TW201632309A - Method of grinding workpiece - Google Patents

Abstract

The present invention provides a grinding method, in which the ground surface of the workpiece will not be left with scratches by the contact terminal of a thickness measuring device, irrespective of the kind of workpiece, and even if a protective member is adhered to the surface of the workpiece, the thickness of the workpiece can be measured while it is being ground. A grinding method is to grind for thinning the surface of a workpiece, whose surface is adhered with a protective member, to a specified thickness, characterized by comprising the following processes: a first grinding process to grind the back surface of the workpiece to a specified thickness while a second ultrasonic measuring device is used to measure the actual thickness of the workpiece in accordance with the difference in the propagation time of the reflected waves from the surface and the back surface of the workpiece; a protective member thickness calculating process, in which at the end of the first grinding process, the thickness of protective member is calculated according to the difference between the total thickness determined by the difference between the upper surface height position of the chuck table measured by a first ultrasonic measuring device and the upper surface height position of the workpiece measured by the second ultrasonic measuring device and the actual thickness of the workpiece measured by the second ultrasonic measuring device; and a second grinding process, which, after performing the protective member thickness calculating process, calculates the thickness of the grinding workpiece according to the difference between the upper surface height position of the workpiece measured by the second ultrasonic measuring device and the upper surface height position of the chuck table measured by the first ultrasonic measuring device as well as the thickness of the protective member, and grinds the workpiece to the target finished thickness.

Description

Grinding method of workpiece

The present invention relates to a method of grinding a plate-shaped workpiece such as a wafer.

A germanium wafer (hereinafter simply referred to as a wafer) in which a plurality of ICs, LSIs, and the like are formed on the surface, and the back surface is ground and thinned to a predetermined thickness, and then divided into individual element wafers by a cutting device. The divided component chips are various electronic devices widely used in mobile phones, personal computers, and the like.

In the back grinding of the wafer, the wafer held by the disk mounting table of the grinding device is rotated, and the grinding surface (back surface) of the wafer is brought into contact while the grinding stone is rotated, and the wafer is The thickness is measured while grinding.

In the method of measuring the thickness at this time, the thickness is measured while the contact terminal is in contact with the ground surface of the rotating wafer and the upper surface (reference surface) of the frame of the disk mounting table, and the time is reached when the predetermined thickness is reached. For example, Japanese Laid-Open Patent Publication No. SHO-63-256360, JP-A-2000-006018, and JP-A-2001-009716 Reference).

[Practical Technical Literature] [Patent Literature]

[Patent Document 1] JP-A-63-256360

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2000-006018

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2001-009716

However, in the measurement method of thickness measurement while contacting the contact terminals on one side, since the thickness of the contact terminal of the thickness measuring device is measured while being in contact with the ground surface of the wafer, contact is made on the ground surface of the wafer. The problem of scratching the contact of the terminal contact.

In the contact measurement method, since the total thickness of the protective member including the thickness of the wafer and the surface of the wafer is measured by the thickness measuring device, the grinding process is performed, so that the thickness of the protective member is In the case of unevenness, the difference will also appear in the measured thickness, and there is a problem that the thickness cannot be measured with high precision.

Here, a grinding method in which a wafer is thinned to a predetermined thickness while measuring the thickness of the wafer during grinding using a laser beam is also proposed. In this method, although the thickness of the wafer is measured by the difference in arrival time between the reflected wave reflected from the upper surface of the wafer and the reflected wave reflected from the lower surface of the wafer, the laser beam having a specific wavelength depending on the type of the workpiece is not transparent. The problem of the wafer has a case where the thickness measurement method using the laser beam cannot be applied depending on the kind of the workpiece.

In view of the above, the object of the present invention is to prevent the scratch of the contact terminal of the thickness measuring device from being left on the surface to be processed of the workpiece, irrespective of the type of the workpiece, and even if it is attached to the surface side of the workpiece. The protective member may also provide a grinding method of the workpiece to be ground while measuring the thickness of the workpiece.

