JP2001260015A - Method and device for lapping semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for lapping a semiconductor wafer, for improving flatness of the wafer by reducing variations in the thickness of the semiconductor wafer. SOLUTION: In lapping, when a load detecting sensor 17 detect that an upper surface plate 15 and/or a lower surface plate 16 are brought into contact with a carrier plate 13 as overload of driving motor 14, the detected signal is transmitted to a lap finishing means 18, the lap finishing means 18 stops the driving motor 14, and lapping is finished. As a result, variations in the thickness of a silicon wafer W can be reduced, and flatness of the wafer W can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for lapping a semiconductor wafer, and more particularly to a method and an apparatus for lapping a semiconductor wafer in which the flatness of the wafer after lapping is enhanced and the thickness of each semiconductor wafer is suppressed from varying. .

[0002]

2. Description of the Related Art A lapping apparatus, which is widely used, inserts and holds a silicon wafer into a plurality of wafer holding holes formed in a carrier plate, and forms a slurry (lap liquid).
Is supplied from above, and each wafer is wrapped.
Specifically, the carrier plate rotates between a sun gear and an internal gear rotated by a rotation motor,
The silicon wafer in the wafer holding hole was wrapped by pressing / sliding the front and back surfaces (upper surface and lower surface) of the silicon wafer in the wafer holding hole against respective opposing surfaces (lap action surfaces) of the upper and lower stools. During the lap, the lower surface of the carrier plate is in contact with the lap working surface of the lower platen. At this time,
The thickness of the conventional carrier plate has been designed to be smaller than the thickness of the silicon wafer after wrapping which is set in advance. For example, the difference in thickness between the carrier plate and the silicon wafer was 70 μm or more. Further, in the conventional means, the detection of the end of the lap, that is, the detection when the wafer is wrapped to the set thickness, is performed by measuring the distance between the upper stool and the lower stool using a distance sensor. Was.

[0003]

However, according to such a conventional lapping apparatus, the end of the lap is detected by measuring the distance between the upper platen and the lower platen. The thickness was less than the thickness of the wrapped wafer. For this reason, for example, a diameter of 1
The upper surface plate and the lower surface plate having a large diameter such as 400 to 1500 mm have a large error in the distance measurement. Therefore, the flatness of the wrapped silicon wafer is 1.2 to 1.5 μg in GBIR.
m. In addition, for example, there is a variation in wafer thickness between wafers in one batch. In particular, large variations occurred in the wafer thickness between batches.

[0004] Therefore, as a result of diligent research, the inventor has designed the thickness of the carrier plate to be substantially the same as the thickness of the wafer after wrapping, and furthermore, when the end of wrapping is detected, the upper platen in the lap is used as a carrier plate The present inventors have found that the above-mentioned variation in the thickness of the wafer is eliminated and the flatness of the wafer is increased, and the present invention has been completed.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and an apparatus for wrapping a semiconductor wafer, which can reduce the variation in the thickness of the semiconductor wafer and can increase the flatness of the wafer. Another object of the present invention is to provide a method and an apparatus for wrapping a semiconductor wafer, which can detect that the surface plate has contacted the carrier plate without damaging the lapping surface of the surface plate. And Another object of the present invention is to provide a method and an apparatus for wrapping a semiconductor wafer, which can accurately detect the end of lapping by simple control.

[0006]

According to the first aspect of the present invention, a semiconductor wafer is held between an upper surface plate and a lower surface plate provided in parallel with each other while supplying a lapping liquid containing abrasive grains. In a semiconductor wafer lapping method in which a carrier plate held in a hole is rotated and revolved, and the front and back surfaces of the semiconductor wafer are simultaneously wrapped, a carrier plate having a thickness substantially equal to a predetermined thickness of the semiconductor wafer after lapping is set. A method for lapping a semiconductor wafer, comprising a step of preparing and a step of ending the lapping of a semiconductor wafer when detecting that the upper platen has contacted a carrier plate.

