TWI731305B - Double-side polishing apparatus for a workpiece - Google Patents

Abstract

The present invention provides a double-side polishing apparatus for a workpiece, which is capable of performing double-side polishing of a wafer while measuring the thickness of the workpiece with high precision for a longer period of time than conventional techniques. In the double-side polishing apparatus 1 of the present invention, the upper fixed plate 2 or the lower fixed plate is provided with one or more through holes 10 penetrating from the upper surface of the upper fixed plate 2 or the lower fixed plate to the lower surface. A hole 11 is provided on the polishing pad 7 at a position corresponding to the through hole 10. The double-side polishing apparatus 1 further includes a workpiece thickness measuring device that measures the thickness of the workpiece W in the double-side polishing of the workpiece W. Each of the one or more through holes 10 is inserted into the solid window member 13, and the window member 13 is composed of a tubular portion 14 and a flange portion 15 having a diameter larger than the diameter of the through hole 10. The side surface 14a of the tubular portion 14 is provided with an annular recessed portion 14b. When the annular recessed portion 14b is placed with an O-ring 16, the tubular portion 14 is inserted into the through-hole 10 from the side of the polishing pad 7.

Description

Grinding device for both sides of workpiece

The invention relates to a double-sided grinding device for a workpiece.

A typical example of a workpiece to be polished, that is, in the manufacture of semiconductor wafers such as silicon wafers, in order to obtain higher-precision flatness quality or surface roughness quality of the wafer, it is generally used to polish both the front and back sides at the same time. step.

Especially in recent years, due to the miniaturization of semiconductor elements and the increase in diameter of semiconductor wafers, the flatness of semiconductor wafers during exposure has gradually been strictly required. Under such a background, it is necessary to finish polishing at an appropriate point in time. very important.

Against this background, Patent Document 1 describes a double-sided polishing device 100. As shown in Figure 1, the upper plate 91 (or the lower plate) is provided with a through hole 92, which can be passed through using a measuring mechanism (not shown). The hole 92 measures the thickness of the wafer W during polishing in real time.

In the above-mentioned double-side polishing device 100, the polishing surface of the upper and lower table is provided with a polishing pad 94 having a hole 93 having a diameter d3 larger than the diameter d1 of the through hole 92 at a position corresponding to the through hole 92; The diameter d1 of 92 is larger than the diameter d3 of the hole 93 of the polishing cloth 94 and the diameter d2 is smaller than the window material 95 of the thickness of the polishing cloth 94. The window material 95 is fixed to the upper plate 91 (or the lower plate) by the adhesive layer 96.

Advanced technical literature Patent Document 1: Japanese Patent No. 4654275

However, in the double-sided polishing apparatus 100 of Patent Document 1, the abrasive splashes and contacts the adhesive layer 96 during polishing, and then the layer 96 dissolves into the abrasive, which may cause the abrasive to flow into the through hole 92. If the abrasive flows into the through hole 92, the upper surface of the window material 95 will be atomized and the accuracy of the thickness measurement of the wafer W will deteriorate. In this way, since the abrasive flows into the through-hole 92, it is difficult to perform double-sided polishing of the wafer W while measuring the thickness of the wafer W with high accuracy over a long period of time.

The present invention is to solve the above-mentioned problems, and its purpose is to provide a double-sided grinding device for a workpiece, which can measure the thickness of the workpiece with high precision for a long period of time while simultaneously grinding both sides of the workpiece.

In order to solve the above-mentioned problems, the gist of the present invention is structured as follows. [1] A two-sided grinding device for a workpiece, comprising: a rotary fixed plate with an upper fixed plate and a lower fixed plate; a sun gear arranged at the center of the rotary fixed plate; an internal gear arranged on the outer peripheral portion of the rotary fixed plate; The bearing plate is arranged between the upper fixing plate and the lower fixing plate, and is provided with more than one holding hole for holding the workpiece, wherein the upper fixing plate or the lower fixing plate is provided with the upper fixing plate or the lower fixing plate. One or more through-holes penetrated from the surface to the lower surface, the polishing pad is provided with a hole at a position corresponding to the through-hole, and the double-side polishing device further includes a workpiece thickness measuring device, which can penetrate both sides of the workpiece during polishing The one or more through holes and holes are used to measure the thickness of the workpiece, and each of the one or more through holes is inserted into a solid window material. The window material will have a cylindrical portion and have a larger diameter than the through hole The cylindrical part is composed of a flange part having a diameter of φ, and the side surface of the cylindrical part is provided with an annular recessed part, and the cylindrical part is inserted into the through hole from the polishing pad side when the O-ring is arranged in the annular recessed part.

[2] In the double-sided polishing device described in [1], the cylindrical portion has a protruding portion protruding from the through hole having a length longer than the thickness of the upper platen or the lower platen, and the protruding portion is fixed by a member Fixed on the upper surface of the upper plate or the lower surface of the lower plate.

