JPH066258B2 - Method of grinding the surface of a silicon wafer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for grinding a surface of a silicon wafer, and more specifically, a fixed superabrasive arranged on an annular free end edge of a rotationally driven support member. The present invention relates to a method for grinding a surface of a silicon wafer into a satin surface with a grain blade.

[Conventional technology]

As is well known, in the manufacture of silicon wafers, generally, a substantially cylindrical ingot made of high-purity silicon is produced, and then this ingot is sliced into an appropriate thickness to obtain a large number of substantially disc-shaped silicon. Generate a wafer.
After that, both sides of each silicon wafer are processed with abrasive grains,
Then, each silicon wafer is dipped in an appropriate mixed acid solution to etch both surfaces thereof, and one surface of each silicon wafer is further polished to be a mirror surface.
A circuit is formed by printing or the like on the above-mentioned one surface, that is, a mirror surface of the silicon wafer manufactured in this way, but it is not uncommon for the other surface of the silicon wafer to be further subjected to abrasive grain processing after the circuit is formed.

Thus, in the processing of abrasive grains on the surface of a silicon wafer, particularly in the polishing of both surfaces of a silicon wafer before applying a circuit, it is generally considered important to make the matte surface by the abrasive grain processing. . Generally, when the surface of a silicon wafer is ground using a fixed superabrasive grain that is driven to rotate,
A considerably remarkable so-called saw mark is generated on the ground surface,
Such saw marks cause an undesired orientation of the silicon wafer. Therefore, conventionally, both sides of the silicon wafer have been processed into abrasive grains by so-called lapping using loose abrasive grains. Lapping is usually performed by interposing a lapping liquid containing free abrasive grains between both sides of a silicon wafer and a lapping plate located opposite to these.
This is performed by relatively moving the silicon wafer and the lapping plate while pressing each other with an appropriate pressure. By such lapping, the surface of the silicon wafer can be made to have a satin surface substantially free of saw marks.

[Problems to be Solved by the Invention]

However, in the lapping, (a) the working efficiency is considerably lower than when using fixed abrasive grains, (b) the silicon wafer is contaminated by the lapping liquid, and therefore the lapping and cleaning of the silicon wafer are relatively complicated after lapping and There are drawbacks and problems that a drying process must be performed and (c) automation is difficult.

The present invention has been made in view of the above facts, and its technical problem is to cause problems such as a mode of grinding the surface of a silicon wafer using a fixed superabrasive blade, that is, contamination of the silicon wafer. Despite the fact that the surface of a silicon wafer can be ground with sufficient work efficiency and in a manner that can be easily automated, the ground surface has virtually no saw marks or a slight amount of saw marks on the surface. (EN) Provided is a new and excellent method of grinding a surface of a silicon wafer which can be pressed.

[Means for Solving the Problems]

As a result of intensive studies and experiments, the present inventor has surprisingly found that when a surface of a silicon wafer is conventionally ground by using a fixed superabrasive grain blade that is rotationally driven, it is inevitable that the ground surface is ground. It was thought that a considerable saw mark was generated on the surface of the silicon wafer prior to grinding the surface of the silicon wafer by the blade. Dressing the blade by grinding in substantially the same manner as grinding
It has been found that the surface of a silicon wafer can be ground to a sufficiently good satin surface with a blade, with substantially no saw marks, or even slightly if any.

That is, according to the present invention, in order to achieve the above technical problems, the rotation axis of the fixed superabrasive grain blade disposed at the annular free end edge portion of the support member is a fixed aluminum oxide-based abrasive grain dresser. The blade and the dresser are arranged so as to be substantially perpendicular to a substantially flat surface, the blade is rotationally driven, and the blade and the dresser are arranged in a direction substantially perpendicular to the rotation axis of the blade. Move it,
Dressing the dresser by grinding the dresser with the blade, and then arranging the blade and the silicon wafer such that the rotational drive of the blade is substantially perpendicular to the surface of the silicon wafer to be ground. The blade and the silicon wafer are relatively moved in a direction substantially perpendicular to the rotation axis of the blade, and the blade is used to move the surface of the silicon wafer to a matte surface. A method for grinding a surface of a silicon wafer is provided.

