KR0172549B1 - Method for forming a photoresist pattern - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a lithography technique used in a semiconductor device manufacturing process, in which a resist pattern is formed to solve the collapse of a resist pattern due to an increase in aspect ratio, Washing the resist pattern with ultrapure water at a high temperature to cure the resist pattern, and then drying the resist pattern using a spin dry.

Description

Method for forming photoresist pattern of semiconductor device

FIGS. 1 to 3 are cross-sectional views showing a step of forming a photoresist pattern by a conventional method.

FIGS. 4 to 7 are cross-sectional views showing a step of forming a photoresist pattern according to the present invention. FIG.

FIG. 8 is a cross-sectional view showing a state before a photoresist pattern is formed on a wafer, followed by continuous ultra-pure water washing, and a spin-dry process. FIG.

DESCRIPTION OF THE REFERENCE NUMERALS

1: Wafer 2: Photoresist

3: mask 4: light

5: Ultra-pure water at room temperature 6: Ultra-pure water at high temperature

2 ': Photoresist pattern

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithography technique used in a manufacturing process of a semiconductor device, and more particularly, to a resist pattern forming method capable of eliminating a collapse of a resist pattern generated when an aspect ratio of a resist pattern is increased .

The lithography process of a semiconductor device is essentially used in a process of forming a pattern. That is, a resist is applied to a top surface of a layer to be patterned, and exposure and development processes are performed using a mask having a pattern, And the lower layer is etched using the resist pattern as a mask to form a pattern of the lower layer.

However, as the semiconductor device is highly integrated, the spacing of the resist pattern is minimized, and the resist pattern easily collapses. Such a collapse phenomenon of the resist pattern can be largely divided into two.

The first is that the adhesion between the resist pattern and the wafer substrate is weak and the resist pattern is peeled from the wafer substrate. Second, the resist pattern itself is not physically rigid, so that the pattern is warped or broken. The resist pattern collapse phenomenon becomes more problematic as the degree of integration of the semiconductor device becomes higher because the phenomenon of pattern collapse becomes worse as the aspect ratio of the resist pattern becomes larger and the interval between patterns becomes narrower .

The collapse phenomenon of the resist pattern occurs during the development process. The developing process is firstly carried out with a developing solution, followed by washing with deionized water, and then the wafer is rotated at a high speed to dry the resist pattern. At the moment when the ultrapure water washing is finished and the spin dry process starts, the resist pattern is collapsed . The cause of the collapse of the resist pattern is that the ultrapure water filled between the patterns acts on the center of the gap between the pattern and the pattern at the instant of sudden evaporation as the spin-dry process starts, and as a result, the resist pattern collapses do.

The magnitude of the pressure applied to the center of the gap between the pattern and the pattern is inversely proportional to the surface tension of the ultrapure water solution and the aspect ratio of the pattern and is inversely proportional to the radius of curvature formed at the surface of the ultrapure water between the patterns.

This can be expressed as follows. (See also Fig. 7)

The small radius of curvature in the above equation means that the interval between the patterns is narrow, and the small pattern width means that the minimum line width of the semiconductor device is small. Aspect ratio = pattern height / pattern width.

Particularly, in a mask process for manufacturing capacitors of a dynamic random access memory (DRAM) device among the semiconductor devices, the collapse of the resist pattern is a serious problem.

This is because the shape of the pattern on the mask for manufacturing the capacitor is like an island and the size of the pattern is the smallest so that the contact area with the wafer substrate is small.

On the other hand, when the pattern shape on the mask in the lithography process is an island shape, it is advantageous in terms of pattern formation to use a negative resist rather than a positive resist. A negative resist is used in the mask process for manufacturing a capacitor, and a pattern collapse phenomenon occurs in the negative resist as well as the positive resist.

However, the negative resist has various advantages over the positive resist in terms of application of a technique for preventing pattern collapse after the pattern formation is completed according to the principle of pattern formation.

An object of the present invention is to provide a resist preparation method for curing a resist pattern by washing the resist pattern with ultrapure water at a high temperature so as to prevent the resist pattern from collapsing in a spin dry process.

According to an aspect of the present invention, there is provided a method of manufacturing a photoresist, including the steps of: applying a photoresist on a wafer; exposing the photoresist using a mask; Forming a photoresist pattern on the photoresist pattern by a photoresist pattern; first cleaning the photoresist pattern with ultrapure water at room temperature; secondly cleaning the photoresist pattern with ultrapure water at a high temperature to cure the photoresist pattern; And then completing the photoresist pattern by evaporating the ultrapure water by rotating the finished photoresist pattern at high speed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIGS. 1 to 3 are cross-sectional views showing a step of forming a photoresist pattern according to the prior art.

