JP2019141974A - Double side lapping machine and method for grinding thin fine ceramic using the same - Google Patents

Abstract

To provide a double side lapping machine that can efficiently process even a thin, hard brittle workpiece such as an SiC wafer into a state with low warpage and good flatness and surface roughness, and a method for grinding thin fine ceramic using the lapping machine.SOLUTION: An upper surface plate side grindstone 2 and a lower surface plate side grindstone 3 attached to an upper surface plate and a lower surface plate of a double side lapping machine comprise a vitrified grindstone of a fixed abrasive grindstone in which a hard abrasive with an average particle size of 8 μm-0.1 μm and a soft abrasive with an average particle size of 5 μm-0.1 μm are boned with a binder layer 13, with the porosity: 40%-65% and the binder rate: 5-25%, and the lower surface plate side grindstone 3 is sharper than the upper surface plate side grindstone 2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a double-sided lapping machine employing a fixed abrasive grindstone and a method for grinding thin-walled fine ceramics such as a semiconductor wafer using the same.

Silicon carbide (hereinafter referred to as SiC), silicon nitride (Si ₃ N ₄ ), gallium nitride (GaN), aluminum nitride (AlN), lithium tantalate (LT), zirconia (ZrO ₂ ), alumina (Al ₂ O ₃ ) And fine ceramics such as boron nitride (BN) tend to be frequently used as semiconductors. The following description will be given using SiC as an example.

  SiC is a chemically and thermally stable high-hardness material, and a SiC wafer made of the material is known as one of power semiconductors.

  The SiC wafer is cut into a thickness of 0.7 mm or less from an ingot using an electrodeposited diamond wire saw, and is practically used. However, the thickness, crystal orientation and directionality of SiC, and further processing during cutting Due to the effects of stress and internal stress inherent to the ingot, the flatness (TTV) is poor at the stage of being cut out from the ingot, and a large warp (warp, expressed as SORI in academic societies, etc.) is generated.

  The flatness and warpage are corrected by a method of grinding both surfaces in sequence using a single-side grinding machine or a double-sided simultaneous lapping method using loose abrasive grains.

  However, the processing by the single-sided grinding machine is not only a process for each wafer but also a process of inverting the Si surface and the C surface of the wafer, which is troublesome. In addition to this, it is necessary to prepare a lot of expensive grinding equipment in order to achieve mass production.

  Further, since the processing is performed on each side, a difference occurs in the processing stress on both sides, and a difference also occurs in the surface roughness between the processed surface and the unprocessed surface, so that warping due to the Twiman effect is likely to occur.

  On the other hand, double-sided simultaneous lapping using free abrasive grains can simultaneously process a large number of workpieces (workpieces) on the same surface plate, ensuring parallelism on both sides of the workpiece and reducing warpage. However, the working efficiency is extremely poor compared to grinding using a fixed abrasive wheel.

  In addition, the presence of loose abrasive grains is difficult to be uniform between the upper and lower surface plates of the lapping machine, and the surface roughness on the upper and lower surfaces (Si surface and C surface) of the wafer is different, resulting in warping due to the Twiman effect. May occur.

  Furthermore, lapping processing using loose abrasive grains not only makes the working environment worse, but also makes it difficult to save labor and automate, and involves environmental problems in the treatment of slurry waste liquid.

  For this reason, proposals using a fixed abrasive grindstone for a double-sided lapping machine have been made by the following Patent Documents 1-9.

  Patent Document 1 improves the sharpness of the wrapping wheel by changing the structure of the grindstone and the additive, thereby improving the efficiency and accuracy of the wrapping process.

  In Patent Document 2, a grinding wheel segment is arranged on the inner and outer peripheral portions of a lap surface plate to which diamond pellets are fixed, thereby suppressing uneven wear of the pellets and segments and improving the accuracy of polishing.

  In Patent Document 3, an elongated rectangular bar-shaped abrasive piece obtained by sintering metal powder and diamond powder is fixed to the sliding surfaces of upper and lower surface plates so that a gap is left between the abrasive pieces, thereby suppressing damage to the carrier. It is a thing.

  Patent Document 4 discloses that a rectangular polishing piece obtained by sintering metal powder and diamond powder is concentrically formed on a sliding surface of upper and lower surface plates so that a gap is formed between the polishing pieces. In this case, the carrier is prevented from being damaged and the polishing efficiency is improved by inclining and fixing with respect to the diameter direction.

  Patent Document 5 discloses a method for suppressing carrier damage and polishing efficiency by arranging rod-shaped polishing pieces at intervals on the inner and outer peripheral portions of a lap surface plate in which diamond pellets are fixed concentrically with a substantially uniform interval. It is an improvement.

  Patent Document 6 creates a parallel plane above and below the workpiece by adhering and curing a synthetic resin to the workpiece, and sandwiches it between the upper and lower surface plates of a double-sided lapping machine, and is fixed to the sliding surface of the surface plate. The workpiece warpage is removed by grinding and polishing in the order of the synthetic resin and the workpiece with the polishing body.

  In Patent Document 7, an inorganic porous body is sandwiched between a surface plate of a polishing apparatus and a work plate for grinding, and the thermal expansion of the surface plate and the work plate is caused individually to prevent deformation due to the thermal expansion of the grindstone. Is.

  In Patent Document 8, the surface roughness of the upper and lower surfaces of the workpiece is reduced by making the particle size of the fixed abrasive wheel fixed to the upper surface plate of the double-sided lapping machine smaller than the particle size of the fixed abrasive wheel fixed to the lower surface plate. Are different in one processing step.

  In Patent Document 9, the particle size of the fixed abrasive grindstone fixed to the lower surface plate of the double-sided lapping machine is made larger than the particle size of the fixed abrasive grindstone fixed to the upper surface plate, thereby improving the wafer flatness while increasing the wafer flatness. The machined surface roughness of the lower surface is varied by simultaneous machining.

JP 2003-291070 A JP 2004-243465 A JP 2004-243469 A JP 2009-045690 A JP 2009-274185 A JP 2014-161934 A Japanese Patent Laying-Open No. 2015-104762 JP-A-4-261768 Special table 2015-531318 gazette

  In any of the techniques of Patent Documents 1 to 7, fixed abrasive grains having the same quality are fixed to the upper and lower surface plates of the double-sided lapping machine, and the effect of reducing the warpage of the wafer is not sufficient.

  SiC is extremely hard following diamond, and is extremely difficult to process because it has a crystal orientation and direction.

  In double-sided simultaneous lapping with a fixed abrasive wheel of the same quality, there is an unavoidable difference between the processing conditions of the grinding wheel attached to the upper surface plate of the double-sided lapping machine and the processing conditions of the grinding stone attached to the lower surface plate, and the Twiman effect. The warp caused by the inevitably remains.

