JPS59166460A - Wafer polishing equipment - Google Patents

Abstract

PURPOSE:To accurately polish one side of each of two wafers as a mirror surface and enhance the speed of the machining, by using a vacuum suction unit to turn the wafers as planets by a carrier while sucking the wafers on, to polish them between rotary surface plates. CONSTITUTION:When wafers 17, 18 are processed by plates 15, 16 of high flatness, the porous part 11 of a vacuum suction unit 10 is elastically deformed to push out internal gas from the part to make its internal pressure neagative to suck the wafers on the flat surfaces of the suction unit. The wafers 17, 18 are inserted into the through hole 26 of a carrier 2 and pushed on each other by an upper and a lower rotary surface plates 3, 4 having non-woven fabrics 5. The carrier 2 is rotated as a planet while a machining liquid containing free abrasive grains is supplied, so that one side of each wafer is polished as a mirror surface. After that, the wafers 17, 18 are put in a vacuum container to separate the wafers from the vacuum suction unit 10. According to this constitution, the wafers are accurately finished as mirror surfaces and the speed and efficiency of the machining are promoted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a wafer polishing apparatus that uses a double-sided polishing apparatus to polish one side of an extremely thin wafer with high precision.

[Prior art]

In order to mirror-polish a wafer with high precision, a polishing liquid containing minute abrasive grains is dispersed in a polisher with a high flatness, and a uniform pressure is applied to the entire surface of the wafer on this polisher. It is necessary to keep the relative speed variations small. As a means of applying pressure to the wafer, a method is used in which the wafer is fixedly held on a flat pressure (+1!l) plate with wax or sockless, etc., and polished with a polisher, but the flatness of the wafer is It depends on the identification accuracy, and has the drawback that it is not possible to obtain a flat surface that is better than the fixed accuracy, and polishing with sieve accuracy cannot be obtained.Therefore, double-sided polishing is performed without fixing the wafer on the pressure side and using the pressure side as a polisher. Devices have also been employed in the prior art.

FIG. 1 shows an example of this, in which an elastic nonwoven fabric 5 is bonded between an upper rotating surface plate 3 and a lower rotating surface plate 4 that face each other and is held on the thick plate part of the carrier 2. Two wafers 1 are interposed in a superposed manner. Furthermore, a processing liquid containing abrasive grains is supplied between the wafer 1 and the nonwoven fabric 5. Carrier 2 is
As will be explained later, the upper rotating surface plate 3 and the lower rotating surface plate 34, which rotate planetarily, pressurize the wafer 1 by means not shown. With the above configuration, the surface of the wafer 1 is mirror-polished by rotating the rotating shaft 8. However, at the same time, relative movement also occurs on the mating surfaces of the two wafers 1, resulting in wafer 1
Both sides are mirror polished. On the other hand, mirror polished wafer 1
Wafer 1 needs to be mirror-polished on only one side and the other side used as an operation surface for post-processing to prevent foreign matter from forming on the surface of wafer 1, damaging wafer 1 and impairing its function. It is said that Therefore, when both surfaces of the wafer 1 are mirror-polished, the upper and lower surfaces of the wafer 1 cannot be distinguished, and the above-mentioned problems occur in subsequent steps. As a means for preventing this, the method shown in FIG. 2 is adopted, but it has disadvantages such as insufficient force for holding the thin wafer 1 and difficulty in high-precision polishing.

That is, in FIG. 1, the upper rotating surface plate 3 and the lower rotating surface plate 4 are arranged side by side with their flat surfaces facing each other with an appropriate gap between them, and the opposing surfaces are covered with an elastic body as described above. A nonwoven fabric 5 is bonded. A rotating shaft 8 for rotating the upper rotating surface plate 3 and the lower rotating surface plate 4 is provided at the center of the upper rotating surface plate 3 and the lower rotating surface plate 4. Further, within the above-mentioned gap, a center gear 6 fixed to the rotating shaft 8 and a carrier 2 meshing with the outer periphery of the center gear 6 are provided. Further, the outer peripheral side of the carrier 2 meshes with an internal gear 7 surrounding the center gear 5.

Two wafers 1 to be overlapped are placed on the thick plate portion 2a of the carrier 2.
A hole is formed for inserting and holding. Further, in the upper rotating surface plate 3 and the nonwoven fabric 5 bonded thereto, (b) a large number of small holes 9 are formed that penetrate in the axial direction of the rotating shaft 8, and the small holes 9 are processed to contain abrasive grains by means not shown. liquid is supplied.

Further, a pressing force is applied to the upper (b) rotating surface plate 3 and the lower rotating surface plate 4 by means not shown. Therefore, the wafer 1 is pressurized by the upper rotating surface plate 3 and the lower rotating surface plate 4.

