JP7464410B2 - Processing Equipment - Google Patents

Description

The present invention relates to a processing device for processing non-circular workpieces.

In the field of semiconductor manufacturing, back grinding is performed to grind the back side of a semiconductor wafer such as a silicon wafer (hereinafter referred to as the "workpiece") to form a thin film.

As shown in Patent Document 1, a processing device for grinding the back surface of a workpiece is known in which a spindle feed mechanism with a grinding wheel attached to its lower end is suspended from a constant pressure cylinder, and when the frictional force acting on the grinding wheel cutting into the workpiece is higher than a predetermined value, the constant pressure cylinder raises the spindle and spindle feed mechanism vertically.

In this type of grinding machine, if the frictional force acting on the grinding wheel becomes excessive, the constant pressure cylinder temporarily raises the spindle and spindle feed mechanism, so that the workpiece is ground in a ductile mode without excessive contact between the grinding wheel and the workpiece, allowing the workpiece to be ground stably without damaging it.

Japanese Patent No. 6030265

However, when grinding a non-circular workpiece such as a rectangular workpiece while rotating the grinding wheel and the workpiece, the contact area between the grinding wheel and the workpiece is not always constant; for example, areas where the contact area between the grinding wheel and the workpiece is relatively large tend to have a smaller amount of workpiece ground than areas where the contact area is relatively small. In other words, if the grinding wheel is brought into uniform contact with the workpiece, there is a problem in that the thickness of the processed workpiece will vary depending on the fluctuation in the contact area between the grinding wheel and the workpiece.

As a result, a technical problem arises that must be solved in order to process a non-circular workpiece to the desired thickness, and the present invention aims to solve this problem.

In order to achieve the above object, the processing device according to the present invention is a processing device for machining a non-circular workpiece into a flat surface, and includes a holding means including a chuck capable of suction-holding the workpiece, a chuck spindle for rotating the chuck, and a detection unit capable of detecting the rotation angle of the chuck, a processing means including a grindstone for machining the workpiece, a grindstone spindle for rotating the grindstone, a spindle feed mechanism for moving the grindstone vertically, and an air cylinder for holding the spindle feed mechanism, and a control means for increasing or decreasing the air pressure supplied to the air cylinder for each predetermined rotation angle of the chuck in response to changes in the contact area between the workpiece and the grindstone, thereby raising and lowering the grindstone.

With this configuration, the grinding wheel is raised and lowered for each specified rotation angle of the chuck in response to changes in the contact area between the workpiece and the grinding wheel as the chuck rotates, thereby preventing local changes in the amount of machining of a non-circular workpiece and reducing variations in the thickness of the machined workpiece caused by the shape of the workpiece.

In addition, in the processing device according to the present invention, it is preferable that when the contact area is larger than a preset reference area, the control means increases the air pressure supplied to the air cylinder above the preset reference pressure to lower the grinding wheel.

This configuration makes it possible to prevent localized reductions in the amount of machining within the contact area between the workpiece and the grindstone that is larger than the reference area.

In addition, in the processing device according to the present invention, it is preferable that when the contact area is smaller than a preset reference area, the control means reduces the air pressure supplied to the air cylinder below the preset reference pressure to raise the grinding wheel.

This configuration makes it possible to prevent localized increases in the amount of machining within the contact area between the workpiece and the grindstone that is smaller than the reference area.

By raising and lowering the grinding wheel at each specified rotation angle of the chuck in response to changes in the contact area between the workpiece and the grinding wheel as the chuck rotates, the present invention can suppress local changes in the amount of machining of a non-circular workpiece and reduce variations in the thickness of the machined workpiece caused by the shape of the workpiece.

1 is a perspective view showing a grinding device according to an embodiment of the present invention; FIG. 2 is a side view of the main unit shown in FIG. 1 . FIG. 2 is a plan view of the main unit shown in FIG. 1 . 1 is a plan view comparing the contact areas between the workpiece and the grinding wheel at two points in the workpiece. FIG. FIG. 13 is a diagram showing how the height position of the grinding wheel is changed according to the rotation angle of the chuck.

The embodiment of the present invention will be described with reference to the drawings. Note that in the following, when referring to the number, numerical value, amount, range, etc. of components, unless otherwise specified or when it is 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.

In addition, when referring to the shape or positional relationship of components, etc., this includes things that are substantially similar or similar to that shape, etc., unless otherwise specified or considered in principle to be clearly different.