  Moreover, the fixed abrasive grindstone used in the lapping machines of Patent Documents 2 to 5 and 7 is intended to increase the amount of grinding fluid and the chip dischargeability. Although it arrange | positions with the clearance gap used as discharge space, in this structure, the abrasive grain which fell from the grindstone is not utilized for grinding. For this reason, the processing efficiency is not fully satisfactory.

  In the fixed abrasive grindstone used in the lapping machine of Patent Document 8, the grain size of the grindstone attached to the lower surface plate is roughened for the purpose of improving the adhesion with the multi-components on the back surface of the workpiece.

  In Patent Document 8, diamond abrasive grains having an average particle diameter of 20 μm are used as abrasive grains for a grindstone attached to an upper surface plate, and diamond abrasive grains having an average particle diameter of 100 μm are provided as abrasive grains for a grindstone attached to a lower surface plate. The roughness of the processed surface in the lapping processing test of the square plate of the silicon nitride sintered body by the double-sided lapping machine using the grindstone is 0.32 μmRa on the back surface and 0.07 μmRa on the surface (difference between the two) 0.25 μm Ra).

  However, when the difference in surface roughness between the front surface and the back surface exceeds 0.2 μmRa, stress balance is lost due to the difference in roughness between the upper and lower surfaces, and warping due to the Twiman effect remains.

  The fixed abrasive grindstone used in the micro-grinding process of Patent Document 9 also processes the grindstone that processes one surface of the wafer and the other surface for the purpose of differentiating the surface roughness of the upper and lower surfaces of the workpiece (wafer). The grindstone has a different particle size.

  However, the fixed abrasive grindstone used in the grinding process of Patent Document 9 has an average particle size of 10 μm to 80 μm of the finer abrasive particles, and an average particle size of the coarser abrasive particles of 80 μm to 200 μm, In this case, it is not possible to ensure the processed surface roughness required for a power semiconductor wafer such as SiC.

  Also in this method, the difference between the processed surface roughnesses on both sides of the wafer is large, and warping due to the Twiman effect remains as in the technique of Patent Document 8.

  The present invention has been made in view of the above prior art, and has high hardness, crystal orientation and direction, and hence the thickness of SiC wafers and the like for which development of mass production processing technology has been delayed. We provide a double-sided lapping machine that can efficiently process thin hard and brittle workpieces with low warpage and excellent flatness and surface roughness, and a method for grinding fine ceramics (such as SiC wafers) using the lapping machine. The challenge is to do.

In order to solve the above problems, in the present invention, there is a fixed abrasive grindstone attached to an upper surface plate and a lower surface plate, and the fixed abrasive grindstone has a hard abrasive particle having an average particle diameter of 8 μm to 0.1 μm. And a soft abrasive grain having an average particle diameter of 5 μm to 0.1 μm mixed at a mass ratio of hard abrasive grains: 50 to 90%: soft abrasive grains: 50 to 10% and containing a low melting point vitrified bond A vitrified grindstone having a porosity of 40% to 65% and a binder ratio of 5 to 25%.
Fixed abrasive grindstone (hereinafter referred to as lower surface plate side grindstone) attached to lower surface plate is fixed abrasive grindstone (hereinafter referred to as upper surface plate side grindstone) whose particle size, hardness or concentration is attached to upper surface plate A double-sided lapping machine that is different and has a sharpness superior to that of the upper surface grinding wheel.

  The lower surface plate side and upper surface plate side whetstone of this double-sided lapping machine are vitrified whetstones having a high porosity obtained by firing at a temperature of 900 ° C. or lower.

  The vitrified grindstone is configured as a fan-shaped segment divided into a plurality of portions in the circumferential direction and radial direction of the surface plate of the lapping machine, and the segments are arranged without gaps and fixed to the upper surface plate and the lower surface plate preferable.

  The hard abrasive is a single diamond abrasive, a single cubic boron nitride (CBN) abrasive or a combination of diamond abrasive and cubic boron nitride abrasive, the soft abrasive is cerium oxide, Silica, barium sulfate, zirconium oxide alone or a mixture of two or more kinds of abrasive grains selected from them can be used.

The sharpness of the lower surface plate side grindstone can be made better than the sharpness of the upper surface plate side grindstone by any of the following methods 1) to 3).
1) The grain size of the lower surface plate side grindstone is made coarser than that of the upper surface plate side grindstone.
2) The hardness of the lower surface plate side grindstone is made lower than the hardness of the upper surface plate side grindstone.
3) Make the concentration of the lower surface plate side grindstone lower than the concentration level of the upper surface plate side grindstone.

  In the method of 1), the difference in the sharpness between the lower surface plate side grindstone and the upper surface plate side grindstone is 0.2 μm to 5 μm, more preferably 0. .3 μm to 3 μm, and the particle size (average particle size) of the lower surface plate side grindstone is preferably set to 0.3 μm to 8 μm, more preferably 0.4 μm to 6 μm.

  The specific setting of the grain size of the abrasive grains is 1 μm to 5 μm on the upper platen side, 1.5 μm to 8 μm on the lower platen side, and more preferably 1.5 μm on the upper platen side for roughing fixed abrasive wheels. 3 μm and the lower platen side are preferably 2.0 μm to 6 μm.

  Further, for the fixed abrasive grindstone for finishing, the upper surface plate side is 0.2 μm to 1.5 μm, the lower surface plate side is 0.3 μm to 2 μm, and more preferably, the upper surface plate side is 0.3 μm to 1 μm. The side should be 0.4 μm to 1.5 μm.

  The ratio of hard abrasive grains to soft abrasive grains is the ratio of only the two. As for the ratio in the volume ratio of the whole grindstone, hard abrasive grains: 25 to 40% and soft abrasive grains: 3 to 15% are appropriate.

  When the work to be processed is a highly brittle material, the higher the content ratio of hard abrasive grains (diamond abrasive grains or CBN abrasive grains), the more effective, but if the content ratio exceeds 40%, the spacing between abrasive grains becomes narrower. After that, the chip discharge property deteriorates, clogging occurs and the sharpness is lowered. Moreover, when the ratio is lower than 25%, the sharpness decreases from the initial stage.

  If the soft abrasive grain is less than 3%, the lubricating effect and the mechanochemical reaction effect cannot be expected, and if it exceeds 15%, the grindstone itself becomes brittle and causes abnormal wear, which is not economical.

  The volume ratio of the binder to the entire grindstone is 5 to 25%, more preferably 8 to 22%, and the ratio of the pores to the entire grindstone is 40% to the above. 65%, more preferably 40-60% is good.

