WO2020010522A1

WO2020010522A1 - Preparation method for independent metal film and metal film

Info

Publication number: WO2020010522A1
Application number: PCT/CN2018/095163
Authority: WO
Inventors: 龚国华; 何江
Original assignee: 深圳通感微电子有限公司
Priority date: 2018-07-10
Filing date: 2018-07-10
Publication date: 2020-01-16

Abstract

A preparation method for an independent metal film and a metal film, the method comprising: S1. spin coating of a transfer coating: selecting a substrate of which the surface conforms to optical level flatness, washing and drying the substrate, and spin coating a transfer coating on the surface of the substrate; S2. solidification: evaporating and cooling the substrate after spin coating the transfer coating so as to solidify the transfer coating; S3. settling: selecting a metal material, and allowing same to settle on the surface of the solidified transfer coating so as to generate a metal film of a preset thickness; S4. peeling: putting the substrate which has the metal film into an organic solvent capable of dissolving the transfer coating at normal temperature so as to separate the metal film; and S5. transferring: keeping the metal film in an unfolded state, transferring the metal film to an anaerobic condition and drying same so as to obtain a final independent metal film. The present technical solution may be used to prepare an independent metal film that meets requirements; the method is simple and easy to carry out, and the cost is low.

Description

Method for preparing independent metal film and metal film

Technical field

The invention relates to the technical field of metal thin film preparation, and more particularly, to a method for preparing an independent metal thin film and a metal thin film.

Background technique

In scientific research and practical semiconductor processes, suspended films with thicknesses of tens to hundreds of nanometers are often used. Such films are too thin to be peeled off, so it is difficult to prepare them by conventional methods.

technical problem

The technical problem to be solved by the present invention is to provide a method for preparing an independent metal thin film and a metal thin film in response to the foregoing technical defects of the prior art.

Technical solutions

The technical solution adopted by the present invention to solve its technical problems is to construct a method for preparing an independent metal thin film, including the following steps:

S1. Spin-coating a transfer coating: selecting a substrate whose surface satisfies optical level flatness, cleaning and drying the substrate, and spin-coating the transfer coating on the surface of the substrate;

S2: curing: evaporating and cooling the substrate after the transfer coating is spin-coated to cure the transfer coating;

S3. Deposition: a metal material is selected and deposited on the surface of the cured transfer coating to generate a metal film of a preset thickness; the deposition includes:

Filling argon under vacuum and depositing the metal thin film on the surface of the transfer coating by a sputtering power source; or

Heating and vaporizing the metal material by an electron beam power source under a vacuum condition to deposit and generate the metal thin film on the surface of the transfer coating;

S4. Peeling: placing the substrate with the metal thin film in an organic solvent capable of dissolving the transfer coating at normal temperature to separate the metal thin film;

S5. Transfer: Keep the metal thin film in an unfolded state and transfer the metal thin film to dry under oxygen-free conditions to obtain a final independent metal thin film.

Preferably, in the step S1, in the process of spin-coating the transfer coating on the surface of the substrate, the thickness of the transfer coating is 0.5-2 times the preset thickness of the metal thin film.

Preferably, in the step S3, during the process of depositing on the surface of the solidified transfer coating to form a metal film with a preset thickness, the substrate temperature does not exceed 80 ° C.

Preferably, in the step S3, the filling argon under vacuum includes filling argon to a pressure of 0.4-4Pa.

Preferably, in the step S3, the preset thickness of the metal thin film is 50-1000 nm.

Preferably, in the step S1, the surface flatness of the substrate is ± 10 nm.

Preferably, in the step S3, the metal material is one or more of Au, Ag, Cu, Cr, Al, Ni, and Ti.

Preferably, in the step S5, the transferring process includes using a mesh structure or a hollow ring frame tool to lift the metal thin film to keep the metal thin film in an unfolded state.

Preferably, after the step S2, the following steps are further performed:

S2-1. Preset pattern: A preset pattern is set on the surface of the solidified transfer coating.

The invention also constructs a metal thin film, which is obtained by any of the independent metal thin film preparation methods described above.

Beneficial effect

The method for preparing the independent metal thin film and the metal thin film of the present invention have the following beneficial effects: the preparation of the independent metal thin film that meets the requirements can be obtained, the method is simple and easy, and the cost is low.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further described below with reference to the accompanying drawings and embodiments. In the drawings:

1 is a schematic flowchart of a first embodiment of a method for preparing an independent metal thin film according to the present invention;

2 is a schematic process diagram of a first embodiment of a method for preparing an independent metal thin film according to the present invention;

3 is a schematic flowchart of a second embodiment of a method for preparing an independent metal thin film according to the present invention;

FIG. 4 is a schematic process diagram of a second embodiment of a method for preparing an independent metal thin film according to the present invention.

