JP7464412B2 - Processing Equipment - Google Patents

Description

The present invention relates to a processing device that processes the surface of a workpiece.

In the field of semiconductor manufacturing, a grinding device is known that grinds semiconductor wafers such as silicon wafers (hereafter referred to as "workpieces") into a thin, flat shape by pressing the grinding surface of a rotating grinding wheel against the workpiece to grind the workpiece.

Patent document 1 discloses an apparatus that processes a workpiece in the order of rough grinding and fine grinding.

JP 2009-117648 A

When grinding or polishing a workpiece, groove-shaped cracks may occur on the surface of the workpiece (the surface being machined). Cracks are particularly likely to occur during rough grinding using a coarse grinding wheel. When cracks occur, pieces of the workpiece may break off and get caught in the wheel, causing serious damage such as scratches to the workpiece to be machined subsequently.

However, in the past, operators would visually inspect the workpiece after machining, so they could only check for cracks after the fact. Furthermore, because it was unclear when the cracks formed, it took time to determine the cause of the cracks.

As a result, a technical problem arises that must be solved in order to quickly detect cracks, and the present invention aims to solve this problem.

In order to achieve the above-mentioned object, the processing apparatus of the present invention is a processing apparatus for processing the surface of a workpiece, and is equipped with a chuck table that can rotate while holding the workpiece by suction, a measuring means for non-contact measuring the distance to the surface of the workpiece, and a control means for adjusting the rotation period of the chuck table and the sampling period of the measuring device so that on a locus of measurement points of the measuring device that moves in a circumferential direction of the workpiece in accordance with the rotation of the chuck table, the distance between the measurement points calculated in accordance with the rotation speed of the chuck table, the rotation period of the chuck table, and the sampling period of the measuring device is less than the spot diameter of the measurement points, and the measurement points are set without gaps over the entire circumference of the locus .

With this configuration, the measurement points of the measuring device are spread around the entire circumference of the workpiece, so cracks that occur on the workpiece surface can be immediately detected while the workpiece is being processed.

In addition, in the processing device according to the present invention, it is preferable that the measuring device is an optical interference type displacement sensor.

In addition, in the processing device according to the present invention, it is preferable that the measuring device is a light quantity measuring sensor.

The present invention can immediately detect cracks that occur on the workpiece surface while the workpiece is being processed.

1 is a front view showing a grinding device according to an embodiment of the present invention; FIG. 4 is a plan view showing the arrangement relationship between the chuck table and a measuring device. FIG. 13 is a schematic diagram showing how the number of measurement points of the measuring device increases each time the chuck table rotates. 1A is a schematic diagram showing a state in which the distance between measurement points of a measurement device is wide compared to the spot diameter, and a graph showing measurement values of the measurement device. 1A is a schematic diagram showing a state in which the distance between points of a measurement device is narrow compared to the spot diameter, and a graph showing the measurement values of the measurement device. FIG. 11 is a schematic diagram showing a state in which the presence or absence of a crack is determined in a modified example of the present invention.

One 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 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 be the same as in reality. In addition, in cross-sectional views, hatching of some components may be omitted to make the cross-sectional structure of the components easier to understand.

The grinding device 1 grinds the workpiece W to make it thin and flat. The workpiece W is a semiconductor wafer such as a silicon wafer. The grinding device 1 includes a grinding means 2 and a chuck table 3.

The grinding means 2 includes a grinding wheel 21, a grinding wheel spindle 22, and a spindle feed mechanism 23.

The grinding wheel 21 is, for example, a #600 cup-shaped grinding wheel, and its lower surface forms a grinding surface 21a that grinds the workpiece W. The grinding wheel 21 is attached to the lower end of the grinding wheel spindle 22.

The grinding wheel spindle 22 is configured to rotate the grinding wheel 21 around the rotation axis 2a in the direction of arrow A in FIG. 2. Note that the rotation direction of the grinding wheel 21 is not limited to the direction of arrow A in FIG. 2, and may be the opposite direction (clockwise).