  The ratio of the binder to the entire grindstone is usually low-pressure processing in lapping, so a low degree of bonding is often required. However, if it is less than 5%, it becomes difficult to support the abrasive grains. This leads to abnormal dropout of the grains, increasing the amount of wear of the grinding wheel and causing a situation where it is not cut. On the other hand, if it exceeds 25%, the low-pressure processing cannot perform self-generated blades (self-dressing), and the sharpness cannot be maintained and cannot be cut.

  When the ratio of the pores is less than 40%, it becomes difficult to keep the dropped abrasive grains in the pores and promote the function as free abrasive grains, and it becomes difficult to maintain a good sharpness by effectively using the dropped abrasive grains. On the other hand, when the ratio of the pores exceeds 65%, the sharpness is not a problem, but the wear amount of the grindstone is increased and the economic efficiency is lowered.

  In the method 2), the difference in the sharpness between the lower surface plate side grindstone and the upper surface plate side grindstone is 10-60 softer than the RL hardness of the upper surface plate side grindstone. It is good to set.

  Further, in the method of 3), the difference in sharpness between the lower surface plate side grindstone and the upper surface plate side grindstone is 10-30 lower than the concentration level of the upper surface plate side grindstone than the concentration level of the upper surface plate side grindstone. It should be set to the eyes.

  In addition, the carrier material for holding the workpiece included in the double-sided lapping machine of the present invention is a high-strength stainless steel, ribbon steel, carbon steel, alloy tool steel, high-speed tool steel for stable workpiece holding in rough machining. It is preferable to use chrome molybdenum steel or those made of those materials and applied with DLC (Diamond Like Coat), and glass epoxy resin is used for finishing because there are many workpieces that dislike metals.

  In addition, it is preferable that the carrier can be fitted and held in a state in which the work is prevented from rotating, because the work is suppressed from becoming a medium-high shape (an abacus spherical shape). The work can be prevented from being rotated by the carrier by providing an orientation flat and a flat fitting part or an uneven fitting part on the outer periphery of the work and the inner circumference of the carrier.

This invention uses a double-sided lapping machine described above, the rotational speed of the upper and lower surface plates: 20Rpm～100rpm, pressing load of the fixed abrasive grinding wheel to the ^workpiece: satisfies at least one of 160g / cm ² ~300g / cm 2 There is also provided a method for grinding thin-walled fine ceramics that simultaneously grinds both surfaces of a workpiece having a thickness of 0.7 mm or less under the conditions. The said pressing load is performed using the lapping machine which enabled the pressurization control of 50-300 g / cm < ² >.

  In this method, the difference in surface roughness between the upper and lower surfaces of a workpiece such as a wafer to be ground by the upper surface plate side grindstone and the lower surface plate side grindstone is within 0.15 μmRa, more preferably within 0.1 μmRa in roughing. The finishing process may be performed within 0.5 nm Sa, more preferably within 0.2 nm Sa.

Fine ceramics processed by this method include SiC, gallium nitride (GaN), aluminum nitride (AlN), gallium arsenide (GaAs), silicon nitride (Si ₃ N ₄ ), lithium tantalate (LT), niobium Lithium oxide (LN), lead zirconate titanate (PZT), lead zinc niobate titanate (PZNT), indium phosphide (InP), alumina, sapphire, crystal, quartz glass, hard glass, low Tg optical glass (aspherical surface lens optical glass), low expansion glass, zirconia, cordierite _{(2MgO · 2Al 2 O 3 ·} 5SiO 2) , and the like.

  The surface roughness in rough machining is expressed by arithmetic average roughness Ra, and the surface roughness in finishing processing is expressed by arithmetic average height Sa. Measurement of machined surface roughness in rough machining and measurement of machined surface roughness in rough machining cannot be performed at the arithmetic average height Sa, and it is necessary to request the measurement of machined surface roughness in finish machining to the outside. Because there was not.

  The vitrified grindstone employed in the double-sided lapping machine of the present invention is known as a fixed abrasive grindstone capable of high precision and high efficiency machining. This vitrified grindstone has many pores inside, and exhibits excellent sharpness due to the presence of the pores.

  In machining using this vitrified grindstone, the abrasive fluid dropped during machining is taken into the pores where the abrasive surface is released by grinding the working fluid (water may be sufficient) little by little, and ground as semi-fixed abrasive grains. It is utilized in. When segmented vitrified grinding stones are affixed to the grinding surface without gaps, the falling abrasive grains do not flow through the gaps between the grinding stone segments, and the falling abrasive grains are used without waste, contributing to improved machining efficiency. .

  In addition to this, in the processing with the fixed abrasive grindstone, the specifications of the lapping machine can be made higher than that of the lapping machine using loose abrasive grains. In addition, it is not necessary to consider the supply amount of loose abrasive grains into the lapping machine due to the processing conditions required for lapping machines using loose abrasive grains, and these synergistic effects enable high-speed rotation control, machining pressure (grinding stone pressing load). ) Can be realized with high constant pressure and high pressure control to improve the efficiency of double-sided lapping.

  Further, by using a superfinished grindstone in which fine abrasive grains are hardened with vitrified bonds as the vitrified grindstone, it is possible to improve the accuracy of double-sided lapping.

  The fixed abrasive grindstone can arbitrarily change the grain size, the porosity, hardness, and concentration of the grindstone, and the tempering of the grindstone attached to the upper and lower surface plates can be freely performed. As a result, it is possible to effectively reduce the warpage by performing double-sided simultaneous processing by making the grindstone for processing the front and back surfaces of the wafer suitable for each processing surface.

  The vitrified grindstone is a grindstone having a relatively soft hardness, and the flatness of the grinding surface can be easily corrected. Depending on the flatness of the polishing surface, there may be cases where even a double-sided lapping machine cannot achieve satisfactory workpiece flatness. However, by correcting the polishing surface to be flat, further improving and stabilizing the flatness of the wafer Can be planned.

  According to the fine ceramic grinding method of the present invention, high-efficiency and high-precision processing of fine ceramic semiconductor wafers including SiC wafers and reduction of wafer warpage over the conventional method can be achieved.

This is due to what was used a double-sided lapping machine described above, the rotational speed of the upper and lower surface plates 20Rpm～100rpm, that the pressing load of the fixed abrasive grinding wheel to the workpiece was set to 160g ^/ cm ² ~300g ^/ cm 2 It is an effect.

The following hard brittle fine ceramic wafer 0.7mm thickness, since the easily broken, with the processing, usually, the number of revolutions of platen: 5～20Rpm, pressing the grinding wheel during processing weights: ^50g / cm 2 ~150g / Cm ² is set.

