Grinding device

Abstract

To achieve both of reduction of the number of dimples generated and productivity of a wafer.SOLUTION: A grinding device includes: a chuck table which suctions and holds a wafer; a grinding unit for grinding the wafer; a positioning unit having a positioning table; a transport arm which transports the wafer between the positioning table and the chuck table; a camera unit which captures images of one surface side of the wafer suctioned and held by the positioning table; a control unit including a contamination state determination unit which determines a contamination state of the one surface side on the basis of the images obtained by the camera unit; and a cleaning unit disposed below a moving path of the transport arm between the positioning table and the chuck table and having nozzles for supplying cleaning water to the one surface side of the wafer in a state that the other surface side of the wafer is held by the transport arm. The control unit may change wafer cleaning conditions in the cleaning unit according to the contamination state.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a grinding apparatus for grinding wafers, particularly silicon wafers cut from silicon ingots.

Background Art

[0002] In order to manufacture device chips such as ICs (Integrated Circuits), silicon wafers (hereinafter simply referred to as wafers) made of single crystal silicon are usually used. Wafers are manufactured by processing silicon ingots (hereinafter simply referred to as ingots) made of single crystal silicon.

[0003] For example, an ingot is cut into a thin plate shape with an inner peripheral blade type cutting machine or a multi-wire saw to cut out a wafer of a predetermined thickness (i.e., slicing). After slicing, the cut surface of the wafer is flattened by grinding or the like.

[0004] After slicing, silicon chips may adhere to the wafer. For example, if the front side of the wafer is sucked and held by a chuck table with chips remaining on the front side and the back side of the wafer is ground, local depressions (dimples) are formed on the back side after grinding. [[ID=2!]]

[0005] In order to suppress the generation of dimples, it is necessary to clean the front side of the wafer before sucking and holding the front side of the wafer by a chuck table. However, since the amount of adhered chips varies for each wafer, if a relatively long cleaning time corresponding to the maximum assumed amount of adhered chips is uniformly applied to each wafer for cleaning, the productivity of the wafers decreases.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

[0007] This invention has been made in view of the aforementioned problems, and aims to achieve both a reduction in the number of dimples and improved wafer productivity. [Means for solving the problem]

[0008] According to one aspect of the present invention, a grinding apparatus for grinding a wafer comprises a chuck table for suction holding the wafer, and a grinding unit having a spindle, the spindle of which a grinding wheel for grinding the wafer held by the chuck table is mounted, The wafer is placed such that the central part of one side is in contact with the surface and the outer edge protrudes outwards. A positioning unit having a positioning table for positioning the wafer in a predetermined position, a transport arm for transporting the wafer between the positioning table and the chuck table, and the wafer held by the positioning table by suction Applicable One side The annular region excluding the central part A grinding apparatus is provided, comprising: a camera unit having a camera for capturing images; a control unit having a processor and memory, and including a dirt state determination unit that determines the dirt state of one side based on the image obtained by the camera unit; and a cleaning unit positioned below the movement path of the transport arm between the positioning table and the chuck table, and having a nozzle that supplies cleaning water to the one side of the wafer while the other side of the wafer, which is opposite to the one side that is held by the chuck table, is held by the transport arm, wherein the control unit can change the cleaning conditions of the wafer in the cleaning unit according to the dirt state. In one embodiment of the present invention, the camera may be moved while the wafer, which is held by suction on the positioning table, is rotated above the camera unit, thereby capturing an image of the entire side of the wafer except for the central portion of that side. According to another embodiment of the present invention, a grinding apparatus for grinding a wafer comprises a chuck table for holding the wafer by suction, a grinding unit having a spindle and a grinding wheel for grinding the wafer held by the chuck table mounted on the spindle, a positioning unit having a positioning table for positioning the wafer at a predetermined position, a transport arm for transporting the wafer between the positioning table and the chuck table, a cassette placement area on which a cassette containing the wafer is placed, a transport robot having a hand portion for holding the wafer by suction, for transporting the wafer from the cassette and placing it on the positioning table, and the other side of the wafer being held by suction on the hand portion A grinding apparatus is provided, comprising: a camera unit having a camera for imaging one side of a wafer; a control unit having a processor and memory, and including a contamination determination unit for determining the contamination status of the one side based on the image obtained by the camera unit; and a cleaning unit positioned below the movement path of the transport arm between the positioning table and the chuck table, and having a nozzle for supplying cleaning water to the one side of the wafer while the other side of the wafer, opposite to the one side held by the chuck table, is held by the transport arm, wherein the control unit can change the cleaning conditions of the wafer in the cleaning unit according to the contamination status. In another embodiment of the present invention, the camera may be moved while the wafer, which is held by the hand, is rotated above the camera unit, so that the camera images the entire one side of the wafer. [Effects of the Invention]

[0009] In a grinding apparatus according to one aspect of the present invention, a control unit determines the degree of contamination on one side of the wafer based on an image captured by a camera, and then a cleaning unit cleans one side of the wafer while a transport arm holds the other side of the wafer.

[0010] The control unit can change the cleaning conditions of the wafer in the cleaning unit according to the degree of contamination. For example, the control unit can shorten the cleaning time for wafers with a relatively small amount of chips attached, and lengthen the cleaning time for wafers with a relatively large amount of chips attached.

