JP2019018326A - Grinding device - Google Patents

Abstract

An object of the present invention is to provide a grinding device capable of performing a grinding process under appropriate processing conditions. A grinding table is provided with a chuck table, a spindle, and a grinding wheel mounted below the spindle and rotated with rotation of the spindle, and a workpiece held on the chuck table is ground by the grinding wheel. A grinding unit, a grinding feed unit for grinding and feeding the grinding unit toward the holding surface, an AE sensor mounted on the grinding unit or the grinding feed unit, and a control unit. When the workpiece is ground, the chuck table and the grinding wheel are rotated, and the grinding unit is ground and fed by the grinding feed unit to bring the grinding wheel into contact with the workpiece. The rotation speed of the chuck table, the rotation speed of the grinding wheel, or the feed speed of the grinding wheel depends on the generated elastic wave detected by the AE sensor. Tsu door to control the rate at which the grinding feed the the grinding unit. [Selection diagram] FIG.

Description

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

  In the process of forming device chips including semiconductor devices and optical devices from plate-like workpieces made of silicon, gallium arsenide, sapphire, glass, etc., the plate-like workpiece is ground and thinned to a predetermined thickness A grinding device is used. The grinding apparatus includes a chuck table for holding the plate-like workpiece, a grinding unit for grinding the workpiece, and a grinding feed unit for grinding and feeding the grinding unit in the vertical direction.

  The grinding unit includes a spindle extending along the vertical direction, a grinding wheel attached to the lower end of the spindle, and a grinding wheel attached to the lower surface of the grinding wheel. When grinding the workpiece, the spindle is rotated to rotate the grinding wheel, and the grinding feed unit is operated to feed the grinding unit by grinding. When the grinding wheel mounted on the rotating grinding wheel comes into contact with the workpiece, grinding of the workpiece is started.

  During grinding, a work load (hereinafter referred to as a work load) is applied to the workpiece and the grinding unit. If a work load exceeding the allowable range is applied to the work piece or the grinding unit, the work piece may be damaged or chipped, or the grinding wheel may be abnormally worn, and normal grinding may not be performed. Therefore, in order to suppress the occurrence of such a problem, a technique for detecting an abnormality in the machining load has been developed (see Patent Document 1).

  In this technique, a current value of a motor that rotates a spindle is measured during grinding of a workpiece. The current value reflects the processing load caused by grinding. Then, it is determined that the machining load is abnormal when the current value exceeds a predetermined threshold value. When an abnormality in the machining load is detected, for example, by taking measures such as slowing down the grinding feed speed of the grinding unit and slowing down the rotation speed of the grinding wheel and chuck table, the machining load can be reduced.

JP 2012-161861 A

  However, the current value of the motor that rotates the spindle may change due to minute individual differences in the workpiece. For example, the current value may be observed to be low even in a situation where an abnormality occurs in the grinding process. Therefore, the threshold value may be set low so that the occurrence of abnormality can be detected reliably.

  However, when the threshold value is lowered, when the current value increases due to individual differences of workpieces, measures such as reducing the grinding feed speed may be implemented even if there is no abnormality in grinding. . Then, the processing speed is slowed down and the processing efficiency is lowered. Further, when the processing speed is reduced, the self-generated blade of the grinding wheel is not promoted, and the grinding ability of the grinding wheel is lowered, which may cause an increase in processing load.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a grinding apparatus capable of performing grinding under appropriate processing conditions.

  According to one aspect of the present invention, a chuck table having a holding surface on an upper surface, holding a workpiece on the holding surface, and rotating about an axis along a direction perpendicular to the holding surface, and a spindle A grinding wheel mounted below the spindle and rotating in accordance with the rotation of the spindle, and a grinding unit for grinding the workpiece held on the chuck table with the grinding wheel, and the grinding unit Control for controlling the grinding feed unit that feeds the grinding toward the holding surface, the grinding unit or the AE sensor mounted on the grinding feed unit, the grinding feed unit, the chuck table, and the AE sensor And a control unit that rotates the chuck table and the grinding wheel during grinding of the work piece held on the chuck table to rotate the grinding feed unit. The grinding unit is fed by grinding to bring the grinding wheel into contact with the workpiece, and the rotation speed of the chuck table and the rotation speed of the grinding wheel according to the elastic wave generated by the grinding and detected by the AE sensor Alternatively, there is provided a grinding apparatus for grinding the workpiece, wherein the grinding feed unit controls a speed at which the grinding unit is fed by grinding.

