JP2005333100A - Support plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem in uniformity of wafer thickness by wafer polishing as variation of basic thickness is as large as about 30 to 50μm since a plate material of a plastic support plate is manufactured by an extrusion molding method. <P>SOLUTION: The support plate 5 (basic thickness:1mm, variation: within 1.8μm and bending elastic modulus: 9MPa) made from polycarbonate is slightly bent. A wafer 3 is stuck to an adhesion layer 4 from an end while an air layer between the wafer 3 and the adhesion layer 4 is removed. Air bubbles are prevented from remaining between the wafer 3 and the adhesion layer 4. The wafer 3 is stuck to the support plate 5 by making a polished face side up. Sticking objects of the wafer 3, the adhesion layer 4 and the support plate 5 are installed on a polishing face of a polishing grinding stone 15, and the wafer 3 is polished. Since the support plate is formed of synthetic resin, material cost can be reduced, and the support plate can be lightened compared to a plate formed of glass. Thus, the support plate can be enlarged. Damage due to falling at the time of conveyance or handling due to weight increase can be prevented. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a support plate for supporting a plate-like object such as a semiconductor wafer.

  2. Description of the Related Art In recent years, electronic devices with high performance, high functionality, and miniaturization are rapidly progressing, and there is an increasing demand for miniaturization and weight reduction of electronic components used in electronic devices. Accordingly, it is required that the thickness of the semiconductor chip is thinner, for example, 200 μm or less, further 100 μm or less, and uniform. In addition, the size of a semiconductor silicon wafer (hereinafter simply referred to as a wafer) tends to increase, and it is required to form a large number of semiconductor chips from a single wafer. In response to this requirement, since it is necessary to prevent cracks during processing, there is a method of supporting a wafer by using a relatively rigid support plate. For example, there is a method in which a glass support plate is used, an adhesive layer is formed on the surface of the plate, a wafer is adhered and fixed to the glass support plate through this, and the wafer is polished in this state. However, in this method, the basic thickness of the glass support plate greatly affects the wafer polishing accuracy, that is, the uniformity of the wafer thickness. Therefore, it is necessary to minimize the variation in the basic thickness of the support plate. At present, the basic thickness variation is required to be within 4 μm.

In Patent Document 1, a first plate having rigidity enough to stably support an object, a second plate fixed to the back surface of the first plate and contracted by heat at a predetermined temperature, and a first plate A wafer support plate composed of an adhesive layer formed on the surface of the wafer has been proposed. In this support plate, the first plate is made of plastic material, the second plate is made of heat-shrinkable tape, and the first plate and the second plate are fixed with a bond (registered trademark) agent. Yes. A support plate made of a plastic material is manufactured by a method of producing a plate material of a predetermined thickness by an extrusion method and then cutting it into a desired shape such as a circle or a polygon in order to reduce manufacturing costs. Yes.
Japanese Patent Application Laid-Open No. 2002-76101, particularly in the column of claims

  However, since the plate material of the conventional plastic support plate is manufactured by the extrusion molding method as described above, the variation in the basic thickness is as large as about 30 to 50 μm, so that the wafer thickness can be made uniform by wafer polishing. There was a problem.

  On the other hand, in the glass support plate, the basic thickness variation is maintained within 4 μm by polishing it, but the manufacturing cost of one sheet is very high, from several thousand yen to several tens of thousands of yen. In addition, since the weight of the support plate increases as the support plate becomes larger, it is difficult to handle the support plate in a state in which the wafer is stuck and fixed, and there is a possibility that the support plate falls during transportation and is damaged. Also, it is not easy to peel the wafer thinly formed by polishing from the glass support plate, and since the glass plate has a high bending elastic modulus and cannot be bent appropriately, the glass support plate should be bent forcibly. There was a problem that the plate was broken when trying to peel off.

The invention according to claim 1 is a support plate made of a hard or semi-rigid synthetic resin having a rigidity that can prevent the supported object from being deformed or broken by its own weight, A support plate having a basic thickness of ˜3 mm and a variation in the basic thickness within 2 μm.

Invention of Claim 2 is a support plate of Claim 1 whose bending elastic modulus is 1-40 GPa.

The invention according to claim 3 is the support plate according to claim 1 or 2, wherein the linear expansion coefficient is 1.0 × 10 ^{−5 to} 7.5 × 10 ⁻⁵ (1 / ° C.).

  Invention of Claim 4 is a support plate in any one of Claims 1-3 whose ultraviolet-ray transmittance is 30% or more.