[Action]

As will be clearly understood from the description of the experimental examples described below, according to the method of grinding the surface of the silicon wafer of the present invention, despite grinding the surface of the silicon wafer using a fixed superabrasive blade. The surface of the silicon wafer can be ground to a sufficiently good satin surface where saw marks are substantially absent or a little, if any.

〔Example〕

 Hereinafter, it will be described in more detail with reference to the accompanying drawings.

FIG. 1 illustrates one embodiment of a grinding wheel that can be used in the method of the present invention. The illustrated grinding wheel 2 comprises a circular base 4 and a cylindrical hanging part 6 depending from the periphery of the base 4.
And a support member 8 having This support member 8
Is conveniently formed from a suitable metallic material such as aluminum. The central portion of the base portion 4 of the support member 8 is attached to the rotary shaft 10 by an appropriate method. In the case shown in the drawing, a through opening 12 is formed in the center of the base portion 4, while a small diameter portion 14 having a male thread on the outer peripheral surface is formed at the lower end portion of the rotating shaft 10, and the opening 12 is formed in the opening 12. The small diameter portion 1 is inserted through the small diameter portion 14 so that the upper surface of the base portion 4 is brought into contact with the shoulder portion 16 of the rotating shaft 10 and protrudes through the opening 12.
The support member 8 is detachably attached to the rotary shaft 10 by screwing the nut 18 onto the protruding end portion of No. 4.

At the free edge of the support member 8, ie the hanging part 6, the blade 2
0 is provided. It is important that this blade 20 is made of fixed superabrasives. The superabrasives may be, for example, cubic boron nitride abrasives or similar abrasives, but are preferably natural or synthetic diamond abrasives. The grain size of the diamond abrasive grain is U. S. 1200 to 10 by mesh number
0, preferably 1000 to 150, more preferably 8
00 to 230 may be sufficient. The super-abrasive grain is a metal pond method using an appropriate metal binder such as nickel, copper or brass, a vitrified bond method using a clay-like binder that is heated to be porcelain, or a thermosetting resin binder. It may be bonded to the blade 20 by the resinoid bond method used or the like. Particularly when the superabrasive grains are diamond abrasive grains, they can be bonded conveniently by the metal bonding method. In the case of using the metal bond diamond abrasive grain blade 20, as in the case of the vitrified bond or resinoid bond superabrasive grain blade 20, a blade having a predetermined shape is formed and then the blade is supported by an appropriate adhesive. 8 can be adhered to a predetermined position of the supporting member 8 by a known electrodeposition method using an electrolytic solution containing nickel ions from the viewpoint of the strength of the blade 20 and the like. It is preferable that the blade 20 is directly formed and fixed at the same time.

In the illustrated embodiment, the lower surface of the hanging portion 6 of the support member 8 is inclined downward in the radial direction. The blade 20 includes a fixed or bonded portion 22 that extends along the inner surface and the lower surface of the hanging portion 6, and a free end portion 24 that extends outward in the radial direction downward beyond the lower end of the outer surface of the hanging portion 6. Have. Rotation axis 26 of blade 20
The angle α formed by the free end 24 of the blade 20 is
100 to 160 degrees, preferably 110 to 150 degrees,
Particularly preferably, it is 120 to 140 degrees. If the angle α is too large, the so-called cutting rubbing of the silicon wafer by the blade 20 at the time of grinding to be described later is reduced, and conversely if the angle α is too small, the grinding resistance that acts on the blade 20 at the time of grinding to be described later. Is too large,
Therefore, the required strength of the blade 20 is considerably increased. Suitably the thickness of the blade 20, in particular its free end 24, is from 0.05 to 2.00 mm, preferably from 0.08 to 1.00 mm, particularly preferably from 0.10 to 0.50 mm. If the thickness is too large, the contact area between the blade 20 for grinding and the silicon wafer, which will be described later, increases, which reduces the so-called cutting edge, and also requires a relatively large amount of expensive superabrasive grains. On the contrary, if the thickness is too small, the strength of the blade 20 becomes too small. Although not necessary, the blade 20 has an annular shape that continuously extends over the entire circumference of the hanging portion 6 of the supporting member 8. Is preferred.
If desired, the free end 24 of the blade 20 can be circumferentially spaced to form a plurality of slots.
The formation of such slots allows cooling water to flow through the slots during grinding, which will be described later, and also allows the grinding powder removed from the silicon wafer to easily escape through the slots, thus improving the grinding effect. Can be increased. Also, if desired, the blade 20
Alternatively, the free end portion 24 may have a corrugated sectional shape in the circumferential direction, or two or more blades 20 may be arranged concentrically with the hanging portion 6 of the supporting member 8.

