GB2362654A

GB2362654A - Diamond saw blade

Info

Publication number: GB2362654A
Application number: GB0112668A
Authority: GB
Inventors: Robert Carrol Runyon; David Walter Smith
Original assignee: KETECA USA Inc
Current assignee: KETECA USA Inc
Priority date: 2000-05-26
Filing date: 2001-05-24
Publication date: 2001-11-28
Also published as: GB0112668D0

Abstract

An electro-deposited nickel diamond dicing saw blade is made by depositing nickel in the presence of free diamonds which are encapsulated in a plating matrix of preferably nickel on a masked base. When making a blade using a prefabricated hub, the blade is deposited directly on a portion of the hub. When making a blade that is hubless, a blade is deposited on an unmasked portion of a flat sheet such as stainless steel. After plating the diamond dicing saw blade to a desired thickness the first plated side is smooth and the opposite side comprises exposed diamonds. The exposed diamonds are encapsulated by plating a matrix of nickel alone so as to equalize the exposed encapsulated diamonds on both sides of the saw blade. A subsequent operation of neutralizing or etching as least the smooth side of the diamond dicing saw blade is performed to leave an equal amount of exposed diamonds on both sides of the saw blades substantially completes the operation of the saw blade. Subsequent operations by the manufacturer or the customer include dressing the outside diameter of the saw blade to an exact eccentricity on the saw spindle, thus, grinding the blade to an exact dimension usually is not required during manufacture of the saw blade. The diamond saw blade is produced by the steps of providing a metallic base on which to plate a diamond saw blade, masking a portion of the base to prevent plating thereon, plating a holding matrix onto the base in the presence of free diamonds to form a diamond saw blade with diamonds encapsulated in the matrix leaving a smooth base side with no exposed diamonds and an exposed side with portions of diamond exposed, plating the exposed side with holding matrix material to substantially cover the exposed diamonds, and removing e.g by etching holding matrix material from at least the smooth base side to provide a diamond saw blade having exposed diamonds on both sides of the saw blade.

Description

2362654 1 DIAMOND SAW BLADE AND METHOD OF MANUFACTURE The present

invention relates to saw blades for use in dicing semiconductor wafers and substrates and is related to a co-pending application filed by the applicants on the same date and entitled "Laminated diamond saw blade and method of manufacture".

Heretofore, there have been manufacturers of what are referred to as "diamond" cuffing saw blades, which include "diamond" dicing saw blades having diamonds, or synthetically made diamond like material, attached or bonded directly on to a metal blade, leaving a substantially uniform coating of diamonds or diamond-like material on the cutting edge of the disk-shaped saw blade. A typical example of the deposition of abrasive particles onto a disk of a hub is shown and described in U.S. Patent No. 6,008,069, which uses an electro-deposited form of hard carbon. It was thus known that diamond-like carbon films could be deposited onto metal disks or hubs.

The disadvantage of having a metal core or carder blade is that the diamonds on the cutting face come loose and fall away, and the blade is soon worn out.

The metal core blade was also relatively thick and not well suited for cutting an individual die from a wafer. As wafer technology has progressed, the wafers have become larger, and the die or semiconductor devices have become smaller leaving very small separations or streets between individual dies. This has resulted in the need for dicing saw blades which are no thicker than twelve microns thick. Such blades, made for dicing small semiconductor devices, are usually made by electro-depositing nickel on a masked plate or onto a flat portion of a prefabricated hub in the presence of free diamond particles so as to encapsulate small diamonds uniformly throughout the electro deposited nickel saw blade. Such saw blades are made in thicknesses of 12 2 microns up to 200 microns encapsulating diamonds that have a size range from 1-3 microns up to 30-50 microns.

A problem with such thin electro-deposited dicing saw blades is that the process steps must be carefully controlled in order to produce a stress free deposited nickel for carrying the diamonds. Both hubless dicing saw blades and those made onto fabricated hubs have a tendency to wear more on one side than the other. This tendency has resulted in cuts that are not substantially vertical or orthogonal to the substrate surface being cut, so that the edges of 10 the cut of the wafer are not smooth.

