JP2543947B2 - Forming method of fine pattern - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for forming a fine pattern by a lithographic method, and particularly to easily remove a resist residue and form a fine pattern with excellent dimensional accuracy. The present invention relates to a method of forming a fine pattern, which can be performed.

[Prior Art] Conventionally, a method of forming a fine pattern by a lithographic method using an electron beam, an ultraviolet ray, an X-ray or the like has been applied to the manufacture of a diffraction grating for an optical device, a thin film optical element, a semiconductor element, or the like. .

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

The method shown in FIG. 3 is a method for forming a fine pattern by a lithographic method using an electron beam, an ultraviolet ray or an X-ray, which is a method for coating a resist 4 on a thin film 2 for pattern formation on a substrate 1. And the resist 4
The step of irradiating the irradiated portion 5 of the resist with an electron beam (or ultraviolet ray, X-ray) to crosslink the resist, the step of dissolving the unirradiated portion of the resist 4 with an organic solvent to develop the pattern, The step of dry-etching the pattern forming thin film 2 is performed by using the resist pattern 6 obtained by the above as a mask, and the step of removing the resist resist 7 which is no longer needed. A fine pattern 8 is obtained.

FIG. 4 relates to a lithographic method using an electron beam, which uses a dielectric material having a high electrical insulation property as a substrate. In this case, charging when an electron beam is applied For prevention, an antistatic metal film 9 is formed on the upper surface of the resist 4. That is, the step of forming the pattern forming thin film 2 on the dielectric substrate 1, the step of applying the resist 4, the step of forming the antistatic metal film 9 thereon, and the electron from the metal film 9 The step of irradiating a line to crosslink the resist, the step of removing the antistatic metal film 9, the step of developing the resist with an organic solvent, and the resist pattern 6 as a mask to form the pattern forming thin film 2 It comprises a step of dry etching and a step of removing the resist residue 7 after the dry etching, and a desired fine pattern 8 is obtained after removing the resist residue 7.

[Problems to be Solved by the Invention] The conventional techniques described above have a problem that it is extremely difficult to remove a resist residue after dry etching in obtaining a fine pattern. That is, this resist residue is three-dimensionally cross-linked with an electron beam or the like,
Due to the fact that it is polymerized and is complicatedly altered by being exposed to plasma in the dry etching process,
It is insoluble in organic solvents as well as acids and alkalis, and although the conventional wet method has been adopted, its removal was not easy.

Although a removal method using oxygen plasma or Ar ions by a dry method has also been studied, it was not possible to completely remove the resist residue. In the case of using the dry method, there is a problem that the substrate is deteriorated or the shape of the fine pattern is deformed by over-etching, so that the fine pattern with desired dimensional accuracy cannot be obtained.

In order to solve this, as disclosed in JP-A-59-136931, a thin film (A) is newly formed between a substrate and a resist, and a resist pattern is formed. The entire thin film (A) is wet etched as a mask, the resist is removed, and the thin film (A) pattern obtained by this wet etching is used as a mask to perform plasma etching on the pattern forming thin film or substrate. A method for obtaining a desired fine pattern is known. According to this method, since the resist is removed before being exposed to plasma, there is an advantage that there is no alteration of the resist and it can be removed with various organic solvents or acids or alkalis. However, since the thin film (A) pattern is formed by wet etching, there are problems such as pattern thinning and setback, which are disadvantages of this wet etching, and a fine pattern with high dimensional accuracy cannot be obtained.

The present invention solves the above-mentioned problems of the prior art, easily removes the resist residue, and can efficiently form a fine pattern with excellent dimensional accuracy, and provide a method for forming a fine pattern, That is the purpose.

[Means for Solving the Problems] A structure of a method for forming a fine pattern according to the present invention for solving the above-mentioned problems is a pattern forming thin film forming step of forming a pattern forming thin film on a substrate, and the pattern A metal film forming step of forming a metal film on the pattern forming thin film formed in the forming thin film forming step, a resist applying step of applying a resist on the metal film formed in the metal film forming step, and the resist An exposure / development step of forming a resist pattern by cross-linking and developing the resist applied in the application step by lithography, and using the resist pattern formed in the exposure / development step as a mask to form the metal film and the pattern forming thin film. On the other hand, a dry etching step of forming a desired fine pattern by dry etching,
A wet etching step of wet-etching a metal film on a thin film formed in a desired fine pattern in the dry etching step to remove a resist residue together with the metal film to obtain a thin film having a desired fine pattern. It is characterized by.

