TW201908051A - Grinding device - Google Patents

Abstract

An object of the present invention is to provide a grinding device capable of performing grinding processing under suitable processing conditions. The solution of the present invention is a grinding device including a suction cup table; a grinding unit comprising a main shaft and a grinding stone that is installed under the main shaft and rotates along with the rotation of the main shaft, wherein the grinding stone is used to grind a workpiece held on the suction cup table; a grinding and feeding unit which carries out grinding and feeding of the grinding unit toward the holding surface; an AE sensor mounted to the grinding unit or the grinding feeding unit; and a control unit, wherein the control unit rotates the suction cup table and the grinding stone when the workpiece is being ground, and the grinding unit is enabled to grind and feed through the grinding feeding unit so as to allow the grinding stone to contact the workpiece, and the control unit controls the rotation speed of the suction cup table, the rotation speed of the grinding stone, or the grinding and feeding speed of the grinding feeding unit that enables the grinding and feeding of the grinding unit according to an elastic wave generated by the grinding and detected by the AE sensor.

Description

Grinding device

The present invention relates to a grinding device for grinding a plate-like workpiece.

In a process of forming a device wafer including a semiconductor device or an optical device from a plate-shaped workpiece made of silicon, gallium arsenide, sapphire, glass, or the like, the plate-shaped workpiece is ground and thinned to a predetermined thickness. Thickness grinding device will be used. This grinding device includes a chuck table holding the plate-like workpiece, a grinding unit for grinding the workpiece, and a grinding feed unit for grinding the grinding unit in a vertical direction.

The grinding unit includes a main shaft that extends in the vertical direction, a grinding wheel attached to a lower end of the main shaft, and a grinding vermiculite attached to a lower surface of the grinding wheel. During grinding of the workpiece, the main shaft is rotated to rotate the grinding wheel, and the grinding feed unit is operated to grind the grinding unit. Once the grinding vermiculite mounted on the rotating grinding wheel comes into contact with the workpiece, grinding of the workpiece is started.

During grinding processing, a load (hereinafter referred to as a processing load) generated by the processing is applied to the workpiece or the grinding unit. If a machining load exceeding the allowable range is applied to the workpiece or the grinding unit, damage or chipping of the workpiece may occur, and abnormal grinding stone consumption may prevent normal grinding processing from being performed. Then, in order to suppress the occurrence of such a problem, a technique for detecting an abnormality of the processing load has been developed (see Patent Document 1).

This technique measures the current value of the motor that rotates the main shaft during the grinding process of the workpiece. The current value reflects the machining load generated by the grinding process. When the current value exceeds a predetermined threshold value, it is determined that the processing load is abnormal. When abnormal processing load is measured, for example, measures such as slowing down the grinding feed rate of the grinding unit, slowing down the rotation speed of the grinding wheel, and the chuck table can reduce the processing load. [Previous Technical Documents] [Patent Documents]

[Patent Document 1] Japanese Patent Application Publication No. 2012-161861

(Problems to be solved by the invention)

However, the current value of the motor that rotates the spindle may change due to a small individual difference in the workpiece. For example, even when an abnormality occurs in the grinding process, the current value may be observed to be low. For this reason, the threshold may be set to a low value so that the occurrence of an abnormality can be reliably detected.

However, if the threshold value is lowered, when the current value is increased due to the individual difference of the workpiece, even if no abnormality occurs in the grinding process, measures such as reducing the grinding feed rate may be implemented. As a result, the processing speed becomes slower and the processing efficiency decreases. In addition, if the processing speed is reduced, the self-grinding edge of the grinding vermiculite is not promoted, and the grinding ability of the grinding vermiculite is reduced, but the machining load may be increased.

