JP4995103B2 - Polishing surface plate - Google Patents

Description

  The present invention relates to a polishing surface plate used for lapping.

  Flattening by lapping is used as a processing technique for a thin film head substrate, a semiconductor device manufacturing substrate, or the like that requires high polishing accuracy. In particular, when flatness is required on the surface of the workpiece, a double-sided lapping technique is employed in which lapping is performed simultaneously from the upper and lower surfaces of the workpiece.

  Double-sided lapping technology means that a workpiece is sandwiched between an upper surface plate and a lower surface plate for polishing, and a load is applied to the workpiece from at least one of the upper surface plate and the lower surface plate, while the upper surface plate and the lower surface plate are applied. This is a processing technology in which the workpiece is relatively moved between the upper and lower surface plates, thereby simultaneously lapping both sides of the workpiece with the upper surface plate and the lower surface plate. It is accommodated in a hole portion of a thin plate-like accommodation plate called a carrier that revolves while rotating by the mechanism, and is polished when moving between the upper surface plate and the lower surface plate, and high flatness is given to both surfaces.

  In recent years, as various materials have been developed, high-precision processing techniques for the developed materials are also required due to application needs. A typical example is a silicon carbide (SiC) single crystal substrate. SiC single crystals are particularly attracting attention as materials for substrate wafers for various devices including power devices for power, because they have excellent heat resistance and mechanical strength. As a semiconductor substrate for manufacturing various devices such as a Schottky barrier diode, its practical use is being accelerated.

  In addition, the development of SiC single crystal material itself has progressed remarkably, and large-diameter single crystal wafers having a diameter of 100 mm have been marketed (Non-patent Document 1). SiC single crystal needs to be processed into a wafer with high flatness, but since it has hardness next to diamond, there are various difficult problems with high-precision flattening. Solution is an issue.

As one of the processing technologies that realize high-precision flattening of hard and brittle materials such as SiC single crystals, the above-mentioned double-sided lapping technology has attracted a great deal of attention, with a view to improving productivity. Development is underway to establish a stable double-sided lapping technology.
JP-A-6-179165 RT Leonard, et al., International Conference on Silicon Carbide and Related Materials, (2007) Technical Digest Tue, Oct. 16, pp. Tu-39.

  If the polishing surface plate used for lapping is composed only of a polishing plate made of a soft metal material for polishing, the strength of the surface plate itself is insufficient and the surface plate cannot withstand the load during lapping. Deformation and other shape anomalies occur, causing the workpiece to have a polished shape that deteriorates or, in some cases, causes problems such as workpiece damage during lapping due to uneven contact with the surface plate. Sometimes. For this reason, in a polishing surface plate used for lapping, a reinforcing base material made of a high-strength metal material such as high-strength cast iron or stainless steel is used as a backing plate (hereinafter also referred to as “strength reinforcing plate”). It has become common to employ a double structure that is bonded or fused to the back surface of the polishing plate.

  By the way, in the polishing table having a double structure made of different materials as described above, when a temperature change occurs in the polishing apparatus itself or the polishing environment, the polishing platen warps due to a difference in thermal expansion coefficient of each material. Such a change in shape occurs. For example, according to the inventors' investigation, a 12 mm thick stainless steel (high strength metal material) backing plate is bonded to a pure tin (soft metal material for polishing) polishing plate (12 mm thickness, 380 mm diameter). In the case of the polishing surface plate, it has been found that when the surface plate temperature is uniformly increased by 20 ° C., the central portion warps about 120 μm from the peripheral portion so that the pure tin polishing plate side becomes convex ( (See FIG. 3).

  When the polishing surface plate that has caused the shape change caused by the temperature change of the polishing environment is used as the upper surface plate or the lower surface plate of the double-sided lapping machine, for example, in the above situation, the center of the surface plate In the vicinity of the part, the load acting on the work piece is unevenly increased, while in the peripheral part, the acting load is reduced, and in an extreme case, the work piece does not hit the surface plate surface and polishing does not proceed. As a result, the thickness of the workpiece to be finished eventually becomes non-uniform, and not only the purpose of high flattening processing is not achieved, but also excessive surface polishing due to non-uniform load Problems such as remaining scratches or, in the worst case, cracking of the workpiece during polishing occur. Such a temperature change may be caused not only by a temperature change in a processing laboratory or the like, but also by a processing heat generated during lapping, and in the present invention, all temperatures that change the surface plate temperature. The change is collectively referred to as the temperature change of the polishing environment.

