JP2011023618A - Wafer cleaning apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for cleaning a wafer having a circular recess on a rear surface corresponding to a device region. <P>SOLUTION: The wafer cleaning apparatus for cleaning a circular recess 31 of a wafer 11 having a circular recess 31 formed on the rear surface corresponding to a device region 17 and an annular reinforcing part 33 formed on the outer circumference of the circular recess 31 includes: a cleaning means having a disc-like cleaning pad 84 abutting on the bottom surface of the circular recess 31 of a wafer held on a rotary chuck table 46 and rotating; a vertically driving means 80 for allowing the cleaning pad 84 to be positioned higher than the height of the annular reinforcing part 33 and moving the cleaning means between a retracting position; and a horizontally driving means 70 for horizontally swinging the cleaning pad 84 positioned at the cleaning position. The total of the distance of reciprocation of the cleaning pad 84 by the horizontally driving means 70 and the diameter of the cleaning pad 84 is larger than the radius of the circular recess 31 and not larger than the diameter, and the center of the cleaning pad 84 moves through the center of the circular recess 31. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a wafer cleaning apparatus for cleaning a wafer such as a semiconductor wafer.

  In the semiconductor device manufacturing process, a plurality of regions are partitioned by dividing lines called streets arranged in a lattice pattern on the surface of a semiconductor wafer having a substantially disk shape, and devices such as ICs and LSIs are placed in the partitioned regions. Form. Then, the semiconductor wafer is cut into individual semiconductor chips (devices) by cutting the semiconductor wafer along a street with a cutting device.

  The divided wafer is formed to have a predetermined thickness by grinding the back surface before cutting along the street. In recent years, in order to achieve a reduction in weight and size of electrical equipment, it has been required to make the wafer thinner, for example, about 50 μm.

  Such thin wafers are difficult to handle and may be damaged during transportation. Therefore, there is disclosed a processing method in which only the back surface corresponding to the device region of the wafer is ground to form a circular recess, and an annular reinforcing portion is formed on the back surface of the wafer corresponding to the outer peripheral surplus region surrounding the device region. Proposed in the Gazette.

  The wafer thus processed is usually subjected to a grinding process, and a metal film such as gold is formed on the ground surface. At that time, it is necessary to remove the grinding debris remaining on the ground surface and keep the ground surface clean. Conventionally, the ground wafer is cleaned and spin-dried by a spinner cleaning device.

JP 2007-19461 A

  However, the spinner cleaning device is a cleaning method in which water is sprayed at high speed while rotating the wafer at a high speed, and the grinding scraps are washed away to the outside of the wafer. Since there is an annular reinforcing portion on the outer periphery of the wafer, there is a problem that grinding scraps stay at the root of the annular reinforcing portion.

  If cleaning is performed by bringing a cleaning pad made of an elastic material such as sponge or rubber into contact with the wafer so as not to damage the surface of the wafer made of a brittle material, a higher cleaning effect is expected, but an annular shape having a height of several hundred μm is expected. If it rides on the reinforcing part, a gap is formed at the base of the cleaning pad and the annular reinforcing part, and grinding scraps remain at the base of the annular reinforcing part. In addition, since the wafers have various sizes and the width of the outer peripheral annular reinforcing portion varies from 1 to 10 mm, it is necessary to mount a cleaning pad of a size suitable for each wafer.

  The present invention has been made in view of these points, and an object of the present invention is to provide a wafer cleaning apparatus that can efficiently and cleanly clean a circular recess formed on the back surface of a device region of a wafer. It is.

  According to the present invention, a device area on which a plurality of devices are formed and held on a rotatable chuck table and an outer peripheral surplus area surrounding the device area are formed on the surface, and a circular shape is formed on the back surface corresponding to the device area. A wafer cleaning apparatus for cleaning a circular concave portion of a wafer having a concave portion formed and an annular reinforcing portion formed on an outer peripheral side of the circular concave portion, wherein the wafer is rotated while being in contact with the bottom surface of the circular concave portion of the wafer. A cleaning means having a disc-shaped cleaning pad; a cleaning position where the cleaning pad contacts the bottom surface of the circular recess; and a retreat position where the cleaning pad is positioned higher than the height of the annular reinforcing portion. A vertical drive means for moving the cleaning means; and a horizontal drive means for reciprocating the cleaning means in the horizontal direction and swinging the cleaning pad positioned at the cleaning position in the horizontal direction. The sum of the distance that the cleaning pad reciprocates by the horizontal driving means and the diameter of the cleaning pad is greater than the radius of the circular recess and less than the diameter, and the center of the cleaning pad passes through the center of the circular recess. A wafer cleaning apparatus is provided, which is characterized in that the wafer is moved.

