JP7443461B2 - Wafer positioning device and chamfering device using the same - Google Patents

Description

The present invention relates to a positioning device for a wafer bonded or molded with glass, resin, or silicon, and a chamfering device using the same.

In recent years, wafers that have been bonded or molded with glass, resin, or silicon have been proposed, and are expected to be used in a variety of applications such as projectors, high-frequency devices, and MEMS-applied products due to the insulation and transparency of the substrate. ing. In addition, a notch called an orientation flat (OF) or notch is provided at a predetermined position on the outer peripheral edge of the wafer as a mark so that the crystal orientation can be determined in a later process. There is.

Therefore, when a wafer having such a configuration is placed into various devices such as a chamfering device for further processing or an inspection device for inspection, it is necessary to position the wafer using the orientation flat as a reference. In particular, due to the demand for improved wafer quality, the processing condition of the wafer end face (edge portion) has become important, and in order to prevent chipping due to handling, the edge portion is chamfered by grinding.

As a technology for positioning a wafer, the wafer is positioned by optically detecting a positioning reference part such as an orientation flat or notch provided on the outer peripheral edge of a disc-shaped wafer, and using this positioning reference part as a reference. It is known to optically measure the outer peripheral edge of the wafer using a line sensor while rotating the wafer after centering the wafer, and is described in Patent Document 1.

Furthermore, when aligning semiconductor wafers that are stacked one above the other, an imaging means such as an infrared camera is used to image an alignment mark formed on the surface of the semiconductor wafer placed on the front side when viewed from the imaging means. is known and described in Patent Document 2.

Japanese Patent Application Publication No. 2011-181849 Japanese Patent Application Publication No. 2015-188042

However, in the above-mentioned conventional technology, when detecting the outer shape of the stacked wafers, the maximum outer shape of the entire wafer is detected, and it is difficult to correctly detect the outer shape corresponding to the bonding surface. In particular, in optical detection, areas other than the focal point may be out of focus due to the finite depth of field, the boundaries of shadows may become blurred due to the spread of the light source, and shadows may be formed around the rounded corners of the object. The edges obtained from actual images are far from ideal edges due to distortion due to local reflections near the edges, making stable measurement difficult.

In particular, when performing alignment using the silicon as a reference for a wafer made of glass and silicon bonded together, problems such as the transparency of the glass part, dust, overlapping, bubbles, waviness, dirt, etc. may occur when using a normal line sensor. Positioning was extremely difficult.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to be able to easily incorporate wafers that have been bonded or molded with glass, resin, or silicon into a general-purpose chamfering device, and to ensure that An object of the present invention is to obtain a wafer positioning device capable of detecting an edge portion and a chamfering device using the same.