Embodiments of the invention

In order to have a clearer understanding of the technical features, objects, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the drawings.

As shown in FIG. 1 and FIG. 2, in a first embodiment of a method for preparing an independent metal thin film according to the present invention, the following steps are included: S1. Spin-coating a transfer coating: selecting a substrate whose surface satisfies optical level flatness, and The substrate is cleaned and dried, and a transfer coating is spin-coated on the surface of the substrate. Specifically, the substrate is cleaned and dried with an optical level flatness that meets the requirements to ensure the surface is clean and dry. The substrate here can be silicon or silicon. Glass and similar materials. On the cleaned substrate surface, a conventional photoresist spin coater is used to spin-coat a transfer coating with a thickness of 100 to 1000 nm. The transfer coating here can be PMMA or photoresist. In the examples here, PMMA is used. The properties of PMMA after curing are relatively stable. Compared with silicone oil, molten metals, or liquid crystal materials, PMMA is easier to obtain, lower in cost, and does not volatilize during the deposition of metal thin films. Will affect or pollute the vacuum environment. In the spin coating process, the thickness of PMMA can be controlled by the speed of the spin coater and the viscosity of PMMA. The viscosity of PMMA can be controlled by the ratio of PMMA to the solvent. The solvent here can be phenol or anisole.

S2. Curing: Evaporate and cool the substrate after spin-coating the transfer coating to cure the transfer coating. Specifically, the substrate with spin-coated PMMA is placed on a drying oven and evaporated to remove the solvent, and then cooled and solidified. PMMA makes the transfer coating on the substrate a hard structure.

S3. Deposition: Select a metal material to deposit on the surface of the solidified transfer coating to generate a metal film of a predetermined thickness. Deposition includes: filling argon under vacuum and depositing metal on the surface of the transfer coating by a sputtering power source. Thin film; or metal materials are heated and vaporized by an electron beam power source under vacuum to deposit a metal thin film on the surface of the transfer coating; specifically, the spin-coated PMMA substrate is placed in a vacuum chamber, where The atmospheric pressure satisfied by the vacuum chamber is 10 ^-4 Pa or less. Deposition is performed on the surface of the transfer coating under vacuum conditions to generate a metal film of a predetermined thickness. In addition, during the metal film deposition process, the thickness of the film can be monitored using crystal oscillator technology. The specific operation of metal thin film deposition can be as follows: select the required metal material target (Au, Ag, Pt, Cr, Ti, Al, etc.) and install it on the target base, put the PMMA substrate spin-coated, and place The atmospheric pressure of the vacuum chamber is maintained below 10 ^-4 Pa, and no impurity gas is guaranteed during the film deposition process. Filled with high-purity argon, the pressure inside the cavity can be maintained between 0.4-4Pa, and the pressure can be kept stable. Turn on the sputtering power, the sputtering current is maintained at 0.1-0.5A, the sputtering voltage is 220-550V, and the argon plasma is excited. Argon + in the plasma bombards the surface of the metal target, and metal atoms are sputtered and deposited on the substrate to form a metal thin film. A metal thin film deposition process may also be employed the following specific actions: selecting the desired powder metal material is placed in the evaporation crucible, placed in a good spin-coating PMMA substrate, the background vacuum chamber was evacuated to ^{^10-4-10--} Below ⁵ Pa, it is guaranteed that there are no other impurity gases under vacuum conditions during metal film deposition. Turn on the power of the electron beam, maintain its output power at 800-3000W, and excite the electron beam to heat and vaporize the metal material in the crucible, so that the metal material is deposited on the substrate. In addition, the atmospheric pressure is controlled during the metal thin film deposition process. The air pressure is low. When the air pressure is low, the metal thin film deposition rate will be slow, so the grains of the metal thin film will be smaller, and the internal stress of the metal thin film will be smaller. It is beneficial to the peeling of the metal film and is not brittle. When the particle size of the metal film is too large, the internal stress of the metal film will be relatively large. In this way, the metal film is relatively easy to break during the peeling process of the metal film, so it is assured during the metal film deposition process. Its low pressure vacuum environment.

