JPH02183255A - Pattern forming method - Google Patents

Abstract

PURPOSE:To form an upper layer resist pattern which is vertical in profile and has no scum by executing a descum treatment after patterning. CONSTITUTION:The desired CMS (chrolo-methyl-stylene) resist pattern 4 is formed by exposing a CMS film 3 by using an excimer layer and developing the film and thereafter, the descum treatment is executed. Unnecessary org. matter is, therefore, removed and the CMS resist pattern 4 is trimmed by which the good pattern having no scum is obtd.; in addition, the crosslinking in the surface part of the CMS resist pattern 4 is progressed by the UV light radiated during discharge. Further, the crosslinking of the CMS resist pattern 4 is progressed by executing a heating and baking treatment to increase the absorption coefft. of light. A PMCI (polymethyl-glutarimide) film 2 is exposed over the entire surface by using the CMS resist pattern 4 as a mask and thereafter, the part where the PMGI film 2 is photodecomposed is dissolved away by an alkaline developing soln. The fine patterns of the two-layered resists are accurately formed in this way.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for forming fine patterns.

[Conventional technology]

Conventionally, as an example of this type of pattern forming method, there is a method described in "Autumn 1985 Obi Proceedings, p. 431, 18P-F-10J.
There is something to be disclosed. This is PCM (Por-table C) for excimer laser lithography.
Onfors+able Mask) method is studied to form a resist pattern with a high aspect ratio.

That is, using RD200ON (manufactured by Hitachi Chemical) as the upper layer and PMCI (manufactured by Silapray) as the lower layer, the upper layer RD200ON was exposed to an excimer laser with a wavelength of 248n+m.
After forming a pattern by exposing and developing with an exposure machine, the lower layer PMCI is exposed to Xe-If using the upper layer resist as a mask.
A two-layer resist pattern is formed by exposing and developing the entire surface using a G-light. In this case, the upper layer (7) r? D
200ON is l1eep UV v4? 'Because it has strong absorption properties, it serves as a good adhesion mask when exposing the entire lower layer to light.

[Problem to be solved by the invention]

However, in the conventional pattern forming method described above, the negative resist used for the upper layer has an RD2000N of
Since the absorption coefficient is too large for light with short wavelengths such as 193n* and 248nrs, the crosslinking density differs between the upper and lower parts of the upper resist. Therefore, there was a problem that undercutting occurred and a good upper layer resist pattern could not be obtained.

Furthermore, since two types of light sources are required, one for upper N exposure and the other for lower layer exposure, there is a problem in that the cost is high.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a pattern forming method capable of obtaining a good resist pattern at low cost.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention includes the steps of: forming a flat lower layer resist on a substrate; forming an upper layer resist made of a material having high transmittance to exposure light on the lower layer resist; After that, the upper layer resist is exposed and
A process of developing to form an upper resist pattern, and then shaping the upper resist pattern by descum treatment, crosslinking the surface of the upper resist pattern, and then heat-treating it to increase the transmittance to exposure light. The method includes a step of reducing the size, and then a step of patterning the lower resist by exposing and developing the lower resist using the upper resist pattern as a mask.

[For production]

In the present invention, since the upper resist layer is made of a material with high transmittance to exposure light, a uniform crosslinking density can be obtained.
An upper resist pattern with a vertical profile is obtained. Furthermore, since the upper resist pattern is subjected to descum processing, a good pattern without scum is obtained. Furthermore, since heat treatment is performed after the descum treatment, the crosslinking density of the upper resist pattern further increases, and the transmittance to exposure light decreases. In addition, the exposure process for the upper and lower resist layers is performed using the same apparatus.

〔Example〕

An example of the method of the present invention is shown in FIG. 1 as a process diagram and as shown in FIG.
The description will be given by showing a characteristic diagram of wavelength light and its transmittance in the CMS.

