JP2752148B2 - Wafer exposure method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to an exposure method for a wafer, and particularly to an exposure method for a peripheral portion of a wafer. In order to determine the position of the chip, the area on the wafer where the resist film is formed over the entire surface is divided, and in a wafer exposure method that exposes each divided area, a unit rectangle that is the minimum exposure area is When a virtual net as a mesh is applied to the entire surface of the wafer, 1.A mesh overlapping the peripheral portion of the wafer is exposed over the entire peripheral portion, and after the resist film on the peripheral portion of the wafer is removed, the resist film remains. A method of exposing a wafer for exposing the formed chip forming area; and 2. a point at which two orthogonal virtual threads of a virtual net passing substantially at the center of the wafer intersect with the peripheral edge of the wafer,
Except for the mesh on both sides of the position confirmation point, a mesh overlapping with the periphery of the wafer is exposed over the entire periphery of the periphery, and both sides of the position confirmation point are exposed with a gap so as to provide an unexposed area,
After the resist film on the peripheral portion of the wafer is removed, the wafer is exposed by exposing the chip formation region where the resist film remains.

[Industrial applications]

The present invention relates to a method for exposing a wafer, and more particularly, to a method for exposing a wafer peripheral portion.

In the semiconductor photo process, it is necessary to remove the resist at the peripheral portion of the wafer after forming a resist film on the entire surface of the wafer. The resist coating film usually becomes thicker at the periphery of the wafer, and a part of the resist film may be peeled off in a subsequent process. In addition, when the wafer is stored in the carrier, the peripheral edge of the wafer comes into contact with the groove of the carrier, and the resist at that portion is peeled off. The stripped resist becomes dust and hinders subsequent processes. For this reason, after the resist film is formed on the entire surface of the wafer, the resist on the peripheral portion of the wafer is removed.

In addition, in the manufacture of integrated circuits, it is also required to increase the number of chips that can be obtained from one wafer while minimizing the area of the peripheral edge of the wafer from which the resist is removed.

In addition, when chips are taken from a wafer on which a large number of chips on which elements have been formed are arranged and bonded to die pads, it is also required to prevent chips from being mixed up.

[Conventional technology]

Conventionally, as one of the methods for removing the resist at the peripheral portion of the wafer, there is a method as shown in a conventional example I in FIG. In FIG. 5, reference numeral 1 denotes a wafer having a resist film formed on the entire surface, 61 denotes a wafer stage, 62 denotes a rotation motor, 63 denotes a table, and 66 denotes an optical lens system forming a part of an exposure apparatus.

In this method, the resist on the wafer peripheral portion is removed by rotating the substantially circular wafer 1 around the central axis and exposing a certain width from the wafer peripheral portion by the optical lens system 66. However, if the accuracy of the wafer position setting is poor due to variations in the dimensions of the wafer and the shape of the chip to be taken from the wafer in the future in the future, the chip near the wafer edge in the subsequent process There have been problems such as the occurrence of defects and the inaccurate determination of chip positions on the wafer.

There is also an exposure apparatus that exposes a fixed width from the wafer peripheral portion while automatically detecting the peripheral position of the wafer. Sixth
Conventional example II in the figure is a diagram for explaining this. An optical lens system, 67 is a light emitting system, 68 is a light receiving system, and 81 is a moving stage.

In this apparatus, when the shape of the wafer slightly deviates from the circle, the amount of light entering the light receiving system 68 changes, and the amount of change is fed back to the moving stage 81 to move the moving stage 81 so that the peripheral portion of the wafer is always kept at a constant level. The exposure is performed in a width.

According to this apparatus, the resist at the peripheral portion of the wafer is uniformly removed with a certain width, and the problem that the resist at the peripheral portion of the wafer peels off and is solved can be solved. In such a case, there is a problem that a defect occurs in a chip near the peripheral portion of the wafer in a later process, and a position of the chip on the wafer cannot be accurately determined.

[Problems to be solved by the invention]

In view of the drawbacks of the conventional method described above, the present invention solves the problem that the resist on the peripheral edge of the wafer is peeled and becomes garbage, and accurately determines the peripheral exposure position so that a chip near the peripheral edge of the wafer does not cause a defect. It is an object of the present invention to increase the number of chips that can be taken from one wafer, determine the positions of the chips on the wafer, and prevent chips from being mixed at the time of die bonding or the like.

[Means for solving the problem]

FIG. 1 is a view for explaining the principle of the present invention. FIG. 1 (a) shows a method of exposing the entire periphery of the wafer, and FIG. 1 (b) shows an unexposed area for position confirmation on a part of the periphery of the wafer. FIG. 7 is a diagram for explaining a method of exposing the entire peripheral portion except for the above.

1 (a) and 1 (b), 1 is a wafer having a resist film formed on the entire surface, 11 is a peripheral portion of the wafer, 2 is a virtual net,
Reference numeral 21 denotes a mesh overlapping the peripheral portion of the wafer, 22 denotes a mesh on both sides of the position confirmation point, 31 and 32 denote virtual threads, 41 and 42 denote position confirmation points, and 51 and 52 denote unexposed areas.

