JP7764296B2 - Wafer grinding method - Google Patents

Description

The present invention relates to a wafer grinding method.

In the wafer grinding method disclosed in Patent Document 1, electrodes made of Cu and Zn are embedded in resin on a wafer, and the resin is ground away with a grinding wheel to expose the electrodes on the grinding surface. In this grinding method, the wafer, whose electrodes are exposed on the grinding surface as a result of grinding, is then cleaned in a wafer cleaning unit. In this cleaning, a cleaning solution is used to remove metal chips from the grinding surface, which are generated when the electrodes are ground with the grinding wheel.

JP 2013-004910 A

In the above-described cleaning method, a cleaning solution such as citric acid water is used. A brush is also brought into contact with the surface to be ground. Next, pure water is sprayed onto the surface to be ground to remove the citric acid water. The wafer is then dried by rotating at high speed.

As a result, cleaning time can sometimes be longer than grinding time, causing the ground wafers to have to wait.

Therefore, the object of the present invention is to shorten the cleaning time for wafers whose electrodes have been exposed on their top surface due to grinding.

The wafer grinding method of the present invention (the present grinding method) is a wafer grinding method in which the underside of a wafer having a plurality of electrodes sealed with resin on its upper surface is held by the holding surface of a chuck table, and the upper surface of the wafer is ground with a rotating annular grinding wheel to expose the electrodes on the upper surface. The method includes a holding step in which the underside of the wafer, with the resin facing upward, is held by the holding surface; a grinding step in which the chuck table and the grinding wheel are brought closer together in a direction perpendicular to the holding surface, and pure water is supplied to the upper surface of the wafer while grinding the upper surface with the grinding wheel, thereby exposing the plurality of electrodes on the upper surface; and a first cleaning step in which the height of the grinding wheel is maintained for a predetermined time after the grinding step is completed, the supply of pure water is stopped, and water containing dissolved metal scraps is supplied to the upper surface to clean the upper surface.
The grinding method may include, after the first cleaning step, a second cleaning step of supplying water containing dissolved metal chips onto the upper surface to clean the upper surface until the grindstone is separated from the upper surface.
The grinding method may include a pure water washing step in which pure water is sprayed onto the wafer to remove water containing dissolved metal chips from the upper surface of the wafer.

In this grinding method, when the grinding process is completed, the height of the grinding wheel is maintained for a predetermined time, and a first cleaning process is carried out. The supply of pure water is stopped and water containing dissolved metal scraps is supplied to the top surface of the wafer to clean the top surface where the electrodes are exposed. This shortens the time required for cleaning compared to transporting the wafer to a cleaning device for cleaning.

Furthermore, since the first cleaning step is carried out while the grinding wheel is in contact with the upper surface, the grinding wheel can also be cleaned together with the upper surface.
Furthermore, the time from the completion of the grinding step to the start of the first cleaning step can be shortened, thereby improving the cleaning effect of the metal chip dissolved water.

FIG. 2 is an explanatory diagram showing a grinding process in the grinding device. 10 is a graph showing the change in height of the grinding wheel over time. FIG. 10 is an explanatory view showing a first cleaning step in the grinding apparatus.

The grinding apparatus 1 shown in Figure 1 includes a chuck table 20 that holds the wafer 100, a grinding mechanism 10 that grinds the wafer 100, a grinding feed mechanism 80 that feeds the grinding mechanism 10, and a control unit 7 that controls each component of the grinding apparatus 1.

The wafer 100 shown in Figure 1 is an example of a workpiece and is a circular semiconductor wafer. Multiple electrodes (not shown) are sealed with resin on the upper surface 101 of the wafer 100. The upper surface 101 of the wafer 100 is the grinding surface that will be subjected to the grinding process. As shown in Figure 1, a protective tape 105 is formed on the lower surface 102 of the wafer 100. The wafer 100 is held on the chuck table 20 via the protective tape 105.

The grinding mechanism 10 includes a spindle 11 extending along the Z-axis direction, a wheel mount 13 connected to the lower end of the spindle 11, and a grinding wheel 15 removably attached to the underside of the wheel mount 13.

