JP2016153154A - Wafer positioning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer positioning method capable of positioning a wafer at a predetermined position on a chuck table, by using a conventional mechanism, without using imaging means for positioning or a positioning mechanism.SOLUTION: By rotating a chuck table 10, a Y-coordinate of a center position of a wafer W is matched with a Y-coordinate of a center position of a holding surface 12 of the chuck table 10. While the wafer W is separated from the chuck table 10, the chuck table 10 is moved in an X-axis direction to match an X-coordinate of the center position of the holding surface 12 of the chuck table 10 with an X-coordinate of the center position of the wafer W.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a wafer alignment method.

  When a semiconductor wafer is divided into individual chips, it is divided by various processing methods, one of which is a processing method called DBG (Dicing Before Grinding). A groove or a modified layer is formed by a cutting device or a laser processing device along a planned division line of the semiconductor wafer, and the semiconductor wafer is ground from the back surface to the finished thickness to be divided into individual chips. Since chips generated at the edge of the chip are very small, a chip with high bending strength can be obtained. In such a processing method, it is necessary to position the wafer at a predetermined position and orientation when the division line is determined by a cutting device or a laser processing device. Normally, wafers that are loaded into a cutting machine or laser processing machine are supported by tape in a predetermined orientation and position on an annular frame, so the position and orientation of the wafer are automatically aligned when they are loaded onto the chuck table. Has been. When processing a single wafer that does not use an annular frame, an alignment mechanism for performing alignment before loading into the chuck table is provided in the apparatus (Patent Document 1).

JP 2005-11917 A Japanese Patent Application No. 2013-260534

  However, there has been a problem that the apparatus main body is increased in size by the alignment mechanism or the manufacturing cost of the alignment mechanism is increased. Also, the wafer carried out from the cassette held by the carry-in / out means is imaged by the image-taking means for alignment, the orientation and position of the wafer on the carry-in / out means are detected, and the carry-in / out means moves in the Y-axis direction. A method of positioning the center of the wafer at the center of the holding surface of the chuck table using a chuck table that moves in the X-axis direction and rotates about the Z-axis direction as a rotation axis has also been devised (Patent Document 2). However, in this case as well, it is necessary to newly provide an imaging means for alignment, and there is a problem of an increase in cost.

  In view of the above, the present invention has been made in view of the above, and the position of the wafer is set to a predetermined value on the chuck table by using a conventional mechanism without using an imaging means or an alignment mechanism for alignment. It is an object of the present invention to provide a wafer alignment method capable of being aligned.

  In order to solve the above-mentioned problems and achieve the object, the present invention provides a chuck table for holding a wafer on a holding surface, a rotating means for rotating the chuck table on a rotating shaft orthogonal to the holding surface, and the chuck A processing means capable of moving in the Y-axis direction for processing the wafer held on the table, an imaging means capable of moving in the Y-axis direction for imaging the wafer held on the chuck table, and the chuck table on the Y-axis In a processing apparatus, comprising: a processing feed means for processing and feeding in an X-axis direction orthogonal to the direction; and a loading / unloading means for loading and unloading a wafer to and from the chuck table. A method for aligning a wafer positioned at the center of a table, the wafer being held on the chuck table by the imaging means A coordinate acquisition step for imaging the peripheral edge and acquiring coordinates of three or more outer peripheral edges, a center position determining step for determining the coordinates of the center position of the wafer from the acquired coordinates, and a central position of the holding surface stored in advance Based on the coordinates and the coordinates of the center position of the wafer, the chuck table is rotated by the rotating means so that the Y coordinate of the center position of the wafer coincides with the Y coordinate of the center position of the holding surface. Unloading the wafer from the chuck table, driving the processing feed means to match the X coordinate of the center position of the holding surface with the X coordinate of the center position of the wafer, and then placing the wafer on the chuck table again. And an alignment step of aligning the center of the wafer with the center of the holding surface.

  Further, in the wafer alignment method, after the mark indicating the crystal orientation of the wafer is imaged by an imaging means, the orientation detection step of detecting the orientation of the mark, the orientation detection step and the alignment step are performed. It is preferable to further include a crystal orientation alignment step of positioning the mark at a predetermined position by the rotating means.

