Gettering layer forming device and processing device

Abstract

To efficiently form a gettering layer on the back surface of a ground wafer in a short time.SOLUTION: A gettering layer forming apparatus 70 includes a spinner table 51 having a spinner holding surface 511 for suction-holding a wafer 100, and an annular mounting surface 512 disposed radially outside of the spinner holding surface 511, an annular portion 71 that is placed on the mounting surface 512 to surround the wafer 100 and form a water tank 73, a moving mechanism 72 for placing the annular portion 71 on or away from the mounting surface 512, an abrasive grain nozzle 74 for inputting free abrasive grains into a water tank 73, a water nozzle 52 for supplying water to the water tank 73 to submerge the wafer 100, an ultrasonic horn 75 that propagates ultrasonic vibrations to the free abrasive grains, and horizontal movement mechanisms 83 and 84 for relatively moving the ultrasonic horn 75 and the spinner table 51 in a direction parallel to the spinner holding surface 511. A gettering layer is formed on the back surface of the wafer 100 submerged in the water tank 73 by using the free abrasive grains to which the ultrasonic vibrations have been propagated.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a gettering layer forming apparatus for forming a gettering layer on the back surface of a wafer, and a processing apparatus equipped with this gettering layer forming apparatus. [Background technology]

[0002] As various electronic devices are required to be smaller and thinner, the semiconductor devices used in these electronic devices are also trending toward being smaller and thinner. Specifically, in the semiconductor device manufacturing process, the surface of a disk-shaped semiconductor wafer (hereinafter simply referred to as a "wafer") is partitioned into a large number of rectangular regions by cutting lines called streets, which are arranged in a grid pattern, and devices such as ICs and LSIs are formed in each rectangular region. By cutting the wafer with a large number of devices formed in this way along the streets, multiple semiconductor chips are formed.

[0003] To reduce the size and thickness of individual semiconductor chips, the backside of the wafer (the side opposite to the side on which the devices are formed) is usually ground to a predetermined thickness before cutting the wafer along the streets. This wafer grinding is performed by pressing a grinding wheel rotating at high speed against the backside of the wafer, but this grinding process forms a processing strain layer consisting of microcracks of about 1 μm on the backside of the wafer. This causes a problem of reduced flexural strength of the wafer, especially when the wafer is ground to a thickness of 100 μm or less.

[0004] Therefore, the back surface of the ground wafer is polished or etched to remove the processing strain.

[0005] However, if the back surface of the wafer is ground and then polished or etched to remove the strain layer, the gettering effect is lost. Here, the gettering effect refers to the effect of forming gettering sites (crystal defects, strain, etc.) inside or on the back surface of the wafer, and capturing and fixing impurities (heavy metal impurities, etc.) that cause metal contamination at these gettering sites.

[0006] Therefore, Patent Document 1 proposes a wafer processing method in which free abrasive grains placed in water in a tank are ultrasonically vibrated, the wafer is submerged in the water in the tank with its back side facing down, and the ultrasonically vibrating free abrasive grains collide with the back side of the wafer to form a gettering layer on the back side. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-303223 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the method proposed in Patent Document 1 has the problem that it takes a long time to form a gettering layer because the free abrasive grains are not always in contact with the back surface of the wafer.

[0009] The present invention has been made in consideration of the above problems, and its object is to provide a gettering layer forming apparatus and processing apparatus that can efficiently form a gettering layer on the back surface of a ground wafer in a short period of time. [Means for solving the problem]

[0010] The first invention for achieving the above-mentioned object is a gettering layer forming apparatus for forming a gettering layer on the backside of a wafer, comprising: a holding table having a holding surface that suction-holds the front side of the wafer and an annular mounting surface arranged radially outside the holding surface; a circular ring portion that is placed on the mounting surface and surrounds the wafer held on the holding surface to form a water tank; a moving mechanism for placing the circular ring portion on or separating it from the mounting surface; an abrasive grain feeding section that feeds free abrasive grains into the water tank; a water nozzle that supplies water to the water tank to submerge the wafer; an ultrasonic horn that propagates ultrasonic vibrations to the free abrasive grains; and a horizontal moving mechanism that moves the ultrasonic horn and the holding table relatively in a direction parallel to the holding surface, wherein the free abrasive grains to which the ultrasonic vibrations are propagated form a gettering layer on the backside of the wafer that is held on the holding surface and submerged.

[0011] Further, a second invention is a processing apparatus for processing the back surface of a wafer, comprising: a chuck table having a chuck holding surface for holding the front side of the wafer and an annular mounting surface arranged radially outside the chuck holding surface; a processing mechanism for processing the wafer held on the chuck table; and a gettering layer forming device for forming a gettering layer on the back surface of the wafer, wherein the gettering layer forming device comprises: a circular ring portion that is placed on the mounting surface and surrounds the wafer held on the chuck holding surface to form a water tank; an abrasive grain feeding portion that feeds free abrasive grains into the water tank; a water nozzle that supplies water to the water tank to submerge the wafer; an ultrasonic horn that propagates ultrasonic vibrations to the free abrasive grains; and a horizontal movement mechanism that moves the ultrasonic horn and the chuck table relatively in a direction parallel to the chuck holding surface, and wherein a gettering layer is formed on the back surface of the wafer held on the chuck holding surface and submerged by the free abrasive grains to which the ultrasonic vibrations are propagated.