  The invention according to claim 5 is the support plate according to any one of claims 1 to 4, which is used for silicon wafer polishing.

  According to the sixth aspect of the present invention, an annular groove having a depth of 10 to 300 μm on the upper surface of the plate is formed so as to surround the center portion of the plate, and the upper surface of the portion surrounded by the annular groove is higher than the upper surface of the outer peripheral portion of the groove. It is a support plate in any one of Claims 1-5 made low.

  The invention according to claim 7 is the support plate according to claim 6, wherein the upper surface of the portion surrounded by the annular groove is lower by 0.1 to 2 μm than the upper surface of the outer peripheral portion of the groove.

  The invention according to claim 8 is the support plate according to any one of claims 1 to 5, wherein the upper surface of the plate has a recess having a depth of 0.1 to 300 μm.

  The invention according to claim 9 is the support plate according to any one of claims 1 to 8 formed by an injection molding method or an injection compression molding method.

  In the first aspect of the present invention, the support plate is made of a hard or semi-hard synthetic resin. The material resin of the support plate is at least one selected from the group consisting of a thermoplastic resin, a thermosetting resin, and a photocurable resin. The thermoplastic resin is not particularly limited, but is preferably a polycarbonate resin, an acrylic resin, a polyethylene terephthalate resin, a liquid crystal polyester resin, or a liquid crystal polyester imide resin. These may be used alone or in combination of two or more. Can be used in combination. Examples of the thermosetting resin include phenol resin, melamine resin, and epoxy resin. As a photocurable resin, what mixed the low polymer of an epoxy acrylate, a reactive diluent, and a photoinitiator can be illustrated.

  The support plate is not limited in size and shape, and may be circular or polygonal, and preferably has a diameter corresponding to the shape of the wafer, for example, about 150 mm, about 200 mm, about 350 mm, or about 400 mm. It is a plate.

  The support plate has a composition sufficient to prevent a supported object, such as a wafer, from deforming or breaking due to its own weight.

    The basic thickness of the support plate is 0.5 to 3 mm, and the variation of the basic thickness is within 2 μm. As shown in FIG. 1, the basic thickness (1) refers to the thickness over the entire support plate (5). If the basic thickness (1) of the support plate (5) is less than 0.5 mm, the strength as the support plate is insufficient and cannot be put to practical use, and if it exceeds 3 mm, the handleability of the polishing apparatus is lowered.

    By setting the variation of the basic thickness (1) within 2 μm, the accuracy and uniformity of the thickness by wafer polishing can be maintained at the same level as the glass support plate. If this variation exceeds 2 μm, the accuracy and uniformity of the thickness due to wafer polishing will decrease. In order to make the variation of the basic thickness (1) within 2 μm, an injection molding method, an injection compression molding method, a hot press method, a method of polishing a synthetic resin plate, or the like can be employed.

In the second aspect of the invention, the flexural modulus of the support plate (5) is 1 to 40 GPa, preferably 2 to 9 GPa. In order to fix the wafer (3) to the support plate (5), the wafer (3) and the support plate (5) are adhered with an adhesive layer (4) interposed therebetween. ) And an adhesive layer (4). For this reason, the wafer (3) is usually adhered to the support plate (5) under vacuum conditions. In the second aspect of the invention, by setting the bending elastic modulus of the support plate (5) within the above range, as shown in FIGS. 2 and 3, the support plate (5) is slightly bent to adhere to the wafer (3). While expelling the air layer between the layers (4), the wafer (3) is stuck to the adhesive layer (4) from its end so that no bubbles remain between the wafer (3) and the adhesive layer (4). be able to. Thereby, the equipment for forming the said vacuum condition becomes unnecessary, and also the process time which adheres a wafer (3) to a support plate (5) can be shortened.

In the invention according to claim 3, the linear expansion coefficient of the support plate is 1.0 × 10 ^{−5 to} 7.5 × 10 ⁻⁵ (1 / ° C.), preferably 1.0 × 10 ^{−5 to} 4.0 ×. 10 ⁻⁵ (1 / ° C.). Frictional heat generated when the wafer is polished is transmitted to the support plate through the adhesive layer. At this time, if the linear expansion coefficient is larger than necessary, a stress occurs that the support plate expands and the wafer is deformed. However, when the linear expansion coefficient is in the range of 1.0 × 10 ^{−5 to} 7.5 × 10 ⁻⁵ (1 / ° C.), the wafer is not deformed and the wafer polishing accuracy, that is, the uniformity of the thickness is further increased. improves. Further, in a preferable linear expansion coefficient range of 1.0 × 10 ^{−5 to} 4.0 × 10 ⁻⁵ (1 / ° C.), a high pressure load is applied to the support plate in a polishing condition in which the grindstone is rotated at a high speed. Even when higher frictional heat is generated, a uniform wafer thickness can be stably obtained.