More specifically, it 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. That is, when the metal film is wet-etched, the metal film is dissolved and the resist residue formed thereon is peeled off at the same time, so that the resist residue can be easily removed.

[Operation] The pattern forming thin film is dry-etched using the resist pattern obtained by crosslinking and developing the resist as a mask (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 separated and removed from the pattern forming thin film, and a desired fine pattern is obtained.

[Examples] Hereinafter, the present invention will be described with reference to Examples.

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

The method of forming the fine pattern will be described with reference to FIG. 1. This is a step of forming a pattern forming thin film 2 on a substrate 1 and a step of forming a metal film 3 on the pattern forming thin film 2. A step of applying a resist 4 thereon, a step of irradiating an electron beam, an ultraviolet ray or an X-ray from the side of the resist 4, a step of developing an irradiated portion 5 of the resist 4 to obtain a resist pattern 6, and a resist pattern 6
The step of obtaining a thin film pattern (which becomes the fine pattern 8) by dry etching using the mask as a mask and the metal film 3 by wet etching the metal film 3
And the step of removing the resist residue 7 at the same time (details will be described later)
The desired fine pattern 8 is obtained by completing this removing step.

The step of removing the resist residue 7 by wet etching will be described in detail with reference to FIG. 2. This is a step of obtaining a thin film pattern by dry etching, and then the work P is wet-etched with a metal wet etching solution ( (Not shown) and simultaneously stir the liquid. As a result, the side surface of the metal film 3 is etched. When the etching further progresses, the undercut of the metal film 3 progresses, the resist residue 7 on the metal upper surface is separated and removed from the workpiece P, and a desired fine pattern 8 is obtained.

 Specific examples will be shown below.

Specific Example-1 An example in which synthetic quartz, which is a dielectric having a high electrical insulation property, is used as the substrate 1 and the fine pattern 8 of SiO ₂ is formed on the synthetic quartz.

An SiO ₂ pattern forming thin film 2 having a thickness of 1 μm was formed on a cleaned synthetic quartz substrate 1 by a sputtering method. On top of this thin film 2, Ti was deposited by resistance heating vacuum deposition.
After forming the metal film 3 of No. 2 to a thickness of 0.2 μm, a negative type ultraviolet resist relating to the resist 4 is formed by spin coating to 0.2 μm.
It was formed to a thickness of 8 μm. Then, using an ultraviolet exposure device,
The resist 14 was exposed to light to form 100 fine patterns of 0.5 μm lines and spaces. After removing the portion not irradiated with ultraviolet rays with an organic solvent, reactive ion etching related to dry etching was performed using CF ₄ gas with the obtained resist pattern 6 as a mask. Then H ₂ O ₂ : 187
The Ti film was removed by wet etching using a Ti etching solution consisting of ml, NH ₄ OH: 15 ml, EDTA: 7.3 g, H ₂ O: 300 ml. By performing this wet etching, it was observed that the resist residue 7 was peeled off and floated in the Ti etching solution. At the same time as Ti, the resist residue 7 was completely removed, and a desired fine pattern 8 of SiO ₂ was obtained.

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

Specific Example-2 An example in which LiNbO ₃ which is a dielectric crystal is used as the substrate 1, and the fine pattern 8 of TiO ₂ is formed on this.

Using the optical waveguide substrate according to Substrate 1 obtained by diffusing Ti of about 1 μm on the surface of cleaned LiNbO _3, the thin film 2 for pattern formation of TiO ₂ was formed by reactive sputtering with O ₂ .
It was formed to a thickness of 1 μm. Next, an Au metal film 3 having a thickness of 300 Å was formed on the TiO ₂ thin film by a sputtering method, and a negative electron beam resist corresponding to the resist 4 having a thickness of 0.8 μm was formed thereon by a spin coating method. Next, the resist 4 was exposed using an electron beam drawing apparatus, and a converging grating coupler having a hyperbola pattern in which the line spacing was gradually changed was drawn. Average line width is about 1μ
In m, the number was about 800. The electron beam irradiation conditions were an applied voltage of 30 kV, a dose of 35 μC / cm ² , and a current density of 4.7 μA / mm ² . After removing the electron beam non-irradiated portion with a developing solution (mixture of isoamyl acetate: 15 vol% and ethyl cellosolve: 85 vol%), post-baking (130 ° C, 30 minutes) was performed to obtain the resulting resist pattern 6. TiO ₂ was dry-etched using the mask. The parallel plate type dry etching apparatus was used for the dry etching, and CF ₄ was used as an etchant. Next, I ₂ : 4.5g, NH ₄ I: 30g, H ₂ O: 150m
Au was wet-etched using an Au etching solution consisting of 225 ml of l, C ₂ H ₅ OH. This wet etching is
It was performed for 20 minutes while applying ultrasonic waves at a liquid temperature of 25 ° C. As a result, it was confirmed that Au was etched and the resist residue 7 on Au was completely removed. After cleaning with H ₂ O, a fine pattern 8 of TiO ₂ was obtained.

