JPH03223760A - Resist pattern forming method - Google Patents

Abstract

PURPOSE:To make improvement in the contrast of exposing light to a 1st resist by subjecting the 1st resist to exposing via a contrast increasing layer with a patterned 2nd resist as a mask. CONSTITUTION:After the lower layer resist 2 is formed by spin coating on a substrate 1, the contrast increasing layer 10 consisting of a full-surface light fadable material is formed by spin coating on the lower layer resist 2. The upper layer resist 3 is then formed by spin coating over the entire surface on the contrast increasing layer 10. Further, the this resist is irradiated with upper layer exposing light 5 via an exposing mask 4 and is then developed, by which the upper layer resist patterns 3a are formed. The contrast increasing layer 10 is thereafter irradiated with lower layer exposing light 6 via the upper layer resist patterns 3a. The contrast of the exposing light to the 1st resist improves in this way even if the absorption of the exposing light in the 2nd resist is imperfect.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a resist pattern forming method, and particularly to a resist pattern forming method in a multilayer resist process.

[Conventional technology]

As semiconductor devices become more highly integrated, there is a demand for finer circuit patterns.In order to meet this demand, resist patterns that serve as masks for processing the underlying layer are also made finer in the circuit pattern manufacturing process. is now required. Therefore, a multilayer resist process has conventionally been used in which a resist film coated in multiple layers is used to improve the processed shape of the resist. One type of this multilayer resist process is a method called a portable conformal mask method (hereinafter referred to as PCM method). 2nd A
2A to 2E are cross-sectional process diagrams showing a conventional resist pattern forming method using the PCM method.

A lower resist 2 for planarization and patterning is formed on the substrate 1. Next, an upper layer cyst 3 is formed on the lower resist 2 to serve as a mask during exposure of the lower resist 2 to obtain a structure as shown in FIG. 2A.

Next, upper layer resist 3 is irradiated with upper layer exposure light 5 through exposure mask 4, and then developed to form upper layer resist pattern 3a as shown in FIG. 2B. The upper resist pattern 3a often has a trapezoidal shape as shown in FIG. 2B. This is based on the fact that the amount of exposure near the bottom of the upper resist 3 is smaller than near the surface.

Next, as shown in FIG. 2C, the upper resist pattern 3
Lower layer exposure light 6 is irradiated onto the lower resist 2 through a.

The upper resist pattern 3a has a property of absorbing the lower layer exposure light 6, and therefore, the upper resist pattern 3a serves as a mask when exposing the lower resist 2. At this time, since the upper resist pattern 3a is trapezoidal as described above, absorption of the lower layer exposure light 6 is incomplete on the side surfaces. As a result, the contrast of the optical image when the lower resist pattern 2 is exposed using the upper resist pattern 3a as a mask is 2D.
It becomes weaker as shown in the figure.

After development, a lower resist pattern 2a as shown in FIG. 2E is obtained.

[Problem to be solved by the invention]

Conventional resist pattern formation is performed in the above order, and since the upper resist pattern 3a, which serves as a mask for exposing the lower resist 2, is trapezoidal, the resist pattern 3a is formed in the lower resist pattern 2 through the upper resist pattern 3a. Absorption of the irradiated lower layer exposure light 6 becomes incomplete on the side surfaces of the upper layer resist pattern 3a, and the contrast of the optical image on the lower layer resist 2 decreases. There was a problem that I couldn't get it. This problem becomes even more serious when forming a fine resist pattern.

This invention was made in order to solve the above-mentioned problems, and it is a resist pattern forming method that can form a lower resist pattern with high precision by improving the contrast of the optical image during exposure of the lower resist. Aim to get the method.

[Means to solve the problem]

The resist pattern forming method according to the present invention includes a step of preparing a base layer, a step of forming a first resist on the entire surface of the base layer, and a step of forming a photobleachable material on the entire surface of the first resist. forming a second resist on the surface of the contrast enhancing layer; patterning the second resist into a predetermined pattern; and forming a second resist on the patterned second resist. The contrast enhancing layer and the first resist are exposed to light using the mask as a mask, and the first resist is patterned into a predetermined pattern by developing the contrast enhancing layer and the first resist.

