JP2016007690A - Method for manufacturing sapphire substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a sapphire substrate capable of performing an intermediate polishing step in such conditions as not to depend on layer constitution of a working deterioration layer before performing a mirror surface polishing step after a rough polishing step and capable of suppressing a time of the mirror surface polishing step.SOLUTION: A manufacturing method of a sapphire substrate includes: a rough polishing step of performing rough polishing of a main surface of a sapphire substrate 10, a crystal plane of the main surface being r plane; an intermediate polishing step of polishing the main surface of the sapphire substrate 10 with a diamond fixed abrasive grain after the rough polishing step; and a mirror surface polishing step of performing mirror surface polishing of the main surface of the sapphire substrate 10 after the intermediate polishing step. Therein, the intermediate polishing step has such a low load polishing step that polishing is performed with a polishing load of 50 g/cmor less when the mirror surface polishing of the main surface of the sapphire substrate 10 is performed, and the low load polishing step is started when the residue of allowance in the intermediate polishing step is 25 μm or more and is continuously performed until the intermediate polishing step ends.

Description

  The present invention relates to a method for manufacturing a sapphire substrate.

  In recent years, sapphire substrates have also been used as silicon growth substrate (SOS substrates: silicon on sapphire substrates) materials used in electronic devices. When used in such applications, a method is employed in which an electronic device structure is formed by epitaxially growing a silicon layer on the main surface of a sapphire substrate whose main surface crystal face is an r-plane. For this reason, a sapphire substrate whose crystal surface of the main surface is an r-plane has been demanded.

  The sapphire crystal has a rhombohedral crystal structure, and there are various crystal planes such as a-plane, c-plane, m-plane, and r-plane depending on the crystal orientation. And it is known that the sapphire crystal has a difference in physical properties depending on the crystal orientation. For example, in a sapphire crystal, although there is no cleavage plane of the crystal, there is a direction in which it is easy to break.

  As described above, sapphire crystals have various crystal faces and there are differences in physical properties. Therefore, when producing a sapphire substrate, the processing characteristics may differ depending on which crystal face is processed. is there. For example, Non-Patent Document 1 reports that the polishing rate for mirror polishing is faster on the c-plane than on the a-plane and r-plane.

  By the way, as the sapphire substrate, a mirror substrate in which at least one main surface is mirror-polished is generally used. For example, such a mirror substrate is manufactured by cutting a sapphire ingot to form a flat plate, and then performing rough polishing and mirror polishing.

  A typical example of rough polishing is lapping using boron carbide or silicon carbide as an abrasive. A typical example of mirror polishing is polishing using colloidal silica or alumina. In rough polishing, in order to obtain a desired shape in a short time, high-speed polishing is usually performed, but on the other hand, a work-affected layer is easily introduced.

  For example, as disclosed in Patent Document 1, the work-affected layer includes a mosaic layer and a crack layer, and depending on the polishing conditions, there may be a set of pear ground or scratches. May be present. Such a work-affected layer is different in structure and properties from a normal crystal part and may be more brittle than the rest of the substrate. In addition, crystals such as sapphire need to be removed because they cause growth failure and distortion during epitaxial growth.

  In particular, the r surface of the sapphire substrate is susceptible to brittle fracture of the polished surface due to polishing, and therefore, a work-affected layer is more easily formed in rough polishing than the c surface. Furthermore, as described above, since the polishing speed of the r-plane is slower than that of the c-plane, conventionally, the polishing time for removing the work-affected layer by mirror polishing has been long.

  Therefore, in the sapphire substrate whose main surface crystal surface is r-plane, it has been particularly required to reduce the thickness of the work-affected layer on the main surface of the substrate subjected to the mirror polishing process in order to increase productivity.

