CN105301896B

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

Info

Publication number: CN105301896B
Application number: CN201510828527.8A
Authority: CN
Inventors: 缪向水; 罗腾; 李震
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2015-11-25
Filing date: 2015-11-25
Publication date: 2020-01-10
Anticipated expiration: 2035-11-25
Also published as: CN105301896A

Abstract

The invention discloses a photoetching method based on a metallic glass film phase-change material, belonging to the field of semiconductor micro-nano processing; in the prior art, the etching edge of the multilayer film is fuzzy and not steep enough; according to the method provided by the invention, the Pr-based metal glass phase-change material film is used as the photoresist, the Pr-based metal glass is a metal glass phase-change material with high thermal stability, the crystallization temperature is low, and the method is suitable for laser direct writing exposure induced thermal phase change; the thermal conductivity is high, and the line width of the crystallized pattern can be accurately controlled by changing the laser power; no toxicity and harm, no pollution to environment; the etching selection ratio is high and can reach 5:1, the process is simple and controllable, the production period is short, and the phase-change photoetching technology is very suitable for phase-change photoetching.

Description

Photoetching method based on metal glass film phase-change material

Technical Field

The invention belongs to the field of semiconductor micro-nano processing, and particularly relates to a phase-change material photoresist Pr-based metal glass film photoetching method based on high etching selectivity in specific etching liquid and simple to operate.

Background

In the manufacturing process of micro-nano equipment such as a semiconductor device, a photoelectronic device, a micro-electro-mechanical system device and the like, a photoetching process is one of the most important technologies. In order to prepare micro-nano aperture, the current mainstream methods are divided into three types: electron beam lithography, focused ion beam lithography, optical lithography.

Because electron beam lithography and focused ion beam lithography need to be performed in a strict vacuum environment, if the vacuum degree cannot reach the standard, the accumulation of dust on an optical device can cause the distortion of a carved pattern; the equipment is expensive, and the lithography efficiency is very low, which is not suitable for commercial mass production. Optical lithography is therefore by far the most widely used.

The traditional optical lithography is a process of using ultraviolet light of 200 nm-450 nm as a lithography light source, using a photoresist (commonly called as photoresist) as an intermediate medium to realize the transformation, transfer and processing of patterns, and finally transmitting image information to a wafer (mainly referring to a silicon wafer) or a dielectric layer. The minimum resolution that can be achieved is determined by the following equation:

wherein R is the optical resolution, lambda is the photoetching laser wavelength, and NA is the numerical aperture of the focusing objective lens. According to the formula, the resolution can be directly and effectively reduced by lowering the laser wavelength lambda and increasing the numerical aperture NA. However, when the laser wavelength is reduced to the ultraviolet and deep ultraviolet band, the absorption of the conventional optical components is very strong in the band, and CaF must be used₂The ultraviolet-transmitting materials greatly increase the photoetching cost; the limit value of the numerical aperture in the air is 1.0, and the currently used 0.9 has no too large lifting space. Therefore, in order to satisfy the development of technology and to ensure the continuation of moore's law, a new type of lithography technology is being invested in a great deal of research.

Phase change photoetching utilizes inorganic phase change material (such as GeSbTe) as photoresist to deposit on the surface of a substrate with proper thickness, then utilizes a modulatable laser beam to expose a phase change material film according to a required shape pattern, after laser exposure, an exposure area can generate phase change when the temperature exceeds the phase change temperature due to laser heating, an unexposed area still remains an amorphous state, the film is immersed in etching liquid, and the preparation of a micro-nano structure is completed by utilizing the etching difference between the exposure area (crystalline state) and the unexposed area (amorphous state) in the etching liquid.

Most of the current phase-change photoetching researches are based on chalcogenide semiconductor phase-change materials (such as GeSbTe, AgInSbTe and the like) and multilayer film structures thereof, the etching selection ratio (namely the etching rate ratio of two phases) of chalcogenide semiconductor single-layer film materials is not high and is only about 2, and the etching edges of the multilayer films are fuzzy and not steep enough. Therefore, the research on novel phase-change lithography materials is particularly important for the development of phase-change lithography.

