JPH05142753A - Photomask - Google Patents

Abstract

PURPOSE:To prevent the line width of pattern from decreasing or bending in a consecutive part even if consecutive exposing is executed. CONSTITUTION:This photomask is used for the consecutive exposing which exposes an uexposed area while superposing a mask pattern on a part of an already exposed area at the time of exposing the unexposed area adjacent to the already exposed area. A dummy pattern 120 of the line width below the resolving power of the exposing device to be used is provided in the consecutive part to be subjected to the consecutive exposing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask used for manufacturing a large area semiconductor integrated circuit device or an active matrix type liquid crystal display device which exceeds a single exposure area of a step-and-repeat exposure device.

[0002]

2. Description of the Related Art In recent years, a step-and-repeat exposure apparatus for repeatedly projecting and exposing a mask pattern formed on a photomask onto an exposure object (for example, a wafer coated with a photoresist or a glass substrate) has been resolving power. However, in a large-area semiconductor integrated circuit device, liquid crystal display device, or the like, it is necessary to repeat exposure a plurality of times. Here, when exposing the unexposed area adjacent to the already exposed already exposed area, the photomask is aligned so that the mask pattern overlaps a part of the already exposed area, and the unexposed area is exposed in this state. Sometimes. Hereinafter, such exposure is referred to as joint exposure.

[0003]

The above-described joint exposure has a problem as shown in FIG. That is, when exposing the unexposed area, the portion where the mask pattern overlaps the exposed area (hereinafter referred to as the connecting portion C) is exposed not only in the exposed area but also in the unexposed area. Therefore, double exposure is required. Therefore, the joint portion C is exposed more than the other portions, so that the line width of the pattern 300 in the joint portion C tends to be thin, as shown in FIG. In addition, if the alignment of the photomask with respect to the unexposed area shifts, the connecting portion C
The pattern 300 bends.

In order to solve such a problem, the line width of the mask pattern corresponding to the connecting portion is set to be thicker than the line width of other portions, or the portion not affected by the bending is selected as the connecting portion. ing. However, since the mask pattern of the joint portion is complicated and these require special design rules, the joint portion cannot be freely selected. Further, it is difficult to narrow the pitch of the mask pattern at the connecting portion, that is, the pitch between the wirings.

The present invention was devised in view of the above circumstances, and an object of the present invention is to provide a photomask in which the line width of a pattern is not thinned or bent at a joint portion by joint exposure. There is.

[0006]

A photomask according to the present invention is a photomask used in a step-and-repeat exposure apparatus, which is used for exposing an unexposed area adjacent to an exposed area. A dummy pattern having a line width equal to or less than the resolution of the exposure apparatus used is provided in the joint portion where the joint exposure is performed in which the mask pattern is partially overlapped with the mask pattern to expose the unexposed area.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a plan view of a connecting portion of a photomask according to an embodiment of the present invention, FIG. 2 is a plan view showing a result of the first exposure by this photomask, that is, a plan view showing an already exposed area, and FIG. FIG. 4 is a plan view showing a relationship between an exposed area and a photomask when performing a second exposure, that is, an unexposed area, FIG. FIG. 6 is a plan view showing a state where the alignment of the photomask is deviated during the exposure of FIG. 6, and FIG. 6 is a plan view showing the result of exposing the unexposed area in the state shown in FIG.

A photomask 100 according to this embodiment is a photomask used in a step-and-repeat exposure apparatus, and is an unexposed area B adjacent to an exposed area A.
At the time of exposure, the joint exposure is performed by exposing the unexposed area B in a state where the mask pattern 130 is overlaid on a part of the exposed area A. A dummy pattern 120 is provided.

The photomask 100 in this embodiment is
As shown in FIG. 1, the mask pattern 130 is of a positive type, and the two vertical mask patterns 130 and the three dummy patterns 120 provided on both sides of the mask pattern 130 are opaque (in the drawing, It is shown by the diagonal line descending to the right). Here, the dummy pattern 120 is set to have a line width equal to or less than the resolution of the exposure apparatus used. Therefore, even if exposure is performed using this photomask 100, the dummy pattern 120 is not directly exposed. Further, the dummy pattern 120 is set to be slightly longer than a connecting portion C described later.