  The thermal instability of the shape of such a polishing surface plate has been recognized in the past, and improvement measures such as devising the structure of a polishing plate made of a soft metal material for polishing have been proposed so far. (For example, patent document 1). However, complicating the structure of the polishing plate made of the soft metal material for polishing is a factor that increases the manufacturing cost of the polishing surface plate, and is not necessarily preferable as an industrial production means including the cost.

Under such circumstances, it has been desired to develop a polishing platen that can suppress the occurrence of shape change as much as possible by a simpler method even if the temperature changes in the polishing environment.
The present invention has been made in view of the above circumstances.

  The present invention is a polishing surface plate used for lapping which solves the above-mentioned problems, and the gist thereof is as follows.

  (1) A polishing surface plate for lapping a workpiece, a backing plate formed of a high-strength metal material and imparting a predetermined strength to the surface plate, and formed of a soft metal material for polishing. A polishing plate fixed to the workpiece polishing surface side of the plate and pressed against the workpiece during lapping, and a metal material for shape correction, and fixed to the back side of the backing plate and polished with the backing plate A polishing surface plate comprising: a shape correction plate for reducing a change in shape of the surface plate based on a difference in thermal expansion coefficient between the plate and the plate.

  (2) The polishing surface plate according to (1), wherein the shape correction plate has a thickness of 50% to 150% with respect to the thickness of the polishing plate.

  (3) The polishing platen according to (2), wherein the shape correction plate has a thickness of 70% to 130% with respect to the thickness of the polishing plate.

  (4) The shape correction metal material forming the shape correction plate has a thermal expansion coefficient at room temperature of ± 20% of the thermal expansion coefficient at room temperature of the polishing soft metal material forming the polishing plate. The polishing surface plate according to any one of (1) to (3), wherein

  (5) The shape correction metal material forming the shape correction plate has a coefficient of thermal expansion at room temperature of ± 10% of the coefficient of thermal expansion at room temperature of the soft metal material for polishing forming the polishing plate. The polishing surface plate as described in (4) above.

  (6) The polishing surface plate according to any one of (1) to (3), wherein the shape correction plate is made of the same material as the soft soft metal material for forming the polishing plate.

  (7) The soft metal material for polishing is at least one metal selected from the group consisting of copper, tin, and lead or an alloy containing the metal, The polishing surface plate described in 1.

  (8) The polishing surface plate according to any one of (1) to (7), wherein the workpiece is a ceramic hard material.

  (9) The polishing surface plate according to (8), wherein the ceramic hard material is a material made of silicon carbide and / or sapphire.

  (10) The polishing surface plate according to (9), wherein the ceramic hard material is a single crystal material.

  (11) A polishing apparatus comprising the polishing platen according to any one of (1) to (10).

  With the polishing surface plate of the present invention, heat between a polishing plate made of a soft metal material for polishing such as copper or tin and a backing plate made of a high-strength metal material such as cast iron or stainless steel in a lapping process. It is possible to suppress as much as possible the change in shape of the surface plate (hereinafter sometimes referred to as “surface plate deformation”) due to the difference in expansion coefficient, and without requiring special environmental temperature management for the polishing apparatus. In addition, it is possible to realize lapping with high flatness, and at the same time, it is possible to substantially eliminate substrate cracking during lapping of thin film head substrates, semiconductor device manufacturing substrates, and the like caused by deformation of the platen.

