JPH08217597A - Method for grinding diamond and device therefor - Google Patents

Abstract

PURPOSE: To efficiently work diamond with high precision by rubbing the surface of a diamond wafer with a grinding disk contg. diamond abrasive grain to generate heat, simultaneously spraying a substance causing a thermochemical reaction with the diamond and lowering the hardness by the reaction. CONSTITUTION: A diamond wafer is fixed at the center of a discoid holder and pressed on a rotating grinding disk, the relative speed of the contact point between the disk and the wafer surface is controlled to a high speed of 5-15m/s, the substrate surface is kept at 200-800 deg.C, a substance (e.g. iron) entering into solid soln. with a hard substance (diamond) is sprayed on the disk to bring about a chemical reaction, hence the hardness of the diamond is lowered, and the diamond is ground. The rough oblique drawing of the grinder is shown in the figure. A pressure at 0-30000N/m<2> is exerted on the rotating shaft 4 of a load cell 5. The diamond wafer is pressed on a grinding disk 1 by the normal load. The powder (liq.) of a reacting substance diffusing into the hard substance and subjected to a chemical reaction is sprayed from a spraying device 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing method and a polishing apparatus for polishing the surface of a hard material of a hard material wafer which can be used in the fields of electronics and optics. In particular, it relates to a method and apparatus for polishing the coated surface of a composite wafer having a substrate coated with diamond by a vapor phase synthesis method. The substrate is Si, Mo or the like.

[0002]

BACKGROUND OF THE INVENTION Diamond is the hardest material available today. There is no harder material than this. Since there is no harder material than that, in order to mechanically polish diamond, diamond itself is used as an abrasive. Polish diamond with diamond.
This is called co-sharpening.

The polishing method includes a method using free abrasive grains and a method using fixed abrasive grains. A skiff polishing method is known as a method using free abrasive grains. This uses an iron-based polishing machine and loose diamond grains. While pressing the diamond plate fixed to the holder against the polishing plate and causing a polishing liquid containing diamond abrasive grains to flow on the polishing plate surface, the polishing plate is revolved,
The holder is rotated and the diamond surface is polished by the action of loose diamond abrasive grains. This has the advantage that it hits the object softly and does not destroy it. However, since loose abrasive grains are used, the loss of diamond grains is large. The polishing rate is slow and the finished surface accuracy is not good.

The method of polishing with fixed abrasive grains is to rub a diamond plate with a polishing plate having diamond abrasive grains fixed thereto. There are several types of diamond whetstones depending on the means of fixing the diamond. These are resin bond grindstones, metal bond grindstones, electrodeposition grindstones, and the like. A resin bond grindstone is one in which diamond abrasive grains are fixed with a resin such as phenol resin or polyimide resin.

Bronze, cobalt, tungsten, iron,
A metal bond grindstone is fixed with a metal such as nickel. An electrodeposition grindstone is obtained by fixing diamond abrasive grains with a plating film of iron, nickel, or the like. Since resin-bonded grindstones, metal-bonded grindstones, and electrodeposited grindstones are used with diamond grains fixed, the grains do not flow away. This is extremely advantageous because there is no loss of expensive diamond abrasive grains. In the method using fixed abrasive grains, the diamond plate to be polished is attached to the holder, pressed against a rotating (revolving) grindstone (polishing plate, polishing platen), the holder itself is also rotated, and the diamond surface is moved by physical action. Scrape away.

These polishing methods use diamond plates and films to
It is a method in which the diamond surface is rubbed to physically scrape the diamond surface. All of these methods require a high load on the polished surface because they are ground by physical means. This is because it is necessary to forcibly grind a hard diamond surface by high pressure with diamond abrasive grains having the same hardness. Needless to say, the diamond abrasive grains and the sample diamond are worn out by the high load. If high pressure is not applied, the specimens cannot be scraped at all just by slipping each other.

Special methods for polishing without applying a high load have also been proposed. For example, JP-A-2-26900 uses a smooth metal disk without using diamond abrasive grains. In this method, diamond is brought into contact with a smooth metal disk heated in an oxygen atmosphere to chemically polish the diamond. Since this polishes diamond by the action of heat and oxygen, it can be called a thermochemical polishing method. However, in such a thermochemical method, the processing characteristics strongly depend on the surrounding atmosphere and temperature. There is a drawback that the apparatus becomes extremely expensive in order to perform the processing favorably.

[0008]

Heretofore, diamond has been used as an abrasive or a tool. However, diamond has a wide band gap, is highly resistant to heat and has high thermal conductivity, and becomes a semiconductor by adding impurities. There are strong expectations that diamond will be used in the electronics field due to these advantages. For diamond films to be used in the electronics field, they must be able to be processed by existing wafer processes. For example, it is desired that a technique such as photolithography can be applied for fine processing.

