JPH02118653A - Process for forming fine pattern using two-layered photoresist - Google Patents

Abstract

PURPOSE:To form a minutely formed pattern having perpendicular sectional shape by irradiating a whole surface of a positive photoresist as first layer with ultraviolet rays, coating the surface with a positive photoresist for a second layer, and irradiating the second layer selectively with ultraviolet rays through a photomask. CONSTITUTION:An alkali-soluble positive photoresist 4 is obtd. by irradiating a substrate 1 coated with a positive photoresist for a first layer with parallel ultraviolet rays uniformly for a short time. Then, a positive photoresist 5 for a second layer is coated to ca.1/2 of a desired film thickness so as to make the surface of the second layer of the positive photoresist 5 flat, and the photoresist 5 is prebaked. The area of the positive photoresist is converted to an alkali-soluble area 8 when the positive photoresist is irradiated with UV rays 6 such as g-line, etc. through a photomask to ca.3/4 degree of irradiation executed usually for a single layered resist. In this stage, the photoresist can be made selectively soluble sufficiently with a small dose of radiation applied to the first layer. Thus, a vertical sectional shape of the positive photoresist for the first layer is formed, and the photoresist is formed more minutely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing semiconductor devices and the like, and particularly to a method for forming fine patterns in a photolithography process.

[Conventional Technique vFi] Conventionally, in this type of photolithography process, a fine pattern formation method involves forming a high-pitched pattern on a silicon substrate (or silicon oxide film) 1, as shown in FIGS. 3(a) to (C). Resolution of positive photoresist 13 is usually 1iJ! After coating to a desired film thickness of 11 or more and prebaking for 1 to 2 minutes in a nitrogen or air atmosphere at 90 to 100°C (Fig.
a)) When a photomask (or redicle) 7 is irradiated with ultraviolet light (hereinafter also referred to as UV light) 6 using a photomask (or redicle) 7 as a mask, the positive photoresist becomes alkali-soluble (the Figure 3(b)). Next, a fine photoresist pattern is formed by flattening for 60 seconds with an aqueous solution of tetramethylammonium hydroxide, which is a positive resist developer. The process is carried out at 130 to 140 DEG C. for 20 to 40 minutes to form a mask for microfabrication of the silicon substrate (silicon oxide film) 1 (FIG. 3(C)).

[Problem to be solved by the invention]

The conventional fine pattern forming method described above uses a single layer of high-resolution positive photoresist, so when the photoresist film thickness becomes thicker than one layer, UV rays increase from near the photoresist surface to the bottom of the photoresist. As the irradiation area of the light beam gradually attenuates, the energy that makes the positive resist soluble in alkali also decreases, and the cross-sectional shape of the photoresist becomes tapered as shown in Figure 3 (C), which improves the controllability of dimensions. It has the disadvantage that it has poor performance and inhibits miniaturization. 1 In addition, when the substrate has a step, as in the conventional example shown in FIG. In the case of opening, there is a drawback that the machining dimensions are different between the opening 15 and the opening 16, which reduces the machining accuracy.

[Means to solve the problem]

The method for forming a fine pattern using the two-layer photoresist of the present invention is as follows: No. 11! a step of applying a positive photoresist to about half the desired film thickness; a step of prebaking the first layer positive photoresist and then irradiating the entire surface with ultraviolet rays; coating the second layer positive photoresist on the first layer positive photoresist so that the combined film thickness with the 21i positive photoresist becomes the desired film thickness; and the second layer positive photoresist. The method includes a step of selectively irradiating the positive photoresist with ultraviolet rays through a photomask or the like, and a step of developing it using a developer for positive photoresists.

[Effect]

After irradiating the entire surface of the 118th positive photoresist with ultraviolet rays and then applying a second layer of positive photoresist,
By selectively irradiating the photoresist with ultraviolet rays, the positive resist can be made alkali-soluble even if the ultraviolet energy required for pattern formation is small, thereby forming the cross section of the first layer of positive photoresist vertically. be able to.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1(a) to 1(e) are longitudinal cross-sectional views of an embodiment of a method for forming a fine pattern using the two-layer photoresist of the present invention.

In FIG. 1(a), a silicon substrate (or silicon oxide film) 1 has an uneven cross section with a step difference of about 0.37 m and a width of about 1 to 2 lines on its surface. The first positive-type photoresist 2 is a photoresist whose main component is novolac resin, and the rotation speed and viscosity are selected and applied so that the film thickness is about 0.5 tm, which is about half of the desired film thickness. After coating, the first M photoresist is coated with the substrate 1 at 90~
Prebaking is performed for 1 to 2 minutes in a nitrogen or air gas atmosphere at 100° C. to evaporate the solvent in the first M photoresist and stabilize the photoresist film.

