JP2008073832A - Grinding wheel for manufacturing thin wafer and grinding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grinding wheel which is used for grinding a silicon wafer and other materials acquired for slicing, has good cutting ability and high cutting efficiency and can provide high quality surface finishing without giving any damage on the ground material, and also to provide a grinding method having economical effects. <P>SOLUTION: A groove 9 and uneven patterns are formed on a diamond film section of the ring-shaped or disk-shaped grinding wheel which has the diamond film 7 as an abrasive layer, by a CVD method. Ridge sections of inner and outer peripheries or an outer periphery of the abrasive layer of the grinding wheel are formed in a round shape. Thus, effective and economical grinding is performed by using pure water as a grinding liquid. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

Field of Invention

The present invention relates to a grinding wheel and a grinding method used for grinding a silicon wafer and for grinding a workpiece to be thinned.

A grinding wheel using diamond abrasive grains has been used as a tool for grinding, polishing and flattening a silicon wafer sliced from an ingot.
Such a grinding wheel is formed as an abrasive layer that acts as a grinding function, with diamond grains, which are abrasive grains, bonded and held on the surface of a ring-shaped or disk-shaped substrate by electrodeposition, resin bonding, metal bonding, vitribonding, etc. ing. Since diamond is difficult to adhere to other substances, the main holding method is that these electrodeposition layers and bonds mechanically grab the diamond grains, and when the strength is compared under the condition that the thickness of the abrasive layer is equal, The resin is the lowest, and in the order of vitri, metal, and electrodeposition, this is also the rank of the grinding wheel life.
The diamond grains are randomly arranged as an abrasive layer, the size, shape and density of the grains are non-uniform, and the electrodeposited layer or bond in the part where the diamond grains are less arranged is locally worn, and in the worst case Diamond grains will fall off. The drop-off of diamond grains caused scratches or damage to the wafer during the thinning grinding process.
In addition, when grinding using an acidic or alkaline grinding fluid, the shape of the grinding wheel is high because the electrodeposition layer or bond deteriorates due to a chemical reaction or dissolves and the diamond grains fall off from the substrate. Grinding accuracy and grinding ratio cannot be maintained. Therefore, the current situation is that the deteriorated sharpness is recovered by continuously performing dressing repeatedly. In order to maintain the sharpness of the grindstone when grinding, diamond grains and bonds do not fall off, and the diamond grains are hard enough not to sink into the bond even at high processing pressures. However, if the bond and holding force of the conventional type grindstone is too strong, the self-generated blade action will be insufficient, resulting in abrasive wear of diamond grains and bonds. Grinding accuracy increases due to crushing, increased grinding resistance, and poor finished surface roughness, and it is inevitable that the grinding accuracy will be lowered. Yes, especially in grinding stones using electrodeposition layers, resin bonds, metal bonds, and vitribonds as bonding and holding members for diamond grains and base materials. It is not possible to exhibit an excellent ability for determined. In addition, the consumption of the grindstone is increased and the consumption of the grindstone is increased, such as an increase in the wear amount of the grindstone due to dressing for maintaining the sharpness of the waste liquid and the sharpness. In general, in order to bring the surface roughness of the grinding surface closer to a mirror surface, grinding with a shallow cutting depth with fine abrasive grains will reduce residual stress on the processing surface, and high-efficiency machining that does not cause cracking or crushing is expected. It is supposed to be possible. Conventional grindstones have limitations in reducing the size of the abrasive grains, making the shape and density uniform, making the film thin, and creating a shape as a grindstone, and there are limits to further thinning silicon wafers and grinding with less damage.

Problems to be solved by the invention

The present invention improves the productivity of grinding of a silicon wafer sliced from an ingot and other grinding materials that require thinning, sharp and high quality surface finish, and little damage to the grinding material It aims at establishing the grinding wheel which can be ground, and the grinding method with an economical effect.