  It can be said that the deformation caused by the temperature change is a kind of bimetal effect in the polishing table having a double structure constituted by joining different kinds of metals as described above. That is, in the case of tin and stainless steel, the thermal expansion coefficients at room temperature are about 22 ppm / K (tin) and about 17 ppm / K (stainless steel), respectively. For this reason, when tin thermally expands, the tin side is deformed into a convex shape, and when it is thermally contracted, it is deformed into a concave shape. And in order to fundamentally avoid such thermal instability of the surface plate shape, it is preferable to give up dissimilar metal bonding and ensure the independence of individual metal parts on the surface plate, but double-sided lapping polishing In this case, it is customary to fix the platen to the polishing device by bolting etc. in consideration of the maintenance work of the platen, etc., but especially in the case of the upper platen, the polishing platen itself If the hometown is insufficient, the fixing method of the upper surface plate becomes unstable, which is not preferable from the viewpoint of achieving stable lapping.

Therefore, the inventors have the same or equivalent to the soft metal material for polishing that forms the polishing plate on the polishing surface side on the back surface side of the conventional double-structure polishing surface plate, that is, the back surface side of the backing plate. The present inventors have found that the bimetal effect can be suppressed by joining a shape correction plate made of a shape correction metal material (for example, metal or alloy) having a thermal expansion of 1 and completed the present invention.
The details are described below.

FIG. 1 shows the structure of the polishing surface plate of the present invention as an example.
First, the polishing surface plate of the present invention is made of a soft metal material for polishing, and is bonded to the surface side of the surface plate, that is, the polishing plate 1 positioned on the surface side of the surface plate for polishing the workpiece, and the back surface side The strength reinforcing backing plate 2 made of a high strength metal material and the shape correcting plate 3 made of a shape correcting metal material adhered to the back side of the backing plate 2 are formed as a whole. Make up structure.

  And about the metal material for shape correction which forms the shape correction plate 3, in order to suppress the bimetallic effect of the surface plate for polishing, it has the same thermal expansion coefficient as the soft metal material for polishing which forms the polishing plate 1, Alternatively, it is preferable to use a material having substantially the same thermal expansion coefficient. Here, the substantially equivalent thermal expansion coefficient means that the thermal expansion coefficient at room temperature of the shape correction plate 3 or the linear expansion coefficient is ± 20% of the thermal expansion coefficient value at room temperature of the polishing plate 1 made of a soft metal material for polishing. Within the range, more preferably within ± 10%. When outside the range of ± 20%, the suppression of the bimetal effect cannot be obtained, and the thermal instability of the surface plate shape due to the difference in thermal expansion between the polishing plate 1 and the shape correction plate 3 becomes obvious.

  Further, as the polishing soft metal material used as the polishing plate 1, various metals such as copper, tin, or lead generally used as a polishing plate metal or their alloys are selected, and the backing plate 2 For this, a high-strength metal material such as cast iron or stainless steel is selected. Furthermore, the shape correcting metal material for forming the shape correcting plate 3 of the present invention is basically not particularly limited as long as it has a thermal expansion coefficient at room temperature as described above. For example, the polishing plate 1 When the soft metal material for polishing used as tin (coefficient of thermal expansion: about 22 ppm / K) is used as the metal material for shape correction of the shape correction plate 3, tin (about 22ppm / K), duralumin (about; 21.6ppm / K), aluminum (same; about 23.1ppm / K), etc. are suitable, and when the soft metal material for polishing used as the polishing plate 1 is copper (thermal expansion coefficient; about 16.5ppm / K) Bronze (85Cu-15Sn, the same; about 17.3 ppm / K), brass (the same; about 18 ppm / K), etc. are suitable as the metal material for shape correction of the shape correction plate 3.

  Furthermore, regarding the thickness of the polishing plate 1 made of a soft metal material for polishing and the shape correcting plate 3 made of a metal material for shape correction, the thickness of the shape correction plate 3 is smaller than the thickness of the polishing plate 1. It is preferably 50% or more and 150% or less, more preferably 70% or more and 130% or less. If the thickness of the shape correction plate 3 is less than 50% or more than 150% of the thickness of the polishing plate 1, the balance of expansion or contraction from both sides of the backing plate 2 cannot be maintained, and the bimetal effect is exerted. It cannot be suppressed sufficiently.