The spindle 11 is driven by a spindle motor (not shown) and can rotate as indicated by arrow 501. The wheel mount 13 is formed in a disk shape and is fixed to the lower end of the spindle 11, rotating as the spindle 11 rotates. The wheel mount 13 supports the grinding wheel 15.

The grinding wheel 15 is formed to have approximately the same diameter as the wheel mount 13. The grinding wheel 15 includes an annular wheel base 16 made of a metal material. A plurality of grinding stones 17, each roughly rectangular parallelepiped, are arranged in a ring shape around the entire circumference of the underside of the wheel base 16. The grinding stones 17 are rotated by the rotation of the spindle 11, and grind the wafer 100 held on the holding surface 22 of the chuck table 20.

The grinding feed mechanism 80 moves the grinding mechanism 10 having this configuration along the Z-axis direction, which is the grinding feed direction.

The grinding machine 1 also has a processing water supply mechanism 70. The processing water supply mechanism 70 includes a processing water source 71 that is a source of processing water, a processing water channel 73 provided within the grinding mechanism 10, and processing water piping 75 that connects the processing water source 71 and the processing water channel 73. The processing water channel 73 is formed inside the spindle 11, the wheel mount 13, and the wheel base 16.
A processing water valve 72 is disposed in the processing water pipe 75. The processing water valve 72 is used to switch the communication state between the processing water source 71 and the processing water channel 73.

During grinding, the processing water supply mechanism 70 supplies processing water from the processing water source 71 to the processing water channel 73, causing the processing water to be sprayed onto the upper surface 101 of the wafer 100 being ground by the grinding wheel 17. In this embodiment, pure water is used as the processing water.

The chuck table 20 is a circular, plate-shaped table for holding the wafer 100. The chuck table 20 includes a circular, plate-shaped porous member 21 and a frame 23 that supports the porous member 21. The porous member 21 can be connected to a suction source 47. The suction force from the suction source 47 is transmitted to the holding surface 22, which is the upper surface of the porous member 21, allowing the chuck table 20 to suction-hold the wafer 100 using the holding surface 22.

The chuck table 20 can be rotated by a table rotation mechanism 30. The table rotation mechanism 30 is, for example, a pulley mechanism, and includes a motor 31 as a drive source, a driving pulley 32 attached to the shaft of the motor 31, a driven pulley 34 connected to the driving pulley 32 via an endless belt 33, and a rotating shaft 35 that supports the driven pulley 34.

The rotating shaft 35 is connected to the underside of the chuck table 20 directly below the center of the holding surface 22 and extends perpendicular to the holding surface 22 of the chuck table 20. When the motor 31 drives the driving pulley 32 to rotate, the endless belt 33 rotates in conjunction with the rotation of the driving pulley 32. The rotation of the endless belt 33 rotates the driven pulley 34 and the rotating shaft 35. This causes the chuck table 20 to rotate around the center of the holding surface 22 as indicated by arrow 503.

The grinding device 1 also includes a fluid flow mechanism 40. The fluid flow mechanism 40 is a mechanism for supplying a fluid such as air or water to the holding surface 22 of the chuck table 20, or for applying suction force to the holding surface 22.

The fluid flow mechanism 40 includes a suction groove 403, a suction flow path 470 connected to the suction groove 403, a rotary joint 460 connected to the rotary shaft 35, and a suction pipe 471 connected to the suction flow path 470.

The suction groove 403 is provided on the bottom surface of the recess in the frame 23 of the chuck table 20 so as to contact the underside of the porous member 21. The suction groove 403 is formed concentrically around the center of the chuck table 20.

The suction channel 470 extends from the bottom surface of the suction groove 403, passing through the frame 23, the rotary shaft 35, and the rotary joint 460.

The suction flow path 470 is connected to a suction pipe 471 outside the rotary joint 460. One end of the suction pipe 471 is connected to the suction flow path 470. The other end of the suction pipe 471 is connected to a suction source 47. This suction source 47 includes, for example, an ejector mechanism or a vacuum generator, and is connected to the porous member 21 of the chuck table 20 to apply suction force to the holding surface 22, which is the upper surface of the porous member 21.

The suction piping 471 is also provided with a suction on-off valve 475 and a suction flow rate adjuster 473, arranged in this order from the suction source 47 toward the suction flow path 470. The suction on-off valve 475 switches the communication state between the suction piping 471 and the suction source 47. The suction flow rate adjuster 473 is used to adjust the suction force transmitted from the suction source 47 to the holding surface 22 of the porous member 21.

