KR20070034992A - Optical films and their preparation - Google Patents

Abstract

Optically used films, products having such films, methods of making such films, and systems using such films are disclosed.

Description

OPTICAL FILMS AND METHODS OF MAKING THE SAME

The present invention relates to optical films and related products, systems and methods.

Optical elements and optical systems are commonly used in applications where light modulation is required. Examples of optical elements include lenses, polarizers, optical filters, antireflective films, retarders (such as quarter wave plates), and beam splitters (such as polarized and non-polarized beams) Dividers).

The present invention relates to optically used films, products with such films, methods of making such films, and systems using such films.

According to one aspect, the present invention provides a product comprising a first material layer comprising at least one trench, and sequentially forming a plurality of monolayers of a second material in the trench, thereby forming the trench volume. Filling at least 50% of the first material layer, wherein the first material layer is birefringent for light of wavelength λ propagating through the layer along an axis, wherein λ is between 150 nm and 2,000 nm. .

In another aspect, the invention features a method comprising forming a material layer on a grating surface using atomic layer deposition.

In another aspect, the invention features a method comprising forming an optical retardation film using atomic layer deposition.

In another aspect, the invention features a product comprising a continuous layer comprising rows of first material alternating with rows of nanolaminated material, the continuous layer propagating through the continuous layer along an axis. It is birefringent with respect to the light of the wavelength?, And? Is between 150 nm and 2,000 nm.

In another aspect, the invention features an article comprising a form birefringent optical retardation film comprising a nanolaminate material.

Embodiments of the present invention may include one or more of the following features.

The filling step further includes forming one or more monolayers of the third layer of material in the trench, wherein the second and third materials are different. The monolayer of the second material and the third material may form a nanolaminate material. At least about 80% (eg, at least about 90%, at least about 99%) of the trench volume may be filled by sequentially forming a plurality of monolayers of the second material in the trench. The second material may be different from the first material. The layer of the first material and the second material may form a continuous layer. The continuous layer is birefringent for light of wavelength λ propagating through the continuous layer along the axis, and λ is between 150 nm and 2,000 nm. The article may include additional trenches formed on the surface of the first material layer. The method may further comprise filling at least about 50% of the volume of each of the additional trenches by sequentially forming a plurality of monolayers of a second material in the additional trenches. The method fills at least about 80% (eg, at least about 90%, at least about 99%) of the volume of each of the additional trenches by sequentially forming a plurality of monolayers of a second material in the additional trenches. It may further comprise a step. The trenches may be separated by rows of first material. The first layer of material can form a surface relief grating. The surface relief diffraction grating may have a diffraction grating period of about 500 nm or less (eg, about 400 nm or less, about 300 nm or less, about 200 nm or less, about 100 nm or less).

The trench may be formed by etching a continuous first layer of material (eg, reactive ion etching). The trench may be formed lithographically. For example, the trench may be formed using nano-imprint lithography or holographic lithography. If the trench is formed using nano-imprint lithography, nano-imprint lithography may include forming a pattern in the thermoplastic material. Alternatively, or in addition, nano-imprint lithography may include forming a pattern in the UV curable material.

The method may further comprise forming a second material layer over the filled trench by sequentially forming nanolayers of the second material over the trench. The second material layer includes a surface having an arithmetic mean roughness of about 50 nm or less (eg, about 40 nm or less, about 30 nm or less, about 20 nm or less, about 10 nm or less).

The second material may be a dielectric material. In some embodiments, forming a plurality of monolayers of the second material includes depositing a monolayer of the precursor and exposing the monolayer of the precursor to the reactant to provide a monolayer of the second material. The reactant may chemically react with the precursor to form the second material. For example, the reactant can oxidize the precursor to form a second material. Depositing a monolayer of the precursor may include injecting a first gas containing the precursor into the chamber holding the product. The pressure of the first gas in the chamber during deposition of the precursor monolayer is from about 0.01 to about 100 Torr. Exposing the monolayer of precursor to the reactant may comprise injecting a second gas comprising the reactant into the chamber. The pressure of the second gas in the chamber is about 0.01 to about 100 Torr while the monolayer of precursor is exposed to the reactant. The third gas may be injected into the chamber after the first gas is injected and before the second gas is injected. The third gas may be inert relative to the precursor. The third gas may include at least one gas selected from the group consisting of helium, argon, nitrogen, neon, krypton, and xenon. The precursor is selected from the group consisting of tri (tetra-butoxy) silanol, (CH ₃ ) ₃ Al, TiCl ₄ , SiCl ₄ , SiH ₂ Cl ₂ , TaCl ₃ , AlCl ₃ , Hf-ethanoxide and Ta-ethanoxide Can be.

The trench may have a width of about 1,000 nm or less (eg, about 900 nm or less, about 800 nm or less, about 700 nm or less, about 600 nm or less, about 500 nm or less, about 400 nm or less, about 300 nm or less, about 200 nm or less). The trench may be at least about 10 nm (eg, at least about 20 nm, at least about 30 nm, at least about 40 nm, at least about 50 nm, at least about 75 nm, at least about 100 nm, at least about 150 nm, at least about 200 nm, at least about 300 nm, at least about 400 nm. , About 500 nm or more, about 1,000 nm or more, about 1,500 nm or more, about 2,000 nm or more).

The method may further comprise forming a second birefringent layer on the first material layer after filling the trench. The second birefringent layer may include a plurality of trenches and forming the second birefringent layer includes filling the plurality of trenches by sequentially forming a plurality of monolayers of the third material in the trenches of the second birefringent layer. . The method may include forming additional birefringent layers on the second birefringent layer.

In certain embodiments, the diffraction grating may be a surface relief diffraction grating. The diffraction grating may have a diffraction grating period of about 2,000 nm or less (eg, about 1,5000 nm or less, about 1,000 nm or less, about 750 nm or less, about 500 nm or less, about 300 nm or less, about 200 nm or less).

The optical relaxing film can form birefringence.

The article may further comprise at least one antireflective film, the article surface comprising the surface of the antireflective film. In some embodiments, the article includes a third layer of material adjacent to the continuous layer. The article may comprise a layer of nanolaminate material adjacent to the continuous layer. The layer of nanolaminate material adjacent the continuous layer may comprise a surface having an arithmetic mean roughness of about 50 nm or less (eg, about 40 nm or less, about 30 nm or less, about 20 nm or less, about 10 nm or less). The nanolaminated material has a refractive index of at least about 1.3 (eg, at least about 1.4, at least about 1.5, at least about 1.6, at least about 1.7, at least about 1.8, at least about 1.9, at least about 2.0, at least about 2.1) at λ. Can be. The first material has a refractive index of at least about 1.3 (eg, at least about 1.4, at least about 1.5, at least about 1.6, at least about 1.7, at least about 1.8, at least about 1.9, at least about 2.0, at least about 2.1) at λ. Can be. The nanolaminate material may include portions of the second material and portions of the third material, wherein the second material and the third material are different. In some embodiments, the first material and the third material are the same.

Nanolaminate materials may include dielectric materials, inorganic materials, and / or metals. The nanolaminate material may include a material selected from the group consisting of SiO ₂ , SiN _x , Si, Al ₂ O ₃ , ZrO ₂ , Ta ₂ O ₅ , TiO ₂ , HfO ₂ , Nb ₂ O _5, and MgF ₂ .

The first material may be a dielectric material, inorganic material, glass, polymer, semiconductor, and / or metal. In certain embodiments, the first material is selected from the group consisting of SiO ₂ , SiN _x , Si, Al ₂ O ₃ , ZrO ₂ , Ta ₂ O ₅ , TiO ₂ , HfO ₂ , Nb ₂ O _5, and MgF ₂ . .