Means to solve the problem

The grinding wheel used for the grinding processing of the silicon wafer of the present invention and the other flattening grinding of the material to be thinned is a direct CVD method as an abrasive layer on the surface of a ring-shaped or disk-shaped substrate. Thus, a diamond film is formed. Unlike conventional grinding stones created by bonding diamond grains to the base material by bonding or electrodeposition, the abrasive grain layer is a 100% diamond film, so there is no wear or peeling of the bond or electrodeposition layer, and no diamond grains fall off. .
By increasing the processing accuracy of the base material, the shape accuracy of the grindstone can also be increased. By forming a diamond film on the base material by CVD, it is possible to manufacture the diamond particles by controlling the arrangement, shape, size, density, and film thickness uniformly and freely. Processing can be realized. In particular, the sharpness is improved by providing grooves or irregular patterns on the diamond film as the abrasive layer.
Since diamond films are chemically stable, they are excellent in durability because they are stable and resistant to wear even with acidic and alkaline grinding fluids. Furthermore, since clogging is less likely to occur compared to conventional grinding stones, grinding waste can be easily discharged with water pressure or pneumatic pressure, maintaining excellent sharpness, and there is no occurrence of stagnation on the grinding surface, resulting in a high grinding ratio and high productivity. Improvement can be achieved.
According to the CVD method, a diamond film can be formed even on ultrafine particles with a high density, and a grinding wheel with a uniform cutting edge size and cutting edge height can be produced. For this reason, grinding can be performed with a shallow depth of cut, controlled to a level of 0.1 to 0.05 μm, the residual stress on the processed surface of the material to be ground is reduced, and cracks and fractures are not generated. Since less grinding is possible, thinning and high-quality surface finishing are possible.
In the present invention, when grinding is performed using a ring-shaped or disc-shaped grinding wheel formed by forming a diamond film by a CVD method, it is not necessary to use an acidic or alkaline grinding liquid, and high efficiency is achieved using pure water. Can be ground.

When grinding a workpiece using a ring-shaped or disk-shaped grinding wheel, most grinding machines set the depth of cutting of the rotating grinding wheel with a rigid mechanism and wear the grinding wheel. If this is ignored, a forced cutting method is employed that can grind the material to be ground to the depth of the cut.
On the other hand, there is a constant pressure cutting method in which a rotating grinding wheel is pressed against a material to be ground with a constant pressure for grinding. Grinding or lapping that requires high-quality surface finish that grinds the entire surface uniformly and flatly by moving the grinding wheel forward, backward, or up and down according to the undulation if the grinding surface sent by the processing table has undulations For this, a constant pressure cutting method is suitable.
As the cutting method, it is only necessary to perform processing according to the processing purpose. However, when the cutting depth is set, the wear of the abrasive grains cannot be ignored. Conventional grinding wheels need to maintain grinding accuracy and grinding ratio by the action of self-sharpening due to abrasive grains, bond wear, and blades by dressing, and it has been difficult to improve the productivity of grinding.
Since the grinding wheel formed by forming a diamond film on the base material by CVD as in the present invention is not easily worn, the cutting depth can be easily set and the sharpness can be maintained. High precision grinding is possible.
The inventors of the present application have already applied Japanese Patent Application No. 2005-36398 for a polishing body in which a diamond film is uniformly formed on the surface of a grinding wheel base material by a CVD method so as to have a uniform particle size, shape, arrangement, density and film thickness. However, the present invention can be used for grinding a silicon wafer sliced from an ingot using such a polishing body, or for grinding a workpiece to be thinned. Thus, the present invention provides a grinding wheel having a novel technique with further improvements.