The object of the present invention is to: 1. A method of exposing a wafer in which a resist film is formed on an entire surface and dividing the area on the wafer, and exposing each divided area. Is applied over the entire surface of the wafer, the mesh overlapping the peripheral portion of the wafer is exposed over the entire peripheral portion, the resist film on the peripheral portion of the wafer is removed, and the chip forming region where the resist film is left is exposed. 2. In the wafer exposure method in which the area on the wafer where the resist film is formed on the entire surface is divided and the wafer is exposed in each divided area, the unit rectangle that is the minimum exposure area is meshed. When a virtual net is put on the entire surface of the wafer, a point at which two orthogonal virtual yarns of the virtual net passing substantially at the center of the wafer cross the peripheral edge of the wafer is defined as a position confirmation point, and both sides of the position confirmation point The mesh After exposing the mesh overlapping the peripheral portion of the wafer over the entire periphery of the peripheral portion, exposing the both sides of the position confirmation point with a gap so as to provide an unexposed area, and removing the resist film at the peripheral portion of the wafer. The problem is solved by a wafer exposing method for exposing a chip forming region where a resist film is left.

[Action]

In the present invention, first, a unit rectangle serving as a minimum exposure area is determined. This unit rectangle corresponds to the shape of a chip to be taken in the future from the wafer.

If a virtual net having the unit rectangle as a net is applied to the entire surface of the wafer, an area corresponding to a mesh inside the wafer that does not overlap with the periphery of the wafer is an area that can be used as a chip in the future, and corresponds to a mesh that overlaps with the periphery of the wafer. Area cannot be used as a chip. If the portion of the mesh that overlaps with the wafer periphery is exposed to remove the resist film at that portion, the problem that the resist film at the wafer periphery is peeled off in a subsequent process and adversely affects is eliminated.

Further, the position of a chip to be taken in the future is determined by a virtual network having a unit rectangle as a mesh, and the number of chips that can be used as a chip can be maximized.

Further, if a position confirmation point is provided and an unexposed area including the position confirmation point is formed, the position where the chip is to be formed on the wafer alone is determined even if the dimensions vary from wafer to wafer. Is determined, and for example, there is no case where chips are mixed up at the time of die bonding.

Exposure for each mesh of the virtual net is performed, for example, by placing a wafer on an XY stage that moves in the X and Y directions, aligning the directions of both sides of the unit rectangle in the X and Y directions, and setting the X and Y directions.
This is achieved by moving stepwise in the direction with the unit rectangle dimension as the unit and exposing.

The position confirmation point determines the X-axis and the Y-axis passing through the center of the wafer. However, since the nominal dimensions of the wafer and the chip are known in advance, the position can be set in advance.

〔Example〕

 Hereinafter, embodiments of the present invention will be described.

FIG. 4 is a view for explaining an apparatus for carrying out the present invention. FIG. 4 (a) is a view for explaining a step moving mechanism, and FIG. 4 (b) is a view for explaining an arrangement of sensors. .

4 (a) and 4 (b), 1 is a wafer having a resist film formed on the entire surface, 61 is a wafer stage, 62 is a rotation motor, 63 is a table, 64 is an X-direction linear pulse motor, and 65 is Y
A directional linear pulse motor, 66 represents an optical lens system, and 71, 72, 73 represent sensors.

The wafer 1 is fixed to the wafer stage 61 by vacuum suction. The wafer stage 61 is rotated by a rotation motor 62, and the wafer stage 61 is further moved in the X direction by an X
Moves in the Y direction.

The wafer 1 is moved by the rotation motor 62 and the linear pulse motors 64, 65, and the position of the wafer 1 is determined by the sensors 71, 72, 73 set in advance according to the number of inches of the wafer.

The sensor is, for example, a photo sensor, and detects that the peripheral portion of the wafer has reached that position. For example, the sensors 71 and 72 are arranged so that the orientation flat of the wafer 1 is aligned in the X direction, and the sensor 73 is arranged in the X direction passing through the center of the wafer 1.

After the position of the wafer 1 is thus determined, the wafer is moved stepwise by the size of a unit rectangle by the X-direction linear pulse motor 64 and the Y-direction linear pulse motor 65, and the portion where the wafer periphery enters the unit rectangle. Only exposed.

FIG. 2 shows an example in which a unit rectangle including a peripheral portion of a 6-inch wafer is entirely exposed in Example I. In FIG. 2, 1 is a wafer having a resist film formed on the entire surface, 11 is a peripheral portion of the wafer, and 21 is a mesh overlapping with the peripheral portion of the wafer.

First, the size of the unit rectangle is set to 5 mm both vertically and horizontally, and the position of the peripheral edge to be exposed is determined in accordance with the nominal size of the 6-inch wafer. The dimensions of the unit rectangle correspond to the dimensions of the chip to be cut out after forming the element.

Next, for example, the exposure is started from the position of the orientation flat, and the wafer is successively moved by the vertical length or the horizontal length of the unit rectangle to perform the exposure, and the entire periphery of the wafer is exposed.