The continuous layer may form a diffraction grating with a diffraction grating period of about 500 nm or less (eg, about 200 nm or less, about 100 nm or less, about 50 nm or less). Rows of the first material may have a minimum width of about 500 nm or less (about 200 nm or less, about 100 nm or less, about 50 nm or less, about 20 nm or less, about 10 nm or less). The rows of first material may have a minimum width that is equal to or different from the minimum width of the nanolaminate material rows. The minimum width of each of the rows of first material may be substantially the same. Alternatively or additionally, the width of each of the rows of nanolaminated material is substantially the same.

The continuous layer may be at least about 15 nm (eg, at least about 30 nm, at least about 50 nm, at least about 75 nm, at least about 100 nm, at least about 150 nm, at least about 200 nm, at least about 300 nm, at least about 500 nm, at least about 1,000 nm, about 1,500 nm or more, about 2,000 nm or more). In certain embodiments, the continuous layer is about 1 nm or more (eg, about 2 nm or more, about 5 nm or more, about 10 nm or more, about light at a wavelength λ between 150 nm and 2,000 nm propagating through the continuous layer). 20 nm or more, about 50 nm or more). The continuous layer may have an optical delay of about 2,000 nm or less for light at a wavelength λ between 200 nm and 2,000 nm propagating through the composite layer along the axis. In some embodiments, λ is between about 400 nm and about 700 nm (eg, between about 510 nm and about 570 nm). In some embodiments, the continuous layer has an optical delay of at least about 4 nm for light at wavelength λ between about 400 nm and about 700 nm propagating through the continuous layer along the axis.

The article may comprise a second continuous layer comprising rows of third materials alternating with rows of second nanolaminated material, the second continuous layer having a wavelength λ propagating through the second continuous layer along an axis. ) Is birefringent for light. The article may also comprise additional form birefringence layers, each of which is birefringent for light of wavelength λ propagating through each of the form birefringence layers along an axis.

Embodiments of the invention may include one or more of the following advantages.

In some embodiments, the article may be relatively robust optical retarders, may have high transmission at that wavelength, and have a delay that can be accurately controlled. The optical retardation may include one or more shaped birefringent layers. Morph birefringence is caused by the sub-wavelength of the medium, which is achieved by arranging at least two different materials (eg optically isotropic materials) in an alternating manner. Morph birefringence can be caused in the sub-wavelength diffraction grating structure, the medium having its refractive index changing periodically, the period being substantially less than that wavelength. Since the period is smaller than that wavelength, only substantially zero-order diffraction is achieved and all higher-order diffractions are lost (eg, the beam at that wavelength is substantially transmitted and / or reflected). While the materials that make up the form birefringent medium may be optically isotropic (ie, have a uniform refractive index), the medium itself is optically anisotropic, resulting in birefringence.

In some embodiments, the optical retarders may include one or more shaped birefringent layers formed of continuous materials, as opposed to having trenches filled with, for example, a gas (eg, air). Thus, optical retarders may be mechanically more robust than optical retarders that include discontinuous layers (eg, layers comprising one or more trenches filled with air).

In certain embodiments, continuous shaped birefringent layers may be formed having a relatively high aspect ratio between the width and thickness of portions of the layers. For example, high aspect ratio trenches may be etched into the layer, and the trenches are sequentially filled using a conformal coating scheme (eg, atomic layer deposition) to provide a continuous form birefringence layer having a relatively high aspect ratio. .

The birefringence of the optical retarders can be precisely controlled. To achieve this, the refractive index of one or more portions of the form birefringence layer can be adjusted to a desired value, for example, by controlling the composition of the portion (s), thereby controlling the birefringence. For example, one or more portions of the layer may be formed of nanolaminates. The refractive index of the nanolaminate can be adjusted by selecting portions of two or more materials of the nanolaminate, which can be controlled on a monolayer by the monolayer principle in which the nanolayer is formed using atomic layer deposition.

Alternatively or additionally, precise control of the layer structure can accurately control the birefringence of the form birefringence layer. For example, accurate control of the structure can be achieved by the use of lithography techniques (eg, electron beam lithography, nanoimprint lithography, holographic lithography) that define the structure of the form birefringence layer.

In certain embodiments, the delay of the optical retarders can be precisely controlled. For example, the depth and / or birefringence of the form birefringence layer of the optical retarder can be precisely controlled to provide the desired delay. For example, the optical retarders may include one or more layers to control the thickness of the shape birefringent layer portions in the retarder, such as one or more etch stop layers.

In certain embodiments, the optical retarders have a high transmission at that wavelength. For example, the optical retarders may include one or more antireflective films that reduce light reflection at that wavelength on one or more interfaces. Alternatively or additionally, the layers of optical retarders may be formed of a material having a relatively low absorption at that wavelength.

Other features and advantages of the invention will be apparent from the following more detailed description, drawings, and claims.

1 is a schematic diagram of an embodiment for an optical retarder,

2A-2J show the manufacturing steps of the optical retarder shown in FIG. 1,

3 is a schematic diagram of an atomic layer deposition system,

4 is a flow diagram illustrating the steps of forming nanolayers using atomic layer deposition;

5 is a cross-sectional view of another embodiment of an optical retarder;

6 is a cross-sectional view of one embodiment of an optical retarder including a plurality of retardation layers;

7 is a cross-sectional view of a polarizer incorporating an optical retarder,

8 is a cross-sectional view of a liquid crystal display incorporating an optical retarder;

9A is a scanning electron micrograph of a sub-wavelength diffraction grating prior to filling the trench,

9B is a scanning electron micrograph of the sub-wavelength diffraction grating shown in FIG. 9A after filling the trench.

Like reference symbols in the various drawings indicate like elements.

Referring to FIG. 1, an embodiment of the optical retarder 100 includes a retardation layer 110 and two antireflective films 150, 160. The optical retarder 100 includes a substrate 140, an etch stop layer 130, and a cap layer 120. The retardation layer 110 is in the form of a diffraction grating and includes portions 111 having a first refractive index and portions 112 having a second refractive index. The retardation layer 110 is birefringent for light of wavelength λ propagating along the axis 101, parallel to the z-axis of the coordinate system shown in FIG. 1. Generally, λ is between about 150 nm and about 5,000 nm. In certain embodiments, λ corresponds to a wavelength (eg, about 400 nm to about 700 nm) within the visible portion of the electromagnetic spectrum.

The portions 111, 112 extend along the y-direction to form a periodic structure consisting of a series of alternating rows with different refractive indices. Rows corresponding to portions 111 have a width A ₁₁₁ in the x-direction, while rows corresponding to portions 112 have a width A ₁₁₂ in the x-direction. The width of the rows is smaller than [lambda] so that the retardation layer 110 is form birefringent for light of wavelength [lambda] without significantly higher order diffraction. Optical waves with different polarization states propagate past the retardation layer 110 with the thickness of the retardation layer 110, the refractive indices of the portions ₁₁₁ and _112, and the different phase shifts associated with A ₁₁₁ and A ₁₁₂ . . Thus, these parameters are chosen to provide the desired amount of delay for light polarized at λ.

Retardation layer 110 has a birefringence corresponding to n _e -n ₀ , where n _e and n _o are the effective extraordinary and normal refractive indices for layer 110, respectively. . For the delay layer 110, n _e and n _o are given as follows.

In equation (1), n ₁₁₁ and n ₁₁₂ and A ₁₁₁ and A ₁₁₂ are regarded as refractive indices and thicknesses (along the x-direction) of the portions ₁₁₁ and ₁₁₂ , respectively. In general, the values of n _e and n _o depend on n ₁₁₁ , n ₁₁₂ , A ₁₁₁ and A ₁₁₂ , and n ₁₁₁ and n ₁₁₂ Between. A ₁₁₁ and A ₁₁₂ may be selected to provide the desired values of Δn based on the values for n _e and n _o given by equation (1). In addition, the refractive indices n ₁₁₁ , n ₁₁₂ along the composition of each of the portions 111, 112 can be selected to provide a desired value of Δn. In some embodiments, Δn is relatively large (eg, at least about 0.1, at least about 0.15, at least about 0.2, at least about 0.3, at least about 0.5, at least about 1.0, at least about 1.5, at least about 2.0. Optionally, in yet another embodiment, Δn is relatively small (eg, about 0.05 or less, about 0.04 or less, about 0.03 or less, about 0.02 or less, about 0.01 or less, about 0.005 or less, about 0.002 or less, about 0.001 or less) .