Accordingly, it would be desirable to provide a nickel electro-deposited dicing saw blade that is both smooth cutting and can be made to a predetermined controlled blade thickness.

Features of a dicing saw blade to be described below, by way of example, in the belief that they will enable the invention to be better understood, are that it cuts vertically through a wafer with a minimum of chipping and cracking on the top and bottom surfaces of the wafer, and that it 20 runs vertically true without rippling during a cutting operation.

A method for producing saw blades with equal diamond exposure on all sides of the cutting edges will also be described below, by way of example, in the belief that it will enable the invention to be better understood.

A particular diamond dicing saw blade made by electro-depositing stress free nickel in the presence of free diamonds, so that the diamond saw blade runs vertically true without creating rippling stresses during a cutting operation, will also be described below, by way of example, in the belief that it 30 will enable the invention to be better understood.

3 In a particular arrangement to be described below, by way of example, a diamond saw blade is made so that it minimises side thrust generated in the diamond saw blade, by electro-depositing a nickel matrix holding material onto a mandrel or base in the presence of free diamonds, so that no diamonds protrude from, or are exposed on, the smooth side plated on the base, and so that there are exposed, or partially exposed, encapsulated diamonds on the side opposite to the smooth side. Subsequently an additional matrix of holding material is elect ro-depos ited onto the exposed or partially exposed encapsulated diamonds to equalize the exposed diamonds on both sides, thus equalizing the side thrust generated by the exposure of diamonds on both sides.

Previously proposed arrangements will now be described with reference to Figs. 1 to 7 of the accompanying drawings, and arrangements, which it is believed will enable the invention to be better understood, will be described, by way of example, with reference to Figs. 8 to 11 of the accompanying drawings.

Figure 1 is a plan view of an integrated hub type diamond dicing saw blade, Figure 2 is a side view in cross sectional elevation of the hub and saw blade shown in Figure 1, Figure 3 is an enlarged side view of a cutting edge or the tip of the saw blade shown in Figures 1 and 2, Figure 4 is a section, in elevation, of a typical saw blade showing a bullet nose wear pattern that occurs during cutting and that causes bottom cracking, 4 Figure 5 is an enlarged section, in elevation, of the cutting tip of a saw blade before being worn in, Figure 6 is an enlarged section, in elevation, of the cutting tip of a dicing saw blade after being worn in by cutting wafers, Figure 7 is a section, in elevation, taken through a wafer after being cut by the saw blade shown in Figure 6, Figure 8 is an enlarged section, in elevation, of the cutting tip of a saw blade of the type shown in Figure 5 after a first equalizing step, Figure 9 is an enlarged section, in elevation, of the cutting tip of a saw blade after a second equalizing step has been performed on the saw blade of 15 Figure 8, Figure 10 is a block flow diagram for use in describing the steps performed in making a smooth cutting saw blade on a prefabricated aluminium hub, and Figure 11 is a block flow diagram for use in describing the steps performed in making a smooth cutting hubless saw blade for use in a chuck or hub clamping device.

Refer now to Figures 1 and 2 showing a previously proposed integrated hub type diamond dicing saw blade (10) having an electro- deposited diamond encapsulated saw blade (11) attached to a mounting face (15) of the hub, which includes an opposite mounting flange (12) and recesses (13) and (16) for marking and identification purposes, and an internal diameter or opening I.D. (14). The saw blade (11) is deposited on a portion of aluminium of the hub which has been removed on one side behind the saw blade (11). This type of blade is known and is used for dicing saw blades having a thickness from approximately 0.5 to 8 mils in thickness.

