JP2021142627A - Processing device - Google Patents

Abstract

To provide a processing device that can reduce variation in thickness of a processed work-piece, for example, an upstream side in a rotation direction of a grinding stone thinner than a downstream side thereof in a surface of the work-piece, so as to process the work-piece into a desired thickness.SOLUTION: A grinding device comprises an adsorbent 33 that can adsorb and hold a work-piece W and a rotary table 34 having the adsorbent 33 provided on an upper surface thereof. The adsorbent 33 is arranged to be eccentric to an upstream side in an offset direction D3 of the work-piece W from a rotation center O1 of the rotary table 34. This enables the work-piece to be ground where being eccentric to the upstream side in the offset direction from the rotation center of the rotary table, so that a downstream side in the offset direction of the work-piece is ground in larger grinding amounts than that of the upstream side because contact areas in which a grindstone contacts the work-piece vary, which can cancel variation in grinding amount such as a state where the downstream side in the offset direction of the work-piece is apt to be thicker than the upstream side thereof.SELECTED DRAWING: Figure 7

Description

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

In the field of semiconductor manufacturing, backside grinding is performed to grind the back side of a work in order to form a semiconductor wafer (hereinafter referred to as “work”) such as a silicon wafer into a thin film.

As a processing device for grinding the back surface of the work, as shown in Patent Document 1, a spindle feed mechanism having a grindstone attached to the lower end is suspended in a constant pressure cylinder, and a frictional force acting on the grindstone cut into the work is predetermined. It is known that the constant pressure cylinder raises the spindle and the spindle feed mechanism in the vertical direction when the value is higher than the value.

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 grindstone and the work do not come into excessive contact with each other. Is ground in ductile mode, so stable grinding can be performed without damaging the workpiece.

Japanese Patent No. 6030265

By the way, as shown in FIG. 8, in a work W such as a silicon wafer, an epitaxial film is formed with an off angle of about 1 to 4 degrees so as to reduce crystal defects, and the surface of the work W is { It is tilted by the off-angle with respect to the 0001} plane (basal surface).

When such a work W is in-feed ground, that is, when the grindstone 100 is pressed against the work W in a state where the grindstone 100 and the work W held by the chuck 101 are rotated, respectively, as shown in FIG. Since the grindstone 100 cuts from all angles with respect to the surface of the work W, the grinding resistance when the grindstone 100 cuts smoothly into the step of the work W (the grindstone cuts from the upstream side to the downstream side in the offset direction). Is smaller than the grinding resistance when the grindstone cuts so that it is caught in the step of the work (the grindstone cuts from the downstream side in the offset direction toward the upstream side), so that the upstream side in the offset direction is from the downstream side in the work W surface. There is a problem that the work tends to be thin and the thickness of the workpiece after processing varies.

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

In order to achieve the above object, the processing apparatus according to the present invention is a processing apparatus for flattening a work with a grindstone, and has an adsorbent capable of adsorbing and holding the work and a rotary table provided with the adsorbent on the upper surface. And, the adsorbent is eccentrically arranged from the rotation center of the rotary table to the upstream side in the offset direction of the work.

According to this configuration, the work is ground in a state of being eccentric to the upstream side in the offset direction from the rotation center of the rotary table, and the downstream side in the offset direction of the work is due to the fluctuation of the contact area between the grindstone and the work. By grinding with a larger grinding amount than the upstream side, the variation in the grinding amount, which tends to be thicker on the downstream side in the offset direction of the work than on the upstream side, is offset, so that the variation in the thickness of the work after machining is reduced. can do.

According to the present invention, the variation in the grinding amount, which tends to be thicker on the downstream side in the offset direction of the work than on the upstream side, is offset, so that the variation in the thickness of the work after machining can be reduced.

The perspective view which shows the grinding apparatus which concerns on one Embodiment of this invention. The plan view of the main unit shown in FIG. A side view of the main unit shown in FIG. Top view showing a chuck and a work. The schematic diagram which shows the direction which a grindstone cuts into a work surface. The plan view which compared the contact area between a work and a grindstone at two places in a work. The figure which shows a state that a workpiece is ground. The schematic diagram which shows the crystal structure of the work surface. The plan view which shows the workpiece after grinding by the conventional grinding apparatus.

An embodiment of the present invention will be described with reference to the drawings. In the following, when referring to the number, numerical value, quantity, range, etc. of components, it is limited to the specific number unless it is clearly stated or in principle it is clearly limited to the specific number. It is not a thing, and it may be more than or less than a specific number.

In addition, when referring to the shape and positional relationship of components, etc., unless otherwise specified or when it is considered that this is not the case in principle, those that are substantially similar to or similar to the shape, etc. shall be used. include.