The configuration of the present invention for achieving the above object is as follows.
[1] A wafer in which the center of the wafer is detected by detecting the outer peripheral edge of the small-diameter wafer, which is the smaller wafer of a stacked wafer in which two wafers of different sizes, a large-diameter wafer and a small-diameter wafer, are bonded together. The positioning device includes a measurement table on which the laminated wafer is placed and is rotatable while holding the laminated wafer, and a measurement table located near the outer peripheral edge of the small-diameter wafer among the laminated wafers placed thereon. an optical sensor that is installed at a predetermined interval and receives reflected light from the generally disk-shaped surfaces of the small-diameter wafer and the large-diameter wafer; A wafer positioning device characterized in that it does not receive reflected light from a surface that is inclined with respect to a horizontal surface of the wafer.
[2] The positioning device according to [1], wherein the light receiving angle is determined by the shape of an edge of a boundary between the two wafers.
[3] The positioning device according to [1] or [2], wherein only the surface width of the laminated wafer is detected by the reflected light.
[4] A wafer in which the center of the wafer is detected by detecting the outer peripheral edge of the small-diameter wafer, which is the smaller wafer of a stacked wafer in which two wafers of different sizes, a large-diameter wafer and a small-diameter wafer, are bonded together. The positioning device includes a measurement table on which the laminated wafer is placed and is rotatable while holding the laminated wafer, and a measurement table located near the outer peripheral edge of the small-diameter wafer among the laminated wafers placed thereon. an optical sensor that is installed at a predetermined interval and receives reflected light from the generally disk-shaped surfaces of the small-diameter wafer and the large-diameter wafer; The detection sensitivity is narrowed so that the surface that is sloped with respect to the horizontal surface is narrowed, and the optical sensor measures from the horizontal surface of the small-diameter wafer to the outer peripheral edge and the horizontal surface of the large-diameter wafer. , a wafer bonded using at least one of resin and silicon, characterized in that the light receiving angle is 1/10 or less of the angle of the slope portion of the small diameter wafer with respect to the horizontal plane. Wafer positioning device.
[5] In a chamfering device that grinds and chamfers the end face of a laminated wafer in which two wafers of different sizes, a large-diameter wafer and a small-diameter wafer, are bonded together, the laminated wafer is placed and while the laminated wafer is held. A rotatable measurement table is installed at a predetermined distance from the measurement table near the outer peripheral edge of the laminated wafer placed thereon, and receives reflected light from the approximately disc-shaped surface of the laminated wafer. A chamfering device comprising: an optical sensor, wherein a light receiving angle of the optical sensor is narrowed so as not to receive reflected light from a surface that is an inclined surface with respect to a horizontal surface of the small diameter wafer.
[6] The chamfering device according to [5], wherein the light receiving angle is determined by the shape of an edge of a boundary between the two wafers.
[7] The surface and vending device according to [5] or [6], wherein only the surface width of the laminated wafer is detected by the reflected light.

Another configuration of the present invention is to detect the outer peripheral edge of the small-diameter wafer, which is the smaller wafer of a stacked wafer in which two wafers of different sizes, a large-diameter wafer and a small-diameter wafer, are bonded together. In a wafer positioning device that detects a center, a measurement table is provided that is capable of rotating while holding the laminated wafer on which the laminated wafer is placed; an optical sensor that is installed at a predetermined distance from the measurement table and receives reflected light from the generally disk-shaped surfaces of the small-diameter wafer and the large-diameter wafer, and the light-receiving angle of the optical sensor is , the detection sensitivity is narrowed so that the surface that is sloped with respect to the horizontal surface of the small-diameter wafer is narrowed, and the optical sensor measures from the horizontal surface of the small-diameter wafer to the outer peripheral edge and then to the horizontal surface of the large-diameter wafer. be.

Further, in the above, it is preferable that the light receiving angle is 0° to 4°.

Furthermore, in the above, the laminated wafer is a wafer bonded using at least one of glass, resin, and silicon, and the light receiving angle is an angle of the slope portion of the small diameter wafer with respect to a horizontal plane. It is desirable that it be 1/10 or less.

Further, in the above device, it is preferable that the light receiving angle is narrowed so that light is received with respect to a horizontal surface of the small diameter wafer and light is not received with respect to a sloped surface.

Further, in the above device, it is preferable that the light receiving angle is 0° to 2°.

Further, the present invention provides a chamfering device that grinds and chamfers the end face of a stacked wafer in which two wafers of different sizes, a large diameter wafer and a small diameter wafer, are bonded together. A measurement table that can be rotated while being held; and a measurement table that is installed near the outer peripheral edge of the stacked wafer placed thereon at a predetermined distance from the measurement table; an optical sensor that receives light;
The light-receiving angle of the optical sensor is narrowed so that detection sensitivity is reduced on a surface that is inclined with respect to the horizontal surface of the small-diameter wafer, and from the horizontal surface of the small-diameter wafer to the outer peripheral edge and then on the surface of the large-diameter wafer. By measuring up to a horizontal plane with the optical sensor, the outer peripheral edge of the small diameter wafer is detected, and the center of the small diameter wafer is detected.

Furthermore, in the above, the laminated wafer is a wafer bonded using at least one of silicon, glass, and resin, and is a reflective line sensor in which image elements are arranged in a row. The edge position of the inner peripheral part of the silicon is detected by the optical sensor, and the center position of the laminated wafer is determined from the detected edge position, and the wafer on which the laminated wafer is placed during the chamfering process. It is preferable to place the table so that the axis of rotation of the table coincides with the center position.