[0012] Furthermore, a third invention is a processing apparatus for processing the back surface of a wafer, comprising: a chuck table that holds the front side of the wafer on a chuck holding surface; a processing mechanism that processes the back surface of the wafer held on the chuck holding surface; a spinner cleaning mechanism that cleans the wafer; a transport mechanism that transports the wafer from the chuck table to the spinner cleaning mechanism; and a gettering layer forming device that forms a gettering layer on the back surface of the wafer, wherein the spinner cleaning mechanism comprises a spinner table having a spinner holding surface that holds the front side of the wafer and an annular mounting surface arranged radially outward of the spinner holding surface; a cleaning nozzle that sprays a cleaning liquid onto the back surface of the wafer held on the spinner holding surface; and a gettering layer forming device that forms a gettering layer on the backside of the wafer. The gettering layer forming device includes a circular ring portion that is placed on the mounting surface and surrounds the wafer held on the spinner holding surface to form a water tank, an abrasive grain feeding portion that feeds free abrasive grains into the water tank, and an ultrasonic horn that propagates ultrasonic vibrations to the free abrasive grains. Water is supplied from the cleaning nozzle to the water tank to submerge the wafer held on the spinner holding surface, and the spinner table is rotated, and a gettering layer is formed on the backside of the wafer held on the spinner holding surface and submerged by the free abrasive grains to which the ultrasonic vibrations are propagated. [Effects of the Invention]

[0013] According to the present invention, ultrasonic vibrations are transmitted from an ultrasonic horn to free abrasive grains contained in the water in a water tank, and the free abrasive grains vibrate ultrasonically, creating countless fine scratches on the back surface of the wafer, thereby forming a gettering layer on the back surface of the wafer.The free abrasive grains contained in the water in the water tank vibrate ultrasonically while always remaining on the back surface of the wafer, and the free abrasive grains moving laterally and diagonally create fine scratches that cross in a crisscross pattern on the back surface of the wafer, so that a gettering layer is formed efficiently in a short time to capture and fix impurities (such as heavy metal impurities) that cause metal contamination at the gettering site. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a perspective view showing a partly broken away grinding device which is one embodiment of a processing device according to the present invention; [Figure 2] 1 is a perspective view showing a state before a circular portion of a gettering layer forming apparatus according to the present invention is placed on a spinner table. FIG. [Figure 3] 1 is a perspective view showing a state in which a circular portion of a gettering layer forming apparatus according to the present invention is placed on a spinner table. [Figure 4] 1 is a perspective view showing a state in which water and free abrasive grains are being supplied to a water tank formed between a circular ring portion of a gettering layer forming apparatus according to the present invention and a wafer. FIG. [Figure 5] 10 is a side cross-sectional view showing a state in which water and free abrasive grains are being supplied to a water tank formed between the annular portion of the gettering layer forming apparatus according to the present invention and the wafer. FIG. [Figure 6] 1 is a perspective view showing a state in which ultrasonic vibrations are propagated by an ultrasonic horn to loose abrasive grains supplied to a water tank of a gettering layer forming apparatus according to the present invention. FIG. [Figure 7] 1 is a cutaway side view showing a state in which ultrasonic vibrations are propagated by an ultrasonic horn to loose abrasive grains supplied to a water tank of a gettering layer forming apparatus according to the present invention. FIG. [Figure 8] 1 is a plan view showing the positional relationship between an ultrasonic horn and a wafer in a gettering layer forming apparatus according to the present invention. FIG. [Figure 9] 10 is a plan view showing another embodiment of the positional relationship between the ultrasonic horn and the wafer in the gettering layer forming apparatus according to the present invention. FIG. [Figure 10] 10 is a perspective view showing a state in which the annular portion is pulled up after a gettering layer has been formed on the back surface of the wafer by the gettering layer forming apparatus according to the present invention. FIG. [Figure 11] 1 is a cutaway side view showing the configuration of an abrasive grain recovery system that recovers and reuses free abrasive grains used in forming a gettering layer in a gettering device according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0016] [Wafer grinding equipment] Hereinafter, the overall configuration of a wafer grinding apparatus as one embodiment of a processing apparatus according to the present invention will be described with reference to FIG.

[0017] The grinding apparatus 1 shown in FIG. 1 grinds the back surface (top surface in FIG. 1) of a disk-shaped wafer 100, which is a workpiece, and includes the following components.

[0018] That is, the grinding apparatus 1 comprises, as main components, a chuck table 10 that holds the front surface (the bottom surface in FIG. 1) of the wafer 100 on a chuck holding surface 11, a grinding mechanism 30 that is a processing mechanism that grinds the back surface of the wafer 100 held on the chuck holding surface 11, a spinner cleaning mechanism 50 that cleans the wafer 100, a transport mechanism 60 that transports the wafer 100, and a gettering layer forming device 70 that forms a gettering layer on the back surface of the wafer 100. The gettering layer forming device 70 according to the present invention is provided integrally with the spinner cleaning mechanism 50, and the details of its configuration will be described later.

