JPH02224976A - Inner periphery type metal bonded abrasive cutting wheel and using method and manufacture thereof - Google Patents

Abstract

PURPOSE:To reduce the clogging and deformed friction loss of an inner peripheral cutter caused by the cutting of a semiconductor single crystal bar, etc. by using iron powder for the chief ingredient of a bonding agent which is fixed to the inner peripheral end face of an annular metal base board and both sides of its vicinity. CONSTITUTION:A bonding agent with which super abrasive grains 12 are mixed is fixed to the inner peripheral end face of an annular metal base board 10 and both sides of its vicinity to form an inner peripheral cutter. Iron powder is used for the chief ingredient of the bonding agent. Thereby, the clogging and deformed friction loss of the inner peripheral cutter caused by cutting a semiconductor single crystal bar, etc. can be reduced while reducing the depth of the abnormal machining distortion layer or average machining distortion layer of the surface layer of a wafer, etc. after cutting, to obtain a specular semiconductor single crystal base board of high accuracy and high quality.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an internal metal bond cutting grindstone for cutting semiconductor single crystal rods and the like into wafers, a method of using the same, and a method of manufacturing the same.

[Prior Art] Yamond abrasive grains 12 are fixed by electrodeposition (also called electroforming) processing of hard and brittle materials, especially semiconductor single crystals and ceramics. Precision machining using diamond abrasive grains (1) has recently received particular attention.2 (2) has one or two layers, and when it falls off, it cuts. Hard and brittle materials generally lose their ability to increase tensile strength to compressive strength.

very small compared to Therefore, when processing hard and brittle materials, the electrodeposition method is recommended.
Starting from the point where the external force exceeds the tensile strength, diamond abrasive grains 12, etc. are placed on the inner peripheral edge of the alloy and on the top and bottom surfaces where a series of minute fractures begin.
0 is nickel plated.
It is done by

The reason behind the development of the semiconductor industry is, of course, that the internal metal bond cutting wheel was developed to minimize the cutting allowance when cutting a bar due to the need for advances in the technology for supplying semiconductor single crystal semiconductor materials. However, it is a semiconductor single-crystal rod cut almost perpendicular to the axial direction, and of course it is made of alloys.
The grinding wheel itself is also thin and grinds to form circular flakes (wafers) with a surface layer. The thickness of this whetstone is usually 200-32
The thickness of the gold is usually 100 to 200 μm. The series of steps to form a diamond, especially the semi-abrasive layer, which is a hard and brittle material, is limited to two layers at most. The abrasive grains 12 used in the process of cutting diamond conductor single crystal rods have a diameter of about 40 to 70 μm, and the development of internal metal bond cutting wheels is of great significance.
This diameter had the effect of adhering the abrasive grains to the metal bond.

selected empirically from the viewpoint of cutting force and cutting force.

This inner circumferential type metal bond cutting whetstone is shown in FIG.

5301 or 5US304 (1) Semiconductor single crystal rods tend to become fine powder during cutting, and furthermore, the diamond abrasive grains 12 fall off, etc.
Since clogging easily occurred, the cutting ability was significantly reduced.

(2) Since the number of diamond abrasive grains 12 is small, if they fall off, the cutting ability tends to be anisotropic.
Warpage occurred in the semiconductor wafer, causing wafer failure.

(3) Due to this anisotropy, deep processing distortions reaching several tens of micrometers may occur in the wafer surface layer in some cases. Such processing distortion deteriorates the mirror crystal quality of the mirror semiconductor wafer, which is the final processed product, or causes the uneconomical need to remove the wafer surface unnecessarily.

