JP2020055063A - Grinding method and grinding device - Google Patents

Abstract

To facilitate confirmation of whether an already ground wafer is ground into a desired thickness.SOLUTION: A wafer W is ground into a prescribed thickness while making a first detection terminal 60 contact a reference surface 51a being an upper surface of a frame body 51 of a holding table 5 and while making a second detection terminal for thickness measurement contact a back side Wb of the wafer W having a protecting member T arranged thereon. Thereafter, weight measurement means 7 measures total weight of the wafer W and the protecting member T and a comparison part 81 compares the measured weight with preset weight memorized in advance in a weight memorizing part 80 of control means 8 to determine whether or not the wafer is ground into a desired thickness. If a result of the comparison of the weight shows that the thickness is abnormal, alarm generating means 9 receives the result of the comparison performed by the comparison part 81 and generates an alarm, so that an operator and the like can recognize that the thickness is abnormal.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a grinding method and a grinding device.

  During grinding of the back surface of a wafer such as a semiconductor wafer, as shown in Patent Document 1, detection terminals are brought into contact with the holding surface of the holding table and the back surface of the wafer to reduce the thickness of the wafer to a desired thickness. Then, the thickness of the wafer is measured (for example, see Patent Document 1). Actually, in order to protect the device on the surface, a protective member such as a protective tape is stuck on the surface of the wafer, and in the grinding device, the protective member side is held by a holding table, and during the grinding, the protective member is And the total thickness of the wafer.

JP 2000-006018 A

  However, when a protective member having a thickness different from that of the protective member to be used is stuck to the wafer and the wafer is ground, the wafer is not desired even if the total thickness of the protective member and the wafer becomes a predetermined thickness. Is thinned to a thickness different from the thickness of It is unacceptable to remove the protective member from the thinned wafer after grinding and measure the thickness of the single wafer because the wafer may be damaged. The wafer after grinding is generally diced, picked up, and mounted on a substrate. There is also a possibility that a problem caused by the above may occur. An object of the present invention is to make it possible to easily determine whether a wafer has been ground to a desired thickness after grinding.

  The present invention is a grinding method for grinding a back surface of a wafer to reduce the thickness to a desired thickness, and a protective member arranging step of arranging a predetermined protective member on the front surface of the wafer, and via the protective member A holding step of holding the wafer on the holding table to expose the back surface of the wafer, and after performing the holding step, contacting the detection terminals with the upper surface of the holding table and the back surface of the wafer, respectively, to thereby form the protection member and the wafer. A grinding step of grinding the back surface of the wafer to a predetermined thickness while measuring the total thickness of the wafer, and a weight measurement for measuring the weight of the wafer provided with the protection member after performing the grinding step And a confirmation step of confirming whether or not the wafer has been thinned to the desired thickness based on the weight measured in the weight measurement step.

  Further, the present invention is a grinding apparatus for grinding a back surface of a wafer having a protection member disposed on a front surface, the holding table including a holding surface for holding a wafer via the protection member, and a holding table held by the holding table. Grinding means having a grinding wheel for grinding the processed wafer, a first detection terminal for detecting the height position of the holding surface by contacting the holding surface, and contacting the back surface of the wafer held by the holding table And a thickness measuring means having a second detection terminal for detecting the height position of the back surface, and a weight measuring means for measuring the weight of the wafer provided with the protective member after the grinding. Device.

  The control device includes a control unit that controls at least the grinding unit, and the control unit stores, as a predetermined weight, a weight when the wafer on which the predetermined protection member is provided is thinned to a desired thickness. A weight storage unit, and a comparison unit that compares the weight of the wafer provided with the protective member after grinding measured by the weight measuring unit with the predetermined weight. It is preferable to further include a warning transmission unit that transmits a warning when the weight compared by the comparison unit is out of the allowable value.

  In the present invention, it is possible to easily confirm whether the wafer has been thinned to a desired thickness by measuring the weight of the wafer provided with the protective member measured after the grinding.

It is a perspective view showing an example of a wafer. It is a perspective view which shows a protection member arrangement | positioning step. It is a perspective view showing the whole grinding device. It is sectional drawing which shows the time of a holding step. It is sectional drawing of the holding table and grinding means at the time of grinding. It is a front view of the weight measuring means at the time of weight measurement.

1 Protecting Member Arranging Step As shown in FIG. 1, the wafer W to be ground is, for example, a semiconductor wafer having a plurality of devices D on a surface Wa, and is divided along a division line L after the grinding. As shown in FIG. 2, before the grinding, a protection member T is provided on the surface Wa of the wafer W for the purpose of protecting the surface. The protection member T is, for example, a tape or the like.

