JPH01269941A - Formation of fine pattern - Google Patents

Abstract

PURPOSE:To easily remove the residue of a resist and to form the fine pattern of superior size accuracy efficiently by removing the resist residue after dry etching by processing a metal film by wet etching. CONSTITUTION:When the fine pattern is formed by lithography, a work P is dipped in wet etching liquid for metal after a process for obtaining the pattern of a thin film by dry etching and the liquid is stirred at simultaneously to etch the flank of a metal film 3. Further, the etching is advanced, the undercut of the metal film 3 is developed to disconnect the resist residue 7 on the top surface of the metal, so that the residue is removed from the work P. Consequently, the resist residue is easily removed and the fine pattern of superior size accuracy is formed efficiently.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for forming a fine pattern by lithography, and in particular, to easily remove resist residue and form a fine pattern with excellent dimensional accuracy. This invention relates to a method for forming fine patterns.

[Prior Art] Conventionally, there has been a method for forming fine patterns by phosphorography using 11-ray beams, ultraviolet rays, X-rays, etc.

It is applied to the manufacture of diffraction gratings for optical equipment, thin film optical devices, semiconductor devices, etc.

FIG. 3 is a pattern forming process diagram of an example of a method for forming a fine pattern by conventional lamination lithography, and FIG. 4 is a pattern forming process diagram of another example.

The method shown in FIG. 3 is a method of forming fine patterns using electron beams, ultraviolet rays, or X-rays, or by a lithography method, and this method involves coating a resist 4 on a pattern-forming thin film 2 on a substrate 1. irradiating the irradiated portion 5 of the resist 4 with an electron beam (or ultraviolet rays, It consists of a step of developing the pattern, a step of dry etching the pattern forming thin film 2 using the resist pattern 6 obtained by this development as a mask, and a final step of removing unnecessary resist residue 7. After removing this resist residue 7, a desired fine pattern 8 is obtained.

The device shown in Figure 4 uses a dielectric material with high electrical insulation as a substrate in the phosphorography method using an electron beam, and in this case, the electrostatic charge when irradiated with the electron beam is reduced. In order to prevent this, an antistatic metal film 9 is formed on the upper surface of the resist 4. That is, a step of forming a pattern forming thin film 2 on a dielectric substrate 1, a step of applying a resist 4, a step of forming an antistatic metal film 9 thereon, and a step of depositing electrons on this metal film 9. A step of cross-linking the resist by irradiating a line, a step of removing the antistatic metal film 9, a step of developing the resist with an organic solvent, and using the resist pattern 6 as a mask,
a step of dry etching the pattern forming thin film 2;
The process includes a step of removing resist residue 7 after dry etching, and after removing resist residue 7, a desired fine pattern 8 is obtained.

[Problem to be solved by the invention] In the conventional technology described above, in obtaining a fine pattern,
There was a problem in that it was extremely difficult to remove resist residue after dry etching. In other words, cyst residues are: ■ three-dimensionally cross-linked or polymerized by electron beams, etc.; ■ complexly altered due to exposure to plasma during the dry etching process; It is insoluble in acids, alkalis, etc., and although conventional wet methods have been used, its removal has not been easy.

Removal methods using dry methods such as oxygen plasma and Ar ions have been considered, but resist residues cannot be completely removed. When this dry method is used, there is a problem that a fine pattern with desired dimensional accuracy cannot be obtained because the quality of the substrate changes or the shape of the fine pattern is deformed due to overetching.

In order to solve this problem, as disclosed in Japanese Patent Laid-Open No. 59-136931, a new thin film (A) is formed between the substrate and the resist, and after forming a resist pattern, this resist pattern is The thin film (A) as a mask
There is a method of wet etching the resist, removing the resist, and using the thin film (A) pattern obtained by this wet etching as a mask, plasma etching the pattern forming thin film or substrate to be patterned to obtain a desired fine pattern. Are known. According to this method, the resist is removed before it is exposed to plasma, so
It has the advantage that it does not cause resist deterioration and can be removed with various organic solvents, acids, or alkalis. However, since the thin film (A) pattern is formed by wet etching, there are disadvantages of this wet etching such as thinning of the pattern and set pack, and there is a problem that a fine pattern with high dimensional accuracy cannot be obtained.