[0007] The number of wafer holding holes in the carrier plate is not limited. One or more may be used. That is, a single-wafer lapping apparatus or a batch-type lapping apparatus for batch-lapping a large number of semiconductor wafers may be used. Further, the material of the carrier plate is not limited. For example, SK material can be used. The size of the carrier plate is not limited. In addition, it is usually changed according to the diameter of the semiconductor wafer to be wrapped. further,
The type of lapping liquid used here is not limited. For example, there is a dispersion of alumina powder in water. The thickness of the carrier plate is changed according to the thickness of the semiconductor wafer at the end of the lap.

[0008] The method of detecting the state in which the upper stool contacts the carrier plate is not limited. For example, an overload on the drive unit of the upper stool and / or the drive unit of the lower stool may be detected. In addition, since the lower platen is always in contact with the carrier plate during the lap, the upper platen contacts the carrier plate in this way,
Usually, not only the drive unit of the upper stool but also the drive unit of the lower stool is overloaded. A general-purpose load detection sensor can be used as the load detection sensor. The operation of ending the lap is usually performed by stopping the rotation of the upper stool and the lower stool.

According to a second aspect of the present invention, the semiconductor wafer wrapping is terminated when an overload of the drive unit of the upper surface plate and / or the drive unit of the lower surface plate is detected. Wrapping method.

According to a third aspect of the present invention, there is provided an upper platen and a lower platen provided in parallel with each other, and a wafer holding hole for holding a semiconductor wafer interposed between the upper platen and the lower platen. In the lapping apparatus including the formed carrier plate, the carrier plate has a thickness substantially equal to a desired thickness of the wrapped semiconductor wafer, and detects that the upper platen has contacted the carrier plate. Then, the present invention provides a semiconductor wafer lapping apparatus provided with a lap ending means for ending the lapping of the semiconductor wafer.

According to a fourth aspect of the present invention, the lap ending means has a load detection sensor for detecting an overload of the drive unit of the upper stool and / or the drive unit of the lower stool. It is a lapping device for semiconductor wafers.

[0012]

According to the first and third aspects of the present invention, the lapping operation of the semiconductor wafer is terminated when it is detected that the upper platen has contacted the carrier plate during the lapping process. . As a result, variations in the thickness of the semiconductor wafer can be reduced. In addition, the carrier plate also serves as a guide plate for adjusting the thickness of the entire surface on both the front and back surfaces of the semiconductor wafer. As a result, the flatness of the semiconductor wafer after the lapping process is increased to about 0.5 μm, whereas the conventional silicon wafer has a GBIR of 1.2 to 1.5 μm.

According to the second and fourth aspects of the present invention, when an overload of the drive unit of the upper platen and / or the drive unit of the lower platen is detected, lapping of the semiconductor wafer is performed. To end. As a result, even when a simple control mechanism is used, it is possible to accurately detect the end of the lap.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a main part of a semiconductor wafer lapping apparatus according to one embodiment of the present invention. FIG. 2A is an enlarged sectional view of a main part of a semiconductor wafer according to one embodiment of the present invention, showing a state during lapping. FIG. 2B is an enlarged sectional view of a main part showing a state at the end of lapping of the semiconductor wafer according to one embodiment of the present invention. FIG. 3 is a block diagram showing a control system of a semiconductor wafer lapping apparatus according to one embodiment of the present invention.

As shown in FIGS. 1 and 2, the wrapping device 10 includes a sun gear 11 rotatably provided around an axis, an internal gear 12 provided rotatably coaxially with the shaft. A circular plate-shaped carrier plate 13 that meshes with these gears 11 and 12 at the same time and revolves and rotates. The thickness of the carrier plate 13 is substantially the same as the preset thickness of the silicon wafer W after lapping, and the material is SK material. A plurality of carrier plates 13 are arranged around the sun gear 11 and each carrier plate 1
3 is a wafer holding hole 1 for accommodating a silicon wafer W.
3a is drilled. Each silicon wafer W is inserted and held in these wafer holding holes 13a.

As shown in FIGS. 1 to 3, an upper surface plate 15 and a lower surface plate 16 are arranged above and below each carrier plate 13 in parallel with the plates 13. Both surface plates 1
The gears 5 and 16 are rotated in opposite directions by a single drive motor (drive unit) 14 via a gear type power transmission system. The drive motor 14 is provided with a load detection sensor 17 for detecting the load of the motor. On the other hand, the control system of the lapping device 10 is provided with lap ending means 18 for stopping the drive motor 14 and ending lapping based on an overload detection signal from the load detection sensor 17.

