JP2020025010A - Spacer for wafer - Google Patents

Abstract

To provide a spacer for wafer maintaining the form even if the thickness of a polyether ether ketone film is 30 μm or less, and can be manufactured and handled easily.SOLUTION: A spacer 20 for wafer interposed between an adsorber 1 and a semiconductor wafer 10 includes a bottom board 21 of plane ring shape interposed between the porous table 5 of the adsorber 1 and the surface peripheral part 11 of the semiconductor wafer 10, and a mating wall 24 of plane ring shape laminated closely to the outer peripheral edge 23 of the reverse face of the bottom board 21 by heat press and mating with the positioning groove 4 of the case 2 of the adsorber 1. At least the bottom board 21, out of the bottom board 21 and the mating wall 24, is formed of polyether ether ketone film, and the thickness of the bottom board 21 is 30 μm or less. Even if the thickness of the bottom board 21 is 30 μm or less, the mating wall 24 having reinforcement function is laminated on the bottom board 21 and integrated, and thereby rigidity of the thin bottom board 21 is ensured at the time of handling, and the form can be maintained easily.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a wafer spacer used for back grinding of a semiconductor wafer or the like.

  When the wafer processing step (previous step) is completed, the semiconductor wafer is transferred to a dicing step for separating semiconductor chips individually, but the thickness is as thick as about 750 μm, which is not suitable for a semiconductor package which needs to be thinned as it is. Therefore, before the dicing process, the back surface is shaved in a back grinding process, and the thickness is reduced to 100 μm or less (see Patent Document 1).

When back grinding the semiconductor wafer, as shown in FIG. 5, first, a protective tape (also referred to as a back grinding tape) 14 is removably adhered to the surface of the semiconductor wafer 10 on which the circuit pattern is formed, and The vicinity of the periphery is aligned with the surface periphery 11 of the semiconductor wafer 10, the semiconductor wafer 10 is mounted on the suction device 1 of the back grinding device, and the protective tape 14 side thereof faces downward.
In FIG. 5, the suction device 1 and the protective tape 14 of the semiconductor wafer 10 are shown slightly separated for convenience of explanation.

  In most regions of the surface of the semiconductor wafer 10 except for the surface peripheral portion 11, an integrated circuit 12 is patterned as a circuit pattern, and a large number of bumps 13 connected to the integrated circuit 12 are formed so as to protrude. Are used as connection terminals for an external circuit board. Further, the suction device 1 includes, for example, a short case 2, a porous table 5 fitted into an opening on the front side of the case 2, and a vacuum connected to the porous table 5 via an exhaust pipe. The protective tape 14 of the semiconductor wafer 10 is in surface contact with the exposed surface of the porous table 5.

  When the semiconductor wafer 10 is mounted on the suction device 1 of the back grinding device, the protective tape 14 of the semiconductor wafer 10 is vacuum-sucked on the surface of the porous table 5 by operating the vacuum generator of the suction device 1 while supplying the chemical solution. After the back surface of the semiconductor wafer 10 is ground with a rotary grindstone and etched or polished to remove the damaged layer on the back surface of the semiconductor wafer 10, the semiconductor wafer 10 is removed from the porous table 5 of the suction device 1 and the protective tape on the front surface side is removed. If the semiconductor wafer 10 is peeled off, the semiconductor wafer 10 can be back ground and thinned.

  By the way, when a circuit pattern is formed on the surface of the semiconductor wafer 10, a difference in height occurs between the bumps 13 and the like of the circuit pattern and the peripheral edge portion 11. When vacuum-adsorbed to the table 5, the peripheral portion 15 floats from the surface of the porous table 5, and a gap G is generated between the peripheral portion 15 and the surface of the porous table 5. As a result, the attitude of the peripheral portion 15 of the semiconductor wafer 10 becomes unstable, and chipping may occur to damage the semiconductor wafer 10.

  Further, when a gap G is formed between the surface of the porous table 5 and the peripheral portion 15 of the semiconductor wafer 10, polishing dust and the like at the time of grinding flow into the holes of the porous table 5, and the porous table 5 is clogged. This may cause a decrease in the performance of the adsorption device 1. If the porous table 5 is clogged, the entire surface of the semiconductor wafer 10 cannot be uniformly vacuum-sucked, and the semiconductor wafer 10 may be displaced and hinder back grinding.

