Processing device

Abstract

To provide a working device for working workpiece to a desired thickness.SOLUTION: A grinding device 1 for in-feed grinding workpiece W includes a chuck 31 rotatable in a state of sucking and holding the workpiece W, and a grinding wheel 21 for grinding the workpiece W. At the time of in-feed grinding of the workpiece W, the workpiece W is sucked and held on the chuck 31 in a state of being decentered to the upstream side in an off-set direction of the workpiece W from the center of rotation of the chuck 31.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a processing apparatus for processing a non-circular workpiece.

Background Art

[0002] In the field of semiconductor manufacturing, back grinding for grinding the back surface of a semiconductor wafer such as a silicon wafer (hereinafter referred to as "workpiece") is performed to form a thin film on the workpiece.

[0003] As a processing apparatus for performing back grinding of a workpiece, as shown in Patent Document 1, a spindle feed mechanism having a grindstone attached to its lower end is suspended by a constant pressure cylinder, and when the frictional force acting on the grindstone cut into the workpiece is higher than a predetermined value, a device is known in which the constant pressure cylinder raises the spindle and the spindle feed mechanism in the vertical direction.

[0004] In such a grinding machine, when the frictional force acting on the grindstone becomes excessive, the constant pressure cylinder temporarily raises the spindle and the spindle feed mechanism, so that the workpiece is ground in a ductile mode without excessive contact between the grindstone and the workpiece, and thus the workpiece can be stably ground without being damaged.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, as shown in FIG. 8, in a workpiece W such as a silicon wafer, an epitaxial film is formed with an off-angle of about 1 to 4 degrees so that crystal defects are reduced, and the surface of the workpiece W is inclined by the angle of the off-angle with respect to the {0001} plane (basal plane).

[0007] When performing infeed grinding on such a workpiece W, that is, as shown in Fig. 9, when grinding by pressing the grinding wheel 100 against the workpiece W while rotating the grinding wheel 100 and the workpiece W held by the chuck 101 respectively, since the grinding wheel 100 cuts in from all angles with respect to the surface of the workpiece W, when the grinding wheel 100 smoothly cuts into the step of the workpiece W (the grinding wheel cuts in from the upstream side to the downstream side in the offset direction), the grinding resistance is smaller than when the grinding wheel cuts in so as to catch on the step of the workpiece (the grinding wheel cuts in from the downstream side to the upstream side in the offset direction). Therefore, there is a problem that the upstream side in the offset direction in the plane of the workpiece W tends to be thinner than the downstream side, and thickness variations occur in the workpiece after processing.

[0008] Therefore, a technical problem to be solved arises in order to process the workpiece to a desired thickness, and an object of the present invention is to solve this problem.

Means for Solving the Problem

[0009] In order to achieve the above object, a processing apparatus according to the present invention is a processing apparatus for performing planar processing on a workpiece, and includes a chuck that can rotate while sucking and holding the workpiece, A grinding wheel attached to a grinding wheel spindle having a rotation axis parallel to the rotation axis of the chuck, and as the grinding wheel spindle rotates, the grinding wheel passes through the rotation center of the chuck while rotating to the workpiece and a grinding wheel that is pressed against the workpiece to perform planar processing on the workpiece. The workpiece is sucked and held by the chuck in a state of being eccentric to the upstream side in the offset direction of the workpiece from the rotation center of the chuck.

[0010] According to this configuration, the workpiece is ground in a state of being eccentric to the upstream side in the offset direction from the rotation center of the chuck, and due to the variation in the contact area between the grinding wheel and the workpiece, the downstream side in the offset direction of the workpiece is ground with a larger grinding amount than the upstream side. As a result, the variation in the grinding amount, in which the downstream side in the offset direction of the workpiece tends to be thicker than the upstream side, is offset, and thus the thickness variation of the workpiece after processing can be reduced.

Effect of the Invention

[0011] In the present invention, the variation in the grinding amount, where the downstream side in the offset direction of the workpiece tends to be thicker than the upstream side, is compensated, so that the thickness variation of the workpiece after processing can be reduced.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0013] Embodiments of the present invention will be described with reference to the drawings. In the following, when referring to the number of components, numerical values, amounts, ranges, etc., unless otherwise specified or clearly limited to a specific number in principle, it is not limited to that specific number, and it may be more or less than the specific number.

[0014] Also, when referring to the shape, positional relationship of components, etc., unless otherwise specified or clearly not considered to be so in principle, it includes those substantially similar or analogous to the shape, etc.