Furthermore, an air pipe 481 is connected to the suction pipe 471. The air pipe 481 is a pipe that connects the holding surface 22 of the chuck table 20 with the air supply source 48.

One end of the air pipe 481 is connected to the suction flow path 470 via the suction pipe 471. The other end of the air pipe 481 is connected to the air supply source 48. The air supply source 48 includes a compressor or the like and is used to supply air to the holding surface 22 of the chuck table 20.

In addition, an air supply on-off valve 485 and an air adjustment unit 483 are arranged in this order on the air pipe 481 from the air supply source 48 toward the suction flow path 470. The air supply on-off valve 485 switches the communication state between the air pipe 481 and the air supply source 48. The air adjustment unit 483 is used to adjust the flow rate of air sent from the air supply source 48 to the holding surface 22.

The air pipe 481 is also connected to a water pipe 491. The water pipe 491 is a pipe that connects the holding surface 22 of the chuck table 20 to the water supply source 49.

One end of the water pipe 491 is connected to the suction flow path 470 via the air pipe 481 and the suction pipe 471. The other end of the water pipe 491 is connected to the water supply source 49. The water supply source 49 includes a pump or the like and is used to supply water to the holding surface 22 of the chuck table 20.

In addition, a water supply on-off valve 495 and a water adjustment unit 493 are arranged in the water piping 491, in that order, from the water supply source 49 toward the suction flow path 470. The water supply on-off valve 495 switches the communication state between the water piping 491 and the water supply source 49. The water adjustment unit 493 is used to adjust the flow rate of water sent from the water supply source 49 to the holding surface 22.

By supplying air and/or water to the holding surface 22 via these air pipes 481 and/or water pipes 491, it becomes easier to separate the wafer 100 held on the holding surface 22 from the holding surface 22.

The grinding machine 1 also has a cleaning mechanism 60. The cleaning mechanism 60 includes a cleaning water source 61, which is a source of cleaning water, a cleaning water nozzle 63 that sprays cleaning water, and a cleaning water pipe 65 that connects the cleaning water source 61 and the cleaning water nozzle 63. A cleaning water valve 67 is also provided on the cleaning water pipe 65. The cleaning water valve 67 is used to switch the communication state between the cleaning water source 61 and the cleaning water nozzle 63.

In the cleaning mechanism 60, cleaning water is supplied from the cleaning water source 61 to the cleaning water nozzle 63, which then supplies the cleaning water to the upper surface 101, which is the surface to be ground, of the wafer 100. In this embodiment, metal scrap dissolved water is used as the cleaning water. This metal scrap dissolved water is, for example, citric acid water.

The control unit 7 includes a CPU that performs calculations according to a control program, and storage media such as memory. The control unit 7 controls the above-mentioned components of the grinding apparatus 1 and performs overall control of each component of the grinding apparatus 1. For example, the control unit 7 controls the above-mentioned components of the grinding apparatus 1 to execute a wafer grinding method for grinding the wafer 100.

This wafer grinding method is described below. In this wafer grinding method, the lower surface 102 of a wafer 100, which has multiple electrodes sealed with resin on its upper surface 101, is held on the holding surface 22 of a chuck table 20, and the upper surface 101 of the wafer 100 is ground with a rotating annular grinding wheel 17 to expose the electrodes on the upper surface 101.

[Holding process]
Specifically, first, for example, an operator or a transfer device (not shown) places the wafer 100 on the holding surface 22 of the chuck table 20 with the lower surface 102 facing downward. Then, the control unit 7 controls the suction on-off valve 475 and the suction flow rate adjustment unit 473 to connect the suction source 47 to the holding surface 22. As a result, the lower surface 102 of the wafer 100 is held by the holding surface 22 so that the upper surface 101 of the wafer 100, including the resin and electrodes, faces upward. In this way, in the holding step, the lower surface 102 of the wafer 100 is held by the holding surface 22 with the resin facing upward.

