JP2006100586A - Grinding method for laminate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grinding method for a laminate which can prevent a substrate from being damaged by fragments of a plate-like object occurring at the time of grind-cutting the plate-like object of a laminate which is made by joining the plate-like object to the substrate with an extremely narrow gap part left in-between. <P>SOLUTION: When grind-cutting the plate-like object by cutting with a grinding stone into the gap part of the laminate made by joining the substrate and the plate-like object with the gap part left in-between, a protection layer for the substrate is formed in advance in the gap part to prevent the substrate from being damaged by the fragments of the plate-like object occurring during the grinding operation. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for grinding a laminate, and more particularly to a grinding method for grinding and cutting a laminate having a hollow structure such as a chip size package (CSP) type solid-state imaging device.

  A solid-state imaging device composed of a CCD or a CMOS used for a digital camera or a mobile phone is increasingly required to be downsized. For this reason, the conventional large package in which the entire solid-state image sensor chip is hermetically sealed in a ceramic package or the like has recently been shifted to a chip size package (CSP) type having a size substantially equal to the size of the solid-state image sensor chip. .

  Under such circumstances, a spacer is formed on the transparent glass plate in correspondence with the position surrounding the light receiving portion of each solid-state imaging device formed on the wafer (semiconductor substrate), and a separation groove between adjacent ones is formed. On the other hand, a separation groove with the adjacent chip is also formed on the wafer, and this transparent glass plate is bonded to the wafer at the spacer portion to form a gap between the wafer, and then the transparent glass plate and the wafer are bonded. There has been proposed a method in which chemical mechanical polishing (CMP) is performed until the separation grooves are reached and separated into individual solid-state imaging devices. The width of the separation groove of the transparent glass plate is a width necessary for exposing a pad surface formed on the outside of the light receiving portion of the solid-state imaging device for performing wiring and the like from the outside (for example, Patent Documents). 1).

However, in the technique described in Patent Document 1, in order to separate the individual solid-state imaging devices, a step of forming separation grooves in advance on both the transparent glass plate and the wafer is necessary, and further by chemical mechanical polishing. Since the thickness is reduced until the transparent glass plate and the wafer are polished and reach the separation groove, there is a problem that the time for separation is long.
JP 2004-6834 A

  In order to solve such a problem, for example, using a dicing machine or the like, a disc-shaped grindstone (dicing blade) having a width necessary for exposing the pad surface of the wafer is used. A method is conceivable in which the transparent glass plate is ground and cut so as to pass through the gap portion, and then the wafer portion is ground and cut with another thin disc-like grindstone (dicing blade).

  However, in the case of a method of grinding and cutting using such a grindstone, for example, when the gap of the gap formed between the wafer and the transparent glass plate is as narrow as about 100 μm, FIG. As shown in FIG. 5 (b) showing the AA 'cross-section and a partially enlarged view of FIG. 5 (a), the glass fragments 12A generated during the grinding and cutting of the transparent glass plate 12 are removed when the grinding stone 52 is discharged. There is a serious problem that the wafer 11 is damaged by being caught in the gap between the wafer 11 and the wafer 11, being stirred, and being extremely dragged.

  The present invention has been made in view of such circumstances. For example, as in a solid-state imaging device, a laminate plate composed of a substrate and a plate-like object joined with an extremely narrow gap. An object of the present invention is to provide a method for grinding a laminated body, which can prevent a substrate from being damaged by plate-like fragments generated during grinding and cutting.

  In order to achieve the above object, according to the first aspect of the present invention, a plate-like object and a substrate are joined via a convex portion or a spacer formed on the plate-like object, and the substrate, the plate-like object, In the method of grinding a laminated body in which a gap portion is provided, the laminate is cut into the gap portion with a grindstone to grind and cut the plate-like material, a protective material is disposed in advance in the gap portion, and the substrate The protective layer is formed, and the plate-like material is ground and cut.

  According to the first aspect of the present invention, since the protective layer of the substrate is previously formed in the gap before grinding and cutting the plate-like material, even if the gap is extremely narrow, it occurs during the grinding and cutting of the plate-like material. The substrate is not damaged by debris.

  The invention according to claim 2 is characterized in that, in the invention according to claim 1, the protective layer is formed by filling the gap with a fluid material. According to the second aspect of the present invention, since the fluid material is filled in the gap, the protective layer can be easily formed even if the gap is extremely narrow.