Wafer processes have advanced to a high degree for Si wafers. Rather than searching for a unique diamond method for diamond, Si
It is most desirable to be able to transfer the wafer process developed in 1. to diamond as it is. For this purpose, the diamond must have a large area and be flat.

Diamond can be artificially produced by a high pressure synthesis method or a vapor phase synthesis method. The former is to synthesize bulk diamond crystals by high pressure and high temperature. Large crystals cannot be made because high pressure needs to be applied. Therefore, a diamond wafer that is entirely diamond like the Si wafer cannot be made. Diamond wafers with the same meaning as Si wafers will not be able to be manufactured in the future.

In the vapor phase synthesis method, hydrogen gas and hydrocarbon gas are introduced onto a suitable heated substrate to cause a vapor phase reaction to grow a diamond thin film on the substrate.
For example, plasma CVD method, hot filament CVD method,
The diamond thin film can be synthesized by using a microwave plasma CVD method, an arc plasma jet CVD method, or the like. These vapor phase synthesis methods can produce relatively large area membranes. If you take time, you can make a fairly thick film. Therefore, it is conceivable to use a Si wafer or a diamond thin film formed on another suitable material as a substantial diamond wafer.

[0012] In fact, even when a device is made from a Si wafer, only a part of the upper layer of the wafer is used. The lower layer of the wafer serves as a pedestal and is not actively used. Therefore, even in the case of diamond, only the upper layer needs to be diamond. A very thin diamond obtained by vapor phase synthesis of diamond should be able to be used as a diamond wafer. The whole need not be diamond. Even if Si is coated with diamond, its electrical properties can be utilized as diamond. Therefore, a composite (substrate + thin film) in which a thin diamond thin film is attached on a non-diamond (Si, Mo, Ni, etc.) substrate is hereinafter referred to as a diamond wafer.

Even if a diamond wafer is made, a device cannot be made as it is. This is because the entire wafer is warped and the surface is uneven. It cannot be put on the wafer process as it is. It is necessary to polish the diamond surface in order to remove the surface irregularities and make the surface flat and smooth. However, diamond is the hardest material that is hard to polish among existing materials. As mentioned earlier, there is no harder material than diamond,
Co-cut the diamond surface with diamond abrasive grains. At this time, it is necessary to apply a high pressure to the polishing surface.

Therefore, the diamond wafer must be able to withstand a high surface pressure. However, the diamond wafer described above is merely a Si substrate covered with a diamond thin film, for example. When a high load is applied for polishing, this pressure is applied to the substrate. However, Si, which is the substrate, is a brittle material. It cannot withstand high load during polishing. If the diameter of the Si wafer becomes larger and thinner, it cannot withstand the high surface pressure during polishing and will crack. The same applies when a material other than Si is used as the substrate. It is cracked or chipped due to high pressure during polishing. When polishing composite diamond wafers, it is necessary to prevent the wafers from cracking, chipping or breaking under high loads.

A first object of the present invention is to provide a method for mirror-polishing a diamond surface of a composite diamond wafer in which a soft substrate is coated with diamond without damage. It is a second object of the present invention to provide a method for efficiently polishing a hard film of a composite wafer. It is a third object of the present invention to provide a method for polishing a diamond wafer at low cost. A fourth object of the present invention is to provide a method capable of uniformly and smoothly polishing a diamond wafer. It is a fifth object of the present invention to provide an apparatus for polishing a fragile diamond wafer having a diamond coating formed on a substrate without damage. It is a sixth object of the present invention to provide an apparatus capable of smoothly polishing a composite diamond wafer. It is a seventh object of the present invention to provide an apparatus capable of polishing a composite diamond wafer having a hard coating with high efficiency.

[0016]

The present inventor has earnestly studied a method of uniformly and efficiently mirror-polishing a diamond film of a composite wafer having a substrate coated with diamond without damaging the wafer. The following method has been found in which powder of a substance that reacts with diamond is added to a polishing plate and heated by friction to cause a chemical reaction to perform polishing.

In the polishing method of the present invention, a diamond wafer is fixed to the center of a disk-shaped holder and pressed against a rotating polishing disk, and the relative speed of the contact point between the polishing disk and the wafer surface is set to 5%.
-15m / s high speed and the substrate surface temperature is 200 ℃
The temperature is kept at ˜800 ° C., and a substance that forms a solid solution with a hard substance (diamond) is sprayed on the polishing plate to cause a chemical reaction to lower the hardness of diamond and perform polishing.