[0011] Since the cleaning time can be shortened for wafers with a relatively small amount of chip adhesion, wafer productivity can be improved compared to applying the same cleaning time used for wafers with a relatively large amount of chip adhesion to each wafer.

[0012] In addition, cleaning one side of the wafer before grinding the other side reduces the number of dimples generated during grinding. Therefore, it is possible to achieve both a reduction in the number of dimples and increased wafer productivity. [Brief explanation of the drawing]

[0013] [Figure 1] This is a perspective view of the grinding machine. [Figure 2] This is a partial cross-sectional side view of a positioning unit, etc. [Figure 3] This is an enlarged perspective view of the first washing unit. [Figure 4] This is a partial cross-sectional side view showing how wafers are cleaned in the first cleaning unit. [Figure 5] This is a partial cross-sectional side view showing the process of grinding a wafer using a rough grinding unit. [Figure 6] This is a perspective view of a grinding apparatus according to a second embodiment. [Figure 7] This is a perspective view of a grinding apparatus according to a third embodiment. [Modes for carrying out the invention]

[0014] (First Embodiment) An embodiment according to an aspect of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a perspective view of a grinding apparatus 2. In FIG. 1, a part of the components is shown as functional blocks. In FIG. 1, the X-axis direction, the Y-axis direction (front-rear direction), and the Z-axis direction (vertical direction, grinding feed direction) are orthogonal to each other.

[0015] The grinding apparatus 2 has a rectangular parallelepiped base 4 that supports components. A recess 4a is formed on the front (one side in the Y-axis direction) side of the base 4, and a transfer robot 6 for transferring the wafer 11 is provided in this recess 4a.

[0016] The transfer robot 6 has a multi-link structure. A fork-shaped hand portion 6a called an end effector is provided at the tip of the uppermost stage of the multi-link. The hand portion 6a is arranged at an arbitrary position within a predetermined range.

[0017] The hand portion 6a can suck and hold the wafer 11 in a non-contact manner. A plurality of disk-shaped suction pads (not shown) are provided on the hand portion 6a. Each suction pad generates a negative pressure according to the so-called Bernoulli's law.

[0018] Such a suction pad is also called a Bernoulli chuck. A plurality of nozzles are formed in each suction pad, and by injecting air radially or cyclonically from the plurality of nozzles, a negative pressure is generated at the central portion in the radial direction of the suction pad.

[0019] When each suction pad of the hand portion 6a is arranged downward and a negative pressure is generated from each suction pad in a state where the hand portion 6a is close to the wafer 11, the wafer 11 is sucked by the hand portion 6a. The wafer 11 is sucked and held in a non-contact manner by the hand portion 6a by the balance between the upward force due to the negative pressure and the downward force due to the weight of the wafer 11 and the like.

[0020] Cassette mounting areas 8a and 8b are provided on both sides of the recess 4a in the X-axis direction. A cassette 10 containing one or more wafers 11 before grinding is placed in each of the cassette mounting areas 8a and 8b. The wafers 11 are formed of single-crystal silicon as described above.

[0021] The wafer 11 is formed, for example, by positioning the focal point of a laser beam at a predetermined depth in the ingot and moving the ingot relative to the focal point to form a region with weak mechanical strength (a so-called modified region), and then separating the ingot at the modified region. Alternatively, the wafer 11 may be formed by slicing the ingot with a wire saw.

[0022] The wafer 11 that is ground by the grinding apparatus 2 is the wafer after it has been separated from the ingot and before it has been ground. The grinding surface of the wafer 11 (in this embodiment, the other surface 11b) corresponds to the region where the modified region has been formed and the region where slicing has been performed.

[0023] The wafer 11 has one surface 11a and another surface 11b located opposite to surface 11a. The distance from surface 11a to surface 11b (i.e., the thickness of wafer 11) is, for example, 250 μm to 800 μm, and the diameter of wafer 11 is, for example, 2 inches (approximately 50 mm) to 12 inches (approximately 300 mm).

[0024] Of course, no devices such as ICs (Integrated Circuits), MEMS (Micro Electro Mechanical Systems), or circuits such as TEGs (Test Element Groups) are formed on one side 11a and the other side 11b of the wafer 11.

[0025] Behind the cassette mounting area 8a (on the other side in the Y-axis direction), a positioning unit 12 is provided for positioning the wafer 11, which has been unloaded by the transport robot 6, into a predetermined position. Figure 2 is a partial cross-sectional side view of the positioning unit 12 and the like.

[0026] As shown in Figure 2, the positioning unit 12 has a disc-shaped positioning table 12a on which the wafer 11 is placed. The positioning table 12a has a smaller diameter than the outer diameter of the grinding chuck table 22, which will be described later.

[0027] Furthermore, since the diameter of the positioning table 12a is smaller than the diameter of the wafer 11, when the wafer 11 is placed on the positioning table 12a, the outer edge of the wafer 11 protrudes beyond the positioning table 12a.

[0028] On the surface side of the positioning table 12a, a cross-shaped groove passing through the center of the surface and a plurality of annular grooves arranged concentrically around the center are formed. The cross-shaped groove and the plurality of annular grooves intersect and connect with each other, and are connected to the suction passage 12b formed in the positioning table 12a.