The present invention solves the problems of the prior art as described above, and provides a method for forming fine patterns that can easily remove residual resist and efficiently form excellent fine patterns in one dimension. Its purpose is to

[Means for Solving the Problems] The structure of the method for forming a fine pattern according to the present invention for solving the above problems is to apply a resist onto a thin film for pattern formation on a substrate, and cross-link this resist. A method for forming a fine pattern using a lithography method, in which a desired fine pattern is formed by dry etching the pattern-forming thin film using a resist pattern obtained by development as a mask, and then removing resist residue. In this method, a resist is applied onto a pattern-forming thin film through a metal film, and the resist residue after dry etching is removed by wet etching the metal film.

More specifically, etching is achieved by forming a metal film between the resist and the substrate, forming a fine pattern by dry etching, and then wet etching the metal film. Since this metal film is dissolved and the resist residue formed thereon is peeled off at the same time, the resist residue can be easily removed.

[Operation] A resist pattern obtained by crosslinking and developing the resist is used as a mask to dry-etch the pattern-forming thin film (this procedure is the same as the conventional method).

Next, when the metal film is dissolved by wet etching,
The resist residue on the upper surface of the metal film is removed by cutting from the pattern-forming thin film to obtain a desired fine pattern.

[Example code] Hereinafter, the present invention will be explained by examples.

FIG. 1 is a pattern forming process diagram of a method for forming a fine pattern according to an embodiment of the present invention, and FIG. 2 is a schematic diagram showing details of wet etching in FIG. 1.

The method for forming this fine pattern will be explained with reference to FIG. 1. It consists of a step of forming a pattern-forming thin film 2 on a substrate 1, and a step of forming a metal film 3 on this pattern-forming thin film 2. , a step of applying resist 4 thereon;
A process of irradiating electron beams, ultraviolet rays, or X-rays from the resist 4 side, a process of developing the irradiated portion 5 of the resist 4 to obtain a resist pattern 6, and dry etching using this resist pattern 6 as a mask to form a thin film pattern ( This consists of a step of obtaining a fine pattern 8) and a step of simultaneously removing the metal film 3 and the resist residue 7 by wet etching the metal film 3 (details will be described later). As a result, a desired fine pattern 8 is obtained.

The process of removing the resist residue 7 by wet etching will be explained in detail with reference to FIG.

After the step of obtaining a thin film pattern by dry etching, the workpiece P is immersed in a metal wet etching solution (not shown), and the solution is simultaneously stirred. As a result, the side surface of the metal film 3 is etched.

As the etching progresses further, the undercut of the metal film 3 progresses, and the resist residue 7 on the upper surface of the metal is cut off and removed from the workpiece P, and a desired fine pattern 8 is obtained.

A specific example will be shown below.

Specific Example 1 An example in which synthetic quartz, which is a dielectric with high electrical resistance, is used as the substrate 1, and a fine pattern 8 of SiO is formed thereon.

A pattern-forming thin film 2 of SiO2 was formed to a thickness of 1 μm on a cleaned synthetic quartz substrate 1 by sputtering. On this thin film 2, a Ti metal film 3 was formed to a thickness of 0.2 μm using a resistance heating vacuum evaporation method, and then a negative ultraviolet resist according to the resist 4 was formed to a thickness of 0.8 μm using a spin code method. . Next, the resist 4 was exposed to light using an ultraviolet exposure device to form 100 fine patterns of 0.5 μm lines and spaces. After removing the portions not irradiated with ultraviolet rays using an organic solvent, reactive ion etching related to dry etching was performed using CF and gas using the obtained resist pattern 6 as a mask. Next, H,0,: 187mR.

NH4OH: 15mQ, EDTA: 7.3g.

The Ti film was removed by wet etching using a Ti etching solution consisting of 300 mff1 of H2O. By performing this wet etching.

The resist residue 7 has peeled off and is floating in the Ti etching solution! At the same time as the m T l was removed, the resist residue 7 was completely removed, and a desired fine pattern 8 of Sin was obtained.

This product is used, for example, as a diffraction grating for optical equipment.

Specific example 2 The substrate 1 is a dielectric crystal LiNb0. using
An example in which a fine pattern 8 of TiO□ is formed on this.

