JPH0438355Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to alignment marks for mask alignment of photomasks used in photolithography.

[Conventional technology]

A photomask used in photolithography is produced by drawing a designed mask pattern onto a reticle using an electron beam exposure device or a pattern generator, and using this reticle as a master plate by sequential exposure using a photorepeater. . The mask pattern formed on the photomask includes alignment marks for alignment in addition to a desired chip pattern.

FIGS. 3a and 3b show examples of the shapes of alignment marks for mask alignment of conventional photomasks. In the drawings, the hatched areas are areas that do not transmit light, and the non-hatched areas are areas that transmit light, and the same representation method will be used in the following drawings.

Although a square figure is shown in the figure, other shapes such as rectangles and polygons may also be used.

The alignment marks on photomask A (shown in Figure a) used for photolithography in the first step are closer to the border than the alignment marks on photomask B (shown in Figure b) used in photolithography in the next step. All parts are shifted outward by approximately 2 μm, and when aligning the photomask B to the wafer, all the boundaries of the wafer pattern corresponding to the boundaries of the alignment marks of photomask A are passed through the transparent area of the alignment mark. It is configured so that it can be recognized and the marks can be easily matched.

[Problem that the invention attempts to solve]

Conventional alignment marks are structured as described above, and when changing the resist from a positive resist to a negative resist during the process, or from a negative resist to a positive resist, the photomask is used with the transparent and opaque areas reversed. Although the chip pattern can be used as is, there is a problem in that the alignment mark cannot be used because the size of the corresponding figure of the alignment mark in the previous process is reversed.

For example, when changing the photomasks with alignment marks shown in Figure 3a and b from positive resist to negative resist, the alignment of photomasks A and B can be adjusted by reversing the transparent and opaque areas. The marks are as shown in Figure 4a and b, respectively, and when aligning photomask B to the wafer, the border of the pattern on the wafer corresponding to the borderline of the alignment mark on photomask A can be seen through the transparent area of the alignment mark. Lines cannot be recognized and marks cannot be easily aligned.

In such a case, it was necessary to newly design only the alignment mark portion, create a reticle, and create a photomask.

This idea was made to solve the above problem, and is a photomask with alignment marks that does not require the creation of a new reticle when changing the photomask from one for positive resist to one for negative resist. The purpose is to provide

[Means for solving problems]

The photomask according to this invention has alignment marks each including a first figure and a second figure having a boundary line parallel to the boundary line of the first figure at a certain interval, and With respect to the alignment mark, the alignment mark of the second photomask is such that the facing boundary lines of the first figure and the second figure are in a direction in which the first figure contracts and the second figure expands. It is characterized by being provided at intervals.

[Example of idea]

An embodiment of this invention is shown in FIGS. 1a and 1b. In addition to the cross-shaped figure 1, there is a square figure 2 having a boundary line parallel to the boundary line of the cross-shaped figure 1 at a certain interval, and the photomask A used for the photolithography in the first process (see Fig. a). ) has a cruciform figure 1 compared to that of photomask B (shown in Figure b) used for the next step of photolithography.
All of the boundaries of square shape 2 are shifted outward by about 2 μm, and all of the boundaries of square shape 2 are shifted inward by about 2 μm. That is, the boundary lines of the cross-shaped figure 1 and the square figure 2 that face each other are shifted in the same direction.

For example, in the case of a photomask for positive resist, when aligning the wafer of photomask B, the borderline of the wafer pattern corresponding to the borderline of cross shape 1 of the alignment mark of photomask A is the dotted line in Figure b. The mark can be recognized and the marks can be easily matched.

When the photomask is modified to use a negative resist, FIGS. 1A and 1B become as shown in FIGS. 2A and 2B by reversing the transparent areas and opaque areas, respectively. In this case, when aligning photomask B to the wafer, the borderline of the pattern on the wafer corresponding to the borderline of square shape 2 of the alignment mark on photomask A becomes like the dotted line in Figure b, and the transparent area This can be used to match marks.

Note that the shapes of the figures are not limited to those shown in the examples.

[Effect of idea]

As described above, according to this invention, when changing a photomask from one for positive resist to the other by reversing the transparent area and opaque area, there is no need to newly design alignment marks. , it becomes possible to use a photomask produced using an already produced reticle as is, which greatly contributes to reducing the number of photomask production steps.

[Brief explanation of drawings]

Figures 1a and b are plan views showing one embodiment of this invention, Figures 2a and b are plan views showing the state in which the transparent and opaque areas of Figures 1a and b are reversed, respectively. Figures a and b are plan views showing an example of the shape of alignment marks on a conventional photomask, and Figures 4a and b are
3A and 3B are plan views showing a state in which the transparent area and the opaque area in FIGS. 3a and 3b are reversed, respectively; FIG. 1...Cross shape, 2...Square shape. In addition,
The same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims for Utility Model Registration] In a pair of photomasks used in photolithography, each alignment mark used for mask alignment is parallel to a first figure and a boundary line of the first figure with a certain distance between them. The alignment mark of the second photomask includes a second figure having a boundary line, and the alignment mark of the second photomask has a boundary line that faces opposite to the first figure and the second figure. A photomask characterized in that the first figure is provided at intervals in a direction in which the first figure is contracted and the second figure is in an enlargement direction.