First, as shown in FIG. 1(a), PMCI (poly-+5ethyl
-glutartIlide) II! 2 is spin-coated to a thickness of 1 to 1.5 nm at a beta temperature of about 200 to 250°C. Next, CMS (chloro-netyl-5ty) is applied as an upper layer resist on the PMGT film 2.
lene) Film 3 is spin-coated to a thickness of 0.5 to 0.6 μm.

Thereafter, as shown in FIG. 1b), as a light source,
Using an 8nrs excimer laser, the energy density is 5
The above 0MS film 3 is exposed and developed under the conditions of ~10 mJ/- pulse and irradiation amount of 100 mJ/cd to obtain the desired 0MS.
A resist pattern 4 is formed. By the way, as shown in FIG. 2, it can be seen that the transmittance of this 0MS film 3 for the wavelength of light is large before exposure and decreases after exposure. Under the exposure conditions, the absorption coefficient of light before exposure is 1.77μ
m1 increases to 2.23 pm-' after exposure. However, this level of absorption coefficient is not sufficient to use the OMS resist pattern 4 as an exposure mask for the PMGI film 2 in the next step. Therefore, it is necessary to further increase the light absorption coefficient of the resist pattern 4 and reduce the light transmittance.

Therefore, as shown in Figure 1, 02 flow rate 11005
CC, RF power 100W and pressure l Q Qtsto
In this way, unnecessary organic substances are removed, the 0MS resist pattern 4 is shaped into a good pattern without scum, and it is also removed by the radiation ultraviolet light (about 20 On-) during discharge. Crosslinking of the surface portion of the resist pattern 4 proceeds, and after the descum treatment, a heating beta treatment is performed at a beta temperature of 200 to 250° C. for 5 minutes to form the 0MS resist pattern 4.
This further promotes crosslinking and increases the light absorption coefficient. Incidentally, the absorption coefficient at this time increases to 5.474 Im-'. Furthermore, since the surface of the resist pattern 4 is crosslinked, a flow state due to heat treatment in the next step can be avoided.

Next, Figure 1! d>, an excimer laser with a wavelength of 248 r++s was used as the light source, the energy density was 5 to 10 mJ/c+a pulse, and the irradiation amount was 1
Under conditions of ~5 J/cIJ, the entire surface of the PMCI film 2 is exposed using the OMS resist pattern 4 as a mask. In this case, since the resist pattern 4 absorbs the exposure light, the portion directly under the resist pattern 4 excluding the PMGI film 2 is photodecomposed.

After that, as shown in FIG.
The photodecomposed portion is dissolved and removed using an alkaline developer, and a fine pattern of the two-layer resist is formed with high precision.

〔Effect of the invention〕

As described above, according to the present invention, the upper resist has a high transmittance to exposure light and is subjected to descum treatment after being patterned, so that a good upper resist pattern with a vertical profile and no scum can be formed. Further, since the heat treatment is performed after the descum treatment, the crosslinking density of the upper resist pattern increases and the transmittance to exposure light decreases.

Therefore, the above-mentioned problems can be solved with unique effects such as not only the lower resist layer can be exposed and developed with high precision, but also the upper and lower resist layers can be exposed with the same device, reducing costs and improving work efficiency.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the method of the present invention, where FIG. 1 is a process diagram and FIG. 2 is a wavelength light-transmittance characteristic diagram in CMS. l...Substrate, 2...PMG I film, 3...0MS
Film, 4...0MS resist pattern. Fig. 1 CMSI Σ anti-2 long light - ΔtMq system) / Ren diagram 2
figure

Claims (1)

[Scope of Claims] A step of forming a flat lower layer resist on a substrate, a step of forming an upper layer resist made of a material having a high transmittance to exposure light on the lower layer resist, and then a step of forming the upper layer resist on the substrate. Next, the upper resist pattern is shaped by descum processing, and the surface of the upper resist pattern is crosslinked, and then heat treated to resist exposure light. A pattern forming method comprising the steps of: reducing transmittance; and then patterning the lower resist by exposing and developing the lower resist using the upper resist pattern as a mask.