In addition, drawings may exaggerate characteristic parts to make the features easier to understand, and the dimensional ratios of components may not necessarily be the same as in reality.

The grinding device 1 grinds the workpiece W to form a thin film. In the following, a workpiece W that is square in plan view will be described as an example, but the shape of the workpiece W is not limited to this. The workpiece W that is ground using the grinding device 1 is preferably a silicon wafer, silicon carbide wafer, or other workpiece that exhibits high hardness and brittleness, but is not limited to these.

The grinding device 1 includes a main unit 2 equipped with a grinding wheel 21 and a conveying unit 3 arranged below the main unit 2.

The main unit 2 includes an arch-shaped column 22, a grinding wheel spindle 23 to which the grinding wheel 21 is attached, three linear guides 24 that support the grinding wheel spindle 23 so that it can slide in the vertical direction V, and a spindle feed mechanism 25 that raises and lowers the grinding wheel spindle 23 in the vertical direction V.

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

The linear guide 24 is a guide rail for the saddle 23a that rises and falls along the vertical direction V, and is composed of two front linear guides 24a and one rear linear guide 24b.

The front linear guides 24a are disposed on the edge of the groove 22b in front of the column 22 and are arranged parallel to each other along the vertical direction V. In addition, the saddle 23a is directly attached to the front linear guides 24a.

The rear linear guides 24b are arranged parallel to each other along the vertical direction V at the bottom of the groove 22b. In addition, the saddle 23a is attached to the rear linear guides 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 spaced apart from each other so that the center of gravity G of the grinding wheel spindle 23 is located within the triangle T formed by the front linear guide 24a and the rear linear guide 24b in a plan view.

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 to rotate the ball screw 25b, the nut 25a slides in the feed direction D1 of the ball screw 25b, which is parallel to the vertical direction V, and the saddle 23a descends.

The main unit 2 is provided with an air cylinder 26. The air cylinders 26 are provided on both sides of the spindle feed mechanism 25 in the horizontal direction H. The air cylinders 26 are of known construction and comprise a cylinder, a piston, a piston rod, a compressor, etc. (not shown).

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

The air cylinder 26 suspends the grinding wheel spindle 23 and the spindle feed mechanism 25 within 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, the spindle feed mechanism 25 is prevented from tilting in the horizontal direction H when it moves up and down.

The transport unit 3 includes a chuck 31 capable of suction-holding the workpiece W, a detector 32 that detects the rotation angle of the chuck 31, and a slider 33 on which the chuck 31 is placed.

The chuck 31 has an adsorbent 34 made of a porous material such as alumina on its upper surface, and a dense body 35 in which the adsorbent 34 is embedded approximately in the center. The chuck 31 has a conduit (not shown) that runs through the inside and reaches the surface. The conduit 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 adsorbent 34 is adsorbed and held by the adsorbent 34. When the compressed air source or water supply source is activated, the adsorption between the workpiece W and the adsorbent 34 is released.

The adsorption body 34 is formed into a shape corresponding to the workpiece W when viewed from above. In addition, the dense body 35 is formed into a substantially circular shape when viewed from above, but the shape of the dense body 35 is not limited to this. In addition, the chuck 31 can be rotated around a vertical axis passing through the center of the chuck 31 by a servo motor (not shown).

The detection unit 32 detects the rotation angle of the chuck 31 and sends a detection signal to the control device 5 described below each time the chuck 31 rotates a predetermined angle. For example, since the rotation angle of the chuck 31 corresponds to the rotation angle of the servo motor that rotates the chuck 31, the detection unit 32 can detect the rotation angle of the chuck 31 by reading the rotation angle of the servo motor.

The slider 33 can slide on the rail 36 by a slider drive mechanism (not shown), so that the chuck 31 and the slider 33 slide together in the transport direction D2.

In this way, the workpiece W vacuum-adsorbed onto the chuck 31 is transported by the slider 33 to below the grinding wheel 21 before grinding, and is transported from below the grinding wheel 21 to the rear of the main unit 2 after grinding.

The grinding device 1 is provided with an in-process gauge 4 that measures the thickness of the workpiece W. The in-process gauge 4 measures the thickness of the workpiece W during processing.