[0029] One end of the suction passage 12b is connected to the center of the cross-shaped groove, and the other end of the suction passage 12b is connected to a suction source 14, such as a vacuum pump, via a pipe or the like. When the suction source 14 is operated, negative pressure is transmitted to the groove on the surface side of the positioning table 12a.

[0030] A cylindrical rotating shaft 12c is connected to the underside of the positioning table 12a. The longitudinal direction of the rotating shaft 12c is aligned with the Z-axis direction. The rotating shaft 12c is directly or indirectly connected to a rotational drive source (not shown), such as a motor.

[0031] When the rotation drive source is activated, the positioning table 12a rotates around the rotation axis 12c. The positioning table 12a can rotate in either direction. Multiple positioning pins 12d are provided around the positioning table 12a at approximately equal intervals along the circumferential direction of the positioning table 12a.

[0032] Each positioning pin 12d is movable by the same distance along the radial direction of the positioning table 12a. In order to position the wafer 11 at a predetermined position in the XY plane, first the wafer 11 is placed on the positioning table 12a.

[0033] In this embodiment, the wafer 11 is placed on the positioning table 12a such that one side 11a of the wafer 11 is in contact with the positioning table 12a and the other side 11b is exposed upwards. When the wafer 11 is placed on the table, it is not held in place by suction on the positioning table 12a.

[0034] In this state, the position of the wafer 11 is adjusted to a predetermined position in the XY plane by the multiple positioning pins 12d gripping the wafer 11 in the radial direction of the positioning table 12a. For example, the position of the wafer 11 is adjusted so that the center of one surface 11a coincides with the center of the upper surface of the positioning table 12a in the XY plane.

[0035] After position adjustment, the wafer 11 is held in place by the positioning table 12a using negative pressure, and then one side 11a of the wafer 11 (i.e., the side to be sucked by the chuck table 22, which will be described later) is imaged by the camera unit 16. The camera unit 16 is equipped with a camera 16a positioned facing upwards near the positioning table 12a.

[0036] Camera 16a has a light source (not shown) that emits light in the visible light band. The light source emits light upward to illuminate a predetermined area of ​​one surface 11a of the wafer 11 which is held by attraction on the positioning table 12a.

[0037] Light reflected from surface 11a is received by an image sensor via an objective lens (not shown) whose optical axis is aligned along the Z-axis. The image sensor is, for example, a CMOS (Complementary Metal-Oxide-Semiconductor) image sensor or a CCD (Charge-Coupled Device) image sensor.

[0038] A moving mechanism (not shown) is provided at the bottom of the camera 16a to move the camera 16a linearly along the radial direction of the positioning table 12a. The camera 16a can move both towards the rotation axis 12c and away from the rotation axis 12c. The moving mechanism is, for example, a ball screw type, but other types may also be used.

[0039] When imaging one side 11a with camera 16a, the positioning table 12a is rotated in a predetermined direction around the rotation axis 12c, and the camera 16a is moved linearly by the moving mechanism (for example, in a direction approaching the rotation axis 12c) while imaging one side 11a.

[0040] This allows imaging of the entire surface 11a, excluding the central part of surface 11a (i.e., the area to be aspirationed). The obtained image is used by the control unit 62 of the grinding device 2, described later, to determine the degree of contamination on surface 11a.

[0041] The base end of the loading arm (transport arm) 18 is provided in the region adjacent to the positioning unit 12 in one direction in the X-axis direction (see Figures 1 and 4). As shown in Figure 4, the loading arm 18 has an arm portion 18a.

[0042] A disc-shaped suction portion 18b is provided on the lower surface of the tip of the arm portion 18a. The suction portion 18b has a frame and a porous plate fixed in a recess of the frame, and the lower surface of the suction portion 18b functions as a holding surface 18b1 that sucks and holds the wafer 11 while in contact with the wafer 11.

[0043] The cylindrical portion 18c located at the base end of the arm portion 18a is rotatable within a predetermined angular range around the rotation axis 18c1. Furthermore, the cylindrical portion 18c is movable up and down along the Z-axis direction by an actuator.

[0044] As will be described later, the loading arm 18 of this embodiment requires precise adjustment of the height position of the suction section 18b. For this reason, an electric cylinder is used as the actuator. The electric cylinder has a motor, and by converting the rotation of the shaft by the motor into linear motion, the height position of the cylindrical section 18c can be precisely adjusted.

[0045] Returning to Figure 1, a disc-shaped turntable 20 is provided behind the base end of the loading arm 18. A rotational drive source (not shown), such as a motor, for rotating the turntable 20 is located on the underside of the turntable 20.

[0046] The upper surface of the turntable 20 is divided into three fan-shaped regions by multiple linear partition plates arranged radially. The central angle of each fan-shaped region is approximately 120 degrees. The fan-shaped region closest to the loading arm 18 is the loading / unloading region A, where the wafer 11 is loaded into or unloaded from the turntable 20.

[0047] The fan-shaped region located approximately 120 degrees clockwise from the loading / unloading area A in a top view becomes the rough grinding area B where the wafer 11 undergoes rough grinding. The fan-shaped region located approximately 120 degrees counterclockwise from the loading / unloading area A in a top view becomes the finish grinding area C where the wafer 11 undergoes finish grinding.