According to the present invention, it is possible to obtain a wafer positioning device and a chamfering device using the same that can reliably detect the edge of a wafer even if the wafer has been bonded or molded with glass, resin, or silicone. .

A front view showing main parts of a chamfering device according to an embodiment of the present invention A plan view showing main parts of a chamfering device in one embodiment Side view showing detection of the inner edge of a wafer in one embodiment A plan view showing the configuration of a chamfered portion according to an embodiment of the present invention Explanatory diagram showing outer edge detection using a conventional reflective line sensor Explanatory diagram showing measurement of a plane in one embodiment An explanatory diagram showing measurement of an edge portion (slope) in one embodiment A graph showing a comparison of the measurement results of the wafer W height in one embodiment and the conventional method

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a front view showing the main parts of a chamfering device according to an embodiment of the present invention. The chamfering apparatus 10 includes a wafer feeding unit 20, a grindstone rotation unit 50, a wafer supply/storage section (not shown), a wafer cleaning/drying section, a wafer transport means, a controller that controls the operation of each part of the chamfering apparatus, and the like.

On the other hand, there is a strong demand for improving the quality of wafers, and the processing condition of the wafer end face (edge portion) is considered important. In order to prevent chipping due to handling, chamfering is performed by grinding the edges, and chamfering is performed by polishing. In other words, in the manufacturing process, from wafer manufacturing to device manufacturing, quality improvement of edge characteristics has become an essential process.

To perform the chamfering process, position information of the wafer W is required, and the wafer W needs to be accurately placed on the apparatus before the chamfering process. As a preliminary step to the polishing process, the position of the center point of the wafer and the position of the OF of the wafer W must be accurately detected at predetermined positions and placed on the wafer table 34. Furthermore, in normal grinding, the chamfered portion of the wafer W is ground with the main surface of the wafer W perpendicular to the rotation axis of the resin grinding wheel, but so-called helical grinding is performed in which the chamfered portion of the wafer W is ground with the resin grinding wheel tilted. known to do.

In FIG. 1, the wafer feeding unit 20 includes an X-axis base 21 placed on a main body base 11, two X-axis guide rails 22, 22, four X-axis linear guides 23, 23, . . . , a ball screw. It has an X-table 24 that is moved in the X direction in the figure by an X-axis drive mechanism 25 comprising a stepping motor and a stepping motor.

The X table 24 includes two Y-axis guide rails 26, 26, four Y-axis linear guides 27, 27, ..., which are moved in the Y direction in the figure by a Y-axis drive mechanism consisting of a ball screw and a stepping motor (not shown). A Y table 28 is incorporated.

The Y table 28 is guided by two Z-axis guide rails 29, 29 and four Z-axis linear guides (not shown), and is moved in the Z direction in the figure by a Z-axis drive mechanism 30 consisting of a ball screw and a stepping motor. A Z table 31 is incorporated.

A motor 32 and a θ spindle 33 are built into the Z table 31, and a wafer table 34 on which a wafer W (a plate-shaped workpiece) is placed by suction is attached to the θ spindle 33. Then, the wafer table 34 is rotated in the θ direction in the figure around the wafer table rotation axis CW.

Furthermore, a truing grindstone 41 (hereinafter referred to as truer 41) used for truing a grindstone for finish chamfering the peripheral edge of the wafer W is attached to the lower part of the wafer table 34 so as to be coaxial with the wafer table rotation axis CW.

By this wafer feeding unit 20, the wafer W and the truer 41 are rotated in the θ direction in the figure and moved in the X, Y, and Z directions.

The grindstone rotation unit 50 has an outer circumferential rough grinding wheel 52 attached thereto, an outer circumferential grindstone spindle 51 which is rotated around its axis by an outer circumferential grindstone motor (not shown), and an upper outer circumference grinder attached to a turntable 53 disposed above. It has a polishing spindle 54 and an upper outer periphery fine polishing motor 56. Similarly, a lower outer periphery fine polishing spindle 57 and a lower outer periphery fine polishing motor (not shown) are provided on the turntable 53 via a lower fixed frame 59 (partially cut away in FIG. 1).