According to the present invention, it is possible to provide a method for grinding a workpiece by using a tray mounting table provided with a workpiece to be bonded to the surface protection member and being held by the protection member, and to be held by the tray Grinding means for grinding the back surface of the workpiece on the mounting table, and grinding device for ultrasonic measuring means for measuring the thickness of the workpiece, grinding the back surface of the workpiece to thin the workpiece to a predetermined thickness The ultrasonic measuring device includes: a first ultrasonic measuring device that is disposed facing the upper surface of the disk mounting table, and measures the height of the upper surface of the disk mounting table, and is maintained The surface of the workpiece on the tray mounting table faces each other, and the propagation time from the reception of the reflected wave reflected from the upper surface of the workpiece to the ultrasonic wave that is oscillated is reflected to the lower surface of the workpiece. The second ultrasonic measuring device that measures the actual thickness of the workpiece after the reflected wave is received by the reflected wave, and the method for grinding the workpiece includes: measuring only the second ultrasonic wave by one side Instrument measurement Is the real thickness of the workpiece, while up to a predetermined thickness by grinding the back surface of the first workpiece a grinding process; and at the end of the first grinding process, according to the upper height position of the disk mounting table measured by the first ultrasonic measuring device and the processed by the second ultrasonic measuring device a thickness of the protective member for calculating the thickness of the protective member, and a total thickness of the difference between the height position of the object and the difference between the actual thickness of the workpiece measured by the second ultrasonic measuring device; and the protection After the component thickness calculation process is performed, the difference between the height position of the upper surface of the workpiece measured by the second ultrasonic measuring device and the height position of the upper surface of the tray mounting table measured by the first ultrasonic measuring device, and the protection The thickness of the member is calculated by the thickness of the workpiece during grinding, and the second grinding process is performed until the workpiece is ground to the target finishing thickness.

Preferably, between the first ultrasonic measuring device and the disk mounting table, and between the second ultrasonic measuring device and the ground surface of the workpiece, the first and second grinding are performed while being filled with water. process.

In the grinding method of the present invention, the means for measuring the thickness of the workpiece is used to grind the workpiece to the target while measuring the height position of the surface to be ground of the workpiece using an ultrasonic measuring instrument. Since the thickness is finished, there is no scratch on the ground surface of the workpiece.

In the thickness of the workpiece, the thickness of the workpiece is measured and the thickness of the workpiece is finished, and the height of the upper surface of the pallet is measured and the workpiece is ground. The upper height position of the noodles is ground and processed, so you can use the comparison. An inexpensive ultrasonic measuring device grinds the workpiece to the target finishing thickness.

Further, even if the protective member is attached to the surface of the workpiece, since the protective member is pressed by the grinding pressure in the grinding of the solid thickness of the workpiece, the thickness of the protective member is not uniformly diminished. The workpiece can be precisely ground to the target finishing thickness.