  A third aspect of the invention is characterized in that, in the second aspect of the invention, the fluid material is filled in the gap under a reduced pressure environment. According to the third aspect of the present invention, since the fluid material is filled in the voids under a reduced pressure environment, the fluid material can be filled easily even in an extremely narrow void.

  The invention of claim 4 is characterized in that, in the invention of claim 2 or claim 3, the fluid material filled in the gap is cooled and solidified before the grinding. According to the invention of claim 4, since the fluid material is cooled and solidified before the grinding process, it functions as a good protective layer, and the substrate is damaged by debris generated during grinding and cutting of the plate-like object. There is no.

  The invention according to claim 5 is characterized in that, in the invention according to claim 4, the grinding is performed in a temperature environment below the melting point of the flowable material. According to the invention of claim 5, since grinding is performed in a temperature environment below the melting point of the flowable material, the solidified flowable material is ground while maintaining the solidified state, and the function as a protective layer is good. Maintained.

  The invention according to claim 6 is the invention according to claim 5, wherein the grinding is performed by placing the laminated body on a table having a cooling function. According to invention of Claim 6, since the table which mounts a laminated body has a cooling function, it can grind, maintaining the temperature environment below melting | fusing point of a fluid material.

  A seventh aspect of the invention is characterized in that, in the invention of the fifth or sixth aspect, a grinding liquid mixed with an antifreeze liquid is used in the grinding process. According to the seventh aspect of the present invention, since the antifreezing liquid is mixed with the grinding liquid, the grinding liquid does not freeze even in a low temperature environment, and good grinding can be performed.

  The invention according to claim 8 is characterized in that, in the invention of claim 2 or claim 3, the grinding is performed in a state where the laminate is immersed in the fluid material. According to the invention of claim 8, since the laminate is ground while being buried in the fluid material, the fluid material does not flow out of the gap during grinding, and the function as the protective layer can be maintained.

  According to a ninth aspect of the present invention, in the first aspect of the invention, before the plate-like object is bonded to the substrate, the protective material is applied to the surface of the plate-like object on the side where the gap is formed. It is characterized by that. According to the ninth aspect of the present invention, since the protective material is applied in advance to the surface of the plate-like object on which the void is formed before the plate-like object is bonded to the substrate, it is easy even if the gap is extremely narrow. A protective layer can be formed.

  As described above, according to the method for grinding a laminated body of the present invention, when the plate-like object of the laminated body in which the plate-like object and the substrate are laminated with a gap portion is ground and cut, the substrate is previously placed in the gap portion. Since the protective layer is formed and then ground and cut, the substrate is not damaged by debris generated during the grinding and cutting of the plate-like object even in a very narrow gap.

  Hereinafter, preferred embodiments of a method of grinding a laminate according to the present invention will be described in detail with reference to the accompanying drawings. In this embodiment, an application example of a CSP type solid-state imaging device to a manufacturing process will be described. In each figure, the same member is given the same number or symbol.

  Initially, the outline of the manufacturing process of the CSP type solid-state imaging device to which the grinding method of the present invention is applied will be described. FIG. 1 is an explanatory view showing a manufacturing process of a CSP type solid-state imaging device. As shown in FIG. 1B, a large number of solid-state imaging elements 11A are formed on a semiconductor substrate (wafer) 11 (corresponding to the substrate of the present invention).

  A general semiconductor element manufacturing process is applied to manufacture the solid-state imaging device 11A. The solid-state imaging device 11A includes a photodiode that is a light receiving element formed on the wafer 11, a transfer electrode that transfers excitation voltage to the outside, and an opening. Light shielding film, interlayer insulating film, inner lens formed on the upper part of the interlayer insulating film, color filter provided on the upper part of the inner lens via an intermediate layer, provided on the upper part of the color filter via an intermediate layer The microelements composed of microlenses and the like are arranged on a planar array.

  Since the solid-state imaging device 11A is configured in this way, light incident from the outside is condensed by the microlens and the inner lens and irradiated to the photodiode, so that the effective aperture ratio is increased.

  Further, as shown in FIG. 1B, pads 11B, 11B,... For wiring with the outside are formed outside the solid-state imaging device 11A.