[Grinding process]
Next, the control unit 7 brings the chuck table 20 and the grinding wheel 17 relatively closer together in a direction perpendicular to the holding surface 22 (Z-axis direction), and while supplying pure water as processing water to the upper surface 101 of the wafer 100, grinds the upper surface 101 with the grinding wheel 17, thereby exposing multiple electrodes on the upper surface 101.
In this embodiment, the control unit 7 uses the grinding feed mechanism 80 to move the grinding wheel 17 closer to the chuck table 20 in the Z-axis direction.

Specifically, the control unit 7 first positions the grinding wheel 17 at the origin height position, which is above the center of rotation of the wafer 100 held on the holding surface 22 of the chuck table 20 and at a height position where the bottom surface of the grinding wheel 17 does not come into contact with the wafer 100.
Furthermore, the control unit 7 rotates the grinding wheel 17 using a spindle motor (not shown), and also rotates the holding surface 22 of the chuck table 20 that holds the wafer 100 using a table rotation mechanism 30 .

At this time, the control unit 7 also opens the processing water valve 72 of the processing water supply mechanism 70, thereby starting the spraying of pure water L1 from the processing water channel 73 onto the upper surface 101 of the wafer 100, as shown in FIG. 1. The supply rate of pure water L1 is, for example, 3.0 L/min.

Next, the control unit 7 uses the grinding feed mechanism 80 to move the grinding wheel 17 of the grinding mechanism 10, which is at the origin height position, toward the chuck table 20 along the Z-axis direction.

2 shows the relationship between the height H of the grinding wheel 17 (height of the lower surface) and time t. As shown in Fig. 2, the control unit 7 first lowers the grinding mechanism 10 at a relatively high initial speed V1 so as to approach the chuck table 20 until the height of the grinding wheel 17 reaches a predetermined air-cut start height h1 (time range T1). The control unit 7 can detect the height of the grinding wheel 17 using, for example, an encoder (not shown) provided in the grinding feed mechanism 80.
FIG. 2 also shows the flow rates F (L/min) of the pure water L1 and the metal scrap dissolved water supplied to the upper surface 101 of the wafer 100.

Then, after the lower surface of the grinding wheel 17 reaches the predetermined air-cutting start height h1, the control unit 7 sets the speed at which the grinding mechanism 10 is lowered by the grinding feed mechanism 80 to an air-cutting speed V2, which is slower than the initial speed V1. The control unit 7 then causes the grinding mechanism 10 to approach the chuck table 20 at the air-cutting speed V2 by the grinding feed mechanism 80 (time range T2).

Then, after the lower surface of the grinding wheel 17 reaches a height h2 at which it contacts the upper surface 101 of the wafer 100, the control unit 7 grinds the upper surface 101 of the wafer 100 with the grinding wheel 17 at a first grinding speed V3 (time range T3; first grinding process). The first grinding speed V3 is slower than the initial speed V1 and is, for example, the same speed as the air-cut speed V2.

The control unit 7 also measures the thickness of the wafer 100 being ground, using a thickness measuring device (not shown) as appropriate. When the thickness of the wafer 100 approaches the target value, the control unit 7 uses the grinding feed mechanism 80 to move the grinding mechanism 10 toward the chuck table 20 at a second grinding speed V4, which is slower than the first grinding speed V3 (time range T4). In other words, the control unit 7 further slows the descent speed of the grinding mechanism 10 from the first grinding speed V3 to the second grinding speed V4, and continues the grinding process until the thickness of the wafer 100 reaches the target value (second grinding process). This second grinding process reduces the grinding marks that were left on the wafer 100 during the first grinding process.

In this way, in the grinding process, the upper surface 101 of the wafer 100 is ground by the grinding wheel 17 while pure water L1 is supplied as processing water to the upper surface 101. As a result, the resin on the upper surface 101 is removed by grinding, and a plurality of electrodes are exposed on the upper surface 101.
The supply of the pure water L1 is carried out continuously during the time range T1 to T4, for example, as indicated by the double-headed arrow 301 in FIG.

[First cleaning step]
After the thickness of the wafer 100 reaches the target value, the control unit 7 performs the first cleaning step. That is, the control unit 7 maintains the height of the grinding wheel 17 at the time when the grinding step is completed for a predetermined time, stops the supply of pure water L1 as the processing water, and supplies water containing dissolved metal scraps as cleaning water to the upper surface 101 of the wafer 100 to clean the upper surface 101.