  Preferably, the cleaning pad is formed from a disk-shaped elastic body such as sponge or rubber.

  According to the present invention, since the cleaning pad comes into contact with the circular concave portion of the wafer to perform cleaning, a high cleaning effect can be expected, and since cleaning is performed in contact with the root of the annular reinforcing portion, it is possible to prevent unwashed grinding waste. Further, since the cleaning range can be set as appropriate, a single cleaning pad can cope with circular recesses of various sizes, contributing to a reduction in the number of parts and a reduction in replacement man-hours.

It is a surface side perspective view of a semiconductor wafer. It is a back surface side perspective view of the semiconductor wafer by which the protective tape was stuck on the surface. It is an external appearance perspective view of the grinding device provided with the wafer cleaning device of the present invention. It is a perspective view which shows the relationship between the wafer hold | maintained at the chuck table at the time of grinding, and a grinding wheel. It is explanatory drawing of the circular recessed part grinding process implemented by the grinding device. It is sectional drawing of the semiconductor wafer in which the circular recessed part grinding process was implemented. It is a partial cross section side view of a wafer washing device, (A) shows a retreat position and (B) shows a washing position, respectively. It is a schematic diagram which shows the relationship between the circular recessed part and cleaning pad of a wafer at the time of washing | cleaning. It is a figure which shows the example of various shapes of a washing | cleaning pad.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view of a semiconductor wafer before being processed to a predetermined thickness. A semiconductor wafer 11 shown in FIG. 1 is made of, for example, a silicon wafer having a thickness of 700 μm, and a plurality of streets 13 are formed in a lattice shape on the surface 11a, and a plurality of streets partitioned by the plurality of streets 13 are formed. A device 15 such as an IC or LSI is formed in the region.

  The semiconductor wafer 11 configured as described above includes a device region 17 in which the device 15 is formed, and an outer peripheral surplus region 19 that surrounds the device region 17. A notch 21 is formed on the outer periphery of the semiconductor wafer 11 as a mark indicating the crystal orientation of the silicon wafer.

  A protective tape 23 is attached to the surface 11a of the semiconductor wafer 11 by a protective tape attaching process. Accordingly, the front surface 11a of the semiconductor wafer 11 is protected by the protective tape 23, and the back surface 11b is exposed as shown in FIG. 2 during grinding.

  Referring to FIG. 3, an external perspective view of the grinding device 2 is shown. The grinding apparatus 2 performs a grinding method in which a back surface corresponding to the device region 17 of the semiconductor wafer 11 is ground to form a circular recess, and an annular reinforcing portion including an outer peripheral surplus region 19 is formed on the outer peripheral side of the circular recess. Suitable for

  Reference numeral 4 denotes a base of the grinding apparatus 2, and two columns 6a and 6b are provided upright at the rear of the base. A pair of guide rails (only one is shown) 8 extending in the vertical direction is fixed to the column 6a.

  A rough grinding unit 10 is mounted along the pair of guide rails 8 so as to be movable in the vertical direction. The rough grinding unit 10 is attached to a moving base 12 whose housing 20 moves up and down along a pair of guide rails 8.

  The rough grinding unit 10 includes a housing 20, a spindle 25 rotatably accommodated in the housing 20, a servo motor 22 that rotationally drives the spindle 25, a mounter 27 fixed to the tip of the spindle 25, and a mounter 27. A grinding wheel 24 having a plurality of grinding wheels 26 for rough grinding, which are detachably mounted, is included.

  The rough grinding unit 10 includes a rough grinding unit moving mechanism 18 including a ball screw 14 and a pulse motor 16 that move the rough grinding unit 10 up and down along a pair of guide rails 8. When the pulse motor 16 is pulse-driven, the ball screw 14 rotates and the moving base 12 is moved in the vertical direction.

  A pair of guide rails 19 (only one is shown) 19 extending in the vertical direction are also fixed to the other column 6b. A finish grinding unit 28 is mounted along the pair of guide rails 19 so as to be movable in the vertical direction.

  The finish grinding unit 28 is attached to a moving base (not shown) in which the housing 36 moves in the vertical direction along the pair of guide rails 19. The finish grinding unit 28 includes a housing 36, a spindle 37 rotatably accommodated in the housing 36, a servo motor 38 that rotationally drives the spindle 37, a mounter 39 fixed to the tip of the spindle 37, and the mounter 39 A grinding wheel 40 having a grinding wheel 42 for finish grinding, which is detachably mounted, is included.

  The finish grinding unit 28 includes a finish grinding unit moving mechanism 34 including a ball screw 30 and a pulse motor 32 that move the finish grinding unit 28 in the vertical direction along the pair of guide rails 19. When the pulse motor 32 is driven, the ball screw 30 rotates and the finish grinding unit 28 is moved in the vertical direction.