With the above configuration, the rotating shaft 8 is rotated, and the carrier 2 planetarily rotates the center gear 6. Therefore, one side of the wafer 1 that comes into pressure contact with the nonwoven fabric 5 is mirror polished. However, on the other hand, since the two sheets of Ueno 1 are simply polymerized, a relative displacement occurs in the mating surfaces of the two, and the above-mentioned machining fluid also infiltrates the mating surfaces, causing the mating surfaces to also be affected. Mirror polishing is performed, and as described above, both surfaces of the wafer 1 are often polished. Further, foreign matter gets mixed into the mating surfaces, causing defects such as scratches on the mating surfaces.

FIG. 2 shows another conventional technique in which the wafers 1 are not superimposed, but are held in stepped slots provided on the upper and lower surfaces of the carrier 2. It is. In this example, only one side of the wafer is mirror polished.
When the plate thickness of the carrier 2 becomes thinner, the level difference in the grooves of the carrier 2 that holds the carrier 2 becomes lower, which makes processing difficult and also causes the disadvantage that the wafer 1 may jump out of the groove during polishing and damage the wafer 1. arise.

FIG. 3 shows still another conventional technique, in which one wafer 1 is held on a carrier 2. In this method, both sides of the wafer 1 are polished to a mirror finish, and the thick part 2a of the carrier 2 is polished by increasing the pressing force of the However 1, which is thinner than the thickness of the wafer 1. If the machining speed is increased, a problem arises in that the tooth tips of the carrier 2 are broken.

[Purpose of the invention]

The present invention has been devised to solve the above-mentioned drawbacks, etc., and its purpose is to provide a wafer polishing apparatus capable of mirror-polishing only one side of a wafer with high precision and improving polishing speed and efficiency. Our goal is to provide the following.

[Summary of the invention]

In order to achieve the above object, the present invention provides a vacuum suction device having a flat surface that comes into contact with the mating surfaces of two wafers, and a vacuum suction means for vacuum suctioning the wafer to the flat surface; It has a thick part that is thinner than the overall thickness of the two wafers superimposed with a vacuum suction device interposed therebetween, and a through hole part for holding the two wafers is formed in this thick part. The present invention is characterized by a wafer polishing apparatus which includes a carrier, and rotates the wafer planetarily by the carrier while vacuum suctioning the wafer, thereby polishing the wafer to a mirror surface.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described based on the drawings.

Next, the outline of this embodiment will be explained with reference to FIGS. 4 and 5. In the figures, the same reference numerals as in FIGS. 1 to 3 indicate the same components or components with the same functions.

The wafers 17 and 18 are placed on top of each other via a vacuum suction device 10. A flat surface of a flat vacuum suction means 10 is in contact with each of the mating surfaces of the wafers 17 and 1B.

The flat surface of the vacuum suction device 10 is formed with high precision, and a large number of holes 11, which serve as vacuum suction means, are formed in the flat surface.

On the other hand, the thickness of the thick portion 2a of the carrier 2 is smaller than the total thickness of the two wafers 17 and 1B on which the vacuum suction device 10 is interposed. However, the total thickness of the wafer 17° 18 is thick due to the vacuum suction device 10 as described above, and even if a single wafer 17° 18 is thin, the carrier 2
can be formed to have a certain thickness or more.

A plurality of through holes 26 are formed in the thick portion 2a of the carrier 2, in which the stacked wafers 17 and 18 are held with the vacuum suction device 10 interposed therebetween.

From the above configuration, wafer 17. i8, a play with high precision flatness that is separately equipped) 15,1! When processed, the cavity 11 of the vacuum adsorption device 10 is elastically deformed, the gas in the cavity 11 is pushed out, and the cavity 11 becomes under negative pressure with respect to the atmosphere. Therefore, the wafers 17 and 1B are attracted to the flat surface of the vacuum suction device 10 due to the pressure difference between the atmospheric pressure and the cavity 11. The wafers 17 and 18 are inserted into the through hole 26 of the carrier 2 as shown in FIG.
One side of each wafer 17, 1B is polished to a mirror surface by planetary rotation of the carrier 2 while applying pressure with an upper rotating surface plate 3 and a lower rotating surface plate 4 having a rotary surface plate and supplying a machining liquid containing free abrasive grains. After the mirror polishing is completed, the wafers 17 and 18 are placed in a vacuum container (not shown), the pressure is set to low, the vacuum pressure in the cavity 11 is equidistant, and the wafers 17 and 18 are separated from the vacuum suction device 10.

As described above, highly accurate one-sided mirror polishing is performed.

Next, this embodiment will be explained in more detail.