FIG. 2 illustrates another embodiment of a grinding wheel that can be used in the method of the present invention. In this grinding wheel 2 ′, the lower surface of the hanging portion 6 ′ of the support member 8 ′ has the rotation axis 2
It extends substantially perpendicular to 6 '. Then, an annular flat plate-shaped blade 20 'is provided along the lower surface such as the hanging portion 6'. Except for the points described above, the grinding wheel 2'shown in FIG. 2 is substantially the same as the grinding wheel 2 shown in FIG.

In the embodiment shown in FIGS. 1 and 2, a support member 8 or 8'having a cylindrical hanging portion 6 or 6'is used, with the hanging portion 6 or 6'provided with a blade 20 or 20 '. However, instead of this, for example, a support member having a circular flat plate shape may be used, and a blade may be provided at an annular free end portion, that is, a peripheral portion of the support member.

In the method of the present invention, prior to grinding the surface of the silicon wafer by the blade 20 or 20 'of the grinding wheel 2 or 2'described above, the grinding wheel 2 or 2'of the grinding wheel 2 or 2'is fixed by a fixed aluminum oxide type abrasive dresser. It is important to dress the blade 20 or 20 '.

A manner of dressing the blade 20 of the grinding wheel 2 will be described with reference to FIG. The dresser 28 is held by a holder 30. The illustrated holder 30 is
It has a base 32 and a holding plate 34 fixed on the base 32. The base 32, which may be disk-shaped as a whole, has a circular recess 36 formed in the upper surface thereof, and a passage 38 extending downward from the circular recess 36. The passage 38 is connected to a suitable vacuum source (not shown). The holding plate 34, which may be disc-shaped, comprises a main part 40 made of a porous material and an annular outer part 42 fixed to the periphery thereof.
Is fixed to the base 32 by fixing the lower surface of the annular outer portion 42 to the upper surface of the base 32.
Covers the recess 36. Dresser 28 that can be disk-shaped
Is placed on the holding plate 34 and covers the main portion 40 thereof.

When a vacuum source (not shown) is activated, the holding plate 3
The air is sucked through the main portion 40, the concave portion 36 and the passage 38 of No. 4, and thus the dresser 28 is suction-held on the holding plate 34.

It is important that the dresser 28 is formed by bonding aluminum oxide type abrasive grains, preferably artificial crystal aluminum oxide (alundum) type abrasive grains. The artificial crystal aluminum oxide-based abrasive grains have a symbolic designation of A, 3
Those referred to as 2A, WA or RA etc. are conveniently used. The artificial crystal aluminum oxide type abrasive grains can be conveniently bonded by a vitrified bond method using a clay-like binder which is heated to be porcelain or a resinoid bond method using a thermosetting resin binder.

