TWI673138B - Wafer polishing method - Google Patents

Abstract

The invention is a polishing device comprising a plurality of polishing heads which are attached to a polishing cloth on which a polishing wafer is adhered, and which can simultaneously rotate the wafer and push the wafer to the polishing cloth while applying a polishing load to the wafer. When the polishing head is rotated, the wafer supported by the polishing head is pushed against the polishing cloth for polishing. Among the multiple polishing heads, each polishing head individually has a pressure control mechanism for controlling the polishing load of the polishing head and A rotation control mechanism that controls the rotation speed of the polishing head. Thereby, a polishing method is provided to suppress the processing amount distribution between the polishing heads and the variation in the processing amount to be extremely small.

Description

Wafer grinding method

The invention relates to a polishing device and a polishing method.

In a method for polishing a semiconductor wafer such as a single crystal silicon wafer, a polishing device 101 as shown in FIG. 12 is used. The polishing device 101 is provided with a polishing cloth 103 adhered to a rotatable platform 102 and is located above a platform. Two or more polishing heads 130a and 130b, and a polishing agent supply mechanism 104 that can supply polishing agents to the polishing cloth 103.

A template assembly is attached to each of the polishing heads 130a and 130b. The template assembly is formed by combining a back pad 131 and a support guide 132 made of resin such as glass epoxy material, and the like, and the back pad 131 And the support guide 132, each polishing head can support the back side surface of the wafer W (see Patent Documents 1 and 2). In addition, the polishing heads 130a and 130b can be rotated, and the supported wafer can be pushed against the polishing cloth 103 and polished. In addition, the polishing head can control the polishing load. For example, if the polishing heads 130a and 130b are as shown in FIG. 12, it can be controlled by controlling the internal pressure A (external pressure) of the first space portion 133. The contact pressure between the support guide 132 and the polishing cloth 103 can be controlled by controlling the pressure B (internal pressure) inside the second space portion 134.

In addition, in a general polishing apparatus, the shape of the wafer W after polishing is controlled by controlling the polishing load applied to the wafer W and the peripheral speed of the wafer W. In the polishing apparatus 101 of FIG. 12, the pressure A (external pressure) that controls the contact pressure between the support guide 132 (the guide portion of the template) and the polishing cloth 103 and the wafer W and the polishing cloth can be controlled. The pressure B (internal pressure) of the contact pressure of 103 is controlled, and The shape of the wafer W can be controlled by adjusting the pressure difference between the pressures A and B. Furthermore, the peripheral speed of the wafer W can be controlled by the rotation speed of the polishing heads 130a and 130b.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent No. 4833355

[Patent Document 2] Japanese Patent Application Publication No. 2012-35393

Generally, in a polishing apparatus 101 having a plurality of polishing heads 130a and 130b as shown in FIG. 12, all the polishing heads are subjected to polishing processing using a common polishing load and a peripheral speed (rotational speed). The reason why all the grinding heads have the same grinding load and rotation speed is because even when there are two or more grinding heads, the load control of all the grinding heads is controlled by a common pressure control mechanism. The circumferential speed control (speed control) is also controlled by a common rotation control mechanism. In the case of the grinding device 101, as shown in Figs. 12 and 13, the grinding load control of the grinding heads 130a and 130b, that is, the above-mentioned external pressure and internal pressure control are individually controlled by a common controller and electro-pneumatic regulator. get on. Similarly, as shown in FIGS. 12 and 13, the rotation speeds of the grinding heads 130 a and 130 b are controlled by the same controller and motor.

When the polishing apparatus has a plurality of polishing heads, a difference in the shape of the processing amount of the wafer (a processing amount distribution, a magnitude of the processing amount, and the like) occurs between the polishing heads. In the past, in order to reduce this difference, Polishing is carried out by uniformly using all polishing heads with a polishing load that reduces the difference in the shape of the machining amount between the polishing heads. For example, the common external pressure and internal pressure are generally set to appropriate values in all the grinding heads, and the difference between the external pressure and the internal pressure is optimized so as to reduce the difference in the shape of the machining amount between the grinding heads, so that Control the warping and slumping of the outer periphery of the wafer. In addition, since the shape of the wafer can also be controlled by controlling the ratio of the rotation speed of the polishing head to the rotation speed of the table, polishing is generally performed on all polishing heads using a uniform rotation speed that can reduce the difference in processing volume and shape. .

