Chipping detection device and processing device

Abstract

To provide a chipping generation detection device that promptly detects generation of chipping, and a processing device.SOLUTION: A chipping generation detection device 5 detects chipping generated in a workpiece W at the time of grinding the workpiece W adsorbed and held by a chuck 3. The chipping generation detection device 5 includes: a measurement part 55 that measures during processing an amount of reflection light reflected at a measurement point P set in a peripheral edge of a surface to be processed of the workpiece W; and a determination part 56 that calculates an average reflection light amount that is a correlation value varying according to the area where chipping is generated in the workpiece W on the basis of the reflection light amount, and determines that chipping is generated when the average reflection light amount reaches a predetermined threshold.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a chipping detection device and a processing device. [Background technology]

[0002] 2. Description of the Related Art In the field of semiconductor manufacturing, there is known an apparatus for detecting the presence or absence of processing abnormalities in a semiconductor wafer (hereinafter referred to as a "workpiece") such as a ground or polished silicon wafer.

[0003] Patent Document 1 discloses a wafer processing abnormality detection device in which a camera captures a comparison image including the workpiece surface to be processed, and a control means compares the comparison image with a reference image, and determines that grinding or polishing is not being performed normally if chipping or the like is present in the comparison image. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-136498 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the device described in Patent Document 1 determines the appropriateness of the processing after the fact by obtaining detailed information such as the size, number, and location of chippings on the workpiece after processing, so there is a problem in that it is not clear at what point in the processing the chipping occurred, and it takes time to determine the cause of the chipping.

[0006] Therefore, a technical problem arises that must be solved in order to quickly detect the occurrence of chipping, and an object of the present invention is to solve this problem. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the chipping detection device of the present invention is a chipping detection device that detects chipping that occurs in a workpiece held by suction on a chuck when the workpiece is processed, and is equipped with a measurement unit that measures the amount of reflected light reflected at a measurement point set on the periphery of the workpiece's surface to be processed during processing, and a judgment unit that calculates a correlation value that varies depending on the area of ​​the workpiece where chipping has occurred based on the amount of reflected light, and judges that chipping has occurred when the correlation value reaches a predetermined threshold value.

[0008] In addition, in order to achieve the above-mentioned object, the processing apparatus according to the present invention is equipped with the above-mentioned chipping occurrence detection device, a chuck that can rotate while holding the workpiece by suction, and a processing unit that grinds or polishes the workpiece. [Effects of the Invention]

[0009] The present invention can detect the occurrence of chipping during processing by determining that chipping has occurred when a correlation value calculated based on the amount of reflected light and varying depending on the area where chipping has occurred reaches a predetermined threshold value. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram showing a grinding device according to an embodiment of the present invention; [Figure 2] FIG. 2 is a schematic diagram showing the configuration of a pitching occurrence detection device. [Figure 3] FIG. 4 is a schematic diagram showing the positional relationship between a chuck and a pitting occurrence detection device. [Figure 4] FIG. 10 is a schematic diagram showing how the measurement points of the pitting occurrence detection device are scanned in the circumferential direction of the workpiece. [Figure 5] An enlarged view of the measurement point (part A) shown in Figure 4. [Figure 6] An enlarged view of the measurement point (part B) shown in Figure 4. [Figure 7] 1 is a table showing the measurement results of the amount of reflected light at measurement points corresponding to the rotation angle of the chuck spindle (0 degrees, 90 degrees, 180 degrees, 270 degrees). [Figure 8] Graph showing the change in the average reflected light intensity at each measurement point corresponding to the rotation angle (0 degrees, 90 degrees, 180 degrees, 270 degrees) of the chuck spindle. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the present invention will be described with reference to the drawings. Note that, hereinafter, 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 the specific number, and may be more or less than the specific number.

[0012] Furthermore, when referring to the shape or positional relationship of components, etc., it includes things that are substantially similar or approximate to those shapes, etc., unless otherwise specified or when it is clearly considered otherwise in principle.

[0013] In addition, the drawings may exaggerate characteristic parts to make the features easier to understand, and the dimensional proportions of the 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.

