JP2007220887A - Universal chuck - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a universal chuck that facilitates high-accuracy grinding or polishing of the surface of a workpiece such as a semiconductor wafer. <P>SOLUTION: The suction plate 11 of the universal chuck is, for example, a porous body in which an inorganic material such as ceramics is sintered so as to form it into a disk shape and a large number of through-holes having ventilation are formed between an upper suction face of the suction plate and a lower sucking attraction face of the suction plate. Here, the through-holes are uniformly formed in the suction plate 11. A plurality of non-ventilations 11f are formed by filling the through-holes with a soft material. A disk-like ventilator 11a and annular ventilators 11b, 11c, 11d, and 11e are formed by dividing parts among the through-holes with the non-ventilators 11f. The suction plate 11 constitutes the universal chuck while being connected to an air suction system 16 through a chuck base body. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a universal chuck capable of reliably performing vacuum suction on workpieces having different sizes without replacing the chuck.

  Conventionally, for example, in the manufacture of semiconductor wafers, a porous body having a large number of through holes formed between its upper and lower surfaces is used as a vacuum chuck suction plate used in processing operations such as grinding and polishing. Has been. Such an adsorption plate is formed of a sintered body of an inorganic material such as ceramics or metal. Then, air is sucked from the suction surface side of the lower surface of the suction plate, and the workpiece is sucked and fixed to the suction surface side of the upper surface. In addition, the above-described processing operation is performed on a workpiece such as a semiconductor wafer having a different size without replacing the vacuum chuck that matches the size with a single vacuum chuck called a universal chuck.

  Various types of universal chucks have been proposed so far. A specific example of the mechanism will be described with reference to FIG. Here, FIG. 5A is a perspective view in which a part of the universal chuck is cut out, and FIG. 5B is a cross-sectional view taken along the line XX shown in FIG.

  As shown in FIGS. 5A and 5B, the universal chuck has a suction plate 101 and a chuck base 102, and the suction plate 101 is fitted to the chuck base 102. These are connected to an intake system 103 including a vacuum pump (not shown). The adsorption plate 101 is centered on a ventilation disk 101a made of porous ceramics, and has a plurality of ventilation annular plates 101b made of the same porous ceramics having the same axial center and the same height on the outer periphery of the disk. , 101c, 101d, 101e. A non-breathable partition wall 101f having a width of several millimeters and the same height as the above-described disk is arranged between the ventilation disk and the ventilation annular plate to constitute one disk as a whole.

  The chuck base 102 is provided with a recess 102a and annular grooves 102b, 102c, 102d, and 102e on its upper surface, and intake holes 104a, 104b, 104c, 104d, and 104e communicating with the chuck base 102, respectively. The intake holes 104a, 104b, 104c, 104d, 104e are connected to the intake pipes 105a, 105b, 105c, 105d, 105e of the intake system 103, respectively, and are vacuumed through the intake valves 106a, 106b, 106c, 106d, 106e. It communicates with the pump.

In such a universal chuck structure, a semiconductor wafer is placed on the upper surface, that is, the suction surface of the suction plate 101 made of porous ceramics. The air in the ventilation disk 101a and the ventilation annular plates 101b, 101c, 101d, and 101e constituting the suction plate 101 is caused by the recess 102a and the annular grooves 102b, 102c, and 102d of the chuck base 102 on the lower surface, that is, the suction surface. , 102e is sucked by a vacuum pump through the intake holes 104a, 104b, 104c, 104d, 104e, the intake pipes 105a, 105b, 105c, 105d, 105e and the intake valves 106a, 106b, 106c, 106d, 106e. The In such suction, the opening / closing of the intake valves 106a, 106b, 106c, 106d, and 106e is appropriately selected according to the size of the semiconductor wafer. The non-breathable partition wall 101f prevents suction from the vented annular plate outside the size of the semiconductor wafer.
JP 09-174364 A

