KR20050072877A - 2-step etching process of sio2 among nano imprint lithography - Google Patents

Abstract

TECHNICAL FIELD The present invention relates to nanoimprint lithography, and more particularly, to a process of forming a nanoscale pattern by using a SiO ₂ etching process in nanoimprint lithography as a _two -step etching process.

The two-step silicon oxide etching process of nanoimprint lithography according to the present invention, in the nanoimprint lithography manufacturing process, SiO ₂ with CF ₄ etching gas By etching 1-step etching step to obtain a fine pattern in which the side wall profile is vertical, and SiO ₂ with CHF ₃ etching gas And a two-step etching step capable of etching by etching.

Description

2-Step Etching Process of SiO2 Among Nano Imprint Lithography

TECHNICAL FIELD The present invention relates to nanoimprint lithography, and more particularly, to a process of forming a nanoscale pattern by using a SiO ₂ etching process in nanoimprint lithography as a _two -step etching process.

In general, one of the most widely used microstructure fabrication techniques to date is photolithography, which uses a project-printing system to repeatedly reduce predesigned circuitry to pattern patterns on a substrate coated with a photoresist thin film. To form.

Here, the size of the pattern to be formed is limited by the optical diffraction phenomenon, the resolution is proportional to the wavelength of the light used. That is, the smaller the wavelength of the light beam, the higher resolution the pattern can be formed.

Therefore, in recent years, the development of an optical transfer method using a short wavelength light source such as EUV (Extreme Ultra Violet) or Soft X-ray to form a high resolution pattern has been actively studied worldwide.

The performance of a line grating is mainly determined by the distance between the line and the center of the line, that is, the period and wavelength of the incident wave. When the grating period is longer than the wavelength of the incident wave, the grating acts as a diffraction grating and diffraction irrespective of polarization to form a diffraction interference pattern due to a theoretically well known phase difference.

On the other hand, when the lattice period becomes shorter than the wavelength, the lattice acts as a polarizer, reflecting electromagnetic waves polarized parallel to the lattice (P waves) and passing vertically polarized ones (S waves).

The lattice period becomes an important factor when the long wavelength light source is to be used as a polarizer. Line lattice polarizers are mainly used in the far-infrared region because the lattice period must be shortened in order to polarize short wavelength light.

That is, in order to use the RGB three primary colors including blue with high ER (Extinction Ratio) characteristics and use them as polarizers, a line grating having a period of about 0.1 μm or less is required. However, the current semiconductor process has a line width of about 0.1 占 퐉, and when the lines and lines are periodically drawn, the space between the lines and the carrier is also about 0.1 占 퐉, so that the lattice period is 0.2 占 퐉.

Therefore, in order to obtain a line grating having a period of 0.1 μm or less as described above, an interference effect is used by using an argon laser having a short wavelength, or to form a finer pattern, DUV (Deep Ultraviolet) or EUV (Extreme) having a shorter wavelength is used. Steppers that use ultraviolet wavelengths or lasers with shorter wavelengths should be used.

As described above, the manufacture of fine patterns using lithography using an electron beam or an interferometer using an atomic beam, etc., has been studied, but there is a limitation in size, and complicated and expensive equipment is required, and thus, commercial access is difficult.

In order to overcome this problem and realize a low-cost manufacturing process, Princeton University uses laser interference lithography and side-wall patterning techniques to fabricate 100 nm periodic grating molds for nanoimprint lithography. I have reported production.

Nano imprint lithography includes Soft Imprint Lithography, Thermal Imprint Lithography, and UV Imprint Lithography. Nanoimprint lithography can be applied to various fields such as nano-electronics, plastic electronics, and molecular electronics.

Here, thermal imprint lithography has an advantage of being easy and inexpensive to produce compared to quartz templates used for ultraviolet imprint lithography.