  Therefore, conventionally, in order to suppress the formation of a work-affected layer when performing rough polishing, a method of polishing by reducing the polishing load at the time of rough polishing to the extent that the self-generated action of the grindstone is not hindered may be employed. . However, according to such a method, since the polishing load during the rough polishing is reduced, it takes a long time for the rough polishing, resulting in a problem that productivity is lowered in the entire polishing process.

  In addition, the amount of rough polishing is reduced, and polishing with intermediate properties between rough polishing and mirror polishing, such as lapping using loose abrasives with diamond as abrasives and double-sided lapping using fixed abrasives, is fixed. In some cases, the method is performed between rough polishing and mirror polishing under the above conditions.

  However, even when such intermediate property polishing is performed between rough polishing and mirror polishing, the generation of a work-affected layer cannot be reduced sufficiently, so that the polishing time during mirror polishing can be sufficiently reduced. It was not possible to improve productivity.

  For example, Patent Document 1 discloses that when a substrate made of sapphire or silicon carbide is ground, first, rough grinding is performed, then finish grinding is performed, and finally lapping is performed. Then, as a method of finish grinding, the grinding part provided with the grinding wheel for grinding the substrate is rotated, the chuck arranged to face the grinding wheel of the grinding part, the chuck for holding the substrate is rotated, and the grinding part is It is disclosed that the grinding ratio of the substrate with respect to the grinding wheel is changed in accordance with the feeding amount fed toward the chuck along the rotation axis and feeding the grinding part. In particular, it is disclosed that the grinding ratio is changed according to each layer of the work-affected layer.

  According to the finish grinding method disclosed in Patent Document 1, the work-affected layer after finish grinding is made smaller than the work-affected layer after rough grinding by changing the grinding ratio according to each layer constituting the work-affected layer. In addition, it is said that the time required for lapping can be reduced.

  However, in the finish grinding method disclosed in Patent Document 1, it is necessary to previously know the thickness of each layer in the work-affected layer by experiments or the like, which may reduce productivity.

A. T. T. et al. Budnikov; Functional Materials 17, No. 1 4 (2010)

JP2011-218545A

  Therefore, in view of the above-described problems of the prior art, in one aspect of the present invention, after the rough polishing step, before the mirror polishing step, the intermediate polishing step can be performed under conditions that do not depend on the layer structure of the work-affected layer. It aims at providing the manufacturing method of the sapphire substrate which can suppress the time of a grinding | polishing process.

In order to solve the above problems, according to one aspect of the present invention, a rough polishing step of rough polishing a main surface of a sapphire substrate whose main surface crystal face is an r-plane;
After the rough polishing step, an intermediate polishing step of polishing the main surface of the sapphire substrate with diamond fixed abrasive,
After the intermediate polishing step, having a mirror polishing step for mirror polishing the main surface of the sapphire substrate,
The intermediate polishing step includes a low load polishing step in which polishing is performed with a polishing load of 50 g / cm ² or less when the main surface of the sapphire substrate is mirror-polished.
The low-load polishing step is provided when the remaining machining allowance in the intermediate polishing step is 25 μm or more and continues until the intermediate polishing step is completed.

  According to one aspect of the present invention, after the rough polishing step and before the mirror polishing step, the intermediate polishing step can be performed under conditions that do not depend on the configuration of the work-affected layer, and the time of the mirror polishing step can be suppressed. A method for manufacturing a sapphire substrate can be provided.

The perspective view of the sapphire substrate which concerns on embodiment of this invention. The top view of the double-side polish apparatus concerning the embodiment of the present invention. Sectional drawing in the AA 'line of FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments, and the following embodiments are not departed from the scope of the present invention. Various modifications and substitutions can be made.

  In the present embodiment, a configuration example of a method for manufacturing a sapphire substrate will be described.

  The manufacturing method of the sapphire substrate of this embodiment can have the following processes.

  A rough polishing step of rough polishing a main surface of a sapphire substrate whose main surface crystal surface is an r-plane.