As described above, the polishing method of the present invention is intended to polish a hard diamond film by utilizing not only physical action but also chemical action. The reaction (spray) substance diffuses inside the diamond and chemically reacts with the diamond. This reduces the hardness of diamond. As it becomes softer, it can be polished by lower pressure. This is a very important point for the present invention. The hardness reduction amount is proportional to the diffusion amount of the sprayed substance. Here, the substance to be sprayed for causing a chemical reaction is simply referred to as a reactive substance or a reactive agent.

As the reaction material, materials such as iron (Fe), nickel (Ni), manganese (Mn), cerium (Ce), lanthanum (La) can be used. Both are materials that chemically react with diamond. These materials are made into powders and sprayed onto the polishing disk regularly or at any time. It is desirable that the reactant powder always exists uniformly without escaping from the polishing plate. It is necessary to properly determine the distribution and timing of the atomizer. Further, it is preferable to uniformly form recesses for retaining the powder on the surface of the polishing plate.

The reactant reacts with the diamond to form a compound that substantially reduces the hardness of the diamond. For this to happen, the reactants must diffuse efficiently inside the diamond. The diffusion rate of the above-mentioned reactant into the diamond largely depends on the temperature near the contact surface between the diamond and the polishing plate. The diffusion rate is higher at higher temperatures. Means for heating to raise the temperature are required. It is conceivable to provide a heater below the polishing table to heat the polishing table.

However, other than that, heat is generated due to friction between the polishing plate and the diamond film. It is possible to effectively utilize the frictional heat during polishing to promote the diffusion of the reaction material.
The magnitude of frictional heat is determined by the product of pressure and relative velocity. Depending on the area of the wafer, the force that pushes the wafer is 2
It is of the order of kgf to 20 kgf. This force has an upper limit due to the physical strength of the substrate. Often the substrate is Si
Since it is a brittle material like that, if too much pressure is applied, the substrate will crack. It may not be possible to raise it above 10 kgf.

Therefore, consider increasing the relative speed.
If the relative speed is high, the frictional heat will be generated even if the pressure is low. A preferable relative speed is 5 m / s to 20 m / s. The best is about 10 m / s to 17 m / s. When the dynamic friction coefficient between the diamond thin film and the polishing plate is μ, and the pressing force is 10 kgf and the speed is 15 m / s, the friction heat generation amount per unit time is 350 μcal / s.

A preferable polishing platen temperature is 200 ° C. to 8 ° C.
It is 00 ° C. When the polishing disk and the wafer are rotated relative to each other at a relative speed within the above range while applying an appropriate pressure, 20
It becomes 0 to 800 ° C. This can facilitate diffusion of the reactant into the diamond. Contact interface temperature T1
Is measured by a temperature sensor embedded in the surface of the polishing plate. The target temperature Tm of the polishing interface is determined from the temperature T1 and the polishing conditions. When the target temperature is given, the weight W and the relative speed S for realizing this are determined. The polishing apparatus is adjusted to meet such conditions. Friction heat alone may not be sufficient for heating. In this case, heat with a heater to raise the temperature of the polishing plate.

The essence of the present invention is to reduce the hardness and promote the progress of polishing by diffusing the reactive substance into the hard substance. The diamond after polishing should not contain a diffusion layer. All need to be scraped off. Therefore, as the polishing plate, one having diamond abrasive grains fixed to the surface is used. The diamond abrasive grains are fixed to the polishing plate via a connecting material such as resin bond, metal bond, or electrodeposition.

[0025]

1 is a schematic perspective view of a polishing apparatus for carrying out the polishing method of the present invention. The polishing disk 1 is a disk-shaped grindstone having a large number of diamond particles fixed on its surface. Any means for fixing the abrasive grains such as resin bond, metal bond, and electrodeposition may be used. The holder 3 is a circular flat disk. The object to be polished 2 is attached to the lower surface. In other words, diamond wafer
Is attached with the substrate side in contact with the holder surface. A cushioning material may be sandwiched between them.

The holder 3 is supported by a rotating shaft 4 (shaft). The rotating shaft 4 is rotatably supported by a bearing above. The load cell 5 applies a predetermined pressure to the rotating shaft 4. The motor 7 applies a rotational force to the rotating shaft 4 by the shaft 14, the pulley 15, the belt 8 and the pulley 16. The rotating shaft 4 causes the holder 3 to rotate. Here, the load cell 5 can apply a pressure of 0 to 3 × 10 ⁴ N / m ² . The diamond wafer is pressed against the polishing disc by vertical load. The holder-3 rotates at a fixed position and the polishing table 1 revolves largely.