However, the conventional grinding device using a uniform grinding load and rotation speed for all the grinding heads cannot individually adjust the uneven distribution of the processing amount inherent in the grinding heads for each grinding head. Furthermore, since all the grinding heads are The grinding load is set so that the difference in the shape of the machining amounts between the grinding heads can be made small. In fact, the shape of the machining amount between the grinding heads cannot be infinitely approached to zero. In addition, there is also a problem that once the polishing load is adjusted to match the distribution of the processing amount, the variation in the processing amount (the amount of processing amount) between the polishing heads becomes large, and the processing amount between the polishing heads cannot be matched.

In view of the problems as described above, an object of the present invention is to provide a polishing apparatus and a polishing method capable of suppressing the processing amount distribution and the variation in the processing amount between polishing heads to extremely small.

In order to achieve the above object, the present invention provides a polishing device including a platform and a support to which a polishing cloth to which a polishing wafer is adhered, and at the same time being able to rotate the wafer and pushing it to the wafer while applying a polishing load to the wafer. A plurality of polishing heads of the polishing cloth, while rotating the polishing head, push the wafer supported by the polishing head against the polishing cloth for polishing, wherein the plurality of polishing heads are individually provided for each polishing head. A pressure control mechanism that controls the polishing load of the polishing head and a rotation control mechanism that controls the rotation speed of the polishing head.

In this case, the polishing load and the rotation speed can be individually set to arbitrary values for each polishing head, and in particular, the difference in the processing amount distribution of the wafer between the polishing heads and the difference in the processing amount can be suppressed to be extremely small Method, set the grinding load and rotation speed for each grinding head.

At this time, the polishing head includes a back pad supporting the back surface of the wafer, a ring-shaped support guide supporting the side surface of the wafer, and the pressure control mechanism that controls the polishing head as the polishing load. The contact pressure between the wafer being supported and the polishing cloth, and the contact pressure between the support guide and the polishing cloth are preferred.

If it is a polishing device capable of controlling the contact pressure between the wafer and the polishing cloth supported by the polishing head, and the contact pressure between the support guide and the polishing cloth, it can be accurately controlled by adjusting the difference between these contact pressures. Wafer processing volume distribution.

Furthermore, in order to achieve the above-mentioned object, the present invention provides a wafer polishing method, in which a plurality of polishing heads are individually controlled in each polishing head according to the pressure control mechanism and the rotation control mechanism provided in each polishing head. The wafer is polished by the polishing load and the rotation speed.

By individually controlling the polishing load and the rotation speed of each polishing head, it is possible to independently set the processing amount distribution and processing amount of the wafer to be polished at each polishing head for each wafer. In particular, the difference in the distribution of the processing amount of the wafer between the polishing heads and the difference in the processing amount can be minimized.

Furthermore, it is possible to control the difference in the processing amount distribution of the wafer between the plurality of polishing heads by controlling the polishing load for each of the polishing heads, and to control the plurality of rotations by controlling the rotation speed for each of the polishing heads. The processing amount of the wafer between the polishing heads is different.

In this way, by controlling the processing volume distribution difference and processing volume difference between the polishing heads, and even reducing these differences, the variation in the shape of the wafer between the polishing heads can be minimized.

According to the polishing apparatus and the wafer polishing method of the present invention, it is possible to suppress the processing amount distribution between the polishing heads and the variation in the processing amount to be extremely small. It is even possible to control the polishing load and rotation speed of each polishing head in such a way that the difference in the processing amount distribution of the wafers generated between the plurality of polishing heads and the difference in the processing amount are minimized, and a wafer with a uniform shape can be obtained. .

