JP2008264913A - Grinding device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To heighten production efficiency by reducing labors required for measuring thickness in a step for grinding a wafer while grasping a wafer thickness in a grinding device capable of adjusting the wafer thickness to a desired condition by adjusting an inclined angle of a chuck table. <P>SOLUTION: A finish thickness measuring device 80 for measuring thickness of only a secondary ground wafer 1 at a plurality of points in a radial direction is installed near a secondary grinding position, so as to grasp thickness distribution in the radial direction of the wafer 1 from the thickness of the wafer 1 measured by the device 80. Based on the grasped thickness distribution in the radial direction, a chuck table 20 is inclined by an inclined angle adjusting mechanism 70, and an angle of the wafer 1 relative to a grinding wheel 37 is appropriately adjusted, so as to make the wafer thickness after secondary grinding into a desired condition. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a grinding apparatus for grinding by pressing a grinding tool such as a grindstone against a surface to be ground while rotating the substrate, and in particular, the holding angle of the substrate is variable and the inclination angle of the surface to be ground with respect to the grindstone is changed. The present invention relates to a grinding apparatus capable of adjustment.

  In recent years, the miniaturization of semiconductor devices has become more and more remarkable. In order to realize thinning of a device, a device substrate such as a semiconductor wafer having a large number of devices formed on the surface thereof is subjected to backside grinding and thinning to a desired thickness before the device is separated into individual devices. Things have been done. The thinning of the wafer includes not only the thinning of the device but also the purpose of maintaining the performance by improving the heat dissipation of the device, and in recent years, from the initial thickness of the wafer of around 700 μm, Very thin devices such as 50 μm or 30 μm are manufactured.

  The wafer is usually obtained by slicing a cylindrical ingot made of a semiconductor material such as silicon into a thin disk shape with a wire saw or the like. Such a wafer is processed in parallel and parallel on both sides by lapping, double-head grinding, surface grinding, or the like at the stage of a material wafer before forming a device on the surface. Processing at this time is performed with high accuracy such that the flatness and the parallelism are within 1 μm, for example.

  For grinding a wafer (including the above-described material wafer), the wafer is sucked and held on a vacuum chuck type chuck table, and the wafer is rotated by rotating the chuck table, and a grinding tool such as a grindstone is applied to the wafer. A grinding apparatus that performs in-feed grinding such as pressing against a grinding surface is generally used. When performing backside grinding of a wafer with a device formed on the surface by such a grinding apparatus, the surface of the wafer is covered with a protective member to prevent the surface from coming into direct contact with the holding surface of the chuck table. Yes. This is done to prevent the electronics of the device from being damaged or contaminated with grinding waste.

  Generally as a protective member, the protective tape of the structure which apply | coated the adhesive about 10 micrometers on the single side | surface of the base material of about 100-200 micrometers thick polyethylene or a polyolefin sheet is mentioned. As such a protective tape, those having different thicknesses and elasticity of the base material and the adhesive material are appropriately selected according to the type of the device and the like, and are adhered to the surface of the wafer. For example, when a plurality of protruding electrodes called bumps are formed on the surface of the device, the protective tape has a large thickness of adhesive material or base material in order to buffer the influence of these electrodes. A material having high elasticity is used. Such a relatively thick and elastic protective tape has a larger amount of elastic deformation when a processing load is applied to the wafer than a thin and less elastic protective tape.

  By the way, in the above-mentioned in-feed grinding, there is a difference in the work amount per unit time due to the difference in peripheral speed between the vicinity of the rotation center of the wafer and the outer peripheral portion. The machining load increases. For this reason, the amount of elastic deformation of the protective tape adhered to the wafer increases in proportion to the distance from the rotation center, which means that the outer periphery of the wafer sinks compared to the vicinity of the rotation center. Appear. In this case, the grinding amount in the wafer thickness direction is smaller on the outer peripheral side than the rotation center, and as a result, the thickness of the wafer after grinding increases in proportion to the distance from the rotation center. , Not uniform. Such a variation tendency of the thickness becomes more prominent as the thickness or elasticity of the protective tape is larger, and becomes more prominent as the diameter of the semiconductor wafer is larger. In the case of a conventional wafer having a relatively large finished thickness, even if the thickness variation is very small (for example, about 1 to 2 μm), this thickness variation tendency was not a problem. However, when the thickness is very thin, for example, about 30 μm, the thickness variation greatly affects the finished thickness, which becomes a problem.

  In addition, when the material wafer is ground and flattened, the protective tape is not attached, but the thickness is uniform due to subtle changes in the condition of the grinding tool used and the effects of the inner and outer peripheral speed differences of the rotating wafer. For example, the cross-sectional shape tends to be processed into a concave shape with a recessed center.