2‧‧‧grinding device

4‧‧‧Base

4a‧‧‧ recess

6‧‧‧ body

8‧‧‧Guided track

10‧‧‧ grinding unit

11‧‧‧Semiconductor wafer

11a‧‧‧ below

11a‧‧‧ surface

11b‧‧‧above

11b‧‧‧Back

12‧‧‧ Spin shaft housing

13‧‧ ‧ grid

14‧‧‧Support

15‧‧‧ components

16‧‧‧Mobile abutments

17‧‧‧Component field

18‧‧‧ Spin axis

19‧‧‧External redundant areas

20‧‧‧Motor

21‧‧‧V-shaped gap

22‧‧‧Roller bracket

23‧‧‧Protective zone

24‧‧‧ grinding wheel

26‧‧‧Roller abutment

28‧‧‧ grinding diamonds

30‧‧‧Ball screw

31‧‧‧ bolt

32‧‧‧pulse motor

34‧‧‧ grinding unit feeding mechanism

36‧‧‧挟盘台机构

38‧‧‧挟盘台

38a‧‧‧above

44‧‧‧Operation panel

48‧‧‧Ultrasonic measurement

50‧‧‧1st ultrasonic measuring instrument

52, 56‧‧‧Cylinder components

54‧‧‧2nd ultrasonic measuring instrument

58‧‧‧ Waveform detection department

60‧‧‧Thickness calculation unit

62‧‧‧Control means

64‧‧‧ waveform

66‧‧‧ waveform

68‧‧‧ Waveform

[Fig. 1] A perspective view of a grinding apparatus in which the grinding method of the present invention can be carried out.

[Fig. 2] A perspective view of the surface side of the wafer.

[Fig. 3] A rear side perspective view of a ruthenium wafer in a state in which a protective tape is bonded to the surface.

[Fig. 4] A perspective view illustrating the first and second grinding processes.

[Fig. 5] A partial cross-sectional side view showing the first grinding process.

[Fig. 6] A view showing a waveform diagram of the first and second ultrasonic measuring devices in the first grinding process.

[Fig. 7] A partial cross-sectional side view showing the second grinding process.

[Fig. 8] A view showing a waveform diagram of the first and second ultrasonic measuring devices in the second grinding process.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to Fig. 1, an external perspective view of a grinding apparatus 2 suitable for carrying out the grinding method of the present invention is shown. 4 is a base of the grinding device 2, and a body 6 is erected behind the base 4. In the body 6, a pair of guide rails 8 extending in the vertical direction are fixed.

The grinding unit (grinding means) 10 is mounted to be movable in the vertical direction along the pair of guide rails 8. The grinding unit 10 includes a spin shaft housing 12 and a support portion 14 that holds the spin shaft housing 12, and the support portion 14 is attached to the moving base 16 that moves in the vertical direction along the pair of guide rails 8. .

The grinding unit 10 includes a spin shaft 18 rotatably housed in the spin shaft housing 12, a motor 20 that rotationally drives the spin shaft 18, and a roller that is fixed to the tip end of the spin shaft 18. The bracket 22 and the grinding roller 24 detachably mounted to the roller bracket 22 are provided.

The grinding device 2 is provided with a grinding unit feeding mechanism 34 including a ball screw 30 and a pulse motor 32 that moves the grinding unit 10 in the vertical direction along the pair of guide rails 8. When the pulse motor 32 is driven, the ball screw 30 rotates, and the moving base 16 is moved in the vertical direction.

A recess 4a is formed on the upper surface of the base 4, and a tray mounting mechanism 36 is disposed in the recess 4a. The disk mounting table mechanism 36 has a disk mounting table 38 that is moved in the Y-axis direction between the wafer loading and unloading position A and the grinding position B of the grinding unit 10 by a moving mechanism (not shown). . 40, 42 is a snake belly tube. In the front side of the base 4, equipped The operator of the grinding device 2 inputs the operation panel 44 to which grinding conditions and the like are input.

Referring to Fig. 2, the semiconductor wafer 11 is formed of, for example, a germanium wafer having a thickness of 700 μm, and a plurality of ruled lines (divided lines) 13 on the surface 11a are formed in a lattice shape, and are partitioned by the plurality of ruled lines 13. An element 15 such as an IC or an LSI is formed in each field.

The semiconductor wafer 11 configured as described above includes an element region 17 in which the element 15 is formed, and a peripheral excess field 19 in which the element region 17 is surrounded. Further, a V-shaped notch 21 as a mark indicating the crystal orientation of the germanium wafer is formed on the outer circumference of the semiconductor wafer 11.

Before the grinding of the back surface 11b of the wafer 11, the protective tape 23 is bonded to the surface 11a of the wafer 11 by a protective tape bonding process in advance. The protective tape 23 is a structure in which a paste layer is disposed on the surface of a substrate such as polyvinyl chloride or polyolefin. Instead of the protective tape 23, another protective member may be attached to the surface 11a of the wafer 11.