[0048] Each of the loading / unloading area A, rough grinding area B, and finish grinding area C is provided with one chuck table 22. Each chuck table 22 is selectively positioned in one of the loading / unloading area A, rough grinding area B, or finish grinding area C by the rotation of the turntable 20.

[0049] The chuck table 22 has a disc-shaped frame made of non-porous ceramics. A disc-shaped recess is formed on the upper surface of the frame, and a disc-shaped porous plate made of porous ceramics is fixed in this recess.

[0050] Negative pressure is transmitted to the porous plate from the suction source 14 (see Figure 2) through predetermined channels formed in the frame. The upper surfaces of the frame and the porous plate function as holding surfaces 22a (see Figure 5) that suction and hold the wafer 11.

[0051] When the loading arm 18 transports the wafer 11 from the positioning table 12a to the chuck table 22 located in the loading / unloading area A, the wafer 11 is held in place by suction on the holding surface 22a.

[0052] Each chuck table 22 is connected linearly or indirectly to a rotational drive source (not shown), such as a motor, and each chuck table 22 is rotatable around a predetermined rotation axis 22b (see Figure 5).

[0053] Below the movement path 18d (see Figure 1) of the suction unit 18b between the positioning table 12a and the chuck table 22 located in the loading / unloading area A, a first cleaning unit (cleaning unit) 24 is provided for cleaning one side 11a of the wafer 11. The movement path 18d is determined, for example, by the movement trajectory of the radial center position of the suction unit 18b.

[0054] Figure 3 is an enlarged perspective view of the first cleaning unit 24. The first cleaning unit 24 of this embodiment has three cleaning bar sections 26-1, 26-2, and 26-3. The three cleaning bar sections 26-1, 26-2, and 26-3 are connected to each other at their base ends and are arranged radially in the XY plane.

[0055] The angles formed by two adjacent cleaning bars 26-1, 26-2, and 26-3 are approximately 120 degrees each. The cleaning bar 26 has a rectangular parallelepiped base 26a made of metal, resin, or the like. A foamed resin body 26b, which is approximately the same shape as the base 26a, is fixed to the upper surface of the base 26a so as to cover the upper surface of the base 26a.

[0056] The foamed resin body 26b is, for example, a PVA sponge formed from polyvinyl alcohol (hereinafter abbreviated as PVA), and has higher flexibility, water absorption, and water retention compared to a general sponge made of foamed polyurethane.

[0057] One nozzle unit 28 is provided on one side of the base portion 26a, protruding from that side. The nozzle unit 28 has a cylindrical housing 28a. The housing 28a protruding from the side of the base portion 26a of the cleaning bar portion 26-1 is positioned along the longitudinal direction of the base portion 26a of the cleaning bar portion 26-2.

[0058] Similarly, another housing 28a protruding from the side of the base portion 26a of the cleaning bar portion 26-2 is positioned along the longitudinal direction of the base portion 26a of the cleaning bar portion 26-3, and yet another housing 28a protruding from the side of the base portion 26a of the cleaning bar portion 26-3 is positioned along the longitudinal direction of the base portion 26a of the cleaning bar portion 26-1.

[0059] Multiple nozzles 28b are arranged at approximately equal intervals along the longitudinal direction of each housing 28a on the upper surface side of the housing 28a. In this embodiment, the nozzles 28b are openings provided in the housing 28a, but the nozzles 28b may have a cylindrical or conical shape that protrudes along the Z-axis direction.

[0060] The upper end of the rotating shaft 30 is connected to the lower surface of the base end of the three cleaning bar sections 26-1, 26-2, and 26-3 (see Figure 4). In Figure 4, the rotating shaft 30 is shown as a dashed line. The rotating shaft 30 is driven to rotate directly or indirectly by a rotational drive source such as a motor.

[0061] Figure 4 is a partial cross-sectional side view showing the cleaning of the wafer 11 by the first cleaning unit 24. In this embodiment, when the loading arm 18 transports the wafer 11 between the positioning table 12a and the chuck table 22 located in the loading / unloading area A, the first cleaning unit 24 cleans one side 11a (i.e., the bottom surface) of the wafer 11.

[0062] Specifically, the loading arm 18, while holding the other side 11b of the wafer 11 located on the positioning table 12a with the suction unit 18b, raises the cylindrical part 18c and rotates the arm part 18a by a predetermined angle to position the wafer 11 above the first cleaning unit 24.

[0063] Then, the first cleaning unit 24 is rotated around the rotating shaft 30 at a predetermined rotational speed, and cleaning water 28c such as pure water is sprayed (supplied) from each nozzle 28b at a predetermined flow rate, while the cylindrical part 18c is lowered to press the wafer 11 into the foamed resin body 26b.

[0064] This cleans one side 11a of the wafer 11, so that the side 11a that is held by the chuck table 22 can be cleaned. In one example, the rotation speed of the rotating shaft 30 is 60 rpm, and the predetermined flow rate is 1.0 L / min in total for all nozzles 28b.

[0065] Returning to Figure 1, behind the turntable 20, rectangular prism-shaped support structures 32a and 32b are provided, protruding from the upper surface of the base 4. A grinding feed unit 34 is provided on the front side of the support structures 32a and 32b.