Generally, the refractive indices of the portions 11 are at least about 1.3 (eg, at least about 1.4, at least about 1.5, at least about 1.6, at least about 1.7, at least about 1.8, at least about 1.9, at least about 2.0, at least about 2.1. , About 2.2 or more). Further, in general, the refractive indices of the portions 112 are about 1.3 or more (eg, about 1.4 or more, about 1.5 or more, about 1.6 or more, about 1.7 or more, about 1.8 or more, about 1.9 or more, about 2.0 or more, about 2.1). Above, about 2.2 or more).

In general, A ₁₁₁ may be about 0.2 lambda or less (eg, about 0.1 lambda or less, about 0.05 lambda or less, about 0.04λ or less, about 0.03λ or less, about 0.02λ or less, 0.01λ or less). For example, in some embodiments, A ₁₁₁ is 200 nm or less (eg, about 150 nm or less, about 100 nm or less, about 80 nm or less, about 70 nm or less, about 60 nm or less, about 50 nm or less, about 40 nm or less, about 30 nm or less). )to be. Similarly, A ₁₁₂ can be about 0.2 lambda or less (eg, about 0.1 lambda or less, about 0.05 lambda or less, about 0.04 lambda or less, about 0.03 lambda or less, about 0.02 lambda or less, 0.01 lambda or less). For example, in some embodiments, A ₁₁₂ is 200 nm or less (eg, about 150 nm or less, about 100 nm or less, about 80 nm or less, about 70 nm or less, about 60 nm or less, about 50 nm or less, about 40 nm or less, about 30 nm or less). )to be. A ₁₁₁ and A ₁₁₂ may be the same or different from each other.

Along the x-axis, the refractive index of the retardation layer 110 is periodic with period A, corresponding to A ₁₁₁ + A ₁₁₂ . Generally, A is about 0.5 lambda or less (eg, about 0.3 lambda or less, about 0.2 lambda or less, about 0.1 lambda or less, about 0.08 lambda or less, about 0.05 lambda or less, about 0.04 lambda or less, about 0.03 lambda or less, about 0.02 lambda or less, 0.01 lambda or less). In certain embodiments, A is about 500 nm or less (eg, about 300 nm or less, about 200 nm or less, about 100 nm or less, about 80 nm or less, about 60 nm or less, about 50 nm or less, about 40 nm or less).

Although the delay layer 110 is shown having 19 portions, in general, the number of portions of the delay layer can vary as desired. The number of parts depends on the area and period A required by the end use field of the retarder. In some embodiments, the delay layer 110 may comprise about 50 or more portions (eg, about 100 or more portions, about 500 or more portions, about 1,000 or more portions, about 5,000 or more portions, About 10,000 or more parts, about 50,000 or more parts, about 100,000 or more parts, about 500,000 or more parts).

The thickness d of the retardation layer 110 measured along the z-axis can vary as desired. In general, the thickness of layer 110 is selected based on the desired retardation of retardation layer 110 and the refractive indices of portions 111 at λ. In some embodiments, d is at least about 50 nm (eg, at least about 75 nm, at least about 100 nm, at least about 125 nm, at least about 150 nm, at least about 200 nm, at least about 250 nm, at least about 300 nm, at least about 400 nm, at least about 500 nm). , About 1,000 nm or more, about 2,000 nm).

The aspect ratio of the retardation layer thickness d to A ₁₁₁ and / or d to A ₁₁₂ is relatively high. For example, d: A ₁₁₁ and / or d: A ₁₁₂ may be at least about 2: 1 (eg, at least about 3: 1, at least about 4: 1, at least about 5: 1, at least about 8: 1, About 10: 1 or more).

The delay of the delay layer 110 corresponds to the product of the thickness d of the delay layer 110 and Δn. By selecting appropriate values for Δn and the layer thickness, the delay can be changed as desired. In some embodiments, the delay of the delay layer 110 is at least about 50 nm (eg, at least about 75 nm, at least about 100 nm, at least about 125 nm, at least about 150 nm, at least about 200 nm, at least about 250 nm, at least about 300 nm, about 400 nm or more, about 500 nm or more, about 1,000 nm or more, about 2,000 nm). Optionally, in another embodiment, the delay is about 40 nm or less (eg, about 30 nm or less, about 20 nm or less, about 10 nm or less, about 5 nm or less, about 2 nm or less). In some embodiments, the delay corresponds to λ / 4 or λ / 2.

),The delay is also a phase delay (

),

로 표현될 수 있다.

It can be expressed as.

=π/2에 해당하는 반면, 반파 지연은

=π에 해당한다. 일반적으로, 위상 지연은 원하는 대로 변할 수 있다. 일부 실시예에서, 위상 지연은 약 2π이하(예를 들어, 약 0.8π 이하, 약 0.7π 이하, 약 0.6π 이하, 약 0.5π 이하, 약 0.4π 이하, 약 0.2π 이하, 약 0.1π 이하, 약 0.05π 이하, 약 0.01π 이하)일 수 있다. 선택적으로, 다른 실시예에서 지연층(110)의 위상 지연은 2π 이상(예를 들어, 약 3π 이상, 약 4π 이상, 약 5π 이상)일 수 있다.For example, a quarter wave delay

= π / 2, while the half-wave delay

corresponds to = π. In general, the phase delay can vary as desired. In some embodiments, the phase delay is about 2π or less (eg, about 0.8π or less, about 0.7π or less, about 0.6π or less, about 0.5π or less, about 0.4π or less, about 0.2π or less, about 0.1π or less). , About 0.05π or less, about 0.01π or less). Optionally, in another embodiment, the phase delay of the delay layer 110 may be at least 2π (eg, at least about 3π, at least about 4π, at least about 5π).

In general, the composition of the portions 111, 112 can vary as desired. Portions 111 and / or 112 may comprise inorganic and / or organic materials. Examples of inorganic materials include metals, semiconductors, and inorganic dielectric materials (eg, glass). For example, the organic material includes a polymer.

In some embodiments, portions 111 and / or portions 112 may be dielectric oxide (eg, metal oxides), fluorides (eg, metal fluorides), sulfides, and / or nitrides (eg, One or more dielectric materials). Examples of oxides include _{SiO 2, Al 2 O 3,} Nb 2 O5, TiO 2, ZrO 2, HfO 2, SnO 2, ZnO, ErO 2, Sc 2 O 5. Examples of fluorides include MeF ₂ . Other examples include ZnS, SiN _x , SiO _y N _x , AlN, TiN and HfN.

The composition of the portions 111, 112 is typically used to form their layers and their compatibility with the processes used in the manufacture of the optical retarder 100 and other layers of the optical retarder 100. It is chosen based on the materials and their compatibility. The composition of the portions 111 and / or 112 may be selected to have a certain refractive index at λ. In general, the refractive index of the portion 111 is different from the refractive index of the portion 112 at λ. In some embodiments, portions 111 or 112 are formed of a material having a relatively high refractive index, such as TiO ₂ having a refractive index of about 2.35 at 632 nm or Ta ₂ O ₅ having a refractive index of 2.15 at 632 nm. do. Optionally, portions 111 or portions 112 may be formed of a material having a relatively low refractive index. Examples of low refractive index materials are SiO ₂ and Al ₂ O ₃ with refractive indices of 1.45 and 1.65 at 632 nm, respectively.

