CN101332588A - Cup type grinding wheel for backside grinding of semiconductor wafer and grinding method - Google Patents

Abstract

To provide a cup-type grinding wheel for rough grinding of the back surface of a semiconductor wafer that does not require particularly complicated manufacturing processes, improves grinding efficiency by increasing sharpness, and prevents grinding damage that becomes an obstacle in finish grinding as a post-process, and uses the same A better grinding method for rough grinding with a cup wheel for rough grinding. On the cup-shaped grinding wheel (2) used in the rough grinding of the previous process of fine grinding in the grinding of the back of the semiconductor wafer (W), the superabrasive grain blocks (4) are arranged in a substantially radial pattern on the disc-shaped On the circular side surface (31) of the pedestal (3), the long side (42) of the grinding action surface (41) is arranged roughly along the radial direction of the pedestal (3).

Description

Cup type grinding wheel for backside grinding of semiconductor wafer and grinding method

technical field

The present invention relates to a cup-shaped grinding wheel used for rough grinding of the back surface of a semiconductor wafer and a grinding method using the cup-shaped grinding wheel.

Background technique

In the past, a cup-shaped grinding wheel was used in the back grinding of semiconductor wafers such as silicon wafers. On the cup-shaped grinding wheel, a superabrasive layer composed of diamond or cubic boron nitride (CBN) was used on the circular side of the pedestal. formed into a ring. In the back grinding of semiconductor wafers, a semiconductor wafer with a thickness of about 775 μm on which a predetermined film has been formed on the surface is cut from the back side to a substantially predetermined thickness by rough grinding, and finally processed to a predetermined thickness by finish grinding and smooth surface. However, in recent years, as semiconductor wafers have become thinner, in the back grinding of semiconductor wafers, the process of enlarging the cutting allowance of rough grinding to produce thin wafers is often adopted. Rough grinding is located between the film forming process on the surface of the semiconductor wafer and the subsequent fine grinding process. If too much processing time is spent in rough grinding, other processes will have waiting time, which will affect the overall processing efficiency. However, if the polishing rate is only increased, the semiconductor wafer may be burnt or cracked in the worst case, making it impossible to process the semiconductor wafer. In this case, the processing load of finishing grinding will increase. Therefore, in rough machining, it is desired to improve the grinding efficiency reasonably by increasing the sharpness, and to prevent the occurrence of grinding damage that becomes an obstacle in the finishing grinding as a post-process.

Therefore, various techniques have been developed to improve the sharpness of the cup-shaped grinding wheel used in the backside processing of the conductor sheet. The multi-groove, so as to realize a cup-type grinding wheel with good sharpness that can discharge chips smoothly. In the invention described in Patent Document 2, a part of the groove is extended to the peripheral surface of the base.

Patent Document 1: Japanese Patent Laid-Open No. 11-179667

Patent Document 2: Japanese Patent Laid-Open No. 11-245169

However, in the inventions described in Patent Document 1 and Patent Document 2, it is necessary to process complex shapes such as electric discharge machining on the superabrasive layer, and since the back surface of the semiconductor wafer is used as the grinding object, it is impossible to particularly consider The technical specificities of coarse and fine grinding preclude appropriate measures for their respective use.

Contents of the invention

In order to solve the above-mentioned problems of the prior art, the object of the present invention is to provide a grinding machine that does not require particularly complicated manufacturing processes, improves the grinding efficiency by improving the sharpness, and can prevent grinding damage that becomes an obstacle in the finishing grinding as a post-process. A cup wheel for rough grinding of the back surface of a semiconductor wafer is produced to improve the polishing efficiency of finish grinding, and a preferable grinding method for rough grinding using such a cup wheel for rough grinding.

