JPH08123011A - Photomask - Google Patents

Abstract

PURPOSE: To dispose alignment marks of the width exceeding the width of scribing lines at these scribing lines. CONSTITUTION: Alignment mark areas 14 are delineated by providing the corner- parts in positions where the scribing lines 13, 13 of pellet patterns 12 intersect respectively with notched parts 15 and these areas 14 are provided therein fully with alignment marks 16. Since the alignment marks 16 are partly confined within the notched parts 15, the alignment marks 16 are formable to the outside diameter D larger than the width W of the scribing lines 13 and the alignment accuracy is improved. There is no need for widening the width W of the scribing lines 13, therefore, there is no need for decreasing the effective areas of the pellet patterns 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to photomasks, and in particular to
The present invention relates to a configuration of an alignment mark, for example, to a technique effectively used for a photomask used for overlay exposure of a plurality of layers of circuit patterns on the same wafer in a semiconductor device manufacturing process.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process, when a plurality of layers of circuit patterns are superposed and exposed on the same wafer, the circuit pattern previously formed on the wafer is aligned with the circuit pattern to be exposed. (Alignment) is required. As an alignment technique for superposing these patterns on each other, there is a technique for preliminarily forming a mark (alignment mark) for alignment on a photomask and detecting the alignment mark to ensure the alignment.

As a technique for forming an alignment mark on a photomask, by providing the alignment mark on a scribe line, the alignment mark is preliminarily attached to the photomask without reducing the number of pellets obtained per wafer. The technique to do is possible.

An example of a technique for forming an alignment mark is disclosed in Japanese Patent Application Laid-Open No. 52-26902.
There is. Japanese Patent Laid-Open No. 54-1553 discloses an example of an alignment technique using alignment marks.

[0005]

However, in the technique of disposing the alignment mark on the scribe line, the width of the scribe line is restricted by the size of the alignment mark, so that the scribe line width can be reduced. Therefore, there is a problem that the increase in the number of obtained pellets is limited by the size of the alignment mark.

An object of the present invention is to provide a photomask capable of disposing an alignment mark larger than a scribe line width on a scribe line.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0008]

The typical ones of the inventions disclosed in the present application will be outlined below.

That is, the cutouts are formed so as to face the scribe lines of at least two transferred patterns in the group of transferred patterns arranged vertically and horizontally with the scribe lines sandwiched between them on the mask blank. An alignment mark is arranged in the area of the scribe line defined by the cutout.

[0010]

According to the above-mentioned means, since a part of the alignment mark fits in the notch, the alignment mark larger than the scribe line width is provided. Since the notch is formed in the transferred pattern beyond the scribe line width, the scribe line width itself does not become narrow. In other words, since the scribe line width is not reduced even if the alignment mark is increased, the effective area for transfer pattern formation is not reduced.

[0011]

1A and 1B show a photomask according to an embodiment of the present invention. FIG. 1A is a plan view and FIG. 1B is a sectional view taken along a diagonal line. FIG. 2 is a schematic front view showing a reduction projection exposure method using the photomask. FIG. 3 is a plan view showing a wafer that has been subjected to pattern formation processing after exposure.

In the present embodiment, the photomask according to the present invention is configured as an enlarged photomask (also referred to as a reticle; hereinafter, simply referred to as a photomask) used in the reduction projection exposure method. Further, this photomask is used in the manufacturing process of a semiconductor device, for example,
It is configured to be used for manufacturing a power MOSFET, and is configured as a photomask for transferring the first pattern to a wafer in the manufacturing process of the power MOSFET.

The photomask 10 according to the present embodiment is provided with a mask blank 11 made of quartz glass or the like and formed in a square plate shape. A plurality of pellet patterns 12 (four in this embodiment) as transferred patterns are formed on one main surface (hereinafter, referred to as a formation surface) of the mask blank 11, and the scribe lines 13 are sandwiched between them to form a grid pattern. Are vertically and horizontally arranged. For example, the pellet pattern 12 is formed by using chrome.

In the present embodiment, the alignment mark area 1 is provided at the position where the two scribe lines 13 intersect.
4 is set to a square, and an alignment mark 16 is arranged in this area 14. At the corners of the four pellet patterns 12 forming the two scribe lines 13 in which the square alignment mark areas 14 are set and forming a right angle, a semicircular cutout 15 is provided on the convex side of the area 14. It is arranged so as to be on the side and formed respectively. For example, when the size of the pellet pattern 12 is 2 mm □, the curvature of the cutout 15 is
It is set to 126.3 μm. The square alignment mark area 14 is formed such that the centers of the four cutout portions 15 are located on diagonal lines, and the four cutout portions 15 are formed in the alignment mark area 14.
It is designed to form a part of each. Therefore, the outer diameter D of the alignment mark area 14 is larger than the width W of the scribe line 13.