Specifically, the control unit 7 performs so-called spark-out processing by stopping the lowering operation of the grinding mechanism 10 to approach the holding surface 22 of the chuck table 20 and maintaining the height of the grinding wheel 17 (time range T5). This spark-out processing removes grinding spots on the upper surface 101 of the wafer 100.

At this time, the control unit 7 also closes the processing water valve 72 of the processing water supply mechanism 70 to stop the supply of pure water L1 to the upper surface 101 of the wafer 100. Furthermore, as shown in FIG. 3, the control unit 7 opens the cleaning water valve 67 of the cleaning mechanism 60 to start the supply of metal scrap dissolved water L2 from the cleaning water nozzle 63 to the upper surface 101 of the wafer 100. The supply rate of metal scrap dissolved water L2 is, for example, 2.0 L/min.

As a result, the upper surface 101 of the wafer 100, including the exposed electrodes, and the grinding wheel 17 grinding the upper surface 101 are cleaned with the metal scrap dissolving water L2. As a result, metal scraps generated by grinding the electrodes are removed from the upper surface 101 and the grinding wheel 17. In addition, metal scraps adhering to the underside of the grinding wheel 17 are removed by the metal scrap dissolving water L2, preventing clogging of the underside of the grinding wheel 17.

[Second cleaning step]
After the first cleaning step is completed during the spark-out process, the control unit 7 performs a second cleaning step. That is, the control unit 7 supplies the metal scrap dissolved water L2 as cleaning water to the upper surface 101 of the wafer 100 to clean the upper surface 101 until the grinding wheel 17 is separated from the upper surface 101 of the wafer 100.

Specifically, the control unit 7 performs so-called escape cut processing by using the grinding feed mechanism 80 to slowly raise the grinding mechanism 10 at a preset escape cut processing speed V6 (time range T6 in Figure 2). During this time, the control unit 7 continues to supply metal scrap dissolved water L2 to the upper surface 101 of the wafer 100. The control unit 7 then performs escape cut processing until the grinding wheel 17 separates from the upper surface 101 of the wafer 100.

As a result, the upper surface 101 of the wafer 100, including the exposed electrodes, and the grinding wheel 17 grinding the upper surface 101 are subsequently washed with the metal scrap dissolving water L2, and metal scraps are removed from the upper surface 101 and the grinding wheel 17.
The metal scrap dissolved water L2 is supplied continuously during the time range T5 to T6, for example, as indicated by the double-headed arrow 302 in FIG.

[Pure water cleaning process]
After the second cleaning step during the escape cut process is completed, the control unit 7 performs a pure water cleaning step. That is, the control unit 7 sprays pure water L1 onto the wafer 100 to remove the metal scrap dissolved water L2 from the upper surface 101.

Specifically, the control unit 7 uses the grinding feed mechanism 80 to retract the grinding mechanism 10 to the origin height position at a relatively high retraction speed V7 (time range T7 in Figure 2).

At this time, the control unit 7 closes the cleaning water valve 67 of the cleaning mechanism 60 to stop the supply of metal scrap dissolving water L2 to the upper surface 101 of the wafer 100. Furthermore, the control unit 7 opens the processing water valve 72 of the processing water supply mechanism 70 to resume spraying pure water L1 from the processing water channel 73 onto the upper surface 101 of the wafer 100. The supply rate of pure water L1 is, for example, 3.0 L/min. The supply of pure water L1 is carried out continuously during time range T7, for example, as indicated by the double-headed arrow 303 in FIG. 2.

This cleans the top surface 101 of the wafer 100 and the grinding wheel 17 with pure water L1, removing any metal scrap dissolving water L2 adhering to them.

As described above, in this embodiment, when the height of the grinding wheel 17 is maintained for a predetermined period of time after the grinding process is completed (during spark-out processing), the first cleaning process is carried out, the supply of pure water L1 is stopped, and metal scrap dissolved water L2 is supplied to the upper surface 101 of the wafer 100, thereby cleaning the upper surface 101 where the electrodes are exposed. This makes it possible to shorten the time required for cleaning compared to transporting the wafer 100 to a separate cleaning device for cleaning.