Conventionally, when cutting a semiconductor single crystal rod with an internal metal bond cutting grindstone, a mechanical dressing method has often been used to prevent the above-mentioned clogging. This method involves mechanically removing semiconductor single crystal chips adhering to the surface of the grinding wheel by cutting the hard and brittle material, or mechanically scraping off the metal part of the electrodeposited layer to create new diamond abrasive grains. This is a method of exposing. By doing this, although there is a time-saving effect, it is possible to interrupt the cutting operation for dre-sowing, or the grindstone part of the cutting edge becomes symmetrical with respect to the base metal 10 during dre-sowing. If the blade is not removed and the blade edge becomes asymmetrical, the direction of travel of the blade edge deviates from the alloy surface during slicing, causing warpage in the cut thin piece. As described above, even with dressing, it is difficult to sufficiently prevent warping of the cut thin sections, and the cutting operation is interrupted, resulting in a decrease in productivity and an increase in costs.

In order to solve this dressing problem, a nozzle block is provided that has a plurality of cutting fluid discharge holes and small air jet holes arranged parallel to the rotating surface of the thin inner cutting blade, and the grinding fluid is directed toward the cutting blade. A method has been proposed in which clogging is prevented by discharging air and blowing out air at the same time (Japanese Patent Application Laid-Open No. 1983-1999).
Publication No. 9709).

However, with this method, grinding fluid and air are simply ejected near the cutting edge, and the ejected energy alone breaks down and detaches the fine powder layer of the hard and brittle material that is the cause of clogging, so it is not effective. is limited. The cutting blade rotates at high speed, and the cutting edge has a circumferential speed of 1000 to 3500 m/min.
Even at 00m/min, the time required for rotation is only 0.00m/min.
It is 05 seconds. Therefore, even if a large amount of cutting fluid is discharged from multiple positions near the cutting edge, it is difficult to remove the attached fine chips using normal cutting fluid.

[Problems to be Solved by the Invention] In view of the above-mentioned problems, an object of the present invention is to prevent clogging and deformation wear of the inner peripheral blade due to cutting of semiconductor crystal rods, etc., and to prevent cutting by the inner peripheral blade. Inner periphery type metal for obtaining a high-precision, high-quality mirror-finished semiconductor single-crystal substrate by reducing the depth of the abnormal processing-strained layer or the average processing-strained layer on the surface layer such as post-processing. The present invention provides a bond cutting grindstone, a method for using the same, and a method for manufacturing the same.

[Means for Solving the Problems] In order to solve the problems described in item 2, the present invention provides (1) a bonding agent mixed with superabrasive grains on the inner circumferential end surface of the annular metal substrate and both surfaces in the vicinity thereof. The main component of the bonding agent is placed on the iron powder in an internal metal bond cutting grindstone that is fixed to form an internal cutting edge.

The material for the superabrasive grains is preferably diamond, but cubic boron nitride or the like may also be used. The particle size of the abrasive grains is 5
It is preferably within the range of ~60 μm.

As the binder, it is preferable to use at least one type of iron powder having a particle size of about 1/1 of that of the superabrasive grains, mixed with silicon powder.

(2) This internal metal bond cutting wheel is produced by, for example, iso-static press-forming a mixture of superabrasive grains and a binder together with a circular metal substrate, sintering it in an inert or reducing atmosphere, and then applying electrolytic action. It is manufactured by finishing the cutting edge to the specified dimensions.

(3) Also, using this internal metal bond cutting wheel,
When obtaining a wafer by cutting a semiconductor single crystal rod almost perpendicularly to its axial direction, it is preferable to use diamond abrasive grains with a maximum diameter of 70 to 80 μm at least toward the cutting start point of the grindstone during cutting. Although any diameter can be used, it is preferably 30 μm or less. However, even when diamond abrasive grains with a diameter of 70 μm are used, in the case of the present invention, the diamond abrasive grains exert a chemical bonding force with the binder, so the diamond abrasive grains are compared to the conventional nickel electrodeposition method. It is more strongly supported by the sintered metal layer. Therefore, until the diamond abrasive grains lose cutting power due to wear or breakage, the abrasive grains have cutting power almost permanently and exhibit excellent cutting power over a long period of time. From this point of view, it can be said that this is a sufficient improvement over the conventional internal circumferential metal bond cutting grindstone. Conventionally, diamond abrasive grains were simply embedded in an electrodeposited layer of nickel, so diamond abrasive grains fell off relatively easily.

