JPH05134388A - Exposure method - Google Patents

Abstract

PURPOSE:To provide an exposure method possible to form a high accuracy pattern by reducing or dissolving halation effect. CONSTITUTION:The exposure method to form a resist film 5 having uniform thickness on a film to be processed having a step difference on the surface and to expose the resist film 5 covered with a photomask having a prescribed normal light shielding pattern 7 is constituted by using a photomask 6 adding an assistant light shielding pattern 8 connecting to the normal light shielding pattern in a position corresponding to the step difference in the vicinity of the normal light shielding pattern 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method applied to, for example, a photolithography process in a semiconductor integrated circuit manufacturing process, and more particularly to an exposure method capable of accurately forming a pattern of a resist film.

[0002]

2. Description of the Related Art In a manufacturing process of a semiconductor integrated circuit, for example, as shown in FIG. 3A, a first layer wiring 102, an insulating film 103, and an aluminum (A1) film 104 are layered in order on a surface of a semiconductor substrate 101. The aluminum film 104 is formed on the second layer wiring having a predetermined pattern in a photolithography process.

In the photolithography process, a resist film 5 is applied on the aluminum film 104 to have a substantially uniform thickness, and a photomask 106 having a predetermined regular light-shielding pattern 107 is covered and exposed to light. A part of the resist film 105 is photolyzed by the light beam that has passed through the light part, and the photolyzed part of the resist film 105 is dissolved and removed by a developing solution.

After that, the exposed portion of the aluminum film 104 is removed by etching in an etching process, whereby a second layer wiring having a predetermined pattern, that is, a regular pattern is formed. The resist film 105 remaining on the second layer wiring is thereafter removed.

[0005]

[Problems to be Solved by the Invention] Aluminum film 104
The first layer wiring 10 formed on the surface of the
A step is formed between the portion with 2 and the portion without, and the inclined surface 104a is formed on the surface of the aluminum film 104 between the steps.

When the exposure light i is incident on the inclined surface 104a, the reflected light r is reflected by the regular pattern portion 105a of the resist film 105 which should be shielded by the photomask 106, and a part of the regular pattern portion 105a is formed. When photo-decomposed, the line width of the regular pattern portion 105a becomes thin or disappears (see FIG. 3B).

Such a phenomenon is called a halation effect, and due to this halation effect, the normal pattern portion 10
If the tape 5a is thinned or disappears, a part of the regular pattern is etched in a later etching step, and the second layer wiring is thinned or broken, resulting in a defect. Particularly, when the aluminum film 104 is etched by dry etching, the A1 wiring is easily broken due to electromigration or stress migration.

Further, with the progress of higher integration and higher density, a submicron level resist pattern forming technique is required in the photolithography process. In order to meet this requirement, it is most effective to shorten the wavelength of the exposure light i, from the g-line (wavelength 436 nm) to the i-line (wavelength 365 nm) of a mercury lamp.
Or, it is being changed to Krypton fluoride (KrF) excimer laser light (wavelength 248 nm).

Further, it is necessary to increase the optical transparency of the resist material with respect to the exposure light in order to sufficiently secure the resolution for the exposure light having the shortened wavelength, and the light absorption by the resist material is almost eliminated.

Therefore, the shortening of the wavelength is accompanied by the higher transparency of the resist material, and therefore aluminum (Al), tungsten silicide (WSi ₂ ), polysilicon (p
The harlection effect due to the step on the surface of the film to be processed such as oli-Si) is further promoted. In the future, such measures to prevent halation effects will become important.

It is an object of the present invention to provide an exposure method which can reduce or eliminate the halation effect and stably perform highly accurate pattern formation.

[0012]

According to the exposure method of the present invention, a resist film having a uniform thickness is formed on a film to be processed having a step on the surface, and the photosensitive film has a predetermined regular light-shielding pattern. In the exposure method of exposing by exposing a photomask,
It is characterized by using a photomask in which an auxiliary light-shielding pattern continuous with the regular light-shielding pattern is added at a position corresponding to the step near the regular light-shielding pattern.

[0013]

According to the present invention, the auxiliary light-shielding pattern that is continuous with the regular light-shielding pattern blocks the exposure light that is incident on the stepped portion of the surface of the film to be processed, so that the halation effect at the stepped portion can be obtained. Reduced or eliminated.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The exposure method according to one embodiment of the present invention will be described below with reference to FIG.

In FIG. 1A, 1 is a semiconductor substrate and 2 is a semiconductor substrate.
Is a first layer wiring, 3 is an insulating layer, 4 is an aluminum layer as a film to be processed, 5 is a resist layer, and a method of forming these is the same as the conventional method.

A regular pattern 7 corresponding to a predetermined line width is formed on the photomask 6 used in the exposure in the photolithography process, and the regular pattern portion 5a of the resist layer 5 shielded by the regular pattern 7 is the aluminum layer 4. 1A and 1B, the photomask 6 is provided with an auxiliary pattern 8 that covers the inclined surface 4a in succession to the regular pattern 7 in the portion approaching the inclined surface 4a.

When this photomask 6 is covered on the resist layer 5 and irradiated with exposure light, the exposure light which is about to enter the inclined surface 4 a is blocked by the auxiliary pattern 8. Thereby, the exposure light is prevented from entering the inclined surface 4a and reflected by the regular pattern portion 5a of the resist layer 5 to prevent halation, and the normal pattern portion 5a of the resist layer 5 may be photodecomposed by the halation effect. Disappear.

As a result, it is possible to reliably prevent the line width of the regular pattern portion 5a from becoming thin or disappear due to the halation effect, and it is possible to surely prevent the line width of the second layer wiring from becoming thin or disappear in the subsequent etching step. ..

The width of the auxiliary pattern 8 is the same as that of the inclined surface 4a.
From the regular pattern portion 5a to the aluminum layer 4
Is determined in consideration of the surface reflectance, the amount of incident light, etc., and can be calculated using a computer, for example, at the stage of pattern design.

FIG. 2 is a schematic cross-sectional view showing another embodiment of the present invention. If the width of the auxiliary pattern 8 is appropriately selected in consideration of various conditions such as the surface reflectance and the amount of incident light as described above. good.

The resist layer 5 is formed by reflecting the exposure light.
When the line width of the regular pattern portion 5a is thin on one side, the auxiliary pattern 8 may be provided on only one side of the regular pattern 7.

[0022]

As described above, according to the present invention, the incident of the exposure light to the stepped portion of the film to be processed is blocked by the auxiliary pattern. It is possible to prevent the occurrence of defects such as line width narrowing and disconnection due to excessive etching of the film to be processed due to thinning of the resist pattern and disconnection.

Moreover, according to the present invention, it is only necessary to change the shape of the light-shielding pattern of the photomask.
And it can be implemented at low cost.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an exposure method of the present invention.

FIG. 2 is an explanatory diagram of another embodiment of the present invention.

FIG. 3 is an explanatory diagram of a conventional exposure method and its problems.

[Explanation of symbols]

 4 Aluminum film 5 Resist layer 6 Photomask 7 Regular light-shielding pattern 8 Auxiliary light-shielding pattern

Claims (1)

[Claims] 1. An exposure method in which a resist film having a uniform thickness is formed on a target film having a step on the surface, and the photosensitive film is exposed by covering it with a photomask having a predetermined regular light-shielding pattern. An exposure method characterized by using a photomask in which an auxiliary light-shielding pattern continuous with the regular light-shielding pattern is added at a position corresponding to the step near the regular light-shielding pattern.