The workpiece to which the grinding method of the present invention is applied is not limited to the tantalum wafer, and the grinding of the present invention can be applied to other sheet-like workpieces such as an optical element wafer to which a protective member is bonded to the surface. method.

In the grinding method of the present invention, the protective tape 23 side of the wafer 11 is sucked and held by the disk mounting table 38 positioned at the wafer attaching and detaching position A, and the back surface 11b of the wafer 11 is exposed. Then, the disk mounting table 38 is moved in the Y-axis direction by a moving mechanism (not shown), and the wafer 11 is positioned at the grinding position shown in FIG. 4 for the grinding roller 24 on the opposite side.

In Fig. 4, the grinding roller 24 is detachably attached to the spin shaft 18 fixed to the grinding unit 10 by a plurality of bolts 31. The end of the roller bracket 22. The grinding roller 24 is configured by fixing a plurality of grinding vermicum 28 annularly to the free end portion (lower end portion) of the roller base 26.

As shown in Fig. 5, the ultrasonic measuring means 48 includes a first ultrasonic measuring device 50 for measuring the height position of the upper surface 38a of the casing of the cymbal mounting table 38, and measuring the thickness of the wafer 11. The second ultrasonic measuring device 54.

The first and second ultrasonic measuring devices 50 and 54 are relatively inexpensive ultrasonic measuring devices that oscillate ultrasonic waves having a frequency of 20 MHz, and can accurately have a thickness of a plate-shaped workpiece such as a wafer having a thickness of 200 μm or more. measuring.

Preferably, the distance between the first ultrasonic measuring device 50 and the upper surface 38a of the disk mounting table 38 and the distance between the second ultrasonic measuring device 54 and the upper surface (back surface) 11b of the wafer 11 are set to 2 ~3mm degree.

A cylindrical member 52 is disposed at a tip end portion of the first ultrasonic measuring device 50, and a cylindrical member 56 is disposed at a tip end portion of the second ultrasonic measuring device 54. In the measurement of the height position of the upper surface 38a of the disk mounting table 38 by the first ultrasonic measuring device 50, pure water is supplied to the cylindrical member 52, and the ultrasonic wave oscillated from the ultrasonic measuring device 50 is Spread in pure water.

Similarly, in the measurement of the height position of the upper surface (back surface) 11b of the wafer 11 by the second ultrasonic measuring device 54, pure water is supplied to the cylindrical member 56, and the second ultrasonic measuring device is used. 54 The oscillated ultrasonic wave propagates into the wafer 11 in pure water.

During the first grinding process, as shown in Figure 4, The stage 38 is rotated by, for example, 300 rpm in the direction indicated by the arrow a, and the grinding roller 24 is rotated by, for example, 6000 rpm in the direction indicated by the arrow b, and the grinding unit feeding mechanism 34 drives the grinding of the grinding roller 24. The diced stone 28 is in contact with the back surface 11b of the wafer 11.

Further, the grinding roller 24 is ground by a predetermined grinding feed rate to a predetermined amount below. As shown in Fig. 5, while the thickness of the wafer 11 is measured by the non-contact ultrasonic measuring means 48, the wafer 11 is ground to a predetermined thickness, that is, the effective measurement range of the second ultrasonic measuring device 54 is also It is 200μm.

In the first grinding process, the grinding is completed only while measuring the solid thickness of the wafer 11 using the second ultrasonic measuring device 54. In other words, the propagation time from the reception of the reflected wave reflected from the upper surface (back surface) 11b of the wafer 11 by the ultrasonic wave oscillated from the second ultrasonic measuring device 54 and the lower surface (surface) of the wafer 11 The difference in propagation time until the reflected wave of the 11a reflection is received, and the thickness of the wafer 11 is calculated.