The upper outer periphery fine polishing spindle 54 and the lower outer periphery fine polishing spindle 57 chamfer the outer periphery of the wafer W with their rotational axes inclined at 3° to 15°, preferably 6° to 10° with respect to the rotational axis of the wafer W. Perform finishing processing. As a result, helical grinding is performed, and although weak grinding marks are generated in the diagonal direction on the chamfered portion of the wafer W, the effect of improving the surface roughness of the chamfered portion compared to normal grinding can be obtained.
The upper outer periphery fine grinding spindle 54 is equipped with an upper outer periphery fine grinding wheel (upper grinding wheel) which is a chamfering grindstone for finishing grinding the outer periphery of the wafer W, and similarly, the lower outer periphery fine grinding spindle 57 is equipped with a lower outer periphery fine grinding wheel. A grindstone (lower grinding wheel) is attached to the upper outer circumferential fine grinding wheel with a gap of about 0.1 to 1 mm, which is smaller than the thickness of the wafer W, so that the rotating shafts thereof are substantially concentric.

Further, the upper outer periphery fine grinding wheel and the lower outer periphery fine grinding wheel are respectively driven by an upper outer periphery fine grinding spindle 54 and a lower outer periphery fine grinding spindle 57 so that their rotation directions are reversed, that is, they rotate in the opposite direction. A grinding groove for processing the wafer W is formed by an upper outer circumference fine grinding wheel and a lower outer circumference fine grinding wheel.

The wafer processing process is performed in the order of block cutting → orientation flat (OF) processing → slicing → chamfering → lapping → etching → donor killer → fine chamfering, and various cleaning methods are used to remove dirt between steps. In block cutting, both ends (top and tail) of the ingot are cut and the outer periphery is ground, and long ones are cut to the appropriate length to create cylindrical "blocks" with a predetermined diameter.

In orientation flat (OF) processing, the crystal orientation is measured and an orientation flat (OF) or "notch" is carved at a predetermined position so that the orientation can be determined in a later process. In slicing, a block is cut into wafers using a dicing saw, wire saw, or internal blade. A block with a diameter of 300 mm is typically cut up to 200 pieces at a time using a multi-wire saw.

In chamfering, if the edge of the wafer remains sharp during slicing, it can easily break or chip during handling such as transportation and alignment in subsequent processing steps, and the fragments can damage or contaminate the wafer surface. To prevent this, the edges of the cut wafers are chamfered using a diamond-coated grinding wheel.

The chamfering process may be performed after the lapping process. At this time, it also includes adjusting the diameter of the outer periphery where there are variations, adjusting the length of the width of the orientation flat (OF), and adjusting the dimensions of a minute cutout called a notch.

FIG. 2 is a plan view showing the main parts of the entire chamfering apparatus 10. The supply and recovery section supplies wafers W to be chamfered from the wafer cassette 70 and collects the chamfered wafers to the wafer cassette 70. This operation is performed by the supply and collection robot 40. A wafer cassette 70 is set on a cassette table 71, and stores a large number of wafers W to be chamfered. The supply and collection robot 40 takes out the wafers W one by one from the wafer cassette 70 and stores the chamfered wafers W into the wafer cassette 70.

The supply and collection robot 40 is equipped with a three-axis rotating arm 80, and the arm 80 is equipped with a suction pad (not shown) on its upper surface. The arm 80 holds the wafer W by vacuum suctioning the back surface of the wafer with a suction pad. That is, the arm 80 of the supply and collection robot 40 can move back and forth, move up and down, and rotate while holding the wafer W, and the wafer W is transferred by combining these operations.

The chamfering device 10 is disposed at the front, and performs all processes for chamfering the outer periphery of the wafer W, that is, from rough machining to finishing machining. The chamfering device 10 includes a wafer feeding unit 20 and a grindstone rotation unit 50.

