JPH02238457A - Formation of thick-film resist pattern - Google Patents

Abstract

PURPOSE:To form the photoresist patterns which are perpendicular in sectional shape and has the width uniform in a film thickness direction with good dimensional controllability by applying the high-sensitivity positive type photoresist of a 1st layer on a substrate and applying the positive type photoresist of a 2nd layer of the sensitivity lower than the sensitivity of the 1st-layer photoresist thereon, then selectively irradiating the photoresists with UV rays. CONSTITUTION:The photoresist 2 of the 1st layer consisting of the high-sensitivity positive type photoresist is applied on the substrate and is prebaked. The photoresist of the 2nd layer 3 consisting of the positive type photoresist having the sensitivity lower than the sensitivity of the photoresist 2 of the 1st layer is applied thereon and is prebaked. The photoresist 2 of the 1st layer is then subjected to exposing of required patterns with the UV light form the surface side of the photoresist 2 of the 2nd layer; thereafter, the photoresists 2, 3 of the 1st layer and the 2nd layer are subjected to a development processing with a developing soln. The increasing of the size of the surface side and the decreasing of the size on the bottom side by a difference in the sensitivity of the photoresists 2, 3 of the 1st layer and the 2nd layer are eliminated at this time. The photoresist patterns which are perpendicular to the sectional shape and have the good dimensional accuracy are formed in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming a thick film photoresist pattern in a photolithography process used in the manufacture of semiconductor devices. [Prior Art] Conventionally, in this type of thick film photoresist pattern forming method, a desired film of photoresist 2 is deposited on a silicon substrate (or silicon oxide film) 1 to be patterned, as shown in FIG. Apply a thick layer and pre-bake for 1 to 2 minutes in a nitrogen or air atmosphere at 90°C to 100°C. Then, a photomask or reticle is used as a mask to irradiate Uv light such as G-line using an alignment exposure device such as a stepper. This makes the positive photoresist alkali soluble.

Next, as shown in FIG. 3(b), when the photoresist 2 is developed for 60 to 80 seconds with a tetramethylammonium hydride oxide aqueous solution, which is a positive resist developer, the UV
The light irradiated portion is dissolved, and a pattern is formed using the remaining photoresist 2.

Note that the photoresist 2 after patterning was heated at 130°C to 140°C to improve adhesion to the silicon substrate 1, etc.
Post-bake for 20 to 40 minutes at °C. (Problems to be Solved by the Invention) The conventional method for forming a photoresist pattern described above is as follows:
When the film thickness of the photoresist 2 increases to 2 μm or more, as shown in FIG. 3(a), the amount of UV light irradiation during exposure gradually decreases from the surface side of the photoresist toward the bottom surface of the photoresist, resulting in a positive photoresist. The energy required to make it soluble is also reduced. Therefore, when the photoresist 2 is developed, as shown in FIG. 3(b), the opening formed in the photoresist 2 has a tapered shape with a width narrower toward the bottom, and the manufacturing dimensions of the semiconductor device using photolithography technology. There is a problem that the controllability becomes worse.

An object of the present invention is to provide a method for forming a thick film photoresist pattern with improved dimensional controllability. [Means for Solving the Problems] The method for forming a thick film photoresist pattern of the present invention includes the steps of applying and prebaking a first layer of photoresist made of a high-strength positive photoresist, and applying the above-mentioned steps on the first layer of photoresist. A step of applying a second layer of photoresist made of a positive photoresist with lower sensitivity than the first layer of photoresist and pre-baking, and applying the first layer of photoresist from the surface side of the second layer of photoresist. The method includes the steps of: exposing the desired pattern to UV light of sufficient energy to render it soluble; and developing the first and second layers of photoresist with a developer.

[Effect]

In the method described above, the width dimension on the front side becomes large due to the difference in sensitivity between the first layer and the second layer of photoresist.
In addition, a photoresist pattern with a vertical cross-sectional shape and high dimensional accuracy can be formed without the width dimension being small on the bottom side.

〔Example〕

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

FIGS. 1A to 1C are vertical cross-sectional views showing a first embodiment of the present invention in the order of manufacturing steps.

First, as shown in the figure (a), a high-sensitivity positive photoresist 2 (sensitivity room'
/cvb'') to a desired film thickness of 172 mm, and pre-batered at 90-100°C for 1-2 minutes.