2. Holding Step Next, the holding table 5 of the grinding apparatus 1 shown in FIG. 3 holds the wafer W to which the protection member T has been attached. The grinding apparatus 1 shown in FIG. 3 includes a rough grinding unit 30 and a finish grinding unit 31 and grinds the wafer W held on any of the holding tables 5 by the rough grinding unit 30 and the finish grinding unit 31. is there.

  In the grinding device 1, for example, a second device base 11 is connected to the rear (+ Y direction side) of the first device base 10. Above the first apparatus base 10 is a carry-in / out area A in which the carry-in / out of the wafer W is performed. Above the second apparatus base 11 is a grinding area B where the wafer W held by the holding table 5 is ground by the rough grinding means 30 and the finish grinding means 31.

  On the front side (−Y direction side) of the first device base 10, a first cassette mounting portion 150 and a second cassette mounting portion 151 are provided, and the first cassette mounting portion 150 is provided on the first cassette mounting portion 150. The first cassette 150a in which the unprocessed wafer W is stored is mounted, and the second cassette 151a in which the processed wafer W is stored is mounted on the second cassette mounting portion 151.

  Behind the opening of the first cassette 150a, there is provided a robot 155 that unloads the unprocessed wafer W from the first cassette 150a and loads the processed wafer W into the second cassette 151a. At an adjacent position, a temporary placing area 152 for temporarily placing the wafer W is provided. Positioning means 153 is provided in the temporary storage area 152, and the positioning means 153 uses a plurality of positioning pins to move the wafer W unloaded from the first cassette 150a and placed on the temporary storage area 152 in a predetermined manner. Position (centering).

  At a position adjacent to the positioning means 153, a loading arm 154a that rotates while holding the wafer W is disposed. The loading arm 154a holds the wafer W positioned by the positioning means 153, and transports the wafer W to any of the holding tables 5 disposed in the grinding area B. An unloading arm 154b that rotates while holding the processed wafer W is provided next to the loading arm 154a. At a position close to the unloading arm 154b, a single wafer type cleaning means 156 for cleaning the processed wafer W transferred by the unloading arm 154b is provided. The wafer W cleaned by the cleaning means 156 is carried into the second cassette 151a by the robot 155.

  A first column 12 is provided upright (in the + Y direction) behind the second device base 11, and a coarse grinding feed means 20 is provided on the front surface of the first column 12. The coarse grinding feed means 20 is connected to the ball screw 200 having a vertical axis (Z-axis direction), a pair of guide rails 201 arranged in parallel with the ball screw 200, and the ball screw 200 to rotate the ball screw 200. The motor 202 includes a motor 202, an elevating plate 203 whose inner nut structure is screwed into a ball screw, and a side portion of which is in sliding contact with the guide rail 201, and a holder 204 connected to the elevating plate 203 to hold the rough grinding means 30. When the ball screw 200 is rotated, the lifting plate 203 is guided by the guide rail 201 and reciprocates in the Z-axis direction, and the rough grinding means 30 supported by the holder 204 also reciprocates in the Z-axis direction.

  The coarse grinding means 30 is connected to a spindle 300 whose axial direction is a vertical direction (Z-axis direction), a housing 301 for rotatably supporting the spindle 300, a motor 302 for driving the spindle 300 to rotate, and a lower end of the spindle 300. And a grinding wheel 304 detachably connected to the lower surface of the mount 303. The motor 302 causes the spindle 300 to rotate about the Z-axis axis, and accordingly, the grinding wheel 304 also rotates about the Z-axis axis. The grinding wheel 304 includes a wheel base 304a and a plurality of substantially rectangular parallelepiped coarse grinding wheels 304b fixed in a ring shape to the bottom surface of the wheel base 304a.

  A second column 13 is provided on the rear of the second device base 11 so as to be aligned with the first column 12 in the X-axis direction, and a finish grinding feed is provided on the front surface of the second column 13. Means 21 are provided. The finish grinding feed means 21 is configured similarly to the rough grinding feed means 20, and can feed the finish grinding means 31 in the Z-axis direction. The finish grinding means 31 includes a finish grinding wheel 314b, and the abrasive grains contained in the finish grinding wheel 314b are smaller than the abrasive grains of the coarse grinding wheel 304b described above. Other configurations of the finish grinding means 31 are the same as those of the rough grinding means 30. Regarding the finish grinding feed means 21 and the finish grinding means 31 in FIG. 3, the same components as those of the coarse grinding feed means 20 and the coarse grinding means 30 are denoted by the same reference numerals, and the description thereof will be omitted.