A sprayer 6 is provided on the side of the polishing disc 1. A powder of a reactive substance that diffuses into a hard substance and chemically reacts, or a liquid containing the powder is placed in the sprayer 6. During the polishing, regularly or as needed, on the polishing disc, powder,
Spray liquid. The sprayed reactant particles temporarily stay on the surface of the polishing plate. The polishing machine 1 revolves around the sun, and the holder rotates on its axis. Since the pressure is applied, the hard material film is strongly pressed onto the polishing plate. Gives a high relative speed,
Large frictional heat is generated at the contact surface. The material to be polished is heated by the friction heat. The diamond surface becomes hot.

The sprayed reactants adhere to the diamond surface. The temperature and pressure cause the reactant to start diffusing into the hard material (diamond). The rate of diffusion and the amount of diffusion are determined by the material of the material to be polished, the reactant, and the temperature of the material to be polished. Although the abrasive grains of the polishing plate are hard substances, the same material as the material to be polished accelerates the deterioration of the polishing plate. In order to avoid deterioration, the material of the abrasive grains of the polishing machine should be properly selected.

As shown in FIGS. 2 and 3, the polishing disk 1 has a large number of circumferential grooves 12 in the circumferential direction and a large number of radial grooves 1 in the radial direction.
1 is worn. The circumferential groove 12 has a width of 0.5 mm to 1 m.
m is a shallow groove having a depth of 0.1 mm to 0.5 mm. This prevents the powder or solution sprayed on the polishing disc from being removed from the polishing disc by the passage of the object to be polished. When the substance that reacts with the hard substance is supplied to the polishing plate in the form of powder or solution, the substance stays in the circumferential groove 12 and cannot be easily pushed away. If the circumferential groove 12 were not provided, the reaction material would not exist in the portion on the polishing plate through which the object to be polished passes. Since the circumferential groove 12 can capture the powder and the solution, the reactant can be always present even in the portion where the object to be polished passes.

The radial groove 11 has a width of 1 mm to 2 mm,
It is a larger and deeper groove having a depth of 1 mm to 2 mm. The radial groove 11 prevents the polishing plate from being clogged with residual powder, polishing dust, or the like that has been sprayed for a while and then passed. That is, the circumferential groove has a function of allowing the powder to stay for a long time, and the radial groove has a function of promptly removing unnecessary powder and dust. The radial groove does not necessarily have to be linear. It may have a spiral shape or a screw shape. Any shape may be used as long as it connects the central portion and the outer peripheral portion.

Due to the amount of powder supplied, the effect of the circumferential groove, and the effect of the radial groove, a certain amount of reactant is always present on the polishing plate. However, the polishing powder gradually becomes dirty due to the residual powder and dust. When the buildup of polishing debris and residual powder on the polishing plate becomes excessive, water or a cleaning liquid is caused to flow on the polishing plate. As a result, residual powder and polishing dust are removed, and the polishing platen is cleaned. After cleaning, spray the powder or solution again from the sprayer 6,
Restart polishing.

The main motor 7 rotates the holder. The main motor 7 can change its rotation speed by an inverter. The motor 7 is a high speed rotation type motor.
It is The motor output is decelerated by the deceleration mechanism including the belt 8 and the pulley to rotate the holder. The relative speed at the contact point between the object to be polished and the polishing plate is 5 m / s to 2
The motor rotation speed can be adjusted to be 0 m / s.

The present invention causes a chemical reaction by frictional heat generated between the object to be polished and the polishing plate. The frictional heat generated in a unit time is given by the product of relative velocity and frictional resistance. If the force applied through the load cell is large, the frictional resistance is large and the heat generation is large. However, it may not be possible to apply a large pressure to the object to be polished. The object to be polished may be a composite of a hard substance and a brittle material. In this case, the object to be polished cannot be pressed strongly against the polishing plate. In this case, a high relative speed must be given. That is, it is necessary to rotate the polishing plate at high speed. Thus, the present invention provides relatively high speed relative rotation.

Since the object to be polished is scraped off by utilizing the chemical reaction, the temperature is an important factor. The surface temperature of the polishing board 1 is monitored by a radiation thermometer 9. An electric heating coil is installed below the polishing plate 1. The temperature of the polishing plate can be adjusted by heating the polishing plate with an electric heating coil (heater). Here, the temperature of the polishing board is 200 ° C.
It can be adjusted in the range of up to 800 ° C.