In order to achieve the above object, the cup-shaped grinding wheel for grinding the back of a semiconductor wafer of the present invention is used in the grinding of the back of the semiconductor wafer as the rough grinding of the previous process of fine grinding, and is characterized in that the superabrasive block is approximately It is arranged radially on the circular side surface of the disc-shaped pedestal, and the long side of the grinding action surface is arranged substantially along the radial direction of the pedestal. According to the present invention, by utilizing the simple structure of disposing the superabrasive grain blocks in a substantially radial shape on the pedestal, it is possible to obtain a grinding efficiency by improving the sharpness, and prevent the grinding effect in the finishing grinding as a post-process. Cup type grinding wheel for rough grinding of the back surface of semiconductor wafers where grinding damage such as cracks and edge chipping of semiconductor wafers, which become obstacles, occurs.

In addition, when the average grain size of the superabrasive grains of the superabrasive grain block is #270 to #800, it is the most suitable range of superabrasive grains for rough grinding of the back surface of a semiconductor wafer.

In addition, when the long side of the grinding action surface of the superabrasive block is arranged substantially radially within the range of ±10 degrees in the radial direction of the pedestal, it is the most suitable range for the superabrasive block along the radial direction of the pedestal.

In addition, when the gap between adjacent superabrasive grains is greater than the length of the short side of the grinding action surface of the superabrasive grains, the effect of making the superabrasive grains arranged in a substantially radial pattern is obvious, and can make the cutting Chips drain well.

Furthermore, the shape of the superabrasive block on the grinding action surface can be formed into an arc shape that is substantially along the radial direction of the pedestal and protrudes toward the rotation direction. At this time, the wear of the grinding wheel can be reduced to prolong the life of the grinding wheel. In addition, superhard abrasive grains can be produced by the same manufacturing method as the superhard abrasive grains on the cup-shaped grinding wheel formed by arranging the arc-shaped superabrasive grains used in the past in a substantially continuous ring shape on the side of the pedestal. Abrasive blocks can also be manufactured with the same specification according to different situations.

In addition, the method for grinding the backside of a semiconductor wafer according to the present invention is characterized in that rough grinding is performed with one cup-shaped grinding wheel, and then finish grinding is performed with another cup-shaped grinding wheel, the cup-shaped grinding wheel used for rough grinding The superabrasive grain blocks are arranged substantially radially on the circular side of the disc-shaped pedestal and the long side of the grinding action surface is arranged roughly along the radial direction of the pedestal. The cup-shaped grinding wheel for fine grinding The superabrasive block is arranged in a substantially annular shape on the circular side surface of the disc-shaped pedestal in a state where the long side of the grinding action surface is substantially along the circumferential direction of the pedestal. According to the present invention, it is possible to increase the sharpness of the cup-shaped grinding wheel in which the superabrasive blocks are arranged substantially radially, thereby improving the efficiency of the previous rough grinding process, and making the superabrasive blocks The sharpness is also increased in the finish grinding process by the cup-shaped grinding wheel arranged in a roughly ring shape, thereby improving the grinding efficiency. Thereby, the polishing efficiency of the entire polishing process can be improved, and the polished surface of the semiconductor wafer can be smoothed.

The present invention provides a method that does not require particularly complicated manufacturing processes, improves the grinding efficiency of rough grinding by increasing the sharpness, prevents the occurrence of grinding damage that becomes an obstacle in the finishing grinding as a post-process, and improves the grinding efficiency of finishing grinding. An efficient cup-shaped grinding wheel for backside rough grinding of semiconductor wafers, and a preferred grinding method for rough grinding using such a cup-shaped grinding wheel for rough grinding.

Description of drawings

FIG. 1 is a conceptual diagram showing the configuration of a polishing apparatus according to an embodiment of the present invention.

Fig. 2 is a plan view of a cup wheel for rough grinding according to an embodiment of the present invention.

Fig. 3 is a cross-sectional view of the cup wheel for rough grinding in Fig. 2 .

Fig. 4 is a partial side view of the cup wheel for rough grinding in Figs. 2 and 3 .

Fig. 5 is a perspective view of a superabrasive block according to an embodiment of the present invention.

Fig. 6 is a plan view of a cup wheel for finish grinding according to an embodiment of the present invention.

Fig. 7 is a cross-sectional view of the cup wheel for finish grinding in Fig. 6 .