FIG. 9 schematically shows a silicon wafer grinding method using the grinding wheel of the present invention.
1 is an assembly of a grinding wheel according to the present invention, 2 is a silicon wafer, and 3 is a processing table for placing the silicon wafer.
While the processing table 3 is rotated or moved back and forth, and left and right, the rotating grinding wheel assembly 1 is used to press the silicon wafer 2 placed on the processing table 3 with a predetermined pressure or with a predetermined depth of cut. While grinding. During this grinding process, the grinding liquid 5 is sprayed from the nozzle 4 toward the grinding surface of the silicon wafer 2 and the grinding wheel assembly 1 from a grinding liquid supply source (not shown) on the processing table 3 and is generated by grinding. To cool the frictional heat, or help to discharge grinding scraps. Although the processing table 3 has been described by a method of rotating or moving back and forth, and left and right, the processing table 3 can also be ground by moving it back and forth, left and right, and up and down while rotating the grinding wheel assembly 1 only by rotation.
Control of the rotational speed of the grinding wheel assembly 1, the depth of cutting of the grinding wheel assembly 1 into the silicon wafer 2, or the processing pressure, the rotational speed of the processing table 3, the moving speed of the grinding wheel assembly 1 or the processing table 3, etc. Are set and controlled with appropriate grinding conditions by a control panel (not shown).
As an example of a grinding wheel according to the present invention for use in a grinding apparatus according to the present invention, an example of a grinding wheel for a silicon wafer obtained by further improving the polishing body according to Japanese Patent Application No. 2005-363986 disclosed by the present inventor will be described.

FIG. 10 is a schematic view of the grinding wheel assembly 1 of FIG. A grinding wheel portion in which a diamond film 7 is uniformly formed in a size, shape, density, and film thickness as an abrasive layer by a CVD method on the lower end of a ring-shaped or disk-shaped substrate 6, and the substrate 6 It is comprised from the rotating shaft 13 integrally or removably assembled | attached above the center part. Hereinafter, in order to make the description easy to understand, the grinding wheel assembly 1 and the grinding wheel portion without the rotating shaft 13 will be collectively referred to as a grinding wheel.

FIG. 1 is a schematic diagram of a ring-shaped grinding wheel as viewed from below the base material 6 and the diamond film 7 of the grinding wheel assembly 1 shown in FIG. 10 in the first embodiment of the grinding wheel of the present invention.
In particular, a polishing grindstone in which the outer peripheral and inner peripheral ridges of the ring-shaped substrate 6 acting as an abrasive layer are R-processed and a diamond film is formed on the surface by a CVD method to form an abrasive layer. Is to provide. By giving R to the ridge, the initial cutting when the silicon wafer is ground is smoothly performed, the impact when cutting the grinding wheel and the silicon wafer is small, and the effect of preventing cracks and breakage can be expected. It becomes effective as the grinding of silicon wafer thinning proceeds.

FIG. 2 shows a second embodiment of the grinding wheel according to the present invention. A plurality of grooves 9 </ b> A, 9 </ b> B, 9 </ b> C, and 9 </ b> D are provided in the diamond film portion 8 as a ring-shaped abrasive layer so that grinding fluid and polishing waste are discharged from the inner peripheral portion of the substrate 6 toward the outer peripheral portion. The present invention provides a grinding wheel characterized by that.

FIG. 3 shows a third embodiment of the grinding wheel according to the present invention. Providing a grinding wheel that has a rim portion of the outer periphery of the surface that acts as an abrasive layer of the disk-shaped substrate 10 in advance, and a diamond film 8 is formed on the surface by a CVD method to form an abrasive layer. To do.
FIG. 4 shows a fourth embodiment of the grinding wheel according to the present invention. A plurality of grooves 9 </ b> A, 9 </ b> B, so that grinding fluid and grinding debris are discharged from the central part to the outer periphery of the diamond film 8 part formed by CVD as an abrasive layer on the surface of the disk-shaped substrate 10. A disc-shaped grinding wheel characterized by providing 9C and 9D is provided.