However, not all of the temperatures required to diffuse the atomized material are supplied by the electrothermal coil. Most of the heat is supplied by frictional heat generated between the object to be polished and the polishing plate. First, determine the temperature at which the sprayed substance can diffuse into the object to be polished, measure the temperature of the polishing plate increased by frictional heat with a radiation thermometer, and determine the heat required to give the temperature of these differences. Supplied from the heater. If the polishing plate temperature is lower than the set temperature, the electric heating coil power is increased, and conversely, if the polishing plate temperature is higher than the set temperature, the electric heating coil power is decreased.

[0036]

Example A hard material wafer manufactured under the following conditions:
Were polished by the method of the present invention. [Method of Manufacturing Hard Film] As the substrate, a mirror-polished (100) single crystal Si wafer having a diameter of 2 inches (50 mm) and a thickness of 1 mm was used. This Si wafer was scratched with diamond powder having an average particle size of 0.5 μm to 1 μm. This is to increase the nucleus generation density of diamond.

A diamond film was formed on the Si wafer by the filament CVD method. In the filament CVD method, a base material is placed on a support in a reaction vessel, hydrogen gas containing hydrocarbons is introduced into the vessel, the base material is heated by a filament to decompose the raw material gas, and a gas phase reaction is performed. And a reaction product is deposited on the substrate. As the filaments, ten tungsten (W) wires having a diameter of 0.3 mm stretched in parallel at 7 mm intervals were used. There is a cooling mechanism in the support base. Even if the filament temperature is kept constant, the temperature of the base material can be freely adjusted by the cooling mechanism.
The conditions for synthesizing the diamond film are as follows.

Filament temperature 2100 ° C. Raw material gas Hydrogen (H ₂ ) gas 500 sccm Methane (CH ₄ ) gas 5 sccm Pressure 50 Torr (6600 Pa) Base material temperature 850 ° C. Diamond film thickness 50 μm

The temperature of the substrate can be controlled by a cooling mechanism. Here, it is set to 850 ° C. Since the film thickness increases in proportion to time, the film thickness can be controlled by time. Here, it is set to 50 μm. The diamond wafer as the sample of the present invention can also be manufactured by a DC plasma CVD method, a high frequency plasma CVD method, a microwave plasma CVD method, an arc plasma jet CVD method, or the like. In addition to methane, ethane, propane, acetylene, halogenated hydrocarbon and the like can be used as the hydrocarbon raw material.

Diamond film thickness is 10 μm to 300 μm
It can be set to In addition to Si, Mo can be used for the substrate. Since the present invention is a method for polishing a composite film composed of a substrate and a diamond thin film, it can be applied to a hard material wafer manufactured by any manufacturing method. The sample thus manufactured was polished by the following four processing methods.

(1) Processing Condition 1 (Changing Rotation Speed of Polishing Disk) The sample (Si substrate + thin film) is attached to a disk-shaped base material holder. A stainless holder having a diameter of 100 mm and a thickness of 20 mm was used to support the sample. The sample is not fixed directly to the holder. Sample diameter is φ6
Stick it on the natural rubber of 0 mm and thickness 2 mm with an adhesive,
Natural rubber was further adhered to the lower surface of the holder with an adhesive. The reason for interposing the rubber is that the sample originally has irregularities. Another reason is to prevent the fragile substrate from cracking or chipping due to the cushioning effect of rubber. Examine the difference due to the rotation speed of the polishing machine. The polishing conditions are as follows.

B. Polishing machine # 200, resin bond diamond whetstone with a concentration of 100 b. Polishing plate diameter 300 mm C. Polishing board rotation speed 500 rpm, 1500 rp
m d. Holder-Stainless steel φ100, 20 mmt e. Buffer material Natural rubber φ60, 2mmt f. Holder-rotation speed 40 rpm g. Processing pressure 8 kgf H. Polishing time 10 Hr. No spray powder, iron, manganese, cerium. Atmosphere Argon (Ar)

{After polishing for 10 hours} Under the above conditions, the diamond wafer was polished for 10 hours. Sample with a polishing plate rotation speed of 500 rpm, 1500 rpm
The sample is Calculate the linear velocity in the case of rotation. Wafer radius is 25mm, rotation speed is 40r
Since it is pm, the linear velocity at the outermost periphery is 0.1 m /
s. Calculate the linear velocity in the case of revolution. Since the radius of the polishing plate is 150 mm and the radius of the wafer is 25 mm, the distance D between the center of the wafer and the center of the polishing plate is 90 mm to
It is about 110 mm.