The grinding wheel 2 has a rotation axis 26 (FIG. 1) which is substantially perpendicular to the upper surface of the dresser 28. More specifically, the relative movement direction of the grinding wheel 2 with respect to the dresser 28 is indicated by an arrow 44. As seen from the above, the lower end 48 (FIG. 1) of the blade 20 at the rear end is slightly higher than the lower end 46 of the blade 20 at the front end by several tens of μm, so that the rotation axis 2 thereof with respect to the upper surface of the dresser 28 is very small.
Conveniently, the 6 (FIG. 1) is inclined. The grinding wheel 2 is rotationally driven about this rotation axis by a drive source (not shown) such as an electric motor drivingly connected to the rotation shaft 10. In addition, by moving the holding tool 30 in the direction indicated by the arrow 50, or alternatively or additionally, moving the grinding wheel 2 in the direction indicated by the arrow 44, the grinding wheel 2 and the dresser 28 are moved. Are relatively moved in the directions indicated by arrows 44 and 50, that is, in the direction substantially perpendicular to the rotation axis of the grinding wheel 2 and substantially parallel to the upper surface of the dresser 28. Thus, the dresser 28 is ground by the blade 20 of the grinding wheel 2, and the blade 20 is thereby dressed. The peripheral speed of the blade 20 during such dressing, the relative moving speed of the grinding wheel 2 and the dresser 28 in the directions indicated by the arrows 44 and 50, and the grinding depth t ₁ can be set appropriately.

In the method of the invention, after the dressing described above, the dressed blade 20 of the grinding wheel 2 is
The surface of the silicon wafer is ground by.

FIG. 4 shows a manner in which the surface of the silicon wafer 52 is ground by the blade 20 of the grinding wheel 2. Grinding is accomplished in a manner substantially similar to the dressing described above (in other words, the dressing described above grinds the surface of a silicon wafer, as will be readily understood by comparative reference to FIGS. 3 and 4). By grinding the dresser 28 in substantially the same manner). That is, the substantially disk-shaped silicon wafer 52 is placed on the holding plate 34 of the holder 30 with the surface to be ground facing upward, and is thus suction-held on the holder 34.
The grinding wheel 2 has its rotation axis 26 (FIG. 1) substantially perpendicular to the upper surface of the silicon wafer 52.
More specifically, when viewed in the relative movement direction of the grinding wheel 2 with respect to the silicon wafer 52 indicated by the arrow 44, the lower end 48 (FIG. 1) of the blade 20 at the rear end is more than the lower end 48 (FIG. 1) at the rear end. The rotation axis 26 (FIG. 1) is tilted with respect to the upper surface of the silicon wafer 52 so as to be about μm higher,
Conveniently located. The grinding wheel 2 is rotationally driven about its rotation axis 26. In addition, by moving the retainer 30 in the direction indicated by arrow 50, or alternatively or additionally, moving the grinding wheel in the direction indicated by arrow 44,
The grinding wheel 2 and the silicon wafer 52 are in the directions indicated by arrows 44 and 50, that is, the rotation axis 26 of the grinding wheel 2.
Relative to the upper surface of the silicon wafer 52 and substantially parallel to the upper surface of the silicon wafer 52. Thus, the upper surface of the silicon wafer 52 is ground by the blade 20. The peripheral speed of the free end of the blade 20 in such grinding is generally 200 to 30 in the grinding of the surface of the silicon wafer before making one surface a mirror surface, for example.
00 m / min, preferably 300 to 2000 m / m
in, particularly preferably 400 to 1300 m / min, and generally 1000 to 6000 m / min, preferably 1000 to 6000 m / min in grinding the other surface of the silicon wafer after the circuit is formed on one surface of the mirror surface. Is suitably 2000 to 5000 m / min. The relative moving speed of the grinding wheel 2 and the silicon wafer 52 in the directions indicated by the arrows 44 and 50 is generally desired to be 1000 mm / min or less.
The grinding depth t ₂ can be appropriately set according to the thickness of the silicon wafer 52 to be reduced by grinding, and for example, in the grinding of the surface of the silicon wafer before making one surface of the silicon wafer a mirror surface, To 10
To 20 μm, and in the grinding of the other surface of the silicon wafer after the circuit is formed on one surface of the silicon wafer which is mirror-finished, it is generally set to several μm to several hundred μm.

Also when using the grinding wheel 2'illustrated in FIG.
In the same manner as described above, the blade 20 'can be dressed, and then the surface of the silicon wafer 52 can be ground. However, when the grinding wheel 2 ′ shown in FIG. 2 is used, the grinding depth t ₂ becomes several μm due to the relatively large contact area between the silicon wafer 52 and the blade 20 ′. Tends to be limited.