  Thus, in-feed grinding tends to cause non-uniform thickness of the wafer alone, but this inconvenience is caused by tilting the rotation axis of the chuck table that holds the wafer and the angle of the surface to be ground of the wafer with respect to the grinding tool. Can be eliminated by changing the angle from parallel to an appropriate angle. For example, if the outer peripheral side of the wafer is thick, the amount of grinding on the outer peripheral side can be increased by tilting the chuck table so that the outer peripheral side is closer to the grinding tool. As a result, the thickness is uniform over the radial direction. Can be. A grinding apparatus that can adjust the angle of the rotation axis of the chuck table in this way is disclosed in, for example, Patent Document 1.

JP-A-8-90376

  In the apparatus disclosed in Patent Document 1 above, the chuck table can be tilted to uniformly grind the thickness of the wafer. In this process, however, the thickness varies after a certain amount of grinding. In accordance with the result, it is determined whether to continue grinding or end grinding. In that case, the trouble of picking up the wafer from the grinding apparatus and setting it in the thickness measuring apparatus is generated, and when the grinding is necessary again, the trouble is repeated. Therefore, the process becomes complicated and takes time, resulting in a problem that the production efficiency is lowered.

  Therefore, the present invention grasps the thickness of the substrate in a grinding apparatus capable of adjusting the thickness of the substrate to be in-feed grounded to a desired state by making the tilt angle of the holding means such as the chuck table variable. A grinding device that reduces the time and labor required for thickness measurement in the process of grinding the substrate and can smoothly proceed with the process, resulting in improved production efficiency due to reduced work time. It is intended to provide.

  The present invention has a holding surface for holding a circular substrate in a state where one surface of the substrate is exposed, and holding means capable of rotating around a rotation axis orthogonal to the holding surface; An inclination angle adjusting unit that adjusts the inclination of the rotation axis of the holding unit from the basic angle to an arbitrary angle, and a rotation axis that is disposed opposite to the holding surface of the holding unit and is parallel to the rotation axis of the holding unit in the basic angle state. The holding means and the grinding means are moved relative to each other along the direction in which the rotating shaft of the grinding means extends to approach and separate from each other, and when approaching, the grinding means In a grinding apparatus having a feeding means for grinding a surface to reduce the thickness of the substrate, the grinding section is provided with a thickness of at least the diameter of the substrate adjacent to one surface of the substrate held by the holding means. Multipoint measurement in direction Non-contact thickness measuring means capable provided, based on the results measured by said thickness measuring means, is characterized in that the inclination angle adjustment of the rotation axis of the holding means due to the tilt angle adjustment means is made.

  In the present invention, the thickness of the substrate held on the holding means is measured at a plurality of points in the radial direction by the non-contact type thickness measuring means provided in the grinding part during or immediately after the grinding of the substrate. By doing so, the thickness state (thickness distribution over the radial direction) is grasped. Based on the measurement result, if necessary, the inclination angle of the rotating shaft of the holding means is adjusted by the inclination angle adjusting means so that the thickness of the substrate becomes as desired (for example, a uniform thickness). , Proceed with grinding. By performing such an operation, it is possible to finally obtain a substrate having a desired thickness state. According to the present invention, the substrate thickness measuring means is provided in the measuring section, and the substrate thickness can be measured while the substrate is held by the holding means. Therefore, the labor for measuring the thickness is reduced and the working time is shortened.

  The present invention is a grinding apparatus suitable for use in grinding and thinning the back surface of a semiconductor wafer having a device formed on the surface and covered with a protective member such as a protective tape on the surface. When grinding such a semiconductor wafer, the thickness including the protective member that is elastically deformed under the processing load cannot be processed to the desired thickness. The thickness measuring means measures only the thickness of the semiconductor wafer not including the protective member.

  According to the present invention, it is possible to reduce the labor involved in thickness measurement in the process of grinding the substrate while grasping the thickness of the substrate, and to smoothly advance the process, thereby improving the production efficiency. There is an effect that is.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[1] Semiconductor wafer (substrate)
Reference numeral 1 in FIG. 1 indicates a disk-shaped semiconductor wafer (hereinafter abbreviated as a wafer) whose back surface is ground and thinned by the grinding apparatus of the embodiment shown in FIG. The wafer 1 is a silicon wafer or the like, and the thickness before processing is, for example, about 700 μm. A plurality of rectangular semiconductor chips 3 are partitioned on the surface of the wafer 1 by grid-like division planned lines 2. An electronic circuit (not shown) such as an IC or an LSI is formed on the surface of the semiconductor chip 3. A V-shaped notch 4 indicating a semiconductor crystal orientation is formed at a predetermined location on the peripheral surface of the wafer 1. The wafer 1 is finally cut and divided along the planned division line 2 and is divided into a plurality of semiconductor chips 3.

  When the back surface of the wafer 1 is ground, a protective tape (protective member) 5 is attached to the surface on the side where the electronic circuit is formed as shown in FIG. 1B for the purpose of protecting the electronic circuit. The As the protective tape 5, for example, a structure in which an adhesive of about 10 μm is applied to one side of a soft resin base sheet such as polyolefin having a thickness of about 100 to 200 μm is used, and the adhesive is matched to the surface of the wafer 1. It is pasted. The wafer 1 is thinned to, for example, about 30 to 50 μm by being back-ground by the grinding apparatus shown in FIG.