FIG. 5 shows a fifth embodiment of the grinding wheel according to the present invention, in which a plurality of grooves 9A, 9B, 9C, 9D of the fourth embodiment are discharged from the center toward the outer periphery. The present invention provides a disk-shaped grinding wheel characterized by being provided radially.
FIG. 6 shows a sixth embodiment of the grinding wheel according to the present invention. A spiral groove is provided on the surface of the disk-shaped substrate 10 so that the polishing liquid and polishing debris can be easily discharged from the center to the outer periphery of the diamond film 8 formed as an abrasive layer by the CVD method. A disc-shaped grinding wheel characterized by the above is provided. A plurality of grooves provided in the diamond film 8 shown in FIGS. 2, 4 and 5 are processed in advance on the surface of the base 6 or 10 by machining, and the diamond film 8 is formed by the CVD method. Thus, it can be produced as an abrasive layer.
Similarly, the spiral-shaped groove 11 shown in FIG. 6 can be machined on the surface of the substrate 10, and the diamond film 8 can be formed by the CVD method to be manufactured as an abrasive layer.

FIG. 7 is a schematic diagram showing another grinding wheel manufacturing method according to the present invention, and FIG. 8 is a disk-shaped grinding wheel having a diamond film 8 formed by the CVD method according to the manufacturing method of FIG.
FIG. 7 shows a portion where a diamond film 8 as an abrasive grain layer is formed above the surface of the base material 10 when the film is formed by the CVD method, and FIG. 2, FIG.
A mask plate 12 having holes patterned so as to form a plurality of grooves 9A, 9B, 9C, 9D shown in FIG. 5 and a spiral groove 11 shown in FIG. 6 is provided for selection. By forming a film by the CVD method, it is possible to form a diamond film having a similar groove or uneven pattern on the substrate 6 and the substrate 10 without previously machining the groove by machining.

  Although not shown as another method, after a patterned oxide film is formed on the surface of the base material 10, a diamond film is formed in a portion without the oxide film by a CVD method, and a portion with the oxide film is formed. Thus, it is possible to manufacture a grinding wheel having a diamond film having a groove or a concavo-convex pattern.

FIG. 8 shows a disc-shaped polishing grindstone manufactured by growing diamond particles in an arbitrary arrangement, density, shape and film thickness by the pattern of the mask plate 12 or the pattern formed on the surface of the substrate 10 by the CVD method. It is. In the CVD method, by changing the reaction gas, the diamond particle size, shape, density, and film thickness can be freely controlled to form a film, so the optimum particle size, shape, and film for grinding silicon wafers. Thick grinding wheels can be manufactured.
Using this grinding wheel, the silicon wafer 2 could be ground with high efficiency by the polishing method as shown in FIG. 9 described above.

The invention's effect

Since the grinding wheel according to the present invention is diamond whose grain layer is formed by CVD, it has excellent wear resistance, high density, fine grains, and uniform cutting edge size and cutting edge height. The sharpness is good and the cutting edge position of the abrasive grains can always be kept stable, so that the material to be ground such as a silicon wafer can be efficiently ground with high shape accuracy.
By increasing the processing accuracy of the base material of the grinding wheel, the shape accuracy of the grinding wheel can be increased, which is suitable for precision grinding.
A diamond film as an abrasive layer can be manufactured by controlling the size, arrangement, shape, density, and thickness of the particles uniformly and freely by CVD. Grinding with a shallow cutting depth can be performed with this grinding wheel, the residual stress on the processed surface is reduced, and a high-quality surface finish without cracking or crushing can be expected.
Grinding by forming the ridges on the inner and outer circumferences of a ring-shaped or disk-shaped grinding wheel in an R shape, or providing grooves and irregularities in the abrasive layer to discharge grinding fluid and grinding debris from the inside to the outer circumference The clogging of the abrasive layer can be prevented by the flow of the liquid, the cooling effect of the abrasive layer can be improved, the thermal distortion of the silicon wafer can also be prevented, and the grinding process can be performed with little damage to the thinning process.
Diamond is chemically stable, and there is no problem in using acidic or alkaline grinding fluids. However, because of its sharpness, it can be ground using pure water as grinding fluid, so it can reduce costs such as waste liquid treatment costs. It is.