Thereafter, the resist film having a unit rectangular shape including the peripheral portion of the wafer is removed by development. The wafer region in which the resist film remaining inside is a region that can be used as a chip.

FIG. 3 shows an example II in which an unexposed area for position confirmation is left in a part of the peripheral portion of a 6-inch wafer, and the entire unit rectangle including the other peripheral portion is exposed. In Fig. 3, 1
Is a wafer having a resist film formed on the entire surface, 11 is a peripheral portion of the wafer, 21 is a mesh overlapping the peripheral portion of the wafer, 41 and 42 are position confirmation points, 22 is a mesh on both sides of the position confirmation point, 51 and 52 are Indicates an unexposed area.

First, the center of the circular portion of the nominal size of the 6-inch wafer is determined by the sensors 71 to 73 described above. Based on the center, position confirmation points 41 and 42 in the X and Y directions for forming an unexposed area are given in advance. The dimensions of the unit rectangle are 5 mm both vertically and horizontally, and the position of the peripheral edge to be exposed is determined according to the nominal size of the 6-inch wafer. The dimensions of the unit rectangle correspond to the dimensions of the chip.

Except for the mesh on both sides of the position confirmation points 41 and 42,
The mesh overlapping with 1 is exposed.

The mesh on both sides of the position confirmation point 41 is
The meshes on both sides are moved in the X direction by 1 mm so as to be separated from each other, and then the meshes are exposed.

After the exposure, if developed, the resist having a width of 2 mm remains in the unexposed areas 51 and 52 including the reference confirmation points 41 and 42. The remaining resist can be used to confirm the center position of the wafer in a later process and to determine the position of the chip on the wafer.

In particular, when element formation is completed on a chip on a wafer, and a chip is selected from the wafer and die-bonded, the center position can be confirmed, so that a chip whose position is coordinated can be selected without fail.

Although the nominal 6-inch wafer has variations in dimensions, the variations are usually about ± 1 mm, so the dimensions of the unit rectangle are set to 5 mm both vertically and horizontally, and the peripheral edge to be exposed at the nominal value is set in advance. There is no practical problem. You can also set the margins for safety.

〔The invention's effect〕

As described above, according to the present invention, it is possible to accurately determine the exposure position of the peripheral portion of the wafer, to increase the number of chips that can be obtained from one wafer, and to prevent chip mixing during die bonding and the like. can do.

The present invention is particularly effective for a large wafer having a large number of chips, and greatly contributes to the manufacture of integrated circuits.

[Brief description of the drawings]

FIG. 1 is a view for explaining the principle of the present invention. FIG. 1 (a) shows a case where the entire periphery of the wafer is exposed, FIG. 1 (b) shows a case where an unexposed area is left on the periphery of the wafer, and FIG. FIG. 3 is a diagram for explaining embodiment I, FIG. 3 is a diagram for explaining embodiment II, and FIG. 4 is a diagram for explaining an apparatus for implementing the present invention.
4 (a) is a step moving mechanism, FIG. 4 (b) is an arrangement of sensors, FIG. 5 is a diagram for explaining Conventional Example I, and FIG. 6 is a diagram for explaining Conventional Example II. is there. In the figure, 1 is a wafer, on which a resit film is formed on the entire surface, 11 is a peripheral portion of the wafer, 2 is a virtual net, 21 is a mesh overlapping the peripheral portion of the wafer, and 22 is a mesh on both sides of the position confirmation point. , 31 and 32 are virtual threads forming a virtual net, 41 and 42 are position confirmation points, 51 and 52 are unexposed areas, 61 is a wafer stage, 62 is a rotation motor, 63 is a table,
64 is a linear pulse motor in the X direction, 65 is a linear pulse motor in the Y direction, 66 is an optical lens system, 67 is a light emitting system, 68 is a light receiving system, 71 to 73 are sensors, and 81 is a moving stage.

Claims (2)

(57) [Claims] 1. A wafer exposure method for dividing a region on a wafer having a resist film formed on the entire surface and exposing each divided region, comprising the steps of: forming a virtual net having a unit rectangle serving as a minimum exposure region as a mesh; When the entire surface of the wafer is hung, a mesh overlapping the peripheral portion of the wafer is exposed over the entire periphery of the peripheral portion, and after the resist film on the peripheral portion of the wafer is removed, a chip formation in which the resist film is left is formed. A method of exposing a wafer, comprising exposing a region. 2. A wafer exposure method for dividing an area on a wafer having a resist film formed on the entire surface and exposing each divided area, comprising: forming a virtual net having a unit rectangle serving as a minimum exposure area as a mesh; A point at which two virtual threads of the virtual net, which pass through substantially the center of the wafer and intersect with the periphery of the wafer when the entire surface of the wafer is crossed, is defined as a position confirmation point. Exposing a mesh overlapping with the periphery of the wafer over the entire periphery of the periphery of the wafer, exposing both sides of the position confirmation point with a gap so as to provide an unexposed area, and exposing the periphery of the wafer to the periphery of the wafer. A method of exposing a wafer, comprising: exposing a chip forming region where the resist film remains after removing the resist film.