[3] In the double-sided polishing device described in [1] or [2], the bottom of the side wall of the upper plate that divides the through hole, or the side wall of the lower plate that divides the through hole A recess is provided on the top, and the flange of the window material is fitted into the recess.

[4] In the double-sided polishing device described in any one of [1] to [3], the polishing pad covers the outer peripheral portion of the flange portion.

According to the present invention, it is possible to grind both sides of the workpiece while measuring the thickness of the workpiece with high accuracy over a long period of time.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 2 shows an example of the double-sided polishing device of the workpiece according to the present invention. The double-sided polishing device 1 shown in this figure includes a rotary table 4, a sun gear 5, and an internal gear 6. The rotary table 4 has an upper plate 2 and a lower plate 3 facing it. The sun gear 5 is provided at the center of rotation of the rotary table 4. The internal gear 6 is provided in an annular shape on the outer peripheral portion of the rotary table 4. As shown in FIG. 2, the facing surfaces of the upper and lower rotary table 4, that is, the lower surface (grinding surface) of the upper table 2 and the upper surface (grinding surface) of the lower table 3 are respectively attached with polishing pads 7.

Furthermore, as shown in FIG. 2, this device 1 has a carrier plate 9 arranged between the upper platen 2 and the lower platen 3. The carrier plate 9 has one or more holding holes 8 for holding the workpiece W. In addition, in the example shown in the figure, this device 1 only has a carrying plate 9, but it can also have a plurality of carrying plates 9. In the illustrated example, the workpiece (wafer in this embodiment) W is held in the holding hole 8.

Here, by rotating the sun gear 5 and the internal gear 6 in this device 1, the carrier plate 9 can revolve and rotate to make planetary motions. That is, while supplying abrasive grains, the carrier plate 9 is moved planetarily, and the upper platen 2 and the lower platen 3 are rotated relative to the carrier plate 9 at the same time, thereby making the polishing pads attached to the upper and lower rotating platens 4 7 and the two sides of the wafer W held in the holding hole 8 of the carrier plate 9 can be polished at the same time.

In addition, as shown in FIG. 2, in the device 1 of this embodiment, the upper platen 2 is provided with one or more through holes 10 penetrating from the upper surface of the upper platen 2 to the lower surface (polishing surface). In the illustrated example, one through hole 10 is provided at a position passing through the vicinity of the center of the wafer W. In addition, in this example, the through hole 10 is provided in the upper platen 2, but it may be provided in the lower platen 3, and one or more through holes 10 may be provided in either the upper platen 2 and the lower platen 3. In the example shown in FIG. 2, one through hole 10 is provided, but a plurality of through holes 10 may be provided on the same circumference of the upper platen 2. Here, as shown in Figure 2, the polishing pad 7 attached to the upper platen 2 can also be penetrated by the hole 11 at a position corresponding to the through hole 10, so that the upper surface of the upper platen 2 penetrates to the polishing pad. 7 The state of the lower surface.

In addition, a workpiece thickness measuring device 12 is provided above the through hole 10, and the thickness of the wafer W can be measured in real time through the through hole 10 and the hole 11 during the double-sided polishing of the wafer W. In addition, the workpiece thickness measuring device 12 can be, for example, a wavelength-variable infrared laser measuring device. With such a measuring instrument, the interference of the reflected light on the surface of the wafer W and the reflected light on the back surface of the wafer W can be evaluated, and the thickness of the wafer W can be measured.

Then, in the double-sided polishing apparatus 1 of the present invention, the solid window material 13 is inserted into each of the through holes 10. As shown in FIG. 3, this window material 13 is composed of a cylindrical portion 14 and a flange portion 15 having a diameter greater than that of the through hole 10, and the cylindrical portion 14 and the flange portion 15 are formed integrally. In addition, the side surface 14a of the cylinder 14 is provided with a ring-shaped recess 14b. With the O-ring 16 arranged on this ring-shaped recess 14b, the cylinder 14 is inserted into the through hole 10 from the polishing pad 7 side, and the O ring 16 The through hole 10 and the cylindrical portion 14 are sealed. The window material 13 is fixed to the upper plate 2 (or the lower plate 3) by an adhesive layer (for example, double-sided tape) 17.

With such a window material 13, even if the adhesive layer 17 is eluted and the abrasive particles flow into the through hole 10, the cylindrical portion 14 of the window material 13 is inserted into the through hole 10. Therefore, the side surface 14a of the cylindrical portion 14 must be inserted into the through hole 10 for the abrasive to flow into the through hole 10. And the upper fix 2 (or lower fix 3). However, since the O-ring 16 is arranged in the annular recessed portion 14b of the cylindrical shape 14, even if the abrasive grains reach the O-ring, the upper surface 14c of the cylindrical portion 14 cannot be reached.