The present invention has been developed by the present invention in view of such problems, and an object thereof is to provide a grinding device capable of performing grinding processing under appropriate processing conditions. (Means for solving problems)

According to one aspect of the present invention, there is provided a grinding device for grinding a workpiece, which includes: a suction cup table having a holding surface on the upper surface, and holding the workpiece on the holding surface and rotating around the axis; The shaft system is along a direction perpendicular to the holding surface; Grinding unit includes a main shaft and a grinding vermiculite which is installed below the main shaft and rotates in accordance with the rotation of the main shaft. The grinding vermiculite is used for grinding. The workpiece to be held on the chuck table; a grinding feed unit, which grinds the grinding unit toward the holding surface; an AE sensor, which is mounted on the grinding unit or the grinding feed unit And a control unit that controls the grinding feed unit, the chuck table, and the AE sensor, and 控制 the control unit, when the workpiece being held on the chuck table is ground, the chuck table and the The grinding vermiculite is rotated, and the grinding unit is ground and fed by the grinding feed unit, so that the grinding vermiculite is brought into contact with the object to be processed. The rotation speed of the chuck table, the rotation speed of the grinding vermiculite, or the grinding feed unit of the grinding feed unit is controlled by the grinding wave generated by the grinding and by the elastic wave detected by the AE sensor. speed. [Effect of the invention]

During the grinding process of the workpiece, an elastic wave corresponding to the content of the grinding process is generated from the workpiece or the grinding vermiculite. A grinding device according to an aspect of the present invention, for example, an AE (Acoustic Emission) sensor is installed in the grinding unit or the grinding feed unit, and the AE sensor can be used to detect the propagation of the AE sensor. The grinding wave of the grinding unit or the grinding feed unit.

For example, the elastic wave generated by the grinding process tends to increase the amplitude when the processing load applied to the workpiece is large, while the amplitude tends to decrease when the processing load is small. Therefore, in the grinding apparatus according to an aspect of the present invention, during the grinding process, the AE sensor detects the elastic wave and grasps the state of the grinding process.

Then, when the elastic wave having a large amplitude exceeding the allowable range is detected by the AE sensor, for example, the rotation speed of the suction table or grinding vermiculite is increased, and the grinding amount per rotation of the suction table or grinding vermiculite is reduced. Or, slow down the grinding feed rate of the grinding unit of the grinding feed unit. When an elastic wave with a small amplitude lower than the allowable range is detected, the rotation speed of the suction table or the grinding vermiculite is slowed down, or the grinding feed speed of the grinding unit of the grinding feed unit is increased.

In this way, the state of the grinding process is grasped from the elastic wave observed by the AE sensor, and the suction table, the grinding unit, or the grinding feed unit is controlled in accordance with the state of the grinding process, whereby the grinding process can be appropriately performed.

Therefore, according to one aspect of the present invention, a grinding device capable of performing grinding processing under appropriate machining conditions is provided.

An embodiment according to an aspect of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view schematically showing a configuration example of a grinding device 2 according to this embodiment.

As shown in FIG. 1, on the substantially rectangular parallelepiped-shaped base 4 of the grinding device 2, a disc-shaped turntable 6 is provided to be rotatable in a horizontal plane. On the upper surface of the turntable 6, three suction cup tables 8 are provided, which are separated by 120 degrees in the circumferential direction. The turntable 6 functions as a chuck table positioning unit, and positions each chuck table 8 in a work-in / out area, a first processing area, or a second processing area. For example, rough grinding of coarse grains is performed in the first processing area, and fine grinding of fine grains is performed in the second processing area.

The chuck table 8 has a suction path (not shown) connected at one end to a suction source (not shown) inside, and the other end of the chuck path leads to a porous member constituting the holding surface 8 a on the chuck table 8. The chuck table 8 causes the negative pressure generated by the suction source to pass through the porous member to act on the object to be carried on the holding surface 8a, thereby attracting and holding the object to be processed.

Adjacent to the rear of the turntable 6, two columnar columns 12a, 12b are erected. The column 12a is provided with a grinding unit 10a. The column 12b is provided with a grinding unit 10b. Each of the grinding units 10a and 10b includes: spindle motors 14a and 14b; grinding wheels 16a and 16b that are driven to rotate by the spindle motors 14a and 14b; .