The operation of the grinding device 1 is controlled by the control device 5. The control device 5 controls each of the components that make up the grinding device 1. The control device 5 is composed of, for example, a CPU, a memory, etc. The functions of the control device 5 may be realized by controlling it using software, or may be realized by operating it using hardware.

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

First, the workpiece W is attracted and held by the chuck 31. Then, the ball screw 25b is rotated in the forward direction, and the nut 25a and saddle 23a are slid in the feed direction D1 to lower the grinding wheel 21 to the vicinity of the workpiece W.

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

The spindle feed mechanism 25 brings the grinding wheel spindle 23 close to the workpiece W, and grinding begins when the grinding wheel 21 is seated on the workpiece W. For example, the feed speed of the spindle feed mechanism 25 is set to 0.4 μm/s.

The grinding process is performed by ductile mode grinding of the workpiece W in a so-called floating state, in which the abrasive grains of the grinding wheel 21 do not come into excessive contact with the workpiece W during the grinding process.

Specifically, the grinding wheel spindle 23 performs grinding while pressing the grinding wheel 21 against the workpiece W with its own weight (e.g., 20 kg), and when the frictional force acting on the grinding wheel 21 is transmitted to the piston rod, the piston is raised so as to push back the compressed air filled inside the cylinder of the air cylinder 26. Therefore, if the grinding wheel 21 attempts to cut deeper than the desired grinding amount (e.g., Dc value) and the frictional force acting on the grinding wheel 21 becomes excessive, the grinding wheel spindle 23 and spindle feed mechanism 25 are temporarily raised. This prevents the grinding wheel 21 from cutting deeper than the Dc value.

When the measurement value of the in-process gauge 4 reaches the finishing thickness of the workpiece W, the ball screw 25b is rotated in the reverse direction to raise the nut 25a and saddle 23a, thereby separating the grindstone 21 from the workpiece W and completing the grinding process.

However, when grinding the workpiece W while rotating the grinding wheel 21 and the square workpiece W, the contact area between the grinding wheel 21 and the workpiece W is not constant, which can cause the thickness of the workpiece W after grinding to vary across the surface of the workpiece W. This variation in the amount of grinding is more likely to occur with finer grinding wheels 21, which are more likely to be affected by fluctuations in the contact area with the workpiece W.

For example, as shown in FIG. 4, when comparing the contact area S1 between the workpiece W and the grindstone 21 (rotation angle of the chuck 31 = Θ) where the machining surface of the grindstone 21 passes through the corner of the workpiece W and the rotation center O of the chuck 31, and the contact area S2 between the workpiece W and the grindstone 21 (rotation angle of the chuck 31 = Θ - 45 degrees) where the machining surface of the grindstone 21 passes through the center of the side of the workpiece W and the rotation center O, the contact area S1 is approximately twice as large as the contact area S2.

When the grinding wheel 21 is brought into uniform contact with the workpiece W over its entire surface, as the contact area between the workpiece W and the grinding wheel 21 increases, the amount of workpiece W ground decreases, and the workpiece W becomes thicker after grinding. Therefore, when comparing the thicknesses within the contact areas S1 and S2 shown in Figure 4, it is predicted that the contact area S1 will be thicker than the contact area S2 in the workpiece W after grinding.

Therefore, the grinding device 1 suppresses the variation in thickness of the workpiece W after grinding by the following procedure.

[Preparation process]
First, the contact area between the workpiece W and the grindstone 21 is calculated for each predetermined rotation angle of the chuck 31, and stored in the control device 5. Note that the interval of the rotation angle of the chuck 31 for calculating the contact area can be changed arbitrarily.

The control device 5 also compares the contact area (reference area) between the workpiece W and the grindstone 21 at a pre-stored reference rotation angle of the chuck 31 with the contact area between the workpiece W and the grindstone 21 for each rotation angle of the chuck 31, and calculates and stores the height position of the grindstone 21 relative to the workpiece W during processing and the air pressure supplied to the air cylinder 26 that can achieve that height position of the grindstone 21 for each rotation angle of the chuck 31.

Specifically, when the contact area between the workpiece W and the grinding wheel 21 is larger than the reference area, the air pressure supplied to the air cylinder 26 is increased to lower the grinding wheel 21 from the reference position, thereby locally increasing the amount of grinding of the workpiece W. Note that the "reference position" refers to the height position of the grinding wheel 21 within the reference area. This makes it possible to prevent a local decrease in the amount of grinding within the contact area between the workpiece W and the grinding wheel 21 that is larger than the reference area.