[0066] The grinding feed unit 34 has a pair of Z-axis guide rails 36 that are substantially parallel to the Z-axis direction and fixed to the front surfaces of the support structures 32a and 32b. A Z-axis moving plate 38 is slidably attached to the pair of Z-axis guide rails 36.

[0067] A nut portion (not shown) is provided on the rear (back) side of the Z-axis moving plate 38. A screw shaft 40, which is provided along the Z-axis direction between a pair of Z-axis guide rails 36, is rotatably connected to the nut portion via a plurality of balls (not shown).

[0068] A motor 42, such as a stepping motor, is connected to the upper end of the screw shaft 40. When the motor 42 rotates the screw shaft 40, the Z-axis moving plate 38 moves in the Z-axis direction along the Z-axis guide rail 36.

[0069] A rough grinding unit (grinding unit) 44a is provided on the front surface of the Z-axis moving plate 38, which is located in front of the support structure 32a. The rough grinding unit 44a has a cylindrical spindle housing 46 fixed to the Z-axis moving plate 38.

[0070] The spindle housing 46 is positioned so that its cylindrical height is approximately parallel to the Z-axis direction. A portion of a cylindrical spindle 48 (see Figure 5) is rotatably housed within the spindle housing 46. A rotational drive source (not shown), such as a motor, is provided near the upper end of the spindle 48.

[0071] The upper surface of a disc-shaped wheel mount 50 is fixed to the lower end of the spindle 48. An annular rough grinding wheel (grinding wheel) 52a is mounted on the lower surface of the wheel mount 50 of the rough grinding unit 44a. In this way, the rough grinding wheel 52a is mounted to the spindle 48 via the wheel mount 50.

[0072] As shown in Figure 5, the rough grinding wheel 52a has an annular wheel base 52a1 made of a metal material such as an aluminum alloy. The upper side of the wheel base 52a1 is attached to the lower side of the wheel mount 50 using bolts (not shown) or the like.

[0073] Multiple block-shaped rough grinding wheels 52a2 are fixed to the underside of the wheel base 52a1. The multiple rough grinding wheels 52a2 are arranged in a ring shape at approximately equal intervals along the circumferential direction of the wheel base 52a1.

[0074] The annular grinding surface defined by the trajectory of the lower surface of the coarse grinding wheel 52a2 is approximately parallel to the XY plane. The coarse grinding wheel 52a2 contains abrasive grains such as diamond and cBN (cubic boron nitride), and a binder such as ceramics or resin for fixing the abrasive grains.

[0075] Directly below the rough grinding wheel 52a, a grinding water supply nozzle (not shown) is provided to supply grinding water such as pure water to the contact area (working area) between the wafer 11 and the rough grinding wheel 52a2.

[0076] During rough grinding, grinding water is supplied to the area to be ground from the grinding water supply nozzle. Alternatively, instead of the grinding water supply nozzle, an opening (not shown) may be formed in the wheel base 52a1, and grinding water may be supplied to the area to be ground from this opening.

[0077] The wafer 11, held by suction on the chuck table 22 located in the rough grinding area B, is roughly ground by the rough grinding wheel 52a. During rough grinding, the thickness of the wafer 11 is measured with the thickness measuring instrument 54 while grinding the other side 11b.

[0078] Figure 5 is a partial cross-sectional side view showing the grinding of the other surface 11b of the wafer 11 by the rough grinding unit 44a. The chuck table 22 protrudes slightly (for example, 10 μm to 20 μm) in the center compared to its outer periphery.

[0079] The rotating axis 22b is slightly tilted with respect to the Z-axis direction, and a portion of the holding surface 22a is parallel to the grinding surface. By adjusting the positions of the chuck table 22 and the rough grinding wheel 52a so that the grinding surface passes over the center of the holding surface 22a, the other side 11b is uniformly rough-ground.

[0080] Returning to Figure 1, a grinding feed unit 34 is also provided on the front side of the support structure 32b. A finish grinding unit (grinding unit) 44b is provided on the front of the Z-axis moving plate 38 of the grinding feed unit 34 provided on the support structure 32b.

[0081] The finishing grinding unit 44b also has a cylindrical spindle housing 46 fixed to the Z-axis moving plate 38. A portion of a cylindrical spindle 48 (see Figure 5) is rotatably housed within the spindle housing 46 of the finishing grinding unit 44b.

[0082] A rotational drive source (not shown), such as a motor, is provided near the upper end of the spindle 48, and a wheel mount 50 is fixed to the lower end of the spindle 48. An annular finishing grinding wheel (grinding wheel) 52b is mounted on the spindle 48 of the finishing grinding unit 44b via the wheel mount 50.

[0083] The finishing grinding wheel 52b has an annular wheel base made of a metal material such as an aluminum alloy. Multiple block-shaped finishing grinding wheels are fixed to the lower surface of the wheel base.

[0084] Multiple finishing grinding wheels are arranged in a ring shape at approximately equal intervals along the circumferential direction of the wheel base. Each finishing grinding wheel contains abrasive grains such as diamond or cBN (cubic boron nitride), and a binder such as ceramics or resin to fix the abrasive grains in place.