[0019] 1, a plurality of devices (not shown) are formed on the surface facing downward, and these devices are protected by a protective tape (not shown) attached to the surface of the wafer 100. The front surface (the lower surface in FIG. 1) of the wafer 100 is suction-held on the chuck holding surface 11 of the chuck table 10, and the back surface (the upper surface in FIG. 1) is ground by the grinding mechanism 30.

[0020] Next, the configurations of the chuck table 10, grinding mechanism 30, spinner cleaning mechanism 50, transfer mechanism 60, and gettering layer forming device 70, which are the main components of the grinding apparatus 1, will be described.

[0021] (Chuck table) The chuck table 10 is a disk-shaped member, and a disk-shaped porous member 12 made of porous ceramic or the like is incorporated in the center thereof. The outer peripheral surface of the upper surface of the chuck table 10 other than the chuck holding surface 11 forms an annular mounting surface 13. Here, the upper surface of the porous member 12 forms the chuck holding surface 11 that suction-holds the disk-shaped wafer 100.

[0022] The chuck table 10 is rotated around its axis at a predetermined speed by a rotation mechanism 14 provided below the chuck table 10 and including an electric motor (not shown) as a drive source, and can be moved back and forth in the Y-axis direction (front-back direction) by a horizontal movement mechanism 20 provided below the chuck table 10. Here, the horizontal movement mechanism 20 is configured as follows.

[0023] 1, the horizontal movement mechanism 20 is a mechanism for reciprocating the chuck table 10 in the horizontal direction (Y-axis direction) relative to the chuck holding surface 11, and is disposed on a rectangular block-shaped internal base 3 housed in a rectangular box-shaped base 2 that is long in the Y-axis direction (front-rear direction). A slider 21 is disposed on the internal base 3, and this slider 21 is slidable in the Y-axis direction along a pair of left and right guide rails 22 that are arranged parallel to each other along the Y-axis direction (front-rear direction). Therefore, the chuck table 10 supported by the slider 21 and the rotation mechanism 14 including an electric motor and the like are slidable in the Y-axis direction together with the slider 21.

[0024] A rotatable ball screw shaft 23 extending in the Y-axis direction (front-rear direction) is disposed between a pair of left and right guide rails 22 on the internal base 3, and one end of the ball screw shaft 23 in the Y-axis direction (the left end in FIG. 1) is connected to a reversible electric motor 24, which serves as a drive source. The other end of the ball screw shaft 23 in the Y-axis direction (the right end in FIG. 1) is rotatably supported by a bearing 25 erected on the internal base 3. A nut member (not shown) protruding downward from the slider 21 is screwed onto the ball screw shaft 23.

[0025] Therefore, when the electric motor 24 is rotated forward or backward to rotate the ball screw shaft 23 forward or backward, a nut member (not shown) that is threaded onto the ball screw shaft 23 slides together with the slider 21 along the ball screw shaft 23 in the Y-axis direction (front-back direction), and the chuck table 10 also moves integrally along the Y-axis direction together with the slider 21. As a result, the wafer 100 suction-held on the chuck holding surface 11 of the chuck table 10 also moves along the Y-axis direction. The electric motor 24 is electrically connected to a control unit (not shown), and its drive is controlled by the control unit.

[0026] 1, in the grinding apparatus 1 according to this embodiment, a rectangular opening 4 that is long in the Y-axis direction is formed in the upper surface of the base 2, and a chuck table 10 faces this opening 4. The periphery of the chuck table 10 at the opening 4 is covered with a rectangular plate-shaped cover 5, and the front and rear portions of the cover 5 at the opening 4 (in the -Y-axis direction and +Y-axis direction) are covered by bellows-shaped extendable covers 6 and 7 that move and extend together with the cover 5. Therefore, regardless of the position of the chuck table 10 on the Y-axis, the opening 4 is always closed by the cover 5 and the extendable covers 6 and 7, so that foreign matter is reliably prevented from entering the base 2 through the opening 4.

[0027] (Grinding mechanism) 1, the grinding mechanism 30 includes a holder 31 that is open at the top, a spindle motor 32 that is a rotational drive source that is fixed to the holder 31 in a vertically disposed state, a spindle 33 that is driven to rotate by the spindle motor 32, a disk-shaped mount 34 that is attached to the lower end of the spindle 33, and a grinding wheel 35 that is detachably attached to the underside of the mount 34. The grinding wheel 35 is composed of a disk-shaped base 351 and a plurality of grinding stones 352 that are processing tools that are attached in an annular shape to the underside of the base 351. The grinding stones 352 are processing tools for grinding the wafer 100, and their undersides form a grinding surface that comes into contact with the wafer 100. The spindle motor 32 is electrically connected to a control unit (not shown), and its drive is controlled by the control unit.

[0028] The grinding mechanism 30 can be raised and lowered in a direction (Z-axis direction) perpendicular to the chuck holding surface 11 of the chuck table 10 by a vertical movement mechanism 40, and this vertical movement mechanism 40 is disposed on the −Y-axis direction end face (front face) of a rectangular box-shaped column 8 that is erected vertically on the +Y-axis direction end face (rear end face) of the upper surface of the base 2, as shown in FIG. 1 . The vertical movement mechanism 40 raises and lowers a rectangular plate-shaped lift plate 41 attached to the back face of the holder 31, together with the holder 31, the spindle motor 32, the grinding wheel 35, and the like held by the holder 31, in the Z-axis direction along a pair of left and right guide rails 42. The pair of left and right guide rails 42 are disposed perpendicular to the front face of the column 8 and parallel to each other.