In the case of 500 rpm of the sample, the wafer
The linear velocity V at the center is V = 4.7 m / D when D = 90 mm.
When s, D = 100 mm, V = 5.2 m / s, D = 110
When mm, V = 5.7 m / s. 1500r of sample
In the case of pm, the linear velocity V at the wafer center is D = 90.
mm = V = 14 m / s, D = 100 m / s V = 1
When 5.7 m / s and D = 110 mm, V = 17 m / s. Both the rotation and the revolution act, and the linear velocity varies depending on the distance from the center of the polishing machine. If the rotation and the revolution are in the same direction, the linear velocity may temporarily be the sum of both. In the above example, since the linear velocity due to the rotation is small, the relative linear velocity between the polishing plate and the wafer is almost determined by the revolution of the polishing plate.

In both samples, the diamond film surface was convexly warped by 15 μm. In all the samples, the polishing progresses from the central portion toward the periphery. The progress is shown by the area X of the polishing part with respect to the whole substrate Z.
Expressed by the ratio X / Z of, the revolution speed is 500 rp
The value of m was about 50% under all conditions. That is, 50% of the peripheral portion is unpolished or insufficiently polished. When the revolution speed was 1500 rpm, there was no atomized substance, and when the atomized substance was iron, X / Z was 70%. When manganese is the spray substance, X / Z is 90%, which is more excellent. X / Z is 1 when the atomized substance is cerium
It was 0% and the entire surface was polished.

This is the case where the polishing time is 10 hours.
If the time is longer than this, the polishing rate further increases. On the contrary, if the time is shortened, the polished area is further reduced. Table 1 shows the measurement results of the polishing depth at the center of the wafer for the samples having different rotation speeds and atomized substances.

[0047]

[Table 1]

When the polishing plate is rotated at 500 rpm, the polishing rate hardly changes depending on the sprayed substance. That is, there is almost no special effect due to the spray substance. In the case of 1500 rpm, the polishing rate becomes high in the case of spraying manganese and cerium. This is true for the polishing depth and also for the polishing width described above. In the case of 500 rpm, the relative speed between the wafer and the polishing plate is about 5 m / s. It can be seen that when the relative speed is lower than this, the polishing depth is shallow. At 1500 rpm, the relative speed is about 15 m / s. When manganese is used as the reaction material, the polishing depth increases in proportion to the rotation speed. However, when there is no atomized substance and the atomized substance is iron, the polishing depth does not increase to the extent that it is proportional to the rotation speed. When the atomized substance is cerium, the depth increases more than the ratio of the number of revolutions.

(2) Processing condition 2 (when the type of diamond grindstone is changed) The sample (Si substrate + thin film) is 15 on the diamond film surface.
The one having a warp of μm was used. As in the previous example, the wafer was attached to a stainless steel holder having a diameter of 100 mm and a thickness of 20 mm through a natural rubber. Next, we examined the difference in polishing results depending on the polishing machine. The polishing conditions are as follows.

B. Polishing machine # 200, resin-bonded diamond whetstone with a concentration of 100 # 200 diamond electrodeposition whetstone # 200, metal-bonded diamond whetstone with a concentration of 100 b. Polishing plate diameter 300 mm C. Polishing board rotation speed 1500 rpm

D. Holder-Stainless steel φ100, 20 mmt e. Buffer material Natural rubber φ60, 2mmt f. Holder-rotation speed 40 rpm g. Processing pressure 8 kgf H. Polishing time 5 Hr. No spray powder, iron, manganese, cerium. Atmosphere Argon (Ar)

{After polishing for 5 hours} The diamond wafer was polished for 5 hours under the above conditions. For all the samples, the diamond film surface was convexly warped by 15 μm. In all the samples, the polishing progresses from the central portion toward the periphery. The rotation speed of the polishing machine is 15
It is 00 rpm. At linear velocity, 14m / s-17
m / s. Table 2 shows the measurement results of the polishing depth of the central portion of the substrate depending on the polishing plate.

[0053]

[Table 2]

When there is no atomized substance and iron and manganese, the removal depths of the electrodeposition grindstone and the metal bond grindstone are almost the same. Resin bond wheels have less removal than these two wheels. When using cerium as the atomizing substance, the amount of polishing increases with any grinding stone. In the case of cerium, the amount of polishing by the resin bond grindstone is almost equal to the amount of polishing by the other two grindstones. The surface roughness Ra is an important factor for evaluating the polishing result. The surface roughness Ra (nm) of the polished surface was measured for samples having different grindstones and spray substances. The results are shown in Table 3.

[0055]

[Table 3]

In the case of a metal bond grindstone, the surface roughness is the largest. Surface roughness is low in the case of electrodeposition grindstone and resin bond grindstone. Ra = 10 nm to 20 n for the electrodeposition grindstone and resin bond grindstone in the case of no spray substance, iron and manganese
It is about m. For the purpose of reducing the surface roughness, it is preferable to use the atomized substance or the atomized substance iron. The surface is rough when using cerium as a spray substance. Among them, the case of using a metal bond grindstone is the most remarkable. This is because the polishing plate is deteriorated by spraying cerium. The whetstone that is least deteriorated by cerium is resin bond.