  The turntable 4 is disposed on the second device base 11, and, for example, three holding tables 5 are disposed on the upper surface of the turntable 4 at equal intervals in the circumferential direction. Rotation means (not shown) for rotating the turntable 4 is disposed below the turntable 4. The turntable 4 has an axis parallel to the Z axis with the center of the turntable 4 as the center of rotation. It can rotate around. As the three holding tables 5 revolve due to the rotation of the turntable 4, the wafer W mounted on the holding table 5 located near the temporary placement area 152 is moved to a position below the rough grinding means 30 and finish grinding. Positioned sequentially below the means 31.

  The holding table 5 includes, for example, a suction unit 50 having a circular plate shape and a holding surface 50a for holding the wafer W by suction, a frame 51 surrounding the holding surface 50a, and supporting the suction unit 50 from below. Consists of The reference surface 51a, which is the upper surface of the frame 51, and the holding surface 50a have the same height. Each of the three holding tables 5 has a suction unit 52 below the holding table 5, and can hold the wafer W on the holding surface 50 a by the suction force exerted by the suction unit 52. In addition, the three holding tables 5 can be rotated around an axis parallel to the Z-axis around the center of the holding table 5 by a rotating means (not shown) below the holding table 5.

  On the second apparatus base 11, a thickness measuring means 6 for measuring the total thickness of the wafer W and the protective member T during grinding is provided. The thickness measuring means 6 includes a first detection terminal 60 for detecting the height position of the reference surface 51a by contacting the reference surface 51a, which is the upper surface of the frame 51, and a height of the rear surface Wb by contacting the rear surface Wb of the wafer W A second detection terminal 61 for detecting the position; the thickness of the wafer W can be measured using the difference in height measured between the two terminals.

  On the first device base 10, a weight measuring means 7 for measuring the weight of the wafer after grinding is provided. The weight measuring means 7 includes a measuring table 70 and a monitor 71. A control means 8 is connected to the weight measuring means 7, and the control means 8 stores a weight when the wafer is ground and thinned to a desired thickness as a predetermined weight; And a comparison unit 81 for comparing the actual weight measured by the method with the predetermined weight stored in the weight storage unit 80. The comparison unit 81 sets an allowable weight difference before comparing the two weights, and determines whether or not the comparison result is included in the range of the allowable weight difference after the comparison. It will be.

  Further, a warning transmission means 9 is connected to the control means 8. The warning transmission means 9 receives the result of the comparison between the predetermined weight and the weight after grinding by the comparing section 81 of the control means 8 and plays a role of giving a warning when the weight after grinding is a value outside the allowable value. . As the warning transmitting means 9, for example, a warning indicator light such as an LED mounted on the upper part of the apparatus (not shown) is turned on when the weight after grinding is out of an allowable value, and the lighting display can be visually recognized by an operator or the like. Alternatively, the warning transmission unit 9 may include, for example, a speaker unit that emits a warning sound instead of the warning indicator light. It is also possible to adopt a configuration in which lighting of the warning indicator lamp and transmission of the warning sound can be performed simultaneously.

  In this step, the wafer W provided with the protection member T is unloaded from the first cassette 150a shown in FIG. 3 by the robot 155, and is positioned at a fixed position in the temporary storage area 152 by the positioning means 153. Thereafter, the user moves onto the holding table 5 using the loading arm 154a. As shown in FIG. 4, the wafer W placed on the holding table 5 with the back surface Wb exposed to the upper side is protected by a suction force of a suction unit 52 disposed below the suction unit 50. It is sucked and held on the holding table 5 via T.

3 Grinding Step In the grinding step, after rough grinding is performed on the back surface Wb of the wafer W to a thickness immediately before the finished thickness by using the rough grinding means 30, the abrasive grains are more roughened than the rough grinding wheel 304 b used in the rough grinding. The finish grinding is performed to the finish thickness using the finish grinding means 31 including the small finish grinding wheel 314b. The rough grinding and the finish grinding are separately described below.

(1) Rough Grinding The wafer W held on the holding table 5 near the temporary placing area 152 in the holding step is rotated by the turntable 4 in a counterclockwise direction as viewed from the + Z direction. To move down. As shown in FIG. 5, the positional relationship between the wafer W and the coarse grinding wheel 304b of the coarse grinding means 30 is such that the coarse grinding wheel 304b passes through the center of rotation of the wafer W. In a region of the wafer W where the coarse grinding wheel 304b does not pass, the second detection terminal 61 of the thickness measuring means 6 can be brought into contact with the back surface Wb of the wafer W.