The grinding vermiculite 18a, 18b mounted on the grinding wheels 16a, 16b can be moved in the vertical direction (Z-axis direction) by the grinding feed units 20a, 20b, and the workpiece to be held on the suction table 8 is ground. machining.

The workpiece to be processed in the grinding device 2 is, for example, a substantially disc-shaped substrate formed of a material such as silicon, SiC (silicon carbide), or another semiconductor, or a material such as sapphire, glass, or quartz. The surface of the workpiece is divided into a plurality of areas by a plurality of predetermined division lines (segmentation lanes) arranged in a grid shape. Devices are formed in each area divided by the plurality of predetermined division lines. .

The workpiece is thinned by grinding the back surface. For example, rough grinding is performed by the grinding unit 10a, and fine grinding is performed by the grinding unit 10b. The machined object to be ground is finally divided along the predetermined dividing line, thereby forming each device wafer.

On the front side of the base table 4, there are box mounting tables 22a and 22b. On the cassette mounting table 22a, for example, a cassette 24a for storing a workpiece before processing is placed. The cassette mounting table 22b is, for example, a cassette 24b for storing a processed object.

The base 4 is provided with a workpiece conveying robot 26 that is adjacent to the cassette mounting tables 22 a and 22 b and conveys the workpiece. The front part of the base 4 is further equipped with: 定位 a positioning table 28 which determines the position of the workpiece by a plurality of positioning pins; (2) a processed object unloading mechanism (unloading arm) 32 that unloads a processed object from the suction table 8; and a spinner cleaning device 34 that cleans and spin-dries the processed object.

When a grinding process is performed on the workpiece sucked and held on the holding surface 8a of the chuck table 8, a processing load is applied to the workpiece or the grinding vermiculite. If the processing load is too large, breakage or chipping of the workpiece may occur, and abnormal consumption of grinding vermiculite may occur. In addition, if the countermeasures above are necessary to reduce the processing load, the time required for the grinding process will increase, the machining efficiency will deteriorate, and the self-grinding edge of the grinding vermiculite may not be appropriately generated.

Therefore, an AE (Acoustic Emission) sensor 36 is provided in the grinding device 2 of the present embodiment. This AE sensor 36 is, for example, as shown in FIG. 1, and is attached to at least one of the chuck table 8, the grinding units 10 a and 10 b, and the grinding feed units 20 a and 20 b.

The AE sensor 36 is a sensor that detects the elastic energy that is generated when the object is deformed or destroyed, and generates elastic waves. When the AE sensor 36 is provided in the grinding device 2, it is possible to detect elastic waves (vibrations) emitted and transmitted from each component of the grinding device 2. For example, the AE sensor 36 can detect an elastic wave generated during the grinding process of the workpiece by the grinding unit of the grinding device 2.

The elastic wave generated by the grinding process tends to increase the amplitude when the processing load applied to the workpiece is large, while the amplitude tends to decrease when the processing load is small. Therefore, during the grinding process, if the elastic wave propagating through the grinding device 2 is detected by the AE sensor 36, the state of the grinding process can be grasped.

Then, for example, when the processing load is excessive, the rotation speed of the chuck table or the grinding vermiculite is increased, or the grinding feed speed of the grinding unit of the grinding feed unit is slowed down. When the processing load is too small, the rotation speed of the chuck table or the grinding vermiculite is slowed down, or the grinding feed rate of the grinding unit of the grinding feed unit is increased. In this way, grinding processing can be appropriately performed.

Here, the structure of the AE sensor 36 will be described. FIG. 2 (A) is a perspective view schematically showing the structure of the AE sensor 36, and FIG. 2 (B) is a cross-sectional view schematically showing the structure of the AE sensor 36. As shown in FIG. 2 (A), the AE sensor 36 is, for example, a cylindrical shape having a closed upper portion, and has a frame 36a made of stainless steel. An opening (not shown) is provided on the side of the frame 36a, and the coaxial cable 36b is connected to the inside of the frame 36a through the opening. The coaxial cable 36b is, for example, electrically connected to a control unit 38 described later.