In addition, the drawings may be exaggerated by enlarging the characteristic parts in order to make the features easy to understand, and the dimensional ratios and the like of the components are not always the same as the actual ones.

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

The grinding device 1 includes a main unit 2 including a grindstone 21 and a transport unit 3 arranged below the main unit 2.

The main unit 2 includes an arched column 22, a grindstone spindle 23 to which a grindstone 21 is attached, three linear guides 24 that slidably support the grindstone spindle 23 in the vertical direction V, and a grindstone spindle 23 in the vertical direction. It is provided with a spindle feed mechanism 25 that moves up and down to V.

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

The linear guide 24 is a guide rail of a 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.

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

The rear linear guide 24b is provided at the bottom of the groove 22b in parallel with each other along the vertical direction V. A saddle 23a is attached to the rear linear guide 24b via a nut 25a, which will be described later.

As shown in FIG. 3, the front linear guide 24a and the rear linear guide 24b are arranged so that the center of gravity G of the grindstone spindle 23 is arranged in the triangle T formed by the front linear guide 24a and the rear linear guide 24b in a plan view. Are arranged apart from each other.

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.

When the motor 25c is driven and the ball screw 25b is rotated, the nut 25a slides in the feeding direction D1 of the ball screw 25b parallel to the vertical direction V, so that the saddle 23a is lowered.

The main unit 2 is provided with an air cylinder 26. One air cylinder 26 is provided on each side of the horizontal direction H with the spindle feed mechanism 25 interposed therebetween. The air cylinder 26 has a known configuration including a cylinder (not shown), a piston, a piston rod, a compressor, and the like.

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

In the air cylinder 26, the grindstone spindle 23 and the spindle feed mechanism 25 are suspended in the groove 22b, and the piston rod of the air cylinder 26 is connected to the motor 25c. By providing the air cylinders 26 on both sides of the spindle feed mechanism 25 in the horizontal direction H, it is possible to prevent the spindle feed mechanism 25 from tilting in the horizontal direction H when the spindle feed mechanism 25 moves up and down.

The transport unit 3 includes a chuck 31 capable of sucking and holding the work W, and a slider 32 on which the chuck 31 is placed.

The chuck 31 includes an adsorbent 33 made of a porous material such as alumina on the upper surface thereof, and a compact rotary table 34 in which the adsorbent 33 is embedded substantially in the center. The chuck 31 includes a conduit (not shown) that extends through the interior to the surface. The pipeline is connected to a vacuum source, compressed air source or water supply source via a rotary joint (not shown). When the vacuum source is activated, the work W placed on the adsorbent 33 is adsorbed and held by the adsorbent 33. Further, when the compressed air source or the water supply source is activated, the adsorption between the work W and the adsorbent 33 is released.

The slider 32 can be slid on the rail 35 by a slider drive mechanism (not shown), whereby the chuck 31 and the slider 32 slide integrally in the transport direction D2.

The adsorbent 33 is formed in a shape corresponding to the work W when viewed from a plane. Further, the rotary table 34 is formed in a substantially circular shape when viewed from a plane, but the shape of the rotary table 34 is not limited to this. Further, the chuck 31 can be rotated around a vertical axis passing through the rotation center O1 of the chuck 31 by a servomotor (not shown).

As shown in FIG. 4, the adsorbent 33 is eccentric from the rotation center O1 of the rotary table 34, that is, the center O2 of the adsorbent 33 is only a predetermined distance from the rotation center O1 of the rotary table 34 when viewed from a plane. It is arranged at an offset. 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.

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 work W in the offset direction D3. As shown in FIG. 5, the “offset direction D3” means a direction in which the normal vector p of the {0001} plane of the work W is projected on a plane from the tip end to the base end. Further, the “upstream side of the offset direction D3” means the side facing the tip of the normal vector p obtained by projecting the normal vector p of the {0001} plane of the work W onto a plane. Further, hereinafter, the "downstream side of the offset direction D3" is the side opposite to the direction in which the tip of the normal vector p projected on the plane of the {0001} plane of the work W is facing. Means.

Since the center O2 of the adsorbent 33 is arranged offset from the rotation center O1 of the rotary table 34, the amount of grinding in the work W is locally increased or decreased. For example, as shown in FIG. 6, a region S1 in which the machined surface of the grindstone 21 contacts the work W over a relatively wide area and a region S2 in which the machined surface of the grindstone 21 contacts the work W in a relatively small area. By comparison, the area S1 is wider than the area S2.

When the grindstone 21 is uniformly contacted with the work W over the entire surface, the grinding amount of the work W decreases as the contact area between the work W and the grindstone 21 increases, and the work W after grinding becomes It gets thicker. Therefore, when comparing the thicknesses in the regions S1 and S2 shown in FIG. 6, the region S1 is thicker than the region S2 in the work W after grinding.