[0014] The grinding apparatus 1 shown in Fig. 1 grinds a workpiece W to make it thin and flat. The workpiece W is a semiconductor wafer such as a silicon wafer. The grinding apparatus 1 includes grinding means 2 and a chuck 3.

[0015] The grinding means 2 includes a grinding wheel 21, a grinding wheel spindle 22, and a spindle feed mechanism 23.

[0016] The grinding wheel 21 is, for example, a #600 cup-shaped grinding wheel, and its lower surface constitutes a grinding surface 21a that grinds the workpiece W. The grinding wheel 21 is attached to the lower end of a grinding wheel spindle 22. Grinding water is supplied by a nozzle 24 to the vicinity where the grinding wheel 21 comes into contact with the workpiece W. Pure water is supplied by the nozzle 24 as cooling water to the grinding region where the grinding wheel 21 grinds the workpiece W.

[0017] The grinding wheel spindle 22 is configured to rotate the grinding wheel 21 around the rotation axis 2a.

[0018] The spindle feed mechanism 23 raises and lowers the grinding wheel spindle 22 in the vertical direction. The spindle feed mechanism 23 has a known configuration and is composed of, for example, a plurality of linear guides that guide the grinding wheel spindle 22 in the moving direction, 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 25.

[0019] The chuck 3 includes a chuck spindle 31. The chuck spindle 31 is configured to be rotatably driven around a rotation axis 3a. An adsorbent (not shown) made of a porous material such as alumina is embedded on the upper surface of the chuck 3. The chuck 3 includes a conduit (not shown) that runs through the interior and extends to 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 3 is adsorbed and held by the chuck 3. When the compressed air source or water supply source is activated, the adsorption between the workpiece W and the chuck 3 is released.

[0020] The operation of the grinding apparatus 1 is controlled by a control device 4. The control device 4 controls each of the components that make up the grinding apparatus 1. The control device 4 is configured with, for example, a CPU, a memory, etc. The functions of the control device 4 may be realized by control using software, or may be realized by operation using hardware.

[0021] The grinding apparatus 1 is equipped with a chipping detection device 5. The chipping detection device 5 is disposed above the chuck 3. The chipping detection device 5 is a spectral interference type film thickness sensor, such as the Si-f series manufactured by Keyence Corporation.

[0022] The chipping occurrence detection device 5 irradiates light onto the surface of the workpiece W and receives the reflected light reflected by the surface of the workpiece W, thereby measuring the amount of reflected light (amount of reflected light) at a measurement point P set directly below the chipping occurrence detection device 5.

[0023] Specifically, as shown in Fig. 2, the chipping occurrence detection device 5 is configured by connecting a plurality of optical fibers 52a and 52b to a sensor head 51. The optical fiber 52a is connected to a light source unit 53. The light source unit 53 is, for example, a halogen light source that emits white light with a wavelength of 400 to 800 nm, but is not limited to this. The optical fiber 52b is connected to a spectroscope 54.

[0024] The measurement light emitted from the light source unit 53 is irradiated via the optical fiber 52a and the sensor head 51 toward a measurement point P on the processed surface of the workpiece W. The measurement point P is preferably set near the periphery of the workpiece W where chipping is relatively likely to occur (inside the innermost periphery of the workpiece W and within a range on the outer periphery of the bottom surface of the expected chipping depth). The measurement point P on the workpiece W moves in the circumferential direction of the workpiece W by the rotational drive of the chuck 3. The spot diameter of the measurement point P is set to, for example, several tens of μm.

[0025] The light reflected by the front and back surfaces of the silicon layer of the workpiece W is received by the sensor head 51 and guided to the spectroscope 54 via the optical fiber 52b. The spectroscope 54 separates the interference light, the interference pattern of which changes depending on the film thickness (optical path length) of the silicon layer, according to wavelength, and generates a spectral waveform that indicates the relationship between wavelength and the amount of reflected light.

[0026] The measuring unit 55 measures the amount of reflected light from the spectral waveform generated by the spectroscope 54. The determining unit 56 calculates a correlation value (described later) based on the amount of reflected light. The determining unit 56 also determines whether chipping has occurred based on the correlation value.