Fig. 8 is a partial side view of the cup-shaped grinding wheel for finishing in Figs. 6 and 7 .

Fig. 9 is a measurement result of processing resistance of rough grinding in the examples of the present invention and the comparative example.

Fig. 10 is the measurement result of the processing resistance when the wafers rough-polished in the embodiment of the present invention and the comparative example are further polished.

(Symbol Description)

1 Rough grinding device 2 Cup grinding wheel for rough grinding

3 pedestals 4 superhard abrasive blocks

5 Fine grinding device 6 Cup grinding wheel for fine grinding

7 pedestals 8 superhard abrasive blocks

11 rotating shaft 12 clamping table

13 axis of rotation 51 axis of rotation

52 clamping table 53 rotating shaft

Detailed ways

Hereinafter, preferred embodiments of the cup wheel for rough grinding of the semiconductor wafer backside according to the present invention and the grinding method for rough grinding using such a cup wheel for rough grinding will be described in detail with reference to the accompanying drawings. FIG. 1 is a conceptual diagram showing the whole of a polishing apparatus according to this embodiment. The rough grinding device 1 is composed of a cup-shaped grinding wheel 2 for rough grinding and a clamping table 12. The cup-shaped grinding wheel 2 for rough grinding can rotate around the rotating shaft 11 and can advance and retreat in the axial direction. The clamping table 12 can rotate around the axis and the rotating shaft. 11. The rotating shaft 13 arranged in a shifted position rotates and fixes the semiconductor wafer W on the surface. The fine grinding device 5 is also similarly composed of a cup-shaped grinding wheel 6 for fine grinding and a chuck 52. The cup-shaped grinding wheel 6 for fine grinding can rotate around the rotating shaft 51 and can advance and retreat in the axial direction. The clamping table 52 can rotate around the axis. The rotation shaft 53 , whose center is shifted from the rotation shaft 51 , rotates and fixes the semiconductor wafer W on the surface.

The most characteristic cup wheel 2 for rough grinding in this embodiment is shown in FIGS. 2 to 4 . FIG. 2 is a plan view equivalent to viewing the cup-shaped grinding wheel 2 of FIG. 1 from below, and FIG. 3 is a III-III sectional view thereof. The cup-shaped grinding wheel 2 is composed of a disk-shaped base 3 and superabrasive blocks 4 attached substantially radially to its circular side surface 31 . The diameter of the pedestal 3 is preferably about 200-350 mm. FIG. 4 is a partial side view of the peripheral surface of the cup-shaped grinding wheel 2 viewed from the IV direction of FIG. 3 . The superabrasive block 4 is inserted into the groove 32 formed on the side surface 31 of the pedestal 3 and fixed with an adhesive. Here, the groove 32 runs through the pedestal 3 in the radial direction, and forms a hole with a slightly larger radial width on the side surface 31, which is roughly the same shape as the bottom surface of the superabrasive block 4. Block 4 is fixed in this hole. The upper surface of the superabrasive block 4 in the figure serves as the grinding action surface 41 that abuts on the back surface of the semiconductor wafer W. As shown in FIG.

FIG. 5(A) is a perspective view of a superabrasive block 4 . The superabrasive block 4 is in the shape of a cuboid, and the long side 42 of the grinding action surface 41 is arranged substantially along the radial direction of the pedestal 3 . Here, it is preferable that the long side is about 5 to 50 mm, the short side is about 2 to 5 mm, and the height is about 3 to 10 mm. The superabrasive block 4 is preferably a resin grinding wheel made of diamond or cubic crystal boron nitride (CBN) made of superabrasives combined with phenolic resin or polyimide resin, or a glassy bonding material The bonded vitrified bonded grinding wheel may be of any other type as long as it is a superabrasive grinding wheel that can be formed into the shape described above. The average particle size of superhard abrasive grains is preferably above #270 and below #800. If the average particle size of the superabrasive grains is less than #270, the abrasive grains are too rough, and the unevenness on the back surface of the semiconductor wafer becomes large, which cannot be sufficiently smoothed in the finishing process as a post-process. In addition, if the average particle diameter of the superabrasive grains exceeds #800, it will not be possible to effectively polish as rough polishing.