  An intermediate polishing step in which the main surface of the sapphire substrate is polished with diamond fixed abrasive grains after the rough polishing step.

  A mirror polishing process in which the main surface of the sapphire substrate is mirror polished after the intermediate polishing process.

The intermediate polishing step may include a low load polishing step in which polishing is performed with a polishing load of 50 g / cm ² or less when the main surface of the sapphire substrate is mirror-polished. The low-load polishing step can be started when the remaining machining allowance in the intermediate polishing step is 25 μm or more and continued until the intermediate polishing step is completed.

  First, an outline of a sapphire substrate manufactured in the method for manufacturing a sapphire substrate of this embodiment will be described.

  For example, as shown in FIG. 1, the sapphire substrate 10 can have a disk shape, and has an upper surface 11 and a lower surface 12 that are main surfaces, and is between the outer peripheral edge of the upper surface 11 and the outer peripheral edge of the lower surface 12. Can have an end face 13. Although not shown in FIG. 1, a chamfered portion may be provided between the upper surface 11 and the end surface 13 and between the lower surface 12 and the end surface 13.

  And according to the manufacturing method of the sapphire substrate of this embodiment, an intermediate | middle grinding | polishing process can be implemented on the conditions which do not depend on the structure of a process-affected layer, and the time of a mirror polishing process can be suppressed. For this reason, a work-affected layer is likely to be generated in the rough polishing step, and this effect is particularly effective when the r-surface having a slow polishing rate during mirror polishing is the main surface. For this reason, the crystal planes of the upper surface 11 and the lower surface 12 that are main surfaces can be r-planes.

  Further, as described above, since the sapphire substrate is used as a substrate for crystal epitaxial growth, for example, it is preferable that at least one main surface on which the crystal is epitaxially grown has a work-affected layer removed and a mirror surface. .

  Next, each process of the manufacturing method of the sapphire substrate of this embodiment is demonstrated.

  First, the rough polishing process will be described.

  In the rough polishing step, rough polishing can be performed on the main surface of the sapphire substrate having a disk shape.

  In the rough polishing step, it is preferable to perform rough polishing on the upper surface 11 and the lower surface 12 which are a pair of main surfaces of the sapphire substrate 10.

  In the rough polishing step, for example, when a sapphire single crystal ingot is sliced into a disk-shaped sapphire substrate, the warpage included in the substrate is removed to a certain extent, and the main surface is polished to have a predetermined surface roughness. be able to. For this reason, the polishing conditions in the rough polishing step are not particularly limited, and can be arbitrarily selected according to characteristics of the sapphire substrate subjected to the rough polishing step, characteristics required for the sapphire substrate to be manufactured, and the like. .

  However, in the rough polishing step, in order to remove the warp of the sapphire substrate and sufficiently reduce the surface roughness of the main surface, for example, each main surface of the sapphire substrate is preferably polished by 70 μm or more, each 75 μm. It is more preferable to polish as described above.

  Although the polishing method used when performing rough polishing in the rough polishing step is not particularly limited, for example, it is preferable to perform polishing using loose abrasive grains. The material of the abrasive grains used is not particularly limited, but diamond, alumina, boron carbide, silicon carbide, etc. can be preferably used. Among these, boron carbide or silicon carbide can be more preferably used from the viewpoint of cost and polishing rate.

  In the rough polishing step, it is preferable to select the grain size of the abrasive grains so that a sufficient polishing rate can be secured. For example, it is preferable to perform polishing using abrasive grains having an average particle size of 20 μm to 100 μm. The average particle size means a particle size at an integrated value of 50% in the particle size distribution obtained by the laser diffraction / scattering method, and the average particle size in this specification has the same meaning in other portions.

  The rough polishing step can be performed using, for example, a double-side polishing apparatus.

  Next, the intermediate polishing process will be described.

  The intermediate polishing step can be performed after the rough polishing step, and the main surface of the sapphire substrate can be polished with diamond fixed abrasive grains.