The transport arm 63 can transport the wafer W between the measurement table 66 and the wafer table 34 via the transport rail 60 while maintaining the posture of the wafer W during transport. For this reason, the transfer arm 63 is capable of suctioning and fixing the wafer W and releasing the suction.

The transfer arm 63 lifts up the wafer W from the table in each process, and also lifts down (places) the wafer W onto the table. Note that the center of the wafer W placed on the measurement table 66 may be slightly eccentric from the rotation center of the measurement table 66 as long as the outer peripheral edge of the wafer W is in a position range that can be measured by the reflective line sensor 1. good.

The transport rail 60 is a laid rail for moving the transport arm 63 in order to transport the wafer W to a predetermined table between each process, for example, between a measurement process and a chamfering process. The wafer table 34 is a table on which the wafer W is placed during the chamfering process. The wafer table 34 firmly holds the wafer W placed thereon so that the wafer W can be polished. For this purpose, the wafer table 34 attracts and fixes the wafer W.

Furthermore, since the wafer table 34 is movable in the X direction and the Y direction on the two-dimensional plane, the amount and direction of eccentricity of the wafer W can be adjusted and the wafer table 34 can be moved when the wafer W is placed. The center position can be aligned with the rotation center of the wafer table 34. Thereby, when the wafer W transferred from the measurement table 66 is placed, the wafer table 34 adjusts the center of the wafer W based on the adjustment data including at least the detected eccentricity amount and eccentric direction of the wafer W. The position can be aligned with the rotation center of the wafer table 34.

In the chamfering process, by aligning the center of the wafer W with the rotation center (center of the rotation axis) of the wafer table 34, the amount of polishing on the wafer W can be reduced during chamfering. This can also lead to a reduction in cycle time in the chamfering process.

FIG. 3 is a diagram illustrating detection of the inner circumference of an edge of a bonded wafer. The center of the wafer W, in which the lower silicon is bonded to the upper glass substrate, is aligned with the rotation center of the wafer table 34. The measurement table 66 is formed into a thin disk shape, and the outer diameter of the disk shape is smaller than the outer diameter of the wafer W.

The measurement table 66 is rotatably controllable. The measurement table 66 rotates with the wafer W placed thereon. The measurement table 66 is capable of measuring the rotation angle, and the reflective line sensor 1 detects the position of the outer circumferential edge around the entire circumference of the wafer W to determine the distance between the outer circumferential edge and the center of rotation. In the reflective line sensor 1, image elements are arranged in a line in the radial direction of the wafer W from the outermost circumference toward the inner circumference.

In FIG. 3, the reflective line sensor 1 is installed near the outer peripheral edge of the wafer W, and is irradiated with light in a direction substantially perpendicular to the substantially disk-shaped surface of the wafer W in the direction of an arrow. The outer peripheral edge of the wafer W is detected by receiving the reflected light. When the outer peripheral edge is detected, the distance from the center of the measurement table 66 is calculated. The calculation is performed by rotating the wafer W, and measurement data can be obtained for each rotation angle over the entire circumference of the wafer W. In addition to the above, the measurement data may also include measurement date and time, an identification number that can identify the wafer W to be measured, measurement results in the measurement table 66 (unable to measure, number of remeasurements), and the like. Based on the measurement data, the center position and radius of the wafer W, the amount of eccentricity from the rotation center of the measurement table 66 with respect to the center of the wafer W, the eccentric direction, etc. are determined.

FIG. 4 is a plan view showing the configuration of the processing section. In a standby state before starting processing, the wafer W held on the wafer table 34 is placed such that the center position of the wafer W determined from the measurement data coincides with the rotation axis of the wafer table 34. At this time, the OF portion of the wafer W is arranged so as to face a predetermined direction.

The outer periphery rough grinding wheel 52 and the outer periphery fine grinding wheel 55 are located at a predetermined distance from the wafer W, respectively. Specifically, the rotation center of the outer periphery rough grinding wheel 52 is placed a predetermined distance away from the rotation center of the wafer W in the Y-axis direction, and the rotation center is placed a predetermined distance apart from the rotation center of the wafer W in the X-axis direction. They are placed a predetermined distance apart.