Refer now to Figure 3, which shows an enlarged side view of a cutting 5 edge of a previously proposed saw blade of the type shown in Figures 1 and 2. The saw blade (11) is shown moving counter clockwise while the wafer (17) is shown moving from left to right, so that the blade (11) creates a compressive force at the upper surface and a shear force at the lower surface (19), which causes chipping and cracking to occur as the blade exits at point 21.

Refer now to Figure 4, which shows a section, in elevation, of a typical previously proposed saw blade of the type shown in Figure 3 having a bullet nose (22) which occurs as a result of the wear characteristics of diamond saw blades and causes cracking at the point (21). The crack is diagonal and is wider than the thickness of the saw blade. When the saw blade plunges completely through the wafer (17) there are still cracks at the bottom surface (19). Such cracks may be minimized by reducing the size of the diamonds or diamond particles encapsulated into the nickel saw blade (11). As the diamond particles are made smaller to reduce chipping, the cutting rate or speed of cutting the wafer (17) is substantially reduced. It is generally accepted that the size of the diamond particles presently used in diamond saw blades for cutting silicon wafers is acceptable at 2-6 microns. This results from specifications for the width of the street being cut by the saw blade having a plus or minus width dimension and it is known that an ideal blade using the ideal size diamond particles will cut a curff three to ten-thousandths wider than the thickness of the saw blade having exposed diamonds on the side.

Refer now to Figure 5 showing an enlarged section, in elevation, of the cutting tip of a previously proposed nickel electro-deposited saw blade before being worn in. It will be noted that the diamonds on the left side of the blade (11) are all inside the matrix of the nickel and that none is exposed from 6 the outer surface (22) of the blade (11). In contrast thereto the diamonds on the right side of the blade (11) are partially exposed, once the electrode depositing process has been stopped, leaving a surface (23) with exposed diamonds (24). Diamond saw blades of the type shown in Figure 5 are used for sawing wafers, or are post-treated by electro- polishing, before being used as a saw blade.

Refer now to Figure 6 showing an enlarged section of the cutting tip of a previously proposed dicing saw blade after being worn in by cutting wafers, and having a bullet nose. The smooth surface (22) has no exposed diamonds and the opposite side or exposed surface (23) has exposed diamonds (24). As the blade (11) wears in, it forms a bullet nose having additional exposed diamonds and creates a force pattern shown by the arrows (24). The force or thrust on the saw blade (11) causes the flexible saw blade (11) to bend from the vertical, as shown in Figyre 6.

Refer now to Figure 7 showing a section, in elevation, taken through a wafer (17), after the saw blade shown in Figure 6 has been removed. Due to the force concentration shown by the arrows (24) on the tip of the working face of the blade (11) there is acurff oracut (25) formed in the wafer (17), which is substantially identical to the blade (11), and is tilted from the vertical shown by the line 26. It is known in the blade manufacturing art that, when the blade (11) shown in Figure 6 completes its path through the wafer (17) shown in Figure 7, the chips caused by the exit of the tilted blade from the wafer are enlarged on the right side of the blade, where the bullet nose is most pronounced. Thus, it would be desirable to provide an electro-deposited diamond saw blade that would cut true and vertically through a wafer (17).

Refer now to Figure 8 showing an enlarged section, in elevation, of the cutting tip of a saw blade of the type shown in Figure 5 after a first equalizing step has been performed in the process of making the blade (11 A).

7 The step performed is to electro-deposit stress-free nickel on top of the surface (23), so as to encapsulate the diamonds (24) to a predetermined depth or height needed for the following step of equalization, which will now be explained.

Refer now to Figure 9, which shows an enlarged section, in elevation, of the cutting tip of the diamond dicing saw blade (11 A) after a second equalizing step has been performed. After depositing the additional matrix of nickel (25), the surface (26) shown in Figure 8, as well as the surface (22), are etched away or equalized, so as to expose an equal amount of diamonds (24) on both sides of the equalized saw blade (11 B) It has been found that exposing an equal amount of diamonds at the cutting sides and the cutting face of the dicing saw blade (11 B) causes the blade (1113) to cut vertically and true and smooth through wafer (17) so as to - minimise the cracks at both the top and the bottom. The cracks and chips may be further reduced by using smaller diamonds (24), as explained hereinbefore.