  In the universal chuck so far, the ventilation disk and the plurality of ventilation annular plates are integrated by bonding with an adhesive of a material different from these to constitute an adsorption plate. The adhesive functions as the air-impermeable partition. Alternatively, in the adsorption plate, the ventilation disk, the plurality of ventilation annular plates, and the non-permeable partition are integrally sintered by the same ceramic base material. In the meantime, different holes are formed. Here, in the ventilation disk and the plurality of ventilation annular plates, as described above, a through hole having ventilation is formed between the upper surface and the lower surface thereof. On the other hand, in the non-breathable partition wall, the above-mentioned through hole does not exist, and in the non-breathable partition wall, there is no hole crossing the opposite side wall. As described above, the holes in the ventilation disk and the plurality of ventilation annular plates and the non-ventilated partition are formed so as to have different types and densities.

  However, in any of the suction plates, the elastic modulus is discontinuous between the ventilation disk and the ventilation annular plate as the adsorption part and the non-breathable partition wall as the non-adsorption part. For this reason, when a work piece such as a semiconductor wafer is adsorbed on an adsorbing plate, when the semiconductor wafer is placed across a plurality of adsorbing portions with an air-permeable partition interposed therebetween, in grinding or polishing, etc. When the pressing force is applied to the surface of the semiconductor wafer, the surface of the semiconductor wafer is locally deformed due to the difference in elastic modulus. And even if it was slight, there was a problem that, for example, the semiconductor wafer surface could not be processed with high precision due to this deformation. In particular, mirror polishing of an SOI (Silicon on Insulator) wafer formed by bonding two silicon wafers has been a serious problem because extremely high precision flatness is required.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a universal chuck that facilitates high-precision grinding or polishing of a workpiece surface such as a semiconductor wafer.

  In order to achieve the above object, a universal chuck according to the present invention includes a porous body adsorption plate on which a workpiece is adsorbed, a chuck base on which the adsorption plate is held, and the adsorption via the chuck base. In the universal chuck including the suction means communicating with the plate, the suction plate is an integral porous body in which a plurality of through holes having ventilation are formed between the upper surface and the lower surface, A material having a small elastic modulus is divided by a non-venting portion in which the through holes in a predetermined region are filled from the upper surface to the lower surface.

  According to the above invention, the ventilation portion and the non-vention portion of the suction plate are made of the same material, and the elastic modulus is exactly the same between them. For this reason, even when the workpiece is placed on the suction plate across a plurality of ventilation portions with a non-venting portion interposed therebetween, the pressing force of grinding or polishing is applied uniformly to the workpiece. Become. The surface of the workpiece is processed with high flatness and high accuracy.

  In the above invention, a material having a smaller elastic modulus than the porous body is impregnated, press-fitted or enclosed in the through-hole. In a preferred embodiment, the material having a low elastic modulus is a polymer material such as resin, rubber or elastomer.

  According to the configuration of the present invention, it is possible to provide a universal chuck that facilitates highly accurate grinding or polishing of a workpiece surface such as a semiconductor wafer.

  Preferred embodiments of the present invention will be described below with reference to the drawings. In the following embodiments, the case where the workpiece is a semiconductor wafer will be described, but the workpiece is not limited to this. Here, FIG. 1 is a plan view of a suction plate used in the universal chuck, FIG. 2 is a cross-sectional view of the suction plate, and FIG. 3 is an enlarged cross-sectional view of an enlarged region P in FIG.

  As shown in FIGS. 1 and 2, the adsorption plate 11 is a porous material in which an inorganic material such as ceramic is sintered and formed into a disk shape, and a large number of through holes are formed between the upper and lower surfaces. It is a sexual body. And in this adsorption | suction board 11, the disk-shaped ventilation part 11a and the annular | circular shaped ventilation | gas_flowing part 11b, 11c, 11d, and 11e are divided by several narrow annular | circular shaped non-venting part 11f.