In some embodiments, the composition of the portions 111 and / or portions 112 has a relatively low absorption at λ so that the retardation layer 110 has a relatively low absorption at λ. For example, the delay layer 110 may be about 5% or less (e.g., about 3% or less, about 2% or less, about 1% or less, about 0.5% or less, or about λ propagating along the axis 101). Up to about 0.2%, up to about 0.1%).

The portions 111 and / or portions 112 may be formed of a single material or a plurality of different materials. In some embodiments, one or both of portions 111 and portions 112 may be formed of a nanolaminate material, which is considered to be materials that constitute layers of at least two different materials and At least one layer of the material is very thin (eg monolayer thickness of about 1 to 10). Optionally, the nanolaminated material has a locally uniform refractive index depending on the refractive indices of its constituent materials. By varying the amount of each constituent material, the refractive index of the nanolaminated material can be changed. Examples of nanolaminated parts include SiO ₂ monolayers and TiO _2. Monolayers, SiO ₂ monolayers and Ta ₂ O ₅ monolayers, or portions consisting of Al ₂ O ₃ monolayers and TiO ₂ monolayers.

Portions 111 and / or 112 may include crystalline, semicrystalline, and / or amorphous portions. Typically, the amorphous material is optically isotropic and can transmit light better than partially or mostly crystalline portions. For example, in certain embodiments, portions 111 and 112 are formed of an amorphous material, such as an amorphous dielectric material (eg, amorphous TiO ₂ or SiO ₂ ). Optionally, in certain embodiments, portions 111 are formed of a crystalline or semi-crystalline material (eg, crystalline or semi-crystalline Si), while portions 112 are formed of an amorphous material ( For example, an amorphous dielectric material such as TiO ₂ or SiO ₂ ).

Referring to other layers of the optical retarder 100, the substrate 140 generally provides a mechanical support for the optical retarder 100. In certain embodiments, substrate 140 transmits light at wavelength λ, and substantially all light impinging on the substrate at wavelength λ is substantially transmitted (eg, at least about 90%, at least about 95%). , At least about 97%, at least about 99%, at least about 99.5%).

In general, the substrate 140 may be formed of any material that is compatible with the fabrication process used to create the retarder 100, which may support other layers. In certain embodiments, the substrate 140 may comprise Abrisa corporation (BK7), borosilicate glass (eg, Pyrex available from Corning), aluminosilicate glass (eg C1737 available from Corning), or quartz / melt Formed into the same class as silica. In certain embodiments, substrate 140 may be a non-linear optical crystal (e.g., LiNbO ₃ or magneto-optical rotor, such as garnett) or a crystalline (or semi-crystalline) semiconductor (e.g., Si, InP or It may be formed of a crystalline material such as GaAs). In addition, the substrate 140 may be formed of an inorganic material such as a polymer (eg, plastic).

The etch stop layer 130 is formed of a material resistant to the etching process used to etch the material (s) forming the portions 112 (discussed below). The material (s) forming the etch stop layer 130 should be compatible with the materials forming the substrate 140 and the retardation layer 110. Examples of materials capable of forming the etch stop layer 130 include HfO _{2 ,} SiO ₂ , Ta ₂ O ₅ , TiO ₂ , SiN _x Or metals (eg Cr, Ti, Ni).

The thickness of the etch stop layer 130 may vary as desired. Typically, the etch stop layer 130 should be thick enough to prevent excessive etching of the substrate 140, but not so thick as to adversely affect the optical performance of the optical retarder 100. In certain embodiments, the etch stop layer is about 500 nm or less (eg, about 250 nm or less, about 100 nm or less, about 75 nm or less, about 50 nm or less, about 40 nm or less, about 30 nm or less, about 20 nm or less).

Typically, the cap layer 120 is formed of the same material (s) as the portions 111 of the retardation layer 110 and may be deposited on a surface on which additional layers may be deposited, such as the layers forming the antireflective film 150. 121). Surface 121 may be substantially planar.

The antireflective films 150 and 160 reduce the reflectance of light of wavelength λ emitted by colliding on the optical retarder 100. Generally, the antireflective films 150 and 160 comprise one or more layers of different refractive indices. As an example, one or more antireflective films 150 and 160 may be formed of four layers of alternating high and low refractive indices. High refractive index layers may be formed of TiO ₂ or Ta ₂ O ₅ and low refractive index layers may be formed of SiO ₂ or MgF ₂ . The antireflective films may be broadband antireflective films or narrowband antireflective films.

In some embodiments, optical retarder 100 is about 5% or less (eg, about 3% or less, about 2% or less, about 1% or less, about 0.5) to light impinging thereon at wavelength λ % Or less, about 0.2% or less). In addition, the optical retarder 100 may have a high transmittance for light having a wavelength λ. For example, the optical retarder 100 may transmit at least about 95% (eg, at least about 98%, at least about 99%, at least about 99.5%) of light impinging thereon at wavelength λ. .

In general, the optical retarder 100 may be provided as desired. 2A-2J illustrate different steps of the example preparation process. Initially, a substrate 140 is provided as shown in FIG. 2A. The surface 141 of the substrate 140 may be polished and / or cleaned (eg, by one or more solvents, exposure of the substrate to acid, and / or substrate baking).

Referring to FIG. 2B, an edging stop layer 130 is deposited on the surface 141 of the substrate 140. Materials forming the etch stop layer 130 may include sputtering (eg, radio frequency sputtering), evaporation (eg, electron beam evaporation, ion assisted deposition (IAD) electron beam evaporation), or plasma enhanced CVD (PECVD). It may be formed using one of a variety of techniques including chemical vapor deposition by ALD or oxidation. As an example, the HfO ₂ layer may be deposited on the substrate 140 by IAD electron beam evaporation.

Referring to FIG. 2C, an intermediate layer 210 is deposited on the surface 131 of the etch stop layer 130. The portions 112 are etched from the intermediate layer 210 so that the intermediate layer 210 is formed of the material used for the portions 112. Materials forming the interlayer 210 include sputtering (eg, radio frequency sputtering), evaporation (eg, electron beam evaporation), or chemical vapor deposition (CVD) (eg, plasma enhanced CVD). It may be deposited using one of a variety of techniques. For example, the SiO 2 layer may be etched stop layer 130 by sputtering (eg, radio frequency sputtering), CVD (eg, plasma enhanced CVD), or electron beam evaporation (eg, IAD electron beam deposition). May be deposited on. The thickness of the intermediate layer 210 is selected based on the desired thickness of the retardation layer 110.

The intermediate layer 210 is processed to provide portions 112 of the delay layer 110 using lithographic techniques. For example, portions 112 may be formed of intermediate layer 210 using electron beam lithography or photolithography (eg, using photomask or holographic techniques). In some embodiments, portions 112 are formed using nano-imprint lithography. Referring to FIG. 2D, nano-imprint photolithography includes forming a resist layer 220 on the surface 211 of the intermediate layer 210. The resist can be, for example, polymethylmethacrylate (PMMA) or polystyrene (PS). Referring to FIG. 2E, the pattern is impressed into the resist layer 220 using a mold. Patterned resist layer 220 includes thin portions 221 and thick portions 222. The patterned resist layer 220 is then etched (eg, by oxygen reactive ion etching (RIE)) and the portions 224 of the surface 211 of the intermediate layer 210, as shown in FIG. 2F. Thin portions 221 are removed to expose. Thick portions 222 are etched but not completely removed. Thus, resist portions 223 remain on surface 211 after etching.

Referring to FIG. 2G, exposed portions of the intermediate layer 210 are sequentially etched to form trenches 212 in the intermediate layer 210. Unetched portions of the intermediate layer 210 correspond to portions 112 of the delay layer 110. The intermediate layer 210 may be etched using, for example, reactive ion etching, ion beam etching, sputter etching, chemical assisted ion beam etching (CAIBE), or wet etching. The exposed portions of the intermediate layer 210 are etched down with an etch stop layer 130 formed of a material resistant to the etching method. Thus, the depth of trench 212 formed by etching is equal to the thickness of portions 112. After etching trench 212, residual resist 223 is removed from portions 112. The resist can be removed by rinsing the product in a solvent (eg, organic solvent such as acetone or alcohol) by plasma ashing, O ₂ plasma ashing, O ₂ RIE, or ozone cleaning.