Refer now to Figure 10, which shows a block diagram for use in describing, by way of example, the steps performed in making the smooth cutting saw blade on a prefabricated aluminium hub, which it is believed will enable the invention to be better understood. There are six blocks numbered 26-29, 31 and 32 shown in Figure 10, that are substantially selfexplanatory. In block 26 a blade is produced on a supporting hub of the type shown in Figure 2 Portions of the hub are masked, as shown in block 27, so that the blade 11 can be plated as an annular ring on the hub, as shown in block 28. Since the plating operation occurs on a blade which has aluminium on the back side of the blade (11), it is necessary to grind the tip or cutting edge of. the saw blade and then remove the hub material behind the blade (11) to expose the flat sides of the blade (11) as shown in block 29. Afterthe blade (11) has been made, as shown 8 in Figure 5, an additional matrix of nickel (25) is plated on top as a holding layer on the exposed side (23) to build up a layer of holding matrix nickel, as shown in block 31. Next, the newly made blade is etched or equalized by other processes to expose an equal amount of diamonds on both sides of the cutting blade (11), as shown in block 32. The preferred manner of performing the operation is etching, because all three surfaces can be etched simultaneously. However, other types of polishing operations are known and could be performed, as shown in block 32. The finished blade is now ready for mounting on the spindle of a dicing saw and in the preferred manner of operation in the manufacture of a dicing saw, the outside diameter of the saw blade (11) is again dressed for eccentricity to the spindle of the diamond saw.

Refer now to Figure 11 showing a block diagram for use in describing the steps performed, by way of example, in making a particular smooth cutting hubless saw blade for use in a chuck or hub clamping device, which it is believed will enable the invention to be better understood. The blocks 33 through 38 are substantially self-explanatory, some of which are known as having been proposed previously. Photo resist material is used to mask a conductive metal sheet to leave an annular ring exposed on a flat sheet, as shown in block 33. Then a hubless diamond dicing saw blade of nickel and diamonds is plated on the flat sheet, as shown in block 34. The upper surface of the plated diamond saw blade has exposed diamonds, thus a plating operation of a holding layer on top of the exposed diamonds is next performed, as shown in block 35, to entrap the exposed diamonds.

Subsequently, the diamond saw blade is removed from the sheet, as shown in block 36. The blades are mounted so as to expose the flat sides and the cutting edge of the diamond saw blade, as shown in block 37. Block 38 shows that the diamond saw blade is etched under control on at least the smooth sides of the saw blades, but preferably including the cutting edge,

9 leaving submetrically exposed diamonds on the opposite sides, as well as the cutting edge as shown in block 28. This diamond saw blade may be mounted together with separator sheets, so as to stabilize and hold a plurality of such diamond dicing saw blades. Then the outside diameter may be ground to provide a uniform outside diameter. However, in practice, once the individual hubless diamond dicing saw blade is chucked and clamped into a hub, the diamond dicing saw is again dressed to provide an exact eccentric outside diameter cutting tip for the start of cutting operations.

Having explained a particular arrangement by way of example in the belief that it will enable the present invention to be better understood, it will be appreciated that, some modification may be made, for example in the steps shown in Figures 9 and 10. In one example, when plating the holding matrix of nickel on to the already made blade (11), so as to encapsulate the exposed diamond, the controlled plating operation may be stopped, so as to leave a predetermined amount of exposed diamonds on one surface, and then only to etch the opposite smooth surface to equalize the exposed diamonds on both sides. Since the cutting edge of diamond saw blades are always ground at least once in an operation subsequent to using the diamond saw blade, it is not necessary to etch the cutting edge of the saw blade, because it is going to be ground and dressed before use.