1 is a cross-sectional view showing that a negative photoresist 2 is coated on a wafer 1, soft baking is performed, and then a mask 3 is coated to expose the wafer with light 4. [

For reference, the photoresist 2 is applied in a thickness of 1.0 탆, soft baked on a hot plate at a temperature of 90 캜 for about 90 seconds, then covered with a mask and irradiated with light using an exposure apparatus.

FIG. 2 is a schematic view of the photoresist pattern 2 (FIG. 2) after a post exposure bake (Post Exposure Bake) was performed on a hot plate at a temperature of 110 ° C. for about 90 seconds, followed by TMAH (Tetra Methyl Ammonium Hydroxide) ') And is cleaned using ultrapure water 5 at room temperature.

3 is a cross-sectional view showing the completion of the development process by drying the wafer 1 by the spin dry method. At the moment when the ultrapure water solution 5 filled between the photoresist patterns 2 'is completely evaporated, The photoresist pattern 2 'is collapsed when the photoresist pattern 2' is not physically stiff.

8 shows a state in which a photoresist is coated on a wafer 1, exposed, and subjected to a TMAH treatment to form a pattern 2 '. Then, the ultrapure water 5 is continuously washed, A phenomenon occurs in which the photoresist pattern 2 'is collapsed or cut at the moment when the solution of the ultrapure water 5 filled between the two photoresist patterns 2' is evaporated as shown in FIG. do. That is, when the intensity of the input acting toward the center of the gap between the photoresist patterns 2 'is greater than the adhesion force between the photoresist pattern 2' and the wafer 1, the photoresist pattern 2 ' When the photoresist pattern 2 'itself is weak enough not to overcome the pressure, it is bent or collapsed.

FIGS. 4 to 7 are cross-sectional views showing a photoresist pattern formed according to an embodiment of the present invention.

4, the photoresist 2 is applied on the wafer 1 to a thickness of 1.0 탆, soft baked on a hot plate at a temperature of 90 캜 for 90 seconds, and then covered with a mask 3 to form a light 4 FIG. 5 is a cross-sectional view showing exposure.

For reference, the photoresist 2 is negatively applied, but can be applied positively, and can be applied to all resists regardless of the type of light source used in the exposure process.

5, a post exposure bake is performed on a hot plate at a temperature of 110 ° C. for about 90 seconds and then treated with TMAH (Tetra Methyl Ammonium Hydroxide) for about 60 seconds to form a photoresist pattern 2 ') And is subjected to primary washing with ultra-pure water 5 at room temperature.

FIG. 6 shows that the photoresist pattern 2 'is cured by performing second washing with fine ultrapure water 6 at 50-100 ° C. before washing with ultrapure water 5 at room temperature and before spin-drying Sectional view.

For reference, the degree to which the photoresist is cured is promoted as the temperature of the ultrapure water is higher. However, at a certain temperature or higher, since the photoresist is thermally deformed to adhere the resist patterns to each other or change its shape, Should be.

7 shows a state in which the photoresist pattern 2 'is finally removed by evaporating the ultrapure water 6 by spin-drying the wafer at 3000 to 4000 rpm for about 10 to 20 seconds after completion of the photoresist curing by the high-temperature ultrapure water 6, Fig.

For reference, since the photoresist pattern 2 'is already formed in a cured state, the photoresist pattern 2' is not deformed even when a strong pressure is applied by the spin dry.

As described above, according to the present invention, in a process of forming a pattern using a negative photoresist, when a negative photoresist is cured (crosslinked or hardened) when heat energy is received, It is possible to solve the problem of bending or collapsing.

The yield of the semiconductor device is improved because a short phenomenon between the patterns that occurs when the conductive film of the lower layer is etched in the state where the resist pattern is collapsed is prevented.

Claims (7)

A method of manufacturing a photoresist, comprising the steps of: applying a photoresist on a wafer; exposing the photoresist using a mask; developing the exposed photoresist in a developer to form a photoresist pattern; A step of washing the photoresist pattern with ultrapure water at a room temperature, a step of secondly cleaning the photoresist pattern with ultrapure water at a high temperature to cure the photoresist pattern, a step of rotating the photoresist pattern after the curing process at a high speed And evaporating the ultrapure water to complete the photoresist pattern. The method of claim 1, wherein the photoresist pattern is washed in a super-pure water solution at 50 to 100 캜 for 10 to 20 seconds to cure the photoresist pattern. The method of claim 1, wherein the photoresist comprises any kind of photoresist regardless of the wavelength of the light source used in the exposure process. The method for forming a photoresist pattern according to claim 1, wherein the photoresist is negative. The method for forming a photoresist pattern of a semiconductor device according to claim 1, wherein the photoresist is applied, followed by soft baking for 90 seconds at a temperature of 90 캜 on a hot plate. The method according to claim 1, wherein the photoresist is subjected to a post exposure bake on a hot plate at a temperature of 110 캜 for about 90 seconds after the exposure process. Way. The method of claim 1, wherein the developer is TMAN (Tetra Methyl Ammonium Hydroxide).