When a semiconductor single crystal rod, for example a silicon single crystal rod, is cut, the cutting chips are silicon and are easily pulverized.
This adheres and hardens on the inner peripheral blade surface, causing clogging and reducing cutting ability. However, since the diamond abrasive grains of the present invention's whetstone retain cutting power for a long time, they can be removed by other hard and brittle methods in the normal way. Cutting the material, for example alumina porcelain, allows easy dressing.

Since the diamond abrasive grains of the inner circumferential metal bond cutting wheel of the present invention do not easily fall off, there is no need in principle to remove the back surface portion by dressing the metal bond layer in order to expose new diamond abrasive grains.

However, the tips of diamond abrasive grains are subject to some wear, so
It is necessary to slightly remove the surface portion of the metal bond layer to increase the exposed tips of the diamond abrasive grains. This is natural from the theory of microfracture and scratching of hard and brittle materials.

If the cutting ability of the grindstone is reduced, the cutting edge will bend when cutting the semiconductor material, causing the cutting tool to be deviated from the flat plate and deformed. This deformation takes on various shapes such as a saddle shape and a saucer shape, and these are collectively called a sled. In order to immediately obtain mirror-finished semiconductor single crystal wafers with high dimensional accuracy, it is necessary to produce thin pieces with no warpage or with small warpage during the cutting step.

If the diamond abrasive grains are large, processing strains that are abnormally deep, for example, reaching 70 to 80 μm, will partially occur on the cut surface of the semiconductor single crystal substrate. -There is a lot of processing distortion in boat fishing, and the average depth is 172mm, which is the diameter of the diamond abrasive grain used.
It extends to. The degree of such processing distortion depends on the arrangement and exposure of the diamond abrasive grains on the cutting edge of the whetstone, the shape of the tip, mechanical vibration of the cutting edge, etc.

As a result of various experiments, the inventor found that 3 types of diamond abrasive grains were used.
It has been found that further improved results can be obtained by setting the thickness to 0 μm to 50 μm. As the diameter of diamond abrasive grains becomes smaller, the cutting force becomes smaller and becomes impractical. This is similar to a state where the cutting edge is clogged.
If the cutting speed in the diametrical direction of the semiconductor single crystal rod is increased in this state, warpage occurs in the cut thin section. A grindstone using diamond abrasive grains with a diameter of 5 μm and an alloy with a thickness of 150 μm enables cutting at a rate of about 10 mm per minute under normal working conditions.

If the diameter of the diamond abrasive grains is about 30 μm, no clogging will occur, and the surface processing distortion of the semiconductor substrate after cutting will be 10 to 15 μm.A particularly big improvement is that there will be no abnormal processing distortion. It is what happens. The reason for this is that the semiconductor single-crystal rod has a cutting ability that does not warp even when the cutting speed is as high as 50 mm/min/min, and the exposed abrasive grains on the surface of the inner cutting edge of the diamond grinding wheel are This is thought to be due to the fact that the protruding individual diamond abrasive grains do not cause abnormal pressure at the part where the semiconductor single crystal rod is being cut.

In the present invention, as a result of experiments, it has been found that the most preferable mixing ratio of diamond abrasive grains and metal binder is about 0.8 to 2:10 by weight. When the number of diamond abrasive grains increases, the diamond abrasive grains become more noticeable, and when the number of diamond abrasive grains decreases, the cutting ability decreases. However, within the above range of ratios, no significant difference in cutting ability is observed.