Referring to Fig. 6, a waveform diagram of the ultrasonic measuring means 48 in the first grinding process is displayed. 64 is a waveform diagram showing the first ultrasonic measuring device 50, 66 is a waveform showing a reflected wave of the second ultrasonic measuring device 54 reflected by the upper surface of the wafer 11, and 68 is a display which is reflected by the lower surface of the wafer 11. The waveform of the reflected wave.

The arrival time of the reflected wave of the lower surface 11a of the wafer 11 is delayed from the arrival time of the reflected wave from the upper surface 11b of the wafer 11, and is received by the second ultrasonic measuring device 54. The waveform 64 of the first ultrasonic measuring device 50 and the waveform 66 of the reflected wave on the upper surface of the second ultrasonic measuring device 54 and The waveform 68 of the reflected wave below is detected by the waveform detecting unit 58 connected to the ultrasonic measuring means 48.

The propagation time from the reception of the reflected wave reflected by the upper surface (back surface) 11b of the wafer 11 by the second ultrasonic measuring device 54 detected by the waveform detecting unit 58 and the lower surface (surface) of the wafer 11 The thickness calculation unit 60 calculates the difference in the propagation time from the reflection of the reflected wave of the 11a, and the thickness calculation unit 60 calculates the thickness (solid thickness) of the wafer 11 while completing the first grinding process.

In the first grinding process, although the reflected wave of the upper surface 38a of the disk mounting table 38 of the first ultrasonic measuring device 50 is received, the reflected wave is not detected in the measurement of the solid thickness of the wafer 11. use.

In the waveform diagram of FIG. 6, the arrow 70 is a time difference between the time when the reflected wave on the upper surface of the wafer 11 is received and the reflected wave below the wafer 11 is received, and the time difference is set to t. When the sound velocity in the wafer 11 is set to v, the thickness of the wafer 11 in the thickness calculation unit 60 can be calculated from vt/2.

When the first grinding process is carried out, since the protective tape 23 is pressed from above by the grinding pressure, the variations in the thickness of the protective tape 23 are not resolved, and the protective tape 23 has the same thickness.

Therefore, at the end of the first grinding process, the height position from the upper surface 38a of the disk mounting table 38 measured by the first ultrasonic measuring device 50, and the crystal measured by the second ultrasonic measuring device 54 The protective tape 23 is obtained by the difference between the total thickness of the wafer 11 + the protective tape 23 and the actual thickness of the wafer 11 measured by the second ultrasonic measuring device 54 obtained by the difference in the height position of the upper surface 11b of the circle 11. Thickness measurement.

The thickness of the wafer 11 calculated by the thickness calculation unit 60 is a predetermined thickness. When the thickness is 200 μm in the present embodiment, the signal is sent from the thickness calculation unit 60 to the control unit 62, and the control unit 62 feeds the grinding unit. The rotation of the pulse motor 32 of the mechanism 34 is stopped, and the first grinding process is terminated.

After the thickness calculation process of the protective tape 23 is performed, the second grinding process of grinding the wafer 11 to the target finishing thickness is performed. In the second grinding process, as shown in Fig. 7, the height position of the upper surface 38a of the disk mounting table 38 measured by the first ultrasonic measuring device 50 and the second ultrasonic measuring device 54 are measured. The difference in the height position of the upper surface (back surface) 11b of the wafer 11 and the thickness of the protective tape 23 are calculated by the thickness calculation unit 60 by the thickness of the wafer 11, and the wafer 11 is ground to a target finishing thickness, for example, 50 μm. .

Referring to Fig. 8, the waveforms of the first ultrasonic measuring device 50 and the second ultrasonic measuring device 54 in the second grinding process are shown. 66 is a reflected wave in the upper surface (back surface) 11b of the wafer 11 on which the ultrasonic wave oscillated from the second ultrasonic measuring device 54 is displayed, and shows that the reflected wave is received as the wafer 11 is ground. The time of transmission is gradually delayed.