First, an alignment operation is performed. In this alignment operation, the relative positional relationship between the wafer W held on the wafer table 34 and the outer rough grinding wheel 52 and the outer fine grinding wheel 55 in the vertical direction (Z-axis direction) is adjusted.

When the alignment operation is completed, the outer grindstone spindle 51 is driven. Next, grinding (rough processing) using the outer periphery rough grinding wheel 52 is started. Specifically, a Y-axis motor (not shown) is driven, and the outer grindstone spindle 51 is sent toward the wafer table 34 along the Y-axis direction.

When the outer periphery grindstone spindle 51 is sent toward the wafer table 34, the outer periphery of the wafer W comes into contact with a grinding groove for outer periphery rough grinding formed in the outer periphery rough grinding wheel 52, and the outer periphery of the wafer W is brought into contact with the outer periphery rough grinding wheel 52. 52, and rough processing of chamfering the outer periphery of the wafer W is started.

After rough processing by the outer circumferential rough grinding wheel 52 is started, the wafer W held on the wafer table 34 starts rotating at a constant speed in the direction of the arrow. When this rotation angle, that is, the processing point reaches the OF part where the straight line part is reached, the amount of feed of the outer grindstone spindle 51 in the Y direction toward the wafer table 34 is increased, and the outer grindstone spindle 51 is linearly moved in the X direction to make a straight line. Process the part. After that, when the processing of the straight part is completed, the plate-shaped wafer W held on the wafer table 34 is rotated again in the direction of the arrow at a constant speed, and the remaining circular part is ground and rough-processed by the outer periphery rough grinding wheel 52. end.

A semiconductor substrate that has been bonded or molded using at least one of glass, resin, and silicon is a transparent wafer. Therefore, even if you try to perform alignment based on silicon standards, images with normal line-type sensors may suffer from roundness due to sagging on the outer edge, undulations, dust, overlapping bonding, air bubbles on the glass surface, dirt, and variations due to lighting. Due to this influence, it was extremely difficult to identify the outer peripheral edge.

FIG. 5 is an explanatory diagram showing detection of an outer peripheral edge by the conventional reflective line sensor 1, FIG. 6 is an explanatory diagram showing measurement of a plane according to an embodiment, and FIG. 7 is an explanatory diagram showing an edge portion (slanted surface) according to an embodiment. FIG. 8 is a graph showing a comparison of the measurement results of the respective wafer W heights. In the figure, arrows 1-1 and 1-2 represent one of the image elements in the reflective line sensor 1. Arrow 1-1 indicates that light is irradiated onto the surface of wafer W, and the light reflected from the surface of wafer W is received at a relatively wide light receiving angle as shown by arrow 1-2. Note that the irradiation may not be performed by the reflective line sensor 1, but by illumination at the measurement location.

The inner periphery of the silicon surface W-2 of the wafer W is approximately horizontal, but it becomes sloped toward the outer periphery, and its corners are sagging and rounded. Furthermore, it is difficult to identify the edge due to the way the sheets are bonded together, air bubbles on the glass surface, dirt, etc., and the measurement results are as shown by the dotted line in FIG. 8, for example. In FIG. 8, the vertical axis indicates the height of the wafer W in the thickness direction measured by the reflective line sensor 1, and the horizontal axis indicates the position of the wafer W in the radial direction.

The horizontal line at the right end of FIG. 8 is the height of the horizontal plane of the silicon surface W-2, and the horizontal line at the left end is the height of the glass surface W-1. The dotted line portion is the boundary between the silicon surface W-2 and the glass surface W-1, and the shape of the sloped portion of the silicon surface W-2 is directly reflected. Then, it becomes irregular due to the influence of dust and overlapping, and the boundary becomes unclear.

In this state, in order to specify the edge of the silicon surface W-2, which is the boundary, it is impossible to determine unless a height threshold is determined at the dotted line portion. However, since the wafer is transparent, it is greatly affected by the irradiation light or variations in illumination, and the height data values in the figure are extremely unstable.