In this way, it is possible to prevent the flow of abrasive particles from flowing into the through hole 10 from deteriorating the accuracy of the thickness measurement of the wafer W, and it is possible to perform double-sided polishing of the workpiece W while measuring the thickness of the workpiece W with high accuracy for a longer period of time than in the conventional technique.

Also, as shown in Figure 4, the cylindrical portion 14 of the window material 13 may have a protruding portion 14d that is longer than the thickness of the upper platen 2 (or the lower platen 3) and protrudes from the through hole 10. The protruding portion 14d may The fixed member (for example, nut) 18 is fixed to the upper surface 2 a of the upper platen 2 (the lower surface of the lower platen 3 ). Thereby, the window material 13 can be strongly fixed to the upper platen 2 (or the lower platen 3), and the inflow of abrasive grains into the through hole 10 can be further suppressed. In this case, unlike the window material 13 shown in FIG. 3, the adhesive layer 17 is not required.

In the double-sided polishing apparatus 1 of the present invention, as shown in FIG. 5, it is preferable to provide a recessed portion 2b at the bottom of the side wall of the upper plate 2 (or the top of the side wall of the lower plate) defining the through hole 10. Considering such a structure, if the abrasive grains flow into the through hole 10, compared to the structure shown in Fig. 3, it is necessary to pass between the side surface 15a of the flange 15 and the side wall defining the recess 2b. Therefore, the abrasive grains can be further suppressed. Inflow. In particular, the depth of the concave portion 2b of the upper platen 2 is equal to the thickness of the flange portion 15 plus the thickness of the adhesive layer 17, and the lower surface 15b of the flange portion 15 and the lower surface 2c of the upper platen 2 (or the lower surface plate The upper surface of 3) is preferably formed on the same plane. Thereby, the window material 13 is arranged more stably, and double-sided polishing can be performed well.

Moreover, as shown in FIG. 6, it is preferable that the polishing pad 7 covers the outer peripheral portion 15c of the flange portion 15. Therefore, if the abrasive grains flow into the through hole 10, compared to the structure shown in Fig. 4, it is necessary to pass from the hole 11 of the polishing pad 7 between the polishing pad 7 and the outer peripheral portion of the lower surface 15b of the flange portion 15. The inflow of abrasive grains can be further suppressed. [Example]

(Conventional example 1) The thickness of a ^{silicon wafer (diameter: 300 mm, conductivity type: P −} , P ⁺⁺ ) was measured using the double-sided polishing apparatus 100 described in Patent Document 1 shown in FIG. 1. Specifically, the upper platen 2 is placed above the separated wafer W, and the wafer thickness measuring device 12 is placed at a position about 1 m away from the surface of the silicon wafer.

The surface of the silicon wafer W is irradiated with near-infrared light (wavelength: 1310nm) from the wafer thickness measuring device 12, and the reflection intensity caused by the interference of the light reflected from the surface of the silicon wafer W and the reflected light inside, passes through the silicon wafer. The interference fringe period obtained by the optical path difference information of the thickness of W is subjected to fast Fourier transform (FFT) to calculate the thickness of the silicon wafer W. At this time, the thickness is measured at approximately 10,000 locations in the center of the silicon wafer W, and as the window material 13, a material just after processing (that is, the service life = 0 minutes) is used. The calculated thickness is shown in Table 1.

[Table 1]

(Conventional example 2) In the same manner as conventional example 1, the thickness of the silicon wafer W was measured. Among them, as the window material 13, a material that has been polished on both sides for 10,000 points (that is, the service life=10,000 points) will be used. The other conditions are exactly the same as in conventional example 1. The results obtained are shown in Table 1.

(Conventional example 3) In the same manner as conventional example 1, the thickness of the silicon wafer W was measured. Among them, as the window material 13, a material that has been polished on both sides for 40,000 minutes (that is, the service life=40,000 minutes) is used. The other conditions are exactly the same as in conventional example 1. The results obtained are shown in Table 1.

(Invention Example 1) In the same manner as in the conventional example 1, the thickness of the silicon wafer W was measured. Among them, the double-sided polishing apparatus 1 of the present invention shown in FIGS. 2 and 3 will be used. The other conditions are exactly the same as in conventional example 1. The results obtained are shown in Table 1.

(Invention Example 2) In the same manner as in Conventional Example 2, the thickness of the silicon wafer W was measured. Among them, the double-sided polishing apparatus 1 of the present invention shown in FIGS. 2 and 3 will be used. The other conditions are exactly the same as those in conventional example 2. The results obtained are shown in Table 1.

(Invention Example 3) In the same manner as conventional example 3, the thickness of the silicon wafer W was measured. Among them, the double-sided polishing apparatus 1 of the present invention shown in FIGS. 2 and 3 will be used. The other conditions are exactly the same as those in conventional example 3. The results obtained are shown in Table 1.

