JP6622610B2 - Grinding equipment - Google Patents

Description

  The present invention relates to a grinding apparatus for grinding a wafer.

  In a grinding apparatus that holds a wafer on a holding table formed in a porous shape and presses a grinding wheel in contact with the surface to be ground of the wafer to press and grind the surface to be ground, the holding surface of the holding table and the grinding wheel By making the grinding surface parallel, the thickness accuracy of the wafer after grinding is improved.

  However, there is a problem that cracks occur in the wafer when grinding waste generated by grinding adheres to the holding surface and the wafer is held in this state and the grinding wheel is pressed. Therefore, the grinding apparatus is provided with a cleaning mechanism for cleaning the holding surface of the holding table, and the holding surface is removed at the timing when the grinding of one wafer is finished and separated from the holding table, that is, every time one wafer is ground. Washing is performed to prevent the wafer from being ground in a state where the grinding scraps adhere to the holding surface. Examples of the cleaning mechanism include a brush and a stone (for example, see Patent Document 1), a fluid cleaning mechanism for ejecting a fluid onto a holding surface (for example, see Patent Document 2), and the like.

Japanese Patent No. 4079289 Japanese Patent No. 5538971

  However, in the fluid cleaning mechanism that ejects fluid to the holding surface, it is difficult to discharge grinding waste that has entered the holding surface of the holding table formed in a porous shape. On the other hand, when the holding surface is cleaned with a brush or stone, the shape of the holding surface changes, so the accuracy of the parallelism between the holding surface and the grinding surface of the grinding wheel decreases, and the finished thickness accuracy after grinding the wafer There is a problem that decreases. In particular, if the holding surface is washed every time one wafer is ground, the accuracy of the parallelism between the holding surface and the grinding surface of the grinding wheel tends to be lowered, and this is also a factor of reducing productivity.

  The present invention has been considered in view of such problems, and it is possible to reliably and efficiently remove grinding dust on the holding surface, and to change the shape of the holding surface of the holding table to obtain a finished thickness accuracy after grinding the wafer. It is an object to prevent the decrease in the temperature.

The present invention provides a holding table having a holding surface that includes a porous plate and holds a wafer, a grinding means for grinding a wafer held by the holding surface of the holding table with a grinding surface of a grindstone, and cleaning the holding surface A grinding device comprising: a cleaning means, wherein the cleaning means contacts the holding surface and scrapes off grinding waste protruding from the holding surface; and presses the cleaning grindstone against the holding surface. And a holding table rotating means for rotating the holding table about the center of the holding surface, and is generated on the wafer from the surface to be ground of the wafer ground by the grinding means and held on the holding table. A crack detecting means for detecting the crack, and when the crack detecting means detects a crack generated on the wafer, the cleaning surface is cleaned by the cleaning means so that the holding surface is parallel to the ground surface. And a control unit to maintain.
The grinding apparatus includes a storage unit that stores the position of the crack detected by the crack detection unit, and the control unit sets the position of the holding surface corresponding to the position of the crack stored in the storage unit to the cleaning unit. It is preferable to wash.

In the present invention, the cleaning means that contacts and presses the cleaning grindstone with the holding surface to scrape the grinding scraps, the crack detection means that detects cracks generated on the surface to be ground of the wafer, and the cleaning means that holds the crack when it is detected. Since the control unit for cleaning the surface is provided, grinding scraps that have entered the holding surface can be discharged only when a crack is detected on the surface to be ground of the wafer. Therefore, it is possible to reliably and efficiently remove grinding scraps on the holding surface, and it is possible to prevent the shape of the holding surface from changing and the finished thickness accuracy after grinding of the wafer from being lowered.
In addition, a storage unit that stores the position of the crack generated in the wafer is provided, and the control unit causes the cleaning unit to clean the position of the holding surface corresponding to the position of the crack stored in the storage unit, thereby grinding the holding surface. Since only the place where the debris is attached can be cleaned, the cleaning efficiency is further increased and the productivity is further improved.

