JP2012134275A - Grinding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grinding device capable of stably and properly grinding both faces of a laminated wafer, in which two wafers are adhered.SOLUTION: A grinding device grinds both faces of a laminated wafer, in which a first wafer, on which an orientation flat indicating a crystal orientation is formed, and a second wafer, on which an orientation flat smaller than the first orientation flat is formed and which has a diameter almost identical to that of the first wafer are opposed and adhered. The grinding device comprises a chuck table 54 for suction-holding the laminated wafer, and grinding means for grinding the laminated wafer held by the chuck table. A holding face of the chuck table includes a first suction region 55a corresponding to a shape of the first wafer, and a second suction region 55b corresponding to a shape of a portion of the second wafer projecting from the first wafer. When an exposed face of the first wafer is ground, the first and second suction regions are actuated. When an exposed face of the second wafer is ground, the first suction region is actuated to suction-hold the first wafer.

Description

  The present invention relates to a grinding apparatus suitable for grinding a laminated wafer in which two wafers having orientation flats of different sizes are laminated.

  A semiconductor wafer in which a number of devices such as IC and LSI are formed on the surface, and each device is partitioned by a line to be divided (street), the back surface is ground by a grinding machine and processed to a predetermined thickness. A dividing line is cut by a cutting device (dicing device) to be divided into individual devices, and the divided devices are widely used in electric devices such as mobile phones and personal computers.

  In order to reduce the size and weight of a semiconductor chip, a semiconductor wafer is usually cut along a predetermined dividing line and separated into individual devices (chips) by grinding the back surface of the wafer to obtain a predetermined chip. Back surface grinding to be processed into a thickness is performed.

  A grinding apparatus for grinding the back surface of a wafer includes a chuck table for holding a wafer, and a grinding means for rotatably supporting a grinding wheel in which a grinding wheel for grinding the wafer held on the chuck table is annularly arranged. At least, the wafer can be formed to a desired thickness.

  The wafer to be ground includes various forms. For example, a first wafer in which an orientation flat indicating a crystal orientation is formed, and a second wafer in which an orientation flat smaller than the orientation flat of the first wafer is formed. In some cases, a laminated wafer to which a wafer faces and is bonded is ground. Both the first and second wafers are composed of silicon wafers or the like.

  The suction area of the chuck table of the conventional grinding apparatus for grinding such a laminated wafer is formed in accordance with the shape of the first wafer having a large orientation flat. When the exposed surface of the second wafer is ground with such a grinding apparatus, the entire surface of the first wafer is sucked and held by the chuck table, and stable grinding can be performed.

JP 2000-21820 A

  However, when the exposed surface of the first wafer is ground, the second wafer protrudes from the orientation flat of the first wafer in order to suck and hold the second wafer in the suction area formed in accordance with the shape of the first wafer. There is a problem in that the orientation flat portion of the second wafer flutters, and the orientation flat of the second wafer comes into contact with the grinding wheel and is thinned.

  The present invention has been made in view of the above points, and an object thereof is to provide a first wafer on which an orientation flat showing a crystal orientation is formed, and an orientation flat smaller than the orientation flat of the first wafer. The present invention is to provide a grinding apparatus capable of stably and appropriately grinding both surfaces of a bonded wafer in which a second wafer formed with a surface is bonded to each other.

  According to the present invention, a first wafer having an orientation flat indicating a crystal orientation is formed, and an orientation flat smaller than the orientation flat of the first wafer is formed, and a second wafer having substantially the same diameter as the first wafer is formed. A grinding apparatus for grinding an exposed surface of a first wafer and an exposed surface of a second wafer of a laminated wafer that are bonded to face each other, comprising a chuck table having a holding surface for sucking and holding the laminated wafer; Grinding means for rotatably supporting a grinding wheel in which a grinding wheel for grinding a laminated wafer held on the chuck table is annularly arranged, and the holding surface of the chuck table has a shape of the first wafer. And a second suction area corresponding to the shape of the protruding portion of the second wafer from the first wafer. When the exposed surface of the first wafer is ground, the first and second suction regions are acted to suck and hold the second wafer, and the exposed surface of the second wafer is ground. In this case, a grinding apparatus is provided in which the first wafer is sucked and held by acting the first suction region.