As shown in FIG. 2 (B), a vibrator 36g is provided inside the housing 36a. One of the inner conductor and the outer conductor of the coaxial cable 36b is a negative electrode 36c connected to the vibrator 36g, and the other is The positive electrode 36d is connected to the vibrator 36g. A gap inside the frame body 36a is filled with a sealing resin 36e. The lower part of the vibrator 36g is in contact with an insulating material 36f made of ceramics or the like arranged to block the bottom of the frame 36a.

The AE sensor 36 is arranged so that the insulating material 36f contacts the grinding device 2. The elastic wave (vibration) to be detected is transmitted to the vibrator 36g through the insulating material 36f. The elastic wave (vibration) reaching the vibrator 36g is an electrical signal converted by the vibrator 36g into a voltage corresponding to the elastic wave (vibration). The electrical signal is transmitted to the control unit 38 described below through the coaxial cable 36b.

The grinding device 2 is further provided with a control unit 38 for controlling each component of the grinding device 2. The control unit 38 controls the grinding process of the grinding device 2 and controls the measurement of the elastic wave of the AE sensor 36. Then, the measurement results obtained by the measurement by the AE sensor 36 are reflected, and the operations of the grinding feed units 20a, 20b, the grinding units 10a, 10b, and the chuck table 8 are corrected.

Next, a description will be given of the grinding process of the workpiece performed in the grinding device 2, the measurement of the elastic wave of the AE sensor 36, and the correction of the processing conditions reflecting the results of the measurement.

First, the cassette 24a containing the object to be processed is placed on the cassette mounting table 22a. Then, the processed object transfer robot 26 is operated to carry out the processed object stored in the box 24a from the box 24a. The object to be processed is placed on the positioning table 28, and each pin of the positioning table 28 is actuated to precisely position the object to be processed at the center of the positioning table 28.

Next, the workpiece loading mechanism (loading arm) 30 is operated, and the workpiece is placed on the chuck table 8 positioned in the loading / unloading area. At this time, the processing surface side of the processing object is exposed upward. Then, the workpiece is sucked and held on the chuck table 8, and the turntable 6 is rotated to position the chuck table 8 in the first processing area, that is, below the grinding unit 10 a.

Next, the spindle motor 14a of the grinding unit 10a is operated to rotate the grinding wheel 16a. Then, the chuck table 8 is rotated around an axis which is in a direction perpendicular to the holding surface 8a. Then, the grinding feed unit 20a is operated, and the grinding wheel 16a is lowered toward the workpiece. When the grinding vermiculite 18a mounted on the grinding wheel 16a comes into contact with the work surface of the work, the work is ground. The grinding feed unit 20a lowers the grinding vermiculite 18a to a predetermined height position, whereby the workpiece can be thinned to a predetermined thickness.

The grinding process may be performed using the grinding unit 10b. It is also possible to simultaneously grind and process the object held on the chuck table 8 positioned in the first processing area (below the grinding unit 10a) and the chuck positioned in the second processing area (below the grinding unit 10b). The workpiece to be held on the table 8. For example, rough grinding may be performed in the first processing area, and fine grinding may be performed in the second processing area.

After the grinding process is performed, the chuck table 8 is repositioned to the area where the workpiece is carried in and out, the workpiece carrying mechanism (unloading arm) 32 is operated, and the workpiece is transferred from the chuck table 8 to the spinner cleaning device 34. At this time, the sucker table 8 is released from being sucked and held by the workpiece.

Next, the rotator washing device 34 is operated to wash and dry the workpiece, and the workpiece transfer robot 26 is operated to store the workpiece in the box 24b placed on the box mounting table 22b.