  In the process shown in FIG. 1, a transparent glass plate 12 (corresponding to a plate-like object) is pasted on the wafer 11 on which the above-described solid-state imaging device 11A is formed, and the light-receiving portion of the solid-state imaging device 11A is sealed, The process of dividing into the solid-state imaging device 21 is represented conceptually.

  First, as shown in FIG. 1A, a spacer 13 made of silicon is formed on a transparent glass plate 12. The spacer 13 is formed by applying an adhesive 13A to the transparent glass plate 12 and bonding a silicon plate thereto. Next, a spacer 13 having a required shape is formed by using photolithography and dry etching technology, and finally, the adhesive 13B is transferred only to the spacer 13 portion.

  Next, the transparent glass plate 12 thus provided with the spacer 13 on one surface is bonded to the wafer 11 through the spacer 13. As a result, as shown in FIG. 1B, the solid-state imaging device 21 having a structure in which the gap portion 14 is provided between the wafer 11 and the transparent glass plate 12 and the light-receiving portion of the solid-state imaging element 11A is sealed is obtained at the wafer level. Thus, the laminate 20 formed in a large number is manufactured.

  Next, it cuts into the space | gap part 14 with the grindstone of about 0.6-1.2 mm in thickness, and only the transparent glass plate 12 of the laminated body 20 is grinding-cut, the division | segmentation of the transparent glass plate 12, and pad 11B on the wafer 11 , 11B,... Are exposed (FIG. 1C). Next, a portion between the pad 11B and the pad 11B of the wafer 11 is cut by grinding with a grindstone and divided into individual solid-state imaging devices 21 (FIG. 1D).

  Since the wafer 11 is typically a single crystal silicon wafer, the material of the spacer 13 is preferably a material having physical properties similar to those of the wafer 11 and the transparent glass plate 12, such as a thermal expansion coefficient. Is preferred.

  In the grinding and cutting process of the transparent glass plate 12 shown in FIG. 1C, the gap between the gap portion 14 between the wafer 11 and the transparent glass plate 12 is extremely narrow at about 100 μm due to the thinning of the solid-state imaging device 21. As described above with reference to FIGS. 5A and 5B, the glass fragments 12 </ b> A generated during the grinding and cutting of the transparent glass plate 12 are caught in the gap between the grindstone 52 and the wafer 11. It is scratched or dragged to damage the wafer 11 side. Therefore, the grinding method of the present invention is suitably used for the grinding and cutting step of the transparent glass plate 12.

  2 and 3 are conceptual diagrams illustrating the present invention. 2 and FIG. 3 is actually manufactured at the wafer level, but for the sake of simplification, only one grinding portion is illustrated. The same applies to FIGS.

  In the present invention, the gap portion 14 of the laminate 20 is filled with a fluid material (including a gel-like material) of the protective layer 15 that protects the wafer 11. For this purpose, the laminate 20 is dipped in a tray 81A filled with the fluid material of the protective layer 15 and kept in the vacuum chamber 81 decompressed by the vacuum pump 82 for a predetermined time. As a result, the air in the gap portion 14 of the laminate 20 is discharged, and the material of the fluid protective layer 15 is easily filled in the gap portion 14.

  Next, as shown in FIG. 3, the laminated body 20 is fixed on the wafer table 51 of the dicing apparatus, and is set at a position where the lowermost end of the cutting edge of the dicing blade (grinding stone) 52 slightly enters the gap portion 14. The transparent glass plate 12 is ground and cut. At this time, even if glass fragments 12A are produced while grinding and cutting the transparent glass plate 12, the protective layer 15 is present in the gap portion 14, so that the wafer 11 is not damaged.

  3A shows a cross-sectional view in a direction orthogonal to the grinding cutting direction, and FIG. 3B shows an A-A ′ cross-sectional view in FIG.

  Next, the wafer 11 is fully cut with another thin dicing blade, and finally the cleaning liquid is sprayed with a spin cleaner to remove the protective layer 15. The laminate 20 is ground and cut by attaching a dicing sheet (not shown) to the back surface of the wafer 11. Therefore, even if it is divided into individual solid-state imaging devices 21, it does not fall apart.