Using an optical waveguide substrate according to the substrate 1 obtained by diffusing about 1 μm of Ti on the surface of cleaned LiNb○, a thin film 2 for pattern formation of TiO2 was formed to a thickness of 0.1 μm by reactive sputtering method using 0□. was formed. Next, this Ti○2
A metal film 3 of Au is deposited on the thin crotch by sputtering method.
A negative type electron beam resist corresponding to resist 4 was formed to a thickness of 0.8 μm using a spin code method. Next, the resist 4 was exposed using an electron beam lithography '3A setting, and a condensing grating coupler consisting of a hyperbolic pattern whose line spacing gradually changed was drawn. The average line width is about 1 μm, and the number of lines is about 800.
It was a book. The electron beam irradiation conditions were an applied voltage of 30 kV,
Dose amount: 35μC/cJ, current density: 4.7μA/m
It was set as m. Developer (isoamyl acetate: 15vo
After removing the unirradiated areas with the electron beam using a mixture of 1% and ethyl cellosolve: 85v01%), post-bake (1%
30° C. for 30 minutes), and using the obtained resist pattern 6 as a mask, TiO□ was dry etched.

The dry etching was carried out using a parallel plate type dry etching apparatus using CF as an etchant. Next, I2: 4.5 g, NH41: 30 g.

Hz O: 150 mQ, Cz H-OH: 2
Au etching solution consisting of 25 mQ
was wet etched. This wet etching was carried out for 20 minutes at a liquid temperature of 25° C. while applying ultrasonic waves.

It was confirmed that this etched the Au and completely removed the resist residue 7 on the Au. After cleaning with s H, ○, the fine pattern 8 of TiO2 was removed.
was gotten.

This product is used as an optical element with a light deflection function.

Specific example 3 Si, which is a semiconductor, is used as the substrate 1, and Si
An example of forming a fine pattern 8 of O2.

The cleaned n-type Si substrate 1 was thermally oxidized, and a thin rv 42 for pattern formation of SiO2 having a thickness of 0.3 μm was formed thereon. Next, on this SiO2 thin plate, a metal film 3 of gold gLCr is formed to a thickness of 400 μm by sputtering, and a positive X-ray resist (silicone resin) for the resist 4 is formed on this by a spin code method to a thickness of 0.9 μm. Formed. Next, the resist 4 is exposed using an X-ray exposure device,
Ten fine patterns of 1 μm lines and spaces were formed.

After removing the X-ray irradiated portion with an organic solvent developer, post-baking (130° C., 30 minutes) was performed, and using the resulting resist pattern 6 as a mask, the Sin was dry-etched. This dry etching uses a parallel plate type dry etching device, and uses C as a niche layer.
The experiment was carried out using HF. Then Ce (No,) 4
・2NH4・No.

The Cr film was wet-etched using a Cr etching solution consisting of an aqueous solution in which 42 mQ of perchloric acid was dissolved and diluted to 10,100 O. This wet etching was carried out for 10 minutes at a liquid temperature of 25° C. while applying ultrasonic waves. As a result, the Cr was etched and the resist residue 7 on the Cr was completely removed, and a fine pattern 8 of 1 μm fine grooves was formed in the SiO2 thin film formed on the Si substrate 1.

This product is used as a semiconductor device.

According to the embodiment described above, the resist residue 7 altered by dry etching can be easily removed, so that a fine pattern 8 having a finer shape and excellent dimensional accuracy having a nearly rectangular shape can be obtained.

In addition, since the metal film 3 is used to remove the resist residue 7, it can be removed using an electron beam or lithography.
Even when a highly electrically insulating material is used as the substrate 1, there is an advantage that charging does not occur during electron beam irradiation and a finer pattern 8 can be obtained.

[Effects of the Invention] As described in detail above, the present invention provides a method for forming a fine pattern that can easily remove resist residue and efficiently form a fine pattern with excellent one-dimensional accuracy. can do.

[Brief explanation of the drawing]

FIG. 1 is a pattern forming process diagram of a method for forming a fine pattern according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing details of wet etching in FIG. 1, and FIG. FIG. 4 is a pattern forming process diagram of an example of a method for forming a fine pattern using the lithography method, and FIG. 4 is a pattern forming process diagram of another example. 1... Substrate, 2... Thin film for pattern formation, 3...
Metal film, 4... Resist, 6... Resist pattern, 7... Resist residue, 8... Fine pattern.

Claims (1)

[Claims] 1. By applying a resist onto a thin film for pattern formation on a substrate, crosslinking and developing this resist, dry etching the thin film for pattern formation using the resulting resist pattern as a mask, and then removing the resist residue. , in a method of forming a fine pattern by lithography, in which a desired fine pattern is formed, a resist is applied onto a pattern-forming thin film through a metal film,
A method for forming a fine pattern, characterized in that resist residue after dry etching is removed by wet etching the metal film.