Next, a method of lapping the silicon wafer W by the lapping apparatus 10 will be described with reference to FIGS. FIG. 4 is a flow sheet showing a control procedure in the silicon wafer lapping apparatus according to one embodiment of the present invention. FIG. 5A is a graph showing an overload detection timing during lapping by the lapping device according to one embodiment of the present invention. FIG. 5B is a graph showing the transition of the motor current value during lapping by the conventional lapping device. FIG. 6A is a graph showing the relationship between the flatness (GBIR) of the silicon wafer after lapping by the lapping apparatus according to one embodiment of the present invention and the frequency in one batch. FIG. 6B is a graph showing the relationship between the frequency and the flatness of a silicon wafer after lapping by a conventional lapping apparatus.

First, lapping is started by the lapping device (S100). That is, the sun gear 11 and the internal gear 12 are rotated in directions opposite to each other while supplying the lapping slurry between the upper platen 15 and the lower platen 16 and each carrier plate 13. The drive motors 14 rotate both the platens 15, 16 in opposite directions.

Thus, for example, five silicon wafers W held on the carrier plate 13 are
5. Lapping of the front and back surfaces (upper and lower surfaces) of the silicon wafer is performed while rotating and revolving between the lower platen 16 (see FIG. 2A). During lapping, the lower surface of each carrier plate 13 is in contact with the lapping surface of the lower platen 16. As the slurry supplied during the wrap, for example, a slurry containing composite artificial emery (FO # 1200) is used. During this lap, the magnitude of the load applied to the output shaft of the drive motor 14 is always detected (S10).
1, S102). Specifically, the motor current is monitored, and when the measured value is equal to or more than the set value, the stop signal is turned ON. The motor current is a current value of a motor for driving a rotating shaft of a surface plate, and shows a constant current value during lapping of a silicon wafer (FIG. 5B).

Therefore, if the lap action surface of the upper platen 15 comes into contact with the opposing surface (upper surface) of the carrier plate 13 during lapping, the drive motor 14 is overloaded. More specifically, when the upper platen 15 contacts the upper surface of the carrier plate 13, the load on the rotating shaft and thus the motor main shaft becomes large. Therefore, the current value (actually measured value) is larger than during the lap of the silicon wafer W (FIG. 5A). Of course, the carrier plate 13 is in contact with the lap surface of the lower platen 16 from the start of the lap. Therefore, when the upper platen 15 comes into contact with the carrier plate, the carrier plate 13 is sandwiched between the upper platen 15 and the lower platen 16, so that the overload is actually detected from the path on the lower platen 16 side. Will be.
This overload is detected by the load detection sensor 17 and transmitted to the lap ending means 18 as an overload signal. Conventionally, such an overload is not applied since the upper platen does not contact the carrier plate (see FIG. 5B). Next, the drive motor 14
, A motor stop command is issued (S103). As a result, the drive motor 14 stops, and the processing of the wrap ends (S104). When the motor stops, the rotation of the sun gear 11 and the internal gear 12 also stops.

As described above, when the load detection sensor 17 detects that the upper platen 15 is in contact with the carrier plate 13, the lapping operation of the silicon wafer W is completed. It is possible to reduce the variation in the thickness of each silicon wafer W (20 wafers) and the variation in the thickness of the silicon wafer W between batches. Moreover, this carrier plate 13
Since it serves as a guide plate for adjusting the thickness of the entire surface on both the front and back surfaces of the silicon wafer W, the flatness (GBIR) of the wrapped silicon wafer W can be increased to about 0.5 μm.