[2] Basic Configuration and Operation of Grinding Apparatus A grinding apparatus 10 according to an embodiment shown in FIG. 2 includes a rectangular parallelepiped base 11 having a horizontal upper surface. In FIG. 2, the longitudinal direction, the width direction, and the vertical direction of the base 11 are shown as a Y direction, an X direction, and a Z direction, respectively. A pair of columns 12 arranged in the X direction is erected on one end portion (the end portion on the back side) of the base 11 in the Y direction. The back side which is the column 12 side on the base 11 is a processing area 11A for grinding the wafer 1, and the front side supplies the unprocessed wafer 1 to the processing area 11A, and the processed wafer 1 The detachable area 11B is collected.

  In the processing area 11A, a disk-shaped turntable 13 whose rotation axis is parallel to the Z direction and whose upper surface is horizontal is rotatably provided. The turntable 13 is rotated in the direction of arrow R by a rotation drive mechanism (not shown). On the turntable 13, a plurality (three in this case) of disc-shaped chuck tables (holding means) 20 are rotatably arranged at equal intervals in the circumferential direction. Each chuck table 20 has a rotation axis that can be set parallel to the Z direction, and rotates itself, that is, rotates, and rotates when the turntable 13 rotates. The wafer 1 is held concentrically on the upper surfaces of these chuck tables 20 that are substantially horizontal.

  The chuck table 20 is a generally known vacuum chuck type, and sucks and holds the wafer 1 placed on the upper surface by a vacuum action. As shown in FIG. 3, the chuck table 20 is formed of a disk-shaped frame body 22, and a porous adsorption area 21 is formed in a shallow recess 22 b formed on the upper surface of the frame body 22. The wafer 1 is sucked and held on the upper surface (holding surface) 21 a of the suction area 21.

  As shown in FIG. 3, the chuck table 20 is installed on the upper end surface of a cylindrical body 23 via a disk-shaped upper disk 24. The chuck table 20 is fixed to the upper disk 24, and the upper disk 24 is rotatably supported by the body 23. A motor for rotating the upper disk 24 is housed in the body 23 (not shown), and the chuck table 20 is rotated by operating this motor. A flange-shaped middle disc 25 is provided integrally with the body 23 on the outer peripheral surface of the body 23 and in the intermediate portion in the axial direction. The chuck table 20, the upper disk 24 and the middle disk 25 have the same outer diameter and are provided concentrically with the body 23.

  The body 23 is supported on the frame 14 integrated with the turntable 13 via an inclination angle adjusting mechanism (inclination angle adjusting means) 70 so that the angle of the central axis 20a can be tilted. The center axis 20 a of the body 23 coincides with the rotation axis of the chuck table 20. Therefore, the angle of the rotating shaft 20 a of the chuck table 20 can be adjusted to an arbitrary angle by the tilt angle adjusting mechanism 70. The tilt angle adjusting mechanism 70 will be described in detail later.

  As shown in FIG. 2, in the state where two chuck tables 20 are arranged in the X direction in the vicinity of the column 12, a grinding unit (grinding means) 30 is disposed immediately above the chuck tables 20. Each chuck table 20 is positioned at three positions, that is, a grinding position below each grinding unit 30 and an attachment / detachment position closest to the attachment / detachment area 11 </ b> B by rotation of the turntable 13. There are two grinding positions, and a grinding unit 30 is provided for each of these grinding positions. In this case, the grinding position on the upstream side (right side in FIG. 2) in the transfer direction indicated by the arrow R of the chuck table 20 by the rotation of the turntable 13 is the primary grinding position, and the downstream grinding position is the secondary grinding position. Rough grinding is performed at the primary grinding position, and finish grinding is performed at the secondary grinding position.

  Each grinding unit 30 is fixed to a slider 40 attached to the column 12 so as to be movable up and down. The slider 40 is slidably mounted on a guide rail 41 extending in the Z direction, and can be moved in the Z direction by a ball screw type feed mechanism 43 driven by a servo motor 42. Each grinding unit 30 moves up and down in the Z direction by the feed mechanism 43 and grinds the exposed surface of the wafer 1 held on the chuck table 20 by a feed operation that approaches the chuck table 20 by lowering.

  As shown in FIG. 4, the grinding unit 30 includes a cylindrical spindle housing 31 whose axial direction extends in the Z direction, a spindle shaft 32 coaxially and rotatably supported in the spindle housing 31, and a spindle housing. The motor 33 is fixed to the upper end of 31 and rotationally drives the spindle shaft 32, and the disk-shaped flange 34 is coaxially fixed to the lower end of the spindle shaft 32. A grindstone wheel 35 is detachably attached to the lower surface of the flange 34 by attachment means such as screwing.