  Here, the details of the present invention have been described with reference to FIG. 1 as an example. However, the present example shown in FIG. 1 is merely an example for explaining the outline of the present invention, and the contents of the present invention are limited. Note that it is not a thing. That is, in the case of the example shown in FIG. 1, the polishing plate 1 using pure tin as a polishing soft metal material is a lattice intended to efficiently remove processing waste and improve the circulatory performance of a polishing liquid containing diamond abrasive grains. Shaped grooves are provided. With respect to such a groove structure, there is no reason to specifically limit the details of the structure, and it may be concentric, spiral, or planar without a groove structure. Further, as shown in FIG. 2, even if the shape correction plate 3 is partially penetrated and the backing plate 2 and the polishing apparatus are fixed using the same material as the backing plate 2, the fixing stability of the surface plate can be improved. Good. By improving the fixing stability in this way, the load on the shape correction plate 3 can be increased even against high load lapping required in the case of ceramic-based hard and brittle materials such as silicon carbide and sapphire. Problems can be avoided, and problems such as deterioration in machining accuracy caused by instability of fixing of the surface plate can be avoided.

  Next, the thickness of the layer of the backing plate 2 constituting the polishing surface plate of the present invention will be described. In order to reduce the bimetal effect as described above, it is easily estimated that it is effective to sufficiently increase the thickness of each layer, for example, the thickness of the backing plate 2. However, if the thickness of the backing plate 2 is excessively large, the mass of the polishing surface plate itself becomes excessive, and it is difficult to perform surface adjustment (so-called surface correction processing) to be performed regularly and handling operations when replacing the surface plate. It is not realistic. Therefore, although depending on the surface plate diameter, for example, in the case of a polishing surface plate having a diameter of about 380 mm, the total thickness of the entire surface plate including the thickness of the backing plate and the thickness of the polishing plate is about 10 to 50 mm. It is customary to make it. Therefore, the thickness range defined in the present invention is such that the thickness of the backing plate 2 is approximately 50 mm or less, preferably 20 mm or less. In addition, the thickness of each layer of the polishing plate 1 and the shape correction plate 3 at this time is approximately 50 mm or less, preferably 20 mm or less, although depending on the surface plate diameter for the same reason.

  By the way, in order to improve the thermal stability of the shape of the polishing surface plate, it is conceivable to make the thickness of the polishing plate 1 sufficiently smaller than the thickness of the backing plate 2. However, as shown in Tables 3 and 4 (see Comparative Experimental Examples 1 to 3) in Example 2 of the present invention described later, the polishing plate 1 has a thickness (12.0 mm) with respect to the thickness of the backing plate 2 (12.0 mm). It is necessary to reduce the thickness to about 1 mm, and as described in the second embodiment, it is not practical as a polishing surface plate in continuously performing lapping.

  The effect of the present invention can be obtained by using the polishing surface plate of the present invention mounted on a normal single-side polishing apparatus or a double-side polishing machine.

  Examples of the present invention will be described below.

Example 1
Using a metal material shown in Table 1, a polishing surface plate including a polishing plate 1, a backing plate 2 and a shape correction plate 3 as shown in FIG. 1 was prepared.

  Both surface plate diameters are 380 mm. The thermal expansion coefficients at room temperature (20 to 30 ° C.) are about 22 ppm / K for pure tin and about 17 ppm / K for stainless steel SUS304. Each polishing platen is left in a room controlled at a temperature of 25 ° C. for about two days, and then the surface of the polishing plate 1 is removed by about 0.2 mm using a facing device for facing the surface plate. Flattening was performed. After flattening, the flatness of the surface plate surface was measured using a linear gauge with a resolution of 1 μm.

  Here, in the present invention, the flatness of the surface plate surface is the outermost circumference measured from the reference plane 5 when the polishing surface plate 7 having the structure shown in FIG. It is defined as the difference between the distance to the innermost circumference and the distance to the innermost circumference. As a result of the measurement, it was confirmed that both the polishing platen of the present invention and the polishing platen of the comparative experimental example were flattened with an accuracy of approximately 1 μm resolution or less.