However, since thermal imprint lithography uses a nickel (Si) or silicon (Si) mold, the polymer residues remain on the mold surface during the de-molding process and heat during the imprinting process. There is a problem that deformation of the mold occurs easily.

In general, the process gas used for SiO ₂ etching is mixed with various gases such as CF ₄ , C ₂ F ₆ , C ₃ F ₈ , CHF ₃ and O ₂ gas in an appropriate mixing ratio. The reason why the O ₂ gas is used together is that SiO ₂ is etched to form a fluorine-based organic material including F. The organic material and the O ₂ plasma react to remove the residue after etching. The mixing ratio depends on which equipment is used, and these devices include high density plasma etcher equipment such as RIE, TCP, and ICP.

The equipment is selected according to the etching rate, the pattern scale, or the etching depth. The etching rate is faster as the C / F atom ratio decreases, i.e., as the F atom increases compared to the C atom. In addition, in case of CF ₄ , SiO ₂ is an isotropic etching, and when CHF _{3 is} used, anisotropic etching is performed, thereby obtaining a vertical profile of the side surface.

FIG. 1A shows the side wall profile when using CHF ₃ at the micro pattern scale of lithography, and FIGS. 1B and 1C show the side wall when using CF ₄ at the micro pattern scale of lithography. profile).

The etch profile shown in FIG. 1 shows the lateral profile assuming that the etching time in the ICP-Etcher is the same.

As shown in FIGS. 1A-1C, when CF ₄ gas is used, SiO ₂ is isotropically etched so that the side is inclined to a ladder shape (FIG. 1B), or the edge where the etched side and the wafer meet each other. It is more etched than the side, resulting in a round jar-shaped side profile (FIG. 1C). For this reason, when using CF ₄ gas, RF power is applied to the substrate vias so that the desired vertical profile as shown in FIG. 1A can be obtained after etching.

However, when the pattern scale is reduced from the micro (mm) size to the nanomicro (1 nm or less) size, the pattern shape according to the gas used is completely different. In particular, in the case of forming a fine pattern having a 100 nm period, there is a problem in that it is impossible to form a PR (Photoresist) pattern having a vertical side by a laser interference photo process.

It is an object of the present invention to provide a _two -step SiO ₂ etch process for achieving SiO ₂ etching stop while at the same time obtaining a lateral vertical profile in a nano scale pattern.

In order to achieve the above object, the two-step silicon oxide etching process of nanoimprint lithography according to the present invention, in the nanoimprint lithography manufacturing process, SiO ₂ with CF ₄ etching gas By etching 1-step etching step to obtain a fine pattern in which the side wall profile is vertical, and SiO ₂ with CHF ₃ etching gas And a two-step etching step capable of etching by etching.

Hereinafter, the nanoimprint manufacturing process according to the present invention will be described in detail with reference to FIG.

As shown, silicon oxide (SiO _2, 220) is deposited on the Si wafer 210, and chromium 230 is deposited on the SiO ₂ 220. After depositing PR (Photoresist, 240) on the chromium 230 is patterned (A) by using laser interference or E-Beam and the like (A).

After removing the residue of the PR 240 patterning, the chromium 230 is etched with a mixed gas of chlorine (Cl ₂ ) and oxygen (O ₂ ) (B).

After etching the chromium 230, a two-step etch with a CH ₄ gas and a CHF ₃ gas is etched to the SiO ₂ 220 in the same line width as the PR 240 (C).

The chromium 230 is removed with a chromium etchant, and the pattern sample etched to SiO _{2 is} cleaned with an appropriate surface treatment agent to form a grid pattern 250 (D). Here, the period of the SiO ₂ lattice is about 200 nm and the line width is about 50 nm. In addition, when SiO ₂ remains at the bottom, after etching silicon nitride (Si ₃ N ₄ ), all of the Si ₃ N ₄ falls off when the wet etching of SiO ₂ occurs. Therefore, when etching SiO ₂ , it should not be left under the bottom. Subsequently, Si ₃ N ₄ 260 is deposited on the SiO ₂ 250 film on which the lattice pattern is formed (D).