It is a perspective view which shows the example of a grinding device. It is sectional drawing which shows a holding table and a washing | cleaning means. It is sectional drawing which shows the example of a crack detection means. It is a perspective view which shows the example of a wafer. It is a top view which shows the example of a holding table. It is a top view which shows the position of the crack detected on the wafer. It is sectional drawing which shows the state in which the grinding dust has adhered to the holding surface of a holding table. It is sectional drawing which shows the state from which grinding waste is removed by the washing | cleaning means.

  A grinding apparatus 1 shown in FIG. 1 is an apparatus in which grinding means 3 a and 3 b perform grinding on a wafer W held on a holding table 2.

  On the front side of the grinding apparatus 1, cassette placement regions 4 a and 4 b are provided on which a cassette 40 a for housing the wafer W before grinding and a cassette 40 b for housing the wafer W after grinding are respectively placed. .

  A loading / unloading means 5 for loading / unloading the wafer W to / from the cassettes 40a, 40b is disposed in the vicinity of the cassette placement areas 4a, 4b. The wafer W carried out from the cassette 40a by the carry-in / out means 5 is placed on the alignment table 50, where the center of the wafer W is aligned at a fixed position. The alignment table 50 is provided with a rotating means 51, and the wafer W placed on the alignment table 50 can be rotated. In addition, a side of the alignment table 50 is provided with a detection unit 52 that detects a notch N formed at the peripheral edge of the wafer W as a mark indicating a crystal orientation. The detection unit 52 is, for example, a camera, a transmissive sensor, or a reflective sensor.

  A first transport unit 6a is disposed in the vicinity of the alignment table 50, and the wafer W aligned in the alignment table 50 is placed on one of the three holding tables 2 by the first transport unit 6a. Be transported. Each of the three holding tables 2 can rotate and revolves as the turntable 20 rotates.

  Grinding means 3a and 3b are disposed above the revolution movement path of the holding table 2 as the turntable 20 rotates. Since the grinding means 3a and 3b are configured similarly except for the type of the grinding wheel 34, they will be described with common reference numerals. In the grinding means 3a and 3b, a grinding wheel 32 is attached to a lower end of a rotating shaft 30 having a vertical axis through a wheel mount 31, and the rotating shaft 30 is rotated by a motor 33 connected to the upper end of the rotating shaft 30. When driven, the grinding wheel 32 rotates. A grinding wheel 34 is fixed to the lower part of the grinding wheel 32. The lower surface of the grinding wheel 34 is a grinding surface for grinding the wafer W. The grinding wheel 34 that constitutes the grinding means 3a is, for example, a rough grinding wheel, and the grinding wheel 34 that constitutes the grinding means 3b is, for example, a finish grinding wheel.

  The grinding means 3a and 3b are fixed to an elevating plate 36 that is in sliding contact with a guide rail 35 extending in the vertical direction. As the elevating plate 36 is raised and lowered by being driven by a motor 37, the grinding means 3a and 3b are also raised and lowered. It has a configuration.

  Wafer cleaning means 7 for cleaning the wafer W is disposed at a position adjacent to the cassette mounting area 4b. The wafer cleaning means 7 includes a spinner table 70 that holds and rotates the wafer W. Further, in the vicinity of the wafer cleaning means 7, a second transport means 6 b for transporting the ground wafer W from the holding table 2 to the wafer cleaning means 7 is disposed.

  Cleaning means 8 for cleaning the holding surface 2 a of the holding table 2 is disposed above the movement path of the holding table 2. As shown in FIG. 2, the cleaning means 8 includes a rotary shaft 80 having a vertical axis, a housing 81 that rotatably supports the rotary shaft 80, and a cleaning grindstone disposed at the lower end of the rotary shaft 80. 82, lifting / lowering means 83 for moving the housing 81 up and down, and holding table rotating means 84 for rotating the holding table 2 around the center of the holding surface 2a.

  The cleaning grindstone 82 is formed, for example, from a resin bond grindstone, a resin material, or a ceramic material in a plate shape. The elevating means 83 includes a rail 830 that is in sliding contact with the housing 81 and, for example, a linear motor provided inside the housing 81, and can elevate and lower the housing 81. The holding table rotating means 84 includes a motor 840, an encoder 841, a shaft 842 driven and rotated by the motor 840, a pulley 843 formed at the tip of the shaft 842, a belt 844 wound around the pulley 843, And a driven pulley 845 around which a belt 844 is wound.