  According to the wafer alignment method of the present invention, after the chuck table is rotated so that the Y coordinate of the center position of the wafer coincides with the Y coordinate of the center position of the holding surface of the chuck table, it is removed from the chuck table by the loading / unloading means. After unloading the wafer and driving the processing feed means to make the X coordinate of the center position of the holding surface coincide with the X coordinate of the center position of the wafer, the wafer is placed on the chuck table again, so that the center of the holding surface The center of the wafer is aligned. As a result, the center position of the wafer can be aligned with the center position of the holding surface of the chuck table by using a conventional mechanism without using an image pickup means or an alignment mechanism for alignment.

FIG. 1 is a perspective view showing a configuration example of a processing apparatus. FIG. 2 is a side view showing an example of wafer movement. FIG. 3 is a flowchart showing an operation example of the processing apparatus. FIG. 4 is a top view showing coordinate acquisition and center position determination. FIG. 5 is a top view showing alignment in the Y-axis direction. FIG. 6 is a top view showing unloading of the wafer and alignment in the X-axis direction. FIG. 7 is a top view showing the end of alignment in the X-axis direction. FIG. 8 is a top view showing alignment of crystal orientations.

  DESCRIPTION OF EMBODIMENTS Embodiments (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments. The constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the structures described below can be combined as appropriate. Various omissions, substitutions, or changes in the configuration can be made without departing from the scope of the present invention.

Embodiment
The processing apparatus according to the embodiment will be described. FIG. 1 is a perspective view illustrating a configuration example of a processing apparatus. FIG. 2 is a side view showing an example of wafer movement.

  The processing apparatus 1 is a facing dual dicer and cuts the wafer W. The processing apparatus 1 includes a chuck table 10, a rotating unit 11, a processing unit 20, a first portal frame 30, an imaging unit 40, a processing feeding unit 50, an indexing feeding unit 60, and a cutting feeding unit 70. It has.

  The wafer W is various processing materials such as a semiconductor wafer or an optical device wafer on which a semiconductor device or an optical device is formed, an inorganic material substrate, a ductile resin material substrate, a ceramic substrate, or a glass plate. The wafer W is formed in a disk shape, and devices such as ICs and LSIs are formed in a large number of regions arranged in a lattice pattern on the surface WS. A notch (mark) N representing the crystal orientation is provided on the outer periphery of the wafer W. Instead of the notch N, an orientation flat in which the outer peripheral edge WE of the wafer W is cut out linearly may be used.

  Here, the X-axis direction is a direction in which the wafer W held on the chuck table 10 is processed and fed. The Y-axis direction is a direction in which the index feeding means 60 is indexed and fed to the wafer W held on the chuck table 10 and orthogonal to the X-axis direction on the same horizontal plane. The Z-axis direction is a direction orthogonal to the X-axis direction and the Y-axis direction, that is, a vertical direction.

  The chuck table 10 is disposed on the upper surface of the apparatus main body 2 so as to be movable along an opening 2 a provided in the X-axis direction. The chuck table 10 includes a holding surface 12. The chuck table 10 is formed in a disk shape, and is rotated by a rotating unit 11 on a rotation axis orthogonal to the holding surface 12. The holding surface 12 holds the wafer W. The holding surface 12 is the upper end surface in the vertical direction of the chuck table 10 and is formed flat with respect to the horizontal plane. The holding surface 12 is made of, for example, porous ceramic or the like, and sucks and holds the wafer W by a negative pressure of a vacuum suction source (not shown).

  The processing means 20 processes the wafer W held on the chuck table 10. Two processing means 20 are arranged opposite to each other in the Y-axis direction. The processing means 20 is connected to the portal frame 30 erected on the apparatus main body 2 so as to straddle the opening 2 a provided on the upper surface of the apparatus main body 2 in the Y-axis direction via the index feeding means 60 and the cutting feed means 70. Is fixed. The processing means 20 includes a cutting blade 21, a spindle 22, and a housing 23. The cutting blade 21 is a cutting grindstone formed in an extremely thin disk shape and in an annular shape. The spindle 22 is detachably mounted with a cutting blade 21 at its tip. The housing 23 has a drive source such as a motor (not shown), and supports the spindle 22 so as to be rotatable around a rotation axis in the Y-axis direction. The spindle 22 is rotated at a high speed, and the wafer W is cut by the cutting blade 21.

  The image pickup means 40 picks up an image of the wafer W held on the chuck table 10 and is, for example, a camera using a CCD (Charge Coupled Device) image sensor. The imaging means 40 is fixed to the first portal frame 30 via the index feeding means 60 and the cut feeding means 70. The imaging unit 40 images the wafer W and generates image data for alignment adjustment of the pair of processing units 20, image data for determining the center position of the wafer W, and the like.