>Evaluation of Wafer Thickness> As can be seen from Table 1, regarding conventional examples 1 to 3, compared with conventional example 1 with service life=0 minutes, the measured value of wafer thickness increases as the polishing time increases. In contrast, regarding the invention In Examples 1 to 3, the measured value of the thickness of the wafer is almost unchanged even if the polishing time is increased compared with the invention example 1 with the service life=0 minutes. In this way, according to the present invention, it is understood that it is possible to perform double-sided grinding of the workpiece while measuring the thickness of the workpiece with high accuracy for a longer period of time than in the conventional technique. [Possibility of industrial use]

According to the present invention, both sides of the workpiece can be polished while measuring the thickness of the workpiece with high accuracy over a long period of time. Therefore, it is quite useful in the semiconductor wafer manufacturing industry.

1‧‧‧Two-sided grinding device 2‧‧‧Upper Fix 2a‧‧‧Upper surface 2b‧‧‧Concave 2c‧‧‧Lower surface 3‧‧‧Place Fix 4‧‧‧Rotating plate 5‧‧‧Sun gear 6‧‧‧Internal gear 7‧‧‧Polishing Pad 8‧‧‧Keep hole 9‧‧‧Carrier plate 10‧‧‧Through hole 11‧‧‧hole 12‧‧‧Workpiece thickness measuring device 13‧‧‧Window material 14‧‧‧Tube 14a‧‧‧Side 14b‧‧‧Annular recess 14c‧‧‧Upper surface 14d‧‧‧Protrusion 15‧‧‧Flange 15a‧‧‧ side 15b‧‧‧Lower surface 15c‧‧‧peripheral part 16‧‧‧O ring 17‧‧‧Next layer 18‧‧‧Fixed member W‧‧‧Workpiece (wafer)

Fig. 1 shows the main part of a conventional double-sided grinding device for a workpiece. Fig. 2 shows an example of the double-sided polishing device of the workpiece according to the present invention. Figure 3 shows the main part of the double-sided polishing device shown in Figure 2. Fig. 4 shows the main part of another example of the double-sided polishing device for the workpiece according to the present invention. Fig. 5 is the main part of a preferred example of the double-sided polishing device for the workpiece according to the present invention. Fig. 6 is the main part of another preferred example of the double-sided polishing device for the workpiece according to the present invention.

2‧‧‧Upper Fix

7‧‧‧Polishing Pad

10‧‧‧Through hole

11‧‧‧hole

13‧‧‧Window material

14‧‧‧Tube

14a‧‧‧Side

14b‧‧‧Annular recess

14c‧‧‧Upper surface

15‧‧‧Flange

16‧‧‧O ring

17‧‧‧Next layer

Claims (4)

A two-sided grinding device includes: a rotary fixed plate with an upper fixed plate and a lower fixed plate; a sun gear arranged on the central part of the rotary fixed plate; an internal gear arranged on the outer periphery of the rotary fixed plate; a bearing plate arranged on the outer periphery of the rotary fixed plate; Between the upper plate and the lower plate, there are provided more than one holding hole for holding the workpiece, wherein the upper plate or the lower plate is provided with the upper plate or the lower plate penetrating from the upper surface to the lower surface The polishing pad is provided with a hole corresponding to the through hole. The double-sided polishing device further includes a workpiece thickness measuring device, which can penetrate the one or more through holes during the two-sided polishing of the workpiece. Holes and holes are used to measure the thickness of the workpiece. Each of the one or more through holes is inserted into a solid window material. The window material will consist of a cylindrical part and a flange part having a larger diameter than the through hole The cylindrical portion is provided with a ring-shaped recess on the side surface. When the ring-shaped recess is equipped with an O-ring, the barrel is inserted into the through hole from the polishing pad side, so that the flange portion of the window material The surface forms the same surface with the surface of the upper plate or the lower plate, and the polishing pad covers the outer peripheral portion of the flange portion. The double-sided grinding device described in the first item of the patent application, wherein the cylindrical portion has a protruding portion protruding from the through hole with a length longer than the thickness of the upper plate or the lower plate, and the protruding portion is fixed by a member Fixed on the upper surface of the upper plate or the lower surface of the lower plate. The double-sided polishing device described in the first item of the scope of patent application, wherein a concave portion is provided at the bottom of the side wall of the upper plate that divides the through hole, or at the top of the side wall of the lower plate that divides the through hole , The flange portion of the window material is fitted into the recessed portion. As the two-sided grinding device described in item 2 of the scope of patent application, the penetrating device is divided into A recess is provided at the bottom of the side wall of the upper plate of the through hole or at the top of the side wall of the lower plate defining the through hole, and the flange of the window material is fitted into the recess.

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