Referring to FIG. 2I, after removing the residual resist, material is deposited on the article to fill trench 212 and form cap layer 120. The filled trenches correspond to portions 111 of the delay layer 110. The material may be deposited on the article in a variety of ways, including sputtering, electron beam evaporation, CVD (eg, high density CVD) or atomic layer deposition (ALD). Note that when cap layer 120 is formed and trench 212 is filled during the same deposition step, portions 111 and cap layer 120 are formed of a continuous portion of material.

Finally, antireflective films 150 and 160 are deposited on the surface 121 of the cap layer 120 and the surface 142 of the substrate 140, respectively. The materials forming the antireflective films can be deposited on the article by, for example, sputtering, electron beam evaporation, or ALD.

As mentioned above, in some embodiments, one or both of portions 111, cap layer 120, and / or antireflective films 150, 160 of retardation layer 110 are atomic layer deposition (ALD). It is prepared by using. For example, referring to FIG. 3, the ALD system 300 may include a trench 212 of an intermediate product 301 (comprising a substrate 140, a cap layer 130, and portions 112) in a nanolayered multilayer. Used to fill Deposition of nanolayered multilayers consists of a monolayer by monolayer, providing significant control over the composition and thickness of the films. During deposition of the monolayer, a gaseous precursor is injected into the chamber and adsorbed onto the exposed surfaces of portions 112, the etch stop layer surface 131, or previously deposited monolayers near these surfaces. Subsequently, a reactant that chemically reacts with the adsorbed precursor is injected into the chamber to form a monolayer of the desired material. The self-limiting nature of the chemical reaction on the surface can provide precise control of the film thickness and large area uniformity of the deposited layer. In addition, non-directional precursor adsorption onto each exposed surface provides a uniform deposition of material on the exposed surface, regardless of the surface orientation to the chamber 110. Thus, the layers of the nanolaminated film follow the trench shape of the intermediate product 301.

The ALD system 300 includes a reaction chamber 310 that is connected to sources 350, 360, 370, 380, 390 through a manifold 330. Sources 350, 360, 370, 380, 390 are connected to manifold 330 via supply lines 351, 361, 371, 381, 391, respectively. The valves 352, 362, 372, 382, 392 regulate gas flow to the sources 350, 360, 370, 380, 390, respectively. Sources 350 and 380 include first and second precursors, respectively, while sources 360 and 390 each include a first and second reactant. Source 370 transfers reaction by-products from the substrate while allowing precursors and reactants to flow constantly into chamber 310 towards product 301 during the deposition process. The precursor and reactant are injected into the chamber 310 by mixing with the carrier gas in the manifold 330. Gases are exhausted from the chamber 310 through an exhaust port 345. Pump 340 exhausts gases from chamber 310 through exhaust port 345. Pump 340 is connected to exhaust port 345 through tube 346.

The ALD system 300 includes a temperature controller 395 that controls the temperature of the chamber 310. During deposition, the temperature controller 395 raises the temperature of the article 301 above room temperature. In general, the temperature should be high enough to facilitate rapid reaction between the precursor and the reactant, but not damage the substrate. In some embodiments, the temperature of product 301 is about 500 ° C. or less (eg, about 400 ° C. or less, about 300 ° C. or less, about 200 ° C. or less, about 150 ° C. or less, about 125 ° C. or less, about 100 ° C. or less). May be).

Typically, the temperature should not vary significantly between different parts of the product 301. Large temperature changes can cause changes in the reaction rate between the precursor and the reactant in different portions of the substrate, resulting in changes in the thickness and / or morphology of the deposited layers. In some embodiments, the temperature between different portions of the deposition surface may vary from about 40 ° C. or less (eg, about 30 ° C. or less, about 20 ° C. or less, about 10 ° C. or less, about 5 ° C. or less).

Deposition process parameters are controlled and synchronized by the electronic controller 399. Electronic controller 399 includes temperature controller 395; Pump 340; And valves 352, 362, 372, 382, 392. Electronic controller 399 includes a user interface, which allows an operator to set deposition process parameters, monitor the deposition process, and interact with system 300.

With reference to FIG. 4, an ALD process is initiated 410 as the system 300 mixes a first precursor from source 350 with a carrier gas from source 370 into chamber 310. A monolayer of the first precursor is adsorbed on the exposed surface of the product 301 and the residual precursor is purified 430 from the chamber 310 by the continuous flow of carrier gas through the chamber. Next, the system injects 440 the first reactant from the source 360 into the chamber 310. The first reactant reacts with a monolayer of the first precursor to form a monolayer of the first material. For the first precursor, the flow of carrier gas purifies the residual reactant from chamber 450 (450). Steps 420-460 are repeated 460 until the first layer of material reaches the desired thickness.

In an embodiment where the films are a single material layer, the process stops when the first material layer reaches the desired thickness (470). However, for the nanolaminate film, the system injects 480 a second precursor into chamber 310 through manifold 330. A monolayer of the second precursor is adsorbed onto the exposed surface of the deposited layer of the first material and the carrier gas purifies the chamber of residual precursor (490). The system then injects a second reactant from the source 380 through the manifold 330 into the chamber 310. The second reactant reacts with the monolayer of the second precursor to form a monolayer of the second material (500). The flow of carrier gas through the chamber purifies the residual reactant (510). Steps 480-510 are repeated 520 until the second layer of material reaches the desired thickness.

Additional layers of first and second materials are deposited by repeating steps 520 and 530. Once the desired number of layers have been formed (eg, the trench is filled and / or the cap layer has the desired thickness), the process is terminated 540 and the coated product is removed from the chamber 310.

Although the precursor was injected into the chamber before the reactant for each cycle of the process disclosed above, in other embodiments, the reactant may be injected before the precursor. The order in which the precursors and reactants are injected can be selected depending on the interaction with the exposed surface. For example, if the binding energy between the precursor and the surface is higher than the binding energy between the reactant and the surface, the precursor may be injected before the reactant. Optionally, when the binding energy of the reagent is higher, the reagent may be injected before the precursor.

In general, the thickness of each monolayer depends on a number of factors. For example, the thickness of each monolayer depends on the type of material being deposited. Materials made of large molecules can form thick monolayers compared to materials made of small molecules.

Product temperature can affect monolayer thickness. For example, for certain precursors, higher temperatures may reduce the adsorption of precursors on the surface during the deposition cycle, resulting in thinner monolayers than are formed when the substrate temperature is low.

The form of the precursor and the form of the reactant, and the dose amount of the precursor and the reactant can affect the monolayer thickness. In certain embodiments, monolayers of material may be deposited with particular precursors, but different reactants may be used to form monolayers of different thicknesses for each combination. Similarly, monolayers of material formed from different precursors can result in different monolayer thicknesses for different precursors.

Examples of other factors that may affect monolayer thickness include the duration of purge, the residence time of the precursor on the coated surface, the reactor pressure, the physical structure of the reactor, and the possibility of influence from by-products on the deposited material. An example of the byproducts that can affect the film thickness is when the byproducts are deposited. For example, HCl is a byproduct of depositing TiO ₂ using TiCl ₄ precursor and water as reactants. HCl may etch the deposited TiO ₂ before it is discharged. Etching reduces the thickness of the deposited monolayer so that when certain portions of the substrate are exposed to HCl longer than other portions (eg, substrate portions close to the outlet may be exposed to by-products longer than substrate portions farther from the outlet). May result in a variable monolayer thickness for the substrate.