In contrast, the method of the invention, the high rigidity of the lapping tool, the rotation rate of the stool: 20Rpm～100rpm, grindstone pressing weighted with respect to the ^workpiece: to allow setting of 160g / cm ² ~300g / cm 2 This high-speed rotation control and high constant pressure pressurization control, the adoption of vitrified grinding stones, the refinement of the grinding stones attached to the upper and lower surface plates, and the appropriate sharpness difference between the grinding wheels attached to the upper and lower surface plates Adjustment (adjustment that keeps the processed surface roughness of the upper and lower surfaces of the workpiece as small as possible) achieves higher processing efficiency, higher accuracy, reduced warpage, and further improved flatness.

  The upper limit of the rotational speed of the surface plate was set to 100 rpm because it was confirmed in a machining test that the workpiece wafer was damaged when the rotational speed was further increased.

The upper limit of the pressing load was set to 300 g / cm ² m because it was confirmed in the processing test that the wafer of the workpiece was damaged when a load higher than that was applied.

It is a perspective view which shows the principal part of an example of the double-sided lapping machine of this invention. It is the figure which looked at the principal part of FIG. 1 from the top. It is a top view which shows typically the carrier arrangement | positioning of the double-sided lapping machine used for the process test, and the set state of the SiC wafer of the workpiece | work with respect to each carrier. It is a top view which shows an example of the segment arrangement | sequence of the grindstone attached to the upper and lower surface plates of a double-sided lapping machine. It is sectional drawing which shows typically the processing image with the fixed abrasive grindstone in a lapping machine.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a double-sided lapping machine according to the present invention and a fine ceramic grinding method using the same will be described below with reference to FIGS.

  As shown in FIGS. 1 to 3, the illustrated double-sided lapping machine 1 is attached to an upper surface plate side grindstone 2 fixed to an upper surface plate (not shown) and a lower surface plate (also not shown). A lower surface plate side grindstone 3 to be fixed, a drive shaft 4 of the upper surface plate, a sun gear 5 disposed on the outer periphery of the drive shaft 4, and an internal gear 6 surrounding the outer periphery of the sun gear 5 are provided.

  Further, a plurality of carriers 7 which are respectively meshed with the sun gear 5 and the internal gear 6 and arranged between the sun gear 5 and the internal gear 6, and the upper surface plate is lowered to place the upper surface plate side grindstone 2 on the carrier 7. Is provided with a pressurizing device (indicated by an arrow in the figure) 8 using high constant pressure pressurizing control that presses against a workpiece (in the figure, a SiC wafer) W held on the substrate.

  As shown in FIG. 4, the upper surface plate side grindstone 2 and the lower surface plate side grindstone 3 are arranged on the upper and lower surface plates by arranging the grindstone segments 9 divided in the circumferential direction and the radial direction of the surface plate without any gaps. It has been.

  The illustrated double-sided lapping machine 1 is a 4-way method known for its high processing speed, and the upper surface plate (upper surface plate side grindstone 2) and the lower surface plate (lower surface plate side grindstone 3) rotate in opposite directions, The carrier 7 rotates in the same direction as the lower surface plate (the lower surface plate side grindstone 3) while revolving.

  The upper surface plate side grindstone 2 and the lower surface plate side grindstone 3 employed in the double-sided lapping machine 1 are hard abrasive grains having an average particle diameter of 8 μm to 0.1 μm and soft abrasive grains having an average particle diameter of 5 μm to 0.1 μm. Porosity of 40% to 65% of hard abrasive grains mixed at a mass ratio of 50% to 90%: soft abrasive grains: 50% to 10% and bonded with a binder containing a low melting point vitrified bond. , Binder ratio: 5 to 25% vitrified grinding wheel.

  As the hard abrasive grains, diamond abrasive grains or cubic boron nitride (CBN) abrasive grains having an average particle diameter in the range of 8 μm to 0.1 μm are used, and soft abrasive grains have an average particle diameter of 5 μm to 0.1 μm. A simple substance such as cerium oxide, silica, barium sulfate, zirconium oxide and the like, and a mixture of two or more kinds of abrasive grains selected from them are used.

  A vitrified bond having a low melting point and low shrinkage having a melting point and a thermal decomposition temperature of 900 ° C. or less is used. The low melting point / low shrinkage vitrified bond includes, for example, zinc carbonate or magnesium carbonate reactive sintering agent and lithium fluoride, but the example vitrified bond does not contain such an additive. A thing was used.

  The vitrified grindstone has many pores inside, and exhibits excellent sharpness due to the presence of the pores.

  The pores of the vitrified grinding wheel occupy 40% to 65% of the grinding wheel volume. Because of the pores, the edge effect of the hard abrasive grains around the pores that work as a cutting edge when machining the workpiece can be expected to easily bite into the work material. The effect of being held inside the open pores and being used as semi-fixed abrasive grains can also be expected.

  The processing image with the fixed abrasive grindstone in the lapping machine is shown in FIG. In the figure, 11 is diamond abrasive grains existing inside the grindstone, 12 is soft abrasive grains also existing inside the grindstone, 13 is a binder layer containing vitrified bonds, and 14 is present inside the grindstone. Medium-sized pores 15 are small-sized pores which are also present inside the grindstone, and 16 is crushed diamond abrasive grains which are dropped by processing and taken into open pores of the grinding surface.

  As shown in FIG. 5, in the processing using the fixed abrasive grindstone, the dropped abrasive grains are taken into the open pores of the abrasive surface and become semi-fixed abrasive grains, which are utilized without waste for grinding.

  The diamond abrasive grains 11 may be replaced with cubic boron nitride abrasive grains or a combination of diamond abrasive grains and cubic boron nitride abrasive grains. The soft abrasive grains 12 are simple substances such as cerium oxide, silica, barium sulfate, and zirconium oxide described above, or a mixture of two or more kinds of abrasive grains selected from them.

The lower surface plate side grindstone 3 is sharper than the upper surface plate side grindstone 2. The difference in sharpness between the upper surface plate side grindstone 2 and the lower surface plate side grindstone 3 is
1) The particle size of the lower surface plate side grindstone 3 is made coarser than the particle size of the upper surface plate side grindstone 2.
2) The hardness of the lower surface plate side grindstone 3 is made softer than the hardness of the upper surface plate side grindstone 2.
3) The concentration of the lower surface plate side grindstone 3 is made lower than the concentration level of the upper surface plate side grindstone 2.
It has been done either way.

  The sharpness adjustment by the method 1) is performed such that the particle size (average particle size) of the upper surface plate side grindstone 2 is 0.2 μm to 5 μm, more preferably 0.3 μm to 3 μm. The particle size is set to 1 to 2 steps coarser from 0.3 μm to 8 μm, more preferably from 0.4 μm to 6 μm.

