JPS62190839A - Exposing method - Google Patents

Abstract

PURPOSE:To miniaturize an integrated circuit and to improve the quality by removing a resist film coated on the alignment mark of a wafer by laser emitting, and then aligning a mask on the wafer to not only improve the alignment accuracy but also to increase a margin in an etching step. CONSTITUTION:Only a resist film 3 on a mark used in a specific masking step is removed by laser emitting to expose the mark. For example, an argon gas laser or a carbon dioxide gas laser is emitted to the film 3 coated on the alignment mark 2 of a wafer 1. This process is more effective by emitting the laser on the resist film while spraying an oxygen as than in vacuum. The laser emission is executed only on the mark used in the masking step on the wafer. The laser may be emitted in addition to the use of an exclusive laser emitting unit by employing a laser light source and an oxygen gas introducing hole in an exposure unit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Required] Accurate alignment of patterns on a mask and a wafer in a lithography process has become an increasingly important problem as integrated circuits become smaller. In the present invention, the accuracy of alignment is improved by first removing the resist film deposited on the alignment marks of the wafer.

[Industrial application field]

The present invention relates to alignment of a wafer and a mask in an exposure process.

In an integrated circuit wafer process, an exposure process using a mask is repeated many times. Each exposure step requires alignment of the wafer and mask patterns prior to exposure.

Alignment is the process of optically aligning the alignment marks on the wafer's scribe line with the corresponding marks on the mask, and the accuracy of this alignment governs the miniaturization design of integrated circuits. It is an important element.

Furthermore, in manufacturing, there is a demand for improved alignment accuracy in order to ensure uniform quality of products.

[Conventional technique i-hote]

Alignment marks on a wafer are usually formed on a scribe line as a cross, an L-shape, a square, a rectangle, or a set of these by etching at an early stage of the wafer process.

A resist film having desired characteristics is deposited on the wafer on which alignment marks have been formed prior to exposure.

This resist film is also deposited on the alignment marks in the same way, so when the cross section of one mark on the wafer is taken, the second
It will look like the figure.

Since the protrusions forming the marks 2 are formed on the wafer 1 by etching, the resist film 3 is deposited on the marks in a convexly raised state.

In a normal alignment process, a mark having the shape described above is irradiated with light to align it with a corresponding mark on a mask.

[Problem that the invention seeks to solve]

In the conventional alignment method described above,
A raised resist film with a non-uniform thickness is deposited on and around the mark.

The irradiated light causes complicated interference and reflection, making it impossible to obtain a sharp image of the edge portion 4 required for alignment.

In order to flatten the surface of the resist film above the mark, an organic film (silanol) 5, HSi(OH) 4-fi is applied to the top of the resist as shown in Figure 3. The effect is small.

[Means for solving problems]

The above problem is solved by the exposure method of the present invention, which comprises removing only the resist film on the mark used in a specific mask process by laser irradiation to expose the mark.

That is, this is achieved by removing the resist film deposited on the alignment mark of the wafer by laser irradiation, and then aligning the mask and the wafer.

Furthermore, the resist film can be easily removed by introducing oxygen gas into the atmosphere during the laser irradiation.

[Effect]

By removing the resist film, it becomes easier to obtain a sharp video signal at the edge portion, and the accuracy of alignment is greatly improved.

〔Example〕

An embodiment according to the present invention will be described in detail with reference to the drawings.

FIG. 1 (al) is a cross-sectional view showing a situation in which a resist film 3 deposited on an alignment mark 2 of a wafer 1 is irradiated with an argon gas laser or a carbon dioxide laser.

In the above process, it is more effective to irradiate the resist film with a laser while blowing oxygen gas onto the surface of the resist film than in a vacuum.

Laser irradiation is performed spot-wise only on alignment marks used in the main mask process on the wafer.

The state after irradiation is shown in FIG. 1(b).

Laser irradiation can be performed not only by using a dedicated laser irradiation device but also by attaching a laser light source and an oxygen gas introduction hole to an exposure device.

〔Effect of the invention〕

As explained above, by applying the exposure method of the present invention, not only the accuracy of alignment is improved, but also the margin in the etching process is widened, which contributes to miniaturization of integrated circuits and improvement of quality. It's large.

[Brief explanation of drawings]

Figure 1 is (al), (b) is a cross-sectional view explaining the exposure method according to the present invention, Figure 2 is a cross-sectional view explaining problems with the conventional technology, and Figure 3 is a countermeasure with the conventional technology. A cross-sectional view is shown for explaining. In the drawings, ■ indicates a wafer, 2 indicates an alignment mark, 3 indicates a resist film, 4 indicates an edge portion, and 5 indicates an organic film (silanol). Fuhaimei 1sa/Kanachirinin No. 35 Tonseimeisu ■Nobuzu No. 1
figure

Claims (1)

[Claims] (1) An exposure method characterized in that the resist film (3) deposited on the alignment mark (2) of the wafer (1) is removed by laser irradiation, and then the mask and the wafer are aligned. (2) When irradiating the laser, oxygen gas is introduced into the atmosphere.
Exposure method described in section 1).