[0027] A sensor holder 57 that houses the sensor head 51 is supported by a movement mechanism 58. The movement mechanism 58 is, for example, a linear actuator or a swing arm. The movement mechanism 58 slides the sensor head 51, thereby moving the measurement point P in the radial direction of the workpiece W.

[0028] The sensor holder 57 is formed with a first opening 57a and a second opening 57b.

[0029] The first opening 57a extends in the vertical direction of the sensor holder 57 and is opened so as to ensure the field of view of the sensor head 51.

[0030] The second opening 57b is formed on the side of the sensor holder 57 and communicates with the first opening 57a. The second opening 57b is connected to a blower 59 serving as a scattering means for supplying air. The air supplied from the blower 59 flows as shown by the arrows in FIG. 2 and is discharged to a measurement point P on the workpiece W via the first opening 57a. This exposes the processed surface of the workpiece W at the measurement point P, thereby suppressing light reflection at the measurement point P.

[0031] Next, a procedure for the chipping detection device 5 to detect chipping that has occurred in the workpiece W will be described.

[0032] The chipping detection device 5 detects the occurrence of chipping during grinding of the workpiece W. That is, first, the workpiece W is suction-held by the chuck 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 3 are each rotated, the grinding surface 21a of the grinding wheel 21 is pressed against the workpiece W, thereby grinding the workpiece W.

[0033] Then, when the workpiece W has been ground to the desired thickness, the rotation of the grinding wheel 21 and the chuck 3 is stopped, and the slider of the spindle feed mechanism 23 is activated to separate the grinding wheel 21 from the workpiece W. Then, the chuck 3 releases the workpiece W from its suction hold, and the grinding process of the workpiece W by the grinding device 1 is completed.

[0034] During grinding of such a workpiece W, the measurement unit 55 measures the amount of light reflected at a measurement point P on the workpiece W. As shown in Figures 3 and 4, the measurement point P on the workpiece is scanned in the circumferential direction of the workpiece W as the workpiece W rotates, and the locus L of the measurement point P covers the entire circumference of the workpiece W. The blackened areas in Figure 4 are areas where chipping C occurred.

[0035] The number of measurement points P is, for example, about 100, but can be changed as desired depending on the rotation speed of the chuck 3 (for example, 100 to 300 rpm) and the sampling period of the chipping occurrence detection device 5. For example, it is preferable to arrange adjacent measurement points P so that they at least partially overlap each other, since this allows measurement points P to be arranged around the entire circumference of the workpiece W. On the other hand, it is preferable to arrange adjacent measurement points P at an appropriate interval, since this allows the amount of reflected light to be measured in a short time.

[0036] Next, the determining unit 56 determines whether or not chipping (minute chips) has occurred on the surface of the workpiece W based on the amount of reflected light.

[0037] For example, if no chipping occurs within the measurement point P, almost the entire amount of irradiated light is reflected, and therefore almost the entire amount of irradiated light is measured as the amount of reflected light.

[0038] On the other hand, the amount of light reflected by the silicon layer within the measurement point P decreases according to the area (chipping area) occupied by the chipping within the spot range of the measurement point P, which is due to the size and number of chippings occurring in the silicon layer. Therefore, when the chipping area of ​​chipping C within the measurement point P as shown in Figure 5 is relatively small, the amount of reflected light decreases, and when the chipping area of ​​chipping C within the measurement point P as shown in Figure 6 is relatively large, the amount of reflected light decreases further. In other words, there is an inverse correlation between the amount of reflected light and the chipping area of ​​chipping C.

[0039] Fig. 7 shows the measurement results of the reflected light amount at measurement points P corresponding to the rotation angles (0 degrees, 90 degrees, 180 degrees, 270 degrees) of the chuck spindle 31, measured every 60 seconds from the start of machining until 300 seconds, and the average reflected light amount per revolution (hereinafter simply referred to as "average reflected light amount"), which is the average value of the reflected light amount at each measurement point P corresponding to the rotation angles (0 degrees, 90 degrees, 180 degrees, 270 degrees) of the chuck spindle 31. Fig. 8 also shows a graph related to the change in the average reflected light amount.