[0029] A rotatable ball screw shaft 43 is erected vertically along the Z-axis direction (up-down direction) between the pair of left and right guide rails 42, and the upper end of the ball screw shaft 43 is connected to a reversible electric motor 44, which serves as a drive source. The electric motor 44 is mounted in a vertical position via a rectangular plate-shaped bracket 45 attached to the upper surface of the column 8. The lower end of the ball screw shaft 43 is rotatably supported by the column 8, and a nut member (not shown) that protrudes horizontally from the back surface of the lifting plate 41 toward the rear (+Y-axis direction) is screwed onto the ball screw shaft 43.

[0030] Therefore, when the electric motor 44 is driven to rotate the ball screw shaft 43 forward or backward, the lifting plate 41, to which a nut member (not shown) that screws onto the ball screw shaft 43 is attached, moves up and down along the Z-axis direction together with the grinding mechanism 30. As shown in Fig. 1, a thickness measuring device 26 that measures the thickness of the wafer 100 during grinding is disposed near the chuck table 10 on the base 2. The electric motor 44 is electrically connected to a control unit (not shown), and its drive is controlled by the control unit.

[0031] (Spinner cleaning mechanism) The spinner cleaning mechanism 50 is a mechanism for cleaning the back surface of the wafer 100 after the back surface has been ground and a gettering layer has been formed on the back surface by the gettering layer forming device 70, and is equipped with a spinner table 51 that holds and rotates the wafer 100 after grinding, and a cleaning nozzle 52 that sprays a cleaning liquid toward the back surface of the wafer 100.

[0032] (Transport mechanism) The transfer mechanism 60 includes a carry-in / out robot 61, a first transfer arm 62, and a second transfer arm 63. The carry-in / out robot 61 takes out one wafer 100 from a cassette 101 that stores a plurality of wafers 100 before grinding and transfers it to an alignment table 102, and also transfers the wafer 100, the back surface of which has been cleaned by the spinner cleaning mechanism 50, to a cassette 103 and stores it in the cassette 103.

[0033] In addition, the first transport arm 62 has the function of holding the wafer 100 before grinding that has been aligned on the alignment table 102 and transporting it to the chuck table 10, and the second transport arm 62 has the function of holding the wafer 100 after grinding and transporting it from the chuck table 10 to the spinner table 51 of the spinner cleaning mechanism 50. (Gettering layer forming device) The gettering layer forming apparatus 70 according to the present invention is provided integrally with the spinner cleaning apparatus 50 as described above, and the details of its configuration will be described below with reference to FIG. The gettering layer forming apparatus 70 shown in Figure 2 is an apparatus for forming a gettering layer on the back surface of a wafer 100, and is equipped with the spinner table 51 provided in the spinner cleaning mechanism 50, an annular portion 71, a moving mechanism 72 for moving the annular portion 71 up and down, an abrasive nozzle 74 constituting an abrasive grain feeding section that feeds free abrasive grains into a water tank 73 (see Figures 3 to 7) formed by the annular portion 71 and the wafer 100, a water nozzle 52 (used as a cleaning nozzle when cleaning the wafer 100) that supplies water to the water tank 73, an ultrasonic horn 75 that propagates ultrasonic vibrations to the free abrasive grains in the water tank 73, and a horizontal moving mechanism (a rotating mechanism 83 (see Figure 5) described later) that horizontally rotates the abrasive grain nozzle 74 and the water nozzle 52 relative to the spinner holding surface 511 of the spinner table 51.

[0034] The spinner table 51 has a circular spinner holding surface 511 on its top surface around which an annular mounting surface 512 is formed, and is attached to the upper end of a rotation shaft 77 that extends vertically upward from a rotation mechanism 76 located below. A rotary joint 78 is connected to the lower end of the rotation mechanism 76. The rotation mechanism 76 is electrically connected to a control unit (not shown), and its drive is controlled by the control unit.

[0035] The annular portion 71 is a ring member sized to be placed on the spinner support surface 512 of the spinner table 51, and a circular elastic packing 79 serving as a sealing member is attached to its underside. The movement mechanism 72 for moving the annular portion 71 up and down is composed of an air cylinder or the like, and has an arm 80 extending horizontally from the upper ends of two rods 721 that extend vertically upward and are movable up and down. The annular portion 71 is supported at the tip of the arm 80 so as to be horizontally rotatable. Specifically, a gate-shaped support frame 81 is attached to the annular portion 71, and the longitudinal center of the horizontal portion of the support frame 81 is supported at the tip of the arm 80 via a universal joint 82. Therefore, the annular portion 71 can rotate around the universal joint 82 relative to the arm 80. The universal joint 82 is located at the center of the spinner support surface 511 of the spinner table 51. A rotary joint or the like may be used instead of the universal joint 82.