  In view of such a problem, conventionally, a planar ring-shaped wafer spacer 20A is interposed between the porous table 5 of the suction device 1 and the peripheral edge portion 15 of the semiconductor wafer 10, and the porous material is formed by the wafer spacer 20A. A method for filling a gap G between the surface of the table 5 and the peripheral portion 15 of the semiconductor wafer 10 has been proposed.

  As a material of the wafer spacer 20A, for example, a polyethylene terephthalate film (PET) having excellent transparency and strength can be cited, but if it is desired to obtain excellent solvent resistance, chemical resistance, dimensional stability, etc. Adoption of a small amount of polyetheretherketone film (PEEK) can be considered (see Patent Document 2).

JP 2012-020374 A JP 2000-212524 A

  When the material of the conventional wafer spacer 20A is a polyetheretherketone film, extremely excellent performance can be expected in a thermoplastic resin, but from the viewpoint of thinning, a thickness of 30 μm or less, particularly 10 μm or less is required. When this is done, the rigidity is poor, so it is not easy to maintain the form, and it becomes difficult to manufacture and handle.

  More specifically, when the thickness of the wafer spacer 20A is required to be 10 μm or less, if a thin polyetheretherketone film is to be manufactured, it will be broken, wrinkled, loosened, twisted, or the like. Also, during handling, the wafer spacer 20A is formed into a flat ring shape between the surface of the porous table 5 of the suction device 1 and the peripheral portion 15 of the semiconductor wafer 10 due to bending, wrinkling, loosening, twisting and the like. It is extremely difficult to set properly while maintaining

  The present invention has been made in view of the above, and even with a polyetheretherketone film having a thickness of 30 μm or less, it is intended to provide a spacer for a wafer which maintains a form, can be easily manufactured, or can be handled. I have.

In the present invention, in order to solve the above problems, when the precision wafer is sucked to the suction device, it is interposed between these suction device and the precision wafer,
An endless floor plate interposed between the mounting table of the suction device and the peripheral portion of the precision wafer, and a fitting wall provided in a part of the floor plate and fitted in a positioning groove of the suction device, and In the fitting wall, at least a sole plate is formed of a polyetheretherketone film, and the thickness of the sole plate is 30 μm or less.

In the suction device, a mounting table that detachably attaches a precision wafer to the case by vacuum suction is fitted into the case, and a positioning groove is formed in a recessed portion at an approaching point near the mounting table peripheral edge of the case.
The precision wafer is preferably a semiconductor wafer.
Further, the positioning groove and the fitting wall of the case of the suction device can be formed endlessly.
Further, it is preferable that the fitting wall is laminated by hot pressing at least near the outer peripheral edge of the floor plate.

  Here, the precision wafer in the claims includes at least various types of semiconductor wafers (for example, silicon wafers of φ150, 200, 300, and 450 mm), liquid crystal substrates, glass plates, and the like. The peripheral edge of the precision wafer includes at least the peripheral edge of the surface of the precision wafer and its vicinity, and the peripheral edge of the precision wafer. In addition, the suction includes vacuum suction and suction using static electricity.

  The base plate and the fitting wall are not particularly limited to be transparent, opaque, and translucent. The floor plate and the fitting wall can be formed in a ring shape, a frame shape, or the like according to the shape of the precision wafer. The thickness of the bottom plate and the fitting wall is preferably 1 μm to 30 μm for the bottom plate, and 40 μm to 200 μm for the fitting wall. The floor plate can be interposed between the mounting table of the suction device and the peripheral portion of the surface of the precision wafer and its vicinity.

  According to the present invention, even if the polyetheretherketone film of the floorboard is as thin as 30 μm or less, the floorboard is provided with a fitting wall having a reinforcing function. Can be maintained. In addition, since at least the sole plate of the sole plate and the fitting wall is a polyetheretherketone film, excellent heat resistance, solvent resistance, chemical resistance, abrasion resistance, slidability, dimensional stability, flame retardancy, etc. Can be expected.

  According to the present invention, an endless floor plate interposed between the mounting table of the suction device and the peripheral edge of the precision wafer, and a fitting wall provided on a part of the floor plate and fitted in the positioning groove of the suction device. Since at least one of the floor plate and the fitting wall is formed of a polyetheretherketone film, and the thickness of the floor plate is 30 μm or less, for example, a polyetheretherketone between the suction device and the precision wafer is included. Even if the film is as thin as 30 μm or less, there is an effect that the shape of the spacer for the wafer is maintained, and the film can be easily manufactured and handled.