In this embodiment, the alignment mark 1
6 is a frame mark portion 17 formed in a square frame shape,
Cross mark portion 18 arranged at the center of frame mark portion 17
And the blank mark portion 1 formed outside the frame mark portion 17
9 and are formed to fill the square alignment mark area 14. The blank mark portion 19 of the alignment mark 16 is the pellet pattern 1
The alignment mark 16 is a mark portion for forming a boundary with the alignment mark 2, and the alignment mark 16 is arranged so that the outer edge of the blank mark portion 19 coincides with the edge of the alignment mark area 14. Therefore, the outer diameter D of the alignment mark 16 is larger than the width W of the scribe line 13.

Next, a reduction projection exposure method using the photomask 10 having the above structure will be described. A reduction projection exposure apparatus 20 used in the reduction projection exposure method includes a light source 21 for irradiating ultraviolet rays or the like, a light source side lens 22, a holder 23 for holding the photomask 10, a reduction lens 24, and a wafer 30. And an XY table 25 for holding After the photomask 10 is held by the holder 23 and the wafer 30 is held by the XY table 25, when the exposure light 26 such as ultraviolet rays is emitted from the light source 21, the pellet pattern 12 group and the alignment mark 16 of the photomask 10 are removed. Reduction lens 2 on wafer 30
The image is reduced and projected by 4 and transferred to a resist (not shown) applied on the wafer 30.

When the one-shot transfer is completed, the XY table 25 is moved in the X or Y direction by one shot corresponding to the transfer surface of the photomask 10, so that the wafer 30 corresponding to the next one shot is transferred. The unexposed area is located directly below the photomask 10. Then, the above-described exposure work is performed again. After that, by repeating the movement of the XY table 25 and the exposure operation, the pellet pattern 12 of the photomask 10 is
The group and the alignment mark 16 are transferred onto the wafer 30 for each one shot.

When the transfer onto the entire surface of the wafer 30 is completed, the wafer 30 is unloaded from the XY table 25 and transferred to the next process such as the etching process. When the predetermined etching process and the like are completed, as shown in FIG. 3, a pellet portion 32 group, a scribe line portion 33, and an alignment mark portion 34 in which the transferred pattern is exposed are formed on the wafer 30. It will be in a state of being. In this state, the alignment mark portion 3
4 is arranged in each one-shot area 31.

After that, when the second layer pellet pattern is superposed and exposed on the wafer 30 by a second layer photomask (not shown), the alignment mark portion 34 formed on the wafer 30 is removed. It is read by a mark reading device (not shown) in the reduction projection exposure device 20. That is, when the wafer 30 is held on the XY table 25, the mark reading device optically reads the alignment mark portion 34. The reduction projection exposure apparatus 20 finds the origin of the coordinates of the wafer 30 based on the read position of the alignment mark portion 34, and based on the origin, the pellet portion 32 previously formed on the wafer 30 and an attempt to transfer it. The pellet pattern formed on the photomask for the second layer is automatically aligned.

According to the above embodiment, the following effects can be obtained. (1) A part of the alignment mark 16 is cut out 15
The outer diameter D of the alignment mark 16
Can be set larger than the width W of the scribe line 13, so that the alignment accuracy can be improved.

(2) By placing a part of the alignment mark 16 in the notch 15, the scribe line 1
Since the outer diameter D of the alignment mark 16 can be set large without widening the width W of 3, the effective area for forming the pellet pattern need not be reduced. As a result, it is possible to avoid a decrease in the number of pellets obtained per wafer due to the enlargement of the alignment mark.
It is possible to prevent a decrease in productivity in manufacturing T.

(3) Usually, the size of the alignment mark is specified by the standard. Therefore, the size of the alignment mark cannot be set small. Therefore, the width W of the scribe line 13 is set relatively narrower by the amount that the alignment mark 16 can be set larger, so that the number of pellet patterns 12 to be acquired per wafer is increased. You can

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the embodiments and various modifications can be made without departing from the scope of the invention. Needless to say.

For example, the alignment mark area, the notch and the alignment mark may be constructed as shown in FIGS. 4 and 5. In FIG. 4 (a),
Each notch 15A is formed in a right-angled triangle, and the square alignment mark area 14A is arranged so that its four sides are inclined so as to match the oblique sides of the four notches 15A.

In FIG. 4B, each notch 15B is formed in a square shape, and the square alignment mark area 14B has four corners each notch 15B.
They are arranged so as to match B respectively.