[0036] The water nozzle 52 and the abrasive nozzle 74 each have a vertical section 521, 741 that stands upright, a horizontal section 522, 742 that bends at a right angle from the top of the vertical section 521, 741 and extends horizontally, and a vertical section 523, 743 that bends at a right angle from the tip of the horizontal section 522, 742 and extends downward, with the end of each vertical section 523, 743 opening downward. The water nozzle 52 and the abrasive nozzle 74 can be rotated horizontally around the vertical section 521, 741 by a rotating mechanism 83 shown in FIG. 5. The rotating mechanism 83 constitutes the horizontal movement mechanism.

[0037] The ultrasonic horn 75 is attached to the tip of a support arm 85, which has a vertical section 851 that stands upright, a horizontal section 852 that bends at a right angle from the upper end of the vertical section 851 and extends horizontally, and a vertical section 853 that bends at a right angle downward from the tip of the horizontal section 852, with the ultrasonic horn 75 in the shape of a long, thin rectangular block attached to the lower end of the vertical section 853. The support arm 85 and the ultrasonic horn 75 can be moved up and down by an elevating mechanism 86 shown in Figure 7, and can be rotated horizontally around the vertical section 851 of the support arm 85 by a rotating mechanism 87.

[0038] 8, the length L of the ultrasonic horn 75 is set to be equal to or larger than the radius r and equal to or smaller than the diameter D of the wafer 100 (r≦L≦D). An ultrasonic oscillator (not shown) is connected to the ultrasonic horn 75.

[0039] The spinner table 51, water nozzle 52, abrasive nozzle 74, ultrasonic horn 75, etc. are housed inside a polygonal cylindrical case 88 that is open at the top, and a polygonal cylindrical cover 89 with a bottom is disposed inside the case 88 so that it can move up and down. A rectangular plate-shaped bracket 90 protrudes horizontally from part of the upper edge of the cover 89, and two rods 911 (see FIG. 10) extending vertically upward from an elevating mechanism 91 such as an air cylinder are connected to the bracket 90. Therefore, the cover 89 can be moved up and down by the elevating mechanism 91. In the state shown in FIG. 2, the cover 89 is at its lowest position and in an open state.

[0040] [Function of grinding equipment] Next, a method for grinding the wafer 100 using the grinding apparatus 1 configured as above and a method for forming a gettering layer on the back surface of the ground wafer 100 will be described.

[0041] In the grinding apparatus 1 according to this embodiment, the wafer 100 is ground and a gettering layer is formed through four steps, namely, a wafer holding step, a grinding step, a gettering layer forming step, and a cleaning step. Each step will be described below.

[0042] (holding process) The holding step is a step of suction-holding the wafer 100 on the holding surface 11 of the chuck table 10, and in this holding step, one wafer 100 is taken out of the cassette 101 by the carry-in / out robot 61 shown in Fig. 1 and placed on the alignment table 102. The alignment table 102 then aligns the wafer 100, and the aligned wafer 100 is transported to the chuck table 10 while being held by the first transport arm 62.

[0043] On the chuck table 10, the wafer 100 is placed on the chuck holding surface 11 with its back surface (the ground surface) facing up, and when a suction source (not shown), such as a vacuum pump, is driven from this state to suck out the air from within the porous member 12, a negative pressure is generated within the porous member 12, and the wafer 100 is attracted by this negative pressure and held by suction onto the chuck holding surface 11 of the chuck table 10.

[0044] (Grinding process) The grinding process is a process in which the wafer 100, which has been suction-held on the holding surface 11 of the chuck table 10 in the holding process, is ground by the grinding mechanism 30 shown in Figure 1. In this grinding process, the chuck table 10 and the wafer 100, which has been suction-held on it, are moved and positioned below the grinding wheel 35 of the grinding mechanism 30 by the horizontal movement mechanism 20 shown in Figure 1.

[0045] That is, when the electric motor 24 of the horizontal movement mechanism 20 is started and the ball screw shaft 23 rotates, the slider 21, to which a nut member (not shown) that screws onto the ball screw shaft 23 is attached, slides in the +Y-axis direction along the pair of left and right guide rails 22 together with the chuck table 10 and the like, so that the wafer 100 held on the holding surface 11 of the chuck table 10 is positioned below the grinding wheel 35 of the grinding mechanism 30. At this time, the horizontal positional relationship between the grinding stone 352 and the lower surface (machined surface) thereof is adjusted so that the lower surface (machined surface) of the grinding stone 352 passes through the center of the wafer 100.

[0046] 1 is driven to rotate the chuck table 10, and the wafer 100 held on the chuck holding surface 11 of the chuck table 10 is rotated at a predetermined rotational speed in the direction of the arrow in FIG. 1 (counterclockwise direction). At the same time, the spindle motor 32 of the grinding mechanism 30 is driven to rotate the grinding wheel 35 at a predetermined rotational speed in the direction of the arrow in FIG. 1 (counterclockwise direction).

[0047] As described above, while the wafer 100 and grinding wheel 35 are rotating, the vertical movement mechanism 40 is driven to lower the grinding wheel 35 in the −Z-axis direction. That is, when the electric motor 44 is driven to rotate the ball screw shaft 43, the lift plate 41, which is provided with a nut member (not shown) that threads onto the ball screw shaft 43, is lowered in the −Z-axis direction together with the spindle motor 32 and the grinding wheel 35. As a result, the lower surface (machining surface) of the grinding wheel 35 comes into contact with the upper surface (back surface) of the wafer 100. When the grinding wheel 35 is further lowered a predetermined amount in the −Z-axis direction from the state in which the lower surface of the grinding wheel 352 is in contact with the upper surface of the wafer 100, the upper surface (back surface) of the wafer 100 is ground by the grinding wheel 352 by a predetermined amount. The thickness of the wafer 100 during grinding is measured by the thickness gauge 26, and the measurement result is sent to a control unit (not shown).