  In the intermediate polishing step, it is preferable to perform intermediate polishing on the upper surface 11 and the lower surface 12, which are a pair of main surfaces of the sapphire substrate 10, using, for example, a double-side polishing apparatus.

  A configuration example of the double-side polishing apparatus will be described with reference to FIGS.

  FIG. 2 is a top view of the double-side polishing apparatus 20 and shows a state where the upper surface plate is removed so that the internal structure can be easily understood. FIG. 3 shows a cross-sectional view taken along the line AA ′ of FIG. 2, and FIG. 3 also shows the upper surface plate.

  As shown in FIG. 2, a carrier 21 having a gear around it is prepared so that the carrier 21 can rotate and revolve by being engaged with the sun gear 22 and the internal gear 23 of the double-side polishing apparatus 20. A sapphire substrate 10 to be polished is placed in a plurality of through holes provided in the carrier 21, and the carrier 21 on which the sapphire substrate 10 is placed is set in a double-side polishing apparatus 20. Thus, by installing the sapphire substrate 10 on the carrier, the horizontal movement of the substrate can be restricted when performing double-side polishing.

  As shown in FIG. 3, the upper surface plate 31 and the lower surface plate 32 are pressed against the sapphire substrate 10 set on the carrier 21 from the upper surface side and the lower surface side in the double-side polishing apparatus. Diamond fixed abrasive grains can be arranged on the surface of the upper surface plate 31 and the lower surface plate 32 facing the sapphire substrate 10. In this state, by rotating the sun gear 22 and the internal gear 23 at a desired speed, the carrier 21 can be revolved and rotated in the double-side polishing apparatus, and the main surface of the sapphire substrate 10 can be polished.

  Note that the same double-side polishing apparatus can be used in the rough polishing step described above, but when performing polishing using loose abrasive grains in the rough polishing step, the upper surface plate 31 and the lower surface plate 32, Polishing is performed while supplying free abrasive grains (polishing liquid) to the sapphire substrate 10. A polishing pad can be arranged on the surface of the upper surface plate 31 and the lower surface plate 32 facing the sapphire substrate 10.

The intermediate polishing step can include a low-load polishing step of polishing with a polishing load of 50 g / cm ² or less when the main surface of the sapphire substrate is mirror-polished. The low-load polishing step can be started when the remaining machining allowance in the intermediate polishing step is 25 μm or more and continued until the intermediate polishing step is completed.

  This is because by removing the polishing load at the final stage of the intermediate polishing process, it is possible to remove and reduce the work-affected layer formed on the main surface of the sapphire substrate in the rough polishing process or the like. This is because the polishing time can be shortened.

  As described above, the low load polishing step is preferably started when the remaining machining allowance in the intermediate polishing step is 25 μm or more, more preferably 35 μm or more. However, if the low-load polishing step is started too early, it takes time to polish the main surface of the substrate. Therefore, it is preferable to start after the remaining machining allowance in the intermediate polishing step is 40 μm or less.

  Here, the remaining machining allowance in the intermediate polishing step is 25 μm or more means that the remaining machining allowance for each main surface is 25 μm or more. It means that it is 25 μm or more.

  In the intermediate polishing step, it is preferable to polish the main surface in a state where the polishing load is larger than the low load step until the low load step is started. This is because the work-affected layer formed on the main surface can be removed and reduced by polishing at a low load step to reduce the polishing load. Therefore, until the low load step is performed, the polishing load is increased and the polishing speed is increased. It is because it is preferable to raise.

In particular, the intermediate polishing step has a high-load polishing step for polishing with a polishing load of 160 g / cm ² or more when polishing the main surface of the sapphire substrate, and the low-load polishing step after the high-load polishing step is completed. Is preferably performed.