[0015] In addition, the drawings may be exaggerated, such as by enlarging characteristic portions for easier understanding of the characteristics, and the dimensional ratios of the components are not necessarily the same as the actual ones.

[0016] The grinding device 1 grinds a workpiece W to form a thin film. The workpiece W to be ground using the grinding device 1 is preferably a silicon wafer or the like, but is not limited thereto.

[0017] The grinding device 1 includes a main unit 2 having a grindstone 21, and a conveyance unit 3 disposed below the main unit 2.

[0018] The main unit 2 includes an arch-shaped column 22, a grindstone spindle 23 to which the grindstone 21 is attached, three linear guides 24 that slidably support the grindstone spindle 23 in the vertical direction V, and a spindle feed mechanism 25 that raises and lowers the grindstone spindle 23 in the vertical direction V.

[0019] The grindstone spindle 23 is housed in a groove 22b recessed in the front surface 22a of the column 22 over the vertical direction V. The grindstone spindle 23 includes a saddle 23a having the grindstone 21 attached to its lower end, and a motor (not shown) provided in the saddle 23a for rotating the grindstone 21.

[0020] The linear guide 24 is a guide rail for the saddle 23a that moves up and down along the vertical direction V, and is composed of two front linear guides 24a and one rear linear guide 24b.

[0021] The front linear guide 24a is disposed at the edge of the groove 22b in front of the column 22 and is provided in parallel to each other along the vertical direction V. Further, the saddle 23a is directly attached to the front linear guide 24a.

[0022] The rear linear guide 24b is provided in parallel to each other along the vertical direction V at the bottom of the groove 22b. Further, the saddle 23a is attached to the rear linear guide 24b via a nut 25a described later.

[0023] As shown in FIG. 3, the front linear guide 24a and the rear linear guide 24b are spaced apart from each other such that the center of gravity G of the grindstone spindle 23 is disposed within a triangle T formed by the front linear guide 24a and the rear linear guide 24b in a plan view.

[0024] The spindle feed mechanism 25 includes a nut 25a that connects the saddle 23a and the rear linear guide 24b, a ball screw 25b that raises and lowers the nut 25a, and a motor 25c that rotates the ball screw 25b.

[0025] When the motor 25c is driven and the ball screw 25b rotates, the nut 25a slides in the feed direction D1 of the ball screw 25b parallel to the vertical direction V, so that the saddle 23a descends.

[0026] An air cylinder 26 is provided in the main unit 2. The air cylinders 26 are provided one on each side in the horizontal direction H with the spindle feed mechanism 25 interposed therebetween. The air cylinder 26 has a known configuration including a cylinder, a piston, a piston rod, a compressor, etc. (not shown).

[0027] The driving pressure of the air cylinder 26 is set to be equal to or less than a value corresponding to the frictional force acting on the grindstone 21 when the grindstone 21 cuts in by the critical cutting depth (Dc value) of the workpiece W. The Dc value varies depending on the material of the workpiece W. For example, it is 0.09 μm for a silicon wafer and 0.15 μm for a silicon carbide wafer. Further, by adjusting the pressure (air pressure) of the compressed air supplied to the air cylinder 26, the pressing force with which the air cylinder 26 presses the grindstone 21 against the workpiece W via the spindle feed mechanism 25 can be adjusted, and the position (height position) of the grindstone 21 in the vertical direction V can be raised and lowered.

[0028] The air cylinder 26 suspends the grindstone spindle 23 and the spindle feed mechanism 25 in the groove 22b, and the piston rod of the air cylinder 26 is connected to the motor 25c. By providing the air cylinder 26 on both sides in the horizontal direction H with the spindle feed mechanism 25 interposed therebetween, it is possible to suppress the spindle feed mechanism 25 from tilting in the horizontal direction H when the spindle feed mechanism 25 moves up and down.

[0029] The transfer unit 3 includes a chuck 31 capable of sucking and holding the workpiece W, and a slider 32 on which the chuck 31 is placed.

[0030] The chuck 31 includes a suction body 33 made of a porous material such as alumina on the upper surface, and a rotating table 34 of a dense body embedded substantially at the center of the suction body 33. The chuck 31 includes a pipeline (not shown) that passes through the inside and extends to the surface. The pipeline is connected to a vacuum source, a compressed air source, or a water supply source via a rotary joint (not shown). When the vacuum source is activated, the workpiece W placed on the suction body 33 is sucked and held by the suction body 33. Also, when the compressed air source or the water supply source is activated, the suction between the workpiece W and the suction body 33 is released.