[Effect]

In this invention, a contrast enhancement layer made of a photobleachable material is formed on the surface of the first resist, and the first resist is exposed to light through the contrast enhancement layer using the patterned second resist as a mask. Even if the second resist absorbs the exposure light incompletely, the contrast of the exposure light to the first resist is improved.

〔Example〕

FIGS. 1A to 1F are cross-sectional process diagrams and waveform diagrams showing one embodiment of the resist pattern forming method according to the present invention. For example, a lower resist 2 is spin-coated onto a substrate 1 made of PMMA (polymethyl methacrylate). Thereafter, as shown in FIG. 1A, a contrast enhancement layer 10 made of a photobleachable material is spin-coated over the entire surface of the lower resist 2.

Next, as shown in FIG. 1B, an upper resist 3 is spin-coated over the entire surface of the contrast enhancement layer 10.

Thereafter, the upper layer resist pattern 3a is formed as shown in FIG. 1C by irradiating the upper layer exposure light 5 through the exposure mask 4 and then developing it. At this time, the upper resist pattern 3a has a trapezoidal shape as in the conventional case.

Next, the contrast enhancement layer 10 is irradiated with lower layer exposure light 6 through the upper resist pattern 3a.

At this time, as in the conventional case, the upper resist pattern 3a has a property of absorbing the lower layer exposure light 6, and therefore, the upper resist pattern 3a functions as a mask when exposing the contrast enhancement layer 10 and the lower resist 2. The contrast enhancement layer 10 is made of a photobleaching material as described above, and as is well known, this photobleaching material bleaches quickly and increases light transmittance when exposed to strong light, and bleaches slowly when exposed to weak light. ing. Therefore, even if absorption of the lower layer exposure light 6 is incomplete on the side surfaces of the trapezoidal upper resist pattern 3a, the contrast enhancement layer 10 is clearly divided into a bleached portion 10a and a non-bleached portion 10b. The bleached portion 10a has a high light transmittance, and the non-bleached portion 10b has a low light transmittance. Therefore, the contrast of the lower layer exposure light 6 applied to the lower resist 2 is improved as shown in FIG. 1E compared to the conventional method (see FIG. 2D). Therefore, the lower resist pattern 2a after development
As shown in FIG. 1F, the rectangularity is better than in the conventional case (FIG. 2A).

〔Effect of the invention〕

As described above, according to the present invention, a contrast enhancement layer made of a photobleaching material is formed on the entire surface of the first resist, and the contrast enhancement layer and the first resist are formed using the patterned second resist as a mask. Since the second resist is exposed to light, the contrast of the exposure light to the first resist is improved even if the second resist absorbs the exposure light incompletely. As a result, when the first resist is developed, it is possible to form the first resist into a desired pattern with high precision.

[Brief explanation of drawings]

1A to 1F are diagrams for explaining an embodiment of the resist pattern forming method according to the present invention, and FIGS. 2A to 2E are diagrams for explaining a conventional resist pattern forming method. In the figure, 1 is a substrate, 2 is a lower resist, 2a is a lower resist pattern, 3 is an upper resist, 3a is an upper resist pattern, and 10 is a contrast enhancement layer. Note that the same reference numerals in each figure indicate the same or corresponding parts. Figure 1A Substrate 2: Lower resist layer 1o: Contrast enhancement layer 1B Figure 3: Upper resist layer 1C Figure 1D Figure 1E Figure 1F Figure 2a: Lower resist pattern Figure 2A Figure 2B

Claims (1)

[Claims] (1) A step of preparing an underlayer, a step of forming a first resist on one main surface of the underlayer, and a step of forming a contrast enhancement layer made of a photobleachable material over the entire surface of the first resist. forming a second resist on the surface of the contrast enhancement layer; patterning the second resist into a predetermined pattern; and using the patterned second resist as a mask to enhance the contrast. exposing the layer and the first resist;
A resist pattern forming method comprising the step of patterning the first resist into a predetermined pattern by developing.