1‧‧‧ grinding device

2‧‧‧ platform

3‧‧‧ abrasive cloth

4‧‧‧ Abrasive supply mechanism

10a‧‧‧Pressure control mechanism

10b‧‧‧Pressure control mechanism

11a‧‧‧The first electro-pneumatic regulator

11b‧‧‧The first electro-pneumatic regulator

12a‧‧‧Second electro-pneumatic regulator

12b‧‧‧Second electro-pneumatic regulator

13a‧‧‧Controller

13b‧‧‧controller

20a‧‧‧rotation control mechanism

20b‧‧‧rotation control mechanism

21a‧‧‧Motor

21b‧‧‧Motor

22a‧‧‧Controller

22b‧‧‧controller

30‧‧‧Grinding head

30a‧‧‧Grinding head

30b‧‧‧ grinding head

31a‧‧‧Back pad

31b‧‧‧Back pad

32a‧‧‧Support Guide

32b‧‧‧Support Guide

33a‧‧‧First Space Department

33b‧‧‧First Space Department

34a‧‧‧Second Space Department

34b‧‧‧Second Space Department

101‧‧‧Grinding device

102‧‧‧platform

103‧‧‧ abrasive cloth

104‧‧‧abrasive supply mechanism

130a‧‧‧ grinding head

130b‧‧‧ grinding head

131‧‧‧Back pad

132‧‧‧Support guide

133‧‧‧First Space Department

134‧‧‧Second Space Department

W‧‧‧ Wafer

FIG. 1 is a schematic diagram showing an example of a polishing apparatus of the present invention.

FIG. 2 is a schematic diagram showing a method for controlling a grinding load and a rotation speed of a grinding device of the present invention.

FIG. 3 is a flowchart of the adjustment steps in the wafer polishing method of the present invention.

FIG. 4 is a processing amount distribution in each polishing head before the polishing load adjustment in the example.

FIG. 5 is a processing amount distribution in each polishing head after the polishing load is adjusted in the embodiment.

FIG. 6 shows the grinding load and the machining amount of each grinding head before and after the rotation speed is adjusted in the embodiment.

FIG. 7 shows the distribution of the processing amount in each polishing head after the polishing load adjustment of the comparative example.

FIG. 8 shows the processing amount in each polishing head after the polishing load adjustment of the comparative example.

FIG. 9 is a measurement result of ΔSFQR (max) of the silicon wafer after the polishing in the experimental example and the comparative example.

FIG. 10 is a measurement result of ΔESFQR (max) of the silicon wafer after the polishing of the experimental example and the comparative example.

FIG. 11 is a measurement result of the processing amount of the silicon wafer after the polishing in the experimental example and the comparative example.

FIG. 12 is a schematic diagram showing an example of a conventional grinding apparatus.

FIG. 13 is a schematic view showing a method for controlling a grinding load and a rotation speed of a conventional grinding apparatus.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.

First, the grinding apparatus of the present invention will be described with reference to FIGS. 1 and 2. As shown in FIG. 1, the polishing apparatus 1 of the present invention includes a platform 2 to which a polishing cloth 3 to which a polishing wafer W is adhered, and a wafer W which is supported and can be rotated at the same time, and can be pushed while a polishing load is applied to the wafer W. The plurality of polishing heads 30 abut against the polishing cloth 3. FIG. 1 illustrates a case where two or more polishing heads (the polishing head 30 a and the polishing head 30 b in FIG. 1) are provided above one platform 2. However, the number of the plurality of polishing heads 30 is not limited to this, and the polishing device of the present invention may be provided with three or more polishing heads above one platform 2. It is also possible to include an abrasive supply mechanism 4 for supplying an abrasive to the polishing cloth 3.

Each of the plurality of grinding heads in the grinding device of the present invention has a pressure control mechanism for controlling the grinding load of the grinding head and a rotation control mechanism for controlling the rotation speed of the grinding head. In the case of the grinding device 1 of FIG. 1, the grinding head 30a has a pressure control mechanism 10a and a rotation control mechanism 20a, the grinding head 30b has a pressure control mechanism 10b and a rotation control mechanism 20b, and the grinding head 30a and the grinding head 30b can be controlled independently of each other. Composition of grinding load and rotation speed. In such a polishing apparatus 1, the polishing head 30 a and the polishing head 30 b can be rotated, and at the same time, the wafer W supported by the polishing head 30 a and the polishing head 30 b can be pushed against the polishing cloth 3 and polished.