(3) Processing condition 3 (when a non-diamond grindstone is used) A diamond grindstone has been used as a polishing machine up to now, but here, a diamond wafer is ground and polished using a grindstone having no diamond abrasive grains. And the surface roughness were measured.
The material of the polishing plate has been used as a spray substance. No atomized material is used. The polishing conditions are as follows.

B. Polishing machine material Iron (without diamond abrasive) Manganese (without diamond abrasive) Cerium (without diamond abrasive) b. Polishing plate diameter 300 mm C. Polishing board rotation speed 1500 rpm

D. Holder-Stainless steel φ100, 20 mmt e. Holder-rotation speed 40 rpm f. Processing pressure 8 kgf. Polishing time 1 Hr H. No spray powder Atmosphere Vacuum (less than 10 ^-3 Torr)

{After polishing for 1 hour} The diamond wafer was polished for 1 hour under the above conditions. Since the polishing depth (μm) and the surface roughness: Ra (nm) differ depending on the type of polishing plate, these were measured. The results are shown in Table 4.

[0061]

[Table 4]

The surface of each sample is polished to Ra of about 30 nm. It can be seen that polishing hardly progresses because diamond abrasive grains are not used. Particularly, in the case of an iron polishing machine, almost no polishing is possible. In the case of a manganese polisher, it can be polished a little. 1.1 μm in 1 hour for cerium polishing machine
Can be polished to a degree. It is estimated to be about 5 μm after spending 5 hours. It can be seen that this has a surface roughness of 9 nm and is sufficiently smooth. Rather than physically polishing these, the material atoms of the polishing plate penetrate into the diamond thin film by thermal diffusion, and the diamond is removed by a chemical reaction.

(4) Processing condition 4 (when the temperature is changed) As the polishing disk, a polishing disk having no diamond abrasive grains is used. The temperature of the polishing board surface is 300 ℃, 600 ℃, 900 ℃
The effect of temperature was investigated by varying the temperature. Do not spray powder.

B. Polishing machine material Iron (without diamond abrasive) Manganese (without diamond abrasive) Cerium (without diamond abrasive) b. Polishing plate diameter 300 mm C. Polishing machine rotation speed 500 rpm

D. Polishing plate surface temperature 300 ° C, 600 ° C, 900 ° C e. Holder-rotation speed 40 rpm f. Processing pressure 8 kgf. Polishing time 5 Hr H. No spray powder Atmosphere Vacuum (less than 10 ^-3 Torr)

{After polishing for 5 hours} The diamond wafer was polished for 5 hours under the above conditions. Depending on the surface temperature of the polishing plate, the polishing depth (μm) and surface roughness (R
a) is different. Table 5 shows the results of measuring how the polishing depth (μm) varies depending on the polishing plate material and the surface temperature.

[0067]

[Table 5]

When an iron polishing plate is used, 300 ° C., 600
When the temperature is ℃, polishing hardly progresses. When the temperature is raised to 900 ° C., the diamond layer is removed by only about 3 μm. When using a manganese polishing table, 600 ° C, 90
As the temperature rises to 0 ° C., the removal layer of the diamond layer increases to 6 μm to 14 μm. Using a cerium polishing plate, the temperature of 600 ° C. already removes 15 μm. The surface roughness Ra (n
m) was measured and the results are shown in Table 6.

[0069]

[Table 6]

When an iron polishing plate was used, the temperature was 300.
The surface roughness Ra is 100 n at 100 ° C. to 900 ° C.
It was m or more. In the case of a manganese polishing plate, Ra becomes 30 nm or less at 600 ° C. or higher. In the case of a cerium polishing plate, the surface roughness Ra becomes 30 nm or less at 300 ° C. or higher.
When cerium is used, the surface roughness is the smallest at 600 ° C. and Ra = 15 nm.

[0071]

EFFECTS OF THE INVENTION Diamond, which has been extremely difficult to process due to its high hardness, can be efficiently and accurately processed. For efficient polishing, that is, high-speed processing, there are laser processing and electric discharge processing. However, the surface roughness is inferior. In terms of processing accuracy, there is an oxygen etching method. However, this has a slow processing speed. That is, in the diamond processing method, there is no processing method that can achieve both efficiency and accuracy. For the first time, the present invention can provide a diamond processing method excellent in both efficiency and accuracy.