  According to the second aspect of the invention, it is possible to appropriately set the wafer spacer between the mounting table of the suction device and the peripheral portion of the precision wafer while maintaining the endless shape. Further, since the fitting wall fits into the positioning groove of the case, it is possible to effectively prevent the wafer spacer from being displaced in the X and Y directions, and to stabilize the posture of the peripheral portion of the precision wafer.

  According to the third aspect of the present invention, since the positioning groove of the case of the suction device is formed endlessly in a ring shape, a frame shape, or the like, the positioning groove is easily formed. Further, since the fitting wall of the wafer spacer is formed endlessly in a ring shape, a frame shape or the like, simplification of the configuration of the fitting wall and easy formation of the fitting wall can be expected.

  According to the invention as set forth in claim 4, since the fitting wall is directly hot-pressed and laminated on the base plate, a sheet or the like for adhering these can be omitted, and the precision wafer is formed by the adhesive or the adhesive such as the sheet. Less pollution.

It is sectional explanatory drawing which shows typically the use condition in embodiment of the wafer spacer which concerns on this invention. It is a principal part expanded sectional view which shows typically the use condition in embodiment of the spacer for wafers concerning this invention. FIG. 3 is an explanatory rear view schematically showing an embodiment of the wafer spacer according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS It is sectional explanatory drawing which shows embodiment of the spacer for wafers concerning this invention typically. It is sectional explanatory drawing which shows the state which mounted the semiconductor wafer on the adsorption | suction apparatus, and the protection tape side faced downward.

  Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings. A wafer spacer 20 according to the present embodiment, as shown in FIG. 1 to FIG. A spacer 21 interposed between the porous table 5 of the adsorber 1 and the peripheral edge 11 of the semiconductor wafer 10 is a spacer interposed between the adsorber 1 and the semiconductor wafer 10. An upper and lower two-layer structure is provided with a fitting wall 24 that is provided on a part of the floor plate 21 and fits into the positioning groove 4 of the suction device 1, and at least the floor plate 21 of the floor plate 21 and the fitting wall 24 is made of polyether. The sole plate 21 is formed of an ether ketone film, and the thickness thereof is 30 μm or less.

  As shown in FIGS. 1 and 2, the suction device 1 includes, for example, a short case 2, a ceramic porous table 5 fitted into a mounting hole 3 on the front side of the case 2, A vacuum generator 7 is connected to the table 5 via an exhaust pipe 6, and the semiconductor wafer 10 is detachably vacuum-sucked on the porous table 5. The case 2 is formed in a planar circular box structure using a predetermined metal material (stainless steel, aluminum, or the like), and has a planar circular mounting hole 3 in the center on the front surface side. , A porous table 5 is fitted using an adhesive.

  A flat ring-shaped positioning groove 4 surrounding the mounting hole 3 is formed in the flat surface of the case 2, and the positioning groove 4 approaches the mounting hole 3 and the peripheral edge of the porous table 5. The positioning groove 4 is recessed in accordance with the width and height of the fitting wall 24 so as to appropriately fit with the fitting wall 24 of the wafer spacer 20.

  The porous table 5 is formed in a disc of alumina ceramic or the like capable of uniforming a large number of pore diameters, and a flat surface is uniformly exposed on the surface of the case 2 and the flatness of the surface is 5 μm or less. Is set to high accuracy. The peripheral edge of the porous table 5 is close to the positioning groove 4 of the case 2. The vacuum generating device 7 includes, for example, a vacuum pump and a compressor. The exhaust pipe 6 is connected to the center of the mounting hole 3 of the case 2 from below, and functions to generate a negative pressure in the porous table 5. .

  As shown in FIGS. 1 and 2, the semiconductor wafer 10 is made of, for example, a silicon wafer having a diameter of 300 mm or the like. A large number of bumps 13 connected to the integrated circuit 12 are formed so as to protrude, and the large number of bumps 13 serving as the projections function as connection terminals for an external circuit board. In such a semiconductor wafer 10, when the back surface is back-ground, a protective tape 14 is removably adhered to the front surface so that the periphery of the semiconductor wafer 10 is aligned with the front peripheral portion 11. 5 is in surface contact.