  Specifically, for the grindstone for rough machining, the average particle size of the upper surface plate side grindstone 2 is 1 μm to 5 μm, more preferably 1.5 μm to 3 μm, and the average particle size of the lower surface plate side grindstone 3 is 1. It is set to 5 μm to 8 μm, more preferably 2 μm to 6 μm.

  Moreover, about the grindstone for finishing, the average particle diameter of the upper surface plate side grindstone 2 is 0.2 micrometer-1.5 micrometers, More preferably, 0.3 micrometers-1 micrometer, The average particle diameter of the lower surface plate side grindstone 3 is 0. .3 μm to 2 μm, more preferably 0.4 μm to 1.5 μm.

  The ratio of the hard abrasive grains to the soft abrasive grains in the volume ratio of the entire grindstone is 25 to 40% hard abrasive grains and 3 to 15% soft abrasive grains.

  The ratio of the binder in the volume ratio of the entire grindstone is more preferably 8 to 22%, and the ratio of the pores in the volume ratio of the entire grindstone is more preferably 40 to 60%.

  In the grindstone that gives a difference in sharpness by the method 2), the RL hardness of the lower surface plate side grindstone 3 is preferably set to 10 to 60 softer than the RL hardness of the upper surface plate side grindstone 2.

  Further, in the grindstone that gives a difference in sharpness by the method 3), the concentration of the lower surface plate side grindstone 3 is preferably set to be 10 to 30 lower than the concentration level of the upper surface plate side grindstone 2.

  The preferable hardness and concentration of the grindstone vary depending on the grain size of the abrasive grains used. The reason is that the number of abrasive grains contained in the grindstone varies greatly depending on the grain size.

  Considering this, the preferred RL hardness of a No. 2500 (average particle size 5 μm) grindstone having a high pressure applied to one particle is about 50 to 80, and the preferred concentration is 100 (abrasive rate 25%) to 140 (abrasive particles). (Rate 35%).

  In addition, the preferred RL hardness is about 0 to 70, and the preferred concentration is 100 (abrasive rate 25%) to 140 (abrasive) with a # 4000 (average particle size 2.5 μm) grindstone in which the pressure applied to one abrasive grain decreases. The grain ratio will be about 35%).

  Furthermore, since the number of abrasive grains is remarkably increased, the number 10000 (average particle diameter 0.5 μm) grindstone requires a low hardness and low concentration design to reduce the pressure applied to one abrasive grain. The preferred RL hardness will be about -50 to 10, and the preferred concentration will be about 60 to 100 (abrasive grain ratio 25%). In the ultrafine particle region, chip discharge is important, and the above range is considered appropriate for the concentration level to facilitate the discharge.

  Examples of this invention are given below. As a double-sided lapping machine, a 6B double-sided lapping machine (hereinafter referred to as a double-sided lapping machine) manufactured by Nippon Engis Co., Ltd. was used, and the following vitrified grinding stones were attached to the upper and lower surface plates of the double-sided lapping machine.

  The size of the surface plate is an outer diameter of 386 mm, an inner diameter of 148 mm, and a grinding wheel thickness of 5 mm. The workpiece (processing object) was a single-crystal SiC 2-inch wafer.

  As the wafer, an ingot having a diameter of 2 inches and a length of 15 mm was cut with a TOYO electrodeposition diamond saw T-8331A machine with a thickness of 0.45 mm.

  The cutting was performed with a wire having an electrodeposited diamond particle diameter of 30 to 40 μm and a diameter of 0.12 mm.

The measurement accuracy of the cut SiC wafer was as follows.
・ Wafer thickness: 0.413 to 0.459 mm
・ Wafer flatness (TTV): 9 to 35 μm
-Warp: 28-42 μm (Si surface is convex, C surface is concave)
Surface roughness: Si surface: 0.4 to 0.5 μmRa, C surface: 0.2 to 0.3 μmRa
Note that the warpage value referred to here is for the entire 2-inch wafer (and so on).

  Flatness and warpage were measured using Corning Tropel's flatness / parallelism / step difference measuring instrument MSP-150.

  In the roughing process, the difference in surface roughness between the upper and lower surfaces (Si surface and C surface) of the SiC wafer is set to 0.15 μmRa, more preferably within 0.1 μmRa in the roughing process, and the surface between the Si surface and the C surface in the finishing process. The target was to set the difference in roughness to 0.5 nmSa, more preferably within 0.2 nmSa.

-Whetstone used The grindstone uses composite abrasive grains (diamond abrasive grains + silica) as the reference grindstone, the diamond abrasive grain size is 4000 (average particle diameter: 2.5 μm), and the soft abrasive grain silica particle size is Average particle diameter: 3 μm, and vitrified bond was used as the binder.

  The grinding wheel hardness was medium “RL61” and the concentration was 126 (diamond abrasive grain ratio: 31.5% by volume). The RL hardness of this grindstone is a value measured using a Rockwell superficial hardness tester under conditions of a steel ball indenter of 3.175 mm, a basic load of 29.4 N, and a test load of 196 N.

  Prepare two pieces of the above-mentioned grindstone (with the fan-shaped segments divided in the circumferential direction and radial direction of the surface plate attached without any gaps), one is always fixedly attached to the upper surface plate, and the lower surface plate also has its A grindstone was attached. The grindstone attached to the lower surface plate was the same as that attached to the upper surface plate for the double-sided lapping machine for comparison.

  Moreover, about the double-sided lapping machine of the Example, the particle size of the diamond abrasive grain was made into 2500 coarse (average particle diameter: 5 micrometers) two steps. The grindstone hardness was “RL67” as a result of a design aimed at substantially the same hardness as No. 4000. The degree of concentration is 127 (diamond abrasive grain ratio: 31.8% by volume), which is almost the same as that of the upper surface plate side grindstone.

  In addition, the grain size is 4000, the concentration is the same as the upper surface plate side grindstone, the hardness is softer than the upper surface plate grindstone “RL45”, the concentration is 124 (diamond abrasive grain ratio: 31.0 volume) %) And a grindstone having a grain size of 4000, a concentration of 106 (diamond abrasive grain ratio: 26.5% by volume), and a hardness of “RL1” were also prepared. The binders for these wheels were all the same.

For the purpose of mirror finishing for additional processing, fixed abrasive grindstone of composite abrasive No. 10,000 {average diameter of diamond abrasive grains: 0.5 μm, soft abrasive grains of barium sulfate (BaSO ₄ )} having an average grain diameter of 1 μm Were prepared and attached to the upper and lower surface plates. The grindstone had an RL hardness of -11.
Table 1 shows the specifications of each grindstone, and Table 2 shows the composition of the binder.