Typically, the monolayer thickness is between about 0.1 nm and about 5 nm. For example, the thickness of the deposited one or more monolayers can be about 0.2 nm or more (eg, about 0.3 nm or more, about 0.5 nm or more). In some embodiments, the thickness of the deposited one or more monolayers may be about 3 nm or less (eg, about 2 nm, about 1 nm or less, about 0.8 nm or less, about 0.5 nm or less).

The average thickness of the deposited monolayer can be determined by depositing a predetermined number of monolayers on the substrate to provide a material layer. In turn, the thickness of the deposited layer is measured (eg, by an ellipsometer, electron microscope, or some other method). The average thickness of the deposited monolayer can be determined as the measured layer thickness is divided by the number of deposition cycles. The average thickness of the deposited monolayer may correspond to the theoretical monolayer thickness. Theoretical monolayer thickness is considered the specific dimensions of the molecules that make up the monolayer, which can be calculated from the bulk density of the material and the molecular weight of the molecules. For example, the estimate of the monolayer thickness for SiO ₂ is ˜0.37 nm. The thickness is estimated as the cube root of the formula unit of amorphous SiO ₂ with a density of 2.0 grams per cubic centimeter.

In certain embodiments, the average thickness of the deposited monolayer is a fraction of the theoretical monolayer thickness (eg, about 0.2 of theoretical monolayer thickness, about 0.3 of theoretical monolayer thickness, about 0.4 of theoretical monolayer thickness, of theoretical monolayer thickness of About 0.5, about 0.6 of the theoretical fault thickness, about 0.7 of the theoretical fault thickness, about 0.8 of the theoretical fault thickness, and about 0.9 of the theoretical fault thickness. Optionally, the average thickness of the deposited monolayer is about 30 times the theoretical monolayer thickness (eg, about 2 times the theoretical monolayer thickness, about 3 times the theoretical monolayer thickness, about 5 times the theoretical monolayer thickness, and theoretical One or more theoretical fault thicknesses of about 8 times greater than the fault thickness, about 10 times greater than the theoretical fault thickness, and about 20 times greater than the theoretical fault thickness).

During the deposition process, chamber 310 pressure may be maintained or varied at a substantially constant pressure. In general, it is the pressure that controls the flow rate of the carrier gas through the chamber. In general, the pressure should be high enough to saturate the surface with the chemically adsorbed species, and the reactant must react completely with the surface species remaining by the precursor and leave the next periodic reaction sites of the precursor. do. If the chamber pressure is too low (can be caused if the dose of precursor and / or reactant is too low), and / or if the pump speed is too high, the surface cannot be saturated by the precursor and the reaction will not be self limiting. Can be. This can cause non-uniform thickness in the deposited layers. In addition, the chamber pressure should not be high enough to prevent the removal of reaction by-products produced by the reaction of the precursor and the reactant. Residual byproducts may interfere with surface saturation when the next precursor dose is injected into the chamber. In certain embodiments, the chamber pressure is maintained between about 0.01 Torr and about 100 Torr (eg, between about 0.1 Torr and about 20 Torr, between about 0.5 Torr and 10 Torr, about 1 Torr).

In general, the amount of precursor and / or reactant injected during each cycle may be selected depending on the chamber size, exposed substrate surface area, and / or chamber pressure. The amount of precursor and / or reactant injected during each cycle can be determined experimentally.

The amount of precursor and / or reactant injected during each cycle can be controlled by the opening and closing timing of the valves 352, 362, 382, 392. The amount of precursor and reactant injected corresponds to the amount of time that each valve opens each cycle. The valves should open long enough to inject sufficient precursor to provide adequate monolayer coverage of the substrate surface. Similarly, the amount of reagent injected during each cycle should be sufficient to react with substantially all of the precursor deposited on the exposed surface. Injecting more precursor and / or reagent than necessary may increase cycle time and / or waste precursor and / or reagent. In some embodiments, the precursor dose is about 0.1 seconds to about 5 seconds (eg, about 0.2 seconds or more, about 0.3 seconds or more, about 0.4 seconds or more, about 0.5 seconds or more, about 0.6 seconds or more) for each cycle, For more than about 0.8 seconds, about 1 second). Similarly, the reactant dose is about 0.1 seconds to about 5 seconds (eg, about 0.2 seconds or more, about 0.3 seconds or more, about 0.4 seconds or more, about 0.5 seconds or more, about 0.6 seconds or more, about each cycle). More than 0.8 seconds, about 1 second or more).

The time between the precursor and the reactant doses corresponds to the purification. Each purge period should be long enough to remove residual precursors or reagents from the chamber, but if this period is too long it can deposit cycle times without advantage. Different purge periods in each cycle may be the same or may vary. In certain embodiments, the purge period is at least about 0.1 seconds (eg, at least about 0.2 seconds, at least about 0.3 seconds, at least about 0.4 seconds, at least about 0.5 seconds, at least about 0.6 seconds, at least about 0.8 seconds, about 1 second. At least about 1.5 seconds, at least about 2 seconds). Generally, the purge period is about 10 seconds or less (eg, about 8 seconds or less, about 5 seconds or less, about 4 seconds or less, about 3 seconds or less).

The time between successive dose injections of the precursor corresponds to the cycle time. The cycle time may be the same or different than the monolayer deposition cycle of different materials. In addition, the cycle time uses different precursors and / or different reactants, but may be the same or different than the single layer deposition cycle of the same material. In certain embodiments, the cycle time is about 20 seconds or less (eg, about 15 seconds or less, about 12 seconds or less, about 10 seconds or less, about 8 seconds or less, about 7 seconds or less, about 6 seconds or less, about 5 seconds). Up to about 4 seconds, up to about 3 seconds). Reducing the cycle time can reduce the time of the deposition process.

In general, the precursors are compatible with the ALD process and are selected to provide the desired deposition material upon reaction with the reactants. In addition, the precursors and materials must be compatible with the material on which they are deposited (eg, the materials forming the substrate materials or the previously deposited layer). Examples of precursors include chlorides (eg, metal chlorides) such as TiCl ₄ , SiCl ₄ , SiH ₂ Cl ₂ , TaCl ₃ , HfCl ₄ , InCl ₃ and AlCl ₃ . In certain embodiments, organic compounds may be used as precursors (eg, Ti-Etaoxide, Ta-Etaoxide, Nb-Ethaoxide). Another example of an organic compound precursor is (CH ₃ ) Al.

Generally, the reactants are selected to be compatible with the ALD process and are selected based on the chemistry of the precursors and materials. For example, when the material is an oxide, the reactant may be an oxidant. Examples of suitable oxidizing agents include water, hydrogen peroxide, oxygen, ozone, (CH ₃ ) Al, and various alcohols (eg, ethyl alcohol CH ₃ OH). For example, the water Nb- ethanone oxide to obtain the ethanone Ta- oxide, Nb ₂ O ₅ to obtain the AlCl _3, Ta ₂ O ₅ to obtain a TiCl _4, Al ₂ O ₃ to obtain a TiO _2, HfO ₂ in the oxidizing of HfCl _4, ZrCl _4, and a precursor, such as InCl ₃ for obtaining the in ₂ O ₃ to obtain the ZrO ₂ to obtain a suitable reactive agent. In each case, HCl is produced as a byproduct. In some embodiments, (CH ₃ ) ₃ Al may be used to oxidize silanol to provide SiO ₂ .

While certain embodiments have been disclosed, the present invention is not generally so limited. For example, the optical retarder 100 (see FIG. 1) represents a particular configuration of different layers, although other embodiments may include additional layers or fewer layers. For example, in some embodiments the optical retarders need not include one or both of the antireflective films 150, 160. In some embodiments, the optical retarders may include additional antireflective films (eg, between the substrate layer 140 and the etch stop layer 130). Embodiments may include protective layers, such as a hard coat layer (eg, a hard coat polymer), on one or both of the antireflective films 150, 160. In certain embodiments, optical retarders need not include a cap layer. For example, the cap layer formed while filling the trenches between the portions 112 may be removed once the portions 111 are formed. The cap layer can be removed, for example, by chemical mechanical polishing or etching.