  As the protective tape 14, although not particularly limited, for example, a type in which an acrylic adhesive is applied to a polyethylene terephthalate film, a type in which the adhesive strength is significantly reduced by irradiation with ultraviolet rays, and the like are used.

  The base plate 21 of the wafer spacer 20 is formed in an endless planar ring shape by a polyetheretherketone (PEEK) film as shown in FIGS. 2 to 4, and the peripheral edge of the surface of the porous table 5 and the semiconductor wafer 10 are formed. It is interposed between the surface peripheral portion 11. The polyetheretherketone film of the floor plate 21 is formed by forming a polyetheretherketone resin, which is a thermoplastic resin, without stretching, so that the thickness is 30 μm or less, preferably 10 μm or less, more preferably 8 μm or less, and still more preferably. Is formed into a transparent thin film of 6 μm or less.

The physical properties of polyetheretherketone, which is a crystalline resin, are, for example, specific gravity 1.31, glass transition point / melting point 146/339 ° C., elastic modulus (MD) 3720 N / mm ² , elastic modulus (TD) 2940 N / mm ² , yield strength (MD) 80 N / mm ² , yield strength (TD) 75 N / mm ² , maximum strength (MD) 135 N / mm ² , maximum strength (TD) 83 N / mm ² , elongation at break ( MD) is 72%, elongation at break (TD) is 239%, dielectric strength is 16 kV / mm, dielectric constant is 3.30, dielectric loss tangent is 0.003, and water absorption (23 ° C., 24 hours) is 0.1.

  The polyetheretherketone film of the floor plate 21 has a melting point of 343 ° C. and a glass transition point of 143 ° C., and is stable up to 500 ° C. and has excellent heat resistance. Although concentrated sulfuric acid oxidizes but has no solvent to dissolve, it has excellent solvent resistance, is easy to ultrasonically seal, and can be welded or printed by laser. Since the floor plate 21 made of such a polyetheretherketone film is excellent in flame retardancy, has a low water absorption (0.05%), and has a high purity, no toxic gas is generated even if it is burned. Has features.

  The bottom plate 21 has an inner peripheral edge 22 formed along the surface peripheral edge 11 of the semiconductor wafer 10, and an outer peripheral edge 23 formed in a planar ring shape along the positioning groove 4 of the case 2 and the vicinity of the peripheral edge 15 of the semiconductor wafer 10. And has a predetermined width. Specifically, it is formed to have a length extending from the vicinity of the positioning groove 4 in the case 2 of the suction device 1 to the peripheral edge 11 of the porous table 5.

  As shown in FIGS. 1 to 4, the fitting wall 24 of the wafer spacer 20 is formed in an endless planar ring shape by a polyetheretherketone film, The semiconductor wafer 10 is pressed and laminated, and is fitted into the positioning groove 4 of the case 2 from above and approaches the vicinity of the peripheral portion 15 of the semiconductor wafer 10. The polyetheretherketone film of the fitting wall 24 is formed into a transparent film having a predetermined thickness by forming a polyetheretherketone resin, which is a thermoplastic resin, without stretching, as in the case of the floor plate 21. Is done.

  The thickness of the polyetheretherketone film of the fitting wall 24 is not particularly limited as long as it is thicker than the floor plate 21, but the mechanical strength of the wafer spacer 20 is ensured and the handling is easy. From the viewpoint of, for example, when the total thickness of the wafer spacer 20 is 100 μm, when the thickness of the mounting plate 21 is 30 μm, it is 70 μm or less, when the thickness of the mounting plate 21 is 10 μm, it is 90 μm or less, and when the thickness of the mounting plate 21 is 8 μm. In some cases, the thickness is 92 μm or less, and when the thickness of the floor plate 21 is 6 μm, the thickness is 94 μm or less. When the total thickness of the wafer spacer 20 is 50 μm, when the thickness of the mounting plate 21 is 10 μm, it is 40 μm or less, when the thickness of the mounting plate 21 is 8 μm, 42 μm or less, and when the thickness of the mounting plate 21 is 6 μm, 44 μm or less. Adjusted to thickness.