6 and 7 show an improved example of the above, in which the margin angle at which the reflective line sensor 1 can receive light, that is, the light receiving angle φ, is narrowed by the slit 1-3 arranged at the front in the light receiving direction. It is. FIG. 6 shows a case where the measurement surface is horizontal, and although the light receiving angle φ is small, the measurement is performed in the same way as in the state of FIG. 5 where the angle is not narrowed. FIG. 7 shows measurement at a sloped portion, and the reflected light is blocked by a slit 1-3, as indicated by an arrow 1-2. That is, the reflected light from the slope that exceeds the margin angle at which light can be received with respect to the horizontal surface of the wafer W is not detected or is narrowed so that the detection sensitivity is reduced. Alternatively, the light receiving angle φ may be narrowed so that the reflected light from the horizontal surface is received but the reflected light from the slope is not received.

As a result, only the substantially horizontal portion of the wafer W, that is, the surface width, can be detected. The light receiving angle φ is determined based on the actual state of the wafer W that has been bonded or molded with glass, resin, or silicon, such as the angle and roundness of the edge of the boundary between the silicon surface W-2 and the glass surface W-1. . As a result of various experiments, good results were obtained by setting the light receiving angle φ to 0° to 4°, preferably 0° to 2°.

Note that the light receiving angle φ=0° means that the reflected light from the horizontal surface of the wafer W directly faces the reflective line sensor 1, and the center of the reflective line sensor 1 receiving the light coincides (the state shown in FIG. 6). It means. In addition, since the height of the slope part of the bonded wafer W decreases from the inner circumference to the outer circumference, the light reception angle of the horizontal part is 0° to 4° in the slope direction, that is, the light reception angle φ= The angle may be 0° to 4°, preferably 0° to 2°. Alternatively, the light reception angle φ at the horizontal portion may be set to -1° to 4°, preferably -1° to 2°, by allowing a margin for the light receiving angle φ, and it may be determined based on the output, image, etc. actually obtained. good.

Due to the actual situation that the angle of the sloped part on the outer periphery of the bonded wafer is 20° to 30° with respect to the horizontal plane, in that case, the light receiving angle φ is set to 2° so that it is 1/10 or less of the angle of the sloped part. The measurement results when narrowed to below are shown by the solid line in FIG. The horizontal line at the right end of FIG. 8 is the height of the horizontal plane of the silicon surface W-2, and the horizontal line at the left end is the height of the glass surface W-1. The light receiving angle φ of the reflective line sensor 1 is narrowed so that detection sensitivity is reduced on a surface that is inclined with respect to the horizontal surface of the wafer W.

At the boundary between the silicon surface W-2 and the glass surface W-1, when the light receiving angle φ is 2 degrees or less, the detection sensitivity is extremely low, and almost no light is output. In other words, only the width of the horizontal and flat surface of the wafer W is output. Accordingly, when aligning the wafer W using the silicon reference, it is sufficient to detect the edge position as the outer peripheral edge of the wafer W within the output range of the silicon surface W-2.

When the outer peripheral edge of the wafer W is detected, the distance from the center of the measurement table 66 is determined, and the wafer W is rotated to obtain measurement data for each rotation angle over the entire circumference of the wafer W. Furthermore, based on the measurement data, the center position of the wafer W can be adjusted without being affected by roundness, undulation, dust, overlapping bonding, air bubbles on the glass surface, dirt, variations due to lighting, etc. due to sagging of the outer peripheral edge. The edge position of the inner circumference can be found.

The experimental results show that by setting the light receiving angle φ to 0° to 4°, preferably 0° to 2°, alignment accuracy can be reduced to ±0.1 mm or less, and there is no problem in practical use. It has been confirmed. In addition, although it is an optical detection method, it is stable without being affected by out-of-focus areas other than the focal position, blurring of boundaries due to spread of the light source, shadows at rounded corners, and distortions due to local reflections near edges. edge detection is possible.

