JPH0822508B2 - Ultra-thin blade grindstone - Google Patents

Description

TECHNICAL FIELD The present invention relates to an ultra-thin blade grindstone used for cutting and dividing a chip from a semiconductor wafer and for precision cutting of ferrite and the like.

"Prior Art" Fig. 5 is a view showing an example of this type of ultra-thin blade grindstone (electroformed thin-edge grindstone).

This electroformed thin blade grindstone 1 is a thin-walled annular wheel with a thickness of 15 to 50 μm formed by dispersing superabrasive grains such as diamond and CBN in a metal plating phase made of Ni, Co or their alloys. Yes, both sides are sandwiched by a pair of flanges 2, 2 and fixed to the grindstone shaft 3 with a nut 4 for use.

[Problems to be Solved by the Invention] By the way, when a semiconductor wafer is cut and divided by the electroformed thin blade grindstone 1 as described above, conventionally, the wafer is not completely cut, but a groove is formed up to a middle portion of the wall thickness. A half-cut method has been used in which the wafer is diced, and then the wafer is crushed to divide the chip into chips. However, this method requires time and cost for the pressing and splitting process, and the shape of the chip cutting surface may become defective. Recently, the tape is adhered to the back surface of the wafer to completely cut the wafer. The cutting method is becoming mainstream.

However, in such a full-cut method, the grinding resistance inevitably increases by increasing the cutting depth of the grindstone, and since the grindstone cutting edge reaches the tape on the back surface of the wafer, this tape material adheres to the cutting edge. The sharpness of the grindstone is deteriorated, and an excessive force is applied to the grindstone, resulting in frequent breakage. In addition, there is a drawback that the cutting margin becomes large due to the wobbling of the grindstone during grinding,
From the standpoint of improving the yield of wafers, there is a strong demand for a highly rigid grindstone capable of making deep cuts.

"Means for solving the problem" The present invention has been made to solve the above problems,
In addition to superabrasive grains, high-strength ceramic whiskers are oriented in a direction orthogonal to the axis of the grindstone and dispersed in the metal plating phase.

The high-strength ceramic whiskers preferably have a fiber diameter of 2 μm or less and an aspect ratio of 10 or more.

Also, the content of the ceramic whiskers is 3 to 40.
It is desirable to be vol%.

Furthermore, as the ceramic whisker, β-Si ₃ N
₄ may be used.

[Examples] Hereinafter, examples of the present invention will be described in detail with reference to the drawings.

1 and 2 show an example in which the present invention is applied to an electroformed thin blade grindstone (extra thin blade grindstone) for dividing and cutting a semiconductor chip.

This electroformed thin blade grindstone has a thickness obtained by uniformly dispersing high-strength ceramic whiskers 11 ... And superabrasive grains 12 such as diamond or CBN in a metal plating phase 10 made of Ni, Co or their alloys. It is a thin circular ring with a thickness of 15 to 50 μm, and the high-strength ceramic whisker 11 ...
As shown in FIG. 2, most of them are oriented in a direction orthogonal to the axis of the grindstone.

The material of this ceramic whisker 11 is β-
Si ₃ N ₄ , alumina, beryllia, boron carbide, silicon carbide,
It is selected from inorganic fibers composed of silicon nitride, potassium titanate, etc., and one kind or a plurality of kinds are mixed and used. In particular, β-Si ₃ N ₄ is suitable for the present invention, and the reason is as follows.

The specific gravity of β-Si ₃ N ₄ is 3.18, and the specific gravity of diamond abrasive grains is 3.5.
It is relatively close to the specific gravity of 3.49 for CBN abrasive grains and is easy to co-deposit with them.

Due to its manufacturing method, β-Si ₃ N ₄ makes it easier to obtain thick whiskers compared to other ceramic whiskers.Because of its high rigidity, whiskers do not easily get entangled with each other, and the dispersibility is far superior to other materials. There is.

In addition to β-Si ₃ N ₄ , boron carbide, silicon carbide, potassium titanate, etc. may be mentioned as those having a density relatively close to that of superabrasive grains.