The schematic diagram of the 1st Example of the grinding wheel in this invention The schematic diagram of the 2nd Example of the grinding wheel in this invention The schematic diagram of the 3rd Example of the grinding wheel in this invention Schematic diagram of the fourth embodiment of the grinding wheel in the present invention Schematic diagram of the fifth embodiment of the grinding wheel in the present invention Schematic diagram of the sixth embodiment of the grinding wheel in the present invention The schematic diagram which shows another production method of the grinding wheel in this invention Schematic diagram of a grinding wheel coated with another production method of the present invention Schematic diagram of silicon wafer grinding method using grinding wheel in the present invention Schematic diagram of an assembly of grinding wheels in the present invention

Explanation of symbols

1: Assembly of grinding wheel 2: Silicon wafer 3: Processing table 4: Nozzle 5: Grinding liquid 6: Base material 7: Diamond film 8: Diamond films 9A, 9B, 9C, 9D: Groove 10: Substrate 11: Groove 12: Mask plate 13: Rotating shaft

Claims (12)

A ring-shaped grinding wheel characterized in that a ridge portion of a surface that acts as an abrasive layer of a ring-shaped substrate is formed in an R shape and a diamond film is formed on the surface by a CVD method. A disk-shaped grinding wheel characterized in that a ridge portion of a surface that acts as an abrasive layer of a disk-shaped substrate is formed in an R shape and a diamond film is formed on the surface by a CVD method. A ring-shaped grinding wheel characterized in that a diamond film is formed by CVD on a surface provided with a concave groove that acts as an abrasive layer of a ring-shaped substrate. A disk-shaped grinding wheel characterized in that a diamond film is formed by a CVD method on a surface provided with a concave groove that acts as an abrasive layer of a disk-shaped substrate. A mask plate having a plurality of patterned holes is placed on the surface to act as an abrasive layer of a ring-shaped substrate, and a groove is formed by forming a diamond film by a CVD method. A ring-shaped grinding wheel with special features. A mask plate having a plurality of patterned holes is placed on the surface to act as an abrasive layer of a ring-shaped substrate, and a diamond film is formed by a CVD method to form irregularities. Ring-shaped grinding wheel A mask plate having a plurality of patterned holes is placed on the surface acting as an abrasive layer of a disk-shaped substrate, and a diamond film is formed by a CVD method to form a groove. A disc-shaped grinding wheel. A mask plate having a plurality of patterned holes is placed on a surface on which a disk-shaped substrate acts as an abrasive layer, and a diamond film is formed by CVD to form irregularities. A disc-shaped grinding wheel. After depositing a patterned oxide film on the surface that acts as an abrasive layer of a ring-shaped substrate, a diamond film is formed by CVD, and the oxide film is formed as a recess. A ring-shaped grinding wheel characterized by After depositing a patterned oxide film on the surface that acts as an abrasive layer of a disk-shaped substrate, a diamond film is formed by CVD, and the oxide film is formed as a recess. A disc-shaped grinding wheel characterized by While rotating a grinding wheel formed by depositing a diamond film by CVD on the surface that acts as the abrasive layer of the substrate, the surface of the material to be ground, such as a silicon wafer held on a rotating processing table, is subjected to a predetermined pressure. Grinding while sprinkling pure water on the grinding wheel and the material to be ground such as a silicon wafer in the step of grinding while applying pressure. The surface of the material to be ground, such as a silicon wafer held on a rotating processing table, is rotated with a predetermined depth of cut while rotating a grinding wheel formed by forming a diamond film on the surface to act as the abrasive layer of the substrate by CVD. Grinding while sprinkling pure water on the grinding wheel and the material to be ground such as silicon wafer in the step of grinding while cutting

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