  When grinding a workpiece, elastic waves corresponding to the content of the grinding process are generated from the workpiece and the grinding wheel. In the grinding apparatus according to one aspect of the present invention, for example, an AE (Acoustic Emission) sensor is attached to the grinding unit or the grinding feed unit, and the grinding unit or the grinding feed unit to which the AE sensor is attached is attached. The propagating elastic wave can be detected by the AE sensor.

  For example, the elastic wave generated by grinding tends to increase in 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 one aspect of the present invention, the state of the grinding process is grasped by detecting the elastic wave with an AE sensor during the grinding process.

  When an elastic wave having a large amplitude exceeding the allowable range is detected by the AE sensor, for example, the rotation speed of the chuck table or the grinding wheel is increased to reduce the grinding amount per rotation of the chuck table or the grinding wheel. Alternatively, the grinding feed speed of the grinding unit by the grinding feed unit is decreased. When an elastic wave having a small amplitude lower than the allowable range is detected, the rotation speed of the chuck table or the grinding wheel is decreased, or the grinding feed speed of the grinding unit by the grinding feed unit is increased.

  In this way, grasping the state of the grinding process from the elastic wave observed by the AE sensor, and controlling the chuck table, the grinding unit, or the grinding feed unit according to the state of the grinding process, the grinding process is appropriately performed. Can be implemented.

  Therefore, according to one embodiment of the present invention, a grinding apparatus that can perform grinding under appropriate machining conditions is provided.

It is a perspective view which shows the structural example of a grinding apparatus typically. FIG. 2A is a perspective view schematically showing the structure of the AE sensor, and FIG. 2B is a cross-sectional view schematically showing the structure of the AE sensor. FIG. 3A 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 amplitude of the elastic wave measured by the AE sensor exceeds the allowable range. FIG. 3B is a diagram illustrating a case where the amplitude of the elastic wave measured by the AE sensor falls below an allowable range.

  Embodiments according to one aspect of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a perspective view schematically showing a configuration example of a grinding apparatus 2 according to the present embodiment.

  As shown in FIG. 1, a disc-shaped turntable 6 is provided on a substantially rectangular parallelepiped base 4 of the grinding device 2 so as to be rotatable in a horizontal plane. Three chuck tables 8 are provided on the upper surface of the turntable 6 so as to be 120 degrees apart in the circumferential direction. The turntable 6 functions as a chuck table positioning unit, and positions each chuck table 8 in a workpiece loading / unloading region, a first processing region, or a second processing region. For example, rough grinding with coarse abrasive grains is performed in the first processing area, and finish grinding with fine abrasive grains is performed in the second grinding area.

  The chuck table 8 has a suction path (not shown) with one end connected to a suction source (not shown) inside, and the other end of the suction path forms a holding surface 8 a on the chuck table 8. Leads to. The chuck table 8 sucks and holds the workpiece by causing a negative pressure generated by the suction source to act on the workpiece placed on the holding surface 8a through the porous member.

  Two columnar columns 12 a and 12 b are provided upright at positions adjacent to the rear of the turntable 6. 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 a spindle motor 14a and 14b, a grinding wheel 16a and 16b rotated by the spindle motor 14a and 14b, and a grinding wheel 18a and 18b mounted on the grinding wheel 16a and 16b. It has.

  The grinding wheels 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 grind the work piece held on the chuck table 8. Process.

  The workpiece to be processed in the grinding apparatus 2 is, for example, a substantially disk-shaped substrate made of silicon, SiC (silicon carbide), or other semiconductor material, or a material such as sapphire, glass, or quartz. It is. The surface of the workpiece is divided into a plurality of regions by a plurality of division lines (streets) arranged in a grid pattern, and devices such as ICs are formed in the regions divided by the plurality of division lines. Has been.

