CN105301896B - Photoetching method based on metal glass film phase-change material - Google Patents

Abstract

The invention discloses a photolithography method based on a phase change material of a metallic glass thin film, which belongs to the field of semiconductor micro-nano processing; in the prior art, the etching edge of the multilayer film is blurred and not steep enough; the method provided by the present invention utilizes Pr ‑based metallic glass phase change material film is used as photoresist, Pr‑based metallic glass is a metallic glass phase change material with high thermal stability, low crystallization temperature, suitable for laser direct writing exposure induced thermal phase change; The high conductivity is beneficial to accurately control the line width of the crystallization pattern by changing the laser power; it is non-toxic and harmless, and has no pollution to the environment; the etching selection ratio is high, and the etching selection ratio can reach 5:1, and the process is simple and controllable , the production cycle is short, and it is very suitable for phase change lithography technology.

Description

A lithography method based on metallic glass thin film phase change material

technical field

The invention belongs to the field of semiconductor micro-nano processing, and more particularly relates to a photolithography method of a phase-change material photoresist Pr-based metallic glass thin film based on a high etching selectivity ratio in a specific etching solution and simple operation.

Background technique

In the current manufacturing process of semiconductor devices, optoelectronic devices, MEMS devices and other micro-nano devices, photolithography is one of the most important technologies. In order to prepare micro-nano apertures, the current mainstream methods are divided into three types: electron beam lithography, focused ion beam lithography, and optical lithography.

Since electron beam lithography and focused ion beam lithography need to be carried out in a strict vacuum environment, if the vacuum degree cannot reach the standard, the accumulation of dust on the optical device will lead to the distortion of the engraved pattern; the equipment is expensive, and the lithography efficiency is very high low, not suitable for commercial mass production. Therefore, by far the most widely used optical lithography.

Traditional optical lithography uses 200nm-450nm ultraviolet light as the lithography light source, and uses photoresist (commonly known as photoresist) as the intermediate medium to realize the transformation, transfer and processing of the pattern, and finally transmit the image information to the wafer. (mainly referring to silicon wafer) or a process on the dielectric layer. The minimum resolution it can achieve is determined by the following formula:

where R is the optical resolution, λ is the lithography laser wavelength, and NA is the numerical aperture of the focusing objective. According to the formula, the resolution can be directly and effectively reduced by reducing the laser wavelength λ and increasing the numerical aperture NA. However, when the laser wavelength is reduced to the ultraviolet and deep ultraviolet bands, conventional optical components have strong absorption in this band, and ultraviolet-transmitting materials such as CaF ₂ must be used, which greatly increases the cost of lithography; and the limit of numerical aperture in air is The value is 1.0, and the 0.9 currently used does not have much room for improvement. Therefore, in order to meet the development of science and technology and ensure the continuation of Moore's Law, new lithography technology is being put into a lot of research.

Phase-change lithography uses inorganic phase-change materials (such as GeSbTe) as photoresist to deposit on the substrate surface with an appropriate thickness, and then uses a modulated laser beam to expose the phase-change material film according to the desired shape pattern. After that, the exposed area will undergo a phase transition due to laser heating when the temperature exceeds the phase transition temperature, while the unexposed area remains amorphous and remains unchanged, the film is immersed in the etching solution, and the exposed area (crystalline state) The preparation of the micro-nano structure is completed by the etching difference between the unexposed area (amorphous state) in the etching solution.

Most of the current research on phase change lithography is based on chalcogenide semiconductor phase change materials (such as GeSbTe, AgInSbTe, etc.) and its multilayer film structure, and the etching selectivity ratio of chalcogenide semiconductor monolayer film materials (that is, two-phase etching Etch rate ratio) is not high, only about 2, and the etching edge of the multilayer film is blurred and not steep enough. Therefore, the research of new phase change lithography materials is particularly important for the development of phase change lithography.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the problems of the above technology because the etching edge of the multi-layer film in the prior art is blurred and not steep enough.

In order to achieve the above object, the present invention provides a lithography method based on a metallic glass thin film phase change material, characterized in that the method comprises the following steps:

(1) depositing a layer of the metallic glass amorphous film on the surface of the quartz substrate by magnetron sputtering;

(2) Selective laser exposure is performed on the obtained deposited thin film, and the laser power is adjusted so that the exposed area reaches the crystallization temperature and undergoes a phase transition, thereby producing the desired crystallization nanopattern;

(3) The thin film sample of the crystallized nanopattern that has been subjected to selective exposure treatment is put into the prepared nitric acid solution for etching to form the desired nanopattern;

The metallic glass thin film phase change material is a Pr-, Ni-, Nd-, La-, Pt- or Ce-based metallic glass thin film phase change material.

Preferably, the nitric acid solution is an aqueous nitric acid solution or a nitric acid ethanol solution;

Preferably, the nitric acid used in preparing the nitric acid aqueous solution is 65% concentrated nitric acid, wherein the volume ratio of concentrated nitric acid to water is 1:180, and the mass fraction of the prepared nitric acid aqueous solution is 0.5%.

Preferably, the etching temperature is from room temperature to 40° C., and the time is 5s-50s.

Through the above technical solutions conceived by the present invention, compared with the prior art, the following beneficial effects can be achieved:

Using Pr-based metallic glass phase change material film as photoresist, Pr-based metallic glass is a kind of metallic glass phase change material with high thermal stability, low crystallization temperature, suitable for laser direct writing exposure induced thermal phase change ; High thermal conductivity, which is beneficial to accurately control the line width of the crystallization pattern by changing the laser power; non-toxic and harmless, no pollution to the environment; high etching selection ratio, can reach 5:1 etching selection ratio, very suitable in phase change lithography.