  The processing feed means 50 is for moving the chuck table 10 and the processing means 20 relative to each other in the X-axis direction. For example, as shown in FIG. 2, the processing feed means 50 has a drive source such as a ball screw 51 extending in the X-axis direction or a pulse motor (not shown), and an X-axis moving base that supports the chuck table 10. The stage 52 is moved in the X-axis direction.

  The index feeding means 60 is configured to relatively move the chuck table 10, the processing means 20, and the imaging means 40 in the Y-axis direction. For example, the indexing and feeding means 60 has drive sources such as a ball screw 61 and a pulse motor 62 that extend in the Y-axis direction, and moves the processing means 20 and the imaging means 40 in the Y-axis direction.

  The cutting feed means 70 moves the processing means 20 and the imaging means 40 in the Z-axis direction orthogonal to the holding surface 12 of the chuck table 10. For example, the cutting feed means 70 has drive sources such as a ball screw 71 and a pulse motor 72 that extend in the Z-axis direction, and moves the processing means 20 and the imaging means 40 in the Z-axis direction.

  The processing apparatus 1 further includes a cassette 80, a cassette mounting table 90, a cassette carry-in / out means 100, a first transport means 110, a second portal frame 120, a second transport means 130, and a cleaning means 140. The control means 150 is provided.

  The cassette 80 is placed on the cassette mounting table 90 and stores a plurality of wafers W. The cassette mounting table 90 is disposed in front of the second portal frame 120 and is moved up and down in the Z-axis direction by a cassette elevator (not shown) disposed in the apparatus main body 2.

  The cassette carry-in / out means 100 is for carrying out the wafer W from the cassette 80 and carrying the wafer W into the cassette 80. For example, the cassette loading / unloading means 100 is formed in a forked shape, and includes a holding hand 101 that holds the wafer W, and a driving source such as a ball screw and a pulse motor (not shown) that extends in the Y-axis direction. The holding hand 101 is moved in the Y-axis direction.

  The first transfer unit 110 functions as a loading / unloading unit, and transfers the wafer W unloaded from the cassette 80 by the cassette loading / unloading unit 100 to the chuck table 10. The first transport means 110 is disposed on a second portal frame 120 that is erected on the apparatus main body 2 so as to straddle the opening 2a of the apparatus main body 2 in the Y-axis direction. The first transport unit 110 includes a linear motion mechanism 111, a support part 112, an expansion / contraction mechanism 113, and a suction part 114. The linear motion mechanism 111 is, for example, a slider driven by a ball screw or a rotating belt, and is arranged from one end to the center of the second portal frame 120 in the Y-axis direction. The support portion 112 is formed in an L shape, one end of which is fixed to the slider 111a of the linear motion mechanism 111, and the telescopic mechanism 113 is disposed at the other end. The expansion / contraction mechanism 113 has a suction portion 114 fixed to the tip thereof, and moves the suction portion 114 in the Z-axis direction. The expansion / contraction mechanism 113 is, for example, an air actuator that expands and contracts in the Z-axis direction, and moves the suction unit 114 from the position of the surface WS of the wafer W held on the chuck table 10 to a predetermined height. The suction unit 114 holds the wafer W by sucking the surface WS of the wafer W with a suction pad (not shown).

  The second transfer unit 130 functions as a loading / unloading unit, and transfers the processed wafer W placed on the chuck table 10 to the cleaning unit 140. The second transfer means 130 is for transferring the wafer W cleaned by the cleaning means 140 to the cassette 80. The second transport unit 130 is disposed on the second portal frame 120 and includes a linear motion mechanism 131, a support part 132, an expansion / contraction mechanism 133, and a suction part 134. The linear motion mechanism 131 is, for example, a slider driven by a ball screw or a rotating belt, and is disposed from one end to the other end of the second portal frame 120 in the Y-axis direction. The support portion 132 is formed in an L shape, and one end thereof is fixed to a slider (not shown) of the linear motion mechanism 131, and an expansion / contraction mechanism 133 is disposed at the other end. The expansion / contraction mechanism 133 has a suction portion 134 fixed to the tip thereof, and moves the suction portion 134 in the Z-axis direction. The expansion / contraction mechanism 133 is, for example, an air actuator that expands and contracts in the Z-axis direction, and moves the suction unit 134 from the position of the surface WS of the wafer W placed on the chuck table 10 to a predetermined height. The suction unit 134 holds the wafer W by sucking the surface WS of the wafer W with a suction pad (not shown).