Iron powder is used as the binder in the present invention, and powdered cast iron and reduced iron powder generated during cutting or grinding of cast iron are usually used as the iron powder. The reduced iron used is, for example, one obtained by reducing iron oxide or thermally decomposing iron carbonyl obtained by heating in -carbon oxide at a low temperature. In the latter case, iron powder with a particle size of 1 μm or less can be easily obtained.

The particle size of the iron powder is preferably about 1710 times the particle size of the diamond abrasive grains. This is because if the grain size is the same, the porosity will be close to 50% even if it is packed closest, so in order to reduce this porosity, the grain size must be 1% of the grain size of diamond abrasive grains.
90% or more when iron powder of about 10% is added for filling.
This is because close packing of the two is possible. If we consider it microscopically, diamond abrasive grains are densely surrounded by iron powder, and there are no voids at least close in size to the diamond abrasive grains. The iron powder may have a particle size distribution, with small diameter particles filling the gaps between large diameter particles.

When a mixture of such a binder and diamond abrasive grains is pressure-formed, for example, in the state shown in FIG. 1A and FIG. Forms a chemical bond through iron contact. That is, unlike conventional nickel electrodeposition, in which diamond abrasive grains are simply embedded in a sintered metal layer, in the case of the original diamond abrasive grains, they do not fall off even though they would naturally fall off in the conventional case. In the case of conventional nickel electrodeposition, for example, in the case of FIG. 2A, the nickel does not come off, but in the case of FIG. 2B, the degree of shedding increases. However, in the case of the present invention,
Since the binder chemically fixes the diamond abrasive grains, the diamond abrasive grains do not fall off even in the case shown in FIG. 2B. Small particles with a large surface area per unit volume have a high surface free energy, so sintering takes place at relatively low temperatures. In the present invention, sintering progresses sufficiently at temperatures below 1,000°C.

When silicon powder is added to iron powder as a binder, the adhesion of diamond abrasive grains is further increased. This is because silicon powder forms a metal compound with iron powder and diamond abrasive grains. Silicon forms SiC with diamond,
A 5i4e compound is formed with iron. Since the melting point of the compound of Sl and Pe is lower than the respective melting points, it is thought that this increases the adhesion of the metal sintered layer and the diamond abrasive grains.

Traditionally, the sintering method was not suitable for making thin-layered grinding wheels.
It was said that a thickness of about 1 mm was the limit. However, by isostatic press molding using a special mold, for example, 1,000
If heated at 0° C. for about 1 hour, a sintered layer having almost the strength of iron itself, even if it is a thin layer, can be formed. However, this method does not allow precise shaping of the grindstone, so after sintering is completed, it is further processed into an arbitrary shape by electropolishing.

Isostatic press molding is characterized by being able to pressurize the molded product uniformly and having no compression unevenness.

Molding is carried out by transmitting fluid pressure of approximately 2,000 kg/cm2 through the rubber membrane. The rubber membrane deforms according to the shape of the molded object.

[Example] The present invention will be explained in detail below.

To summarize, the inner circumferential metal bond cutting wheel is No. 1A,
As shown in Figure 18, stainless steel, such as 5tlS30
1 or 5 IIS304's annular base metal 10 is made of diamond abrasive grains 12, cast iron powder, and/or pure iron powder on a limited portion of the upper and lower surfaces of the inner peripheral end and the vicinity thereof, for example, the inner peripheral portion with a width of 3 to 5 mm. It is manufactured by press-molding a mixture with the binder 16, sintering it, and then removing unnecessary sintered iron powder layers by an appropriate method, such as electrolytic polishing, and finishing it to the desired dimensional accuracy. .