[0048] (Gettering layer formation process) The gettering layer forming process is a process for forming a gettering layer on the back surface of the wafer 100 that has been ground in the preceding grinding process, and when forming this gettering layer, the wafer 100 that has been ground is held by the second transfer arm 63 shown in Fig. 1 and transferred from the chuck table 10 to the spinner table 51 of the spinner cleaning mechanism 50 while the annular part 71 of the gettering layer forming device 70 is waiting above the spinner table 51 as shown in Fig. 2. Then, the wafer 100 transferred to the spinner table 51 is suction-held on the spinner holding surface 511 of the spinner table 51.

[0049] When the moving mechanism 72 is driven from the above state to lower the two rods 721, the arms 80 extending horizontally from the upper ends of the rods 721 and the annular portions 71 supported at the tips of the arms 80 also lower, and as shown in FIG. 3, the annular portions 71 are placed on the placement surface 512 (see FIG. 2) formed on the outer periphery of the upper surface of the spinner table 51. When the annular portions 71 are placed on the placement surface 512 of the spinner table 51 in this manner, the annular portions 71 surround the wafers 100 held by suction on the spinner holding surface 511 of the spinner table 51, and a water tank 73 is formed between the annular portions 71 and the wafers 100. At this time, a high level of sealing is ensured between the annular portions 71 and the placement surface 512 of the spinner table 51 due to the sealing action of the elastic packing 79 attached to the underside of the annular portions 71. The bottom surface of the water tank 73 is formed by the wafers 100.

[0050] In the above state, the water nozzle 52, the abrasive nozzle 74, and the ultrasonic horn 75 are waiting at their standby positions (home positions) as shown in FIG.

[0051] As described above, when water tank 73 is formed on spinner table 51 by annular portion 71 and wafer 100, turning mechanism 83 shown in Fig. 5 is driven, and horizontal portions 522, 742 (see Fig. 2) of water nozzle 52 and abrasive nozzle 74, which are waiting in the waiting position as shown in Fig. 3, turn in the direction of the arrows in Fig. 4 around vertical portions 521, 741 (see Fig. 2), so that the openings of vertical portions 523, 743 (see Fig. 2) of water nozzle 52 and abrasive nozzle 74 are opened above water tank 73. In this state, when water is supplied from water nozzle 52 and free abrasive grains are supplied from abrasive nozzle 74 into water tank 73, water tank 73 is filled with water containing free abrasive grains, as shown in Fig. 5, and wafer 100 held on spinner holding surface 511 of spinner table 51 is submerged in the water in water tank 73.

[0052] Next, the pivoting mechanism 83 shown in Fig. 5 is driven again to pivot the water nozzle 52 and the abrasive nozzle 74 in the horizontal direction and retract them to the standby position as shown in Fig. 6, and the pivoting mechanism 87 shown in Fig. 7 is driven. Then, the horizontal part 852 of the support arm 85 supporting the ultrasonic horn 75 pivots horizontally around the vertical part 851 (see Fig. 2) in the direction of the arrow in Fig. 6, and the ultrasonic horn 75, which was waiting at the standby position shown by the dashed line in Fig. 6, moves above the wafer 100 as shown by the solid line in Fig. 6.

[0053] From the above state, the lifting mechanism 86 shown in Fig. 7 is driven to lower the support arm 85 and the ultrasonic horn 75 supported thereby, and the ultrasonic horn 75 is immersed in the water in the water tank 73 as shown in Fig. 7. At this time, the ultrasonic horn 75 extends from the center to the outer peripheral edge of the wafer 100 as shown in Fig. 8.

[0054] Next, while driving the rotation mechanism 76 shown in FIG. 6 to rotate the spinner table 51 and the wafer 100 held thereon by suction at a low speed in the direction of the arrow (counterclockwise) shown in FIG. 8, ultrasonic vibrations are propagated from the ultrasonic horn 75 to the free abrasive grains contained in the water in the water tank 73. The free abrasive grains then ultrasonically vibrate, creating countless fine scratches on the backside of the wafer 100, thereby forming a gettering layer on the backside of the wafer 100. In particular, in this embodiment, the free abrasive grains contained in shallow water are ultrasonically vibrated while always resting on the backside of the wafer 100, and the free abrasive grains moving laterally and diagonally create fine scratches that cross each other on the backside of the wafer 100, thereby efficiently forming a gettering layer in a short time for capturing and fixing impurities (such as heavy metal impurities) that cause metal contamination in the gettering sites.

[0055] 8, in this embodiment, the length L of the ultrasonic horn 75 is set to be equal to or greater than the radius r and equal to or less than the diameter D of the wafer 100 (r≦L≦D), so that when the spinner table 51 and the wafer 100 held thereon rotate in the direction of the arrow in Fig. 8, a gettering layer is formed uniformly over the entire back surface of the wafer 100. Note that although the present embodiment uses the ultrasonic horn 75 in the form of a long, narrow rectangular block, as shown in Fig. 9, a gettering layer can also be formed uniformly over the entire back surface of the wafer 100 by using a small, circular ultrasonic horn 75' and moving this ultrasonic horn 75' back and forth in the radial direction (the direction of the arrow in the figure) in the range from the center of the wafer 100 to the outer peripheral edge.