  The workpiece is thinned by grinding the back surface. For example, rough grinding is performed by the grinding unit 10a, and finish grinding is performed by the grinding unit 10b. The ground workpiece is finally divided along the division lines, whereby individual device chips are formed.

  Cassette mounting tables 22 a and 22 b are provided on the front side of the base 4. On the cassette mounting table 22a, for example, a cassette 24a that accommodates a workpiece to be processed is placed. On the cassette mounting table 22b, for example, a cassette 24b for storing a processed workpiece is placed.

  On the base 4, a workpiece transfer robot 26 that transfers a workpiece adjacent to the cassette mounting tables 22 a and 22 b is installed. The front portion of the base 4 further includes a positioning table 28 for determining the position of the workpiece with a plurality of positioning pins, a workpiece loading mechanism (loading arm) 30 for placing the workpiece on the chuck table 8, and a workpiece. A workpiece unloading mechanism (unloading arm) 32 for unloading the workpiece from the chuck table 8 and a spinner cleaning device 34 for cleaning and spin drying the ground workpiece.

  When the workpiece that is sucked and held on the holding surface 8a of the chuck table 8 is ground, a processing load is applied to the workpiece and the grinding wheel. If the processing load is too large, the workpiece may be damaged or chipped, and the grinding wheel may be abnormally consumed. In addition, if more than necessary measures are taken in order to reduce the processing load, the time required for grinding increases, the processing efficiency deteriorates, and the self-generated blade of the grinding wheel may not be appropriately generated.

  Therefore, an AE (Acoustic Emission) sensor 36 is installed in the grinding apparatus 2 according to the present embodiment. For example, as shown in FIG. 1, the AE sensor 36 is installed at at least one of the chuck table 8, the grinding units 10a and 10b, the grinding feed units 20a and 20b, and the like.

  The AE sensor 36 is a sensor that detects an elastic wave generated by releasing elastic energy stored in the object when the object is deformed or destroyed. When the AE sensor 36 is installed in the grinding apparatus 2, it is possible to detect elastic waves (vibrations) emitted and propagated from the components of the grinding apparatus 2. For example, the AE sensor 36 can detect an elastic wave generated when the workpiece is ground by the grinding unit of the grinding apparatus 2.

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

  For example, when the processing load is too large, the rotation speed of the chuck table or the grinding wheel is increased, or the grinding feed speed of the grinding unit by the grinding feed unit is decreased. When the processing load is too small, the rotation speed of the chuck table and the grinding wheel is decreased, or the grinding feed speed of the grinding unit by the grinding feed unit is increased. Then, grinding can be performed appropriately.

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

  As shown in FIG. 2B, the housing 36a is provided with a vibrator 36g, and one of the inner conductor and the outer conductor of the coaxial cable 36b is connected to the negative electrode 36c of the vibrator 36g. The other is connected to the plus electrode 36d on the upper surface of the vibrator 36g. A sealing resin 36e is filled in a gap inside the housing 36a. The lower part of the vibrator 36g is in contact with an insulating material 36f made of ceramics or the like disposed so as to close the bottom of the housing 36a.

  The AE sensor 36 is installed so that the insulating material 36f is in contact with the grinding device 2, and an elastic wave (vibration) to be detected propagates to the vibrator 36g via the insulating material 36f. The elastic wave (vibration) reaching the vibrator 36g is converted into an electric signal having a voltage corresponding to the elastic wave (vibration) by the vibrator 36g. The electrical signal is transmitted to the control unit 38 described below through the coaxial cable 36b.

  The grinding apparatus 2 further includes a control unit 38 for controlling each component of the grinding apparatus 2. The control unit 38 controls grinding processing in the grinding apparatus 2 and controls measurement of elastic waves by the AE sensor 36. The operations of the grinding feed units 20a and 20b, the grinding units 10a and 10b, and the chuck table 8 are corrected by reflecting the measurement result obtained by the measurement by the AE sensor 36.

  Next, the grinding of the workpiece performed in the grinding apparatus 2, the measurement of the elastic wave by the AE sensor 36, and the correction of the processing conditions reflecting the measurement result will be described.