On the other hand, regarding the shape of the whiskers, the fiber diameter is 2 μm.
In the following, it is desirable that the aspect ratio is 10 or more,
More preferably, the aspect ratio is 20 or more. When the fiber diameter is larger than 2 μm, the protrusion amount of the whiskers 11 ... From the metal plating phase 10 becomes large, the thickness accuracy of the grindstone decreases, and the effect of improving the grindstone rigidity per whisker content decreases, which is preferable. Absent. If the whisker 11 has an aspect ratio of less than 10, the effect of improving the rigidity of the grindstone becomes insufficient.

In particular, when β-Si ₃ N ₄ is used, it is desirable that the average fiber diameter is 0.5 to 1 μm or less, the aspect ratio is 20 to 100, and the fiber length is 10 to 50 μm. The entanglement of the whiskers described above is further reduced, good dispersibility is obtained, and the effect of improving the rigidity of the grindstone can be further enhanced.

Further, the content of the whiskers 11 ... In the metal plating phase 10 is preferably in the range of 3 to 40 vol%. If it is less than 3 vol%, the effect of improving the rigidity is small, and if it is more than 40 vol%, the protrusion density of the superabrasive grains 12 ... From the metal plating phase 10 is relatively lowered, and the sharpness of the grindstone is lowered.

On the other hand, the average grain size of the superabrasive grains 12 is 3 to 7 μm, and the content in the metal plating phase 10 is 5 to 25 vol%.
The range of the particle size is a suitable value according to the thickness of the grindstone. Further, the upper limit of the abrasive content is slightly smaller than the conventional electroformed blade grindstone (content about 3 vol%), but this increases the amount of metal plating phase 10 exposed on the surface of the grindstone, This is for further enhancing the self-sharpening action of the abrasive grains 12.

Next, a method of manufacturing such an electroformed thin blade grindstone will be described.

FIG. 3 is a sectional view of the grindstone manufacturing apparatus. Reference numeral 20 in the drawing denotes a plating tank in which an agitator is arranged, and a non-conductive pedestal 21 is horizontally arranged in the plating tank 20. A flat substrate 22 made of stainless steel is placed on the pedestal 21, and the upper surface of the flat substrate 22 is masked while leaving a prototype-shaped portion of a grindstone to be manufactured. Further, an anode plate 23 is arranged above the plane substrate 22 in parallel therewith.

For plating, the flat substrate 22 is connected to the cathode of the power source and the anode plate 23 is connected to the anode of the power source, and the plating solution M in which the superabrasive grains 12 ... And the ceramic whiskers 11 ... While energizing. Then, on the flat substrate 22, the metal plating phase 10 is deposited while gradually incorporating the whiskers 11 and the superabrasive grains 12 that are horizontally attached to the surface thereof, and the abrasive grain layer 24 is formed. Eventually, when this reaches a predetermined wall thickness, the energization is stopped and the flat substrate 22 is moved to the abrasive grain layer.
24 is peeled off and washed and shaped to obtain an electroformed thin blade grindstone.

In the above electroformed thin blade grindstone, the metal plating phase
Since a large number of ceramic whiskers 11 ... Are dispersed in 10 and these whiskers 11 ... Are oriented in a direction orthogonal to the axis of the grindstone, deformation of the metal plating phase 10 in this direction is suppressed, and The rigidity is increased and the deflection is reduced. Therefore, even when it is used in the full-cut method of deeply cutting into a wafer, it can sufficiently withstand a large grinding resistance, and even if the tape material adheres to the cutting edge and the sharpness is reduced, there is little risk of damage.

Further, as the rigidity of the grindstone is improved, the wobbling of the cutting edge during grinding is reduced, and the waste (kerf loss) of the cutting margin due to this wobbling can be reduced, so that the yield of wafers can be improved. .

Furthermore, in this grindstone, whiskers fall off from the grinding surface during grinding as appropriate, and chip pockets are formed in the traces, so this chip pocket enhances the chip discharge performance and the self-developing action of superabrasive grains. It is possible to promote and improve the sharpness of the grindstone.