S4. Peeling: The substrate with the metal film is placed in an organic solvent that can dissolve the transfer coating at normal temperature to separate the metal film. Specifically, the substrate with the metal film deposited to a predetermined thickness is immersed in organic Among the solvents, the organic solvent here is a solvent that can dissolve the transfer coating without damaging the substrate and the metal thin film. In this way, during the process of dissolving the transfer coating by the organic solvent, the substrate and the metal film are not affected by the solvent. For example, when the transfer coating is PMMA, the organic solvent may be acetone. In addition, in the process of solvent-solvent transfer coating, the temperature must be maintained at normal temperature, for example, the temperature is controlled at 25 ± 5 ° C until the metal thin film is completely separated from the substrate. In addition, it should be explained here that the smaller the relative molecular mass of PMMA, the easier the metal film formed on the surface is peeled off. For example, 300 nm Ag is peeled off. The relative molecular mass of PMMA is 50 K and the thickness is 300 nm. The metal film and the substrate can be easily and naturally separated.

S5. Transfer: Keep the metal film in the unfolded state and transfer the metal film to dry under oxygen-free conditions to obtain the final independent metal film. Specifically, after the metal thin film is separated from the substrate, the metal thin film will be suspended in the solution, and there must be a patent process for the metal thin film in the use of the metal thin film. Here, the metal thin film must be kept in an unfolded state during the transfer process. The removed metal film is dried in an anaerobic condition, so as to obtain the final independent metal film, which can be used in various scenarios. The anaerobic condition here may be that the metal thin film is taken out of the solution and then dried in a nitrogen box. Of course, the anaerobic environment is not limited to the above description.

Further, in step S1, during the spin coating process on the substrate surface, the thickness of the transfer coating layer is 0.5-2 times the preset thickness of the metal thin film. Specifically, in order to ensure that the thickness of the finally obtained metal film meets the requirements, the thickness of the transfer coating usually meets the target thickness of the metal film by 0.5-2 times. In this way, the quality of the metal film and the quality of the metal film during the deposition process can be guaranteed. The integrity of the metal film is ensured during the subsequent metal film peeling process, that is, the deposited metal film will not be easily broken. In addition, the peeling process of the metal thin film is simplified, which reduces waste of time and materials.

Further, in step S3, during the process of depositing on the surface of the solidified transfer coating to form a metal film with a predetermined thickness, the substrate temperature does not exceed 80 ° C. Specifically, at the same time, the temperature of the substrate is monitored during the metal thin film deposition process to ensure that the temperature of the substrate does not exceed 80 ° C. When the temperature exceeds 80 ° C, the electron beam power source or the sputtering power source is stopped to stop the metal thin film. Deposition. Here, the stress of the metal thin film should be controlled during the deposition of the metal thin film. When the temperature of the substrate changes greatly during the deposition of the metal thin film, the stress of the metal thin film formed by the deposition will increase, and the metal thin film is easily broken during the peeling process. So controlling the substrate temperature is also a key element.

Further, filling argon under vacuum includes filling argon to a pressure of 0.4-4Pa. Specifically, as described earlier, during the metal thin film deposition process, the ambient air pressure has an impact on the grain structure and stress of the metal thin film. In this way, when filling argon gas in a vacuum environment, it must be ensured that the argon gas can satisfy the metal The requirements of the thin film deposition process, and at the same time ensure that the grain structure and stress of the generated metal thin film meet the needs of the metal thin film peeling process. In this way, the argon gas pressure environment can satisfy 0.4-4Pa. In addition, it can be understood that the gold (Au) film maintained at a vacuum of 0.4 Pa during metal film deposition is more likely to peel off, and the peeled metal film is more likely to maintain integrity.

Further, in step S3, the preset thickness of the metal thin film is 50-1000 nm. Specifically, during the metal thin film deposition process, the crystal film technology can be used to monitor the thickness of the film, so that the thickness of the final metal thin film can meet 50-1000 nm, so as to ensure easier stripping of the metal thin film and ensure its integrity during the stripping process. .

Further, in step S1, the surface flatness of the substrate is ± 10 nm / cm ² , and the property does not change at a temperature of 180 ° C. Specifically, the flatness of the substrate surface is controlled to ensure that the flatness of the spin-coated transfer coating can meet the requirements, and finally the flatness of the obtained metal film can meet the requirements

Further, in step S3, the metal material is one or more of Au, Ag, Cu, Cr, Al, Ni, and Ti. Specifically, the metal material may be any one of gold (Au), silver (Ag), platinum (Pt), copper (Cu), chromium (Cr), titanium (Ti), iron (Fe), and nickel (Ni). There may be multiple kinds, for example, an alloy composed of multiple metal materials.

Further, in step S5, the transfer process includes using a mesh structure or a hollow ring frame tool to lift the metal thin film to keep the metal thin film in an unfolded state. Specifically, the metal thin film is suspended in the solution after being separated from the substrate. At this time, if the metal thin film is directly taken out, the metal thin films are easily entangled together. Therefore, a hollow ring frame or mesh structured tool can be used to hold the metal film from below, so that the metal film remains unfolded on the surface of the hollow ring frame or meshed tool, and the hollow and mesh structure can The solution is filtered off, so that the transfer of the metal film is very important.