The superabrasive blocks 4 are arranged approximately in the radial direction of the pedestal 3 , and if they are arranged within a range of ±10 degrees from the radial direction, the role of the radial arrangement in this embodiment can be fully exhibited. In addition, in the configuration of the pedestal 3, by making the gap between the adjacent superabrasive blocks 4 greater than the length of the short side 43 of the grinding action surface of the superabrasive block 4, each superabrasive particle can be played. Block 4 is arranged radially, and sufficient clearance is used to improve the discharge capacity of cutting chips.

In FIG. 5(A), the superabrasive block 4 has been described as a grinding wheel having a rectangular parallelepiped shape. However, as shown in FIG. 5(B), the edges may be in a circular arc shape. At this time, the arc-shaped long side 42 of the polishing action surface 41 is arranged along the radial direction of the base 3 as in FIG. 2 . At this time, it is also preferable to make the superabrasive block 4 be configured in the radial range of ± 10 degrees, and make the gap between adjacent superabrasive blocks 4 greater than the short side 43 of the superabrasive block 4 length. In addition, it is preferable to arrange the convex side of the arc toward the rotation direction side.

Next, the cup grindstone 6 for finishing of the grinding|polishing apparatus 5 for finishing is demonstrated based on FIGS. 6-8. The cup grinding wheel 6 itself for finishing is the same type of grinding wheel as that conventionally used. FIG. 6 is a plan view corresponding to the cup-shaped grinding wheel 6 of FIG. 1 viewed from below, and FIG. 7 is a VII-VII sectional view thereof. The cup-shaped grinding wheel 6 is composed of a disc-shaped base 7 and a superabrasive block 8 attached to its circular side surface 71 in a substantially annular shape along the circumferential direction. The diameter of the pedestal 7 is preferably about 200 to 350 mm. FIG. 8 is a partial side view of the peripheral surface of the cup-shaped grinding wheel 6 viewed from the VIII direction of FIG. 7 . The superabrasive blocks 8 are inserted into the annular grooves 72 formed on the side 71 of the pedestal 7 along the end edge, and there is a very small gap between adjacent superabrasive blocks 8, and the adhesive is used to fixed. The shape of the superabrasive block 8 is the same as the example of the superabrasive block 4 shown in Fig. 5 (B) for rough grinding, and the type of the emery wheel is also preferably made of diamond or cubic crystal boron nitride (CBN). The formed superhard abrasive grains are resin grinding wheels combined with phenolic resin or polyimide resin, vitrified bonded grinding wheels combined with glassy bonding materials, or other formable grinding wheels. However, the average grain size of superhard abrasive grains is smaller than that used in rough grinding, and it is better to be #400 or more and #4000 or less for finishing. The superabrasive blocks of this shape are arranged substantially radially when used as the cup-shaped grinding wheel 2 for rough grinding, and are arranged in a substantially annular shape when used as the cup-shaped grinding wheel 8 for finish grinding as in the past.

Next, the polishing action of the polishing device of this embodiment will be described. With respect to the semiconductor wafer W fixed with the back surface facing up on the chuck 12 of the rough grinding device 1 and rotated at a predetermined speed, the cup-shaped grinding wheel 2 is fed in the axial direction while rotating at a predetermined speed, thereby grinding the back surface of the semiconductor wafer W. Grinding is performed to obtain a thickness substantially close to the target value of the predetermined thickness of the semiconductor wafer. Next, the cup wheel 6 of the finish grinding device 5 in the post-process removes cracks in the surface layer portion generated by rough grinding on the back surface of the semiconductor wafer W, and smooths the back surface. In the rough grinding process, using the cup-shaped grinding wheel 2 arranged substantially radially according to this embodiment, as described in Example 1 below, compared with the conventional case of using a cup-shaped grinding wheel arranged substantially annularly, the Processing resistance, so as to achieve better sharpness of the grinding process. Therefore, the feeding speed of the cup wheel 2 in the axial direction (the speed of cutting into the semiconductor wafer W) can be increased, thereby improving the efficiency of the grinding process. In addition, due to the reduction in processing resistance, grinding damage caused by cracks in the surface layer of the back surface of the semiconductor wafer W made of brittle materials or edge chipping in the edge can be prevented, thereby improving the grinding efficiency of the finish grinding process. In addition, due to the reduction of processing resistance, the average particle size of the superabrasive grains used in rough grinding can be correspondingly reduced. In the process, the grinding allowance can be further reduced to improve efficiency and further improve the smoothness of the finished surface.