[0040] Here, the average reflected light amount is a correlation value that correlates with the size and number of chippings at each measurement point P, and is a value that decreases as the chipping area increases. The sampling range of the measurement points P for calculating the average reflected light amount is preferably set to a wide range in order to detect all chipping occurrences, but it may be a part of the circumferential direction of the workpiece W as long as the average reflected light amount can be stably calculated. Furthermore, instead of the average reflected light amount, the correlation value may be an integrated value of the reflected light amount at each measurement point P scanned in the circumferential direction of the workpiece W.

[0041] 7, it can be seen that the average reflected light intensity remains constant at 178.5 until the processing time reaches 180 seconds. However, when the processing time reaches 240 seconds, the average reflected light intensity drops significantly to 95.25, and when the processing time reaches 300 seconds, it further drops to 92.75.

[0042] When the threshold value of the average reflected light amount is set to, for example, 100, the determining unit 56 determines that chipping occurred during a processing time of 180 to 240 seconds. The threshold value of the average reflected light amount can be changed arbitrarily.

[0043] In this way, the chipping occurrence detection device 5 of this embodiment is a chipping occurrence detection device 5 that detects chipping that occurs in the workpiece W when the workpiece W held by suction on the chuck 3 is ground, and is configured to include a measurement unit 55 that measures the amount of reflected light reflected at a measurement point P set on the periphery of the workpiece W's surface to be machined during processing, and a judgment unit 56 that calculates a correlation value that varies depending on the chipping area based on the amount of reflected light, and judges that chipping has occurred when the correlation value reaches a predetermined threshold value.

[0044] According to this configuration, the determination unit 56 determines that chipping has occurred when the correlation value, which varies depending on the chipping area, reaches a predetermined threshold value, thereby making it possible to quickly and comprehensively detect the possibility that chipping has occurred without having to specify the size, number, or location of the chipping that has occurred.

[0045] In addition, in the grinding device 1 according to this embodiment, the measurement unit 55 measures the amount of reflected light that decreases according to the area occupied by chipping at the measurement point P, the correlation value is the average value of the amount of reflected light at each measurement point P when the measurement point P is scanned in the circumferential direction of the workpiece W, and the judgment unit 56 is configured to judge that chipping has occurred on the workpiece W when the correlation value drops to a predetermined threshold value.

[0046] According to this configuration, the correlation value is set to the average value of the amount of reflected light at each measurement point P set along the circumferential direction of the workpiece W, making it possible to detect the occurrence of chipping over a wide area.

[0047] In addition, the chipping occurrence detection device 5 of this embodiment is configured so that the measuring unit 55 includes a sensor head 51 that irradiates light and receives reflected light, and a moving mechanism 58 that can move the sensor head 51 in the radial direction of the workpiece W.

[0048] According to this configuration, the measurement point P set directly below the sensor head 51 can be set at any position within the surface of the workpiece W.

[0049] In addition, the grinding device 1 according to this embodiment is configured to include the above-mentioned chipping occurrence detection device 5, a chuck 3 that can rotate while holding the workpiece W by suction, and a grinding means 2 that grinds the workpiece W.

[0050] According to this configuration, chipping can be determined to have occurred when the average amount of reflected light, which correlates with the size or number of chippings, reaches a threshold value, thereby enabling the occurrence of chipping to be detected quickly and comprehensively.

[0051] The correlation value used to determine the occurrence of chipping is not limited to the average reflected light amount at the four measurement points P set at equal intervals on the workpiece W as described above. For example, the judgment unit 56 may determine the presence or absence of chipping for each measurement point P, and the ratio may be used as a correlation value that varies depending on the area where chipping has occurred.

[0052] 7 and 8, for example, at a processing time of 180 seconds, the amount of reflected light does not reach a threshold value (e.g., 100) at any of the measurement positions of 0 degrees, 90 degrees, 180 degrees, and 270 degrees, so the determining unit 56 determines that no chipping has occurred at any of the measurement positions. Therefore, the correlation value, which is the ratio of the determination of the presence or absence of chipping, is constant.

[0053] On the other hand, at a processing time of 240 seconds, the amount of reflected light at measurement positions of 0 degrees and 180 degrees does not fall below the threshold, and it is determined that chipping has not occurred, whereas at measurement positions of 90 degrees and 270 degrees, the amount of reflected light falls below the threshold, and it is determined that chipping has occurred. Therefore, the correlation value, which is the ratio of the chipping presence / absence determination, fluctuates.