[0085] However, the average particle size of the abrasive grains on the finishing grinding wheel is smaller than that of the abrasive grains on the coarse grinding wheel 52a2. A grinding water supply nozzle (not shown) is provided directly below the finishing grinding wheel 52b to supply grinding water such as pure water to the area to be ground.

[0086] Alternatively, instead of a grinding water supply nozzle, an opening (not shown) may be formed in the wheel base, and grinding water may be supplied to the grinding area from this opening. The wafer 11, held by suction on the chuck table 22 located in the finish grinding area C, is then finish-ground on the finish grinding wheel 52b.

[0087] During the finish grinding process, the thickness of the wafer 11 is measured using the thickness measuring instrument 54 while grinding the other side 11b. The finished wafer 11 is returned to the loading / unloading area A. Then, it is unloaded from the chuck table 22 by the unloading arm 56.

[0088] Before loading the wafer 11 into the spinner cleaning apparatus 60, one side 11a (i.e., the bottom side) of the wafer 11 is cleaned again in a second cleaning unit 58, which has substantially the same structure as the first cleaning unit 24. The structure and usage method of the second cleaning unit 58 are substantially the same as those of the first cleaning unit 24, so a detailed explanation is omitted.

[0089] The second cleaning unit 58 is rotated at a predetermined speed while spraying cleaning water 28c from its nozzle, and the wafer 11 is pushed into the second cleaning unit 58 by the unloading arm 56, thereby cleaning the wafer 11.

[0090] By cleaning one side 11a of the wafer 11 again in the second cleaning unit 58, contamination of the spinner table of the spinner cleaning device 60 can be reduced. After the side 11a of the wafer 11 has been cleaned, the other side 11b (top side) of the wafer 11 is cleaned in the spinner cleaning device 60.

[0091] Specifically, the other side 11b is cleaned using a chemical solution, pure water, etc., and then dried. The wafer 11 cleaned by the spinner cleaning device 60 is returned to the cassette 10 from which it was shipped by the transport robot 6.

[0092] Each component of the grinding apparatus 2 is controlled by the control unit 62. The control unit 62 is composed of a computer that includes a processor (processing unit), such as a CPU (Central Processing Unit), and memory (storage device). The storage device includes a main memory such as DRAM (Dynamic Random Access Memory) and an auxiliary storage device such as flash memory.

[0093] The auxiliary storage device stores software, and the functions of the control unit 62 are realized by operating the processing unit and other components according to this software. The auxiliary storage device also stores a predetermined program for determining the contamination status of the wafer 11.

[0094] By loading and executing a predetermined program in the processor, the program functions as a contamination determination unit 64. The contamination determination unit 64 determines the contamination status of one side 11a of the wafer 11 based on the image obtained by the camera unit 16.

[0095] The dirt condition determination unit 64, for example, binarizes the obtained image, considering the white areas as areas without dirt and the black areas as areas with dirt. Then, it determines the dirt condition according to the area of ​​the black areas.

[0096] For example, in an annular region excluding the central part of one surface 11a, if the area of ​​the black region is 1% or less, the contamination level is considered to be level 1, and if the area of ​​the black region in the same annular region is more than 1% but 5% or less, the contamination level is considered to be level 2.

[0097] Furthermore, if the area of ​​the black region in the same annular region is more than 5% but 10% or less, the contamination level is considered to be level 3, and if the area of ​​the black region in the same annular region is more than 10% but 20% or less, the contamination level is considered to be level 4.

[0098] Furthermore, if the area of ​​the black region within the same ring-shaped region is between 20% and 30%, the contamination level is classified as level 5. In this way, a step-by-step level is determined according to the contamination level.

[0099] Furthermore, since the central portion of the surface 11a, which is held in place by the positioning table 12a, cannot be imaged by the camera 16a, the control unit 62 determines the level based on the image of the annular region excluding the central portion. In other words, the contamination status of the entire surface 11a is estimated from the image of the annular region.

[0100] The control unit 62 then changes the cleaning conditions for the wafer 11 in the first cleaning unit 24 according to the level of contamination. For example, using the cleaning time for the lowest level (i.e., level 1) as a baseline, the cleaning time is increased as the contamination level increases.

[0101] In this manner, the control unit 62 of this embodiment can shorten the cleaning time for wafers 11 with relatively little chip adhesion by changing the cleaning conditions of the wafer 11 in the first cleaning unit 24 according to the degree of contamination of the wafer 11.

[0102] Therefore, compared to cleaning each wafer 11 by uniformly applying the cleaning time that is used when cleaning wafers 11 with a relatively large amount of chip adhesion, the productivity of wafers 11 can be improved. In addition, by cleaning one side 11a of the wafer 11 before grinding, the number of dimples generated during grinding can be reduced.

[0103] In addition, instead of the cleaning time, or along with the cleaning time, one or both of the following may be changed: (1) the amount the wafer 11 is pushed into the first cleaning unit 24 by the loading arm 18, and (2) the water pressure of the cleaning water 28c sprayed from the nozzle 28b.

[0104] For example, using the indentation amount and water pressure for level 1 as a baseline, the indentation amount and water pressure are increased as the level increases. This makes it possible to clean wafers 11 with contamination levels 2 to 5 in the same short cleaning time as for level 1.