In addition, when the conventional substantially annular cup-shaped grinding wheel 6 is used in the finish-grinding device 5, in the finish-grinding of the semiconductor wafer W that has been ground by the roughly radial cup-shaped grindstone 2 for rough-grinding of this embodiment, Compared with the case where rough grinding is performed using a conventional substantially ring-shaped cup-shaped grinding wheel, as described in Example 2 below, the grinding resistance can be reduced to achieve grinding with better sharpness. Thus, on the cup-shaped grinding wheel 2 for rough grinding, the superabrasive grain blocks 4 are arranged in a substantially radial pattern as described in this embodiment, and the efficiency and quality of rough grinding can be improved by using the cup-shaped grinding wheel 2 for rough grinding. And it can also improve the efficiency and quality of finishing grinding.

In addition, in the cup-shaped grinding wheel 2 for rough grinding, when the arc-shaped superabrasive block 4 is protruded in the direction of rotation as shown in FIG. ) is roughly the same as the grinding wheel in which the rectangular parallelepiped superabrasive grain blocks are arranged in a substantially radial shape, which can reduce the processing resistance. Therefore, as described in the following embodiment 3, the speed of grinding wheel wear can be reduced compared with conventional grinding wheels arranged in a substantially annular shape and a grinding wheel in which cuboid superabrasive grains are arranged in a substantially radial shape, thereby prolonging the life of the grinding wheel. . In addition, the arc-shaped superabrasive grain block arranged on the side surface of the pedestal in a substantially continuous ring-shaped cup-shaped grinding wheel, which is also used in the fine grinding of the present embodiment, can be carried out once. To sintering into a continuous ring-shaped process, and then divided to manufacture, but if it is the arc-shaped superabrasive block 4 shown in Figure 5 (B), the same manufacturing method can be used to manufacture superabrasive abrasive block 4. Abrasive block. In addition, depending on the situation, the same process can also be used to make the manufacturing process and manufacturing equipment common.

[Example 1]

Examples are described below.

Example 1

The following grindstones were manufactured as an example of the cup-shaped grindstone 2 for rough grinding using the superabrasive block 4 of the shape shown in FIG. 5(A).

The diameter of the pedestal 3: 300mm, the long side of the grinding action surface of the superabrasive block 4: about 19mm, the short side: 3mm, the number of the superabrasive block 4: 48 radially arranged, the superabrasive Type: diamond grinding wheel, average grain size of superhard abrasive grains: #325, bonding material: phenolic resin

On the other hand, the object of comparison is a cup-shaped grinding wheel in which 48 arc-shaped superabrasive blocks 48 of non-cuboid shape, width of 3 mm, and arc-shaped long side of about 19 mm are arranged in a ring under the same conditions as above. .

The above two kinds of cup-shaped grinding wheels were used for rough grinding of 12-inch silicon wafers under the conditions of grinding wheel rotation speed 2400rpm, feed speed 250μm/min, and chuck rotation speed 300rpm, and the processing resistance was obtained according to the spindle load current value. As a result, as shown in FIG. 9 , the radially-arranged cup-shaped grinding wheel of the present embodiment can significantly reduce the machining resistance compared with the annularly-arranged cup-shaped grinding wheel of the comparison object. In addition, although the polishing streaks appearing on the polishing surface of the silicon wafer vary depending on the conditions, they are always different from the case of being arranged in a ring shape, and it is considered to be one of the reasons why the processing resistance in the finishing polishing as a post-process can be reduced. one.