Next, the cutting depth of the dicing blade 52 from the upper surface of the transparent glass plate 12 with respect to the laminated body 20 having the thickness H ₁ = 500 μm of the transparent glass plate 12 and the thickness H ₂ of the spacer 13 = 100 μm. In the case of grinding and cutting at 530 μm (that is, the clearance H ₃ between the lowermost edge of the dicing blade 52 and the upper surface of the wafer is 70 μm), the protective layer 15 is deficient due to the rotational force of the dicing blade 52 or the injection of grinding fluid. An example that effectively functions as a protective layer of the wafer 11 will be described.

  In addition, as a common matter of the following examples, the vacuum degree of the vacuum chamber 81 when the fluid material of the protective layer 15 is filled in the gap portion 14 is about 5 to 80 kPa, and the dicing blade 52 has a particle size of 8 to 40 μm. The diamond abrasive grains were bonded to each other with a nickel-bonded metal blade having a diameter of 100 mm and a thickness of 1.0 mm, and the rotational speed was 4,000 to 6,000 rpm. Further, the feeding speed of the wafer table 51 was set to 0.2 to 1.0 mm / sec.

  The dicing blade 52 is a resin-bonded blade in which diamond abrasive grains are bonded with a phenol resin or the like. However, since the wear is fast, it is necessary to frequently adjust the height in order to secure the depth of cut, so a metal bond blade was used in the examples.

[Example 1]
The laminate 20 was dipped in a fluid material to be the protective layer 15, and the vacuum chamber 81 was used to fill the void portion 14 with the fluid material. The fluid material used was a solution containing gelatin or agar, and once cooled and solidified at a low temperature, the fluid material was hardly fluidized even if it was returned to a normal temperature environment.

  After filling the gap 14 with the fluid material, the laminate 20 was cooled in the refrigerator (about 4 to 8 ° C.), and the fluid material was solidified into a pudding to form the protective layer 15.

  Next, the laminate 20 was set in a dicing apparatus, and the transparent glass plate 12 was ground and cut under a normal temperature environment to expose the pads 11B, 11B,. When the processed laminate 20 is observed on a monitor screen using an observation optical system provided in the dicing apparatus, the surface of the wafer 11 due to the glass fragments 12A is found to have a large and deep scratch that breaks the circuit wiring. Furthermore, the number of scratches having a size of 10 μm or less was 10 or less per chip, which was well within the allowable range.

[Example 2]
The laminate 20 was dipped in a fluid material to be the protective layer 15, and the vacuum chamber 81 was used to fill the void portion 14 with the fluid material. The flowable material used was water or oil. In processing, the periphery of the wafer table 51 of the dicing apparatus is surrounded by a weir and filled with water or oil, and the laminated body 20 is soaked and fixed inside, and the transparent glass plate 12 is ground while being soaked at room temperature. It cut | disconnected and the pad 11B, 11B, ... was exposed.

  When the processed laminate 20 is observed on the monitor screen, the scratches on the surface of the wafer 11 are large and deep scratches that break the circuit wiring even though one or two scratches exceeding 10 μm are scattered per chip. It was not found, and there were about 10 scratches with a size of 10 μm or less per chip, which was within the allowable range.

[Example 3]
A silicon oil-based polymer solution frozen at 10 ° C. was used as the flowable material to form the protective layer 15, and the laminate 20 was immersed in this solution, and the gap portion 14 was filled using the vacuum chamber 81. In this state, the laminate 20 was stored in a refrigerator (about 0 to 6 ° C.), and the solution was frozen and solidified to form the protective layer 15.

  In addition, a table having a cooling function such as a freezing chuck table (table surface temperature of about 0 to 6 ° C.) was used as the wafer table 51 of the dicing apparatus, and the laminate 20 was chucked. Further, by supplying grinding water cooled to about 0 to 6 ° C., the laminated body 20 and its surroundings are kept below the melting point of the liquid, and the transparent glass plate 12 is ground and cut in this state, and the pad 11B, 11B was exposed.

  When the laminated body 20 after processing was observed on the monitor screen, scratches on the surface of the wafer 11 were not found to be over 10 μm in size, and only 2 to 3 scratches of 10 μm or less were scattered per chip. Met.

  The fluid material to be filled may be any material that solidifies at room temperature or lower. However, when a material that solidifies at a minus temperature such as water is used, the grinding water is mixed with ethylene glycol, which is an antifreeze, and minus. Prevents freezing even at temperatures and maintains liquidity.