Disclosure of Invention

Aiming at the problems of the prior art that the etching edge of the multilayer film is fuzzy and not steep enough, the invention aims to solve the technical problems.

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

(1) depositing a layer of the metal glass amorphous film on the surface of the quartz substrate through 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 Pr-, Ni-, Nd-, La-, Pt-or Ce-based metal glass film phase change material.

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

preferably, the nitric acid used in the aqueous nitric acid 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 aqueous nitric acid solution is 0.5%.

Preferably, the etching temperature is between room temperature and 40 ℃ and the time is between 5s and 50 s.

Through the technical scheme, compared with the prior art, the invention has the following beneficial effects:

the Pr-based metal glass phase-change material film is used as a photoresist, the Pr-based metal glass is a metal glass phase-change material with high thermal stability, the crystallization temperature is low, and the phase-change material is suitable for laser direct writing exposure induced thermal phase change; the thermal conductivity is high, and the line width of the crystallized pattern can be accurately controlled by changing the laser power; no toxicity and harm, no pollution to environment; the etching selection ratio is high and can reach 5:1, so that the method is very suitable for the phase-change photoetching technology.

Drawings

FIG. 1 is a flow chart of a process for using Pr-based metallic glass phase change material as a photoresist;

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

FIG. 3 is a comparison diagram of XRD patterns of a PrAlNiCu phase-change material film before and after exposure;

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

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

As shown in fig. 1, a layer of Pr-based metallic glass amorphous film is deposited on the surface of a quartz substrate by magnetron sputtering, selective laser exposure is carried out on the obtained deposited film, and the laser power is adjusted to enable an exposure area to reach the crystallization temperature for phase change, so as to generate a required crystallized nano pattern, namely, the exposed part is changed from an amorphous state to a crystalline state; and (3) placing the film sample of the crystallized nano pattern subjected to selective exposure treatment into a prepared nitric acid solution with a specific ratio for etching, and after etching, placing the film sample into clean water for cleaning and blow-drying to finally prepare the required nano pattern.

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

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

Further, the etching temperature is between room temperature and 40 ℃, and is preferably 25 ℃.

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

Further, the exposure uses a laser direct writing technique;

(1) the laser wavelength is 661 nm;

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

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

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

Further, the photolithography method is applicable to not only Pr-based metal glass but also Ni-, Nd-, La-, Pt-or Ce-based metal glass.

Further, the Pr-based metal glass film is prepared by adopting a Pr-based metal glass target material and depositing on a monocrystalline silicon substrate by utilizing magnetron sputtering.

Further, the film thickness is 200nm to 400nm, preferably 300 nm.

Example 1:

a layer of 300nm PrAlNiCu metal glass film is sputtered on a quartz substrate with the thickness of 1mm by a magnetron sputtering method. Wherein the specific sputtering parameters are direct current sputtering (DC), the used argon pressure 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 carried out for 15 minutes before sputtering.

The laser exposure method comprises the following steps: by fixing the laser light source, placing the sample on the movable motor, introducing the required nano patterns into the computer in a stepping sequence, and performing stepping control on the motor by using the computer, the required nano patterns are selectively exposed and directly written, and fig. 2 shows that the patterns are observed by using a metallographic microscope after exposure. As shown in fig. 3, the XRD pattern before exposure (a) was smooth without projections and was amorphous; the XRD pattern (b) after exposure shows obvious diffraction peaks, and is crystalline.

And placing the exposed sample in a prepared nitric acid aqueous solution for etching, wherein the mass fraction of the nitric acid solution is 0.5%, and the etching time is 5s, 10s, 15s, 20s, 25s, 30s, 35s, 40s, 45s and 50s respectively. The amount of etching at each time point is shown in fig. 4.

As shown in FIG. 4, the etching amount is linearly increased with the increase of the etching time, but the etching rate of the amorphous state is not consistent with that of the crystalline state, the etching rate of the amorphous PrAlNiCu is about 10.053nm per second, the etching rate of the crystalline PrAlNiCu is about 2.004nm per second, and the etching selectivity ratio of the amorphous PrAlNiCu to the crystalline PrAlNiCu in the etching solution is about 5:1, so that the phase-change photoetching potential is excellent.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

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;

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.