The grindstone wheel 35 has a plurality of grindstones 37 arranged and fixed to the lower surface of an annular frame 36 made of aluminum or the like. The lower surface that is the processing surface of the grindstone 37 is set to be orthogonal to the rotation axis of the grinding unit 30, that is, the axial direction of the spindle shaft 32. As the grindstone 37, for example, diamond abrasive grains mixed in a glassy bond material, molded, and sintered are used. Here, as the grindstone 37 of the grinding unit 30 for primary grinding, for example, a grindstone containing relatively coarse abrasive grains of about # 320 to # 400 is used. Further, as the grindstone 37 of the grinding unit 30 for secondary grinding, for example, one containing relatively fine abrasive grains of about # 2000 to # 8000 is used. Each flange 34 and each grinding wheel 35 are provided with a grinding water supply mechanism (not shown) for supplying grinding water for cooling and lubrication of the grinding surface or discharging grinding debris, and a water supply line is connected to the mechanism. Has been.
In the present embodiment, the chuck table 20, the grinding unit 30, and the tilt angle adjusting mechanism 70 constitute a grinding unit of the present invention.

  As shown in FIG. 2, on the base 11, a chuck table in which a thickness measuring gauge 50 constituted by a combination of a reference side height gauge 51 and a wafer side height gauge 52 is located on the primary grinding side and the secondary grinding side. 20, respectively. As shown in FIG. 4A, the reference-side height gauge 51 is configured such that the tip of the swinging reference probe 51a contacts the upper surface 22a of the frame body 22 of the chuck table 20 that is not covered with the wafer 1, The height position is detected. The upper surface 22a of the frame 22 is flush with the upper surface 21a of the suction area 21 that actually sucks and holds the wafer 1. The wafer-side height gauge 52 detects the height position of the upper surface of the wafer 1 by bringing the tip of the oscillating variable probe 52 a into contact with the upper surface of the wafer 1 held by the chuck table 20, that is, the surface to be ground. .

  According to the thickness measurement gauge 50, the thickness of the wafer 1 is measured based on a value obtained by subtracting the measurement value of the reference height gauge 51 from the measurement value of the wafer height gauge 52. In this case, since the protective tape 5 is adhered to the surface of the wafer 1, the thickness of the wafer 1 is calculated in consideration of the thickness of the protective tape 5. The thickness measurement point of the wafer 1 by the wafer-side height gauge 52, that is, the contact point of the variable probe 52a with the wafer 1 is preferably an outer peripheral portion close to the outer peripheral edge of the wafer 1.

  Further, as shown in FIG. 2, the grinding apparatus 10 of the present embodiment includes a finishing thickness measuring apparatus that measures the thickness of the wafer 1 held on the chuck table 20 positioned at the secondary grinding position. A (non-contact thickness measuring means) 80 is disposed on the base 11. This finishing thickness measuring apparatus 80 measures the thickness of the wafer 1 in the radial direction during the secondary grinding or after the secondary grinding is completed, and only the wafer 1 excluding the protective tape 5 is measured. A measurable non-contact type is used. The finished thickness measuring device 80 will be described in detail later together with the tilt angle adjusting mechanism 70.

  The grinding unit 30 descends at a predetermined speed (for example, about 3 to 5 μm / second for primary grinding and about 0.2 to 0.5 μm / second for secondary grinding) while the grinding wheel 35 rotates at 3000 to 5000 rpm, for example. Thus, the grindstone 37 of the grindstone wheel 35 presses the back surface, which is the surface to be ground, of the wafer 1 held on the chuck table 20, and the back surface is thereby ground. During grinding, the wafer 1 is rotated in the same direction as the grindstone wheel 35 together with the chuck table 20, but the rotation speed of the chuck table 20 is set to about 300 rpm at the maximum from about 10 rpm. The amount of grinding by the grinding unit 30 is controlled by measuring the thickness of the wafer 1 with the thickness measuring gauge 50.

  As shown in FIGS. 4B and 5, the grinding outer diameter (outer diameter of the rotation locus) 37 a of the grinding wheel 37 of the grinding wheel 35 is larger than the radius of the chuck table 20 (the radius of the suction area 21). Used. The grindstone wheel 35 is positioned so as to face the wafer 1 so that the cutting edge, which is the lower end surface of the grindstone 37 having a certain width, passes through the center of rotation of the chuck table 20, that is, the center of the wafer 1. Due to this positional relationship, the entire back surface of the wafer 1 held on the chuck table 20 and rotated by the rotation of the chuck table 20 is uniformly ground by the grindstone 37 of the grindstone wheel 35.

  5 is a schematic diagram when the turntable 13 is viewed from above, and shows a positional relationship between the grinding outer diameter 37a of the grindstone 37 and the chuck table 20. FIG. The upper surface of the chuck table 20 is previously ground by self-grinding by the grinding unit 30 in order to adjust the positional relationship with the grinding unit 30. In this self-grinding, a grindstone for grinding the chuck table is used. As a result, as shown in FIG. 6, the upper surface of the chuck table 20 descends at a slight angle toward the outer periphery with the center at the apex. It is formed in a substantially umbrella shape that is inclined. Therefore, the region where the grindstone 37 contacts and grinds the wafer 1 is limited to the range of the contact region from the center to the outer peripheral edge of the wafer 1 (the bold line arc portion indicated by reference numeral 37b).

