JPH02271358A - Method for forming photoresist pattern - Google Patents

Abstract

PURPOSE:To form a perpendicular cross section of a photoresist pattern by forming an SOG oxidized film in a recessed part formed on the photoresist and etching the photoresist by using this film as a mask. CONSTITUTION:The wafer 1 is coated with the positive type photoresist 2, the resist 2 is prebaked, and a partial area 3 of the resist 2 is selectively exposed to ultraviolet rays and developed to form the recessed part on the resist 2. The whole surface of the resist 2 is coated with the SOG (spin on glass) oxidized film 4 and after it is baked, it is subjected to anisotropic dry etching until the unexposed area of the resist surface is disclosed, and the film 4 is left on the recessed part. The resist 2 is removed by anisotropic dry etching with O2 by using the left film 4 as the mask, thus permitting the resist pattern 2a perpendicular in the cross section to be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming a photoresist pattern in a photolithography process for manufacturing a semiconductor device.

[Conventional technology]

Conventionally, this type of photoresist pattern forming method has been described in the process diagrams of FIGS. 3(a), (b), and (e).
As shown in a), a photoresist 2 is applied to a desired thickness on a silicon wafer 1, and after prebaking for 1 to 2 minutes in a nitrogen atmosphere at 90 to 100°C,
As shown in FIG. 3, when the exposure area 3 is irradiated with UV light such as G-line using a photomask using an alignment exposure machine, the positive photoresist becomes alkali-soluble.

Next, development is performed for 60 to 80 seconds with a tetramethyl hydroxide aqueous solution, which is a developer for positive photoresists, to form a photoresist pattern 2a as shown in FIG. In order to improve the adhesion to silicon oxide films and the like, a boss bake was performed at 130 to 140° C. for 20 to 40 minutes, and was used as a mask when processing the wafer.

[Problem to be solved by the invention]

The conventional method of forming a photoresist pattern described above is as follows:
The amount of UV light irradiated during exposure gradually decreases from near the photoresist surface to the bottom of the photoresist, and the energy that makes the positive photoresist soluble decreases, as shown in Figure 3(e). Resist pattern 2a
has a trapezoidal cross-sectional shape, which has the disadvantage of poor dimensional controllability.

[Means to solve the problem]

The present invention involves the steps of coating a positive photoresist on a wafer, prebaking, selectively exposing the upper layer of the photoresist to L7V light, and developing the photoresist with a developer for positive photoresist. A step of forming a recess on a photoresist, a step of spin-coating and baking SOG on this photoresist after development, and a step of spinning and baking this SOG.
A step of anisotropic dry etching the oxide film until the surface of the unexposed portion of the photoresist is exposed, and a step of exposing the unexposed portion of the photoresist to the wafer surface using the SOG oxide film remaining in the recessed portion after development as a mask. This is a method for forming a photoresist pattern, including a step of anisotropic dry etching at 0□.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIGS. 1(a) to <g) are process diagrams showing a first embodiment of the present invention. As shown in FIG. 4A, a positive photoresist 2 is applied onto a wafer 1 and prebaked at 90 to +00° C. for 1 to 2 minutes. Next, as shown in FIG.
The exposed areas 3 of the photoresist 2 are selectively exposed to light.

When the exposed photoresist 2 is developed with a positive photoresist developer, a pattern of concave portions is formed in the upper layer of the photoresist 2, as shown in FIG. 3(C). When 5OG (Spin On Glass) oxidized pIA4 is spin-coated on this pattern and beta-treated at 200 to 300° C. for 60 minutes, the result is as shown in the same figure (d).

Normally, when the SOG oxide film 4 is spin-coated, it tends to be thicker on the four parts, so in the case of FIG. It will be thicker than 4.

Next, this SOG oxide film 4 is subjected to anisotropic dry etching until the unexposed portions of the surface of the photoresist 2 are exposed, resulting in the result as shown in FIG. 6 (6).

Here, since the SOG oxide film 4 on the concave pattern is thicker than the SOG oxide film 4 on the photoresist 2 on the unexposed part, the SOG oxide film 4 on the photoresist on the unexposed part is anisotropically dry. Even if it is removed by etching, the SOG oxide film 4 on the concave pattern remains.

Next, using the SOG oxide film 4 on the remaining concave pattern as shown in FIG. remains.

Then, the SOG oxide film 4 on the photoresist pattern 2a is removed by anisotropic dry etching.
A photoresist pattern 2a having a vertical cross-sectional shape as shown in g) can be formed.

FIGS. 2(a) to 2(g) are process diagrams showing the second embodiment of the present invention. As shown in FIG. After prebaking the photoresist 2 at 90 to 100°C for 1 to 2 minutes, the exposure area 3 is selectively exposed to UV light to the extent that the upper layer of the photoresist 2 is exposed, as shown in FIG. However, when the film is developed with a developer, a recessed portion is formed as shown in FIG.

Next, as shown in the same figure (d), SO is applied on the photoresist 2.
G oxide film 4 is spin-coated and baked at 200 to 300°C for 60 minutes. Then, anisotropic dry etching is performed on the SOG oxide film 4 until the surface of the photoresist 2 in the unexposed area is exposed, and as shown in FIG. remain.

Next, using this SOG oxidation M4 as a mask, anisotropic dry etching is performed on the photoresist 2 at 02 until the surface of the wafer 1 is exposed, leaving a photoresist pattern 2a as shown in FIG. When the SOG oxide film 4 on the photoresist 2 is removed by anisotropic dry etching, a photoresist pattern 2a having a vertical cross-sectional shape as shown in FIG. 2(g) can be formed.

This embodiment has the advantage that even if a thick layer of photoresist is applied to flatten a step on a wafer, the dimensional difference in the photoresist pattern can be reduced regardless of whether it is above or below the step.

〔Effect of the invention〕

As explained above, in the present invention, a recess is formed on a photoresist coated on a wafer, and the photoresist is anisotropically dry etched with 02 using the SOG#I film remaining on the recess pattern as a mask. Since the cross section of the photoresist pattern can be formed vertically, dimensional changes in the photoresist pattern are reduced and dimensional controllability is improved.

[Brief explanation of drawings]

FIGS. 1(a) to (g) are process diagrams showing the first embodiment of the present invention, FIGS. 2(a) to (g) are process diagrams showing the second embodiment of the present invention, and FIGS. Figures (a), (b), and (c) are process diagrams showing a conventional method for forming a photoresist pattern. 1... Wafer, 2... Photoresist, 2a.
... Photoresist pattern, 3... Exposure area, 4.
...SOG oxide film.

Claims (1)

[Claims] A process of coating a positive photoresist on the wafer, and after prebaking, selectively exposing the upper layer of the photoresist to UV light to the extent that it is exposed, developing with a positive photoresist developer, and applying the photoresist onto the wafer. After the process of forming the recesses and the development, SOG is applied on this photoresist.
a step of spin-coating and baking the SOG oxide film; a step of anisotropic dry etching the SOG oxide film until the surface of the unexposed portion of the photoresist is exposed; A method for forming a photoresist pattern, comprising the step of anisotropic dry etching an unexposed portion of the photoresist with O_2 until the surface of the wafer is exposed.