The present invention is not limited to the disk type electroformed thin blade grindstone as in the above embodiment, but a shape in which the ultrathin blade grindstone body 30 and the hub 31 made of aluminum alloy are integrally formed as shown in FIG. May be

Further, during plating, the surface of the whiskers 11 may be preliminarily subjected to electroless plating or the like, in which case the adhesive force between the metal plating phase 10 and the whiskers 11 can be increased.

Further, the whiskers 11 ... May be radially oriented around the axis of the grindstone by adjusting the plating solution stirring method at the time of plating, in which case the rigidity of the grindstone can be further improved.

Furthermore, the above description was about an example in which the present invention is applied to a semiconductor chip division cutting grindstone, but the present invention is not limited to this, and a precision cutting grindstone such as ferrite (thickness 50 to 400 μm, ultra The average grain size can be minimized to 5 to 70 μm), and in that case, the same excellent effect as described above can be obtained.

"Experimental Example" Next, the effect of the present invention will be demonstrated with an experimental example.

First, using a plating solution having the following composition, four types of electroformed thin blade grindstones having different types of whiskers were prepared by the apparatus shown in FIG. The shape of the grindstone is 50.4mmφ x thickness
Unified to 25 μm x 40 mmφ inner diameter.

(Plating solution composition) sulfamate Ni: 450 g / chloride Ni: 30 g / boric acid: 40 g / brightener, a pit preventing agent: each minor PH4.0 Temperature: 50 ° C. Cathode current density: 3A / dm ² diamond abrasive concentration: 100g / Whisker concentration: 100g / (other than β-Si ₃ N ₄ ): 20g / (β-Si ₃ N ₄ ) Next, the above 4 types of electroformed thin blade grindstones and normal electroformed thin blade grindstones of the same size (comparison Example) and, under the following conditions, 5
The grinding test was performed one by one.

(Grinding conditions) Work material: 5 inch φ silicon wafer (0.5 mm thickness) (Fixed to the table with 0.07 mm thick bonding tape) Rotation speed: 30,000 rpm Feed rate: 100 mm / sec. Depth of cut: 0.52 mm Cutting edge Overhang: 0.7 mm Cutting distance: 50,000 lines The results are shown in the following table.

As is clear from the above table, in the electroformed thin blade grindstones of Experimental Examples 1 to 3 containing whiskers, the frequency of wheel breakage could be significantly reduced.

[Advantages of the Invention] According to the ultra-thin blade grindstone of the present invention, the high-strength ceramic whiskers dispersed in the metal plating phase can enhance the rigidity of the grindstone and suppress the bending. Therefore,
It can sufficiently withstand a large grinding resistance when used in the full-cut method of cutting deeply into a wafer, and even if the tape material adheres to the cutting edge and the sharpness is reduced, there is little risk of breakage. Further, by improving the rigidity of the grindstone, it is possible to reduce the waste of the cutting margin due to the deflection of the cutting edge during grinding, and it is possible to improve the yield of wafers.

[Brief description of drawings]

1 and 2 are a plan view and a sectional view of an electroformed thin blade grindstone (extremely thin bladed grindstone) according to an embodiment of the present invention, FIG. 3 is a sectional view of a manufacturing apparatus for the grindstone, and FIG. 4 is the present invention. FIG. 5 is a cross-sectional view of another embodiment, and FIG. 5 is a cross-sectional view showing a mode of use of a conventional electroformed thin blade grindstone. 10 …… Metal plating phase, 11 …… High strength ceramic whiskers, 12 …… Super abrasive grain.

Claims (4)

[Claims] 1. An ultra-thin blade grindstone characterized in that a high-strength ceramic whisker, most of which is oriented in a direction orthogonal to the axis of the grindstone, and superabrasive grains are dispersed in the metal plating phase. 2. The ultrathin blade grindstone according to claim 1, wherein the ceramic whisker has a fiber diameter of 2 μm or less and an aspect ratio of 10 or more. 3. The content of the ceramic whiskers is 3
Claim 1 characterized in that it is -40 vol%
Item 2. An ultra-thin blade grindstone according to item 2 or item 3. 4. The ceramic whisker is β-Si ₃ N
_The ultrathin blade grindstone according to claim 1 or 2 or 3 characterized in that it is ₄ .