It will thus be appreciated that although particular arrangements have been described, by way of example, in the belief that they will enable the invention to be better understood, variations and modifications thereof, as well as other arrangements may be conceived within the scope of the appended claims. For example, the base may include a flat stainless steel plate to which the matrix material does not bond chemically, the saw blade being removed from the base prior to the removal of the matrix holding material from the side of the base. In one arrangement, the exposed side of the base is plated with holding matrix material to a depth to cover up to ninety per cent of the exposed edges of the diamonds on the exposed side, and the size of the free diamonds to be encapsulated in the matrix material is between 2.5 and 8 microns.

11

Claims

1. A method of making a diamond saw blade for smooth cuffing substrate materials, including the steps of providing a metallic base on which to plate a diamond saw blade, masking a portion of the base to prevent plating thereon, plating a holding matrix onto the base in the presence of free diamonds to form a diamond saw blade with diamonds encapsulated in the matrix leaving a smooth base side with no exposed diamonds and an exposed side with portions of diamond exposed, plating the exposed side with holding matrix material to substantially cover the exposed diamonds, and removing holding matrix material from at least the smooth base side to provide a diamond saw blade having exposed diamonds on both sides of the saw blade.

2. A method as claimed in claim 1, wherein the metallic base includes an aluminium hub, and the step of plating a holding matrix onto the base includes bonding the holding matrix onto the aluminium, and subsequently removing base material from the base side of the saw blade to expose the smooth base side of the saw blade.

3. A method as claimed in claim 2 wherein the step of removing base material includes etching away aluminium from the smooth base side.

4. A method as claimed in claim 1, wherein the base includes a flat stainless steel plate to which the matrix material does not chemically bond, and includes the step of removing the saw blade from the base prior to removing holding matrix material from the base side.

5. A method as claimed in claim 1 wherein the step of plating the exposed side with holding matrix material includes plating to a depth to cover up to ninety percent of the exposed edges of the diamonds on the exposed side.

12 6. A method as claimed in claim 5 wherein the step of removing holding matrix material from the smooth base side includes only removing enough matrix material to match the exposure edges of diamonds on the exposed side.

7. A method as claimed in claim 1 which includes selecting the size of the free diamonds to be encapsulated in the matrix material to a size between 2.5 microns and 8.0 microns consistent with the thickness of the saw blade, and selecting the smaller sizes of diamonds consistent with a desired cutting speed.

8. A diamond saw blade for cutting substrate materials including a diamond saw blade having an electroplated holding matrix material, free diamonds encapsulated into the holding matrix material, edge portions of some of the diamonds extending out of the matrix material on both sides of the saw blade being substantially equal, thereby balancing side thrust generated by the exposed diamonds during a sawing operation.

9. A saw blade as claimed in claim 8 wherein the average area of the exposed diamonds on both sides of the saw blade is substantially equal.

10. A saw blade as claimed in claim 8 wherein the average height of the exposed diamonds on both sides of the saw blade is substantially equal.

11. A method of minimising side thrust generated in diamond saw blades, including the steps of making a diamond saw blade by electro-depositing matrix holding material onto a mandrel or base in the presence of free diamonds, so that no diamonds protrude from or are exposed on the side plated on the base, and that exposed partially encapsulated diamonds are exposed on the side opposite the smooth side, and electro-depositing additional matrix holding material onto the exposed partially encapsulated diamonds to equalize the side thrust generated by a cutting operation.

13 12. A method as claimed in claim 11 which includes the step of etching away elect ro-de posited matrix holding material on at least one side to partially expose equal amounts of partially encapsulated diamonds on both sides.

13. A method as claimed in claim 1 or claim 11 substantially as described herein with reference to Figs. 8 to 10 or 8, 9 and 11 of the accompanying drawings.

14. A diamond saw blade made by a method as claimed in claim 1, 11 or 13, 10substantially as described herein with reference to Figs. 8 to 10 or 8, 9 and 11 of the accompanying drawings.