  Subsequently, after the room temperature was lowered to 20 ° C. and it was confirmed that the temperature had reached a steady state, these polishing platens were further allowed to stand for about 3 days. Thereafter, when the flatness of the surface plate surface was measured in the same manner as described above, it was found that the flatness of the polishing surface plate of the present invention hardly changed below the resolution of the dial gauge used. On the other hand, in the polishing surface plate of the comparative experimental example, the polishing plate 1 side is deformed so as to be a concave surface, and as a result of the measurement, it is found that a concave surface warpage of about 41 μm occurs and the flattening is deteriorated. It was.

The test wafer was lapped using a double-sided lapping apparatus equipped with the polishing platen of the present invention and comparative experimental example. The slurry used is an oily slurry in which 9 μm diamond particles are suspended. A silicon carbide (SiC) single crystal substrate was prepared as a test wafer for double-sided lapping. The substrate is a single crystal substrate that is obtained by slicing a single crystal ingot with a diameter of about 50 mm using a multi-wire saw manufactured by a sublimation recrystallization method, and the entire surface is composed of 4H polytype and is micro There was no pipe defect density. In addition, as the double-sided lapping machine, an apparatus equipped with 5 carriers capable of accommodating 3 SiC single crystal substrates with a diameter of about 50 mm is used, and double-sided lapping is simultaneously applied to a total of 15 SiC single crystal substrates. Processed. The polishing time was 3 hours and the polishing load was about 200 g / cm ² .

  When the polishing surface plate of the present invention was used, the substrate properties of 15 SiC single crystal substrates were observed using an optical microscope after completion of the double-sided lapping polishing, but there were no cracks and 9 μm diamond particles A uniform satin state was realized. In addition, when the TTV (Total Thickness Variation) of the SiC single crystal substrate was measured using an optical flatness measuring device (NIDEK's Fringe Analizer FA-200), the average value of 15 substrates was 1.12 μm, which was hard and brittle. It was confirmed that good flattening was realized as the material of the SiC single crystal substrate having a diameter of about 50 mm.

  On the other hand, when the polishing surface plate of the comparative experimental example was used, normal lapping was difficult and the substrate cracked after about 30 minutes, so fatal surface scratches were observed on almost all SiC single crystal substrates. It occurred on the entire surface.

(Example 2)
Using the metal materials shown in Table 2, Table 3 and Table 4, a polishing platen comprising a polishing plate 1, a backing plate 2 and a shape correction plate 3 as shown in FIG. 1 was prepared. The three types of polishing surface plates produced were all 380 mm in diameter. As shown in Table 2, the polishing plate 1 made of pure tin (thermal expansion coefficient about 22 ppm / K) and stainless steel SUS304 (about 17 ppm / K) ) Made of three layers, namely a backing plate 2 made of pure tin and a shape correction plate 3 made of pure tin (about 22 ppm / K), the thickness of each layer constituting it was changed. For these polishing surface plates, the flatness of the surface plate surface was measured when the room temperature was changed from 25 ° C. to 20 ° C. in the same manner as in Example 1. Note that the polishing plate 1 made of pure tin has a layer thickness of about 12.2 mm immediately after fabrication, and the thickness after flattening by a facing device is all 12.0 mm.

  Tables 2 to 4 show the measurement results of the thickness ratio (%; plate 3 layer thickness / plate 1 layer thickness x 100) of the shape correction plate 3 to the polishing plate 1 and the warpage of the surface plate surface for each polishing platen. Also listed. In the polishing surface plates 1 to 5 of the present invention, the warpage of the surface plate surface is 10 μm or less, and it can be seen that sufficient flatness is maintained even with changes in room temperature. On the other hand, in the polishing surface plate of Comparative Experimental Example 1 without the shape correction plate 3, warping up to 38 μm occurs, and the flatness is greatly deteriorated.