Next, as shown in FIG. 1(b), the substrate coated with the first positive type photoresist is uniformly irradiated for a short time using an exposure machine using parallel ultraviolet rays. As a result, an alkali-soluble positive photoresist 4 is obtained.

Next, as shown in FIG. 1(C), a second positive type photoresist 5 is coated in a 0.5-inch pattern, which is about half of the desired film thickness, to form a second layer of positive photoresist 5 without being affected by the unevenness of the substrate. The mold photoresist is applied so that the surface becomes flat, and prebaked under the same conditions as the 11th I positive resist.

Next, as shown in FIG. 1(d), using a photomask (or reticle) 7 as a mask, UV light such as q-rays is applied to a single-layer resist with a thickness of 1 to 1 using a stepper or other eyelid exposure device. After irradiation of about 374° C., the portions of the positive photoresist selectively irradiated with UV light become alkali-soluble regions 8, and the unirradiated portions remain insoluble. At this time, the amount of energy given to the first layer is only a small amount because the positive resist is starting to become soluble due to UV irradiation on the entire surface. If the total energy of the V-light irradiation reaches a predetermined amount, it is possible to sufficiently make the photoresist selectively soluble.

Next, as shown in FIG. 1 (0), the first and second layers are developed for about 60 seconds using a tetrameglyammonium hydroxide aqueous solution, which is a developer for positive resists. A fine pattern consisting of resist 10.9 is obtained.

FIG. 2 is a longitudinal sectional view of another embodiment of the invention.

The first layer positive type resist film A1 to resist 2 is deposited on the silicon substrate or silicon oxide film 1 at a height of 0.3 am to 0.2 tt.
A film thickness of approximately 0.5 mm (approximately x+) is applied and prebaked (FIG. 2(a)). Next, the entire surface of the first layer of positive photoresist is irradiated with UV light, and developed using a developer for positive resist to obtain a height comparable to that of the convex portion of the silicon substrate film (see Figure 2). (b)).

Next, using the 02 plasma processing method, the protrusions of the substrate are removed to the extent that they are washed away, and the main surface of the substrate and the photoresist 11 are removed.
The surface is flattened (FIG. 2(C)). Next, the second layer positive photoresist 5 is coated with a desired film thickness of approximately 1.0/II.
When R is applied, the film thickness of the 211th positive photoresist 5 becomes uniform regardless of the unevenness of the substrate, and the dimensions of the openings in the substrate recesses and substrate projections after development are the same at each opening. The dimensions are the same (Fig. 2 (d)
)). Next, as shown in FIG. 2(e), ultraviolet rays 6 are irradiated through the mask 7 and development is performed.
A fine pattern made of resist 10.12 as shown in f) is obtained. In this embodiment, since the dimensions of each opening can be made equal, there is an advantage that miniaturization can be achieved compared to the conventional method.

〔Effect of the invention〕

As explained above, in the present invention, the entire surface of the first layer positive photoresist is irradiated with ultraviolet rays, the second layer positive photoresist is applied, and the UV rays are selectively irradiated using a photomask. , the positive photoresist can be made alkali-soluble even if the ultraviolet energy required for pattern formation is less than conventional ones, and the cross section of the positive photoresist after development has the effect of forming a pattern more vertically than conventional methods1. As a result, the first-layer positive photoresist section in the cross section of the positive photoresist has a vertical shape, which improves the dimensional accuracy of the bottom of the photoresist, and also enables the formation of finer patterns. be.

[Brief explanation of the drawing]

FIGS. 1(a) to (e) are longitudinal cross-sectional views of an embodiment of a method for forming a fine pattern using the two-layer regimen of the present invention, and FIGS. FIGS. 3(a) to 3(C) are longitudinal sectional views of the conventional example. 1... silicon substrate (or silicon oxide film), 2...
...First layer positive photoresist, 3...Full surface UV rays, 4...Alkali-soluble positive photoresist, 5...
・Second layer positive type resist (~, 6...UV
Light beam, 7... Photomask (or reticle), 8...
Selective alkali-soluble region, 9...Developer box single layer positive photoresist, 10...
・Two-layer positive photoresist in cylinder after development, 11...Positive photoresist flattened with the substrate convex portion, 12...Substrate after development, convexity and flattened photoresist, 13...111 Layer high resolution positive photoresist, 1
4...Developing machine single layer positive photoresist, 15...
Substrate recess opening; 16... Substrate protrusion opening;

Claims (1)

[Claims] 1. A step of applying a first layer positive photoresist to about half the desired film thickness; and a step of prebaking the first layer positive photoresist and then irradiating the entire surface with ultraviolet rays. , the second layer positive photoresist is added to the first layer positive photoresist so that the combined film thickness of the first layer positive photoresist and the second layer positive photoresist becomes the desired film thickness. a step of selectively irradiating the second layer positive photoresist with ultraviolet rays through a photomask etc., and a step of developing using a developer for positive photoresists. A method for forming fine patterns using photoresist.