The joint exposure using such a photomask 100 will be described. In this exposure, the photoresist is left as a pair of parallel linear patterns 200. A first exposure is performed on an exposure target such as a wafer coated with a positive photoresist. By this exposure, an already-exposed area A (indicated by a diagonal line rising to the right in the drawing) as shown in FIG. 2 is formed on the exposure object. Here, although the portion corresponding to the dummy pattern 120 is not directly exposed as the already-exposed area A, the dummy pattern 120 causes insufficient exposure in the connecting portion C. Therefore, the line width of the portion corresponding to the mask pattern 130 in the exposed area A, that is, the line width of the pattern 200, is gradually thickened toward the base end. Here, the exposed area A is an area where the photoresist is removed when the developing process is performed.

Next, the second exposure is performed. This second exposure is carried out in the unexposed area B adjacent to the previously exposed area A.
(It is located below the exposed area A in the drawing). During the second exposure, as shown in FIG. 3, the alignment of the photomask 100 is such that the mask pattern 130 of the photomask 100 is linearly connected to the pattern 200 corresponding to the exposed area A and the tip of the dummy pattern 120 is formed. Is performed so as to project into the unexposed area B. That is, the connecting portion C is also irradiated with light by the second exposure.

Therefore, the connecting portion C has been double-exposed, and a sufficient amount of light for manifestation is given only by double-exposure. However, since the dummy pattern 120 of the connecting portion C is set to have a line width equal to or less than the resolving power of the exposure apparatus, the dummy pattern 120 itself does not appear. Therefore, the line width of the pattern 210 (the part without hatching in FIG. 4) corresponding to the mask pattern 130 in the connecting portion C does not become thin as in the conventional case.

Here, a case where the alignment of the photomask 100 with respect to the unexposed area B is slightly deviated will be described with reference to FIGS. 5 and 6. Here, the line width
The figure shows the misalignment by about 1/10.

In the second exposure, that is, in the exposure of the unexposed area B, even if the alignment of the photomask 100 deviates from the exposed area A by about 1/10 of the line width as shown in FIG. By the dummy pattern 120 provided between the mask patterns 130, the base end portion of the pattern 200 corresponding to the mask pattern 130 in the exposed area A formed by the first exposure is formed thick, so Even if the photomask 100 is misaligned with the unexposed area B, the pattern 210 to be formed by two exposures becomes extremely thin,
It doesn't bend.

[0015]

The photomask according to the present invention is a joint exposure for exposing an unexposed area adjacent to an already exposed area by exposing the unexposed area with a mask pattern overlapping a part of the already exposed area. In the photomask used for, a dummy pattern with a line width that is less than the resolving power of the exposure equipment used is provided in the joint portion where the joint exposure is performed. Does not become thin or bend.

[Brief description of drawings]

FIG. 1 is a plan view of a connecting portion of a photomask according to an embodiment of the present invention.

FIG. 2 is a plan view showing a result of the first exposure by this photomask, that is, an already-exposed area.

FIG. 3 is a plan view showing a relationship between an already-exposed area and a photomask when performing a second exposure, that is, an exposure of an unexposed area.

FIG. 4 is a plan view showing a state where exposure of an unexposed area is completed.

FIG. 5 is a plan view showing a state in which the alignment of the photomask is deviated during the exposure of the unexposed area.

FIG. 6 is a plan view showing a result of exposing an unexposed area in the state shown in FIG.

FIG. 7 is a plan view showing a problem of the conventional joint exposure method.

[Explanation of symbols]

 100 Photomask 120 Dummy pattern 130 Mask pattern A Exposed area B Unexposed area C Joining area

Claims (1)

[Claims] 1. A photomask used for joint exposure, wherein when exposing an unexposed area adjacent to an already exposed area, the unexposed area is exposed with a mask pattern overlapping a part of the already exposed area. A photomask, characterized in that a dummy pattern having a line width equal to or less than the resolution of the exposure apparatus used is provided in the connecting portion where exposure is performed.