  As shown in FIGS. 2 and 3, the suction plate 11 is made of an integral porous body, and has a large number of through holes 14 venting from the suction surface 12 that is the upper surface of the suction plate 11 to the suction surface 13 that is the lower surface. It has been drilled. Here, these through holes 14 are provided at a predetermined surface density on the adsorption surface 12. The non-venting portion 11 f is formed by filling the through holes 14 with a soft material 15. By filling or impregnating the soft material 15, the through hole 14 is closed and made non-ventilated, and becomes the non-venting portion 11 f of the suction plate 11. The ventilation portions 11 a, 11 b, 11 c, 11 d, and 11 e are not filled or impregnated with the soft material 15 and become suction portions of the suction plate 11. In addition, although there exists a part seen as the through-hole 14 has cut | disconnected in FIG. 3, this part is connected in the near side or back direction of the paper surface of FIG.

  Here, porous ceramics are suitable as the porous body. The porous ceramic is not particularly limited. For example, nitride ceramics such as aluminum nitride, silicon nitride, boron nitride, and titanium nitride; carbide ceramics such as silicon carbide, zirconium carbide, titanium carbide, tantalum carbide, and tungsten carbide. And oxide ceramics such as alumina, zirconia, cordierite, mullite and the like. Among these, silicon carbide having high thermal conductivity and excellent chemical resistance against hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, hydrofluoric acid, sodium hydroxide, and the like is preferable. When this silicon carbide is used, the thermal conductivity is high and the frictional heat generated by grinding or polishing is easily dissipated. Note that silicon-containing ceramics in which metallic silicon is mixed with the above ceramics, or ceramics bonded with silicon or a silicate compound can be used.

  And the average pore diameter of these porous ceramics should just be about 20 micrometers-50 micrometers. The porosity is not particularly limited, but may be about 20 to 40%. Here, when the porosity is less than 20%, the suction force of the workpiece is weakened, and the workpiece such as a semiconductor wafer may be moved or detached in the grinding or polishing process. And when a porosity exceeds 40%, the intensity | strength of the adsorption | suction board 11 will fall and it will become easy to destroy. Further, in order to keep the suction force of the suction surface 12 uniform, it is desirable that the surface density of the through holes 14 is uniform.

  And as the soft material 15 with which the said through-hole 14 is filled, it can select suitably from the material whose elastic modulus is smaller than the ceramics of the said base material. Here, as will be described later, the soft material 15 is preferably a polymer material that is easily sealed or press-fitted into the through-hole 14. Although it does not specifically limit as this polymeric material, For example, resin, rubber | gum, an elastomer, or a plastic is mentioned.

  The diameter of the suction plate 11 as described above may be about 100 mm to 400 mm, for example, when a semiconductor wafer is a workpiece. Further, the thickness of the suction plate 11 is appropriately determined in consideration of the thermal conductivity, Young's modulus, etc. of the material constituting the universal chuck for grinding and polishing. For example, when the adsorption plate 11 is made of silicon carbide, it may be about 20 to 50 mm.

  Next, a method for manufacturing the suction plate 11 configured as described above will be briefly described. First, an inorganic material such as the ceramic is sintered to form a disk having through holes 14. Here, the through-hole 14 ventilates from the upper surface to the lower surface of the disk. Therefore, for example, by using a technique in which a mask having a plurality of annular openings is coated on the upper surface of the disk and pressed from the upper surface and sucked from the lower surface, for example, thermoplastic resin is passed from the upper surface to the lower surface through the openings. It press-fits or encloses so as to fill the through hole 14. In this way, the required number of annular non-venting portions 11f are formed at desired locations on the suction plate 11.

  Examples of the thermoplastic resin include phenoxy resin, polyether sulfone resin, polysulfone resin, polyphenylene sulfone resin, polyphenylene sulfide resin, polyphenyl ether resin, polyether imide resin, thermoplastic polyimide resin, polytetrafluoroethylene resin, and the like. Is mentioned. In particular, the liquid crystal polymer is suitable because it has heat resistance. In addition, a thermosetting resin such as polyester resin or polyimide resin may be filled in the through holes 14 by press-fitting or sealing.