[0056] Once a gettering layer has been formed on the backside of wafer 100 through the above steps, lifting mechanism 86 shown in Fig. 7 is driven to lift ultrasonic horn 75 to a predetermined height, and rotating mechanism 87 is driven to horizontally rotate ultrasonic horn 75 and retract it to the standby position shown in Fig. 10. Also, moving mechanism 72 is driven to lift annular portion 71 and retract it to the standby position shown in Fig. 10. Furthermore, lifting mechanism 91 is driven to lift cover 89, and the periphery of spinner table 51 is covered with cover 89.

[0057] However, when the annular portion 71 is raised and removed from the support surface 512 (see Figure 2) of the spinner table 51 as described above, the loose abrasive grains flow down from the outer periphery of the spinner table 51 together with the water, and these loose abrasive grains that have flowed down are wasted.

[0058] Therefore, it is desirable to recover and reuse the loose abrasive grains that have fallen off the outer periphery of the spinner table 51, and an abrasive grain recovery system for this purpose is shown in FIG.

[0059] 11, an annular receiving member 92 is disposed below the spinner table 51, and an annular recovery groove 93 that opens upward is formed in this receiving member 92. A discharge hole 94 opens in part of the recovery groove 93 of this receiving member 92, and this discharge hole 94 and the abrasive grain nozzle 74 are connected by a recovery line 95. A pump 96 is connected to the recovery line 95.

[0060] In the abrasive grain recovery system configured as described above, when the formation of a gettering layer on the backside of the wafer 100 is completed and the annular portion 71 is lifted, the loose abrasive grains that flow down from the outer periphery of the spinner table 51 together with the water fall into the recovery groove 93 in the receiving member 92 and are recovered. The loose abrasive grains recovered together with the water by the recovery groove 93 are then returned by the pump 96 to the abrasive grain nozzle 74 via the recovery line 95 and are reused for forming a gettering layer on the backside of the wafer 100.

[0061] (Cleaning process) The cleaning process is a process for cleaning the back surface of wafer 100 on which a gettering layer has been formed in the previous gettering layer forming process. In this cleaning process, cover 89 is raised to cover the periphery of spinner table 51 as shown in FIG. 10, and the back surface of wafer 100 is cleaned by spinner cleaning mechanism 50.

[0062] That is, the rotation mechanism 83 shown in FIG. 5 is driven, and the cleaning nozzle (also used as a water nozzle) 52 and the abrasive nozzle 74, which had retreated to a standby position in the previous gettering layer formation process, rotate horizontally and move to a position where they open above the wafer 100 as shown in FIG. 10.

[0063] In the above state, cleaning liquid is sprayed from the cleaning nozzle 52 toward the back surface (upper surface) of the wafer 100, the back surface of the wafer 100 is cleaned with the cleaning liquid, and foreign matter such as loose abrasive grains and grinding debris adhering to the back surface of the wafer 100 is effectively removed.

[0064] Thereafter, the wafer 100 whose back surface has been cleaned is suction-held by the transfer robot 61 shown in FIG. 1 and transported from the spinner table 51 to the cassette 103, and is then stored in the cassette 103, thereby completing the series of grinding processes and the formation of the gettering layer on the wafer 100.

[0065] As described above, the gettering layer forming apparatus 70 according to the present invention and the grinding apparatus 1 equipped with the same have the effect of efficiently forming a gettering layer on the back surface of the ground wafer 100 in a short time.

[0066] In the above embodiment, the gettering layer forming device 70 is provided integrally with the spinner cleaning mechanism 50, but the gettering layer forming device 70 may be provided integrally with the grinding mechanism 30. In this case, the annular portion 71 is placed on the placement surface 13 (see FIG. 1) formed on the outer periphery of the chuck holding surface 11 of the chuck table 10, and a water tank 73 is formed between the annular portion 71 and the wafer 100.

[0067] Furthermore, although the above has described an embodiment in which the present invention is applied to a grinding apparatus and a gettering layer forming apparatus provided therein, the present invention also includes applications to any other processing apparatus, including polishing apparatuses other than grinding apparatuses, and gettering layer forming apparatuses provided therein.

[0068] Furthermore, the present invention is not limited to the application of the above-described embodiments, and it goes without saying that various modifications are possible within the scope of the claims and the technical ideas described in the specification and drawings. [Explanation of symbols]