  Preferably, the grinding apparatus includes a first cassette placing portion on which a first cassette containing a plurality of laminated wafers is placed, and a second cassette on which a second cassette containing a ground wafer after grinding is placed. A stacking unit; a stacking wafer temporarily transported from the first cassette by the unloading unit; and a stacking wafer temporarily transported from the first cassette by the unloading unit. And positioning means for detecting the orientation flat and positioning the orientation flat in a predetermined direction, a first transport means for transporting the laminated wafer temporarily placed on the positioning means to the chuck table, and grinding is completed. A second conveying means for carrying out the laminated wafer from the chuck table, and a laminated wafer carried out by the second conveying means. A cleaning means for cleaning the wafer and a carrying-in means for storing the laminated wafer washed by the washing means in the second cassette, wherein at least one of the carrying-out means and the carrying-in means reverses the laminated wafer. And after the exposed surface of the first wafer or the exposed surface of the second wafer of the laminated wafer is ground, the laminated wafer is reversed by the carrying-out means or the carrying-in means having a reversing function. The exposed surface of the first wafer or the exposed surface of the first wafer is ground.

  According to the grinding apparatus of the present invention, when the exposed surface of the first wafer is ground, the entire surface of the second wafer can be sucked and held by acting the first and second suction regions. The second wafer orientation flat is in contact with the grinding wheel without causing any fluttering in the orientation flat portion of the second wafer protruding from the orientation flat of the first wafer. The problem of being cut and thinned can be solved.

1 is an external perspective view of a grinding apparatus according to an embodiment of the present invention. It is a perspective view of a chuck table unit and a chuck table feed mechanism. 3A is a perspective view of the laminated wafer as seen from the first wafer side, and FIG. 3B is a perspective view of the laminated wafer as seen from the second wafer side. It is a perspective view of the chuck table concerning an embodiment of the present invention. 5A is a perspective view of a state in which the second wafer is sucked and held by the chuck table, and FIG. 5B is a perspective view of a state in which the first wafer is sucked and held by the chuck table. 6A is a perspective view of a state in which the first wafer of the laminated wafer sucked and held on the chuck table is ground by the grinding wheel, and FIG. 6B is a first view of the laminated wafer sucked and held on the chuck table. It is a perspective view of the state which is grinding the wafer of 2 with a grinding wheel. FIG. 7A is a side view of the laminated wafer before grinding, and FIG. 7B is a side view of the laminated wafer after grinding the first and second wafers.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an external perspective view of a grinding apparatus 2 according to an embodiment of the present invention. The housing 4 of the grinding device 2 is composed of a horizontal housing part 6 and a vertical housing part 8.

  A pair of guide rails 12 and 14 extending in the vertical direction are fixed to the vertical housing portion 8. A grinding means (grinding unit) 16 is mounted along the pair of guide rails 12 and 14 so as to be movable in the vertical direction. The grinding unit 16 is attached to a moving base 18 that moves up and down along a pair of guide rails 12 and 14 via a support portion 20.

  The grinding unit 16 includes a spindle housing 22 attached to the support portion 20, a spindle 24 rotatably accommodated in the spindle housing 22, and a servo motor 26 that rotationally drives the spindle 24.

  As shown in FIG. 6, a wheel mount 28 is fixed to the tip of the spindle 24, and a grinding wheel 30 is detachably attached to the wheel mount 28 with a screw 31.

  The grinding wheel 30 is configured by fixing a plurality of grinding wheels 34 in which diamond abrasive grains or the like are hardened with an appropriate bonding agent such as resin bond or vitrified bond to a free end portion of a wheel base 32. Grinding water is supplied to the grinding wheel 24 via a hose 36. Preferably, pure water is used as the grinding water.

  Referring again to FIG. 1, the grinding apparatus 2 includes a grinding unit feed mechanism 44 that moves the grinding unit 16 in the vertical direction along the pair of guide rails 12 and 14. The grinding unit feed mechanism 44 includes a ball screw 46 and a pulse motor 48 fixed to one end of the ball screw 46. When the pulse motor 48 is pulse-driven, the ball screw 46 rotates and the moving base 18 is moved in the vertical direction via the nut of the ball screw 46 fixed inside the moving base 18.

  A chuck table unit 50 is disposed in the recess 10 of the horizontal housing portion 6. As shown in FIG. 2, the chuck table unit 50 includes a support base 52 and a chuck table 54 that is rotatably disposed on the support base 52. The chuck table unit 50 further includes a cover 56 having a hole through which the chuck table 54 is inserted.