  The wafer 1 is first ground by the grinding unit 30 at the primary grinding position, and then transferred to the secondary grinding position by the turntable 13 rotating in the R direction shown in FIG. Next is ground. As shown in FIG. 4A, the grinding striations 9 having a pattern in which a large number of arcs are radially drawn remain on the surface to be ground of the wafer 1. The grinding streak 9 is first formed in the primary grinding and removed by the secondary grinding, but a new grinding streak is formed in the secondary grinding.

  The above is the configuration related to the processing area 11A. Next, the attachment / detachment area 11B will be described. As shown in FIG. 2, a pickup robot 60 that can move up and down and includes a two-joint link type swing arm is installed in the center of the attachment / detachment area 11 </ b> B. Around the pickup robot 60, a supply cassette 61, an alignment table 62, a supply arm 63, a cleaning nozzle 67, a recovery arm 64, a spinner type cleaning unit (cleaning means) 65, counterclockwise when viewed from above. Collection cassettes 66 are respectively arranged. The cassettes 61 and 66 are for storing a plurality of wafers 1 in a horizontal posture and in a stacked state at regular intervals in the vertical direction, and are set at predetermined positions on the base 11.

  The wafer 1 to be ground is first taken out from the supply cassette 61 by the pick-up robot 60 and placed on the alignment table 62 to be determined at a certain position. Next, the wafer 1 is picked up from the alignment table 62 by the supply arm 63 and placed concentrically on the chuck table 20 waiting at the attachment / detachment position with the back surface facing up. The wafer 1 is transferred to the primary grinding position and the secondary grinding position in this order by the rotation of the turntable 13 in the R direction, and the back surface is ground by the grinding unit 30 at these grinding positions as described above.

  The primary grinding and the secondary grinding are performed while measuring the thickness of the wafer 1 by the thickness measuring gauge 50, and the feed amount of the grinding wheel 35 by the feed mechanism 43 is controlled based on the measured value, and the secondary grinding is finished. At this stage, the wafer 1 is ground to the desired thickness. In the primary grinding, rough grinding is performed to a desired thickness of, for example, 20 to 40 μm, and the rest is finish-ground by secondary grinding.

The wafer 1 for which the secondary grinding has been completed is returned to the attachment / detachment position by further rotating the turntable 13 in the R direction. The wafer 1 on the chuck table 20 returned to the attachment / detachment position is taken up by the recovery arm 64, transferred to the cleaning unit 65, washed with water and dried. The wafer 1 cleaned by the cleaning unit 65 is transferred and accommodated in the collection cassette 66 by the pickup robot 60. The cleaning water is jetted from the cleaning nozzle 67 toward the chuck table 20 positioned at the attachment / detachment position, and this operation is repeated each time the wafer 1 is ground. The chuck table 20 when the wafer 1 is supplied is always cleaned.
The basic configuration and operation of the grinding apparatus 10 have been described above. Next, the tilt angle adjusting mechanism 70 and the finished thickness measuring apparatus 80 according to the present invention will be described.

[3] Inclination Angle Adjustment Mechanism As shown in FIG. 5, the middle disc 25 is provided with one fixed support portion 25a and two movable support portions 25b and 25c. These support parts 25a-25c are arrange | positioned in the circumferential direction equal part. As shown in FIG. 3, a fixed shaft 71 fixed on the frame 14 passes through the fixed support portion 25 a of the middle disk 25. The fixed shaft 71 is fastened to the middle disc 25 by bolting or the like. The movable support portions 25 b and 25 c are moved up and down by the tilt angle adjusting mechanism 70 using the fixed support portion 25 a as a fulcrum, whereby the chuck table 20 is tilted together with the body 23.

  The tilt angle adjusting mechanism 70 in FIG. 3 is shown on the movable support portion 25c side. The tilt angle adjusting mechanism 70 on the movable support portion 25b side has the same configuration, and is movable with the rotation axis of the chuck table 20, that is, the rotation axis of the wafer 1 and the line L passing through the fixed support portion 25a shown in FIG. The tilt angle adjusting mechanisms 70 of both the support portions 25b and 25c are configured symmetrically with each other.

  As shown in FIG. 3, the tilt angle adjusting mechanism 70 includes a motor 72 fixed to the lower surface of the frame 14, and a drive bolt 73 that is screwed through the frame 14 and rotated by the motor 72. And an adjustment lever 75 supported on the frame 14 via a fulcrum block 74 so that the rocking tip is supported on the upper end of the drive bolt 73, and an adjustment lever 75. And an adjustment block 76 penetrating and fixed to the head (see Japanese Patent Application Laid-Open No. 2002-1653).