To be more specific, as shown in FIG. 1A, a base metal 10 is placed in a mold 18.
is fixed, and diamond abrasive grains 1 are placed near the inner peripheral edge of the base metal 10.
A mixed powder of 2 and binder 16 is filled, and a rubber mold 2 is placed on top of this.
0, put a press plate 22 on its peripheral edge, press the rubber mold 20 against the mold 18 via the press plate 22 with a fastener 24, and seal it so that the pressurized liquid does not enter inside the rubber mold 2°. do. Ultrasonic vibrations are then applied to the mold while static pressure is applied to the whole in a compressed liquid such as glycerin, lubricating oil, or mopil oil. The press forming is performed in two steps in order to perform press forming on both surfaces of the inner peripheral side of the base metal 10. As shown in FIG. 1B, the mold used in the second step is a mold in which a recess 18a for accommodating the already molded part is formed. Other points are the same as the first step.

When molded in this manner, the molded body can be sintered in the sintering furnace as it is without damaging the molded body as long as a strong impact is not applied. For example, the firing temperature is 1,000
℃, the base metal 10 itself may deform depending on how it is held, so it is better to sinter it by placing it on a suitable heat-resistant stand. After sintering, the shape is irregular, so electrolytic polishing is performed next.

Since the binder 16 is made of iron powder as a base material, the electrolyte is, for example, 1
Using a lacI2 aqueous solution, a DC voltage is applied using the grindstone as an anode. As a result, Fe becomes iron hydroxide and dissolves. When the metal bond iron melts, the unnecessary diamond grinding wheel will also fall off. In electrolytic polishing, the cutting edge can be processed into any shape by adjusting the shape of the electrode. In order to prevent the base metal 10 from being electrolytically polished at the same time, the exposed portion of the base metal 10 is coated with a non-conductive film such as wax.

During sintering, annealing occurs if the material is slowly cooled after being removed from the furnace, so it is important to perform re-quenching. Since the carbon content in the metal bond affects the mechanical properties of the base metal 10, it is preferable to adjust the carbon concentration close to that of the base metal IO.

When cutting a semiconductor single-crystal rod, particularly a silicon single-crystal rod, using the grindstone of the present invention, an alkaline aqueous solution, such as a 10% solution of caustic soda, is used as the cutting fluid.

This cutting fluid dissolves and removes silicon chips adhering to the cutting edge of the internal metal bond cutting wheel, and at the same time gradually dissolves the iron powder of the metal bond, exposes the diamond abrasive grains 12, and automatically removes the silicon chips. Dressing can also be done.

If silicon is included in the metal bond, this silicon will also be dissolved by the alkali, facilitating automatic chemical dressing.

The tip of the grindstone generates a suitable amount of heat as it cuts the silicon single crystal, and this thermal energy accelerates the above chemical reaction.

Next, the present invention will be explained in detail.

(1) Test example 1 Diamond abrasive grains 12 with a particle size of 10 to 15 μm and particle size 1
Iron powder of μm and silicon powder of 1 pm in particle size are
: 10 : 0.05 weight ratio, this was placed on the inner periphery of a base metal 10 made of 5II3301 with an outer diameter of 690 mm, an inner diameter of 240 mm, and a thickness of 150 μm, and was isostatically press-molded to 1,800 μm. ni9/c+n'
It was pressurized and preformed, sintered in a hydrogen stream at 1000°C for 1 hour, and electrolytically polished.

Using such an inner circumferential metal bond cutting wheel, a diameter of 100
When a mm-thick silicon single crystal rod was cut into thin pieces, 1,
Even after cutting 000 sheets continuously, the warpage of the silicone flakes was 5.
It was less than μm.

Moreover, when one sample was sampled every 100 sheets from among these 1,000 sheets and the processing strain was measured, the maximum processing strain of each thin piece was 5 μm or less.

In order to compare this with the prior art, a similar test was conducted using a commercially available internal nickel bond cutting wheel with the same specifications, and the warpage exceeded 30 μm after cutting 500 sheets. In addition, an abnormally deep machining groove with a maximum machining strain of 50 μm was discovered in a part of the first to fourth thin slices among the five samples.