  In the above configuration, when manufacturing the spacer 20 for a wafer, first, a belt-shaped polyetheretherketone film for the fitting wall 24 is continuously extruded with a molten molding material containing a polyetheretherketone resin. , The long polyetheretherketone film is taken up by a winder, and the polyetheretherketone film is fed from the winder to another winder, and the polyetheretherketone film is continuously punched out. The flat ring-shaped fitting wall 24 is mass-produced quickly.

  Next, a polyetheretherketone film for the floor board 21 is continuously extruded into a belt shape using a molten molding material containing a polyetheretherketone resin, and the long polyetheretherketone film is wound up by a winder. While feeding out the polyetheretherketone film from this winder to another winder, the fitting wall 24 is directly hot-pressed and laminated on one side thereof, and then the fed polyetheretherketone film is formed into a flat ring shape. By continuously punching out, a large number of planar ring-shaped wafer spacers 20 can be rapidly manufactured.

  In this production, even if the polyetheretherketone film for the floorboard 21 is as thin as 30 μm or less, the polyetheretherketone film for the floorboard 21 and the fitting wall 24 thicker than the floorboard 21 are laminated and integrated, The rigidity of the polyetheretherketone film for the thin floor board 21 is ensured, and the shape can be easily maintained. Therefore, it is possible to prevent the wafer spacer 20 from being broken, wrinkled, loosened, twisted, or the like at the time of manufacturing. Further, since the fitting wall 24 is directly hot-pressed and laminated on one side of the polyetheretherketone film, an adhesive sheet for adhering them can be omitted, and the adhesive of the adhesive sheet causes contamination of the semiconductor wafer 10. Nothing.

  In addition, the polyetheretherketone film for the floor plate 21 is fed from the winding machine to another winding machine, and the polyetheretherketone film is fixed to a certain size (for example, A0, A1, A2, A4 size, B0, B1, B2, B4, etc.), and the fitting wall 24 is directly hot-pressed on one side thereof, and a polyetheretherketone film for the floor board 21 is punched into a flat ring shape to obtain a wafer spacer. 20 can also be manufactured.

  Next, when back grinding the semiconductor wafer 10, first, the protective tape 14 is removably adhered to the surface of the semiconductor wafer 10 on which the circuit pattern is formed. At the surface peripheral portion 11 or near the surface peripheral portion 11. Further, the wafer spacer 20 is positioned and arranged at the peripheral portion of the surface of the porous table 5 of the suction device 1 and the fitting wall 24 is fitted into the positioning groove 4 from above, and the semiconductor wafer 10 is placed on the surface of the porous table 5. With the protective tape 14 side facing downward, the bottom plate 21 of the wafer spacer 20 is positioned between the surface periphery of the porous table 5 and the surface periphery 11 of the semiconductor wafer 10 or the vicinity of the surface periphery 11. To intervene.

  After the wafer spacers 20 and the semiconductor wafers 10 are sequentially mounted on the surface of the porous table 5 of the suction device 1, the vacuum generator 7 of the suction device 1 is operated to place the wafer spacer 20 on the surface of the porous table 5. 21 is vacuum-adsorbed, the protective tape 14 of the semiconductor wafer 10 is vacuum-adsorbed, and the back surface of the semiconductor wafer 10 is ground with a rotary grindstone while supplying a chemical solution, and the damaged layer on the back surface of the semiconductor wafer 10 is etched or polished. After the removal, the semiconductor wafer 10 is removed and the protective tape 14 on the front side is peeled off, so that the semiconductor wafer 10 can be back ground and thinned.

  At this time, the gap G between the surface of the porous table 5 and the peripheral portion 15 of the semiconductor wafer 10 is filled with the wafer spacer 20, so that the posture of the peripheral portion 15 of the semiconductor wafer 10 is stabilized. In addition, there is no possibility that abrasive dust or the like at the time of grinding flows into the holes of the porous table 5 and the porous table 5 is clogged to cause a decrease in the performance of the adsorption device 1. Further, since the fitting wall 24 is fitted into the positioning groove 4 of the case 2, it is possible to effectively prevent the wafer spacer 20 from being displaced in the X and Y directions, and to adjust the posture of the peripheral portion 15 of the semiconductor wafer 10. It can be more stable.