The material of the support plate having a linear expansion coefficient of 1.0 × 10 ^{−5 to} 7.5 × 10 ⁻⁵ (1 / ° C.) is not limited, but liquid crystal polymer, PC (polycarbonate resin), PMMA (polyethylene) Methyl methacrylate resin), PPS (polyphenylene sulfide resin), PEEK (polyether ether ketone resin), PI (polyimide resin), PBI (polybenzimidazole resin), PAI (polyamideimide resin), PEI (polyetherimide resin), etc. It may be. These materials may be used alone or in combination of two or more. A material having a linear expansion coefficient of 1.0 × 10 ^{−5 to} 7.5 × 10 ⁻⁵ (1 / ° C.) is more preferably a linear expansion coefficient of 1.0 × 10 ^{−5 to} 4.0 × 10 ⁻⁵ (1 / ° C. It is effective to add an appropriate amount of a material having a linear expansion coefficient of 1.0 × 10 ⁻⁵ (1 / ° C.) or less to the former material. The material having a linear expansion coefficient of 1.0 × 10 ⁻⁵ (1 / ° C.) or less is preferably a fibrous substance, and the shape of the fiber preferably has an aspect ratio of 1 to 500, and the cross-sectional shape of the fiber Is, for example, circular, the diameter is preferably 1 to 60 μm. Such a fibrous substance is not limited, but is made of, for example, glass, carbon, thermosetting resin, ceramic, or engineering plastic.

In the invention of claim 4, the ultraviolet transmittance is 30% or more, preferably 50% or more. In order to fix the wafer (3) to the support plate (5), the wafer (3) and the support plate (5) are adhered with an adhesive layer (4) interposed therebetween. As described above, when the wafer polishing is completed and the wafer (3) is peeled from the support plate (5), the support plate (5) is slightly bent (see FIG. 2 and FIG. 3), but the wafer (3) meat If the thickness is 50 μm or less, the wafer (3) may be damaged during peeling. In order to prevent such breakage, it is effective to use an adhesive tape (for example, self-peeling adhesive tape “Selfa” manufactured by Sekisui Chemical Co., Ltd. for processing ultra-thin wafers) that generates a gas by causing a chemical reaction with ultraviolet rays. Is. An adhesive layer is formed using such an adhesive tape, gas is generated by ultraviolet rays, and the wafer (3) can be easily and quickly separated from the support plate (5) by using the gas pressure. it can. Thus, in order to generate gas from the adhesive layer using ultraviolet rays, the ultraviolet ray region is set to 340 to 390 nm, and in this region, the transmittance is required to be 30% or more, and preferably 50% or more.

  In the sixth aspect of the present invention, an annular groove having a depth of 10 to 300 μm is formed on the upper surface of the support plate according to any one of the first to fifth aspects so as to surround the central portion of the plate, and is surrounded by the annular groove. The upper surface of the part is made lower than the upper surface of the outer peripheral part of the groove.

  In the case of manufacturing a molded product by the injection molding method or the injection compression molding method, as shown in FIG. 9, the runner (11) and the gate (12), which are resin paths, are connected to the molded product. As shown at 4, the gate (6) is left on the molded article. In order to use the molded product as a support plate, it is necessary to cut out the gate (6). Therefore, as a method of simplifying the excision of the gate (6), as shown in FIG. 4, an annular groove (2) is formed so as to surround the gate (6) at the center of the upper surface of the plate. As shown in FIG. 5, the gate (6) is cut off by grinding with a cutter, nipper, end mill, laser, etc., and the upper surface of the portion (9) surrounded by the annular groove (2) is the outer portion of the groove (2) ( 16) lower than the upper surface. The depth of the annular groove (2) is 10 to 300 μm. The width (7) of the annular groove (2) is preferably 30 to 1500 μm, and the size (8) of the ring is preferably 1.5 to 15 mm in diameter (outer diameter). Thus, by making the upper surface of the portion (9) surrounded by the annular groove (2) lower than the upper surface of the outer portion (16) of the groove (2), as shown in FIG. With an appropriate polishing pressure, the wafer can be polished thinly and uniformly without affecting the wafer polishing.