Referring to FIG. 5, in some embodiments, optical retarder 600 is formed by partially etching trenches directly into the substrate and sequentially filling the trenches to provide a continuous delay layer 610. The optical retarder 600 also includes a cap layer 620 and a base layer 630 corresponding to the underetching portion of the original substrate layer. An antireflection film 640 is deposited on the surface 621 of the cap layer 602, and a second antireflection film 650 is deposited on the surface 631 of the base layer 630.

In certain embodiments, the optical retarder may be formed of one or more retardation layers. For example, referring to FIG. 6, the optical retarder 800 includes four delay layers 810, 820, 830, 840. The optical retarder 800 also includes a substrate layer 801, an etch stop layer 805, and cap layers 811, 821, 831, 841.

The retardation layers 810, 820, 830, 840 may have the same delay or different delays for the light beam with wavelength λ.

The optical retarder 800 may be prepared using the methods disclosed herein. For example, each retardation layer and its corresponding cap layer may be an etch stop layer 805 (e.g., retardation layer 810) or a previously deposited cap layer (e.g., retardation layers 820, 830, 840). It can be formed by depositing and etching an intermediate layer on the wafer) and then depositing materials to fill the etched trench and form a cap layer.

In some embodiments, additional etch stop layers may be deposited on the cap layer prior to forming a sequential delay layer. Of course, other layers may be included, for example antireflective films.

In general, the thickness of the delay layers 810, 820, 830, 840 along the z-direction, the width of these portions (along the x-direction), and the materials used to form them may vary as desired. In some embodiments, delay layers 810, 820, 830, 840 are the same, while in other embodiments, one or more delay layers may be different (eg, one or more different materials for other delay layers). And have different thicknesses and / or different birefringence).

In addition, the optical retarder 800 generally includes four delay layers, although embodiments may include more than four or less than four delay layers. Optical delays include two delay layers, three delay layers, or five or more delay layers (e.g., about 10 or more delay layers, about 20 or more delay layers, about 30 or more delay layers, about 100 or more delays). Layer, about 1000 or more retardation layers).

The overall phase delay for light of wavelength λ propagating through an optical retarder including one or more retardation layers can be relatively large. For example, the optical retarder is at least about 2π at λ (eg, at least about 3π, at least about 4π, at least about 5π, at least about 8π, at least about 10π, at least about 12π, at least about 15π, at least about 20π, about 30 π or more).

The overall thickness (z-direction) of the optical retarder comprising at least one retardation layer is at least about 200 μm (eg, at least about 500 μm, at least about 800 μm, at least about 1,000 μm, at least about 1,500 μm, about 2,000 Μm or more, about 5,000 μm or more).

In certain embodiments, optical retarders are optical walk-offs that split light that is abnormally incident (e.g., light that does not propagate along the z-direction) into normal and abnormal rays emitted by the retarders along different paths. It can be used as a walk-off decision. These optical walk-off crystals can be recut and extended into wedges. Walk-off crystals can be used in a variety of applications such as telecom isolators, circulators, or interleavers, and / or in consumer applications such as, for example, optical low pass filters.

Although embodiments of optical retarders have been disclosed to include a form birefringent layer having a rectangular diffraction grating profile, other embodiments are possible. For example, in some embodiments, the diffraction grating profile of the shape birefringence layer may be a curve having a sinusoidal shape. In another example, the diffraction grating may have a triangular or serrated profile.

Further, although the diffraction grating period in the form of optical retarders in the birefringent layers has been described as being constant, in certain embodiments the diffraction grating period may vary. In some embodiments, portions of the form birefringence layer may be arranged non-periodically.

The optical retarders disclosed herein may be integrated into photons, including passive optical devices (eg polarizers) and active optical devices (eg liquid crystal displays). The optical retarders may be integrated into the device providing the monolithic device, or arranged separately from other parts of the device.

Referring to FIG. 7, an example of an active optical device integrated into an optical retarder is a polarizer 660. The polarizer 660 includes a polarizer 670 and an optical retarder 680. Polarizer 670 may be a sheet polarizer (eg, iodine-stained polyvinyl alcohol) or US Patent Application No. 10 / 644,643 entitled "Multilayer Structures for Polarization and Beam Control" and " Method and System for Providing Beam for Polarization "PCT Patent Application No. Nano-structured polarizers disclosed in PCT / US03 / 26024, the contents of which are incorporated herein by reference.

The polarizing film 670 linearly polarizes light incident on the polarizer 660 that propagates along the axis 661. Optical polarizer 680 then delays the linearly polarized light, providing polarized light to the desired elliptical emission polarizer 660. The elliptical emission light can be varied as desired by selecting parameters associated with the retardation layer of the optical retarder 680 to provide the desired amount of retardation. For example, the emitted light can be circularly polarized or elliptically polarized.

Referring to FIG. 8, examples of an active optical device incorporating an optical retarder include a substrate (eg, a silicon substrate), a reflective electrode 720, a liquid crystal (eg, a nematic or ferroelectric liquid crystal) layer 730, ( For example, there is a liquid crystal display 700 including a transparent electrode 740 (formed from indium tin oxide), an optical retarder 750, and a polarizing film 760. The optical retarder 750 delays the polarized light transmitted through the polarizer 760. This light is reflected from the electrode 720 and propagates through the liquid crystal layer 730. The reflected light is delayed again by the optical retarder 760 before impinging on the polarizing film 760 in seconds. Depending on the voltage applied to the electrodes 720 and 740, the reflected light is absorbed or transmitted by the polarizing film 760, corresponding to a dark pixel or a bright pixel, respectively. Optionally, the LCD 700 includes a color filter that absorbs certain wavelengths in the visible spectrum providing a colored image. While the LCD 700 is a reflective display, the optical retarders disclosed herein may be used in other types of displays, such as transmissive displays or transflective displays.

The following examples are illustrative and not restrictive.

Examples

Optical retarders are provided as follows. A 0.5 mm thick BK7 wafer (4 inch diameter) from Abrisa Corporation (Santa Paula, Calif.) Is a solution of H ₂ O: H ₂ O ₂ : NH ₄ OH to remove insoluble organic contaminants and H ₂ O: H _{It is} cleaned by removing ionic and heavy metal atomic contaminants using a ₂ O ₂ : HCl solution. The wafer is then rinsed with isopropyl alcohol and deionized water and spin dried.

The sub-wavelength diffraction grating is etched into the BK wafer as follows. The BK7 wafer is spin coated with a thin (˜180 nm) layer of PMMA (15K weight molecular weight purchased from Sigma-Aldrich (St. Louis, MO)) that is baked on a hot plate at about 115 ° C. for about 1 hour. After baking, the resist is imprinted with a diffraction grating mold having a period of 200 nm and a depth of about 110 nm, and a diffraction grating linewidth of about 100 nm. The mold includes a SiO ₂ layer (about 200 nm thick) patterned on a 0.5 mm thick silicon substrate. The mold is prepared using the methods disclosed in J. Vac. Sci. Technol., B17, 2957 (1999) (J. Wang, Z. Yu and SY Chou). After imprinting, the modified UV curable resist is fully cured by exposure to UV light through the BK7 substrate side. The mold is then separated from the resist, leaving a mask with the negative pattern of the mold profile. The mask is etched by O ₂ RIE until the BK7 wafer is exposed to the recessed portion of the mask. This etching is performed using plasma-therm 790 (available from Unaxis Inc. (St. Petersburg, FL)). The pressure during etching is 4 mtorr. The power is set at 70 W and the oxygen flow rate during etching is 10 sccm. The total thickness of the resist etched to expose the BK7 wafer is about 120 nm.