If so, it is possible to individually control the polishing load and rotation speed at arbitrary values for each polishing head, and to control the wafer shape of each polishing head. This makes it possible to set the polishing load and the rotation speed for each polishing head in such a manner that the difference in the processing amount distribution of the wafers between the polishing heads and the difference in the processing amount are minimized. That is, it is possible to obtain wafers having almost the same processing shape distribution and processing amount difference in wafers in all the polishing heads. In addition, since polishing can be performed at different polishing loads and rotation speeds between each polishing head, wafers with different specifications and shapes can be manufactured in one polishing, thereby obtaining wafers of various varieties.

The polishing apparatus 1 of the present invention as described above can be configured as follows. That is, more specifically, it is preferable that the polishing head has a back pad supporting the back surface of the wafer and a ring-shaped support guide supporting the side surface of the wafer. As a polishing load, the pressure control mechanism can control the polishing The contact pressure between the wafer supported by the head and the polishing cloth, and the contact pressure between the support guide and the polishing cloth.

In the case of the polishing apparatus 1 of FIG. 1, the polishing head 30 a and the polishing head 30 b are each provided with back pads 31 a and 31 b and support guides 32 a and 32 b and can support the side and back surfaces of the wafer W.

In addition, the polishing heads 30a and 30b can be rubber-grip-type polishing heads, and the support guides 32a and 32b and the support guides 32a and 32b and The contact pressure of the polishing cloth 3 can be controlled by controlling the pressure B (internal pressure) inside the second space portions 34a and 34b.

In the case of the polishing apparatus 1 of the present invention, the pressures A and B described above can be individually controlled by the pressure control mechanism 10a and the pressure control mechanism 10b separately provided in the polishing head 30a and the polishing head 30b. More specifically, as shown in FIG. 1, the pressure control mechanisms 10 a and 10 b can be constituted by first electro-pneumatic regulators 11 a and 11 b that control the internal pressure A (external pressure) of the first space portions 33 a and 33 b and The second electropneumatic regulators 12a and 12b that control the internal pressure B (external pressure) of the second space portions 34a and 34b, and the controllers 13a and 13b that send control signals to these electropneumatic regulators to control output power. Thereby, as shown in FIG. 2, the present invention can individually control the pressure A and the pressure B of each polishing head at each polishing head.

Furthermore, the rotation control mechanisms 20a and 20b may be the motors 21a and 21b that rotate the grinding heads 30a and 30b individually as shown in Figs. 1 and 2 and the controllers 22a and 22b that send control signals to these motors and control the rotation speed. Make up. In this way, as shown in Figure 2, the speed can be controlled for each grinding head.

Next, a wafer polishing method using the polishing apparatus 1 of the present invention will be described. In the wafer polishing method of the present invention, the polishing load of the plurality of polishing heads 30 is individually controlled in each polishing head by the pressure control mechanisms 10a and 10b and the rotation control mechanisms 20a and 20b provided in each polishing head. And the rotation speed, the wafer W is polished.

At this time, in particular, by controlling the polishing load at each polishing head, it is possible to control the difference in the processing amount distribution of the wafer W between the plurality of polishing heads 30, and to control the plurality of polishing heads by controlling the rotation speed of each polishing head. The processing amount of the wafer W among 30 wafers is different.

At this time, in the adjustment step as shown in FIG. 3, the grinding load and rotation speed of each grinding head can be individually controlled in such a manner that the difference in the machining amount distribution and the difference in the machining amount of each grinding head are made small.

First, a plurality of polishing heads are assembled (FIG. 3 (A)).

Next, the above-mentioned pressure A (external pressure), pressure B (internal pressure), and rotation speed were set to the same values in all the polishing heads (FIG. 3 (B)).