・ Combination of test wheels (refer to Table 3 at the same time)
The upper surface plate side grindstone and lower surface plate side grindstone of the double-sided lapping machine of Comparative Example 1 are the same product of No. 4000 using composite abrasive grains, hardness “RL61”, concentration 126, and the SiC wafer of the workpiece is Si surface And set it on the carrier so that the rotation is prevented.

  The upper surface plate side grindstone of the double-sided lapping machines of Examples 1 to 6 is the same product having the number 4000, the hardness “RL61”, and the degree of concentration 126 using composite abrasive grains.

  The lower surface plate side grindstone of the double-sided lapping machine of Example 1 is No. 2500, the grain size of which is two steps coarser than that of the upper surface plate side grindstone. I set it in my career as it was done.

  The lower surface plate-side grindstone of the double-sided lapping machine of Example 2 was the same as that of Example 1, and the SiC wafer of the workpiece was set on the carrier so that the concave C surface was up and rotation was prevented.

  The lower surface plate side grindstone of Example 3 has a RL hardness of 20th softer than the upper surface plate side grindstone, “RL45”, and the SiC wafer of the workpiece has the Si surface up as in Example 1. , I set it on the carrier so that the rotation was stopped.

  The lower surface plate side grindstone of the double-sided lapping machine of Example 4 has a concentration of 106 lower than that of the upper surface plate side grindstone. As a result, the grindstone hardness becomes soft as “RL1”, and the sharpness is increased. The SiC wafer of the workpiece was set on a carrier so that the Si surface was up and the rotation was prevented.

  The lower surface plate side grindstone of the double-sided lapping machine of Example 5 is the same as that of Example 1, and the rotational speed of the upper and lower surface plates is about twice the rotational speed (29 rpm) of Comparative Example 1 and Examples 1 to 4. 60 rpm.

The lower surface plate side grindstone of the double-sided lapping machine of Example 6 is the same as that of Example 1, the rotational speeds of the upper and lower surface plates are the same as those of Comparative Example 1 and Examples 1 to 4, and the pressing load of the grindstone (actual load) Was set to 300 g / cm ² , which is approximately twice the pressing load (165 g / cm ² ) of Comparative Example 1 and other examples.

Processing target values Table 4 summarizes processing target values and processing conditions in the double-sided simultaneous lapping processing (rough processing and finishing processing) of a 2-inch SiC wafer.

・ Details of processing (coarse processing) with double-sided lapping machine For processing, the upper surface plate, lower surface plate, internal gear, and sun gear are driven independently using a 6B double-sided lapping machine manufactured by Nippon Engis Co., Ltd. having the structure shown in FIG. Therefore, the 4way / 4 motor system that reduces the processing load and can select the optimal rotation and revolution of the carrier has been adopted.

  For the lapping machine, the swing arm used in the 6B class (standard plate outer diameter φ386 mm) class was changed to a gate-type arm to increase the mechanical rigidity. In addition, in order to improve static accuracy, the upper and lower surface plates are designed to be water-cooled so that cooling water is passed through them, and the heat generated during high-speed and high-pressure machining is forcibly released.

  Furthermore, before the machining test, the grindstone attached (attached) to the lower surface plate was corrected on the machine for the purpose of improving the dynamic accuracy. The correction (accuracy) was a metal bond grindstone with a concentration of 50 employing diamond abrasive grains with an average number of 1000 (average particle diameter of 15 μm), and the flatness of the ground surface was within 1 μm. Thereafter, the accuracy was similarly determined for the grindstone that was inverted with respect to the lower surface plate and attached to the upper surface plate.

  As shown in FIG. 3, each of the three stainless steel carriers 7 having a thickness of 0.35 to 0.4 mm (see FIG. 1 for the sign, and the same applies below) to each of the workpieces W of a 2-inch SiC wafer. Three each were set, and the work W held by each carrier 7 was sandwiched between the upper surface plate side grindstone 2 and the lower surface plate side grindstone 3 attached to the upper surface plate and the lower surface plate.

  The upper surface plate is 29 rpm counterclockwise when viewed from above, the lower surface plate is 29 rpm clockwise when viewed from above, and the three carriers 7 are clockwise when viewed from above by adjusting the rotation of the sun gear 5 and the internal gear 6. The rotation of the rotation was set to 8 rpm.

  The shape of the inner side of the carrier 7 is made to coincide with the orientation flat shape of the workpiece W, so that free rotation within the carrier is prevented, and the carrier 7 rotates stably and reliably.

Pressurization by the pressurizer 8 was controlled to a constant pressure load of 30 kgf (actual load of 165 g / cm ² ).

  Since the workpiece W is a thin, brittle and fragile SiC wafer, the start of processing is to lower the conditions, the rotation speed of the upper and lower surface plates (that is, the rotation speed of the grindstone) is 10 rpm, and the carrier rotation The number was set to 2 rpm, and the load was started from 10 kgf, and the normal rotation speed and the normal load were reached over 40 seconds.

  And it processed for 20 minutes on the regular processing conditions. The end of processing will cause chipping or scratching of the workpiece if the lapping machine is stopped suddenly. After processing under normal conditions, the rotation speed of the surface plate will be up to 20 rpm and the carrier rotation speed will be up to 2 rpm. Was dropped to 10 kgf, and the lapping machine was stopped after 5 seconds.

The setting direction of the workpiece W (SiC wafer) was as summarized in Table 3.
As other conditions, when rotating the surface plate at a high speed, the pressure load was kept at 30 kgf and the rotation speed was set to 60 rpm. Further, when changing the pressure load, the rotation speed of the surface plate was kept at 29 rpm and the rotation speed of the carrier was kept at 8 rpm, and the load was set to 55 kgf (actual load 300 g / cm ² ), which is about twice the constant pressure load.

  As the coolant, water was used, and a supply amount of 20 ml / min was dropped into the grinding part.

  Regarding machining evaluation, the machining allowance was measured using a DIGIMICRO MFC-101A attached to a Nikon measuring stand MS-4G. Surface roughness after rough machining is measured with a non-contact laser microscope (VK-X-100, manufactured by Keyence), and warpage is measured with Corning Tropel's flatness / parallelism / step difference measuring instrument MSP-150. did. The conditions for this processing are summarized in Table 5, and the processing results are summarized in Table 6.

・ Summary of processing results Comparative example 1: The roughness of the processed surface is as good as half or less of the target, but the processing efficiency is small but the target value is not reached. The flatness is just below the standard. Although the warpage has been reduced by half, it is close to the standard limit. The direction of warping is reversed before and after processing, and the concave C surface before processing is convex.