After etching the mask, about 50 nm of Cr is deposited on the remaining resist / exposed BK7 wafer by e-beam evaporation at high vacuum (ie, about 5 × 10 ⁻⁶ torr) at an oblique angle from the wafer normal. The oblique angle is about 65 degrees. Cr is deposited on top and sidewalls of the remaining mask lines to provide a hard mask for the etching of BK7. After Cr deposition, the O ₂ RIE is again used to etch any exposed resist that is not covered by Cr. The CHF ₃ RIE is used again to etch exposed portions of the BK7 wafer surface to form a subwavelength diffraction grating of the wafer. BK7 is etched using plasma-therm 720. The chamber pressure is about 5 mTorr, the power is about 100 W, and 10 sccm and 1 sccm of CHF ₃ and O ₂ are used, respectively. A 100 nm wide trench having a depth of about 630 nm is etched into the BK7 wafer. After BK7 etching, Cr is removed by immersing the wafer in a CR-7 Cr etchant (obtained from Cyantek (Fremont, CA)) for about 30 minutes. The remaining resist is removed sequentially by O ₂ RIE.

Trench TiO ₂ And nanolaminated material consisting of SiO ₂ . The nanolaminate material is deposited by ALD performed using a P-400A ALD device from Planar Systems, Inc. (Beaverton, OR). Prior to depositing the nanolayers, the etched substrate is heated to 300 ° C. in an ALD chamber for about 3 hours. The chamber is flushed with nitrogen gas and flows to about 2 SLM to maintain the chamber pressure at about 0.75 Torr. TiO ₂ precursors are Ti-ethanoxide heated to about 140 ° C. SiO ₂ precursor is silanol heated to about 110 ° C. For both precursors, the reactant used is water maintained at about 13 ° C. Ti-ethanoxide and silanol have a purity of 99.999% grade, which is obtained from Sigma-Aldrich (St. Louis, MO). Nanolayers are formed by depositing ten monolayers of TiO ₂ , followed by a cycle of depositing a single monolayer of SiO ₂ . To deposit the TiO ₂ monolayer, water is injected into the chamber for 2 seconds followed by nitrogen purge for 2 seconds. Ti-ethanoxide is then injected into the chamber followed by nitrogen purge for an additional 2 seconds. SiO ₂ monolayers are deposited by injecting water into the ALD chamber for 1 second followed by nitrogen purge for 2 seconds. Silanaol is injected for 1 second. The next chamber is purged with nitrogen for 3 seconds before the next reactant pulse. The refractive index of the nanocrystals is estimated to be about 1.88 at 632 nm as determined from the measurements of the nanolaminated film, similar to that provided on flat glass substrates.

분광타원해석기(J.A.Woollam Co., Inc.(Lincoln, NE)로부터 상업적으로 입수가능함)를 이용하여 측정된다.The delay of the optical retarder is M-2000V, which is 23.85nm at 551nm wavelength

It is measured using a spectroscopic ellipsometer (commercially available from JAWoollam Co., Inc. (Lincoln, NE)).

Unfilled and filled diffraction gratings are examined using scanning electron microscopy performed using a LEO heat-emitting scanning electron microscope. To perform this investigation, the sample is cleaved and coated with a thin layer of Au. The cross section of the split interface is then observed. 9A and 9B show SEM micrographs before and after filling the trenches.

Other embodiments are provided within the scope of the following claims.

Claims (40)

Providing a product comprising a first layer of material, wherein the first layer of material comprises at least one trench and the layer is birefringent for a wavelength [lambda] propagating through the layer along an axis, where [lambda] is from 150 nm to Between 2,000 nm-; And Filling at least about 50% of the trench volume by sequentially forming a plurality of monolayers of a second material in the trench Including, the method. The method of claim 1, The filling step further includes forming one or more monolayers of a third material in the trench, wherein the second material and the third material are different. The method of claim 2, Wherein said monolayers of said second and third materials form a nanolaminate material. The method of claim 1, At least about 80% of the trench volume is filled by sequentially forming a plurality of monolayers of a second material in the trench. The method of claim 1, At least about 90% of the trench volume is filled by sequentially forming a plurality of monolayers of a second material in the trench. The method of claim 1, At least about 99% of the trench volume is filled by sequentially forming a plurality of monolayers of a second material in the trench. The method of claim 1, And the second material is different from the first material. The method of claim 1, And the layer of the first material and the second material form a continuous layer. The method of claim 1, And the article comprises additional trenches formed in the surface of the first material layer. The method of claim 9, And the method further comprises filling at least about 50% of the volume of each of the additional trenches by sequentially forming a plurality of monolayers of the second material in the additional trenches. The method of claim 9, And the method further comprises filling at least about 80% of the volume of each of the additional trenches by sequentially forming a plurality of monolayers of the second material in the additional trenches. The method of claim 9, And the method further comprises filling at least about 90% of the volume of each of the additional trenches by sequentially forming a plurality of monolayers of the second material in the additional trenches. The method of claim 9, And the method further comprises filling at least about 99% of the volume of each of the additional trenches by sequentially forming a plurality of monolayers of the second material in the additional trenches. The method of claim 9, The trenches are separated by rows of the first material. The method of claim 7, wherein And said first layer of material forms a surface relief grating. The method of claim 15, Wherein said surface relief diffraction grating has a diffraction grating period of about 500 nm or less. The method of claim 7, wherein The trench is formed by etching the continuous first layer of material. The method of claim 17, Wherein said etching comprises reactive ion etching. The method of claim 1, And the trench is formed lithographically. The method of claim 19, The trench is formed using nano-imprint lithography. The method of claim 20, The nano-imprint lithography includes forming a pattern in the thermoplastic material. The method of claim 20, The nano-imprint lithography includes forming a pattern in the UV curable material. The method of claim 19, And said trench is formed using holographic lithography. The method of claim 1, Forming a second material layer over the filled trench by sequentially forming monolayers of the second material over the trenches. The method of claim 24, And the second material layer comprises a surface having an arithmetic mean roughness of about 50 nm or less. The method of claim 1, And said second material is a dielectric material. The method of claim 1, Forming a plurality of monolayers of the second material comprises depositing a monolayer of precursor and exposing the monolayer of precursor to a reactant to provide a monolayer of the second material. . The method of claim 27, And the reactant chemically reacts with the precursor to form the second material. The method of claim 28, And the reactant is oxidized with the precursor to form the second material. The method of claim 27, Depositing a monolayer of the precursor comprises injecting a first gas comprising the precursor into a chamber containing the article. The method of claim 30, Wherein the pressure of the first gas in the chamber is from about 0.01 to about 100 Torr while the monolayer of precursor is deposited. The method of claim 30, Exposing the monolayer of precursor to a reactant comprises injecting a second gas comprising the reactant into the chamber. The method of claim 30, Wherein the pressure of the second gas in the chamber is from about 0.01 to about 100 Torr while the monolayer of precursor is exposed to the reactant. The method of claim 30, A third gas is injected into the chamber after the first gas is injected and before the second gas is injected. The method of claim 27, And said third gas is inert relative to said precursor. The method of claim 27, Wherein said third gas comprises at least one gas selected from the group consisting of helium, argon, nitrogen, neon, krypton and xenon. The method of claim 27, The precursor is in the group consisting of tri (tetra-botoxy) silanol, (CH ₃ ) ₃ Al, TiCl ₄ , SiCl ₄ , SiH ₂ Cl ₂ , TaCl ₃ , AlCl ₃ , Hf-ethanoxide and Ta-ethanoxide Selected method. The method of claim 1, The trench has a width of about 1,000 nm or less. The method of claim 1, Wherein said trench has a depth of at least about 10 nm. The method of claim 8, Wherein the continuous layer is birefringent for light of wavelength λ propagating through the continuous layer along the axis, wherein λ is between 150 nm and 2,000 nm.

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