Furthermore, since the first cleaning step is carried out during spark-out processing in which the grinding wheel 17 is in contact with the upper surface 101, the grinding wheel 17 can also be cleaned together with the upper surface 101.
Furthermore, the time from the completion of the grinding step to the start of the first cleaning step can be shortened, thereby improving the cleaning effect of the metal scrap dissolved water L2.
Furthermore, since citric acid water is used as the metal scrap dissolved water L2, the metal scrap dissolved water L2 can be easily handled.

In addition, in this embodiment, a second cleaning process is performed during the escape cut after the first cleaning process, and metal scrap dissolved water L2 is supplied to the upper surface 101 of the wafer 100 until the grinding wheel 17 separates from the upper surface 101, cleaning the upper surface 101 and the grinding wheel 17. This allows the upper surface 101 and the grinding wheel 17 to be cleaned more effectively without significantly increasing the cleaning time.

Furthermore, in this embodiment, after the second cleaning step, when the grinding wheel 17 is retracted to the origin height position, a pure water cleaning step is performed in which pure water L1 is sprayed onto the wafer 100 to remove the metal scrap dissolved water L2 from the upper surface 101. Therefore, it is possible to shorten the time required for pure water cleaning compared to when the wafer 100 is cleaned with pure water in a separate device.
The pure water L1 removes the metal chip dissolved water L2 from the grinding wheel 17.

In this embodiment, the second cleaning process is performed after the first cleaning process. However, the second cleaning process does not have to be performed. In this case, the pure water cleaning process may be performed during the escape cut after the first cleaning process.

Furthermore, for the pure water cleaning process, the wafer 100 may be removed from the chuck table 20 and transported to a spinner cleaning unit (not shown), and the pure water cleaning process may be performed on the wafer 100 using this spinner cleaning unit.

1: grinding device, 7: control unit, 10: grinding mechanism, 11: spindle,
13: Wheel mount, 15: Grinding wheel, 16: Wheel base,
17: Grinding wheel, 20: Chuck table, 21: Porous member, 22: Holding surface,
23: Frame, 30: Table rotation mechanism, 31: Motor, 32: Drive pulley,
33: endless belt, 34: driven pulley, 35: rotating shaft, 40: fluid distribution mechanism,
47: suction source, 48: air supply source, 49: water supply source, 60: cleaning mechanism,
61: cleaning water source, 63: cleaning water nozzle, 65: cleaning water piping, 67: cleaning water valve,
70: Processing water supply mechanism, 71: Processing water source, 72: Processing water valve, 73: Processing water channel,
75: Processing water piping, 80: Grinding feed mechanism, 100: Wafer, 101: Upper surface,
102: Lower surface, 105: Protective tape, 403: Suction groove,
460: rotary joint, 470: suction flow path, 471: suction piping,
473: suction flow rate adjusting unit, 475: suction opening/closing valve, 481: air piping,
483: air adjusting section, 485: air supply opening/closing valve, 491: water piping,
493: Water adjusting unit, 495: Water supply opening/closing valve

Claims (3)

A wafer grinding method comprising: holding a lower surface of a wafer having a plurality of electrodes sealed with resin on an upper surface side thereof by a holding surface of a chuck table; and grinding the upper surface of the wafer with a rotating annular grindstone to expose the electrodes on the upper surface,
a holding step of holding the lower surface of the wafer with the resin facing upward by the holding surface;
a grinding step in which the chuck table and the grindstone are brought relatively close to each other in a direction perpendicular to the holding surface, and the upper surface of the wafer is ground with the grindstone while pure water is supplied to the upper surface of the wafer, thereby exposing the plurality of electrodes on the upper surface;
a first cleaning step of cleaning the upper surface by maintaining the height of the grinding wheel at the time when the grinding step is completed for a predetermined time, stopping the supply of the pure water, and supplying water containing dissolved metal scraps onto the upper surface;
A method for grinding a wafer comprising: a second cleaning step of supplying water containing dissolved metal chips onto the upper surface to clean the upper surface until the grinding wheel is separated from the upper surface after the first cleaning step;
2. The method for grinding wafers according to claim 1. a pure water cleaning step of spraying pure water onto the wafer to remove water dissolved in metal scraps from the upper surface of the wafer;
3. The wafer grinding method according to claim 1 or 2.