[Example 4]
In this embodiment, unlike the first to third embodiments, the fluid material forming the protective layer 15 is not filled in the gap portion 14 in the vacuum chamber 81, but the spacer 13 is formed as shown in FIG. Before adhering the transparent glass plate 12 to the wafer 11, a fluid material that becomes the protective layer 15 is applied in advance to a portion that becomes the gap portion 14 of the transparent glass plate 12.

  In this case, the flowable material is a surfactant made of silicon, a surface protective agent made of silicate, or a photoresist, and has a high viscosity. Application may be by hand, but it is preferable to use a dispenser in order to uniformly apply a minute amount.

  Thereafter, the transparent glass plate 12 is bonded to the wafer 11 to form a laminated body 20, then the laminated body 20 is set in a dicing apparatus, and the transparent glass plate 12 is ground and cut in a room temperature environment, and the pads 11B, 11B, ... was exposed.

  When the processed laminate 20 was observed on the monitor screen, the surface of the wafer 11 was found to have no large and deep scratches that could break the circuit wiring, and there were 10 or less scratches of 10 μm or less per chip. It was well within the allowable range.

  As described above, according to the present invention, since the filler in the gap portion 14 functions as the protective layer 15 on the surface of the wafer 11, the surface damage of the wafer 11 due to the glass fragments 12 </ b> A during grinding and cutting can be reduced. .

  Further, since the filler is present under the transparent glass plate 12 to be processed, it also serves as a support for the transparent glass plate 12 at the time of grinding, so that the generation of the glass fragments 12A itself is suppressed, This leads to an effect of reducing the surface damage of the wafer 11.

  In the present invention, the material of the protective layer 15 filled in the gap portion 14 of the laminate 20 is not limited to the material used in the first to fourth embodiments, and various materials having similar physical properties are applied. be able to.

  Moreover, although the laminated body 20 which joined the transparent glass plate (plate-shaped object) 12 to the wafer (substrate | substrate) 11 via the spacer 13 was demonstrated, without using the spacer 13, the transparent glass plate (plate-shaped object) 12 is used. Even if it is the laminated body 20 which formed the convex part by etching etc., joined the transparent glass plate (plate-shaped object) 12 to the wafer (substrate) 11 by this convex part, and formed the space | gap part 14, The present invention can be applied very effectively like the laminate 20 with the spacers 13 interposed.

Explanatory drawing showing the assembly process of the solid-state imaging device which is an example to which the present invention is applied The conceptual diagram of the protective film formation process explaining embodiment of this invention The conceptual diagram of the grinding cutting process explaining embodiment of this invention The conceptual diagram of the protective film formation process explaining another embodiment of this invention Conceptual diagram explaining conventional grinding and cutting

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Wafer (substrate), 12 ... Transparent glass plate (plate-like object), 12A ... Glass fragment (fragment), 13 ... Spacer, 14 ... Gap, 15 ... Protective layer, 20 ... Laminate, 21 ... Solid-state imaging device 52 ... Dicing blade (grinding stone)

Claims (9)

A plate-like object and a substrate are joined via a convex portion or a spacer formed on the plate-like object, and a laminated body in which a gap is provided between the substrate and the plate-like object, to the inside of the gap In the method of grinding a laminated body in which the plate-like object is cut by grinding with a grindstone,
A method of grinding a laminate, wherein a protective material is disposed in advance in the gap to form a protective layer of the substrate, and the plate-like material is ground and cut.   The method for grinding a laminate according to claim 1, wherein the protective layer is formed by filling the gap with a fluid material.   The method for grinding a laminate according to claim 2, wherein the gap material is filled with the fluid material in a reduced pressure environment.   The method for grinding a laminate according to claim 2 or 3, wherein the fluid material filled in the gap is cooled and solidified before the grinding.   The said grinding process is performed in the temperature environment below the melting | fusing point of the said fluid material, The grinding process method of the laminated body of Claim 4 characterized by the above-mentioned.   6. The method for grinding a laminate according to claim 5, wherein the grinding is performed by placing the laminate on a table having a cooling function.   The method for grinding a laminate according to claim 5 or 6, wherein a grinding liquid mixed with an antifreeze liquid is used in the grinding process.   The grinding method for a laminate according to claim 2 or 3, wherein the grinding is performed in a state where the laminate is immersed in the flowable material.   The laminate according to claim 1, wherein the protective material is applied to a surface of the plate-like material on the side where the gap is formed before the plate-like material is bonded to the substrate. Processing method.

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