  The cleaning means 140 is for cleaning and drying the wafer W processed by the processing means 20. The cleaning unit 140 includes a spinner table 141 that holds the wafer W. The cleaning unit 140 holds the wafer W on the spinner table 141 and rotates the wafer W at a high speed, and sprays and cleans the cleaning liquid such as pure water toward the wafer W, and clean air (compressed air) or the like is applied to the wafer W. Spray toward and dry.

  The control means 150 controls each component of the processing apparatus 1. For example, the control unit 150 is connected to a drive circuit (not shown) that drives the pulse motors of the machining feed unit 50, the index feed unit 60, and the cutting feed unit 70, and controls the drive circuit to position the chuck table 10 in the X-axis direction. Further, the position of the processing means 20 in the Y-axis direction and the Z-axis direction is determined.

  Next, a method for aligning the wafer W using the processing apparatus 1 will be described. FIG. 3 is a flowchart showing an operation example of the processing apparatus. FIG. 4 is a top view showing coordinate acquisition and center position determination. FIG. 5 is a top view showing alignment in the Y-axis direction. FIG. 6 is a top view showing unloading of the wafer and alignment in the X-axis direction. FIG. 7 is a top view showing the end of alignment in the X-axis direction. FIG. 8 is a top view showing alignment of crystal orientations.

  First, the wafer W is transferred to the chuck table 10 (step S1 shown in FIG. 3). For example, the control unit 150 controls the cassette loading / unloading unit 100 to unload the wafer W to be processed from the cassette 80. Then, the control unit 150 controls the second transfer unit 130 to transfer the wafer W unloaded by the cassette loading / unloading unit 110 to the chuck table 10 and hold the wafer W on the chuck table 10.

  Next, the control unit 150 images the outer peripheral edge WE of the wafer W held on the chuck table 10 by the imaging unit 40, and acquires the coordinates of the outer peripheral edge WE at three or more locations (step S2). For example, the imaging unit 40 images the outer peripheral edge WE of the wafer W held on the chuck table 10 in a state where the chuck table 10 is stopped, and outputs the image data to the control unit 150. Since the imaging means 40 also images the notch N formed in the outer peripheral edge WE, when the position of the notch N can be estimated, the outer peripheral edge WE in a preset range is imaged. Further, when the position of the notch N cannot be estimated, the imaging unit 40 images the outer peripheral edge WE until the notch N can be detected in the entire range of the outer peripheral edge WE or a certain range. The control means 150 acquires three coordinates Q1 to Q3 on the outer peripheral edge WE of the wafer W from the image data input from the imaging means 40 as shown in FIG. The control unit 150 also acquires information on the notch N on the outer peripheral edge WE of the wafer W at the same time.

  Next, the control means 150 calculates the center position of the wafer W from the coordinates Q1 to Q3 (step S3). For example, the control means 150 obtains a vertical bisector L1 of a line segment connecting the coordinates Q1 and the coordinates Q2. Further, the control unit 150 obtains a vertical bisector L2 of a line segment connecting the coordinates Q2 and the coordinates Q3. Then, the control unit 150 obtains the coordinates C of the intersection where the vertical bisector L1 and the vertical bisector L2 intersect. The coordinate C is a coordinate indicating the center position of the wafer W held on the chuck table 10. 4 is a coordinate indicating the center position of the holding surface 12 of the chuck table 10, and is stored in advance in a storage means (not shown). Further, a wafer W ′ indicated by a broken line in FIG. 4 shows a state when the center position of the wafer W is aligned with the center position of the holding surface 12 of the chuck table 10.

  Next, the control unit 150 performs alignment in the Y-axis direction (Y coordinate) (step S4). For example, as shown in FIG. 5, the control unit 150 rotates the chuck table 10 clockwise, sets the Y coordinate of the coordinate C indicating the center position of the wafer W, and the center position of the holding surface 12 of the chuck table 10. Match the Y coordinate of the indicated coordinate P. That is, the chuck table 10 is rotated clockwise so that the coordinate C of the wafer W is placed on an extension line in the X-axis direction passing through the coordinate P of the chuck table 10.

  Next, the control unit 150 performs alignment in the X-axis direction (X coordinate) (step S5). For example, the control unit 150 controls the first transfer unit 110 to suck and hold the wafer W by the suction unit 114, and as shown in FIG. 6, the wafer W is positioned above the holding surface 12 of the chuck table 10 in the Z-axis direction. Move. Then, the control means 150 moves the chuck table 10 in the X-axis direction, and changes the X coordinate of the coordinate P indicating the center position of the holding surface 12 of the chuck table 10 to the center position of the wafer W as shown in FIG. It is made to correspond with the X coordinate of the coordinate C which shows. Then, the control unit 150 controls the first transfer unit 110 to move the wafer W downward in the Z-axis direction and suck and hold the wafer W on the holding surface 12 of the chuck table 10. As a result, the wafer W is held on the chuck table 10 in a state where the center position of the wafer W matches the center position of the holding surface 12 of the chuck table 10.