  The coarse grinding grindstone 304b is rotated by rotating the spindle 300 by the motor 302 shown in FIG. 1, and the wafer W is rotated by rotating the holding table 5 by a rotating means below the holding table 5 (not shown). As a result, the rough grinding wheel 304b is brought into contact with the entire back surface Wb of the wafer W. The coarse grinding means 30 is fed in the −Z direction by the coarse grinding feed means 20, and the rotating coarse grinding stone 304 b is brought into contact with the back surface Wb of the wafer W held on the holding table 5 to perform the grinding. During the rough grinding, the first detection terminal 60 of the thickness measuring means 6 is brought into contact with the reference surface 51a and the second detection terminal 61 is brought into contact with the back surface Wb of the wafer W, so that the protection member T and the wafer W The total thickness is measured, and grinding is performed until immediately before the total thickness becomes a predetermined thickness.

(2) Finish Grinding After grinding the wafer W to just before a predetermined thickness, the rough grinding feeding means 20 raises the rough grinding means 30 and separates it from the wafer W. Thereafter, the turntable 4 shown in FIG. 3 is rotated counterclockwise as viewed from the + Z direction, and the holding table 5 for suction-holding the wafer W is moved below the finish grinding means 31. As in the case of the rough grinding, the positional relationship between the wafer W and the finish grinding wheel 314b of the finish grinding unit 31 is such that the finish grinding wheel 314b passes through the rotation center of the wafer W.

  As in the case of the coarse grinding, the finish grinding means 31 is sent downward by the finish grinding feed means 21 to bring the rotating finish grinding wheel 314b into contact with the back surface Wb of the wafer W, and the wafer W is rotated by the rotation of the holding table 5. Then, the entire surface of the rear surface Wb of the wafer W is finish-ground. In the meantime, the second detection terminal 61 is connected to the back surface Wb , The total thickness of the protection member T and the wafer W is measured, and grinding is performed until the total thickness reaches a predetermined thickness.

4 Weight Measurement Step After the finish grinding, the turntable 4 is rotated counterclockwise as viewed from the + Z direction, and the holding table 5 located below the finish grinding means 31 is moved to the −Y direction side. After that, the wafer W is transferred to the cleaning unit 156 by the unloading arm 154b. The cleaning unit 156 cleans the wafer W, and the cleaned wafer W is then transferred by the robot 155 and positioned on the weight measuring unit 7. Then, as shown in FIG. 6, the wafer W is placed on the measuring table 70 of the weight measuring means 7 and the measured value displayed on the monitor 71 is read, whereby the total of the protection member T and the wafer W after the grinding is obtained. Measure the weight of.

5 Confirmation Step Based on the total weight of the protective member T and the wafer W measured in the above-described weight measurement step, it is confirmed whether the wafer W is thinned to a desired thickness. If the thickness of the protection member T disposed on the wafer W is correct, the total weight (predetermined weight) of the weight of the protection member T and the weight of the wafer W for a desired thickness should take a constant value. is there. Therefore, if the thickness of the protective member T disposed before the grinding is different from the predetermined thickness, the difference between the total weight measured by the weight measurement after the grinding and the predetermined weight is obtained. Is born. Whether the wafer W is thinned to a desired thickness is confirmed based on whether or not the difference in weight is within a predetermined range.

  By using the control means 8 as shown in FIG. 3 at the time of performing the checking step, it is possible to check whether the thickness has been reduced to a desired thickness. In this case, the comparison unit 81 of the control unit 8 compares the total weight after grinding measured by the weight measurement unit 7 with a predetermined weight stored in advance in the weight storage unit 80 provided in the control unit 8. For example, if the comparison result is out of the predetermined allowable range, it is considered that the wafer W has not been finished to the desired thickness, and a warning is transmitted by the warning transmission unit 9 connected to the control unit 8. Specifically, for example, in response to the comparison result of the comparison unit 81, a warning indicator light mounted on the upper part of the apparatus (not shown) emits a specific color, and the operator visually recognizes the appearance from the appearance and recognizes an abnormality in the thickness. I do. Alternatively, the warning transmitting unit 9 includes a sound source (not shown), and emits a warning sound when the comparison result deviates from a predetermined allowable range, so that the operator recognizes the thickness abnormality.

  The following is a specific example when the confirmation step is performed. For example, when it is desired to finish a φ8 inch wafer having an original thickness of 725 ± 20 μm to a thickness of 150 μm, the thickness of the protective member T used at this time is determined to be 100 μm, and its weight is 3.8 g. Assume that the total weight of the protection member T and the wafer W when the wafer W is formed to have a thickness of 150 μm is 14.77 g. The value of the total weight is stored in the weight storage unit 80 of the control means 8 as a predetermined weight in advance.