In the high load polishing step, the main surface of the substrate can be polished at a high polishing rate by polishing with a polishing load of 160 g / cm ² or more as described above. In particular, in order to increase the polishing rate, it is more preferable to perform polishing with a polishing load of 180 g / cm ² or more.

  The intermediate polishing process can be composed of the above-described high-load polishing step and low-load polishing step. For example, an intermediate-load polishing step is provided between the high-load polishing step and the low-load polishing step, and the intermediate polishing process is stepwise. In addition, the polishing load may be reduced.

  The upper limit of the removal allowance (polishing allowance) to be polished in the intermediate polishing step is not particularly limited, and is arbitrary depending on the state of the substrate after the rough polishing step and the characteristics required for the substrate when made into a product. Can be selected. The total amount of machining allowance in the intermediate polishing step is preferably, for example, 50 μm or more, and more preferably 55 μm or more.

  Next, the mirror polishing process will be described.

  In the mirror polishing process, after the intermediate polishing process, the main surface of the sapphire substrate can be polished to have a desired surface roughness. Since the sapphire substrate is often mirror-polished on one main surface and processed into a satin finish on the other main surface, the mirror-polishing step can be performed, for example, on one selected main surface. However, mirror polishing may be performed on both the pair of main surfaces, that is, the upper surface and the lower surface, if necessary.

  Although the specific method of a mirror polishing process is not specifically limited, It can grind | polish with a loose abrasive grain. Although the material of the abrasive grain to be used is not particularly limited, colloidal silica, alumina or the like can be preferably used. Among these, colloidal silica can be more preferably used from the viewpoint of finished surface roughness.

  The mirror polishing step can be performed by, for example, a single-side polishing apparatus. Moreover, when performing mirror polishing about a pair of main surface of a sapphire substrate, it can also implement using the double-side polish apparatus similar to the case of a rough polishing process. The polishing load in the mirror polishing process is not particularly limited.

  Although it does not specifically limit about the grade which performs a mirror polishing process, It is preferable to implement so that the process-affected layer formed in the main surface may be removed. For example, a preliminary test is performed, and the thickness of the work-affected layer remaining on the main surface after the intermediate polishing step is measured by a cross-sectional observation using a transmission electron microscope (TEM), a method using a laser Raman method or laser scattering, or the like. It is preferable to keep it. The polishing amount in the mirror polishing step is preferably equal to or greater than the thickness of the work-affected layer.

  Moreover, an arbitrary process can be further added to the manufacturing method of the sapphire substrate of this embodiment. Examples of optional steps to be added will be described below.

  For example, before performing the above-described rough polishing step, a cutting step of slicing a cylindrical sapphire ingot to manufacture a sapphire substrate can be performed.

  Although the method of slicing the cylindrical sapphire ingot in the cutting step is not particularly limited, for example, it can be sliced with a multi-wire saw or the like.

  Moreover, the chamfering process which chamfers the end surface of a sapphire substrate can be implemented. In the chamfering step, for example, as described above, a chamfered portion can be formed between the main surface and the end surface of the sapphire substrate. The shape of the chamfered portion is not particularly limited. For example, the shape of the chamfered portion can be a linear shape or a curved shape in a cross section passing through the central axis of the sapphire substrate and perpendicular to the upper surface.

  When the chamfered portion is formed by taper processing to form an inclined surface, the cross-sectional shape of the chamfered portion can be a linear shape as described above. Further, when the chamfered portion is formed by a rounded chamfering process and has a rounded curved surface shape, the cross-sectional shape of the chamfered portion can be a curved shape.

  As described above, one main surface of the sapphire substrate can be mirror-polished and the other main surface processed into a satin finish. For this reason, the back surface grinding | polishing process processed into a satin-like shape about the other main surface which does not implement mirror surface grinding | polishing can be implemented. Although the method of processing the other main surface into a satin finish is not particularly limited, it can be processed into a satin finish, for example, by sandblasting or single-side polishing using loose abrasive grains.