  As shown in FIG. 2, the chuck table unit 50 is moved in the front-rear direction (Y-axis direction) of the grinding apparatus 2 by the chuck table moving mechanism 58. The chuck table moving mechanism 58 includes a ball screw 60 and a pulse motor 64 connected to one end of a screw shaft 62 of the ball screw 60.

  When the pulse motor 64 is pulse-driven, the screw shaft 62 of the ball screw 60 rotates, and the support base 52 having a nut screwed to the screw shaft 62 moves in the front-rear direction of the grinding device 2. Therefore, the chuck table 54 also moves in the front-rear direction according to the rotation direction of the pulse motor 64.

  As best shown in FIG. 4, the chuck table 54 has a first suction area 55a and a second suction area 55b. The first and second suction regions 55a and 55b are independent and are selectively connected to a suction source via a switching valve.

  The shape of the first suction region 55a corresponds to the shape of the first wafer 11 shown in FIG. 3, and the shape of the second suction region 55b is the protruding portion 15a of the second wafer 15 protruding from the first wafer 11. It corresponds to the shape.

  As shown in FIG. 1, the pair of guide rails 66 and 68 and the chuck table moving mechanism 58 shown in FIG. 2 are covered with bellows 70 and 72. That is, the front end portion of the bellows 70 is fixed to the front wall that defines the recess 10, and the rear end portion is fixed to the front end surface of the cover 56. The rear end of the bellows 72 is fixed to the vertical housing portion 8, and the front end thereof is fixed to the rear end surface of the cover 56.

  In the horizontal housing portion 6 of the housing 4, the first wafer cassette 74, the second wafer cassette 76, the wafer transfer robot 78, the wafer positioning means 80, and the wafer positioned by the wafer positioning means 80 are moved to the chuck table 54. A first conveying means 82 for conveying, a second conveying means 84 for unloading the ground wafer from the chuck table 54, and a spinner cleaning means 86 are provided.

  The wafer transfer robot 78 also serves as unloading means for unloading the wafer from the first cassette 74 and unloading means for unloading the wafer from the spinner cleaning means 86 into the second cassette 76. The positioning means 80 has a plurality of positioning pins 81 for centering the wafer, and a pair of pins 83 for detecting the orientation flat (orientation flat) of the wafer and positioning the orientation flat in a predetermined direction.

  An operation panel 88 is provided in front of the housing 4 for an operator to input grinding conditions and the like. Further, a cleaning water spray nozzle 90 for cleaning the chuck table 54 is provided at the approximate center of the horizontal housing portion 6.

  The cleaning water jet nozzle 90 ejects cleaning water toward the wafer after grinding held by the chuck table 54 in a state where the chuck table 54 is positioned in the wafer carry-in / out region. In the concave portion 10 of the housing 4, a drain port 92 is provided for draining the grinding water containing the wafer grinding waste by the grinding wheel 32.

  Referring to FIG. 3 (A), a perspective view of a laminated wafer 19 that is a grinding object of the present invention is shown. The laminated wafer 19 includes a first wafer 11 on which an orientation flat (hereinafter abbreviated as an orientation flat) 13 indicating a crystal orientation is formed, and a second wafer on which an orientation flat 17 smaller than the orientation flat 13 of the first wafer 11 is formed. The wafer 15 is configured to face and be bonded.

  In the laminated wafer 19 of the present embodiment, both the first wafer 11 and the second wafer 15 are made of ferrite wafers and have substantially the same diameter. Reference numeral 15 a denotes a protruding portion of the second wafer 15 that protrudes outward from the orientation flat 13 of the first wafer 11.

  FIG. 3B shows a perspective view of the laminated wafer 19 obtained by inverting the state shown in FIG. As shown in FIG. 7A, the first wafer 11 and the second wafer 15 have substantially the same thickness t1. The thickness t1 of the first and second wafers 11 and 15 before grinding is, for example, 220 μm.

  Hereinafter, the grinding operation of the laminated wafer 19 by the grinding apparatus 2 configured as described above will be described. A plurality of stacked wafers 19 are accommodated in the first cassette 74 with the first wafer 11 facing upward.

  Thus, the first cassette 74 containing the plurality of laminated wafers 19 is placed on a predetermined cassette placement portion of the housing 4. The second cassette 76 is mounted on a predetermined cassette mounting portion of the housing 4, and the laminated wafer 19 in which the grinding of the first wafer 11 and the second wafer 15 has been completed is accommodated.