  The adjustment lever 75 has a fulcrum portion 75 a that is a base end fixed to the support block 74, and a force point portion 75 c that is a swinging tip portion is supported by the upper end portion of the drive bolt 73. And the adjustment block 76 is supported on the action point part 75b between the fulcrum part 75a and the force point part 75c. An elastic neck portion 73d having an upward convex semicircular arc shape is formed at the end portion of the adjustment lever 75 on the fulcrum portion 75a side. The drive bolt 73 moves upward or retracts downward by the operation of the motor 72, and when the vertical movement thereof is transmitted to the force point portion 75c, the elastic neck portion 73d is distorted, whereby the adjusting lever 75 swings in the vertical direction. It is like that.

  When the adjustment lever 75 swings in this manner, the adjustment block 76 supported on the action point portion 75b moves up and down. As a result, the movable support portions 25b and 25c of the middle disk 25 move up and down, and as a result, the rotation shaft 20a of the chuck table 20 tilts with the fixed support portion 25a as a fulcrum, and the chuck table 20 tilts accordingly. The rotation axis 20a of the chuck table 20 has a basic angle that is parallel to the Z direction in which the rotation axis of the grinding unit 30 (30a in FIGS. 6, 7, etc.) extends, and the inclination angle can be adjusted based on this basic angle. It has been made.

  As shown in FIG. 5, the contact area 37 b of the grindstone with respect to the wafer 1 extends from the rotation center of the wafer 1 to the fixed support portion 25 a. Therefore, when the chuck table 20 is tilted by the tilt angle adjusting mechanism 70, the contact region 37b (the region actually ground by the grindstone 37) corresponds to the fixed support portion 25a on the outer peripheral edge of the wafer 1, as shown in FIG. In a state where the portion serves as a fulcrum and the rotation center serves as a rocking end, it tilts toward and away from the grindstone 37.

[4] Finishing Thickness Measuring Device As shown in FIG. 4, the finishing thickness measuring device 80 has a plurality of (in this case, three) thickness sensors 81A, 81B, 81C. These thickness sensors 81 </ b> A to 81 </ b> C are arranged directly above the wafer 1 held on the chuck table 20 in a straight line along the radial direction of the wafer 1 and at substantially equal intervals. These thickness sensors 81 </ b> A to 81 </ b> C are supported on a base 11 via a stand 82 and are held by an arm 83 extending on the chuck table 20. The thickness sensors 81 </ b> A to 81 </ b> C have a function of measuring only the thickness of the wafer 1 excluding the protective tape 5. The thickness sensors 81 </ b> A to 81 </ b> C irradiate measurement light toward the wafer 1. An optical sensor or the like that derives the thickness of the wafer 1 from the difference in timing when the reflected light is received (see, for example, JP-A-2001-203249).

  Of the thickness sensors 81A to 81C, the thickness sensor 81A disposed on the most distal end side of the arm 83 measures the thickness near the center of the wafer 1, and the thickness sensor 83C closest to the stand 82 is The thickness near the outer periphery of 1 is measured. A thickness sensor 81B between the thickness sensors 81A and 81C measures the thickness of the intermediate portion of the wafer 1 in the radial direction. A, B, and C in FIG. 7B indicate the respective portions of the wafer 1 whose thicknesses are measured by the thickness sensors 81A, 81B, and 81C, respectively. According to the finished thickness measuring apparatus 80, the thickness sensors 81A to 81C simultaneously measure a plurality of thicknesses in the radial direction of the wafer 1 (in this case, three points), and accordingly, the cross-sectional shape of the wafer 1 is measured. Can be grasped.

  Although the arm 83 is fixed to the stand 82, the arm 83 is horizontally pivoted about the stand 82 so as to be retractable from the wafer 1, and the thickness sensors 81A to 81C are arranged on the wafer 1 when measuring the thickness. You may be made to do. When the arm 83 is turned in this way, the thickness sensor does not require the number of thickness measurement points, and one is sufficient.

  FIG. 10 shows the configuration, in which a stand 82 rotatably supported by a base is rotated by a motor 85 connected via a power transmission belt 84, and an arm 83 is attached to the stand 82. Is fixed. A thickness sensor 81D similar to the thickness sensors 81A to 81C is held at the tip of the arm 83. When the stand 82 rotates, the arm 83 rotates, and the thickness of the wafer 1 is adjusted during the rotation. It is possible to measure over the radial direction. In this form, since the thickness measurement over the radial direction cannot be performed simultaneously, the measurement time is longer than the form of FIG. 4 capable of measuring 3 points simultaneously, but the number of thickness sensors may be one, There is an advantage that the number of thickness measurement points can be increased.

Next, the operation of the tilt angle adjusting mechanism 70 and the finished thickness measuring device 80 will be described.
When it is determined that the wafer 1 has been subjected to primary grinding and secondary grinding and finished to a desired thickness, the thickness of the wafer 1 is continuously measured by the finishing thickness measuring device 80 while the wafer 1 is held on the chuck table 20. Measure. The thickness measurement is measured by the thickness sensors 81A to 81C arranged in the radial direction, and thereby the tendency of the cross-sectional shape of the wafer 1 after the secondary grinding is grasped.