Here, when the Si ₃ N ₄ (260) is deposited, the rate of etching in HF or buffered HF varies according to the growth temperature, and when grown at 800 ° C., about 100 nm / min at high concentration of HF (49% HF) is shown. Etching and growth at 1100 ℃ shows a slow etching rate of 14nm / min. When the Si ₃ N ₄ is deposited at 300 ° C., BOE (Buffered Oxide Etch) solution treatment shows a very slow etching rate of 10 nm / min.

SiO ₂ (250) after step D The Si ₃ N ₄ (260) is etched until the upper portion of the lattice film appears (E).

After the etching of the Si ₃ N ₄ 260 is completed, by performing wet etching (BOE solution treatment) to remove the SiO ₂ (250), a lattice of Si ₃ N _{4 having} a 50 nm line width of 100 nm period is formed (F).

By using the Si ₃ N ₄ (260) lattice formed as described above as a mask to etch the Si (210) to produce a final Si template 270 of 100nm period (G). Of course, after etching, it is enough to remove the Si ₃ N ₄ used as a mask using a high concentration of HF or phosphoric acid (H).

The pattern forming process of the conventional nanoimprint lithography as described above and the process that is different from the pattern formation process of the nanoimprint lithography according to the present invention will be described in more detail as follows.

In order to perform the SiO ₂ etching process in the step A, it is preferable to use chromium as a mask.

In this case, when PR is used as a mask, the SiO ₂ etching rate is so fast that PR is also etched to form a desired pattern. In addition, the formation of a PR fine pattern with a 100 nm cycle is almost impossible to make the side wall profile vertical by any photo process. In general, the side profile of the PR can be up to 85 degrees irrespective of the PR thickness, so this PR pattern is used as a mask to create a nearly vertical chrome pattern with a 100 nm period.

Using a chromium pattern with a 100 nm cycle as a mask, the side profile of the SiO ₂ being etched is formed exactly as the lateral profile of chromium, thus creating a vertical SiO ₂ fine pattern with a desired 100 nm cycle.

In addition, after the B step, CF ₄ and CHF ₃ gas is sequentially supplied to the etching gas to perform a _two -step SiO ₂ etching process, which will be described below with reference to FIGS. 3 to 4.

First, a, CF ₄ gas for etching SiO ₂ (310) by using manreul, the etching rate is relatively fast width (width) is reduced, increase in the etching depth (etching depth), as shown in Figure 3a. In addition, CF ₄ gas is SiO ₂ 310 In addition, since the Si 320 may also be etched, it is difficult to control the etching depth of the SiO ₂ 310, and thus, the Si 320 may be etched up to the Si 320. In addition, as shown in FIG. 3B, when only the CHF ₃ gas is etched from SiO ₂ 310, a fine pattern in which the side profile is vertical may not be obtained, and a trapezoidal side profile may be obtained.

FIG. 4 illustrates a two-step SiO ₂ etching process using CF ₄ and CHF ₃ gas as an etching gas in nanoimprint lithography according to the present invention.

First, by a one-step etching step of etching SiO ₂ 310 using CF ₄ gas, the etching rate of SiO ₂ 310 is relatively faster than when CHF ₃ gas is used, so the width is Decrease, and the etching depth increases. Therefore, when CF ₄ gas is used, a fine pattern in which the side profile is vertical can be obtained. Here, one-step etching is performed using CF ₄ gas to form a fine pattern in which the side profile is vertical, but the etching is performed so that the Si (320) layer is not etched.

Subsequently, etching the SiO ₂ 310 with CHF ₃ gas does not allow the side profile to be vertical but allows an etching stop that can only etch the SiO ₂ 310 layer.

In addition, for etching stop of SiO ₂ in the two-step step, it is preferable to use only CHF ₃ gas without using O ₂ gas at low pressure.