  Each holding table 2 includes a porous plate 21, a frame body 22 that supports the porous plate 21, and a base 23 to which the frame body 22 is attached. A suction path 24 that communicates with the porous plate 21 is formed in the frame body 22 and the base 23. The suction path 24 communicates with the suction source 25. The frame 22 is connected to a driven pulley 845, and the holding table 2 can be rotated by the motor 840 rotating the driven pulley 845 via the belt 844.

  On the side of the housing 81, crack detecting means 90 is disposed. For example, as shown in FIG. 3, the crack detection means 90 includes a camera 900 having a vertical optical axis and a ring illumination 901 that is positioned around the camera 900 and illuminates the wafer W. The ring illumination 901 is movable in the vertical direction. Instead of ring illumination, epi-illumination may be used in which light is dropped along the optical axis of the camera 900 and the lens connects an image with the reflected light of the light. Moreover, as the crack detection means 90, you may use the light quantity sensor using a laser or LED, for example.

  The camera 900 of the crack detection unit 90 is connected to the control unit 91 shown in FIG. 2, and image information acquired by the crack detection unit 90 is transferred to the control unit 91. In addition, a storage unit 92 is connected to the control unit 91, and image information can be stored in the storage unit 92 as necessary. The control unit 91 manages the position and movement of each part of the grinding apparatus 1 using XYZ coordinates, and can move each part to a desired position.

  As shown in FIG. 1, a guide rail 85 is disposed so as to straddle the turntable 20, and the elevating means 83 includes, for example, a linear motor or the like, and can move horizontally along the guide rail 85. ing. Therefore, the cleaning grindstone 82 is movable in the horizontal direction and the vertical direction. The lifting / lowering means 83 functions as a pressing means for pressing the cleaning grindstone 82 against the holding surface 2a.

  When grinding the back surface Wb of the wafer W shown in FIG. 1 using the grinding apparatus 1 configured as described above, the protective tape T is adhered to the front surface Wa of the wafer W, and the wafer W is attached to the cassette 40a. Be contained. Then, the wafer is unloaded from the cassette 40 a by the loading / unloading means 5 and placed on the alignment table 50. After the center position of the wafer W is aligned at a fixed position on the alignment table 50, the wafer W is transported to the holding table 2 by the first transport means 6a. At this time, the first transport means 6a transports the wafer W to the holding table 2 so that the center of the holding table 2 and the center of the wafer W coincide.

As shown in FIG. 4, a notch N is formed as a mark indicating the crystal orientation at the peripheral edge of the wafer W. When the wafer W is placed on the holding table 2 as shown in FIG. A notch alignment portion 26 for aligning with the notch N is formed. The notch alignment portion 26 is formed in a barrier 27 that covers the outer peripheral portion of the porous plate 21. The frame body 22 is formed with a plurality of screw holes 28 through which screws for fixing the frame body 22 to the base 23 shown in FIG. 2 are inserted. In the holding table 2, the notch N of the wafer W and the notch alignment portion 26 of the holding table 2 are aligned, the protective tape T side is placed and held on the holding surface 2a, and the back surface Wb is exposed upward. Become. The rotating means 51 rotates the wafer W and stops the rotation of the wafer W at the position where the detection unit 52 detects the notch N, and the first transport means 6a holds the wafer located at that position and holds the holding table 2. , The notch N can be made to coincide with the notch aligning portion 26 of the holding table 2 and conveyed. That is, the position of the notch N of the wafer W when the first transport means 6a holds the wafer is determined when the wafer W is held and carried out from the alignment table 50, and the holding table 2 is rotated to rotate the first. Alignment is performed so that the position of the notch N of the wafer W held by the transport means 6a coincides with the notch alignment portion 26 of the holding table 2.
The position of the wafer W when the first conveying means 6a holds and unloads the wafer from the alignment table 50 is the position where the detection unit 52 has detected the notch N. However, the detection unit 52 has detected the notch N. Then, it may be a position rotated by a predetermined angle.

  Next, the wafer W is positioned directly below the grinding means 3 a by the counterclockwise rotation of the turntable 20. As the holding table 2a rotates, the grinding means 3a descends while the grinding wheel 34 rotates as the grinding wheel 32 rotates, and the rotating grinding wheel 34 contacts the back surface Wb of the wafer W for grinding. . Here, for example, rough grinding is performed.