During the grinding process, the AE sensor 36 mounted on the grinding apparatus 2 is allowed to observe the elastic wave. During the grinding process of the workpiece, an elastic wave corresponding to the content of the grinding process is generated from the workpiece to be ground by grinding the vermiculite 18a, 18b or the grinding vermiculite 18a, 18b. The AE sensor 36 can detect elastic waves propagating through the grinding units 10a, 10b or the grinding feed units 20a, 20b, etc., on which the AE sensor 36 is installed.

Examples of the waveform of the elastic wave observed by the AE sensor 36 are shown in FIGS. 3 (A) and 3 (B). In each figure, the waveform of the elastic wave observed by the AE sensor 36 and the change in the height position of the grinding unit are displayed. The horizontal axis of the graph represents time, and the vertical axis represents the voltage of the electrical signal output by the AE sensor 36 that has detected the elastic wave and the height of the grinding unit.

FIG. 3 (A) shows an example of the relationship between the height position of the grinding unit and the elastic wave measured by the AE sensor when the height is higher than the allowable range of the amplitude of the elastic wave measured by the AE sensor. FIG. 3 (B) is a diagram showing a case where the amplitude is lower than the allowable range of the amplitude of the elastic wave measured by the AE sensor.

The elastic wave observed by the AE sensor 36 has a predetermined allowable range for its amplitude. For example, in the graphs shown in FIG. 3 (A) and FIG. 3 (B), the allowable range as the amplitude of the elastic wave is the upper limit of the allowable range of the amplitude of the elastic wave shown by symbol 44a and 44b. The range between the lower limit of the allowable range of the amplitude of the elastic wave.

For example, as shown in FIG. 3 (A), when the amplitude of the elastic wave 42a observed by the AE sensor 36 becomes large, and the amplitude exceeds the upper limit 44a of the elastic wave amplitude allowable range, it is suggested that an amplitude exceeding the allowable range is generated. Grinding load. If the grinding process is continued as it is, breakage or chipping of the workpiece may occur, and abnormal consumption of the grinding vermiculite 18a, 18b may occur.

When such an elastic wave 42a is observed, the control unit 38 reduces the grinding feed rate of the grinding units 10a, 10b of the grinding feed units 20a, 20b, for example. In this way, as shown in FIG. 3 (A), after the timing 46a of changing the grinding feed rate, the amplitude of the elastic wave observed by the AE sensor 36 becomes small, and it is confirmed that the processing load is reduced.

On the other hand, as shown in FIG. 3 (B), when the amplitude of the elastic wave 42b observed by the AE sensor 36 becomes smaller and becomes lower than the lower limit 44b of the allowable range of the elastic wave amplitude, it is suggested that The grinding load applied to the workpiece is too small. In this case, the grinding load may be too small, and the self-sharpening edges of the grinding vermiculite 18a and 18b may not progress properly. In addition, there is room for increasing the grinding feed rate to improve machining efficiency.

When such an elastic wave 42b is observed, the control unit 38 increases the grinding feed rate of the grinding units 10a, 10b of the grinding feed units 20a, 20b, for example. In this way, as shown in FIG. 3 (B), after the timing 46b for changing the grinding feed rate, the processing load applied to the workpiece becomes appropriate, and the amplitude of the elastic wave observed by the AE sensor 36 becomes large. . The self-sharpening edges of the grinding vermiculite 18a, 18b also progress appropriately.

As described above, since the grinding device 2 of the present embodiment is provided with the AE sensor 36, it is possible to monitor the processing load applied to the workpiece or the like by the grinding process. Therefore, breakage and the like of the workpiece and ground vermiculite are unlikely to occur, and the processing efficiency can be appropriately maintained. Here, the grinding device 2 of this embodiment is not only the grinding feed speed of the grinding feed units 20a, 20b, but also the rotation speed of the chuck table 8 or the elastic wave detected by the AE sensor 36. Grind the rotation speed of vermiculite 18a, 18b.

In addition, this invention is not limited to the description of the said embodiment, Various changes are possible. For example, in the above-mentioned embodiment, the elastic wave is observed by the AE sensor 36 during the grinding processing of the workpiece by the grinding units 10a and 10b, but the processing measures of one aspect of the present invention are not limited to this.