In general, if the etching of SiO ₂ SiO ₂ as the etching there is organic matter in the F-based form, the O ₂ gas is used together in order to remove it. However, when the SiO ₂ etch depth is about 200 nm, it is so thin that fluorine-based organic matter is hardly formed, and even though such residue is formed, several nm of organic material acts as a mask so that Si is not etched at the etched site. It does not require the use of O ₂ gas because it helps to enable etching stop of SiO ₂ .

Also, CHF₃Using only gas SiO₂It is preferable to etch at low pressure when etching. 4A shows that the fluorine-based organic material does not accumulate at the etched portion when the pressure is low, and FIG. 4B shows that the fluorine-based organic material is accumulated at the etched portion when the pressure is high.

In addition, the 2 step SiO ₂ etching process can be applied to the production of quartz mold (mold, or template) of 100 nm cycle.

Generally, SiO ₂ is amorphous, whereas quartz is single crystal SiO ₂ . Therefore, quartz has a higher density than amorphous SiO ₂ and has an advantage of much better hardness. However, the etching phenomenon SiO ₂ etching and is capable of substantially equal because applying the chromium to as a mask using sequentially a gas of CF ₄ and CHF ₃ 2 step SiO ₂ etching process as except the difference of the etching rate (etching rate) Do.

That is, the two-step SiO ₂ etching process can be applied not only to hot embossing imprint lithography, but also to ultraviolet imprint lithography that requires a transparent mold as well as hot imboss lithography.

According to the present invention, in the nanoscale pattern, it is possible to achieve SiO ₂ etching stop while obtaining the lateral vertical profile.

In addition, the two-step SiO ₂ etching process according to the present invention is also applicable to the manufacture of a transparent quartz template used in the ultraviolet imprint lithography process.

1A shows the side profile when using CHF ₃ gas at the micro pattern scale of lithography.

FIG. 1B shows the side profile when using CF ₄ gas at the micro pattern scale of lithography.

1C shows the side profile when using CF ₄ gas at the micro pattern scale of lithography.

Figure 2 is shown for explaining the nanoimprint manufacturing process according to the present invention.

FIG. 3A illustrates an SiO ₂ etching process using only CF ₄ gas as an etching gas in nanoimprint lithography according to the present invention.

FIG. 3B illustrates an SiO ₂ etching process using only CHF ₃ gas as an etching gas in nanoimprint lithography according to the present invention.

4 illustrates a two-step SiO ₂ etching process using CF ₄ and CHF ₃ gas as an etching gas in nanoimprint lithography according to the present invention.

Figure 5a is shown to show that the fluorine-based organic matter does not accumulate in the etched site when the CHF ₃ gas as the etching gas in the two-step in the nanoimprint lithography according to the present invention to lower the gas pressure.

Figure 5b is shown to show that the fluorine-based organic matter is accumulated in the etched portion when the CHF ₃ gas as an etching gas and the gas pressure is increased in 2-step in the nanoimprint lithography according to the present invention.

<Description of the symbols for the main parts of the drawings>

210; Si 220; Silicon oxide

230; Chromium 240; Photoresit

250; Silicon oxide lattice 260; Silicon nitride

Claims (3)

In the nanoimprint lithography manufacturing process, SiO ₂ with CF ₄ etching gas By etching A one-step etching step of obtaining a fine pattern in which a side wall profile is vertical, and SiO ₂ with CHF ₃ etching gas A two-step etch process of nanoimprint lithography, comprising: a two-step etch step capable of etching to etch stop. The method of claim 1, SiO ₂ The etching step is a two-step silicon oxide etching process of nanoimprint lithography, wherein chromium is used as a mask. The method of claim 1, The two-step silicon oxide etching process of nanoimprint lithography using only CHF ₃ gas at low pressure for etching control of SiO ₂ in the two-step etching step.