Description of drawings

Fig. 1 is the flow chart of using Pr-based metallic glass phase change material as photoresist;

Figure 2 is a metallographic microscope image of the crystallization of the amorphous film of PrAlNiCu phase change material after laser direct writing exposure;

Figure 3 is a comparison diagram of the XRD patterns of the PrAlNiCu phase change material film before and after exposure;

FIG. 4 is a graph comparing the curves of the etching amount and the etching time of the PrAlNiCu amorphous thin film and the crystalline thin film in a 0.5% mass fraction of nitric acid solution.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

As shown in Figure 1, a layer of Pr-based metallic glass amorphous film was deposited on the surface of the quartz substrate by magnetron sputtering, and the obtained as-deposited film was subjected to selective laser exposure, and the laser power was adjusted to make the exposure area reach the crystallization temperature. A phase transition occurs to produce the desired crystalline nanopattern, that is, the exposed part changes from amorphous to crystalline; the thin film sample of the crystalline nanopattern that has undergone selective exposure treatment is placed in a nitric acid solution that has been prepared in a specific proportion Etching is performed, and after the etching is completed, it is placed in clean water for cleaning and drying, and the desired nano-pattern is finally prepared.

Further, the nitric acid solution is an aqueous nitric acid solution or a nitric acid alcohol solution, preferably an aqueous nitric acid solution;

Further, the nitric acid used in the prepared nitric acid aqueous solution is 65% concentrated nitric acid, wherein the volume ratio of concentrated nitric acid to water is 1:180. The mass fraction of the prepared nitric acid aqueous solution was 0.5%.

Further, the etching temperature is from room temperature to 40°C, preferably 25°C.

Further, the etching time in the nitric acid solution is 5s-50s.

Further, the exposure uses laser direct writing technology;

(1) The laser wavelength used is 661 nm;

(2) The numerical aperture of the laser focusing lens used is 0.4;

(3) The laser power is 30mW-80mW;

(4) The laser exposure time is 50us-2ms.

Further, the photolithography method is applicable to Ni-, Nd-, La-, Pt- or Ce-based metallic glasses in addition to Pr-based metallic glasses.

Further, the Pr-based metallic glass thin film is prepared by using a Pr-based metallic glass target and deposited on a single crystal silicon substrate by magnetron sputtering.

Further, the thickness of the thin film is 200nm-400nm, preferably 300nm.

Example 1:

A layer of 300nm PrAlNiCu metallic glass thin film was sputtered on a quartz substrate with a thickness of 1mm by the method of magnetron sputtering. Among them, the specific sputtering parameters are direct current sputtering (DC), the argon pressure used is 0.3pa, the sputtering power is 60W, the target base distance is 120mm, the sputtering time is 15 minutes, and the pre-sputtering is 15 minutes before sputtering.

Using laser to expose, the specific steps are as follows: by fixing the laser light source, placing the sample on the movable motor, importing the required nanopattern into the computer step by step, and using the computer to control the motor step by step, so that the required The nanopattern is directly written by selective exposure. Figure 2 shows the pattern observed by a metallographic microscope after exposure. As shown in FIG. 3 , the XRD pattern (a) before exposure is smooth without protrusions, and is amorphous; the XRD pattern (b) after exposure shows obvious diffraction peaks and is crystalline.

The exposed samples were placed in the prepared nitric acid aqueous solution for etching, the mass fraction of the nitric acid solution was 0.5%, and the etching time was 5s, 10s, 15s, 20s, 25s, 30s, 35s, 40s, 45s, 50s. The amount of etching at each time point is shown in Figure 4.

As shown in Figure 4, as the etching time increases, the amount of etching increases linearly, but the etching rate of the amorphous state is not consistent with the etching rate of the crystalline state, and the etching rate of the amorphous PrAlNiCu About 10.053nm per second, while the etching rate of crystalline PrAlNiCu is about 2.004nm per second, the etching selectivity ratio of amorphous and crystalline PrAlNiCu in the etching solution is about 5:1, showing excellent phase change lithography potential.

Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims (4)

1. A photoetching method based on a metal glass film phase-change material is characterized by comprising the following steps:

(1) depositing a layer of metallic glass amorphous film on the surface of the quartz substrate by magnetron sputtering;

(2) carrying out selective laser exposure on the obtained deposition-state film, and adjusting the laser power to enable an exposure area to reach a crystallization temperature to generate phase change so as to generate a required crystallized nano pattern;

(3) putting the film sample of the crystallized nano pattern subjected to selective exposure treatment into a prepared nitric acid solution for etching to form a required nano pattern;

the metal glass film phase-change material is a Pr-based metal glass film phase-change material;

the nitric acid solution is a nitric acid aqueous solution, the nitric acid used in the preparation of the nitric acid aqueous solution is 65% concentrated nitric acid, wherein the volume ratio of the concentrated nitric acid to water is 1:180, and the mass fraction of the prepared nitric acid aqueous solution is 0.5%.

2. The method of claim 1, wherein the etching temperature is from room temperature to 40 ℃ for 5s to 50 s.

3. The method according to claim 1, wherein the Pr-based metallic glass thin film phase change material is prepared by depositing on a quartz substrate by magnetron sputtering using a Pr-based metallic glass target.

4. The method of claim 1, wherein the thin film has a thickness of 200nm to 400 nm.

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