As shown in FIG. 3 and FIG. 4, after the step S2, the following steps are further performed: S2-1. Preset pattern: A preset pattern is set on the surface of the solidified transfer coating. Specifically, a corresponding mold can be used to emboss the top surface of the spin-coated transfer coating to make the final metal thin film form the final required pattern. It can be understood here that the pattern on the transfer coating is opposite to the pattern of the final metal thin film. The independent metal thin film material with a specific surface shape can be processed according to needs, and is not limited to making a flat independent metal thin film. In addition, here, the metal material is heated and vaporized by the electron beam power source under vacuum conditions to deposit and generate a metal thin film on the surface of the transfer coating layer to better achieve step coverage and micro-hole coverage of large and deep pores. .

In addition to the simple metal film preparation process described above, in addition to simple operation and low cost, and the temperature of the metal film is kept at room temperature during the deposition and peeling process, the thermal stress of the metal film is small, and the metal film can maintain better toughness, so that Not easy to crack during use. And it can effectively peel out a whole 3D structure metal thin film material with a thickness of tens to hundreds of nanometers. In addition, through the above process, an independent metal thin film having a large area can be formed, and the area of the independent metal thin film can be up to 10 cm * 10 cm.

In addition, the metal thin film of the present invention can be prepared by the above-mentioned partial method. According to the above method for preparing an independent metal thin film, an independent metal thin film finally required can be prepared, and more usage scenarios are also satisfied. The metal film obtained by the above method has low thermal stress, can maintain better toughness of the metal film, and is not easily broken during use. Zh

It can be understood that the above examples only express the preferred embodiments of the present invention, and their descriptions are more specific and detailed, but cannot be understood as a limitation on the scope of the patent of the present invention; it should be noted that for those of ordinary skill in the art In other words, without departing from the concept of the present invention, the above technical features can be freely combined, and several modifications and improvements can be made, all of which belong to the protection scope of the present invention; All equivalent transformations and modifications made shall fall within the scope of the claims of the present invention.

Claims

A method for preparing an independent metal thin film, comprising the following steps:

S1. Spin-coating a transfer coating: selecting a substrate whose surface satisfies optical level flatness, cleaning and drying the substrate, and spin-coating the transfer coating on the surface of the substrate;

S2: curing: evaporating and cooling the substrate after the transfer coating is spin-coated to cure the transfer coating;

S3. Deposition: a metal material is selected and deposited on the surface of the cured transfer coating to generate a metal film of a preset thickness; the deposition includes:

Filling argon under vacuum and depositing the metal thin film on the surface of the transfer coating by a sputtering power source; or

Heating and vaporizing the metal material by an electron beam power source under a vacuum condition to deposit and generate the metal thin film on the surface of the transfer coating;

S4. Peeling: placing the substrate with the metal thin film in an organic solvent capable of dissolving the transfer coating at normal temperature to separate the metal thin film;

S5. Transfer: Keep the metal thin film in an unfolded state and transfer the metal thin film to dry under oxygen-free conditions to obtain a final independent metal thin film.
The method for preparing an independent metal thin film according to claim 1, wherein in the step S1, in the process of spin-coating a transfer coating on the surface of the substrate, the thickness of the transfer coating is the thickness of the transfer coating. The metal film has a preset thickness of 0.5-2 times.
The method for preparing an independent metal thin film according to claim 1, wherein in the step S3, during the process of depositing on the surface of the solidified transfer coating to generate a metal thin film of a preset thickness, the substrate The temperature does not exceed 80 ° C.
The method for preparing an independent metal thin film according to claim 2, wherein in step S3, the filling of argon under vacuum comprises filling argon to a pressure of 0.4-4Pa.
The method for preparing an independent metal thin film according to claim 1, wherein in the step S3, the preset thickness of the metal thin film is 50-1000 nm.
The method of claim 1, wherein in the step S1, the surface flatness of the substrate is ± 10 nm / cm 2 .
The method of claim 1, wherein in step S3, the metal material is one or more of Au, Ag, Cu, Cr, Al, Ni, and Ti.
The method for preparing an independent metal thin film according to claim 1, wherein in the step S5, the transferring process comprises using a mesh structure or a hollow ring frame tool to lift the metal thin film to hold the metal thin film. The metal thin film is in a deployed state.
The method of claim 1, wherein after the step S2, the following steps are further performed:

S2-1. Preset pattern: A preset pattern is set on the surface of the solidified transfer coating.
A metal thin film, which is obtained by the method for preparing an independent metal thin film according to any one of claims 1-9.