According to the method of the present invention as described above, the surface of the silicon wafer 52 is ground, as is apparent from the later-described experimental example, to obtain a sufficiently good satin surface with substantially no saw marks or little saw marks. It can be done. When the surface of the silicon wafer 52 is repeatedly ground many times (for example, about 1000 times) after dressing the blade 20 or 20 ′, saw marks tend to gradually appear on the ground surface. 20 or 20 'can be dressed again.

Next, experimental examples and comparative experimental examples of the present invention will be described.

Experimental Example (1) A grinding wheel having a form as shown in FIG. 1 was prepared by the electrodeposition step and the subsequent melting step. More specifically, in the electrodeposition step, a Neckel plate was immersed in an electrolytic solution containing nickel ions to form an anode. Also, the first
An aluminum support member integrally formed with an annular protrusion as indicated by a chain double-dashed line 54 in the drawing is covered with an insulating material except for the inner surface and the lower surface of the hanging portion and the inner surface of the protrusion, and the inverted shape. In this state, it was immersed in the above-mentioned electrolytic solution, and this was used as the cathode. In the electrolytic solution, U.V. S. A synthetic diamond abrasive grain having a mesh number of 400 was agitated and floated. Then, electrolysis was started, and the abrasive particles dropped by gravity onto the non-coated portion of the support member were bolted by the deposited nickel, thus forming a blade. In the dissolving step, the supporting member having the formed blade was taken out of the electrolytic solution, the insulating material coating was removed only on the outer surface of the protruding portion of the supporting member, and then the supporting member was immersed in a caustic soda solution. Thus, the protruding portion of the supporting member was dissolved and removed. Thereafter, the support member was taken out of the caustic soda solution, and all the remaining insulating material coating was removed, thus producing a grinding wheel as shown in FIG. 1 The thickness of the free end of the blade in the produced grinding wheel Was 0.30 mm, the angle α (FIG. 1) formed by the axis of rotation and the free end of the blade was 135 degrees, and the outer diameter of the free end of the blade was 200 mm.

The blades of the grinding wheel were dressed in the manner described with reference to FIG. In this case, WA320NB (that is, U.S.P.
S. A disk-shaped dresser having a mesh number of 320 and a WA abrasive grain having a resinoid bond with a bond degree N) and having a thickness of 4 mm and an outer diameter of 4 inches was used. The peripheral speed at the free end of the blade was 1250 m / min. Hold the dresser holding the dresser in the direction indicated by arrow 50 at 150 mm / m
It was moved at a speed of in. The grinding depth t ₁ was 50 μm. Cooling water was sprayed on the grinding area.

After the above dressing, one side of the silicon wafer was ground in the manner described with reference to FIG. At this time, the peripheral speed of the free end of the blade is 1250 m.
It was / min. The holder holding the silicon wafer was moved in the direction indicated by arrow 50 at a speed of 150 mm / min. The grinding depth t ₂ was 15 μm. Cooling water was sprayed on the grinding area.

FIG. 5 is a photograph showing the surface of the silicon wafer ground as described above at 200 times magnification. As is clear from FIG. 5, the ground surface was a satin surface substantially free of saw marks.

Experimental Examples (2) to (5) One side of a silicon wafer was ground in the same manner as in Experimental Example (1) except for various conditions of A, B, C and D shown in Table 1 below. The ground surface of the silicon wafer was a satin surface substantially free of saw marks similar to the surface shown in FIG.

Experimental Example (6) U. S. Using synthetic diamond abrasive grains having a mesh number of 320, and the formed blade had a circumferential interval l of 1.5 at its free end as shown in FIG.
A grinding wheel was produced in substantially the same manner as in Experimental Example (1) except that the slot 56 having a width W of 1 mm and a depth d of 1 mm was formed.

Then, the used dresser is RA80NB (that is, U.S.P.
S. It is a dresser in which RA abrasive grains having a mesh number of 80 are resinoid bonded with a bond degree N), the peripheral speed of the free end of the blade is 650 m / min, and the moving speed of the holder is 80 mm / min. Other than, are experimental examples
The blade of the grinding wheel was dressed in the same manner as (1).