  After the rough grinding is finished, the wafer W is positioned directly below the grinding means 3b by the rotation of the turntable 20. Then, the holding table 2 rotates counterclockwise, and the grinding means 3b descends while the grinding wheel 34 rotates as the grinding wheel 32 rotates, and the rotating grinding wheel 34 contacts the back surface Wb of the wafer W. Grinding is done. Here, for example, finish grinding is performed.

  When the wafer is ground in this way, grinding waste may enter between the holding surface 2a of the holding table 2 and the protective tape T attached to the wafer W, and the grinding waste may adhere to the holding surface 2a. is there. When the back surface Wb of the wafer W is ground in a state where the attached scrap remains on the holding surface 2a, there is a problem that the wafer W is cracked.

  Therefore, after finishing grinding, the ground wafer W held on the holding table 2 is moved below the crack detecting means 90 by the counterclockwise rotation of the turntable 20. Then, the entire surface of the back surface Wb that is the surface to be ground of the wafer W is imaged by the crack detection means 90, and the acquired image is transferred to the control unit 91. The control unit 91 inspects whether or not a crack has occurred in the wafer W based on pixel information constituting the image.

  If the controller 91 does not detect a crack, the second transfer device 6b holds the wafer W and transfers it to the spinner table 70 of the wafer cleaning means 7. Then, high-pressure water is jetted onto the wafer W along with the rotation of the spinner table 70 to perform cleaning, and further, high-pressure air is jetted onto the wafer W along with the rotation of the spinner table 70 to perform drying. After that, the wafer W that has been cleaned and dried by the loading / unloading means 5 is transported and accommodated in the cassette 40b.

  On the other hand, when the control unit 91 detects the crack C, the position of the crack C is specified by the positional relationship with the center WO and the notch N of the wafer W. The specific process is as follows.

  When obtaining the center coordinates WO of the wafer W shown in FIG. 6 in the image, while rotating the holding table 2, three positions on the periphery of the wafer W are imaged and images for each are acquired. Then, in each image, image processing for recognizing a portion where the pixel value has changed by a certain threshold value or more as an edge is performed to obtain three XY coordinates.

  If the coordinates of the center WO of the wafer W are (XO, YO) and the coordinates of the three points on the periphery of the wafer W are (x1, y1), (x2, y2) and (x3, y3), respectively, the coordinates of the center WO (XO, YO) is obtained by the following formula (1) by the control means 91.

  In the example of FIG. 6, the coordinates (XN, YN) of the notch N are, for example, the intersection of an arc when the wafer W is assumed to be circular and an extension of a line connecting the center WO and the notch N. Further, the radius R of the wafer W can be obtained by the following equation (2), and the position displaced by the radius R from the center WO in the direction of the notch N can be used as the coordinates of the notch N.

  Thus, when the coordinates (XO, YO) of the wafer center WO and the coordinates (XN, YN) of the notch N are obtained, the position of the crack C is determined by the number of pixels between these and the crack C. The displacement XC in the X-axis direction from the center WO of the wafer W and the displacement YC in the Y-axis direction from the notch N can be obtained. The position information of the crack C thus obtained is stored in the storage unit 92.

  The crack C can be regarded as being formed at the position held on the holding surface 2a. That is, for example, as shown in FIG. 7, when the grinding waste 100 is attached on the holding surface 2 a, the pressing force of the grinding wheel 34 is applied to the held wafer W, so that the wafer W Of these, it is considered that the crack C occurred in the portion located above the grinding scrap 100. Accordingly, the grinding dust adheres to the position separated by XC in the X-axis direction from the rotation center of the holding table 2 recognized by the control unit 91 and at a position separated by YC in the Y direction from the notch alignment unit 26 shown in FIG. Can be considered.

  Then, the raising / lowering means 83 moves horizontally along the guide rail 85 by control by the control part 91, and positions the washing grindstone 82 above the position where the grinding | polishing waste has adhered. Then, as shown in FIG. 8, the holding table rotating means 84 rotates the holding table 2, and the elevating means 83 lowers the cleaning grindstone 82 while rotating the cleaning grindstone 82, and presses the cleaning grindstone 82 against the holding surface 2a. To do. Then, the grinding waste protruding upward from the holding surface 2a is scraped off, and the holding surface 2a becomes parallel to the grinding surface (lower surface) of the grinding wheel 34.