  After that, as shown in FIG. 2, a chuck base (not shown) for placing the suction plate 11 and an intake system 16 as an intake means are disposed as described in the prior art. The universal chuck of this embodiment is formed.

  Next, the effect of the universal chuck of this embodiment will be described with reference to FIG. FIG. 4 is a perspective view of the surface of the silicon wafer 17 after mirror polishing by the universal chuck using the suction plate 11 and the universal chuck when the conventional suction plate 101 is used. Here, FIG. 4A shows the case of this embodiment, and FIG. 4B shows the case of the prior art. As shown in FIG. 4A, in the present embodiment, the surface of the silicon wafer is completely smooth after mirror polishing, and the flatness is 10 nm or less. On the other hand, in the conventional case, as shown in FIG. 4 (b), the concavity and convexity traces of about 100 nm are concentrically transferred along the air-impermeable partition after the mirror polishing on the silicon wafer surface. Become.

  And, for example, after thermally oxidizing the surface of one silicon wafer that has been mirror-polished, it is bonded to another silicon wafer surface that has also been mirror-polished, so that the bonded SOI wafer has extremely high bonding strength and no unbonded portion. Can be manufactured. In such production, the yield in mass production of SOI wafer products is greatly improved and stabilized.

  In the above-described embodiment, the workpiece is placed on the suction surface of the suction plate 11, and the workpiece is processed by, for example, mirror polishing. Processing becomes possible. This is because the ventilation part and the non-ventilation part of the adsorption plate 11 are made of the same material, and the elastic modulus is exactly the same between them.

  As mentioned above, although preferred embodiment of this invention was described, embodiment mentioned above does not limit this invention. Those skilled in the art can make various modifications and changes in specific embodiments without departing from the technical idea and technical scope of the present invention.

For example, the surface shape of the suction plate may not be circular but may be various shapes according to the shape of the workpiece. The surface shape may be a rectangular shape, a polygonal shape, an elliptical shape, or a closed curved surface shape. In addition to the ceramic material, a metal material or a plastic material may be used as the base material of the suction plate. Moreover, a compressor, a water absorption means, etc. may be added to the universal chuck.

It is a top view which shows the suction plate of the universal chuck concerning embodiment of this invention. It is sectional drawing which shows the suction plate of the universal chuck concerning embodiment of this invention. It is an expanded sectional view showing the adsorption plate of the universal chuck concerning the embodiment of the present invention. It is a perspective view of the silicon wafer surface which shows the effect of the universal chuck concerning the embodiment of the present invention. It is a schematic diagram which shows the universal chuck concerning a prior art, Comprising: (a) is the perspective view which notched the part, (b) is the sectional view of the XX arrow.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Adsorption plate 11a, 11b, 11c, 11d, 11e Ventilation part 11f Non-ventilation part 12 Adsorption surface 13 Suction surface 14 Through-hole 15 Soft material 17 Silicon wafer 18 Concavity and convexity

Claims (3)

In a universal chuck comprising a porous body adsorption plate to which a workpiece is adsorbed, a chuck base on which the suction plate is held, and an intake means communicating with the suction plate through the chuck base.
The adsorbing plate is an integral porous body in which a plurality of through holes having ventilation are formed between an upper surface and a lower surface, and a material having a smaller elastic modulus than the porous body has the through holes in a predetermined region. A universal chuck characterized in that it is divided by a non-venting portion filled from the upper surface to the lower surface.   The universal chuck according to claim 1, wherein a material having a smaller elastic modulus than the porous body is impregnated, press-fitted, or sealed in the through-hole. The universal chuck according to claim 1 or 2, wherein the material having a smaller elastic modulus than the porous body is a polymer material of resin, rubber, or elastomer.

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