  The laminated wafer 19 accommodated in the first cassette 74 is transported by the wafer transport robot 78 by the vertical movement and forward / backward movement, and is temporarily placed on the wafer positioning means 80. In the wafer positioning means 80, the laminated wafer 19 is centered by a plurality of positioning pins 81 that are movable in the radial direction, and the orientation flat 17 of the second wafer 15 is detected by a pair of fixed pins 83. The orientation flat 17 is positioned in a predetermined direction by the rotation of 79.

  The laminated wafer 19 with the centering and the orientation flat 17 positioned in a predetermined direction is adsorbed by the first conveying means 82 and placed on the chuck table 54 positioned in the wafer loading / unloading area by the swiveling operation. As shown in (A), the chuck table 54 sucks and holds it.

  At this time, the cutting valve is switched so that both the first suction area 55a and the second suction area 55b of the chuck table 54 shown in FIG. 4 communicate with the suction source, and the first and second suction areas 55a and 55b perform the second operation. The entire surface of the wafer 15 is sucked and held.

  When the chuck table 54 sucks and holds the laminated wafer 19 in this way, the chuck table moving mechanism 58 is operated to move the chuck table 54 in the Y-axis direction and position it in the grinding region behind the apparatus.

  When the chuck table 54 is positioned in the grinding region, the center of the laminated wafer 19 sucked and held by the chuck table 54 is positioned slightly beyond the outer circumference circle of the grinding wheel 30 as shown in FIG. .

  When the laminated wafer 19 is positioned in this manner, the servo motor 26 is driven while rotating the chuck table 54 in the direction of arrow a at, for example, about 100 rpm, and the grinding wheel 30 is moved in the same direction as the chuck table 54, that is, in the direction of arrow b. For example, while rotating at 6500 rpm, the pulse motor 48 of the grinding unit feed mechanism 44 is driven to lower the grinding unit 16.

  Then, the grinding wheel 30 of the grinding wheel 30 is brought into contact with the first wafer 11 of the laminated wafer 19, and the exposed surface of the first wafer 11 is ground while being fed at a predetermined grinding feed speed (for example, 7 μm / s). Grind. The first wafer 11 is ground to, for example, 170 μm while measuring the thickness of the first wafer 11 with a contact or non-contact thickness gauge.

  When grinding the first wafer 11, both the first and second suction regions 55 a and 55 b communicate with the suction source and suck and hold the entire surface of the second wafer 15. The protruding portion 15a of the second wafer protruding to the surface is also sucked and held, and the orientation flat 17 of the second wafer 15 is prevented from fluttering. The problem of becoming will not occur.

  When grinding of the first wafer 11 is completed, the chuck table moving mechanism 58 is driven to position the chuck table 54 in the wafer carry-in / out area. If the chuck table 54 is positioned in the wafer carry-in / out region, the washing water is jetted from the washing water jet nozzle 90 to clean the ground surface of the ground laminated wafer 19 held by the chuck table 54. At the same time, the chuck table 54 after the laminated wafer 19 is carried out is cleaned.

  After the laminated wafer 19 held on the chuck table 54 is released from suction, the laminated wafer 19 is attracted to the second conveying means 84 and conveyed to the spinner cleaning means 86 by the turning operation of the second conveying means 84. . The laminated wafer 19 is spin-cleaned by a spinner cleaning means 86 and spin-dried.

  The laminated wafer 19 that has been dried is held by the wafer transfer robot 78, inverted 180 degrees, and placed on the positioning means 80. The laminated wafer 19 in which the centering and the orientation flat 87 are positioned in a predetermined direction by the positioning means 80 is transported by the first transport means 82 to the chuck table 54 positioned in the wafer carry-in / out area.

  In the chuck table 54, the second suction area 55b shown in FIG. 4 is disconnected from the suction source by the operation of the switching valve, and only the first suction area 55a is connected to the suction source. Therefore, as shown in FIG. 5B, the laminated wafer 19 is sucked and held by the chuck table 54 only in the first suction region 55a, and the second wafer 15 is exposed.

  When the chuck table 54 sucks and holds the laminated wafer 19 in this way, the chuck table moving mechanism 58 is operated to move the chuck table 54 in the Y-axis direction and position it in the grinding region behind the apparatus.

  Next, as in the grinding of the first wafer 11, while rotating the chuck table 54 in the direction of arrow a at 100 rpm and rotating the grinding wheel 30 in the direction of arrow b at 6500 rpm, the pulse motor of the grinding unit feed mechanism 44 is rotated. 48 is driven to lower the grinding unit 16.