[0105] (Second Embodiment) Next, a second embodiment will be described with reference to Figure 6. Figure 6 is a perspective view of a grinding apparatus 72 according to the second embodiment. In the grinding apparatus 72, the camera unit 16 is provided between the recess 4a and the positioning unit 12, rather than between the positioning table 12a and the plurality of positioning pins 12d arranged in an annular shape.

[0106] In the second embodiment, the hand unit 6a holds the other side 11b of the wafer 11 by suction, and the transport robot 6 places the wafer 11 on the camera unit 16. Then, the camera 16a acquires an image of the one side 11a.

[0107] By appropriately combining the movement of the camera 16a and the movement of the hand unit 6a, an image of the entire side of one surface 11a is acquired by the camera 16a. In the second embodiment, since one surface 11a is exposed downwards, the entire side of one surface 11a can be imaged. Therefore, the contamination state of the wafer 11 can be determined more accurately than in the first embodiment.

[0108] In the second embodiment, the hand portion 6a may be provided with a plurality of suction pads that eject air in a cyclonic manner, so as to rotate the wafer 11 in a predetermined direction (clockwise or counterclockwise) by the swirling flow of air when suctioning and holding the wafer 11.

[0109] Suction pads that eject air in a cyclonic manner include those that eject air clockwise and those that eject air counterclockwise. One surface of the fork-shaped hand portion 6a has a shape that is symmetrical with respect to the axis of symmetry.

[0110] By arranging multiple suction pads, each spraying air in a predetermined direction, symmetrically on the hand portion 6a with respect to the axis of symmetry, the wafer 11 can be held and rotated at the same time.

[0111] In this case, by rotating the wafer 11, which is held in place by the hand unit 6a, at a predetermined speed above the camera unit 16, and moving the camera 16a along a predetermined direction, the entire surface 11a can be imaged.

[0112] Furthermore, if multiple suction pads are arranged to spray air in a predetermined direction (for example, clockwise) for the rotation of the wafer 11, the same number of suction pads may also be provided to spray air in the opposite direction (for example, counterclockwise) to hold the wafer 11 without rotating it.

[0113] In this embodiment, when the wafer 11 is rotated, multiple suction pads that spray air in a predetermined direction (for example, clockwise) are activated, but multiple suction pads that spray air in the opposite direction (for example, counterclockwise) are not activated. Also, when the wafer 11 is not rotated, all suction pads are activated.

[0114] (Third Embodiment) Next, a third embodiment will be described with reference to Figure 7. Figure 7 is a perspective view of the grinding apparatus 82 according to the third embodiment. In the grinding apparatus 2 according to the first embodiment, an additional camera unit 84 for observing one surface 11a after cleaning is provided between the positioning unit 12 and the first cleaning unit 24.

[0115] The additional camera unit 84 is located directly below the movement path 18d. The additional camera unit 84 includes a camera 84a and a movement mechanism (not shown) for moving the camera 84a linearly in a predetermined direction.

[0116] In the third embodiment, after the first cleaning unit 24 cleans one side 11a, the loading arm 18 returns the wafer 11 to the positioning unit 12 and positions the wafer 11 above the additional camera unit 84.

[0117] Then, the cleaned surface 11a is imaged by an additional camera unit 84, and the control unit 62 uses the dirt condition determination unit 64 to confirm whether the surface 11a has been properly cleaned. Specifically, as described above, whether or not it has been properly cleaned is determined based on the area of ​​the black region.

[0118] If the control unit 62 determines that the cleaning in the first cleaning unit 24 is insufficient, it will either perform cleaning again in the first cleaning unit 24, or notify the operator that the cleaning result is abnormal through a speaker, lamp, monitor, etc. (not shown) provided in the grinding device 82.

[0119] This prevents insufficiently cleaned wafers 11 from being held by the chuck table 22, and also allows for the detection of abnormalities in the loading arm 18, camera unit 16, first cleaning unit 24, etc., in advance.

[0120] Furthermore, the structures, methods, etc., of the embodiments described above can be modified as appropriate without departing from the scope of the present invention. For example, the additional camera unit 84 described in the third embodiment may be applied to the grinding apparatus 72 of the second embodiment.

[0121] By the way, the configuration of the positioning unit 12 is not limited to the configuration described above. The positioning unit 12 does not have to have multiple positioning pins 12d. In this case, the center of the wafer 11 is positioned directly below the movement path 18d using a camera unit (for example, the camera unit 16 described above).

[0122] Specifically, when the wafer 11 is transported from the loading arm 18 to the positioning table 12a, the center of one side 11a (or the other side 11b) of the wafer 11 is first calculated through the cooperation of the positioning table 12a and the camera unit.

[0123] For example, with the wafer 11 stationary, the outer periphery of one surface 11a of the wafer 11 is imaged, and the coordinates of two points on the outer edge of the surface 11a are identified. Then, after rotating the positioning table 12a by a predetermined angle of less than 360 degrees, the coordinates of two different points on the outer edge are further identified.

[0124] For example, the unknown center (X0,Y0) on one surface 11a is calculated as the coordinates of the intersection of the perpendicular bisector of the line segment connecting the coordinates (a,b) and (c,d) of two points on the outer edge before rotation, and the perpendicular bisector of the line segment connecting the coordinates (e,f) and (g,h) of two points on the outer edge after rotation.