  According to the above configuration, even if the floor plate 21 has a thickness of 30 μm or less, the fitting wall 24 having a reinforcing function is laminated and integrated with the floor plate 21, so that the rigidity of the thin floor plate 21 is ensured at the time of handling. Can be easily maintained. Therefore, breakage, wrinkles, loosening, twisting, and the like at the time of handling can be prevented, and the handling of the floor plate 21 becomes quite simple. Further, suppression of wrinkles, loosening, twisting and the like due to generation of static electricity can be expected.

  In addition, since at least the floor plate 21 of the floor plate 21 and the fitting wall 24 is a polyetheretherketone film, excellent heat resistance, solvent resistance, chemical resistance, abrasion resistance, slidability, dimensional stability, and flame retardancy are provided. And the like. Furthermore, there is no pinhole defect, and the electric resistance can be controlled in the range from conductive to semiconductive.

  In the above-described embodiment, the back grinding apparatus for back grinding the back surface of the semiconductor wafer 10 has been described. Alternatively, the back surface of the semiconductor wafer 10 may be ground with a rotating grindstone while rotating the suction device 1 and supplying the chemical solution. In the above embodiment, the suction device 1 of the back grinding device is shown, but another suction device 1 independent of the back grinding device may be used. Further, when the precision wafer is not the semiconductor wafer 10, the wafer spacer 20 can be formed into a plane frame shape or the like according to the shape of the precision wafer.

  A plurality of types of wafer spacers 20 having slightly different diameters can be prepared based on a slight dimensional tolerance of the semiconductor wafer 10. Further, in the above embodiment, the thick fitting wall 24 is laminated on the thin bottom plate 21 of the wafer spacer 20 later. However, the thick polyetheretherketone film is cut to cut the thin bottom plate 21 and the thick fitting wall 24. Can be integrated. Further, the fitting wall 24 may be hot-pressed on the polyetheretherketone film of the wafer spacer 20, but may be hot-pressed at a low temperature after plasma treatment.

  In addition, the floor plate 21 is interposed between the surface peripheral portion of the porous table 5 and the surface peripheral portion 11 of the semiconductor wafer 10, but is not limited thereto. The semiconductor wafer 10 may be interposed in the vicinity of the peripheral edge portion 11 or between the peripheral edge portion 15. Further, the fitting wall 24 of the wafer spacer 20 may be formed not of a polyetheretherketone film but of a polyethylene terephthalate film having excellent mechanical strength and the like.

  Further, the fitting wall 24 may be divided into a plurality of pieces, and the plurality of fitting walls 24 may be arranged and formed at predetermined intervals in the circumferential direction of the floor board 21. Further, an operating piece for handling may be projected outward from the outer peripheral surface of the fitting wall 24 in a radial direction. Further, the fitting walls 24 may be respectively hot-pressed and laminated near the outer peripheral edge 23 on the front and back surfaces of the floor board 21, and the outer peripheral edge 23 of the floor board 21 may be sandwiched between the pair of fitting walls 24.

  The wafer spacer according to the present invention is used in the field of semiconductor manufacturing and the like.

1 suction device 2 case 3 mounting hole 4 positioning groove 5 porous table (mounting table)
7 Vacuum generator 10 Semiconductor wafer (precision wafer)
11 Surface peripheral portion 13 Bump 14 Protective tape 15 Peripheral portion 20 Wafer spacer 21 Floor plate 22 Inner peripheral edge 23 Outer peripheral edge 24 Fitting wall G Gap

Claims (4)

When the precision wafer is sucked to the suction device, a wafer spacer interposed between the suction device and the precision wafer,
An endless floor plate interposed between the mounting table of the suction device and the peripheral portion of the precision wafer, and a fitting wall provided in a part of the floor plate and fitted in a positioning groove of the suction device, and A spacer for a wafer, wherein at least a floor plate of the fitting wall is formed of a polyetheretherketone film, and the thickness of the floor plate is 30 μm or less. In the suction device, a mounting table that detachably attaches a precision wafer to the case by vacuum suction is fitted into the case, and a positioning groove is formed in a recessed portion at an approaching point near the mounting table peripheral edge of the case.
2. The wafer spacer according to claim 1, wherein the precision wafer is a semiconductor wafer.   3. The wafer spacer according to claim 2, wherein the positioning groove and the fitting wall of the case of the suction device are formed endlessly.   4. The spacer for a wafer according to claim 1, wherein the fitting wall is laminated by hot pressing at least near an outer peripheral edge of the base plate.

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