  Then, the grinding of the second wafer 15 is performed while the grinding wheel 34 of the grinding wheel 30 is brought into contact with the exposed surface of the second wafer 15 and fed at a predetermined grinding feed speed (for example, 7 μm / s).

  While measuring the thickness of the second wafer 15 with a contact-type or non-contact-type thickness measuring gauge, the second wafer 15 is finished to a predetermined thickness t2 as shown in FIG. 7B. t2 is, for example, 170 μm.

  When grinding is completed, the chuck table moving mechanism 58 is driven to position the chuck table 54 in the wafer carry-in / carry-out region. If the chuck table 54 is positioned in the wafer carry-in / out region, the washing water is jetted from the washing water jet nozzle 90 to clean the ground surface of the ground laminated wafer 19 held by the chuck table 54. At the same time, the chuck table 54 after the laminated wafer 19 is carried out is cleaned.

  After releasing the suction and holding of the chuck table 54, the laminated wafer 19 is transported to the spinner cleaning means 86 by the second transport means 84. The laminated wafer 19 conveyed to the spinner cleaning means 86 is spin-cleaned and spin-dried. Next, the laminated wafer 19 is transported by the wafer transport robot 78 and accommodated in a predetermined position of the second wafer cassette 76.

  Since the chuck table 54 of the above-described embodiment has the first suction area 55a and the second suction area 55b that can be selectively and independently communicated with the suction source, the first wafer 11 of the laminated wafer 19 is provided. When grinding the first wafer 11, both the first suction area 55 a and the second suction area 55 b communicate with the suction source to suck and hold the entire surface of the second wafer 15, so that the second wafer is ground when the first wafer 11 is ground. The orientation flat 17 of the second wafer 15 does not flutter, and the problem that the orientation flat 17 of the second wafer 15 comes into contact with the grinding wheel 34 and becomes thin can be solved.

2 Grinding device 11 First wafer 13 Orientation flat 15 of the first wafer Second wafer 16 Grinding means (grinding unit)
17 Orientation Flat 19 of Second Wafer 19 Laminated Wafer 24 Spindle 26 Servo Motor 30 Grinding Wheel 34 Grinding Wheel 54 Chuck Table 55a First Suction Area 55b Second Suction Area

Claims (3)

The first wafer on which the orientation flat indicating the crystal orientation is formed and the orientation flat smaller than the orientation flat on the first wafer are formed, and the first wafer and the second wafer having substantially the same diameter are bonded to each other. A grinding apparatus for grinding the exposed surface of the first wafer and the exposed surface of the second wafer of the laminated wafer,
A chuck table having a holding surface for sucking and holding the laminated wafer;
Grinding means for rotatably supporting a grinding wheel in which a grinding wheel for grinding a laminated wafer held on the chuck table is annularly arranged;
The holding surface of the chuck table has a first suction area corresponding to the shape of the first wafer and a second suction area corresponding to the shape of the protruding portion of the second wafer from the first wafer. Including
When grinding the exposed surface of the first wafer, the first and second suction areas are operated to suck and hold the second wafer,
A grinding apparatus characterized in that when the exposed surface of the second wafer is ground, the first wafer is sucked and held by acting the first suction region. A first cassette placement section on which a first cassette containing a plurality of laminated wafers is placed;
A second cassette mounting portion on which a second cassette in which the laminated wafer after grinding is stored is mounted;
Unloading means for unloading the laminated wafer from the first cassette mounted on the first cassette mounting section;
Positioning means for temporarily placing the laminated wafer unloaded from the first cassette by the unloading means, centering the laminated wafer and detecting the orientation flat to position the orientation flat in a predetermined direction;
First conveying means for conveying the laminated wafer temporarily placed on the positioning means to the chuck table;
A second conveying means for carrying out the laminated wafer after grinding from the chuck table;
Cleaning means for cleaning the laminated wafer carried out by the second transport means;
A loading means for storing the laminated wafer cleaned by the cleaning means in the second cassette;
At least one of the carry-out means and the carry-in means has an inversion function for inverting the laminated wafer,
After grinding the exposed surface of the first wafer or the exposed surface of the second wafer of the laminated wafer, the laminated wafer is reversed by the unloading means or the carrying-in means having a reversing function, and the exposed surface or the second wafer of the second wafer is reversed. The grinding apparatus according to claim 1, wherein an exposed surface of one wafer is ground.   The grinding apparatus according to claim 2, wherein the carry-out means also serves as the carry-in means.

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