  By the way, when grinding the wafer 1, the chuck table 20 is self-grinded in an umbrella shape as described above, so that the contact area 37b of the grindstone with respect to the wafer 1 is removed from the center of the wafer 1 as shown in FIG. It is set to the periphery. Therefore, the chuck table 20 is adjusted in advance to a predetermined angle from the basic angle by the tilt angle adjusting mechanism 70 so that the contact area 37b is parallel to the grinding surface of the grindstone 37. FIG. 7A shows this state. The rotating shaft 20a of the chuck table 20 is slightly tilted from a basic angle parallel to the rotating shaft 30a of the grindstone 37, and the contact area 37b of the grindstone 37 becomes the grindstone. 37 is adjusted in parallel with the grinding surface.

  When the wafer 1 is ground to a uniform thickness, the thickness of the wafer 1 is uniformly finished by making the surface to be ground of the wafer 1 parallel to the grinding surface of the grindstone 37 as shown in FIG. It is thought that you can. However, as described in “Background Art”, the processing load increases from the center of the wafer 1 toward the outer peripheral side, and the sinking amount of the protective tape 5 is proportional to the thickness. Therefore, the thickness of the wafer 1 is difficult to be ground on the outer peripheral side. As shown in FIG. 7B, the thickness tends to be non-uniform such that the center is thin and the outer peripheral side is thick.

  In order to finish the thickness of the wafer 1 uniformly, it is necessary to grind based on this tendency. For this purpose, first, the thickness of the wafer 1 after the secondary grinding is measured by the finishing thickness measuring device 80, and the diameter is measured. Know the thickness distribution in the direction. Next, based on the measurement result, it is determined at what angle the contact area 37b of the grindstone 37 to the wafer 1 should face the grindstone 37, and the tilt angle is adjusted so that the angle is realized. The chuck table 20 is tilted by the mechanism 70.

  FIG. 8A shows an example in which the wafer 1 is finished to a uniform thickness. From the state of FIG. 7A, the movable support portions 25b and 25c are lowered by a uniform amount so that the wafer 1 is moved from the center side. The chuck table 20 is inclined so that the outer peripheral side approaches the grindstone 37. By adjusting the tilt angle of the chuck table 20 in this way, the processing load becomes equal from the center to the outer periphery, and as a result, the wafer 1 is finished to a uniform thickness as shown in FIG. 8B.

  FIG. 8 shows the angle adjustment when the wafer thickness is made uniform, but the wafer 1 after the secondary grinding is required to have a thicker outer peripheral side than that shown in FIG. 7B. There is also. In that case, from the state of FIG. 7A, the movable support portions 25b and 25c are raised by a uniform amount so that the center side of the wafer 1 is closer to the grindstone 37 than the outer peripheral side as shown in FIG. 9A. The chuck table 20 is tilted. When the tilt angle of the chuck table 20 is adjusted in this way, the processing load on the center side increases, and as a result, the thickness of the wafer 1 becomes thicker toward the outer periphery as shown in FIG. 9B. Finished.

  The operation of adjusting the tilt of the chuck table 20 is performed when the thickness of the wafer 1 is measured at the stage where the secondary grinding is finished as described above and the thickness adjustment is necessary. It is also possible to measure the thickness of the wafer 1 once during the grinding to grasp the tendency of the secondary grinding, and resume the secondary grinding according to the tendency.

  In the present embodiment, after the completion of the secondary grinding or during the secondary grinding, the thickness of the wafer 1 held on the chuck table 20 by the finishing thickness measuring device 80 is measured at a plurality of points in the radial direction. Understand the thickness state (thickness distribution over the radial direction). Based on the measurement result, the tilt angle of the chuck table 20 is adjusted by the tilt angle adjusting mechanism 70 so that the thickness of the wafer 1 becomes as desired (for example, a uniform thickness) as necessary. Secondary grinding. By performing such an operation, the thickness state of the wafer 1 can be finally made as desired. According to the present embodiment, the finish thickness measuring device 80 is provided in the vicinity of the secondary grinding position, and the thickness can be measured while the wafer 1 is held on the chuck table 20. Therefore, the labor for grasping the radial thickness distribution is reduced and the working time is shortened. As a result, the production efficiency is improved.

  The finished thickness measuring device 80 of the above embodiment has a configuration in which the thickness sensors 81A to 81C are held by the arm 83 disposed on the chuck table 20, and the thickness sensors 81A to 81C are shown in FIG. It can also be provided inside the grinding part cover 91. Although not shown in FIG. 2, the grinding part cover 91 covers the upper part of the chuck table 20 positioned at the primary grinding position and the secondary grinding position, and has a shape such that the grinding unit 30 does not interfere and scatters during grinding. In order to prevent grinding water and the like from being scattered around, it is provided on each of the primary grinding side and the secondary grinding side.