  The shape of the groove (2) is not limited, and the outer edge may be formed in a quadrilateral or other polygon as shown in FIG.

  In the production of the support plate by the injection molding method or the injection compression molding method, as shown in FIGS. 9 and 10, the gate (12) and the runner (11), which are runners, are constantly heated by the heater (10), and the mold is formed. When removing the support plate (5) from (17), a method of mechanically closing the gate (12) with the shut-off valve (13) and cutting the gate (12) and the runner (11) is also effective. When this method is used, it is not necessary to cut the gate (12) and the runner (11) by using a cutter or a nipper.

  According to a seventh aspect of the present invention, in the support plate according to the sixth aspect, the upper surface of the portion (9) surrounded by the annular groove (2) is 0.1 times higher than the upper surface of the outer portion (16) of the groove (2). It is made ~ 2 μm lower. That is, as shown in FIG. 11, when the support plate is arranged so that the surface having the annular groove (2) faces down, the lower surface of the portion (9) surrounded by the annular groove (2) The height (14) is 0.1 to 2 μm higher than the lower surface of the outer part (16) of 2). As shown in FIG. 7, when the polishing pressure is high when the polishing grindstone (15) is used, the annular groove (2) and its peripheral portion are bent, and the wafer thickness is uniform. In the worst case, the wafer may be damaged during polishing. Therefore, as described above, the gate (9) is arranged such that the lower surface of the portion (9) surrounded by the annular groove (2) is 0.1 to 2 μm above the lower surface of the outer portion (16) of the annular groove (2). 6) is excised. Thereby, even when the wafer is bent due to the polishing pressure at the time of wafer polishing, the bending width is suppressed to 0.1 to 2 μm at the maximum, so that the uniformity of the wafer thickness is not affected, and The wafer can be polished thinly and uniformly for any polishing pressure without causing damage to the wafer.

  In the invention according to claim 8, the support plate has a recess having a depth of 0.1 to 300 [mu] m at the center of one surface. When cutting the gate (6) generated by the injection molding method or the injection compression molding method, as shown in FIGS. 12 and 13, the gate (6) is shaved by cutting with a rudder or end mill, laser, or the like, and the support plate (5). A recess (18) having a depth of 0.1 to 300 μm is formed at the center of one side. For an appropriate polishing pressure, the support plate (5) functions effectively even with this depth.

  The support plate according to the invention is preferably molded by injection molding or injection compression molding. In the case of the extrusion molding method, it is necessary to produce a plate with a predetermined thickness and then cut it into a desired shape such as a circle or a polygon. In the injection molding method or the injection compression molding method, such a cutting operation is required. Therefore, the manufacturing process can be simplified.

  According to the first to ninth aspects of the present invention, since the support plate is made of a synthetic resin, the material cost can be reduced and the weight of the support plate can be reduced as compared with that made of glass. The support plate can be enlarged. Further, it is possible to prevent damage due to dropping during transportation or handling due to an increase in weight.

  According to the first aspect of the present invention, when the variation in the basic thickness is within 2 μm, the accuracy and uniformity of the thickness by wafer polishing can be maintained at the same level as that of the glass support plate.

  According to the invention described in claim 2, when fixing the wafer to the support plate, the support plate is slightly bent, and the wafer is adhered to the adhesive layer from its end while driving out the air layer between the wafer and the adhesive layer. It is possible to prevent bubbles from remaining between the adhesive layer and the adhesive layer. This eliminates the need for vacuum forming equipment and shortens the process time for attaching the wafer to the support plate. Also, when the wafer is peeled off from the support plate after polishing the wafer, the support plate can be bent appropriately, and the wafer can be easily peeled off from the support plate without damaging the support plate. .

  According to the third aspect of the present invention, thermal expansion due to frictional heat at the time of polishing can be suppressed, and since the linear expansion coefficient is close to that of glass, the support plate can be deformed under various polishing conditions. There is no. Therefore, the accuracy and uniformity of the thickness due to wafer polishing can be maintained at the same level as the glass support plate.

  According to the fourth aspect of the present invention, the wafer and the support plate can be peeled off easily and in a short time by generating gas from the adhesive layer with ultraviolet rays and utilizing the gas pressure. Therefore, even a wafer having a thin wafer thickness can be reliably peeled off from the support plate without damaging the wafer during peeling.

  According to the fifth aspect of the present invention, the effects of the first to fourth aspects of the invention described above can be obtained in wafer polishing.