  First, the cassette 22a containing the workpiece is placed on the cassette mounting table 24a. Then, the workpiece conveying robot 26 is operated to carry out the workpiece accommodated in the cassette 22a from the cassette 22a. The unloaded workpiece is placed on the positioning table 28, and each pin of the positioning table 28 is operated to precisely position the workpiece in the center of the positioning table 28.

  Next, the workpiece loading mechanism (loading arm) 30 is operated to place the workpiece on the chuck table 8 positioned in the loading / unloading area. At this time, the processing surface side of the workpiece 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 below the first machining area, that is, below the grinding unit 10a.

  Next, the spindle motor 14a of the grinding unit 10a is operated to rotate the grinding wheel 16a. Further, the chuck table 8 is rotated around an axis along a direction perpendicular to the holding surface 8a. Then, the grinding feed unit 20a is operated to lower the grinding wheel 16a toward the work piece. When the grinding wheel 18a mounted on the grinding wheel 16a touches the workpiece surface of the workpiece, the workpiece is ground. The workpiece can be thinned to a predetermined thickness by lowering the grinding wheel 18a to a predetermined height position by the grinding feed unit 20a.

  In addition, you may implement a grinding process using the grinding unit 10b. On the workpiece held on the chuck table 8 positioned in the first processing region (below the grinding unit 10a) and on the chuck table 8 positioned in the second processing region (below the grinding unit 10b) The held workpiece may be ground simultaneously. Further, for example, rough grinding may be performed in the first processing region, and then finish grinding may be performed in the second processing region.

  After carrying out the grinding process, the chuck table 8 is positioned again in the workpiece loading / unloading area, the workpiece unloading mechanism (unloading arm) 32 is operated, and the workpiece is removed from the chuck table 8 by the spinner cleaning. Transport to device 34. At this time, the chuck table 8 releases the suction holding of the workpiece.

  Next, the workpiece cleaning robot 34 is operated to clean and dry the workpiece, and the workpiece transfer robot 26 is operated to store the workpiece in the cassette 24b mounted on the cassette mounting table 22b. To do.

  While performing the grinding process, the AE sensor 36 attached to the grinding device 2 is caused to observe the elastic wave. At the time of grinding of the workpiece, an elastic wave corresponding to the content of the grinding process is generated from the workpiece to be ground by the grinding wheels 18a and 18b and the grinding wheels 18a and 18b. The AE sensor 36 can detect elastic waves propagating to the grinding units 10a and 10b or the grinding feed units 20a and 20b to which the AE sensor 36 is attached.

  3A and 3B show examples of the acoustic wave waveform observed by the AE sensor 36. FIG. Each figure shows the change in the height position of the grinding unit along with the waveform of the elastic wave observed by the AE sensor 36. The horizontal axis of the graph represents time, and the vertical axis represents the voltage of the electrical signal output from the AE sensor 36 that has detected the elastic wave and the height of the grinding unit.

  FIG. 3A 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 amplitude of the elastic wave measured by the AE sensor exceeds the allowable range. FIG. 3B is a diagram illustrating a case where the amplitude of the elastic wave measured by the AE sensor falls below an allowable range.

  A predetermined allowable range is set for the amplitude of the elastic wave observed by the AE sensor 36. For example, in the graphs shown in FIGS. 3A and 3B, the allowable range of the amplitude of the elastic wave is the upper limit of the allowable range of the elastic wave indicated by the symbol 44a and the elastic wave indicated by the symbol 44b. It is a range between the lower limit of the allowable range of the amplitude.

  For example, as shown in FIG. 3A, when the amplitude of the elastic wave 42a observed by the AE sensor 36 becomes large and exceeds the upper limit 44a of the elastic wave amplitude allowable range, grinding exceeding the allowable range is performed. This suggests that a load is occurring. If grinding is continued as it is, the workpiece may be damaged or chipped, and the grinding wheels 18a and 18b may be abnormally worn.