[0125] After identifying the coordinates of the center of one surface 11a, the positioning table 12a is rotated so that the center of this surface 11a is located on the movement path 18d. This allows the loading arm 18 to hold the wafer 11 by suction with the other surface 11b aligned with the center of the suction unit 18b when holding the other surface 11b of the wafer 11.

[0126] Note that the method for calculating the center (X0,Y0) is not limited to the method described above. Instead of the camera unit 16, another camera capable of imaging the other surface 11b from above may be used.

[0127] Incidentally, in the first cleaning unit 24, a brush (not shown) made of a resin such as PVA may be fixed to the upper surface of the base portion 26a instead of the foamed resin body 26b. Alternatively, the foamed resin body 26b and the brush may be omitted, and one surface 11a may be cleaned using only the cleaning water 28c sprayed from the nozzle unit 28. [Explanation of Symbols]

[0128] 2, 72, 82: Grinding device, 4: Base, 4a: Recess, 6: Transfer robot, 6a: Hand unit 8a, 8b: Cassette mounting area, 10: Cassette 11: Wafer, 11a: One side, 11b: Other side 12: Positioning unit, 12a: Positioning table 12b: Suction path, 12c: Rotation axis, 12d: Positioning pin, 14: Suction source 16: Camera unit, 16a: Camera 18: Loading arm (transport arm), 18a: Arm section, 18b: Suction section 18b1: Holding surface, 18c: Cylindrical part, 18c1: Rotation axis, 18d: Movement path 20: Turntable, 22: Chuck table, 22a: Holding surface, 22b: Rotating shaft 24: First washing unit (washing unit) 26, 26-1, 26-2, 26-3: Cleaning bar section 26a: Base part, 26b: Foamed resin body 28: Nozzle unit, 28a: Housing, 28b: Nozzle, 28c: Cleaning water, 30: Rotating shaft 32a, 32b: Support structure, 34: Grinding feed unit, 36: Z-axis guide rail 38: Z-axis moving plate, 40: Screw shaft, 42: Motor 44a: Rough grinding unit (grinding unit) 44b: Finishing grinding unit (grinding unit) 46: Spindle housing, 48: Spindle, 50: Wheel mount 52a: Coarse grinding wheel, 52a1: Wheel base, 52a2: Coarse grinding wheel 52b: Finishing grinding wheel, 54: Thickness measuring instrument, 56: Unloading arm 58: Second cleaning unit, 60: Spinner cleaning device 62: Control unit, 64: State determination unit 84: Additional camera unit, 84a: Camera A: Loading / unloading area, B: Rough grinding area, C: Finishing grinding area

Claims

1. A grinding apparatus for grinding wafers, A chuck table for holding the wafer by suction, A grinding unit having a spindle, with a grinding wheel mounted on the spindle for grinding the wafer held in the chuck table, A positioning unit for positioning the wafer in a predetermined position has a positioning table on which the wafer is placed such that the central part of one side of the table is in contact with the table and the outer periphery extends outward, A transport arm for transporting the wafer between the positioning table and the chuck table, A camera unit having a camera that images an annular region of the wafer, excluding the central part on one side, which is held by suction on the positioning table, A control unit having a processor and memory, and including a dirt condition determination unit that determines the dirt condition of one side based on the image obtained by the camera unit, A cleaning unit having a nozzle that supplies cleaning water to one side of a wafer, while the other side of the wafer, which is opposite to the side of the wafer that is held by the chuck table, is held by the transport arm, is positioned below the movement path of the transport arm between the positioning table and the chuck table. Equipped with, The grinding apparatus is characterized in that the control unit can change the cleaning conditions of the wafer in the cleaning unit according to the degree of contamination.

2. The grinding apparatus according to claim 1, wherein the camera is moved while the wafer, which is held by suction on the positioning table, is rotated above the camera unit, so that the camera images the entire surface of the wafer, excluding the central part of that surface.

3. A grinding apparatus for grinding wafers, A chuck table for holding the wafer by suction, A grinding unit having a spindle, with a grinding wheel mounted on the spindle for grinding the wafer held in the chuck table, A positioning unit having a positioning table for positioning the wafer in a predetermined position, A transport arm for transporting the wafer between the positioning table and the chuck table, A cassette mounting area on which a cassette containing the wafer is placed, A transport robot having a hand section for suction and holding the wafer, which removes the wafer from the cassette and places it on the positioning table, A camera unit having a camera that images one side of the wafer, which is held in suction by the hand portion, A control unit having a processor and memory, and including a dirt condition determination unit that determines the dirt condition of one side based on the image obtained by the camera unit, A cleaning unit having a nozzle that supplies cleaning water to one side of a wafer while the other side of the wafer, which is opposite to the side of the wafer that is held by the chuck table, is held by the transport arm, is positioned below the movement path of the transport arm between the positioning table and the chuck table, and the other side of the wafer is held by the transport arm, Equipped with, The grinding apparatus is characterized in that the control unit can change the cleaning conditions of the wafer in the cleaning unit according to the degree of contamination.

4. The grinding apparatus according to claim 3, wherein the camera is moved while the wafer, which is held in suction by the hand unit, is rotated above the camera unit, so that the camera images the entire surface of one side of the wafer.

Images