In this way, the work W vacuum-sucked on the chuck 31 is carried into the lower part of the grindstone 21 by the slider 32 before the grinding process, and is carried out from the lower part of the grindstone 21 to the rear of the main unit 2 after the grinding process. NS.

The grinding device 1 is provided with an in-process gauge 4 for measuring the thickness of the work W. The in-process gauge 4 measures the thickness of the work W during machining.

The operation of the grinding device 1 is controlled by the control device 5. The control device 5 controls each of the components constituting the grinding device 1. The control device 5 is composed of, for example, a CPU, a memory, and the like. The function of the control device 5 may be realized by controlling using software, or may be realized by operating using hardware.

Next, a procedure for grinding the work W using the grinding device 1 will be described.

First, the offset direction D3 of the work W is measured using a known X-ray diffractometer.

Next, the work W is attracted 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. Further, the ball screw 25b is rotated in the forward direction, and the nut 25a and the saddle 23a are slid in the feeding direction D1 to lower the grindstone 21 to the vicinity of the work W.

Next, the grindstone 21 and the chuck 31 are rotated, respectively. For example, the rotation speed of the grindstone spindle 23 is set to 2000 rpm, and the rotation speed of the chuck 31 is set to 300 rpm. The number of the grindstone 21 is, for example, # 8000.

The spindle feed mechanism 25 brings the grindstone spindle 23 close to the work W, and the grinding process is started from the state where the grindstone 21 is seated on the work W. For example, the feed rate of the spindle feed mechanism 25 is set to 0.4 μm / s.

The grinding process is performed by grinding the work W in a ductile mode in a so-called floating state in which the abrasive grains of the grindstone 21 do not excessively contact the work W during the grinding process.

Specifically, the grindstone spindle 23 grinds while pressing the grindstone 21 against the work W under its own weight (for example, 20 kg), and when the frictional force acting on the grindstone 21 is transmitted to the piston rod, it enters the cylinder of the air cylinder 26. Raise the piston to push back the filled compressed air. Therefore, when the grindstone 21 tries to cut deeper than the desired grinding amount (for example, Dc value) and the frictional force acting on the grindstone 21 becomes excessive, the grindstone spindle 23 and the spindle feed mechanism 25 temporarily rise. As a result, the grindstone 21 is prevented from cutting above the Dc value.

By the way, in in-feed grinding in which the grindstone 21 and the work W are rotated and the grindstone 21 is pressed against the work W to grind the work W, the upstream side in the offset direction D3 is compared with the downstream side due to the crystal structure of the work W. It tends to be thin, and the thickness of the work W after processing may vary.

However, the work W rotates around the rotation center O1 of the rotary table 34 in a state of being eccentric to the upstream side of the offset direction D3 with respect to the rotation center O1 of the rotary table 34, so that the grindstone 21 and the work W come into contact with each other. By changing the area according to the rotation angle of the chuck 31, the above-mentioned thickness variation of the work W is reduced.

Specifically, as shown in FIGS. 7A to 7D, the grindstone 21 when the rotation angle of the chuck 31 is changed to Θ degrees, (Θ + 90) degrees, (Θ + 180) degrees, and (Θ + 270) degrees. Comparing the contact area between the work W and the work W (the range indicated by the arrow in FIG. 7), when the rotation angle of the chuck 31 is Θ degrees, the contact area between the grindstone 21 and the work W is the largest, so that the grinding amount of the work W is the largest. Is the minimum.

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 work W is the narrowest, so that the grinding amount of the work W is maximized. That is, the range in which the grinding amount of the work W is locally increased is set on the downstream side of the offset direction D3 of the work W. The arrows (a) to (d) in the figure indicate the direction in which the grindstone 21 in FIGS. 7 (a) to 7 (d) cuts into the work W.

In this way, the thickness of the work W varies by increasing or decreasing the grinding amount according to the change in the contact area between the grindstone 21 and the work W so as to offset the variation in the grinding amount due to the crystal structure of the work W. Can be reduced.

Then, when the measured value of the in-process gauge 4 reaches the finish thickness of the work W, the ball screw 25b is rotated in the reverse direction to raise the nut 25a and the saddle 23a, thereby separating the grindstone 21 from the work W and grinding. To finish.

It should be noted that the present invention can be modified in various ways as long as it does not deviate from the spirit of the present invention, and it is natural that the present invention extends to the modified ones.

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: Adsorbent 34: Rotating table 35: Rail 4: In-process gauge 5: Control device W: Work

Claims (1)

It is a processing device that flattens the work with a grindstone.
An adsorbent capable of adsorbing and holding the work and an adsorbent
A rotary table with the adsorbent on the upper surface and
With
A processing apparatus characterized in that the adsorbent is eccentrically arranged on the upstream side in the offset direction of the work from the rotation center of the rotary table.

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