  Example 1: The processing efficiency is 2.65 μm / min which is 1.7 times the target, and high efficiency is realized. The flatness and warpage are about half of the target values, and high accuracy is achieved. The direction of warping is not reversed and the Si surface remains convex. The processed surface roughness is in the range where there is no problem in roughing, although the C-plane processed with a coarse grindstone is rough.

Example 2: The processing efficiency is 2.8 μm / min, the average of which is 1.86 times the target, which is slightly higher than that of Example 1, and high efficiency is realized.
Flatness is also good. The warp reduction is particularly good, and all the samples are within 4 μm, and high accuracy is ensured.
As for the direction of curvature, the C surface is convex as in Comparative Example 1.
The processed surface roughness is such that the Si surface is rougher than the C surface because the C surface is raised at the time of setting the workpiece, but the surface roughness level is the same as that of the first embodiment and is in a range where there is no problem.

Example 3 The processing efficiency averaged 1.58 μm / min and cleared the target, but the results were not as good as those in Example 1 and Example 2 in which the lower surface plate side grindstone was rough. The flatness and warpage are about half the target values and are good.
The direction of warping has not changed before and after processing. As for the machined surface roughness, since both the upper and lower surface grindstones are No. 4000, a good surface is obtained.

Example 4: The processing efficiency averaged 1.70 μm / min, which cleared the target. The flatness and warpage may be about half of the target value. There is no reversal before and after processing in the direction of warpage.
The processed surface roughness is the same as in Example 3, since both the upper and lower surface grinders are No. 4000, and a good surface is obtained.

Example 5: Since the rotation speed of the upper and lower surface plates is set to 60 rpm, the machining allowance is further increased by 1.5 times compared to Example 1, and the machining efficiency is about 3.9 μm / min, so that high-efficiency machining is achieved. Has been made. The flatness and warpage were almost the same as in Example 1.
From the results of Example 5, it was confirmed that the machining efficiency can be significantly improved while maintaining the machining accuracy by increasing the rotation speed of the surface plate.

Example 6: By increasing the pressing load of the grindstone to 300 g / cm ² , the machining allowance is increased 1.6 times that of Example 1, and the machining efficiency is about 4.3 μm / min. Has been made. The flatness and warpage were almost the same as in Example 1.
By increasing the processing pressure (grinding stone pressing load), it was confirmed that the processing surface roughness was slightly roughened, but it was possible to improve the processing efficiency at a high level while maintaining the processing accuracy.

  Since the processed workpiece (SiC) is very expensive, the processing test was performed only once for all of the comparative examples and the examples. For this reason, the amount of wear of the grindstone was extremely small, and measurement was omitted because measurement was difficult.

  From the above experimental results, it has been confirmed that the use of a fixed abrasive grindstone with better sharpness on the lower surface plate side can effectively reduce workpiece warpage and improve the flatness of the workpiece. it can.

  Moreover, by using a fine grinding wheel for fine finishing as a fixed abrasive grindstone on the lower surface plate side and upper surface plate side, and further adjusting the difference in sharpness of the grindstone on the lower surface plate side and the upper surface plate side, It can be confirmed that the processed surface roughness of the workpiece can be greatly increased while suppressing the difference in surface roughness between the upper and lower surfaces of the workpiece.

  Furthermore, by increasing the rigidity of the double-sided lapping machine and increasing the rotation speed of the upper and lower surface plates, and increasing the pressing load of the fixed abrasive grindstone against the workpiece, the machining efficiency is greatly increased while ensuring excellent machining accuracy. It can also be confirmed that it can be increased.

-Finishing process Next, the finishing test results are shown below. Finishing was performed as an additional process for the workpiece (SiC wafer) after finishing rough processing by attaching fixed abrasive grindstones of the same quality of No. 10000 (average particle size: 0.5 μm) to the upper and lower surface plates.

The workpieces were three products of Comparative Example 1 in Table 6 and roughly processed products of Examples 1 and 2.
For the carrier of these workpieces, Comparative Example 1 was performed with the Si surface inverted in a concave direction facing up, Example 1 with the convex Si surface facing up, and Example 2 with the convex C surface facing up. It was.

The processing conditions were the same as the roughing except for the pressing load. The pressing load was 12 kgf (actual load 200 g / cm ² ). Further, the surface roughness of the processed surface after finishing was measured with a 3D optical profilometer made by Zygo, New View 8000.
The surface roughness in this finishing process was 0.8 nm Sa, and the processing efficiency was 0.1 μm / min. Table 7 shows the processing results.

・ Summary of machining results Comparative example 1: The machined surface roughness achieved the target and the machining efficiency cleared the target of 0.1 μm / min. However, the flatness was slightly worse than after the rough machining, and the warpage was within the standard. Although it was slightly worse than after rough machining. The direction of warping was the same as after roughing, and the Si surface was concave.

Example 1: The roughness of the processed surface was 0.468 nmSa for the Si surface and 0.691 nmSa for the C surface, achieving the target. The processing efficiency is about 1.5 times that of Comparative Example 1 and nearly twice the target value. As described above, despite the improvement in processing efficiency, the processed surface roughness is as good as that of Comparative Example 1.
The warpage is slightly improved from the end of the roughing process and has a good value less than half of the standard. The flatness is within the standard, but is slightly worse than that during rough machining. The direction of warping is the same as that during rough machining, and the Si surface is convex.

Example 2: The surface roughness of the Si surface was 0.433 nmSa and the C surface was 0.536 nmSa, and the target was achieved. The processing efficiency is also good as in Example 1. Moreover, although the machining efficiency is improved, the machined surface roughness shows a good value.
Warpage is good, less than half of the standard, but worse than at the end of roughing. The flatness is also within the standard but worse than at the end of roughing.
As for the direction of warping, the Si surface is concave as in the case of rough machining.

The grinding wheel wear amount was difficult to measure because the number of processing was small for each grinding wheel.
In the test in which the grinding wheel on the upper surface plate and the lower surface plate side was replaced with No. 2500 (average particle diameter: 5 μm) by this finishing, the processing rate was improved by 1.5 times. However, the flatness and warpage tended to deteriorate without improvement. There was no reversal of the direction of warping.

  The fixed abrasive grindstone of No. 10000 (average particle size: 0.5 μm) used for the upper and lower surface plates in the finishing process can achieve the target 0.8nmSa or less in the processed surface roughness, and the processed surface can be mirrored Met. In addition, although the machining efficiency was able to clear the target value, it was confirmed that the improvement of machining accuracy such as flatness and warpage could not be expected much.