Although detection of the outer peripheral edge has been described using a reflective line sensor 1 in which image elements are arranged in a row, it is also possible to use an area sensor or a reflective laser sensor in which image elements are arranged in a row and a row and are arranged two-dimensionally. Similarly, stable edge detection is possible if the optical sensor, such as a photoelectric sensor, is configured to have a narrow light receiving angle φ so that detection is performed only in a limited area of the optical axis.

The radius of the wafer W is determined from the edge position of the inner circumference of the silicon, and it is determined whether the difference in the measurement data for each rotation angle over the entire circumference is within a predetermined threshold. Then, measurement data determined to be within a predetermined threshold is extracted as a valid data group.

Next, by finding the center position of the wafer W from the valid data group, extra errors caused by irregular factors such as foreign objects or chips attached to the outer peripheral edge of the wafer W, bubbles in the glass part, undulations, dirt, etc. can be excluded. be able to. Then, the center of the wafer can be determined with higher accuracy from the measurement data for the outer peripheral edge of the wafer W.

W...Wafer, W-1...Glass surface, W-2...Silicon surface, 1...Reflection type line sensor, 1-1, 1-2...Arrow, 1-3...Slit, 10...Chamfering device, 11...Main body base , 20... Wafer feed unit, 21... X-axis base, 22... X-axis guide rail, 23... X-axis linear guide, 24... X-table, 25... X-axis drive mechanism, 26... Y-axis guide rail, 27... Y-axis Linear guide, 28...Y table, 29...Z-axis guide rail, 30...Z-axis drive mechanism, 31...Z table, 32...motor, 33...spindle, 34...wafer table, 40...supply and recovery robot, 41...truer, 50... Grinding wheel rotation unit, 51... Outer circumference grinding wheel spindle, 52... Outer circumference rough grinding wheel, 53... Turntable, 54... Upper outer circumference fine grinding spindle, 55... Outer circumference fine grinding wheel, 55-1... Upper outer circumference fine grinding wheel (upper) (grinding wheel), 55-2...Lower outer periphery precision grinding wheel (lower grinding wheel), 56...Upper outer periphery precision grinding motor, 57...Lower outer periphery precision grinding spindle, 59...Lower fixed frame, 60...Transportation rail, 63...Transportation arm , 66...Measurement table, 70...Wafer cassette, 71...Cassette table, 80...Arm

Claims (4)

A wafer positioning device that detects the center of the wafer by detecting the outer peripheral edge of the small-diameter wafer, which is the smaller wafer of a stacked wafer in which two wafers of different sizes, a large-diameter wafer and a small-diameter wafer, are bonded together. In,
a measurement table on which the laminated wafer is placed and is rotatable while holding the laminated wafer;
Among the laminated wafers placed thereon, the small-diameter wafer is placed near the outer circumferential edge of the small-diameter wafer at a predetermined distance from the measurement table, and reflects light from the approximately disc-shaped surfaces of the small-diameter wafer and the large-diameter wafer. an optical sensor that receives light;
Equipped with
The light receiving angle of the optical sensor is narrowed so as not to receive reflected light from a surface that is an inclined surface with respect to a horizontal surface of the small diameter wafer ,
A wafer positioning device , wherein the light receiving angle is determined by the shape of an edge of a boundary between the two wafers . The positioning device according to claim 1 , wherein only the surface width of the laminated wafer is detected by the reflected light. In a chamfering device that grinds and chamfers the end face of a stacked wafer in which two wafers of different sizes, a large-diameter wafer and a small-diameter wafer, are bonded together,
a measurement table on which the laminated wafer is placed and is rotatable while holding the laminated wafer;
an optical sensor that is installed near the outer peripheral edge of the stacked wafer placed thereon at a predetermined distance from the measurement table and receives reflected light from a substantially disc-shaped surface of the stacked wafer;
Equipped with
The light receiving angle of the optical sensor is narrowed so as not to receive reflected light from a surface that is an inclined surface with respect to a horizontal surface of the small diameter wafer ,
A chamfering device in which the light receiving angle is determined by the shape of an edge of a boundary between the two wafers . The chamfering apparatus according to claim 3 , wherein only the surface width of the laminated wafer is detected by the reflected light.