  According to the sixth aspect of the present invention, the wafer can be polished thinly and uniformly without affecting the wafer polishing by an appropriate polishing pressure during the wafer polishing.

According to the seventh aspect of the present invention, even when the annular groove and its peripheral portion are bent at the time of wafer polishing, the bending width can be suppressed to 0.1 to 2 μm at the maximum, so that the wafer thickness is uniform. The wafer can be polished to a thin and uniform thickness with respect to any polishing pressure without affecting the wafer and without causing damage to the wafer.

  According to the invention described in claim 8, gate processing by an easy method such as a ruder, an end mill, or a laser is possible, and the manufacturing cost of the support plate itself can be greatly reduced.

  According to the ninth aspect of the invention, as in the case of the extrusion molding method, it is not necessary to produce a plate material having a predetermined thickness and then cut it into a desired shape such as a circle or a polygon. The process can be simplified. Also, the manufacturing cost can be greatly reduced to less than half the manufacturing cost of the glass support plate.

  Next, in order to describe the present invention specifically, examples of the present invention will be given.

Example 1
As shown in FIG. 2, the support plate (5) made of polycarbonate (basic thickness: 1 mm, its variation: within 1.8 μm, bending elastic modulus: 9 MPa) is slightly bent, and the wafer (3) and the adhesive layer (4) The pressure-sensitive adhesive layer (4) is stuck to the wafer (3) while expelling the air layer between the wafers (3) so that no bubbles remain between the wafer (3) and the pressure-sensitive adhesive layer (4). In this way, as shown in FIG. 3, the support plate (5) is bonded with the wafer (3) facing up to the surface to be polished. As shown in FIG. 7, the wafer (3) -adhesive layer (4) -support plate (5) adherent is placed on the polishing surface of the polishing grindstone (15) to polish the wafer (3).

It is a perspective view which shows a support plate. It is a perspective view which shows the state which adheres a wafer to a support plate through an adhesion layer. It is sectional drawing which follows III-III in FIG. It is a perspective view which shows the support plate before excising a gate. It is a perspective view which shows the support plate after excising a gate. It is sectional drawing which shows the support plate after excising a gate. It is sectional drawing which shows the state which grind | polishes the wafer. It is a perspective view which shows the other example of the shape of an annular groove. It is sectional drawing which shows the state which opens a shut-off valve in the metal mold | die which always heats a gate and a runner with a heater, and a molten resin flows. It is sectional drawing which shows the state which closed a shut-off valve in the metal mold | die which always heats a gate and a runner with a heater, and a molten resin does not flow in. It is sectional drawing which shows the support plate after excising a gate. It is a perspective view which shows the support plate before excising a gate with a luder. It is a perspective view which shows the support plate after cutting out a gate with a luder.

Explanation of symbols

1: basic thickness 2: annular groove 3: wafer 4: adhesive layer 5: support plate 6: gate 7: groove width 8: groove size 9: portion surrounded by annular groove 10: heater 11: runner 12: Gate 13: Shut-off valve 14: Height of the lower surface of the portion surrounded by the annular groove from the lower surface of the outer portion of the annular groove 15: Grinding stone 16: Outer portion 17: Mold 18: Recess

Claims (9)

A support plate made of a synthetic resin having a rigidity that can prevent the supported object from being deformed or broken by its own weight, and has a basic thickness of 0.5 to 3 mm, and has a basic thickness of A support plate having a variation of 2 μm or less. The support plate according to claim 1, wherein the flexural modulus is 1 to 40 GPa. The support plate according to claim 1, wherein the linear expansion coefficient is 1.0 × 10 ^{−5 to} 7.5 × 10 ⁻⁵ (1 / ° C.). The support plate according to claim 1, which has an ultraviolet transmittance of 30% or more. The support plate according to claim 1, which is used for polishing a silicon wafer. An annular groove having a depth of 10 to 300 μm is formed on the upper surface of the plate so as to surround the center portion of the plate, and the upper surface of the portion surrounded by the annular groove is lower than the upper surface of the outer peripheral portion of the groove. The support plate according to any one of 5. The support plate according to claim 6, wherein the upper surface of the portion surrounded by the annular groove is 0.1 to 2 μm lower than the upper surface of the outer peripheral portion of the groove. The support plate according to any one of claims 1 to 5, which has a recess having a depth of 0.1 to 300 µm on an upper surface of the plate. The support plate according to any one of claims 1 to 8, which is formed by an injection molding method or an injection compression molding method.

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