  In this manner, the control unit 91 causes the cleaning unit 8 to clean the position of the holding surface 2a corresponding to the position of the crack stored in the storage unit 92. This is efficient because it is not necessary to clean the entire holding surface 2a. Further, since only the minimum necessary cleaning is required, the parallelism between the holding surface 2a and the grinding surface of the grinding wheel 34 is maintained, the shape of the holding surface 2a is changed, and the finished thickness accuracy of the wafer W after grinding is improved. It can be prevented from lowering.

  In addition, although the cleaning grindstone 82 of this embodiment is formed in the magnitude | size which has a diameter about the radius of the holding surface 2a, it specifies the adhesion position of the grinding waste 100 on the holding surface 2a as mentioned above, and grinds. When removing debris, a cleaning grindstone smaller than the cleaning grindstone 82 may be used.

  Further, the holding table 2 of the present embodiment includes a notch aligning portion 26, and by aligning the positions of the notch aligning portion 26 and the notch N formed on the wafer W, based on the positional relationship between the crack C and the notch N. Although the position of the grinding waste 100 on the holding surface 2a is specified, when the wafer is not notched and the orientation flat is formed, the holding table is provided with an orientation flat alignment portion, By aligning the orientation flat alignment portion with the orientation flat formed and the holding table, the position of the grinding waste on the holding surface 2a can be specified based on the positional relationship between the crack and the orientation flat.

  Further, when the holding table has neither a notch alignment portion nor an orientation flat alignment portion, the control unit 91 obtains the distance from the center of the wafer to the crack, and is washed at a position separated from the center of the holding table 2 by the obtained distance. By making the grindstone contact and rotating the holding table 2 once, grinding debris at a position corresponding to the crack can be removed.

1: Cleaning device 2: Holding table 2a: Holding surface 20: Turntable 21: Porous plate 22: Frame body 23: Base 24: Suction path 25: Suction source 26: Notch alignment part 27: Barrier 28: Screw holes 3a, 3b : Grinding means 30: rotating shaft 31: wheel mount 32: grinding wheel 33: motor 34: grinding wheel 35: guide rail 36: lifting plate 37: motor 4a, 4b: cassette mounting area 40a, 4b: cassette 5: loading / unloading Means 50: Positioning table 6a: First transport means 6b: Second transport means 7: Wafer cleaning means 70: Spinner table 8: Cleaning means 80: Rotating shaft 81: Housing 82: Cleaning grindstone 83: Lifting means (pressing) Means) 830: Rail 84: Holding table rotating means 840: Motor 841: Encoder 842: Shaft 843: Push 844: Belt 845: Driven pulley 85: Guide rail 90: Crack detection means 900: Camera 901: Ring illumination 91: Control unit 92: Storage unit W: Wafer Wa: Front side Wb: Back side WO: Center N: Notch C: Crack T: protective tape 100: grinding scrap

Claims (2)

A holding table comprising a porous plate and holding a wafer; a grinding means for grinding the wafer held by the holding surface of the holding table with a grinding surface of a grindstone; and a cleaning means for cleaning the holding surface; A grinding apparatus comprising:
The cleaning means includes a plate-shaped cleaning grindstone that contacts the holding surface and scrapes off grinding waste protruding from the holding surface, a pressing means that presses the cleaning grindstone against the holding surface, and the holding table that holds the holding table. Holding table rotating means for rotating about the center of the shaft,
Crack detecting means for detecting cracks generated in the wafer from the ground surface side of the wafer ground by the grinding means and held on the holding table;
A controller that cleans the holding surface by the cleaning means when the crack detecting means detects a crack generated in the wafer, and maintains parallelism between the holding surface and the grinding surface;
A grinding apparatus comprising:   2. A storage unit that stores a position of the crack detected by the crack detection unit, and the control unit causes the cleaning unit to clean the position of the holding surface corresponding to the position of the crack stored by the storage unit. The grinding apparatus as described.

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