On the other hand, if the contact area between the workpiece W and the grinding wheel 21 is smaller than the reference area, the air pressure supplied to the air cylinder 26 is reduced to raise the grinding wheel 21 above the reference position and locally reduce the amount of grinding of the workpiece W. This makes it possible to prevent a local increase in the amount of grinding within the contact area between the workpiece W and the grinding wheel 21 that is smaller than the reference area.

The amount of elevation of the grinding wheel 21 relative to the reference position and the air pressure of the air cylinder 26 are preferably set to offset thickness variations within the surface of the workpiece W that occur when performing normal grinding.

For example, when grinding a 300 mm square mold substrate as shown in Figure 4 as a sample, and a thickness variation of about 3 μm occurs within the surface of the workpiece W, the height position of the grinding wheel 21 within the maximum contact area S1 (rotation angle of the chuck 31: Θ degrees) must be lowered by about 3 μm from the height position of the grinding wheel 21 within contact area S2 (rotation angle of the chuck 31: Θ-45 degrees).

Therefore, if the air pressure of the air cylinder 26 during normal grinding is taken as the reference pressure, the air pressure of the air cylinder 26 within the contact area S1 is increased by a predetermined amount (e.g., about 0.2 MPa) above the reference pressure.

Furthermore, when the rotation angle of the chuck 31 is between (Θ-45) degrees and (Θ+45) degrees, the amount of pressure applied to the reference pressure of the air cylinder 26 is set between 0 and 0.2 MPa in proportion to the ratio of the contact areas of the workpiece W and the grindstone 21. Note that the amount of pressure applied to the reference pressure can vary depending on the grit size of the grindstone 21, the material of the workpiece W, etc.

[Grindstone position adjustment]
When the grinding wheel 21 is pressed against the workpiece W while rotating the grinding wheel 21 and the workpiece W to grind the workpiece W, the detection unit 32 detects the rotation angle of the chuck 31 during processing and sends the rotation angle of the chuck 31 to the control device 5.

Next, the control device 5 adjusts the amount of grinding performed by the grinding wheel 21 on the workpiece W by increasing or decreasing the air pressure of the air cylinder 26 so that the height position of the grinding wheel 21 matches the pre-stored height position of the grinding wheel 21 for each rotation angle of the chuck 31 based on the rotation angle of the chuck 31 detected by the detection unit 32. Figure 5 is a schematic diagram showing how the height position of the grinding wheel 21 changes depending on the rotation angle of the chuck 31.

In this way, the grinding device 1 according to this embodiment adjusts the amount of grinding that the grinding wheel 21 grinds the workpiece W for each rotation angle of the chuck 31 in response to changes in the contact area between the workpiece W and the grinding wheel 21, thereby preventing localized changes in the amount of grinding of the non-circular workpiece W and reducing variations in the thickness of the workpiece W after grinding that are caused by the shape of the workpiece W.

The present invention can be modified in various ways without departing from the spirit of the invention, and it goes without saying that the present invention also covers such modifications.

1: Grinding device 2: Main unit (processing means)
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 (holding means)
31: chuck 32: detector 33: slider 34: suction body 35: dense body 36: rail 4: in-process gauge 5: control device (control means)
W: Work

Claims (3)

A processing device for flattening a non-circular workpiece,
a holding means including a chuck capable of suction-holding the workpiece, a chuck spindle for rotating the chuck, and a detection unit capable of detecting a rotation angle of the chuck;
a processing means including a grindstone for processing the workpiece, a grindstone spindle for rotating the grindstone, a spindle feed mechanism for vertically moving the grindstone, and an air cylinder for holding the spindle feed mechanism;
a control means for increasing or decreasing the air pressure supplied to the air cylinder for each predetermined rotation angle of the chuck in response to a change in a contact area between the workpiece and the grindstone, thereby raising or lowering the grindstone;
A processing apparatus comprising: The processing device according to claim 1, characterized in that, when the contact area is larger than a preset reference area, the control means increases the air pressure supplied to the air cylinder above the preset reference pressure to lower the grindstone. 3. The processing apparatus according to claim 1, wherein, when the contact area is smaller than a preset reference area, the control means reduces the air pressure supplied to the air cylinder below the preset reference pressure to raise the grinding wheel.

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