Using the polishing surface plate of the present invention and comparative experimental examples in Tables 2 to 4, lap polishing was performed in the same manner as in Example 1 using a double-sided lap polishing apparatus. The slurry used is an oily slurry in which 9 μm diamond particles are suspended. However, a sapphire single crystal substrate was prepared as a test wafer for double-sided lapping. The substrate is a single crystal substrate that has been sliced from a single crystal ingot having a diameter of about 76 mm using a multi-wire saw. As the double-sided lapping apparatus, a total of five sapphire single crystal substrates were simultaneously lapped using an apparatus equipped with five carriers capable of accommodating one sapphire single crystal substrate having a diameter of about 76 mm. The polishing time was 3 hours and the polishing load was about 150 g / cm ² .

  When the polishing surface plate of the present invention is used, all of the polishing surface plates 1 to 5 are completed without causing substrate cracking during double-sided lapping polishing, and about 5 sapphire single crystal substrates are optical microscopes. The properties of the substrate were observed using No. 1, but there were no cracks, and a uniform satin state with 9 μm diamond particles was realized. Table 5 shows the average value of five TTVs measured using an optical flatness measuring device (NIDEK's Fringe Analizer FA-200). In both cases, a good flat shape is realized, but in particular when the layer thickness of the shape correction plate 3 is 70 to 130% with respect to the polishing plate 1, a good value with an average value of TTV of 3 μm or less. Is obtained.

  On the other hand, although it is a case where the polishing platen of the comparative experimental examples 1-3 shown in Tables 3 and 4 is used, when it carries out using the polishing platen of the comparative experimental examples 1 and 2, of Example 1 Substantially in the same manner as the comparative experimental example, the substrate cracked after about 30 minutes, and fatal surface scratches occurred on the entire surface of almost all sapphire single crystal substrates. Further, when the polishing platen of Comparative Experimental Example 3 is used, the lapping is completed without any particular problem, but the polishing plate 1 is very thin and the facing device for adjusting the surface properties after lapping is used. After the flattening process was performed, part of the layer of the polishing plate 1 was peeled off, so that it became unusable as a polishing platen for subsequent lapping.

(Example 3)
Using the metal materials shown in Table 6 and Table 7, a polishing platen consisting of a polishing plate 1, a backing plate 2 and a shape correction plate 3 as shown in FIG. 1 is prepared, and double-sided lapping using these is performed. It was. All the polishing surface plates are left in a room previously maintained at a temperature of 25 ° C., and the thickness of the polishing plate 1 (tin layer) after the polishing surface plate is flattened by a facing device is 10.0 mm. It is trying to become. For these polishing surface plates, the flatness of the surface plate surface was measured when the room temperature was changed from 25 ° C. to 20 ° C. in the same manner as in Example 1. The results are also shown at the bottom of Table 6 and Table 7.

These polishing surface plates were mounted on a double-sided lapping polishing apparatus, and double-sided lapping was performed in a processing environment controlled at a room temperature of 20 ° C. in the same manner as in Example 2. Here, a silicon carbide (SiC) polycrystalline dummy substrate for silicon substrate process monitoring was prepared as a test wafer for double-sided lapping. The main polytype was 3C, the substrate thickness was 1 mm, and the diameter was 100 mm. The surface of the substrate was already lapped in a substantially mirror state, and the substrate flatness (TTV) was about 3.5 μm. The slurry used here is an oily slurry in which 9 μm diamond particles are suspended. In addition, five carriers capable of accommodating one SiC polycrystalline dummy substrate having a diameter of 100 mm were mounted, and a total of five SiC polycrystalline dummy substrates were simultaneously lapped. The polishing time was 5 hours and the polishing load was about 130 g / cm ² .

  All of the polishing surface plates 6 to 10 were successfully completed without causing substrate cracking during double-sided lapping. Although the substrate properties of the five SiC polycrystalline dummy substrates were observed using an optical microscope, there were no cracks and a uniform satin state with 9 μm diamond particles was realized. Table 8 shows the average value of five TTVs measured using an optical flatness measuring device (Fringe Analizer FA-200 manufactured by NIDEK). In both cases, a good flat shape is realized, but particularly when the thermal expansion coefficient (linear expansion coefficient) of the layer of the shape correction plate 3 is approximately 90 to 110% of the value of the polishing plate 1. It can be seen that a good TTV average value of about 3 μm or less is obtained.