The spindle feed mechanism 23 raises and lowers the grinding wheel spindle 22 in the vertical direction. The spindle feed mechanism 23 is of a known configuration, and is composed of, for example, multiple linear guides that guide the movement direction of the grinding wheel spindle 22, and a ball screw slider mechanism that raises and lowers the grinding wheel spindle 22. The spindle feed mechanism 23 is interposed between the grinding wheel spindle 22 and the column 24.

The chuck table 3 is equipped with a chuck spindle 31. The chuck spindle 31 is configured to be driven to rotate around the rotation axis 3a in the direction of arrow B in FIG. 2. Note that the rotation direction of the chuck spindle 31 is not limited to the direction of arrow B in FIG. 2, and may be the opposite direction (counterclockwise).

The chuck table 3 has an adsorbent (not shown) made of a porous material such as alumina embedded in its upper surface. The chuck table 3 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 chuck table 3 is adsorbed and held on the chuck table 3. When the compressed air source or water supply source is activated, the adsorption between the workpiece W and the chuck table 3 is released.

The grinding device 1 is equipped with a measuring device 4. The measuring device 4 is disposed above the chuck table 3. The measuring device 4 is an optical interference type displacement sensor, such as Opt-measure manufactured by Tokyo Seimitsu Co., Ltd.

The measuring device 4 emits light toward the surface of the workpiece W and receives the light reflected by the surface of the workpiece W, thereby non-contact measuring the distance (displacement) between the measuring device 4 and the surface of the workpiece W. In other words, the measuring device 4 measures the distance to the workpiece W at a measuring point P that is set directly below the measuring device 4.

The measurement point P is preferably set near the periphery of the workpiece W where cracks are relatively likely to occur (for example, about 5 mm inside from the outer periphery of the workpiece W). The measurement point P on the workpiece W moves in the circumferential direction of the workpiece W along the circular trajectory L in FIG. 2 by the rotational drive of the chuck table 3.

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 held by suction on the chuck table 3. Next, the grinding wheel 21 is moved above the workpiece W by the slider of the spindle feed mechanism 23. Then, while the grinding wheel 21 and the chuck table 3 are both rotated, the grinding surface 21a of the grinding wheel 21 is pressed against the workpiece W, thereby grinding the workpiece W.

Next, the measuring device 4 measures the distance to the measurement point P on the workpiece W and sends the measurement value to the control device 5. Also, as the workpiece W rotates around the rotation axis 3a, the measurement point P on the workpiece moves in the circumferential direction of the workpiece W.

The control device 5 also adjusts the rotation period of the chuck table 3 and the phase difference of the sampling period of the measuring device 4 so that the measurement point P covers the entire circumference of the trajectory L by repeatedly rotating the workpiece W. An example of the measurement conditions for the chuck table 3 and the measuring device 4 is shown below.

[Measurement condition]
・Outer diameter of workpiece W: 12 inches
・Thickness of workpiece W: 25 μm
Rotation speed of chuck table 3: 201 rpm
Chuck table 3 frequency: 3.35 Hz
Position of measurement point P: 5 mm inward from the outer periphery of the workpiece
Measurement point P spot diameter: approx. 50 μm
Sampling period of measuring device 4: 1025 Hz

Figures 3(a) to (c) are schematic diagrams showing how the number of measurement points P increases according to the number of rotations of the chuck table 3. Figure 3(a) shows the positional relationship of the measurement points P when the workpiece W rotates once, Figure 3(b) shows the positional relationship of the measurement points P when the workpiece W rotates twice, and Figure 3(c) shows the state in which the measurement points P cover the entire circumference of the workpiece W. Note that the spot diameter of the measurement points P in Figure 3 is enlarged for ease of explanation.

Under the measurement conditions described above, as shown in FIG. 3(a), when the workpiece W rotates once, the number of measurement points P is approximately 306, and the distance between the measurement points P is approximately 2978 μm. Similarly, as shown in FIG. 3(b), when the workpiece W rotates twice, the number of measurement points P is approximately 612, and the distance between the measurement points P is approximately 1489 μm. Thus, when the number of rotations of the workpiece W is low, the distance between the measurement points P exceeds the spot diameter of the measurement points P, and the measurement points P of the measuring device 4 are sparsely scattered on the trajectory L.