In order to use diamond in the fields of electronics and optics, a flat, smooth and large area diamond wafer is required. The present invention can provide a large area mirror-polished diamond wafer. The processing method of the present invention can dramatically increase the applications of diamond.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a diamond polishing apparatus of the present invention.

FIG. 2 is a plan view showing a groove structure on the surface of a polishing plate used in the present invention.

FIG. 3 is a vertical cross-sectional view taken along the line XX of the polishing disk of FIG.

[Explanation of symbols]

 1 Polishing Board 2 Object to be Polished 3 Holder-4 Shaft 5 Road Cell 6 Sprayer 7 Holder-Motor 8 Belt 9 Radiation Thermometer 11 Radial Groove 12 Circumferential Groove 14 Shaft 15 Pulley 16 Pulley

Claims (11)

[Claims] 1. In order to polish a diamond surface of a diamond wafer having a diamond film formed on a base material, the diamond surface and a polishing plate containing diamond abrasive grains are brought into contact with each other, and the contact points are rubbed against each other. A powder of a substance that generates heat by thermodynamic reaction with diamond or a liquid containing a powder is sprayed onto the polishing plate to react the diamond with the reaction substance to form a compound with diamond to lower the hardness and to polish it with the polishing plate. A diamond polishing method characterized in that the diamond surface is removed by means of. 2. The diamond according to claim 1, wherein at least one kind of substances such as iron, nickel, manganese, cerium, and lanthanum is used as a spray substance to be sprayed as powder or liquid. Polishing method. 3. In order to polish a diamond surface of a diamond wafer having a diamond film formed on a base material, the diamond surface is brought into contact with a polishing plate made of a material that chemically reacts with diamond and rubbed against each other. It is characterized in that heat is generated at the contact point by combining and the diamond and the polishing plate material are thermochemically reacted to form a compound with diamond to lower the hardness and scrape with the polishing plate to remove the diamond surface. Diamond polishing method. 4. The diamond polishing method according to claim 3, wherein at least one of substances such as iron, nickel, manganese, cerium, and lanthanum is used as a material for the polishing plate. 5. The processing atmosphere according to claim 1, wherein the processing atmosphere is filled with at least one gas selected from oxygen, hydrogen, argon and the like, or is a vacuum. Polishing method of diamond. 6. An arbitrary one of each of the polishing plate and the material to be polished
The diamond polishing method according to any one of claims 1 to 5, wherein the relative velocity of the points is 5 m / s to 20 m / s. 7. The temperature of the surface of the material to be polished is heated to a range of 200 ° C. to 800 ° C. by frictional heat with the surface of the polishing plate,
The diamond polishing method according to claim 1, wherein a chemical action is promoted by the heat. 8. The temperature of the polishing plate surface can be continuously adjusted in the range of 200 ° C. to 800 ° C. by a heater provided under the polishing plate and a sensor for detecting the surface temperature of the polishing plate. The diamond polishing method according to claim 1, wherein the diamond polishing method is used. 9. A polishing disk having diamond particles fixed on the surface and rotating around a main axis, a holder that fixes a diamond wafer on the lower surface and rotates around a shaft while being pressed against the polishing disk, and a holder that rotates the holder. -Mo-
, A load cell that can apply a force to the holder in the axial direction and detect the force, a sprayer that sprays a powder of nickel, iron, manganese, cerium, lanthanum, or a liquid containing these powders onto a polishing disk, and a polishing tool. It includes a temperature sensor for measuring the surface temperature of the plate and a heater for heating the polishing plate, and the holder can be applied with an axial force of 2 kgf to 20 kgf.
Relative linear velocity between polishing machine and diamond wafer is 5m / s ~
A diamond polishing apparatus characterized in that a polishing disk can be rotated so as to be 20 m / s. 10. The polishing machine used is an electrodeposition grindstone using diamond abrasive grains, a resin bond grindstone, a metal bond grindstone, or a vitrify bond grindstone.
The diamond polishing apparatus described in 1. 11. A polishing machine having iron, nickel, manganese, cerium or lanthanum on at least its surface and rotating around a main axis, and a holder which rotates around a shaft while a diamond wafer is fixed to the lower surface and pressed against the polishing machine. , A holder motor for rotating the holder, a load cell capable of applying a force to the holder in the axial direction and detecting the force, a temperature sensor for measuring the surface temperature of the polishing plate, and heating the polishing plate. Including a heater, the holder is 2kgf ~ 2
A diamond polishing apparatus characterized in that an axial force of 0 kgf can be applied and the polishing disk can be rotated so that the relative linear velocity between the polishing disk and the diamond wafer becomes 5 m / s to 20 m / s.