Example 4
Using the metal materials shown in Table 9 and Table 10, a polishing platen comprising a polishing plate 1, a backing plate 2 and a shape correction plate 3 as shown in FIG. 1 was prepared. Both diameters are 380 mm. All the polishing surface plates are left in a room previously maintained at a temperature of 25 ° C., and the thickness of the polishing plate 1 (tin layer) after the polishing surface plate is flattened by a facing device is 10.0 mm. It is trying to become. For these polishing surface plates, the flatness of the surface plate surface was measured when the room temperature was changed from 25 ° C. to 20 ° C. in the same manner as in Example 1. The results are also shown at the bottom of Table 8 and Table 9.

  The polishing surface plate 11 of the present invention has a total surface plate thickness of 30 mm, and realizes shape thermal stability with a warpage almost below the measurement accuracy limit (<1 μm) even when the temperature changes from 25 ° C. to 20 ° C. ing. On the other hand, in order to achieve thermal stability with only the SUC304 layer as the backing plate, a layer thickness of about 100 mm or more must be ensured, and the total thickness is considerably thicker than about 350% compared to the present invention. It becomes a polishing surface plate. Thus, it can be seen that by adopting the polishing surface plate having the structure of the present invention, it is possible to realize the thermal stability of the excellent shape with the same total thickness as the conventional polishing surface plate.

The lapping plates 11, 14, and 16 were lapped in a processing environment at a room temperature of 20 ° C. using a single-side polishing apparatus. A silicon carbide (SiC) single crystal substrate having a diameter of about 76 mm was prepared as a processing test wafer. The substrate was a single crystal substrate that had been sliced using a multi-wire saw, the entire surface was composed of 4H polytype, and there was no micropipe defect density. Prior to lapping, a SiC single crystal substrate is attached to a ceramic disc with wax using a wax, and the surface is processed by a surface grinder to form a reference surface for the substrate. The surface was again affixed to a ceramic disc with wax using a wax. At this time, a weight corresponding to a total load of 50 kg was placed so that the processing reference surface of the substrate and the ceramic board were sufficiently adhered. The slurry used for lapping was an oily slurry in which 9 μm diamond particles were suspended, the polishing time was 2 hours, and the polishing load was about 200 g / cm ² .

  After completion of the single-sided lapping, the substrate properties of each SiC single crystal substrate were observed using an optical microscope, but there were no cracks and a uniform matte state with 9 μm diamond particles was realized. After removing the substrate from the ceramic disk and thoroughly washing it, the TTV of the SiC single crystal substrate was measured in the same manner as in Example 3. The results are shown in Table 11. A substrate that has been lapped using the polishing surface plate 14 escapes substrate cracking due to the reinforcement effect of wax fixation, but the thickness near the center of the substrate is excessively large. When used for manufacturing, inconveniences such as difficulty in focusing can occur during the exposure process during device fabrication. In the case of the polishing surface plate 16, a good TTV equivalent to the polishing surface plate 11 of the present invention is realized. However, as described above, the total thickness exceeds about 350% compared to the present invention. This is a very thick polishing platen, and its mass is excessive, so that there are significant practical problems as a polishing platen.

(Example 5)
Using a metal material shown in Table 12, a polishing surface plate composed of a polishing plate 1, a backing plate 2 and a shape correction plate 3 as shown in FIG.

  Here, the tin-lead alloy was Sn-37% Pb (eutectic composition), and the coefficient of thermal expansion measured near room temperature was 24 ppm / K. In addition, the thermal expansion coefficient of stainless steel SUS304 at room temperature is 17 ppm / K. The surface plate diameter was 380 mm in all cases. As in Example 1, after flattening the surface plate in a room controlled at a temperature of 25 ° C., the room temperature was lowered to 20 ° C., and after confirming that the temperature was sufficiently steady, When the flatness was measured, it was found that the flatness of the polishing surface plate of the present invention hardly changed below the resolution of the dial gauge used. On the other hand, the polishing surface plate of the comparative experimental example is deformed so that the polishing plate 1 side is concave, and as a result of the measurement, the concave surface warpage of about 49 μm occurs and the flatness is deteriorated. I understood.