  Next, the control means 150 adjusts the position of the crystal orientation of the wafer W (step S6). For example, the control unit 150 controls the rotation unit 11 of the chuck table 10 based on the acquired information about the notch N, and rotates the chuck table 10 counterclockwise as shown in FIG. Is positioned at a predetermined position, and the orientation of the crystal orientation is adjusted to a predetermined direction. Then, the control unit 150 controls the processing unit 20 to cut the wafer W held on the chuck table 10, and after the cutting process, the cleaning unit 140 cleans and dries the wafer W. Then, the control unit 150 controls the second transfer unit 130 and the cassette carry-in / out unit 100 to store the wafer W in the cassette 80.

  As described above, according to the wafer alignment method according to the embodiment, the chuck table 10 is rotated so that the Y coordinate of the center position of the wafer W matches the Y coordinate of the center position of the holding surface 12 of the chuck table 10. In a state where the wafer W is separated from the chuck table 10, the chuck table 10 is moved in the X axis direction so that the X coordinate of the center position of the holding surface 12 of the chuck table 10 matches the X coordinate of the center position of the wafer W. Is. As a result, the center position of the wafer W can be aligned with the center position of the holding surface 12 of the chuck table W by using a conventional mechanism without using an image pickup means or an alignment mechanism for alignment. In addition, the orientation of the crystal orientation can be adjusted using a conventional mechanism. Therefore, the processing apparatus 1 can be reduced in size, and the cost for manufacturing the processing apparatus 1 can be reduced.

  Further, as in the prior art, when the correction of the wafer W in the Y-axis direction is performed by the first transfer unit 110, the end point of the movement axis of the first transfer unit 110 that moves in the Y-axis direction is the center of the chuck table 10. When set near, there is a limit to the amount of movement in the Y-axis direction. For this reason, it becomes impossible to correct the wafer W whose center position is shifted beyond the limit, but in the present invention, the limit can be exceeded by using the rotating means 11 for correction in the Y-axis direction.

DESCRIPTION OF SYMBOLS 1 Processing apparatus 10 Chuck table 11 Rotating means 12 Holding surface 20 Processing means 40 Imaging means 50 Processing feed means 60 Indexing feed means 70 Cutting feed means 80 Cassette 100 Cassette carrying in / out means 110 First transport means 130 Second transport means 140 Cleaning means 150 Control means N Notch P, C, Q1-Q3 Coordinate W Wafer WE Outer peripheral edge WS Surface

Claims (2)

A chuck table for holding a wafer by a holding surface, a rotating means for rotating the chuck table by a rotation axis orthogonal to the holding surface, and a processing means movable in the Y-axis direction for processing the wafer held by the chuck table An imaging means that can move in the Y-axis direction for imaging the wafer held by the chuck table, a processing feed means for processing-feeding the chuck table in the X-axis direction orthogonal to the Y-axis direction, and the chuck And a loading / unloading means for unloading the wafer to and from the chuck table, and a wafer alignment method for positioning the wafer at the center of the chuck table,
A coordinate acquisition step of imaging the outer peripheral edge of the wafer held on the chuck table by the imaging means and acquiring the coordinates of the outer peripheral edge at three or more locations;
A center position determining step for determining coordinates of the center position of the wafer from the acquired coordinates;
Based on the coordinates of the center position of the holding surface and the coordinates of the center position of the wafer stored in advance, the chuck table is rotated by the rotating means, and the Y coordinate of the center position of the wafer is set as the Y coordinate of the center position of the holding surface. After matching, the wafer is unloaded from the chuck table by the loading / unloading means, the processing feed means is driven to match the X coordinate of the center position of the holding surface with the X coordinate of the center position of the wafer, and then again. An alignment step of aligning the center of the wafer with the center of the holding surface by placing the wafer on the chuck table. An orientation detection step in which a mark indicating the crystal orientation of the wafer is imaged by an imaging means, and the orientation of the mark is detected;
The wafer alignment method according to claim 1, further comprising: a crystal orientation alignment step of positioning the mark at a predetermined position by the rotation unit after performing the orientation detection step and the alignment step. Method.

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