Next, the wafer is polished on all the polishing heads (FIG. 3 (C)). At this time, as described above, the pressure A and the pressure B, that is, the polishing loads are the same at all the polishing heads.

Next, the processing amount distribution of the polished wafer is calculated [(D) of FIG. 3]. The processing amount distribution can be calculated by measuring the flatness of the surface of the wafer before and after the polishing process with a planimeter.

Next, the external pressure and the internal pressure of each polishing head are adjusted based on the processing amount distribution [(E) of FIG. 3]. More specifically, the processing amount distribution of the wafers polished by each polishing head is individually calculated, and the external pressure and the amount of displacement of the processing amount are shifted away from the zero line (reference line) of the processing amount according to the processing amount distribution. The difference in internal pressure. As the zero line of the displacement of the processing amount, for example, the processing amount of the center portion of the wafer can be used as the zero line (reference line).

Next, the wafer is polished by all the polishing heads after adjusting the external pressure and the internal pressure [(F) of FIG. 3].

Next, the processing amount distribution of each polished wafer is calculated, and if the processing amount shift amount is close to zero, it ends with the adjustment of the internal pressure and the external pressure of each polishing head (FIG. 3 (G)).

Next, the processing amount in the screened polishing load was confirmed at each polishing head, and if there was a difference in the processing amount between the polishing heads, the rotation speed of the polishing head was adjusted [(H) in FIG. 3]. For example, the rotation speed of the grinding head with a small processing amount can be set to be large to increase the processing amount, and the processing amount difference can be made small.

Next, the wafer is polished on all the polishing heads whose over-speed is adjusted [(I) of FIG. 3].

Next, the processing amount distribution difference and the processing amount difference of the polished wafer are calculated. If these become sufficiently small, the polishing load and rotation speed of each polishing head are adjusted (FIG. 3 (J)).

In the above manner, by performing the grinding after adjusting the grinding load and the rotation speed of each grinding head, it is possible to reduce the difference in processing amount distribution and the processing amount.

[Example]

Hereinafter, the present invention will be described more specifically by presenting examples and comparative examples of the present invention, but the present invention is not limited to these examples.

(Example)

A silicon wafer is polished using a polishing apparatus 1 having two polishing heads 30a and 30b as shown in FIG. 1 and each of which has a pressure control mechanism and a rotation control mechanism. Such a polishing device is a device in which a pressure control mechanism and a rotation control mechanism are mounted on each polishing head of a single-sided polishing machine manufactured by Fujitsu Machine Industry Co., Ltd.

The polishing of the silicon wafer is performed as follows. First, according to the adjustment steps shown in FIG. 3, the polishing load and rotation speed of the two polishing heads 30 a and 30 b are set to values that reduce the difference in processing amount distribution and processing amount of wafers between the polishing heads 30 a and 30 b. As a result, the pressure difference between the internal pressure and the external pressure of the polishing head 30a was adjusted to 7.5 kPa and the rotation speed was adjusted to 33 rpm. Furthermore, the pressure difference between the internal pressure and the external pressure of the polishing head 30b was adjusted to 5.2 kPa, and the rotation speed was adjusted to 38 rpm.

The processing amount distribution of each polishing head before adjusting the polishing load [that is, the polishing load (the pressure difference between the internal pressure and the external pressure is 15 kPa) and the rotation speed (30 rpm) in all the polishing heads] is shown in FIG. In addition, the processing amount distribution of each polishing head after the adjustment after the final measurement in the adjustment step is shown in FIG. 5. In addition, FIGS. 4 and 5 and the “process amount shift amount” in FIG. 7 described below represent the shift amount from the reference line when the processing amount value at the center of the wafer is used as the zero line (reference line). As is clear from FIG. 5, the difference in the distribution of the machining amounts between the polishing heads can be reduced to almost zero.

The polishing ratio among the polishing heads before and after the adjustment of the polishing load and the rotation speed is shown in FIG. 6. After the grinding load and the rotation speed were adjusted in the embodiment, the grinding ratio was almost the same for each grinding head, so that the difference in processing amount could be eliminated between the grinding heads.