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

Specific Example-3 Si which is a semiconductor is used as the substrate 1, and SiO _{2 is formed} on this.
An example of forming the fine pattern 8 of FIG.

Thermally oxidize the washed n-type Si substrate 1
A 0.3 μm SiO ₂ pattern forming thin film 2 was formed. Next, a metal film 3 of metal Cr is formed to a thickness of 400 Å by sputtering on this SiO ₂ thin plate, and a positive X-ray resist (silicone resin) relating to the resist 4 is formed to a thickness of 0.9 μm on this by a spin coating method. did. Next, the resist 4 was exposed using an X-ray exposure device to form 10 fine patterns of 1 μm lines and spaces. After removing the X-ray irradiation part with a developing solution of organic solvent, post-baking (130 ℃, 30
After that, the resist pattern 6 thus obtained was used as a mask to dry-etch SiO ₂ . This dry etching uses a parallel plate type dry etching device,
CHF ₃ was used as an etchant. Then Ce
_{(NO 3) 4 · 2NH 4} · NO 3, perchloric acid: 1000 ml was dissolved 42ml
Cr using an Cr etching solution consisting of an aqueous solution diluted to
The film was wet etched. This wet etching was performed at a liquid temperature of 25 ° C. for 10 minutes 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 fine grooves of 1 μm was formed on the SiO ₂ 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 that has been altered by dry etching can be easily removed, so that a finer pattern 8 that is finer and has a dimensional accuracy close to a rectangle can be obtained. In addition, since the metal film 3 is used to remove the resist residue 7, even when a substance having a high electrical insulation property is used as the substrate 1 in the lithography using an electron beam, it is possible to prevent There is also an advantage that a finer pattern 8 can be obtained without charging.

[Effects of the Invention] As described in detail above, according to the present invention, there is provided a method for forming a fine pattern capable of easily removing a resist residue and efficiently forming a fine pattern with excellent dimensional accuracy. can do.

[Brief description of drawings]

FIG. 1 is a pattern forming process diagram of a fine pattern forming method 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 fine pattern forming method by the lithographic method, and FIG. 4 is a pattern forming process diagram of another example. 1 ... Substrate, 2 ... Pattern forming thin film, 3 ... Metal film, 4 ... Resist, 6 ... Resist pattern, 7 ...
Resist residue, 8 ... Fine pattern.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Shigeru Sasaki 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa, Hitachi, Ltd., Institute of Industrial Science (56) Reference JP 62-150350 (JP, A) JP JP-A-56-79428 (JP, A) JP-A-59-136931 (JP, A) JP-A-64-2325 (JP, A) JP-A-54-30827 (JP, A) JP-A-1-302724 (JP , A)

Claims (1)

(57) [Claims] 1. A pattern forming thin film forming step of forming a pattern forming thin film on a substrate, and a metal film forming step of forming a metal film on the pattern forming thin film formed in the pattern forming thin film forming step. A resist coating step of coating a resist on the metal film formed in the metal film forming step, and an exposure / development step of cross-linking and developing the resist coated in the resist coating step by lithography to form a resist pattern. A dry etching step of forming a desired fine pattern on the metal film and the pattern forming thin film by dry etching using the resist pattern formed in the exposure / development step as a mask, and a desired fine pattern in the dry etching step. By wet-etching the metal film on the patterned thin film, the resist is formed together with the metal film. Method of forming a fine pattern, characterized in that it comprises a wet etching process to obtain a thin film residue is removed with a desired fine pattern.