  Using the polishing surface plate of the present invention and comparative experimental examples shown in Table 12, lapping was performed using a double-sided lapping polishing apparatus in a polishing environment at room temperature of 20 ° C. The implementation conditions were almost the same as in the examples. That is, the slurry used is an oily slurry in which 9 μm diamond particles are suspended, and a SiC single crystal substrate sliced from a single crystal ingot having a diameter of about 50 mm using a multi-wire saw is used as a lap polishing test substrate. It was. When the polishing surface plate of the present invention in Table 12 is used, no cracks are generated on the substrate after completion of the double-sided lapping polishing, and a uniform textured surface processing state is realized. This was confirmed by observation with an optical microscope. Further, the average TTV of the substrate by the optical flatness measuring apparatus was 1.07 μm, and it was confirmed that good flatness was realized. On the other hand, when the polishing platen of the comparative experimental example in Table 12 was used, the substrate cracked immediately after the start of polishing, and fatal surface scratches occurred on the entire surface of almost all substrates.

FIG. 1 is an explanatory view for explaining an example of a polishing surface plate of the present invention, FIG. 1 (a) is a top view of the polishing surface plate, and FIG. 1 (b) is a polishing surface plate. FIG.

FIG. 2 is an explanatory view for explaining an example of the polishing surface plate of the present invention, FIG. 2 (a) is a top view of the polishing surface plate, and FIG. 2 (b) is a polishing surface plate. FIG.

FIG. 3 is an explanatory diagram for explaining the definition of warping of the surface plate surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polishing plate 2 Backing plate 3 Shape correction plate 4 Reinforcing member for fixing to polishing apparatus 5 Reference plane 6 Flatness of surface plate surface 7 Surface plate for polishing

Claims (11)

  A polishing surface plate for lapping a workpiece, a backing plate formed of a high-strength metal material and imparting a predetermined strength to the surface plate, and a soft metal material for polishing. A polishing plate fixed to the workpiece polishing surface side and pressed against the workpiece during lapping, and formed of a metal material for shape correction, and fixed to the back surface side of the backing plate, the backing plate and the polishing plate A polishing surface plate comprising: a shape correction plate that reduces a change in shape of the surface plate based on a difference in thermal expansion coefficient between the surface plate and the surface plate.   The polishing platen according to claim 1, wherein the shape correction plate has a thickness of 50% or more and 150% or less with respect to the thickness of the polishing plate.   The polishing platen according to claim 2, wherein the thickness of the shape correction plate is 70% or more and 130% or less with respect to the thickness of the polishing plate.   The shape correction metal material forming the shape correction plate has a coefficient of thermal expansion at room temperature of ± 20% of the coefficient of thermal expansion at room temperature of the soft metal material for polishing forming the polishing plate. The polishing surface plate according to any one of claims 1 to 3.   The metal material for shape correction forming the shape correction plate has a coefficient of thermal expansion at room temperature of ± 10% of the coefficient of thermal expansion at room temperature of the soft metal material for polishing forming the polishing plate. The polishing surface plate according to claim 4.   The polishing surface plate according to any one of claims 1 to 3, wherein the shape correction plate is made of the same material as the soft metal material for polishing that forms the polishing plate.   The polishing soft metal material is at least one metal selected from the group consisting of copper, tin, and lead or an alloy containing the metal. Surface plate.   The polishing surface plate according to claim 1, wherein the workpiece is a ceramic hard material.   The polishing surface plate according to claim 8, wherein the ceramic hard material is a material made of silicon carbide and / or sapphire.   The polishing surface plate according to claim 9, wherein the ceramic hard material is a single crystal material.   A polishing apparatus comprising the polishing platen according to any one of claims 1 to 10.

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