Then, the peripheral speed at the free end of the blade was 650 m / mi.
One side of the silicon wafer was ground in the same manner as in Experimental Example (1) except that the moving speed of the holder was 80 mm / min.

The ground surface of the silicon wafer was a satin surface substantially free of saw marks, similar to the surface shown in FIG.

Experimental Example (7) U. S. A synthetic diamond abrasive grain having a mesh number of 400 was resinoid-bonded to form a blade, and then the blade was adhered to a supporting member, thus producing a grinding wheel as shown in FIG. The outer diameter of the blade was 200 mm, the inner diameter of the blade was 190 mm, and the thickness of the blade was 2 mm.

Then, the blade of the grinding wheel was dressed in the same manner as in Experimental Example (1).

Thereafter, one side of the silicon wafer was ground in the same manner as in Experimental Example (1) except that the grinding depth t ₂ was 3 μm.

FIG. 7 shows the surface of the silicon wafer thus ground.
It is a photograph magnified 00 times. As is clear from FIG. 7, the ground surface was a satin surface with some saw marks.

Comparative Experimental Example (1) A blade of the same grinding wheel as that of the experimental example (1) was used, and the dresser used was GC320LV (that is, U.S.P.
S. A dresser that is vitrified-bonded with a green carbon random abrasive grain having a mesh number of 320 with a bond degree L).
Dressing was performed in the same manner as in Experimental Example (1) except that

After that, one surface of the silicon wafer was ground in the same manner as in Experimental Example (1).

Fig. 8 shows the surface of the silicon wafer ground in this way.
It is a photograph magnified 00 times. As is apparent from FIG. 8, the ground surface was a non-sheathed surface having prominent saw marks.

〔The invention's effect〕

According to the present invention, a mode of grinding the surface of a silicon wafer using a fixed superabrasive blade, that is, a mode that can be easily automated with sufficient work efficiency without causing problems such as contaminating the silicon wafer. Although it is possible to grind the surface of the silicon wafer with, the ground surface can be made to have a satin surface where there is substantially no saw mark or a small amount of saw mark.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a grinding wheel that can be used in the method of the present invention. FIG. 2 is a sectional view showing another embodiment of a grinding wheel that can be used in the method of the present invention. 3 is a partial cross-sectional view showing the manner of dressing the blade of the grinding wheel of FIG. 1 according to the present invention. FIG. 4 is a partial cross-sectional view showing the manner in which a surface of a silicon wafer is ground by the grinding wheel of FIG. 1 with a blade dressed according to the present invention. FIG. 5 is a photograph showing the surface of the silicon wafer ground in Experimental Example (1) at a magnification of 200 times. FIG. 6 is an enlarged partial front view showing the free end of the blade of the grinding wheel used in Experimental Example (6). FIG. 7 is a photograph showing the surface of the silicon wafer ground in Experimental Example (7) at a magnification of 200 times. FIG. 8 is a photograph showing the surface of the silicon wafer ground in Comparative Experimental Example (1) at a magnification of 200 times. 2 and 2 '... Grinding wheel 8 and 8' ... Supporting member 20 and 20 '... Blade 28 ... Dresser 30 ... Holding tool 52 ... .... Silicon wafers

Claims (1)

[Claims] 1. A blade of a fixed superabrasive grain disposed on an annular free end portion of a support member so that its rotation axis is substantially perpendicular to a substantially flat surface of a fixed aluminum oxide abrasive grain dresser. And the dresser are arranged, the blade is rotationally driven, and the blade and the dresser are relatively moved in a direction substantially perpendicular to the rotation axis of the blade, and the dresser is ground by the blade. By dressing the blade, and then arranging the blade and the silicon wafer so that the rotation axis of the blade is substantially perpendicular to the surface to be ground of the silicon wafer, and rotationally driving the blade. The blade and the silicon wafer are moved relative to each other in a direction substantially perpendicular to the rotation axis of the blade, and the blade and the silicon wafer are moved by the blade. A method of grinding a surface of a silicon wafer, the method comprising grinding the surface of the silicon wafer to a satin surface.