[0054] In addition, instead of the above-mentioned configuration, the chipping occurrence detection device 5 may detect chipping based on whether or not interference light is detected, which is the result of reflection light reflected on the front and back surfaces of the silicon layer of the workpiece W interfering with each other.

[0055] Specifically, if the amount of reflected light falls below a predetermined threshold, the spectrometer 54 cannot generate a spectral waveform. Therefore, a threshold for the amount of reflected light that allows a spectral waveform to be generated may be associated with a criterion for determining whether chipping has occurred, and if the amount of reflected light is sufficient to generate a spectral waveform, it may be determined that chipping has not occurred, and if the amount of reflected light has decreased to such an extent that a spectral waveform cannot be generated, it may be determined that chipping has occurred. The ratio of these determinations may be set to a correlation value that varies depending on the area where chipping has occurred.

[0056] 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 also covers such modifications.

[0057] Although this embodiment has been described as an example in which the chipping detection device 5 is applied to a grinding device 1, it is also possible to apply the chipping detection device 5 to a polishing device that polishes the workpiece W with a polishing pad. [Explanation of symbols]

[0058] 1: Grinding equipment (processing equipment) 2: Grinding means (processing part) 21: Grinding wheel 21a: Grinding surface 22: Grinding wheel spindle 23: Spindle feed mechanism 24: Nozzle 25: Column 3: Zipper 31: Chuck spindle 4: Control device 5: Chipping detection device 51: Sensor head 52a, 52b: optical fiber 53: Light source unit 54: Spectrometer 55: Measuring part 56: Judgment section 57: Sensor holder 57a: First opening 57b: Second opening 58: Movement mechanism 59: Blower (dispersion means) L: Locus P:Measurement point W: Work

Claims

1. A chipping detection device that detects chipping that occurs in a workpiece when the workpiece is machined while being held by a chuck, a measuring unit that measures the amount of reflected light reflected at a measurement point set on the periphery of the workpiece surface during processing; a determination unit that calculates a correlation value that varies depending on an area where the chipping has occurred on the workpiece based on the amount of reflected light, and determines that the chipping has occurred when the correlation value reaches a predetermined threshold value; Equipped with the measuring unit measures the amount of reflected light that decreases in accordance with the area occupied by the chipping at the measurement point; The correlation value is an average value or an integrated value of the amount of reflected light at each measurement point when the measurement point is scanned in the circumferential direction of the workpiece, The chipping detection device is characterized in that the judgment unit judges that chipping has occurred in the workpiece when the correlation value drops to a predetermined threshold value.

2. A chipping detection device that detects chipping that occurs in a workpiece held by suction on a chuck when the workpiece is machined, a measuring unit that measures the amount of reflected light reflected at a measurement point set on the periphery of the workpiece surface during processing; a determination unit that calculates a correlation value that varies depending on an area where the chipping has occurred on the workpiece based on the amount of reflected light, and determines that the chipping has occurred when the correlation value reaches a predetermined threshold value; Equipped with Further provided is a spectroscope that decomposes the interference light resulting from the interference of the reflected light from the front and back surfaces of the workpiece according to wavelength and generates a spectral waveform that indicates the relationship between each wavelength and the amount of reflected light, the correlation value is a ratio of whether or not the reflected light amount at each measurement point exceeds the light amount capable of generating the spectral waveform when the measurement points are scanned in the circumferential direction of the workpiece, The chipping detection device is characterized in that the judgment unit judges that chipping has occurred in the workpiece when the correlation value drops to a predetermined threshold value.

3. The measurement unit a sensor head that irradiates the light and receives the reflected light; a movement mechanism capable of moving the sensor head in a radial direction of the workpiece; The chipping detection device according to claim 1 or 2, further comprising:

4. 3. The chipping detection device according to claim 1, wherein the measuring unit includes a scattering means for scattering the fluid within the area of ​​the work surface onto which the light is irradiated.

5. The chipping detection device according to any one of claims 1 to 4, a chuck that can rotate while suction-holding the workpiece; a processing unit that grinds or polishes the workpiece; A processing device comprising:

Images