JPS6142134A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a resist pattern without influence of stepped portion of wafer surface by using only the novolac system and cyclization rubber system resist and changing processes and conditions of the conventional process. CONSTITUTION:The stepped portion 2 of wafer 1 is coated with thick novolac system or cyclic rubber system resist 3. The region near to the surface is hardened to form a hardened part 4. This part is then coated with a resist 5 and the stepped portion is selectively irradiated with light 6. Next, the patterned resist 5 is hardened with the far ultraviolet ray. Next, unhardened resist 3 is exposed by the anisotropic etching. Moreover, RIE etching is carried out until the stepped portion 2 is exposed to the surface. Thereby, a resist pattern having less influence of stepped portion can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical field to which the invention pertains The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming a resist pattern on a wafer surface.

(2) Description of the prior art: In a method of creating a resist pattern using light, a method for suppressing dimensional changes on a wafer with steps is as follows:
Generally speaking, there are two conventional methods:

■ First, methacrylic resin positive resist (
PMMA (hereinafter referred to as PMMA) is applied thickly, a novolac positive resist is applied thinly thereon, and the novolak resist is exposed to ultraviolet light and patterned. PMMA is not sensitive to ultraviolet light and is resistant to the developer of novolak positive resists, so it does not change in this step. Next, when the entire surface is irradiated with deep ultraviolet light, since the novolak positive resist does not transmit deep ultraviolet light, PMMA can be masked and patterned.

(2) A thick resist is applied onto the wafer, and a photosensitizer that is resistant to anisotropic dry etching is applied on top of the resist (for example, Gene or polysiloxane is used as the photosensitizer).

Thereafter, the photosensitive agent is patterned, anisotropic dry etching is performed, and the underlying thick resist is patterned by using the photosensitive agent as a mask during this etching.

These conventional methods require the use of multiple resists made of different materials, and the use of other materials and equipment that are not used in conventional processes, which cannot be done using existing manufacturing lines. could not.

(3) Detailed Description of the Invention The present invention enables large quantities to be produced by simply changing the steps and conditions of the conventional process, using only conventionally used equipment and a general novolak resist or speed ratio rubber resist. It is an object of the present invention to provide a method for manufacturing a semiconductor device that can obtain a resist pattern that is resistant to dimensional changes due to wafer steps, which is an advantage of the resist method.

(4) Structure of the present invention The present invention applies a thick resist layer as the first layer to a wafer to be microfabricated, and applies energy only to the surface layer to promote bonding of resist molecules, thereby reducing only the surface resist. After curing, a thin resist J- is applied on top of it, exposed and developed to pattern only the in-situ resist layer, and then energy is applied to only the surface layer again to harden the patterned resist. After that, etching is performed under conditions where the etching rate of the unhardened resist at the bottom is faster than the etching rate of the hardened resist to obtain a desired resist pattern.

(5) Explanation of the principle and operation of the invention In the present invention, novolak resists and cyclized rubber resists undergo molecular MJi combination when energy such as heat, deep ultraviolet rays, or accelerated ions are applied, and the comparison is made before applying energy. The resulting resist becomes molecularized and hardens, and the hardened resist has higher dry etching resistance and resistance to solvents than before hardening, so we discovered that it can be used as a mask when etching thick PR (photoresist). Based.

Furthermore, the above-mentioned bonding between polymers due to heat is 150
This does not occur easily at temperatures below ℃, so post-baking of the resist during etching will not harden the entire resist.

(6) Detailed Description of the Invention Next, one embodiment of the invention will be described with reference to the drawings.

First of all, Fig. 1 shows the step 2 formed on the sea urchin/.-1 and the sea urchin I.-1 (this is mainly caused by diffusion and electrode formation), and the step 2 formed on the sea urchin I.-1 to flatten the step. FIG. 3 is a cross-sectional view of a Ueno film having a thickly applied novolak resist or a speed ratio rubber resist (hereinafter abbreviated as resist) 3; After this, only the vicinity of the surface of the thick resist 3 on the wafer 1 is hardened. Harden the resist. Deep ultraviolet light can be used to cure the resist, e.g.
Novolak resin resist Az 1350J, Az-
2400, quantified rubber type resist) OMR-83 is the 10th
It has light transmission characteristics as shown in the figure, and it is difficult for light to pass through at short wavelengths, whereas deep ultraviolet light does not penetrate into the resist and remains on the surface. Therefore, when the resist is irradiated with deep ultraviolet light, the seven molecules of the novolac type resist bond with each other to form a three-dimensional network structure and harden. In addition, in the case of a high-ratio rubber system, a crosslinking reaction between polymers and bonding between seven polymers occur, resulting in curing. In this way, about 26ON1 as far ultraviolet light
When the entire surface of the wafer is exposed at once using light of 1 or less, only the area near the surface of the thick resist is cured, forming a hardened portion 4 (see FIG. 2).