  The grinding device 2 includes a turntable 44 disposed so as to be substantially flush with the upper surface of the base 4 on the front side of the columns 6a and 6b. The turntable 44 is formed in a relatively large-diameter disk shape, and is rotated in a direction indicated by an arrow 45 by a rotation drive mechanism (not shown).

  On the turntable 44, three chuck tables 46 are arranged so as to be rotatable in a horizontal plane, spaced from each other by 120 ° in the circumferential direction. The chuck table 46 has a suction chuck formed in a disk shape by a porous ceramic material, and sucks and holds the wafer placed on the holding surface of the suction chuck by operating a vacuum suction means.

  The three chuck tables 46 arranged on the turntable 44 have a wafer carry-in / out area A, a rough grinding area B, a finish grinding area, and a wafer carry-in / out area when the turntable 44 is appropriately rotated. Sequentially moved to A.

  In the front portion of the base 4, there are a first wafer cassette 50, a second wafer cassette 52, a wafer transfer robot 54, a positioning table 56 having a plurality of positioning pins 58, and a wafer carry-in mechanism (loading arm) 60. A wafer unloading mechanism (unloading arm) 62 and a spinner unit 63 are disposed.

  A support member 66 of a wafer cleaning device 64 is attached on the base 4 so as to straddle the turntable 44. A pair of guide rails 68 are attached to both sides of the support member 66. For example, the X-axis moving member 72 is driven by driving a horizontal driving means 70 (see FIG. 7) including a ball screw 69 and a pulse motor (not shown). Is moved in the X-axis direction.

  As shown in FIG. 7, the X-axis moving member 72 is attached with vertical drive means 80 including a ball screw 76 and a pulse motor 78. A nut mounted on a cleaning unit (cleaning means) 74 is screwed onto the ball screw 76 of the vertical drive means 80. When the pulse motor 78 is driven, the cleaning unit 74 is moved in the vertical direction (Z-axis direction). .

  The cleaning unit 74 has a spindle 82 rotated in the direction of arrow B by a motor (not shown), and a cleaning pad 84 is attached to the tip of the spindle 82. The cleaning pad 84 is formed of a disk-like elastic body such as sponge or soft rubber.

  The cleaning pad 84 is not limited to the disk shape shown in FIG. 9A, and various types of cleaning pads 84B to 84E as shown in FIGS. 9B to 9E can be employed. Reference numeral 85 indicates a void or gap.

  The grinding operation of the grinding device 2 configured as described above will be described below. The semiconductor wafer accommodated in the first wafer cassette 50 is transported by the vertical motion and the forward / backward motion of the wafer transport robot 54 and is placed on the wafer positioning table 56.

  The wafer placed on the wafer positioning table 56 is centered by a plurality of positioning pins 58 and then moved to the chuck table 46 positioned in the wafer loading / unloading area A by the turning operation of the loading arm 60. It is placed and sucked and held by the chuck table 46.

  Next, the turntable 44 is rotated 120 degrees, and the chuck table 46 holding the wafer is positioned in the rough grinding region B. As shown in FIG. 4, the grinding wheel 24 detachably attached to the mount 27 with bolts 29 grinds only the back surface corresponding to the device region 17 of the wafer 11 and surrounds the device region 17 with an outer peripheral surplus region 19. This grinding wheel is suitable for forming the annular reinforcing portion 33 on the back surface of the wafer corresponding to the above.

  As best shown in FIG. 5, the rotation center P1 of the chuck table 46 and the rotation center P2 of the grinding wheel 24 are eccentric, and the outer diameter of the grinding wheel 26 is the device region 17 of the wafer 11 and the outer peripheral surplus region 19. The diameter is set to be smaller than the diameter of the boundary line 35 and larger than the radius of the boundary line 35, so that the annular grinding wheel 26 passes through the rotation center P 1 of the chuck table 46.

  While rotating the chuck table 46 in the direction indicated by the arrow a at 300 rpm and rotating the grinding wheel 24 in the direction indicated by the arrow b at 6000 rpm, the grinding feed mechanism 18 is operated to move the grinding wheel 26 of the grinding wheel 24 to the wafer 11. Make contact with the back of the. Then, the grinding wheel 24 is ground by a predetermined amount at a predetermined grinding feed speed.

  As a result, as shown in FIG. 6, the region corresponding to the device region 17 is ground to form a circular recess 31 and the region corresponding to the outer peripheral surplus region 19 remains on the back surface of the semiconductor wafer 11. An annular reinforcing portion 33 is formed.

  After the rough grinding, the wafer 11 is positioned in the finish grinding region by further rotating the turntable 44 by 120 degrees, and finish grinding is performed by the finish grinding wheel 40 having a grinding wheel for finish grinding of the finish grinding unit 28. The This finish grinding is the same as the rough grinding described with reference to FIGS. 4 to 6, and the ground surface is finish ground.