  The thickness sensors 81A to 81C are attached to the lower surface of the top plate 91a of the grinding part cover 91 on the secondary grinding side, or attached to the inner surface of the side plate 91b on the attachment / detachment position side of the grinding part cover 91. In the form provided on the top plate 91a side, the thickness sensors 81A to 81C are arranged at positions where the thickness of the wafer 1 on the chuck table 20 positioned at the secondary grinding position can be measured at three points in the radial direction. The side plate 91b is provided at a position where the thickness of the wafer 1 on the chuck table 20 can be measured at three points in the radial direction while being moved from the secondary grinding position toward the attachment / detachment position by the rotation of the turntable 13. The thickness sensors 81A to 81C are arranged. Thus, by arranging the three thickness sensors 81A at appropriate positions, the thickness of the wafer 1 can be measured simultaneously, and the radial thickness distribution can be grasped in a short time.

  One thickness sensor can be attached to the inner surface of the side plate 91b, and the thickness measurement point of the wafer 1 on the chuck table 20 can be changed over the radial direction while rotating the turntable 13. In this case, the thickness sensor can measure a plurality of points on the thickness of the wafer 1 on the chuck table 20 from the center to the outer periphery while being moved from the secondary grinding position toward the attachment / detachment position by the rotation of the turntable 13. Placed in position. In the case of one thickness sensor, it takes a relatively long time to grasp the radial thickness distribution, but the number of thickness sensors can be as small as one, and the number of thickness measurement points can be increased. There are advantages such as.

It is the (a) perspective view and (b) side view of the semiconductor wafer ground back by the grinding device concerning one embodiment of the present invention. 1 is a perspective view of a grinding apparatus according to an embodiment of the present invention. It is a side view which shows a chuck table and an inclination angle adjustment mechanism. FIG. 3A is a perspective view and FIG. 3B is a side view showing a state in which a wafer back surface is ground by a grinding unit included in the grinding apparatus shown in FIG. It is a top view which shows the positional relationship of the grinding outer diameter of the grindstone of the grinding processing apparatus shown in FIG. 2, and a chuck table. It is a side view which shows tilting operation | movement of a chuck table. (A) is a side view showing the case where secondary grinding is performed with the grindstone contact area of the wafer parallel to the grindstone grinding surface, and (b) is a cross-sectional view of the wafer obtained by the grinding process. (A) is a side view showing the case where the chuck table is tilted by the tilt angle adjusting mechanism and the wafer is subjected to secondary grinding with a uniform thickness, and (b) is a sectional view of the wafer obtained by the grinding process. (A) is a side view showing a case where the chuck table is tilted by the tilt angle adjusting mechanism and the wafer is subjected to secondary grinding so that the outer peripheral side becomes thick, and (b) is a sectional view of the wafer obtained by the grinding process. . It is the (a) perspective view and (b) side view which show the form in case the thickness sensor provided in the arm of a finishing thickness measuring apparatus is one. It is a perspective view which shows the grinding processing apparatus provided with the other form of the finishing thickness measuring apparatus.

Explanation of symbols

1 ... Semiconductor wafer (substrate)
5 ... Protective tape (protective member)
DESCRIPTION OF SYMBOLS 10 ... Grinding apparatus 20 ... Chuck table (holding means)
20a: Chuck table rotation axis (rotation axis of holding means)
21a: Upper surface (holding surface) of suction area
30 ... Grinding unit (grinding means)
30a: Grinding unit rotation axis (rotation axis of grinding means)
43 ... Feeding means 70 ... Inclination angle adjustment mechanism (inclination angle adjustment means)
80 ... Finish thickness measuring device (non-contact type thickness measuring means)

Claims (2)

A holding means for holding a circular substrate in a state in which one surface of the substrate is exposed; a holding means that is rotatable about a rotation axis orthogonal to the holding surface; and An inclination angle adjusting means for adjusting the inclination of the rotation axis from a basic angle to an arbitrary angle, and a rotation axis arranged opposite to the holding surface of the holding means and parallel to the rotation axis of the holding means in the basic angle state And having a grinding part comprising a grinding means having
The holding means and the grinding means are moved relative to each other along the direction in which the rotating shaft of the grinding means extends to approach and separate from each other, and when approaching, the one surface of the substrate is ground by the grinding means. In a grinding apparatus having a feeding means for reducing the thickness of a substrate,
The grinding part is provided with a non-contact type thickness measuring unit that can measure the thickness of the substrate at least a plurality of points in the radial direction in the vicinity of the one surface of the substrate held by the holding unit. An inclination angle of the rotating shaft of the holding means is adjusted by the inclination angle adjusting means on the basis of a result measured by the thickness measuring means.   The substrate is a semiconductor wafer in which a device is formed on the surface and a protective member is coated on the surface, and the one surface is a back surface of the semiconductor wafer, and in the non-contact type thickness measuring unit, The grinding apparatus according to claim 1, wherein a thickness not including the protective member is measured.

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