This grinding is performed after the grinding load and rotation speed are adjusted. The grinding conditions for this grinding are as follows:

[Polishing conditions]

Processed wafer: 300nm diameter P ^- product <100>

Abrasive cloth: secondary abrasive cloth

Abrasive: KOH-based silica sol

Number of grinding heads: 2

Number of polished wafers: 10 pieces for each grinding head

Furthermore, the ΔSFQR (max), ΔESFQR (max), and the processing amount of the silicon wafer after the polishing were measured. As a measuring device, a flat surface measuring instrument WaferSight 2 manufactured by KLA-Tencor Corporation was used.

(Comparative example)

The conventional polishing device shown in FIG. 12 is used to perform polishing of a silicon wafer in the same manner as in the embodiment. The conventional polishing device does not have a control mechanism and a rotation control mechanism for each polishing head, but all the polishing heads. All are ground with a uniform grinding load and speed.

In the comparative example, in order to reduce the difference in processing amount distribution and the difference in processing amount of the wafer between the two polishing heads 130a and 130b, the pressure difference between the internal pressure and the external pressure was adjusted to both the polishing heads. 5kPa. In addition, the rotation speed of the polishing head at this time is uniformly set to 30 rpm in any polishing head. The processing amount distribution of each polishing head at this time is shown in FIG. 7, and the processing amount is shown in FIG. 8. As can be seen from FIG. 7, the difference in processing amount distribution cannot be reduced as in the embodiment. Furthermore, it can be seen from FIG. 8 that the difference in processing amount becomes larger than in the example.

Next, the present polishing of the wafer and the measurement of ΔSFQR (max), ΔESFQR (max), and processing amount of the silicon wafer after the polishing were performed in the same manner as in the example. In the present polishing of the comparative example, the pressure difference between the internal pressure and the external pressure was 5 kPa and the rotation speed was 30 rpm for both the grinding heads.

The measurement results of ΔSFQR (max), ΔESFQR (max), and processing amount of the above examples and comparative examples are shown individually in FIGS. 9, 10, and 11.

In the example, compared with the comparative example, the difference between △ SFQR (max), △ ESFQR (max) and the processing amount becomes smaller. From this point, it can be confirmed that the grinding load can be reduced by controlling the grinding load and rotation speed of each grinding head The processing volume distribution of the wafers between the heads is poor and the processing volume is poor.

The present invention is not limited to the above-mentioned embodiments. The above-mentioned embodiment is an example, and anyone who has substantially the same structure and produces the same effect as the technical idea described in the patent application scope of the present invention is included in the technical scope of the present invention no matter what.

Claims (2)

A wafer polishing method uses a platform including a polishing cloth to which a polishing wafer is affixed and a support, and can simultaneously rotate the wafer and push the wafer to the polishing cloth while applying a polishing load to the wafer. A plurality of polishing heads, a grinding device that grinds the wafer supported by the polishing heads against the polishing cloth while rotating the polishing heads, and each of the polishing heads of the plurality of polishing heads has an individual A pressure control mechanism that controls the grinding load of the grinding head and a rotation control mechanism that controls the rotation speed of the grinding head. According to the pressure control mechanism and the rotation control mechanism provided on each grinding head, a plurality of each of the grinding heads are individually controlled. Grinding of the wafer by the grinding load and the rotation speed of the grinding head, by controlling the grinding load for each of the grinding heads, and controlling the difference in the processing amount distribution of the wafer between the plurality of grinding heads, and Since the rotation speed is controlled for each of the polishing heads, the difference in processing amount of the wafer between the plurality of polishing heads is controlled. The wafer polishing method according to claim 1, wherein the polishing head includes a back pad supporting a back surface of the wafer, a ring-shaped support guide supporting a side surface of the wafer, and the pressure control mechanism. It controls the contact pressure between the wafer and the polishing cloth supported by the polishing head as the polishing load, and the contact pressure between the support guide and the polishing cloth.