・ Summary According to the double-sided lapping machine of this invention and the thin fine ceramic wafer grinding method using the same, high-efficiency machining of hard and brittle ceramic wafers with a thickness of 0.7 mm or less with thickness variations and warping has been realized. Further, it is possible to realize high precision of wafer flatness, warpage, and processed surface roughness on both upper and lower surfaces.

  The fixed abrasive grindstone attached to the upper surface plate and lower surface plate of the double-sided lapping machine is relatively high in porosity with hard abrasive grains having an average particle diameter of 8 μm or less and soft abrasive grains having an average particle diameter of 5 μm or less. By using a soft vitrified grindstone and increasing the sharpness of the lower surface plate side grindstone to that of the upper surface plate side grindstone, the upper and lower surfaces of the wafer can be corrected with high accuracy while keeping the difference in surface roughness to a minimum. it can.

  The grindstone, which has fan-shaped segments divided in the circumferential direction and radial direction of the surface plate without any gaps, can improve the sharpness more effectively by using falling abrasive grains, and contributes to the improvement of machining efficiency. high.

  The difference in sharpness between the lower surface plate side grindstone and the upper surface plate side grindstone is as follows. 2) Different hardness of both wheels. 3) Different concentrations of both wheels. In rough machining, the best result is obtained when the method 1) is adopted and the upper surface plate side grindstone is set to 4000 and the lower surface plate side grindstone is set to 2500.

  2) The adjustment of the sharpness difference between the upper and lower surface grindstones by the method of 3) can also be expected to improve machining efficiency, improve flatness, and reduce warpage. Adjustment by this method seems to be the best.

  If the lapping machine is made highly rigid to increase the rotation speed of the surface plate, or the pressing load of the grindstone against the workpiece is increased, the machining efficiency is further increased. If the sharpness of the lower surface plate side whetstone is made higher than the sharpness of the upper surface plate side whetstone by any one of the methods 1) to 3) above, and if the rotation speed of the surface plate and the pressing load of the whetstone are increased, It is inferred that good results were obtained for all of the efficiency, workpiece flatness and warpage, and surface roughness of the machined surface.

The above description has been made by taking a SiC wafer as an example of the fine ceramic of the workpiece. However, the double-sided lapping machine and the fine ceramic grinding method of the present invention are gallium nitride (GaN), aluminum nitride (AlN), gallium. Arsenic (GaAs), silicon nitride (Si ₃ N ₄ ), lithium tantalate (LT), lithium niobate (LN), lead zirconate titanate (PZT), lead zinc niobate titanate (PZNT), indium phosphide ( InP), alumina, sapphire, crystal, quartz glass, hard glass, low Tg optical glass, low expansion glass, zirconia, cordierite (2MgO · 2Al ₂ O ₃ · 5SiO ₂ ), etc. Excellent effect can be expected.

DESCRIPTION OF SYMBOLS 1 Double-sided lapping machine 2 Upper surface plate side whetstone 3 Lower surface plate side whetstone 4 Upper surface plate drive shaft 5 Sun gear 6 Internal gear 7 Carrier 8 Pressurizing device 9 Whetstone segment 11 Diamond abrasive grain 12 Soft abrasive grain 13 Binder layer 14 Medium size pores 15 Small size pores 16 Fracture diamond abrasive grains W Workpiece

As the coolant, water was used, and a supply amount of 20 ml / min was dropped onto the grinding part.

Claims (9)

It has a fixed abrasive grindstone attached to a lower surface plate and an upper surface plate, the fixed abrasive wheel is a hard abrasive having an average particle diameter of 8 μm to 0.1 μm and a soft abrasive having an average particle diameter of 5 μm to 0.1 μm. Porosity: 40% to 65%, in which the abrasive grains are mixed at a mass ratio of hard abrasive grains: 50 to 90%: soft abrasive grains: 50 to 10% and bonded with a binder containing a low melting point vitrified bond. Binder ratio: 5-25% vitrified grinding wheel,
The fixed abrasive grindstone attached to the lower surface plate is a double-sided lapping machine in which the grain size, hardness, or concentration is different from the fixed abrasive grindstone attached to the upper surface plate, and the sharpness is superior to that of the upper surface plate side.   A lapping machine used for roughing processing, wherein the average grain size of the fixed abrasive wheel attached to the upper surface plate is 1 μm to 5 μm, and the average particle size of the fixed abrasive wheel attached to the lower surface plate is 1.5 μm. The double-sided lapping machine according to claim 1, which is set to ˜8 μm.   A lapping machine used for finishing, wherein the average grain size of the fixed abrasive wheel attached to the upper surface plate is 0.2 to 1.5 μm, and the average particle diameter of the fixed abrasive wheel attached to the lower surface plate The double-sided lapping machine according to claim 1, wherein is set to 0.3 μm to 2 μm.   2. The double-sided lapping machine according to claim 1, wherein the RL hardness of the fixed abrasive wheel attached to the lower surface plate is set to be 10 to 60 softer than the RL hardness of the fixed abrasive wheel attached to the upper surface plate.   The double-sided lapping machine according to claim 1, wherein the concentration of the fixed abrasive wheel attached to the lower surface plate is set to be 10 to 30 lower than the concentration of the fixed abrasive wheel attached to the upper surface plate.   The hard abrasive is a single diamond abrasive, a single cubic boron nitride abrasive or a combination of diamond abrasive and cubic boron nitride abrasive, the soft abrasive is cerium oxide, silica, Barium sulfate, zirconium oxide alone or a mixture of two or more kinds of abrasive grains selected from them, the ratio of the hard abrasive grains and soft abrasive grains in the volume ratio of the entire abrasive wheel is hard abrasive grains: The double-sided lapping machine according to any one of claims 1 to 5, which is 25 to 40% and soft abrasive grains: 3 to 15%.   The both sides according to any one of claims 1 to 6 whose ratio in the volume ratio which occupies for the whole whetstone of said binder is 8-22%, and the ratio in the volume ratio which occupies for the whole whetstone of said pore is 40-60%. Lapping machine.   The fixed abrasive grindstone attached to the upper surface plate and the fixed abrasive grindstone attached to the lower surface plate are obtained by arranging the segments divided in the circumferential direction and the radial direction of the surface plate without gaps and attaching them to the surface plate. The double-sided lapping machine according to any one of claims 1 to 7. Using the double-sided lapping machine according to claim 1, the rotational speed of the upper and lower surface plates: 20Rpm～100rpm, fixed abrasive grinding wheel to the workpiece pressing ^load: the 160g / cm ² ~300g / cm 2 A thin-walled fine ceramic grinding method in which both surfaces of a workpiece having a thickness of 0.7 mm or less are ground simultaneously under a condition that satisfies at least one of the conditions.

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