  The chuck table 46 holding the wafer 11 that has finished finish grinding is positioned in the wafer carry-in / out area A by further rotating the turn table 46 by 120 degrees.

  The wafer 11 is cleaned by the wafer cleaning device 64 with respect to the ground wafer 11 positioned in the wafer loading / unloading area A. Hereinafter, the cleaning operation of the wafer 11 will be described in detail with reference to FIGS.

  The cleaning unit 74 shown in FIG. 7A is positioned at a retracted position separated from the wafer 11 held on the chuck table 46 by a predetermined distance. This retracted position needs to be at least a position spaced above the height of the annular reinforcing portion 33 of the wafer 11 held on the chuck table 46.

  In order to start the cleaning of the wafer 11, the cleaning unit 74 positioned at the retracted position shown in FIG. 7A is lowered in the direction of the arrow C by the vertical drive means 80, as shown in FIG. 7B. The cleaning pad 84 is brought into contact with the circular recess 31 of the wafer 11.

  The chuck table 46 is rotated in the direction of arrow A, the cleaning water is sprayed from the nozzle 86, and the cleaning pad 84 is further rotated in the direction of arrow B while the bottom of the circular recess 31 of the wafer 11 is rubbed with the cleaning pad 84. Wash.

  At the time of this cleaning, the cleaning pad 84 having the diameter D1 is cleaned while being reciprocated in the horizontal direction by the distance S by the horizontal driving means 70 as shown in FIG. Accordingly, the bottom of the circular recess 31 of the wafer 11 can be cleaned evenly, and the boundary portion between the circular recess 31 and the annular reinforcing portion 33 can also be cleaned with the cleaning pad 84.

  At the time of this cleaning, the sum of the distance S that the cleaning pad 84 reciprocates and the diameter D1 of the cleaning pad 84 needs to be larger than the radius of the circular recess 31 of the wafer 11 and less than the diameter. Furthermore, the center of the cleaning pad 84 needs to move left and right through the center of the circular recess 31.

  In the above-described embodiment, the chuck table 46 and the cleaning pad 84 rotate in the same direction, but the rotation direction of the cleaning pad 84 and the chuck table 46 may be either forward or reverse.

  The shape of the cleaning pad 84 may be any shape as shown in FIG. 9, but in the case of the bar-shaped cleaning pad 84D shown in FIG. 9D and the cross-shaped cleaning pad 84E shown in FIG. The outermost peripheral portion is preferably formed in an R shape along the shape of the circular recess 31 of the wafer.

  In the embodiment described above, cleaning water is supplied from the nozzle 86 during cleaning, and a nozzle that injects high-pressure water from a high-pressure pump or a two-fluid nozzle that includes high-pressure air and water is provided. Also good.

  After the grinding, the wafer 11 is sucked and held by the unloading arm 62 and conveyed to the spinner unit 63. In the spinner unit 63, the wafer 11 is again cleaned and spin-dried, and is further gripped by the wafer transfer robot 54 and accommodated in the second wafer cassette 52.

2 Grinding device 10 Coarse grinding unit 11 Semiconductor wafer 17 Device region 19 Peripheral surplus region 24 Grinding wheel 28 Finish grinding unit 31 Circular recess 33 Annular reinforcing portion 46 Chuck table 64 Cleaning device 74 Cleaning unit 84 Cleaning pad 86 Nozzle

Claims (2)

The device has a device region that is held on a rotatable chuck table and has a plurality of devices formed thereon and an outer peripheral surplus region that surrounds the device region, and a circular recess is formed on the back surface corresponding to the device region, A wafer cleaning device for cleaning the circular recess of a wafer having an annular reinforcing portion formed on the outer peripheral side of the circular recess,
A cleaning means having a disk-shaped cleaning pad that rotates while cleaning the bottom surface of the circular recess of the wafer;
A vertical drive means for moving the cleaning means between a cleaning position where the cleaning pad contacts the bottom surface of the circular recess and a retreat position where the cleaning pad is positioned higher than the height of the annular reinforcement;
A horizontal drive means for reciprocally moving the cleaning means in the horizontal direction and swinging the cleaning pad positioned at the cleaning position in the horizontal direction;
The sum of the distance that the cleaning pad reciprocates by the horizontal driving means and the diameter of the cleaning pad is greater than the radius of the circular recess and less than or equal to the diameter;
A wafer cleaning apparatus, wherein the center of the cleaning pad moves through the center of the circular recess.   The wafer cleaning apparatus according to claim 1, wherein the cleaning pad is formed of a disk-shaped elastic body.

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