  When such an elastic wave 42a is observed, the control unit 38 decreases the grinding feed speed of the grinding units 10a and 10b by the grinding feed units 20a and 20b, for example. Then, as shown in FIG. 3A, after the timing 46a of changing the grinding feed rate, the amplitude of the elastic wave observed by the AE sensor 36 is reduced, and it is confirmed that the machining load can be reduced.

  On the other hand, as shown in FIG. 3B, when the amplitude of the elastic wave 42b observed by the AE sensor 36 becomes small and falls below the lower limit 44b of the allowable range of the elastic wave amplitude, This suggests that the grinding load is too small. In this case, there is a possibility that the grinding load is too small, and the self-generated blades of the grinding wheels 18a and 18b do not advance appropriately. In addition, there is room for increasing the grinding feed rate to increase the processing efficiency.

  When such an elastic wave 42b is observed, the control unit 38 increases the grinding feed speed of the grinding units 10a and 10b by the grinding feed units 20a and 20b, for example. Then, as shown in FIG. 3B, after the timing 46b of 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 increases. The self-generated blades of the grinding wheels 18a and 18b also proceed appropriately.

  As described above, since the grinding apparatus 2 according to the present embodiment includes the AE sensor 36, it is possible to monitor the processing load applied to the workpiece by grinding. Therefore, it becomes difficult to cause damage to the workpiece and the grinding wheel, and the processing efficiency can be appropriately maintained. Here, in the grinding apparatus 2 according to the present embodiment, in addition to the grinding feed speed of the grinding feed units 20a and 20b, the AE sensor 36 determines the rotational speed of the chuck table 8 or the grinding wheels 18a and 18b. You may control according to this elastic wave to detect.

  In addition, this invention is not limited to description of the said embodiment, A various change can be implemented. For example, in the above-described embodiment, the elastic wave is observed by the AE sensor 36 when the workpiece is ground by the grinding units 10a and 10b. However, the processing measure according to one embodiment of the present invention is not limited thereto.

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

  For example, the control unit 38 stores the elastic wave observed by the AE sensor 36 when the grinding wheels 16a, 16b and the chuck table 8 operate normally, and compares it with the waveform of the elastic wave observed during maintenance. Then, abnormality of the grinding wheels 16a and 16b and the chuck table 8 can be detected.

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

2 Grinding device 4 Base 6 Turntable 8 Chuck table 8a Holding surface 10a, 10b Grinding unit 12a, 12b Column 14a, 14b Spindle motor 16a, 16b Grinding wheel 18a, 18b Grinding wheel 20a, 20b Grind feed unit 22a, 22b Mounted on cassette Table 24a, 24b Cassette 26 Workpiece transfer robot 28 Positioning table 30 Workpiece loading mechanism (loading arm)
32 Workpiece unloading mechanism (unloading arm)
34 Spinner cleaning device 36 AE sensor 36a Housing 36b Coaxial cable 36c Negative electrode 36d Positive electrode 36e Sealing resin 36f Insulating material 36g Vibrator 38 Control unit 40a, 40b Grinding unit height 42a, 42b Elastic wave 44a Elastic wave amplitude Upper limit 44b Lower limit of elastic wave amplitude 46a, 46b Timing of change of grinding feed rate

Claims (1)

A chuck table having a holding surface on an upper surface, holding a workpiece on the holding surface, and rotating about an axis along a direction perpendicular to the holding surface;
A grinding unit equipped with a spindle and a grinding wheel mounted below the spindle and rotating as the spindle rotates, and grinding a workpiece held on the chuck table with the grinding wheel;
A grinding feed unit for grinding and feeding the grinding unit toward the holding surface;
An AE sensor mounted on the grinding unit or the grinding feed unit;
A control unit for controlling the grinding feed unit, the chuck table, and the AE sensor;
The control unit is
When grinding the workpiece held on the chuck table, the chuck table and the spindle are rotated, and the grinding unit is ground and fed by the grinding feed unit so that the grinding wheel contacts the workpiece. Let
Controlling the rotational speed of the chuck table, the rotational speed of the grinding wheel, or the speed at which the grinding feed unit grinds the grinding unit according to the elastic wave generated by the grinding and detected by the AE sensor. A grinding apparatus for grinding the workpiece.