For example, when the workpiece is not ground by the grinding device 2, the AE sensor 36 may be operated to observe the elastic wave. For example, at a timing such as the maintenance of the grinding device 2, the grinding wheels 16 a and 16 b or the chuck table 8 may be rotated to observe the elastic wave generated from the grinding device 2.

For example, the control unit 38 memorizes the elastic wave observed by the AE sensor 36 when the grinding wheels 16a, 16b or the sucker table 8 is operating normally, and compares the waveform of the elastic wave observed during maintenance. In this way, the abnormality of the grinding wheels 16a, 16b or the chuck table 8 can be detected.

In addition, the structure, method, and the like of the above-mentioned embodiment can be appropriately changed and implemented without departing from the scope of the object of the present invention.

2‧‧‧ Grinding device

4‧‧‧ abutment

6‧‧‧ turntable

8‧‧‧ Suction table

8a‧‧‧ keep face

10a, 10b ‧‧‧ grinding unit

12a, 12b

14a, 14b‧‧‧ spindle motor

16a, 16b ‧ ‧ grinding wheels

18a, 18b ‧‧‧ grinding vermiculite

20a, 20b ‧‧‧ grinding feed unit

22a, 22b ‧‧‧ box mounting table

24a, 24b ‧‧‧ boxes

26‧‧‧ Automatic object transfer machine

28‧‧‧ positioning table

30‧‧‧ Object moving mechanism (loading arm)

32‧‧‧ Workpiece removal mechanism (unloading arm)

34‧‧‧Rotator cleaning device

36‧‧‧AE Sensor

36a‧‧‧Frame

36b‧‧‧ coaxial cable

36c‧‧‧Negative electrode

36d‧‧‧Positive electrode

36e‧‧‧sealing resin

36f‧‧‧Insulation

36g‧‧‧Vibrator

38‧‧‧Control unit

40a, 40b ‧‧‧ height of grinding unit

42a, 42b‧‧‧ Elastic Wave

44a‧‧‧ Upper limit of the allowable range of the amplitude of the elastic wave

44b‧‧‧ Lower limit of the allowable range of the amplitude of the elastic wave

46a, 46b ‧‧‧ Timing of change in grinding feed rate

FIG. 1 is a perspective view schematically showing a configuration example of a grinding device. FIG. 2 (A) is a perspective view schematically showing the structure of the AE sensor, and FIG. 2 (B) is a cross-sectional view schematically showing the structure of the AE sensor. FIG. 3 (A) shows an example of the relationship between the height position of the grinding unit and the elastic wave measured by the AE sensor when the height is higher than the allowable range of the amplitude of the elastic wave measured by the AE sensor. FIG. 3 (B) is a diagram showing a case where the amplitude is lower than the allowable range of the amplitude of the elastic wave measured by the AE sensor.

Claims (1)

A grinding device is used for grinding an object to be processed, and is characterized in that: (1) a chuck table having a holding surface on the upper surface, holding the object to be held on the holding surface, and rotating around an axis; The vertical direction of the surface; Grinding unit includes a main shaft and a grinding vermiculite which is installed below the main shaft and rotates in accordance with the rotation of the main shaft. The grinding vermiculite is used to grind the workpiece held on the suction table. A grinding feed unit, which grinds the grinding unit toward the holding surface; an AE sensor, which is installed in the grinding unit or the grinding feed unit; and a control unit, which controls the The grinding feed unit, the chuck stage and the AE sensor, and the control unit rotates the chuck stage and the spindle during grinding of the workpiece held by the chuck stage, and the grinding feed Unit to make the grinding unit grinding feed, and to bring the grinding vermiculite into contact with the workpiece, according to the AE generated by the grinding and by the AE sense The elastic wave detected by the measuring device controls the rotation speed of the chuck table, the rotation speed of the grinding vermiculite, or the speed at which the grinding feed unit grinds the grinding unit.