As shown in FIG. 4 (b),
Notches 1 are also formed in the remaining three corners where the alignment mark area of the pellet pattern 12 is not provided.
When 5B is formed, the entire pellet pattern 12 can be designed symmetrically, so that the effect of facilitating pattern design is obtained. On the other hand, FIG. 1 and FIG.
As shown in FIG. 3, when the cutouts 15 and 15A are not formed in the remaining three corners where the alignment mark areas of the pellet pattern 12 are not provided, the effective area for pellet pattern formation is reduced. Can be suppressed to a minimum.

FIG. 5 shows the alignment mark area 14C.
Shows an example in which the two are arranged on opposite sides of a pair of pellet patterns 12 adjacent to each other with the scribe line 13 interposed therebetween. That is, rectangular notches 15C are formed symmetrically on opposite sides of the pair of pellet patterns 12, and the square alignment mark area 14C is arranged so that the pair of opposite sides are aligned with both notches 15C, 15C. Has been done.

Further, the alignment mark 16 is not limited to the one used in the above-described embodiment, but the X-shape, the L-shape, the T-shape.
A combination of letter shapes can be used.

The number of pellet patterns and alignment marks to be arranged on one photomask is not limited to one as in the above-mentioned embodiment, but may correspond to various conditions such as the structure of the pattern to be formed and the degree of integration. It is desirable to select a plurality appropriately.

The photomask according to the present invention is not limited to the one for the first layer, but may be applied to the one for the second layer and thereafter.

In the above description, the case where the invention made by the present inventor is mainly applied to the enlarged photomask (reticle) and the reduced projection exposure method which are the fields of application which are the background of the invention has been described, but the invention is not limited thereto. Instead, the present invention can be applied to general photomasks such as one-to-one photomasks and general exposure methods such as contact exposure methods and proximity exposure methods.

Further, in the above description, the case where the invention made by the present inventor is mainly applied to the manufacturing technology of the power MOSFET which is the field of application as the background has been described, but the present invention is not limited to this. The present invention can be applied to general manufacturing fields in which a photomask is used, such as manufacturing fields of semiconductor devices and liquid crystal panels.

[0033]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows.

Notch portions are formed so as to oppose each other at positions in contact with the scribe lines in at least two transferred patterns of the transferred pattern group arranged vertically and horizontally with the scribe line sandwiched between them on the mask blank. By arranging the alignment mark in the area of the scribe line defined by the parts, it is possible to configure an alignment mark larger than the scribe line width without widening the scribe line width. The alignment accuracy can be improved without reducing the effective area.

[Brief description of drawings]

1A and 1B show a photomask which is an embodiment of the present invention, in which FIG. 1A is a plan view and FIG. 1B is a sectional view taken along a diagonal line.

FIG. 2 is a schematic front view showing a reduction projection exposure method using the photomask.

FIG. 3 is a plan view showing the wafer that has undergone the pattern formation processing after exposure.

4 (a) and 4 (b) are plan views showing another embodiment in which an alignment mark is provided at the intersection of scribe lines.

FIG. 5 is a plan view showing an embodiment in which an alignment mark is arranged in the middle of a scribe line.

[Description of sign]

10 ... Photomask, 11 ... Mask blank, 12 ... Pellet pattern (transferred pattern), 13 ... Scribe line, 14, 14A, 14B, 14C ... Alignment mark area, 15, 15A, 15B, 15C ... Notch, 16 ... Alignment mark, 17 ... Frame mark part, 1
8 ... Cross mark part, 19 ... Blank mark part, 20 ... Reduction projection exposure device, 21 ... Light source, 22 ... Light source side lens, 23 ...
Photomask holder, 24 ... Reduction lens, 25 ... XY table, 26 ... Exposure light beam, 30 ... Wafer, 31 ... One shot area, 32 ... Pellet part, 33 ... Scribe line part, 34 ... Alignment mark part.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Rei Meguro 5-20-1 Kamimizuhonmachi, Kodaira-shi, Tokyo Incorporated company Hitachi Ltd. Semiconductor Division

Claims (3)

[Claims] 1. A photomask in which a plurality of transferred patterns are vertically and horizontally arranged on both sides of a scribe line on a mask blank, and an alignment mark is formed on the scribe line. Cutouts are formed so as to oppose each other at a position in contact with the scribe line in at least two transferred patterns, and the alignment mark is provided in the area defined by the cutouts in the scribe line. A photomask that is characterized by 2. The cutouts are respectively formed at four corners of a transferred pattern at positions where the scribe lines intersect, and the alignment mark is within an area defined by these four cutouts. The photomask according to claim 1, wherein the photomask is disposed in the photomask. 3. The cutouts are formed on opposite sides of two transferred patterns that are adjacent to each other with the scribe line in between, and the alignment mark is within an area defined by the two cutouts. The photomask according to claim 1, wherein the photomask is disposed in the photomask.