  For example, an allowable variation in the weight of the protection member T is set in advance according to the variation in the thickness of the protection member T, such as ± 0.3 g. That is, if the total weight of the protective member T and the wafer W exceeds ± 0.3 g from the correct weight, it is determined that the thickness has not been reduced to the desired thickness. Now, it is assumed that the total weight of the wafer W and the protective member T measured by the weight measuring means 7 after grinding is 11.32 g. At this time, the comparison unit 81 compares the total weight after grinding with the stored predetermined weight. As a result, the weight difference exceeds the allowable range, and the measured value is reduced to the desired thickness. It is determined that there was not.

  If the comparison unit 81 compares the two weights and finds that the weight difference is out of the allowable range, the warning transmission unit 9 issues a warning based on the comparison result. As described above, the warning is transmitted by displaying a warning indicator light, transmitting a warning sound, or another method. Thereby, the operator recognizes the thickness abnormality. If the wafer W is formed thicker than the desired thickness, remove the protective member disposed on the surface of the wafer, and after disposing an appropriate protective member, grinding step, weight measurement step and The confirmation step may be performed again. On the other hand, when the wafer W is formed thinner than the desired thickness, the wafer W is discarded.

  In the present embodiment, the total weight of the protective member T and the wafer W after the grinding is measured using the weight measuring means 7 provided in the grinding apparatus 1. However, the grinding apparatus without the weight measuring means is used. May be used to perform the holding step and the grinding step, and thereafter, the total weight of the protection member T and the wafer W after the grinding may be measured using a single weighing scale.

W: Wafer Wa: Front surface Wb: Back surface L: Planned dividing line D: Device T: Protective member 1: Grinding device 10: First device base 11: Second device base 12: First column 13: Second Column 150: first cassette mounting part 150a: first wafer cassette 151: second cassette mounting part 151a: second wafer cassette 152: temporary storage area 153: positioning means 154a: loading arm 154b: unloading Loading arm 155: Robot 156: Cleaning means
20: Coarse grinding feed means 200: Ball screw 201: Guide rail 202: Motor 203: Lifting plate 204: Holder
21: Finish grinding feed means
30: Coarse grinding means 300: Spindle 301: Housing 302: Motor 303: Mount 304: Grinding wheel 304a: Wheel base 304b: Coarse grinding wheel 31: Finish grinding means 314b: Finish grinding wheel 4: Turntable 5: Holding table 50 : Suction part 50a: holding surface 51: frame body 51a: reference surface 52: suction means 6: thickness measuring means 60: first detecting terminal 61: second detecting terminal 7: weight measuring means 70: measuring table 71: monitor 8: Control unit 80: weight storage unit 81: comparison unit 9: warning transmission unit A: carry-in / out area B: grinding area

Claims (3)

A grinding method for grinding the back surface of the wafer to a desired thickness,
A protective member arranging step of arranging a predetermined protective member on the surface of the wafer,
A holding step of holding the wafer at the holding table via the protection member and exposing the back surface of the wafer,
After performing the holding step, the detection terminals are brought into contact with the upper surface of the holding table and the back surface of the wafer, respectively, and the back surface of the wafer is ground while measuring the total thickness of the protection member and the wafer to a predetermined thickness. A grinding step to thin
After performing the grinding step, a weight measuring step of measuring the weight of the wafer provided with the protection member,
Based on the weight measured in the weight measurement step, a confirmation step of confirming whether the wafer is thinned to the desired thickness,
Grinding method with. A grinding device for grinding the back surface of the wafer on which the protection member is disposed,
A holding table including a holding surface for holding the wafer through the protection member,
Grinding means having a grinding wheel for grinding the wafer held by the holding table,
A first detection terminal that contacts the holding surface to detect a height position of the holding surface, and a second detection terminal that contacts the back surface of the wafer held by the holding table and detects the height position of the back surface A thickness measuring means having:
Weight measuring means for measuring the weight of the wafer provided with the protective member after grinding,
Grinding equipment with. At least control means for controlling the grinding means,
The control means, a weight storage unit that stores as a predetermined weight the weight when the wafer provided with the predetermined protection member is thinned to a predetermined thickness,
A weight of the wafer provided with the protective member after grinding measured by the weight measuring means, and a comparison unit for comparing the predetermined weight,
The grinding device further includes a warning transmission unit that transmits a warning when the weight compared by the comparison unit is out of an allowable value.
The grinding device according to claim 2.

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