Next, as shown in the same figure (b), as a second layer, a positive photoresist 3 (
(sensitivity: 100 m'/cta" or more) and form the desired film thickness together with the first layer of photoresist 2. After that, pre-bater at 90 to 100° C. for 1 to 2 minutes. Then, The surface of the second layer of photoresist 2 is irradiated with UV light having an energy that can make the first layer of photoresist 2 soluble in a developer.At this time, the second layer of photoresist 3 is irradiated with Although the energy of the UV light is larger than that of the first layer, the sensitivity of the second layer of photoresist 2 is lower than that of the first layer of photoresist 2, so the second layer of photoresist 3 does not receive excessive irradiation energy. , the pattern width does not become thicker even after development.

Thereafter, when developing using a positive photoresist developer, the UV light irradiated portions of each of the first and second photoresists 2 and 3 are dissolved and the cross section is A photoresist pattern with a vertical shape can be formed.

FIGS. 2(a) to 2(d) are longitudinal sectional views showing a second embodiment of the present invention in the order of manufacturing steps.

First, as shown in FIG.
0 people) Apply. After blibeta, full exposure (100m
'/Cll'').

Next, as shown in FIG. 4B, a first layer of high-sensitivity positive type photoresist 2 is applied to a desired thickness of 172 mm and prebaked.

Thereafter, as shown in the same figure (C), a second layer of low-density positive photoresist 3 is applied thereon, and the desired film thickness is obtained by combining the base layer photoresist 4 and the first layer photoresist 2. shall be. After prebaking, UV light is selectively irradiated from the surface side of the second layer photoresist 3. This U
The V light irradiation is performed in the same manner as the Uv light irradiation in the first embodiment.

Thereafter, by developing with a positive photoresist developer, a photoresist pattern with a vertical cross-sectional shape is obtained as shown in FIG. 3(d).

At this time, with ordinary thick-film photoresists, sufficient light energy does not reach the bottom of the photoresist, and a thin scum may remain at the bottom of the photoresist after development. However, in this embodiment, the entire surface of the underlayer photoresist 4 is exposed in advance to make it sufficiently soluble in the developer, so even if scum occurs in the first layer photoresist 2, the underlayer photoresist 4 is exposed during development. It has the advantage that it is removed together with the photoresist 4 and no scum remains even with thick photoresist.

[Effects of the Invention] As explained above, in the present invention, a first layer of high-sensitivity positive photoresist is coated, and a second layer of positive photoresist having lower sensitivity than the first layer photoresist is applied thereon. After coating, UV irradiation is performed selectively, so even if the energy of the UV light irradiated to the second layer of low-sensitivity positive photoresist is greater than that of the first layer, the sensitivity of the second layer of photoresist remains unchanged. Because of the low irradiation energy, the second layer of photoresist is not irradiated with too much energy, which has the effect of forming a photoresist pattern with a vertical cross-sectional shape and a uniform width in the film thickness direction with good dimensional control.

[Brief explanation of drawings]

FIGS. 1(a) to (C) are vertical sectional views showing a first embodiment of the present invention in the order of manufacturing steps, and FIGS. 2(a) to (d) show a second embodiment of the present invention in the order of manufacturing steps. Longitudinal sectional view, Figure 3 (a
) and (b) are vertical cross-sectional views showing a conventional photoresist pattern forming method in the order of steps. DESCRIPTION OF SYMBOLS 1... Silicon substrate, 2... First layer photoresist (high sensitivity positive photoresist), 3... Second layer photoresist (low sensitivity positive photoresist), 4.
... Base layer photoresist (thin film positive photoresist). Figure 1 Figure 2 & I! lα尤IJJJJUV尤UVfirst appearance

Claims (1)

[Claims] 1. Applying and pre-baking a first layer of photoresist made of a high-sensitivity positive photoresist, and then applying a second layer of positive photoresist with lower sensitivity than the first layer of photoresist. applying and pre-baking a photoresist, and exposing the second layer of photoresist from the surface side with UV light of sufficient energy to make the first layer of photoresist soluble; A method for forming a thick film photoresist pattern, comprising the step of developing the first layer and the second layer of photoresist with a developer.