[0031] The slider 32 is slidable on the rail 35 by a slider drive mechanism (not shown), and thereby, the chuck 31 and the slider 32 slide integrally in the transport direction D2.

[0032] The suction body 33 is formed in a shape corresponding to the workpiece W when viewed from the plane. Also, the rotating table 34 is formed in a substantially circular shape when viewed from the plane, but the shape of the rotating table 34 is not limited thereto. Further, the chuck 31 is rotatable about a vertical axis passing through the rotation center O1 of the chuck 31 by a servo motor (not shown).

[0033] As shown in FIG. 4, the adsorbent 33 is eccentric from the rotation center O1 of the rotary table 34. That is, when viewed from the plane, the center O2 of the adsorbent 33 is offset by a predetermined distance from the rotation center O1 of the rotary table 34. Note that the offset amount between the rotation center O1 of the rotary table 34 and the center O2 of the adsorbent 33 can be arbitrarily changed.

[0034] The direction in which the adsorbent 33 is offset from the rotation center O1 of the rotary table 34 is the upstream side of the offset direction D3 of the workpiece W. Note that the "offset direction D3" means the direction from the tip to the base of the vector obtained by projecting the normal vector p of the {0001} plane of the workpiece W onto the plane, as shown in FIG. 5. Further, the "upstream side of the offset direction D3" means the side toward which the tip of the normal vector p obtained by projecting the normal vector p of the {0001} plane of the workpiece W onto the plane faces. Further, hereinafter, the "downstream side of the offset direction D3" means the side opposite to the direction toward which the tip of the normal vector p obtained by projecting the normal vector p of the {0001} plane of the workpiece W onto the plane faces.

[0035] Since the center O2 of the adsorbent 33 is offset from the rotation center O1 of the rotary table 34, the grinding amount in the workpiece W locally increases or decreases. For example, as shown in FIG. 6, when comparing the region S1 where the machining surface of the grindstone 21 contacts the workpiece W over a relatively wide range and the region S2 where the machining surface of the grindstone 21 contacts the workpiece W with a relatively small area, the region S1 is wider than the region S2.

[0036] When the grindstone 21 is uniformly brought into contact with the entire surface of the workpiece W, as the contact area between the workpiece W and the grindstone 21 increases, the grinding amount of the workpiece W decreases and the workpiece W after grinding becomes thicker. Therefore, when comparing the thicknesses in the regions S1 and S2 shown in FIG. 6, in the workpiece W after grinding, the region S1 is thicker than the region S2.

[0037] In this way, the workpiece W vacuum-sucked on the chuck 31 is carried by the slider 32 to below the grinding wheel 21 before grinding, and is carried out from below the grinding wheel 21 to the rear of the main unit 2 after grinding.

[0038] The grinding device 1 is provided with an in-process gauge 4 for measuring the thickness of the workpiece W. The in-process gauge 4 measures the thickness of the workpiece W during processing.

[0039] The operation of the grinding device 1 is controlled by the control device 5. The control device 5 controls each component constituting the grinding device 1. The control device 5 is composed of, for example, a CPU, a memory, etc. Note that the function of the control device 5 may be realized by controlling using software, or may be realized by operating using hardware.

[0040] Next, the procedure for grinding the workpiece W using the grinding device 1 will be described.

[0041] First, using a known X-ray diffractometer, the offset direction D3 of the workpiece W is measured.

[0042] Next, the workpiece W is adsorbed and held by the chuck 31 in a state of being eccentric to the upstream side in the offset direction D3 with respect to the rotation center O1 of the rotary table 34. Also, the ball screw 25b is rotated forward, and the nut 25a and the saddle 23a are slid in the feed direction D1 to lower the grinding wheel 21 to the vicinity of the workpiece W.

[0043] Next, the grinding wheel 21 and the chuck 31 are rotated respectively. For example, the rotation speed of the grinding wheel spindle 23 is set to 2000 rpm, and the rotation speed of the chuck 31 is set to 300 rpm. The grit size of the grinding wheel 21 is, for example, #8000.

[0044] The spindle feed mechanism 25 approaches the grinding wheel spindle 23 to the workpiece W, and grinding is started from the state where the grinding wheel 21 seats on the workpiece W. For example, the feed speed of the spindle feed mechanism 25 is set to 0.4 μm / s.