  Further, when one main surface is a mirror surface and the other main surface is a satin finish, the sapphire substrate may be warped. In order to remove such warpage, a heat treatment step of heat-treating the sapphire substrate can be performed. The specific conditions of the heat treatment step are not particularly limited, but for example, heat treatment is preferably performed in a temperature range of 1200 ° C. to 1650 ° C., and heat treatment is performed in a temperature range of 1400 ° C. to 1600 ° C. Is more preferable. In addition, the atmosphere at this time is preferably performed in an air atmosphere or an oxygen atmosphere.

  The timing at which these optional steps described above are performed is not particularly limited, and can be performed at any timing.

  For example, the cutting process, the rough polishing process, the chamfering process, the intermediate polishing process, the heat treatment process, and the mirror polishing process can be performed in this order. Moreover, after finishing all the processes, a cleaning process for cleaning the sapphire substrate can be performed.

  Thus, an arbitrary process can be performed between, before and after the rough polishing process, the intermediate polishing process, and the mirror polishing process. In addition, the order which performs each above-mentioned process is an illustration, and can be implemented in arbitrary orders.

  According to the sapphire substrate manufacturing method of the present embodiment described above, after the rough polishing step and before the mirror polishing step, the intermediate polishing step can be performed under conditions that do not depend on the configuration of the work-affected layer. The manufacturing method of the sapphire substrate which can suppress the time of a process can be provided.

Specific examples and comparative examples will be described below, but the present invention is not limited to these examples.
[Example 1]
A sapphire ingot having a cylindrical shape with a diameter of 6 inches was cut into a wafer shape using a multi-wire saw device to form a sapphire substrate (cutting step). The crystal planes of the upper surface and the lower surface, which are main surfaces of the sapphire substrate, were r-planes.

  Subsequently, the obtained sapphire substrate was subjected to double-sided lapping with a free abrasive grain method (rough polishing step).

  The rough polishing process was performed using the double-side polishing apparatus shown in FIGS. A polishing pad is disposed on the surface of the upper surface plate 31 and the lower surface plate 32 facing the sapphire substrate 10, and silicon carbide slurry is supplied between the sapphire substrate 10 and the upper surface plate 31 and the lower surface plate 32. Polishing was performed. In the rough polishing step, the upper surface and the lower surface, which are the main surfaces of the sapphire substrate 10, were each polished by 70 μm.

  The sapphire substrate after the rough polishing step was subjected to double-sided lapping with a fixed abrasive method (intermediate polishing step).

  The intermediate polishing process was performed using the double-side polishing apparatus shown in FIGS. In addition, it grind | polished by arrange | positioning a grindstone in the surface facing the sapphire substrate 10 of the upper surface plate 31 and the lower surface plate 32. FIG. A grindstone containing diamond as a fixed abrasive was used as the grindstone.

In the intermediate polishing step, polishing was performed with a polishing load of 160 g / cm ² until 25 μm was polished from the start of polishing until the remaining machining allowance was 25 μm (high load polishing step).

Next, when the remaining amount of polishing became 25 μm, the polishing load was changed to 50 g / cm ² to perform polishing (low load polishing step).

  Therefore, in the intermediate polishing process, 50 μm polishing was performed in the high load polishing step and the low load polishing step.

  The sapphire substrate that had finished the intermediate polishing step was subjected to heat treatment (heat treatment step). The atmosphere during the heat treatment step was an air atmosphere.

  Next, mirror polishing was performed on one main surface of the sapphire substrate (mirror polishing step).

  In the mirror polishing step, polishing was performed by a free abrasive grain method, and colloidal silica was used as a polishing liquid.

In the mirror polishing process, when the mirror surface polishing was advanced while observing the residual processed damaged layer on the polished surface with a laser microscope, it was confirmed that the processed damaged layer disappeared when the polishing amount was 20 μm. It took 7 hours to remove the work-affected layer and complete the mirror polishing process.
[Example 2]
A sapphire substrate was produced by the same procedure and conditions as in Example 1 except that the polishing load in the low load polishing step was 30 g / cm ² .