Next, a resist 5 is thinly applied onto the hardened portion 4, and the step portion is selectively irradiated with light 6 sufficient to expose the resist 5 (see FIG. 3). If the resist is positive type, the exposed area is removed after development and patterned (
(See Figure 4).

However, if the resist 5 is a negative type, the exposed portion will remain and an inverted pattern will be created.

Next, the upper surface of the wafer is again irradiated with deep ultraviolet light to harden the patterned resist 5 (see FIG. 5).

Next, the entire surface was subjected to reactive ion etching (hereinafter referred to as RI).
Anisotropic etching such as E) is performed to expose the unhardened resist 3 (see FIG. 6). The hardened resist 4 remaining at that time serves as a mask for etching the unhardened resist 3 thereafter.

Further etching is performed, but the etching conditions are as follows:
If RIE etching is performed under conditions where the etching rate of the unhardened resist 3 is higher than the etching rate of the hardened resist 4, and the etching is performed until the step portion 2 is exposed on the surface, the shadow caused by the step L will be removed. A resist pattern with fewer bumps can be formed (see FIG. 7).

When the uncured resist 3 is exposed on the surface as shown in the thin tube 6, if solvent and isotropic dry etching are performed,
A resist pattern having a tapered cross-sectional shape as shown in FIG. 8 can also be formed.

If the hardened resist remains as shown in Figure 7,
By permeating the bath agent, it is also possible to form a resist pattern having a horizontally overlapping cross-sectional shape as shown in FIG.

As methods for curing only the surface of the resist, in addition to deep ultraviolet light, ion implantation, plasma treatment, and applying heat to the surface while cooling the wafer can be employed.

(Detailed Description of the Invention) As explained above, the present invention uses only novolac and degraded rubber resists that have been widely used in the past.
An advantage of the multilayer resist method is that a resist pattern that is not affected by steps on the wafer surface can be obtained by simply changing the steps and conditions of the conventional process.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a thick resist coated on a wafer with steps, Figure 2 is a cross-sectional view of a hardened layer formed on the resist surface of Figure 1, and Figure 3 is a thin layer of resist applied to the surface of Figure 2. 4 is a cross-sectional view of the thin resist shown in FIG. 3 after being patterned, FIG. 5 is a cross-sectional view of the patterned resist shown in FIG. Figure 7 is a cross-sectional view when the surface of the wafer is anisotropically etched until the unhardened resist is exposed. , Figure 8 is a cross-sectional view of the exposed wafer in Figure 6 exposed by solvent or isotropic dry etching, and Figure 9 is a cross-sectional view of the exposed wafer in the state shown in Figure 7 with the steps on the wafer surface exposed. FIG. 10 is a custom-made light transmission diagram of the novolak resists AZ-1350J and AZ-2400 and the speed ratio -f resist OMR-83. 1...Wafer, 2...Steps on the wafer, 3...Resist coated thickly to cover the step portion 2 and flatten the steps, 4.・・・・・・
Hardened portion of the surface of the resist 30, 5... Thin resist layer applied on the hardened portion 4, 6... Ultraviolet light for exposing layer 5, 7... Pattern The layer 8, which is obtained by hardening the etched layer 5, is used to pattern the resist 3 by anisotropic etching.
The part that remained. 1゜Representative: Susumu Uchihara, patent attorney.゛・−′ Figure 7 Is it long? ? ) Broom /θ diagram

Claims (1)

[Claims] A first thick resist layer is provided on the surface of a semiconductor substrate having a step, the vicinity of the surface is hardened, and a second thin resist layer is further applied on top of the first thick resist layer, and the second thin resist layer is formed to correspond to the step. Based on this pattern, the first
The etching rate of the exposed unhardened resist layer is higher than the etching rate of the hardened resist layer by removing a part of the hardened part of the thick resist layer and exposing the surface of the unhardened resist layer underneath. A method for manufacturing a semiconductor device, characterized in that etching is performed under rapid conditions to form a desired resist pattern.