[0069] 1: Grinding device (processing device), 2: Base, 3: Internal base, 4: Opening, 5: Cover, 6,7: Telescopic cover, 8: Column, 10: Chuck table, 11: chuck table holding surface, 12: porous member, 13: mounting surface, 14: Rotation mechanism, 20: Horizontal movement mechanism, 21: Slider, 22: Guide rail, 23: ball screw shaft, 24: electric motor, 25: bearing, 26: thickness measuring device, 30: grinding mechanism, 31: holder, 32: spindle motor, 33: spindle, 34: Mount, 35: Grinding wheel, 351: base, 352: grinding stone, 40: vertical movement mechanism, 41: lifting plate, 42: Guide rail, 43: Ball screw shaft, 44: Electric motor, 45: Bearing, 50: spinner cleaning mechanism, 51: spinner table, 511: spinner holding surface, 512: Mounting surface of spinner table, 52: Cleaning nozzle (water nozzle), 521, 523: Vertical part of cleaning nozzle (water nozzle), 522: Horizontal part of cleaning nozzle (water nozzle), 60: Transport mechanism, 61: Carry-in / out robot, 62: first transfer arm, 63: second transfer arm, 70: gettering layer forming device, 71: Circular ring portion, 72: Moving mechanism, 721: Rod of moving mechanism, 73: Water tank, 74: Abrasive nozzle (abrasive grain feeding part), 741, 743: Vertical part of the abrasive grain nozzle, 742: horizontal part of abrasive nozzle, 75, 75': ultrasonic horn, 76: rotation mechanism, 77: Rotating shaft, 78: Rotary joint, 79: Elastic packing, 80: Arm, 81: Support frame, 82: Universal joint, 83: Rotation mechanism (horizontal movement mechanism), 85: Support arm; 851, 853: Vertical portion of support arm; 852: horizontal part of support arm, 86: lifting mechanism, 87: swivel mechanism, 88: case, 89: Cover, 90: Bracket, 91: Lifting mechanism, 911: Rod, 92: receiving member, 93: recovery groove, 94: discharge hole, 95: recovery line, 96: pump, 100: wafer, 101: cassette, 102: alignment table, 103: Cassette, D: diameter of wafer, L: length of ultrasonic horn, r: radius of wafer

Claims

1. A gettering layer forming apparatus for forming a gettering layer on a back surface of a wafer, comprising: a holding table having a holding surface that suction-holds the front surface of the wafer and an annular mounting surface disposed radially outward of the holding surface; a circular ring portion that is placed on the placement surface and surrounds the wafer held on the holding surface to form a water tank; a moving mechanism for placing the annular portion on or separating it from the placement surface; an abrasive grain supply unit that supplies free abrasive grains to the water tank; a water nozzle for supplying water to the water tank to submerge the wafer; an ultrasonic horn that propagates ultrasonic vibrations to the loose abrasive grains; a horizontal movement mechanism that moves the ultrasonic horn and the holding table relatively in a direction parallel to the holding surface; and forming a gettering layer on the back surface of the wafer held on the holding surface and submerged in water by the free abrasive grains to which ultrasonic vibrations are propagated. Gettering layer forming device.

2. the ultrasonic horn extends from a radius of the wafer to a diameter of the wafer; a rotation mechanism that rotates the holding table around the center of the holding surface as an axis; 2. The gettering layer forming apparatus according to claim 1.

3. A processing device for processing the back surface of a wafer, a chuck table having a chuck holding surface that holds the front surface of the wafer and an annular mounting surface disposed radially outward of the chuck holding surface; a processing mechanism for processing the wafer held on the chuck table; a gettering layer forming device for forming a gettering layer on the back surface of the wafer; Equipped with The gettering layer forming apparatus comprises: a circular ring portion that is placed on the placement surface and surrounds the wafer held on the chuck holding surface to form a water tank; an abrasive grain supply unit that supplies free abrasive grains to the water tank; a water nozzle for supplying water to the water tank to submerge the wafer; an ultrasonic horn that propagates ultrasonic vibrations to the loose abrasive grains; a horizontal movement mechanism that moves the ultrasonic horn and the chuck table relatively in a direction parallel to the chuck holding surface; and forming a gettering layer on the back surface of the wafer held on the chuck holding surface and submerged in water by the free abrasive grains to which ultrasonic vibrations are propagated. Processing equipment.

4. A processing device for processing the back surface of a wafer, a chuck table that holds the front side of the wafer on a chuck holding surface; a processing mechanism for processing the back surface of the wafer held on the chuck holding surface; a spinner cleaning mechanism for cleaning the wafer; a transfer mechanism that transfers the wafer from the chuck table to the spinner cleaning mechanism; a gettering layer forming device for forming a gettering layer on the back surface of the wafer; Equipped with The spinner cleaning mechanism includes: a spinner table having a spinner holding surface that holds the front side of the wafer and an annular mounting surface disposed radially outward of the spinner holding surface; a cleaning nozzle for spraying a cleaning liquid onto the back surface of the wafer held on the spinner holding surface; a rotation mechanism that rotates the spinner table around an axis that is the center of the spinner holding surface; a gettering layer forming device for forming a gettering layer on the back surface of the wafer; Equipped with The gettering layer forming apparatus comprises: a circular ring portion that is placed on the placement surface and surrounds the wafer held on the spinner holding surface to form a water tank; an abrasive grain supply unit that supplies free abrasive grains to the water tank; an ultrasonic horn that propagates ultrasonic vibrations to the loose abrasive grains; Equipped with Water is supplied from the cleaning nozzle to the water tank to submerge the wafer held on the spinner holding surface, and the spinner table is rotated in this state; a gettering layer is formed on the back surface of the wafer held on the spinner holding surface and submerged in water by the free abrasive grains to which the ultrasonic vibration is propagated; Processing equipment.

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