In the present embodiment, the measurement is carried out while the pure water is filled in the cylinder 52 attached to the tip end of the first ultrasonic measuring device 50 and the cylinder 56 attached to the tip end of the second ultrasonic measuring device 54 because Since the grinding of the wafer 11 is performed while supplying the grinding water, the grinding chips are mixed into the grinding water, so that the grinding water mixed with the grinding chips is supplied to the pure members of the cylindrical members 52 and 56. Thickness measurement the amount.

In the above-described embodiment, the wafer 11 is subjected to the first grinding process and the second wafer by the non-contact measurement while the thickness of the wafer 11 is measured by a relatively inexpensive ultrasonic oscillator that oscillates 20 MHz of ultrasonic waves. Since the grinding process is performed until the target finishing thickness is performed, the grinding surface of the workpiece is not scratched, and the first grinding process can be performed while measuring the actual thickness of the workpiece regardless of the type of the workpiece.

In the above-described embodiment, the grinding method of the workpiece to which the protective member is bonded to the surface has been described. However, the grinding method of the present invention is not limited thereto, and the processed member is not attached to the surface. The same can be applied.

10‧‧‧ grinding unit

11‧‧‧Semiconductor wafer

11a‧‧‧ below

11a‧‧‧ surface

11b‧‧‧above

11b‧‧‧Back

18‧‧‧ Spin axis

22‧‧‧Roller bracket

23‧‧‧Protective zone

24‧‧‧ grinding wheel

26‧‧‧Roller abutment

28‧‧‧ grinding diamonds

38‧‧‧挟盘台

38a‧‧‧above

48‧‧‧Ultrasonic measurement

50‧‧‧1st ultrasonic measuring instrument

52‧‧‧Cylinder components

54‧‧‧2nd ultrasonic measuring instrument

56‧‧‧Cylinder components

58‧‧‧ Waveform detection department

60‧‧‧Thickness calculation unit

62‧‧‧Control means

Claims (2)

A grinding method for a workpiece is a method of grinding a back surface of a workpiece by using a grinding device to thin the workpiece to a predetermined thickness, and the grinding device includes: a surface to be bonded to the surface protection member a disk mounting table that the workpiece passes through the protective member, a grinding device that grinds the back surface of the workpiece held by the disk mounting table, and an ultrasonic measuring device that measures the thickness of the workpiece. The ultrasonic measuring device includes: a first ultrasonic measuring device disposed opposite to an upper surface of the disk mounting table, measuring a height position of the upper surface of the disk mounting table; and a second ultrasonic wave The measuring device is disposed so as to face the upper surface of the workpiece held by the tray mounting table, and the propagation time until the ultrasonic wave to be oscillated is received by the reflected wave reflected from the upper surface of the workpiece, and The difference in propagation time from the reflection of the reflected wave reflected from the lower surface of the workpiece is measured by the actual thickness of the workpiece. The method of grinding the workpiece includes: measuring only by the second ultrasonic measuring device Processed a first grinding process in which the back surface of the workpiece is ground to a predetermined thickness; and at the end of the first grinding process, based on the disk load measured by the first ultrasonic measuring device The total height of the upper height position of the table and the difference in the height position of the workpiece measured by the second ultrasonic measuring device, and the actual thickness of the workpiece measured by the second ultrasonic measuring device thick a difference between the thickness of the protective member for calculating the thickness of the protective member; and a height position of the workpiece measured by the second ultrasonic measuring device and the first ultrasonic wave after the protective member thickness calculation process is performed The difference between the height position of the upper surface of the disk mounting table measured by the measuring device and the thickness of the protective member, the thickness of the workpiece during grinding is calculated, and the second grinding is performed until the workpiece is ground to the target finishing thickness. Cutting process. The method of grinding a workpiece according to the first aspect of the invention, wherein the first ultrasonic measuring device and the disk mounting table are disposed between the second ultrasonic measuring device and the back surface of the workpiece It is filled with water.