Example 2

In Example 1, the finish grinding process was performed on the silicon wafer subjected to the rough grinding process of the present embodiment and the silicon wafer subjected to the rough grinding process of the comparative object. Here, the cup-shaped grinding wheel 6 of the finish grinding device 5 is a grindstone of the same specification as that of the comparison object in Example 1, but the average grain size of superabrasive grains is #2000 for finish grinding. The grinding conditions were as follows: the rotation speed of the grinding wheel was 2400 rpm, the feeding speed was 25 μm/min, and the rotation speed of the holder was 120 rpm. As a result, as shown in FIG. 10 , the fine grinding of silicon wafers that were roughly ground using the radially arranged cup wheels 2 of this embodiment was compared with the rough grinding process using the annularly arranged cup wheels 2 of the comparison object. Compared with the case of fine grinding of silicon wafers, the processing resistance can be reduced.

Example 3

Using the same conditions as in Example 1, the machining resistance and the amount of grinding wheel wear were measured for the cup-shaped grinding wheel 2 in which the arc-shaped superabrasive grain sheets 4 shown in FIG. 5(B) were radially arranged. The results show that the machining resistance is substantially the same as that of the grinding wheel in which the cuboid superabrasive blocks 4 are arranged substantially radially in Example 1, regardless of whether the arc shape is protruded in the rotation direction or vice versa. However, regarding the progress of grinding wheel wear, that is, the wear rate, when the arcuate superabrasive blocks 4 are arranged to protrude in the direction of rotation, the rectangular parallelepiped superabrasive blocks 4 are arranged substantially radially in Example 1. Compared with the grinding wheel of the conventional type, which is arranged in a ring shape, the grinding wheel can slow down the wear speed and prolong the life of the grinding wheel. In particular, when the radius of curvature of the arc-shaped superabrasive block 4 is about 200 mm corresponding to the radius of curvature of the pedestal 3 of 150 mm, the abrasion of the grinding wheel can be halved.

Claims (6)

1, a kind of backside semiconductor is ground and is used cup wheel, be used for the rough lapping as the preceding working procedure of smooth grinding of the grinding of backside semiconductor, it is characterized in that, the super-hard abrasive piece is configured in with being general radial on the round sides of discoid pedestal and the long limit that makes the abrasive action face roughly along the radial arrangement of described pedestal.

2, backside semiconductor as claimed in claim 1 is ground and is used cup wheel, it is characterized in that the average grain diameter of the super-hard abrasive of described super-hard abrasive piece is in the scope of #270 to #800.

3, backside semiconductor as claimed in claim 1 or 2 is ground and use cup wheel, it is characterized in that, the described long limit of the described abrasive action face of described super-hard abrasive piece described pedestal radially ± roughly radially dispose in the scopes of 10 degree.

4, use cup wheel as each described backside semiconductor grinding in the claim 1 to 3, it is characterized in that the gap of adjacent described super-hard abrasive interblock is greater than the length of the minor face of the described abrasive action face of described super-hard abrasive piece.

5, grind as each described backside semiconductor in the claim 1 to 4 and use cup wheel, it is characterized in that, the shape of described super-hard abrasive piece on described abrasive action face forms roughly circular-arc radially and to the direction of rotation protrusion along described pedestal.

6, a kind of Ginding process of backside semiconductor, it is characterized in that, after utilizing a kind of cup wheel to carry out rough lapping processing, utilize another kind of cup wheel to carry out smooth grinding processing, this super-hard abrasive piece that is used for the cup wheel of rough lapping processing be configured on the round sides of discoid pedestal with being general radial and the long limit that makes the abrasive action face roughly along the radial arrangement of described pedestal, this super-hard abrasive piece that is used for the cup wheel that smooth grinding processes is roughly annularly with the long limit of abrasive action face roughly along the circumferential state configuration of the described pedestal round sides at discoid described pedestal.

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