In the mirror polishing step, it was confirmed that the work-affected layer disappeared when the polishing amount was 20 μm. It took 7 hours to remove the work-affected layer and complete the mirror polishing process.
[Example 3]
In the intermediate polishing step, polishing was carried out at a polishing load of 160 g / cm ² until the remaining polishing margin was 30 μm (high load polishing step).

Next, polishing was performed with a polishing load of 50 g / cm ² when the remaining polishing margin became 30 μm (low load polishing step).

  A sapphire substrate was manufactured according to the same procedure and conditions as in Example 1 except for the above two points.

In the mirror polishing step, it was confirmed that the work-affected layer disappeared when the polishing amount was 17 μm. It took 7 hours to remove the work-affected layer and complete the mirror polishing process.
[Example 4]
A sapphire substrate was produced by the same procedure and conditions as in Example 1 except that the polishing load at the high load polishing step was 200 g / cm ² and the polishing load at the low load polishing step was 50 g / cm ² .

In the mirror polishing step, the work-affected layer disappeared when the polishing amount was 20 μm. It took 7 hours to remove the work-affected layer and complete the mirror polishing process.
[Comparative Example 1]
In the intermediate polishing step, polishing is performed with a polishing load of 160 g / cm ² from the start of polishing to 50 μm polishing (high load polishing step). A sapphire substrate was manufactured by the same procedure and conditions as in Example 1 except that the low-load polishing step was not performed.

In the mirror polishing step, it was confirmed that the work-affected layer disappeared when the polishing amount was 45 μm. It took 15 hours to remove the work-affected layer and complete the mirror polishing process.
[Comparative Example 2]
In the intermediate polishing step, polishing was performed at a polishing load of 160 g / cm ² from the start of polishing until polishing by 40 μm (high load polishing step).

Next, polishing was performed with a polishing load of 50 g / cm ² when the remaining polishing margin became 10 μm (low load polishing step).

  A sapphire substrate was manufactured according to the same procedure and conditions as in Example 1 except for the above two points.

  In the mirror polishing step, it was confirmed that the work-affected layer disappeared when the polishing amount was 35 μm. It took 12 hours to remove the work-affected layer and complete the mirror polishing process.

From the above results, after the rough polishing step and before the mirror polishing step, the remaining polishing allowance of the intermediate polishing step is 25 μm or more until the intermediate polishing step is completed with a polishing load of 50 g / cm ² or less. It was confirmed that the generation of a work-affected layer in the intermediate polishing process can be suppressed by performing a low-load polishing step for polishing. Moreover, it was confirmed that the intermediate polishing step can be carried out under conditions that do not depend on the layer structure of the work-affected layer as described above.

10 Sapphire substrate

Claims (2)

A rough polishing step of rough polishing the main surface of the sapphire substrate whose main surface crystal surface is an r-plane;
After the rough polishing step, an intermediate polishing step of polishing the main surface of the sapphire substrate with diamond fixed abrasive,
After the intermediate polishing step, having a mirror polishing step for mirror polishing the main surface of the sapphire substrate,
The intermediate polishing step includes a low load polishing step in which polishing is performed with a polishing load of 50 g / cm ² or less when the main surface of the sapphire substrate is mirror-polished.
The low-load polishing step is a method for manufacturing a sapphire substrate that is started when the remaining machining allowance in the intermediate polishing step is 25 μm or more and is continued until the intermediate polishing step is completed. The intermediate polishing step has a high load polishing step of polishing with a polishing load of 160 g / cm ² or more when polishing the main surface of the sapphire substrate,
The method for manufacturing a sapphire substrate according to claim 1, wherein the low-load polishing step is executed after the high-load polishing step is completed.

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