After that, the workpiece W continues to rotate, and when the workpiece W completes 67 revolutions, as shown in FIG. 3(c), the number of measurement points P becomes approximately 20,500, the distance between the measurement points P becomes 44.4 μm, which is smaller than the spot diameter of the measurement points P (50 μm), and the measurement points P are set without gaps all around the circumference of the locus L.

Next, the control device 5 determines whether or not cracks (tiny steps) have occurred on the surface of the workpiece W based on the measurements made by the measuring device 4.

Specifically, as shown in FIG. 4(a), when the distance between adjacent measurement points P on the workpiece W is significantly longer than the diameter of the measurement points P, if a crack is formed between the adjacent measurement points P, the control device 5 cannot detect the crack based on the variation in displacement because there is no variation in the measurement value of the measuring device 4 as shown in FIG. 4(b). Note that the measurement value of the measuring device 4 shown in FIG. 4(b) is the differentiation of the variation in the distance between the measuring device 4 and the surface of the workpiece W, and because there is no variation in the distance between the measuring device 4 and the surface of the workpiece W, the measurement value is approximately constant.

On the other hand, as shown in FIG. 5(a), when adjacent measurement points P are spread over almost the entire circumference of the locus L and the distance between adjacent measurement points P on the workpiece W is shorter than the diameter of the measurement points P, at least one measurement point P is located inside the crack, and the measurement value of the measuring device 4 varies according to the position of the crack as shown in FIG. 5(b), so the control device 5 can detect the crack based on the variation in displacement. Note that the measurement value of the measuring device 4 shown in FIG. 5(b) is the differentiated variation in the distance between the measuring device 4 and the surface of the workpiece W, and the measurement value increases and then decreases before and after the crack.

In this way, the control device 5 can immediately detect cracks formed on the surface of the workpiece W during grinding processing of the workpiece W.

When the workpiece W has been ground to the desired thickness, the rotation of the grinding wheel 21 and the chuck table 3 is stopped, and the slider of the spindle feed mechanism 23 is activated to move the grinding wheel 21 away from the workpiece W. Then, the suction hold of the workpiece W by the chuck table 3 is released, and the grinding process of the workpiece W by the grinding device 1 is completed.

In addition, instead of the above-mentioned configuration, the measuring device 4 may be a light quantity measuring sensor that measures the light intensity of the light reflected by the surface of the workpiece W. In this case, as shown in Figures 6(a) and (b), the measurement value of the measuring device 4 fluctuates so as to decrease at the crack, so that the control device 5 can detect the presence or absence of a crack based on the fluctuation in the light intensity of the reflected light. Note that, as such a measuring device 4, it is possible to use a spectroscope of the displacement sensor described above, but this is not limited to this.

Furthermore, the present invention can be modified in various ways other than those described above without departing from the spirit of the present invention, and it goes without saying that the present invention extends to such modifications.

In this embodiment, the measuring device 4 is applied to the grinding device 1, but the measuring device 4 can also be applied to a polishing device that polishes the workpiece W with a polishing pad.

1: Grinding equipment (processing equipment)
2: Grinding means 21: Grinding wheel 21a: Grinding surface 22: Grinding wheel spindle 23: Spindle feed mechanism 24: Column 3: Chuck table 3a: Rotating shaft 31: Chuck spindle 4: Measuring device (measuring means)
5: Control device (control means)
L: Path P: Measurement point W: Workpiece

Claims (3)

A processing device for processing a surface of a workpiece,
a chuck table that can rotate while suction-holding the workpiece;
A measuring means for measuring a distance to a surface of the workpiece in a non-contact manner;
a control means for adjusting the rotation period of the chuck table and the sampling period of the measuring device so that, on a locus of measurement points of the measuring device which moves in a circumferential direction of the workpiece in response to the rotation of the chuck table, a distance between the measurement points calculated in response to the rotation speed of the chuck table, the rotation period of the chuck table, and the sampling period of the measuring device is less than a spot diameter of the measurement points, and the measurement points are set without gaps over the entire circumference of the locus ;
A processing apparatus comprising: The processing device according to claim 1, characterized in that the measuring device is an optical interference type displacement sensor. 2. The processing apparatus according to claim 1, wherein the measuring device is a light quantity measuring sensor.