As shown in FIG. 4, the two wafers 17 and 18 are stacked on top of each other with the vacuum suction device 10 interposed therebetween, and as described above, the thickness of the vacuum suction device 10 and the thickness of the wafers 17 and 17 are the same.

The carrier 20 is inserted into and held in the through-hole portion 26 forming the thin-thickness portion 2a, which is thinner than the total thickness including the total thickness of 1.8 mm. The polished surfaces of the wafers 17 and 18 on the side opposite to the vacuum suction device 10 are pressed against the nonwoven fabric 5 of the upper rotating surface plate 3 and the lower rotating surface plate 4.

As shown in FIG. 6, the vacuum suction device 10 includes a polyurethane foam plate 12 forming a highly precise flat surface with a uniform thickness, and a large number of fine holes 11 formed on the flat surface above and below the polyurethane foam plate 12.
It consists of The cavity portion 11 has a narrowed inlet portion, and
The inlet portion is formed from a hollow portion extending inside, and the inlet portion has an opening diameter of 10 to 25 μm, and the hollow portion has a diameter of 50 μm to 150 μm, and a hole height of 100 to 300 μm. Ru.

As shown in FIG. 5, one side of the wafer 17 and 18 is brought into contact with the above-mentioned flat surface of the vacuum suction device 10, and a plate 15 and 16 forming a highly accurate flat surface is brought into contact with the other side, and a process (not shown) is applied. When pressurized uniformly by pressure means, as mentioned above,
The hollow part of the hole part 11 is elastically deformed, and the gas in the hollow part is pushed out from the minute gap where the wafer 17. Become. Therefore, the wafers 17 and 18 are held by suction on the flat surface of the polyurethane foam board 12 due to the difference between the atmospheric pressure and the negative pressure of the cavity 11. As a result, wafers 17 and 18
and the polyurethane foam board 12 are integrally formed. The wafers 17 and 18 formed in one piece are inserted into the through holes 26 of the carrier 2 and held as shown in FIG. On the other hand, as described above, since the thick part 2a of the carrier 2 is formed thinner than the total thickness of the wafers 17 and 18 formed in one piece, the polished surfaces of the wafers 17 and 18 are
It is held in such a way that it protrudes from the surface of the

In the above state, when the center gear 6 is rotated and the upper rotating surface plate 3 and lower rotating surface plate 4 are rotated, the carrier 2 rotates planetarily, and along with this, the wafer 17° 18, the upper rotating surface plate 3, etc. A relative movement occurs between the wafers 17 and 18, and only one side of the wafer 17, 18 is mirror polished. After polishing, the material is placed in a vacuum container and separated as described above.

As described above, the carrier 2 is formed to be slightly thinner than the sum of the thickness of the wafers 17 and 18 plus the thickness of the polyurethane foam board 12, but it is formed thicker than in the prior art, so it has rigidity. Therefore, the polishing speed can be increased. Further, as described above, since two wafers can be mirror-polished at the same time, processing efficiency can be improved. Further, since abrasive grains do not intervene on the non-polished surfaces of the wafers 17 and 18, and foreign matter cannot enter, defects such as scratches are prevented from occurring.

7 and 8 show another embodiment.

The vacuum suction device 10 is composed of an elastic rubber plate 13 forming a highly accurate flat surface with a uniform thickness, and a large number of pinholes 14 formed through the elastic rubber plate 13 in the thickness direction.

The pinhole 14 has a diameter of 10 and a small hole of 50 μm.
They are arranged at approximately equal intervals of 0 to 20 μm.

As shown in FIG. 7, one side of the wafers 17 and 18 is brought into contact with the flat surface of the elastic rubber plate 13 in the same manner as in the embodiment described above, and pressure is applied by the plates 15 and 16 (not shown). As in the embodiment, negative pressure is maintained in the pinhole 14, and the wafers 17 and 18 are attracted to the elastic rubber plate 13. As described above, single-sided mirror polishing with high C:% accuracy can be obtained.

Yet another embodiment is shown in FIG.

The vacuum suction device 10 includes a parallel disk 19 forming a highly accurate flat surface with a uniform thickness, a large number of grooves 20 formed on the flat surface of the parallel disk 19, and a connection between the grooves 20 and the atmosphere side. A hole 21 formed in the parallel disk 19 to communicate with the hole 2
A pipe 22 is detachably connected to a vacuum pump 25 serving as a vacuum source, and a steel ball 24 provided between the hole 21 and the pipe 22 and subjected to a corrosion-resistant treatment and an elastic resin film in contact with the steel ball 24 are provided between the hole 21 and the pipe 22. 23, and a check valve formed from 23. The parallel disk 19 is made of stainless steel plated with hard gas or dense ceramic to prevent scratches on the wafer.