[0045] The grinding process is performed by grinding the workpiece W in a so-called floating state where the abrasive grains of the grinding wheel 21 do not excessively contact the workpiece W during the grinding process in the ductile mode.

[0046] Specifically, while the grinding wheel spindle 23 presses the grinding wheel 21 against the workpiece W with its own weight (for example, 20 kg) to perform the grinding process, when the frictional force acting on the grinding wheel 21 is transmitted to the piston rod, the piston is lifted so as to push back the compressed air filled in the cylinder of the air cylinder 26. Therefore, when the grinding wheel 21 tries to cut deeper than the desired grinding amount (for example, Dc value) and the frictional force acting on the grinding wheel 21 becomes excessive, the grinding wheel spindle 23 and the spindle feed mechanism 25 are temporarily lifted. As a result, the grinding wheel 21 is suppressed from cutting deeper than the Dc value.

[0047] By the way, in the infeed grinding where the grinding wheel 21 is pressed against the workpiece W while rotating the grinding wheel 21 and the workpiece W respectively to grind the workpiece W, due to the crystal structure of the workpiece W, the upstream side in the offset direction D3 tends to be thinner than the downstream side, and thickness variations may occur in the workpiece W after processing.

[0048] However, when the workpiece W rotates around the rotation center O1 of the rotary table 34 in a state of being eccentric to the upstream side in the offset direction D3 with respect to the rotation center O1 of the rotary table 34, the contact area between the grinding wheel 21 and the workpiece W changes according to the rotation angle of the chuck 31, and the above-described thickness variations of the workpiece W are reduced.

[0049] Specifically, as shown in FIGS. 7(a) to (d), when comparing the contact areas (the ranges indicated by the arrows in FIG. 7) between the grinding wheel 21 and the workpiece W when the rotation angle of the chuck 31 is changed to Θ degrees, (Θ + 90) degrees, (Θ + 180) degrees, and (Θ + 270) degrees, when the rotation angle of the chuck 31 is Θ degrees, the contact area between the grinding wheel 21 and the workpiece W is the widest, so the grinding amount of the workpiece W is minimized.

[0050] On the other hand, when the rotation angle of the chuck 31 is (Θ + 180) degrees, the contact area between the grindstone 21 and the workpiece W is the narrowest, so the grinding amount of the workpiece W becomes the largest. That is, the range where the grinding amount of the workpiece W locally increases is set on the downstream side in the offset direction D3 of the workpiece W. In addition, the arrows (a) to (d) in the figure indicate the directions in which the grindstone 21 cuts into the workpiece W in FIGS. 7(a) to (d).

[0051] In this way, by increasing or decreasing the grinding amount according to the change in the contact area between the grindstone 21 and the workpiece W so as to offset the variation in the grinding amount caused by the crystal structure of the workpiece W, the thickness variation of the workpiece W can be reduced.

[0052] When the measured value of the in-process gauge 4 reaches the finish thickness of the workpiece W, the ball screw 25b is rotated reversely to raise the nut 25a and the saddle 23a, thereby separating the grindstone 21 from the workpiece W and ending the grinding process.

[0053] Note that the present invention can be variously modified without departing from the spirit of the present invention, and it is natural that the present invention also extends to such modified ones.

Explanation of Reference Numerals

[0054] 1: Grinding device 2: Main unit 21: Grindstone 22: Column 22a: Front surface 22b: Groove 23: Grindstone spindle 23a: Saddle 24: Linear guide 24a: Front linear guide 24b: Rear linear guide 25: Spindle feed mechanism 25a: Nut 25b: Ball screw 25c: Motor 26: Air cylinder 3: Conveying unit 31: Chuck 32: Slider 33: Adsorber 34: Rotary table 35: Rail 4: In-process gauge 5: Control device W: Workpiece

Claims

【Claim 1】 A processing apparatus for planar processing of a workpiece, comprising: a chuck rotatable while sucking and holding the workpiece; a grindstone attached to a grindstone spindle having a rotation axis parallel to the rotation axis of the chuck, the grindstone being pressed against the workpiece while rotating as the grindstone spindle rotates so as to pass through the rotation center of the chuck, and planar processing the workpiece; and the workpiece is sucked and held by the chuck in a state of being eccentric upstream in the offset direction of the workpiece from the rotation center of the chuck.

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