FIG. 6A shows the flatness of a silicon wafer after lapping by a lapping apparatus 10 according to one embodiment of the present invention. The average value of the flatness is 0.43 μm. Carrier plate thickness is 78
It was set to 0 μm. FIG. 6B shows a silicon wafer after being lapped by a conventional lapping apparatus. The average value of the flatness was 1.30 μm, and the thickness of the carrier plate was 750 μm. When the two are compared, it is apparent that the silicon wafer by the lapping apparatus 10 according to one embodiment of the present invention has higher flatness. In addition, in this embodiment, since the carrier plate 13 is designed with a predetermined hardness, these lapping surfaces 15 and 16 can be attached to the carrier plate 13 without damaging the lap action surfaces of both lapping plates 15 and 16. The contact state can be detected. Furthermore, since the lapping of the silicon wafer W is terminated when an overload of the drive motor 14 of the upper lapping plate 15 and / or the lower lapping plate 16 is detected, a simple control mechanism can be used for accurate lapping. Detection can be performed.

[0023]

According to the present invention, the time when the upper surface plate abuts on the carrier plate is the time when the lapping is completed.
The variation in the thickness of the semiconductor wafer can be reduced between wafers of one batch and between wafers of each batch. In addition, the flatness of the wrapped wafer can be increased.

According to the second and fourth aspects of the present invention, when it is detected that an excessive load is applied to the drive unit of the upper stool and / or the drive unit of the lower stool, the lapping process is terminated. As a result, the end of the lapping process can be accurately detected with a simple control mechanism.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part of a semiconductor wafer lapping apparatus according to an embodiment of the present invention.

FIG. 2A is an enlarged cross-sectional view of a main part during lapping of a semiconductor wafer according to an embodiment of the present invention. (B)
FIG. 2 is an enlarged sectional view of a main part showing a state at the time of lapping of a semiconductor wafer according to one embodiment of the present invention.

FIG. 3 is a block diagram showing a control system of a semiconductor wafer lapping apparatus according to one embodiment of the present invention.

FIG. 4 is a flow sheet of a control system of the semiconductor wafer lapping apparatus according to one embodiment of the present invention.

FIG. 5A is a graph showing an overload detection timing during lapping by the lapping device of the present invention. (B)
5 is a graph showing a transition of a motor current value during lapping by a conventional lapping device.

FIG. 6A is a graph showing the flatness of a silicon wafer after lapping by the lapping apparatus of the present invention. (B) is a graph showing the flatness of a silicon wafer after lapping by a conventional lapping apparatus.

[Explanation of symbols]

 Reference Signs List 10 lapping device, 15 upper surface plate, 16 lower surface plate, 13 carrier plate, 13a wafer holding hole, 14 drive motor, 17 load detection sensor, 18 lap end means, W silicon wafer (semiconductor wafer).

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Kazuya Hosomi F-term (reference) 3C058 AB04 AB08 AC02 BA01 BA06 BA07 CB01 CB06 DA06 DA09 DA18 at 1-1-5 Otemachi, Chiyoda-ku, Tokyo

Claims (4)

[Claims] 1. A carrier plate in which a semiconductor wafer is held in a wafer holding hole is rotated and revolved while supplying a lapping liquid containing abrasive grains between an upper surface plate and a lower surface plate provided in parallel with each other. In a semiconductor wafer lapping method of lapping the front and back surfaces of a semiconductor wafer at the same time, a step of preparing a carrier plate having a thickness substantially equal to the thickness of the semiconductor wafer after lapping set in advance; and Ending the lapping of the semiconductor wafer when the contact is detected. 2. The lapping method of a semiconductor wafer according to claim 1, wherein the lapping of the semiconductor wafer is terminated when an overload of the drive unit of the upper stool and / or the drive unit of the lower stool is detected. 3. An upper platen and a lower platen provided in parallel with each other, and a carrier plate interposed between the upper platen and the lower platen and having a wafer holding hole for holding a semiconductor wafer formed therein. In the lapping apparatus, the carrier plate has a thickness substantially equal to a desired thickness of the semiconductor wafer after lapping, and detects that the upper platen has contacted the carrier plate, and wraps the semiconductor wafer. A semiconductor wafer wrapping device provided with a wrap ending means for ending the wrapping. 4. The semiconductor wafer lapping apparatus according to claim 3, wherein said lap ending means includes a load detection sensor for detecting an overload of the drive unit of the upper stool and / or the drive unit of the lower stool.