・12・ Next, the operation of this embodiment will be explained.

As in the above embodiment, one side of the wafer 17, 1B is brought into contact with the flat surface of the parallel disk 19. Next, when the vacuum pump 25 is activated, the concave groove 2
0 becomes a vacuum state. Therefore, the wafers 17 and 18 are attracted to the flat surface of the parallel disk 19. Next, parallel disk 1
Remove the piping 22 from 9. Atmospheric pressure is applied to the steel ball 24 of the check valve, and the groove 20 and hole 21 of the parallel disk 19 are under negative pressure, so the steel ball 24 is pressed toward the elastic resin film 23. Ru. Therefore, the vacuum inside the parallel disk 19 does not leak, and the wafers 17 and 18 are held by suction on the parallel disk. Next, the wafer 17,1 integrated with the parallel disk 19
B is placed between the upper rotary surface plate 3 and the lower rotary surface plate 4 in the same manner as in the above embodiment, and one side of the wafers 17 and 18 is mirror-polished.

After mirror polishing, the wafers 17 and 18 are placed in a vacuum container in the same manner as described above, and the internal pressure of the parallel disk 19 is set to negative pressure on the outside air side, thereby separating the wafers 17 and 18 from the parallel disk 19.

In the above embodiment, the diameter of the parallel disk 19 is the same as that of the wafer 1.
Since the diameter of the parallel disk 19 can be larger than that of the carrier 2, it is only necessary to hold the parallel disk 19 in the through hole 26 of the carrier 2. Therefore, the outer circumferential sides of the wafers 17 and 18 do not come into contact with the carrier 2, and damage to the outer circumferences is prevented.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, only one side of a wafer can be mirror-polished with high precision, and the polishing speed and efficiency can be improved.

[Brief explanation of the drawing]

1 to 3 are cross-sectional views showing conventional polishing means using a double-sided polishing device, FIG. 4 is a cross-sectional view showing an embodiment of the present invention, and FIG. 5 is a sectional view of a wafer according to an embodiment of the present invention. An explanatory sectional view showing the means for adsorbing X nitrogen to the nitrogen adsorption device, FIG.
FIG. 7 is a cross-sectional view showing the state of engagement between a wafer and the vacuum suction device according to another embodiment; FIG.
This figure is a sectional view showing the vacuum suction device of FIG. 7, and FIG. 9 is a sectional view showing a vacuum suction device of still another embodiment. , go to 1. 1.17, 18 river wafer, double carrier, 2a...thick part, 3...upper rotating surface plate, 4...lower rotating surface plate, 5.
...Nonwoven fabric, 6...Center gear, 7...Internal gear, 8
... Rotating shaft, 9 ... Small hole, 10 ... Vacuum suction device, 11 ... Hole part, 12 ... Polyurethane foam board,
13... Elastic rubber plate, 14... Pinhole, 15.
1! ...Plate, 19...Parallel disk, 20...
Concave groove, 21... Hole, 22... Piping, 23... Elastic resin membrane, 24... Steel ball, 25... Vacuum pump,
26...Through hole section. Figure 1 f2 Figure 3 Figure 6 Figure 4 Figure 6/1 Figure 5 Figure 8 0 Off view

Claims (1)

[Scope of Claims] 1. A pair of rotating surface plates provided opposite to each other by bonding an elastic non-woven fabric to opposing surfaces; A carrier that meshes with a center gear fixed to a shaft and an internal gear surrounding it to rotate planetarily and forms a thick plate portion that holds a wafer, and abrasive grains that are supplied between the nonwoven fabric and the wafer. In a wafer polishing apparatus that polishes the wafer with a processing liquid containing
A vacuum suction device having a vacuum suction means that forms a flat surface that comes into contact with each of the mating surfaces of the two wafers and vacuum suction means for vacuum suctioning the wafer to the flat surface side, and the vacuum suction device is interposed. The carrier is provided with the carrier forming the thick plate portion which is thinner than the total thickness of the two stacked wafers, and forming a through hole portion in the thick plate portion for holding the stacked wafers. A wafer polishing device characterized by: 2. The vacuum suction device is characterized in that it is formed from a flat polyurethane foam plate or elastic rubber plate with a uniform thickness, in which a large number of fine holes are formed on both flat surfaces. A wafer polishing apparatus according to claim 1. 3. The vacuum suction device forms a large number of grooves on both surfaces of a parallel plate made of hard chrome plating on the surface of a stainless steel plate of uniform thickness, or a parallel plate made of ceramic, and A hole is formed that communicates with the groove and opens to the outside air, and a pipe that communicates with a vacuum source is removably engaged with the hole through a check valve. The first claim characterized in that
The wafer polishing apparatus described in .