(2) Test Example 2 Using the internal metal bond cutting wheel of Test Example 1 above, a silicon single crystal rod was cut into thin slices by using a weak alkaline aqueous solution containing caustic soda as the cutting fluid and by using pure water. The occurrence of warping was compared by cutting. Warpage is 10μm
The number of sheets that could be continuously cut in excess of 200 mm was 1.200 sheets when this weakly alkaline aqueous solution was used, whereas it was about aOO sheets when pure water was used.

(3) Test Example 3 Using the internal metal bond cutting wheel of Test Example 1 above, using a slightly alkaline surfactant aqueous solution as the cutting fluid,
When the silicon single crystal was cut into thin pieces while applying an electric field between the grindstone and the silicon single crystal rod, the resistance during cutting was reduced, and when we investigated the occurrence of warpage, we found that the warpage exceeded 10 ttm continuously. The target number of sheets to be cut was approximately 500. In order to prevent the electric field action from reaching the base metal 10, before cutting, the surface of the base metal 10 from the outer end of the abrasive grain layer 12 to the outer end of the base metal 10 is coated with Teflon (registered trademark) as an insulating material. It was coated with resin.

On the other hand, when a test was conducted using a commercially available internal nickel bond cutting grindstone with the same specifications, the warpage exceeded 30 μm after cutting approximately 600 pieces.

[Effects of the Invention] As explained above, by using the internal metal bond cutting grindstone according to the present invention, it is possible to reduce clogging and deformation wear of the inner peripheral blade due to cutting of semiconductor single crystal rods, etc. By reducing the depth of the abnormal processing strain layer or the average processing strain layer on the surface layer of the wafer etc. after cutting with a blade, high precision, high quality mirror surface semiconductor single crystal substrates etc. can be manufactured efficiently and at low cost. It has the excellent effect of being able to be produced using

[Brief explanation of the drawing]

Figures 1A and 1B are cross-sectional views of essential parts showing a method for manufacturing an internal metal bond cutting wheel according to an embodiment of the present invention, and Figures 2A and 2B are diagrams showing how diamond abrasive grains are separated from the binder by shape. FIG. 3, which is a diagram showing the difficulty of detachment, is a cross-sectional view of a main part showing the structure of a conventional inner circumferential type metal bond cutting grindstone. In the figure, 10 is an alloy 12 is a diamond abrasive grain 14, 16 is a binder 18 is a mold 20 is a rubber mold 22, a push plate 24 is a fastener

Claims (1)

[Claims] 1) On the inner circumferential end surface of the annular metal substrate and both surfaces in the vicinity thereof,
An internal metal bond cutting grindstone in which an inner cutting edge is formed by fixing a bonding agent mixed with super abrasive grains, wherein the bonding agent is mainly composed of iron powder. Whetstone. 2) The internal metal bond cutting wheel according to claim 1, wherein the superabrasive grains are diamond abrasive grains or cubic boron nitride abrasive grains with a particle size in the range of 5 to 60 μm. 3) The particle size of the iron powder is approximately 1/1 of the particle size of the superabrasive grains.
The internal metal bond cutting grindstone according to claim 1 or 2, characterized in that the internal diameter metal bond cutting grindstone is 0 or less. 4) The internal metal bond cutting grindstone according to claim 1, 2 or 3, wherein the binder is a mixture of the iron powder and silicon powder. 5) A mixture of super abrasive grains and a binder is isostatically pressed together with a circular metal substrate, sintered in an inert or reducing atmosphere, and the cutting edge is further finished to the specified dimensions by electrolysis. A method for manufacturing an internal metal bond cutting wheel according to claim 1. 6) A cutting method for obtaining a semiconductor single crystal flake by cutting a semiconductor single crystal rod substantially perpendicularly to its axial direction with an internal metal bond cutting wheel, using the internal metal bond cutting wheel according to claim 1. A cutting method characterized in that an alkaline grinding fluid is spouted under pressure toward at least the cutting start point of the grindstone during cutting.