JP2004299018A - SUPER-SMOOTH CRYSTAL FACE FORMING METHOD BY POLISHING OF SiC SINGLE CRYSTAL SUBSTRATE OR THE LIKE - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that the characteristic required in the device forming on the surface or growth of a single crystal film can not be obtained because the crystal surface is not obtained, in the material where the crystal surface cannot sufficiently be obtained by the thermal, chemical and mechanical surface treatment. <P>SOLUTION: In this super-smooth crystal face forming method for a single crystal substrate, a single crystal substrate consisting of SiC, nitrides and oxides of group III or a dielectric body to be polished derivative with a rotary buff polishing method or an ultrasonic vibration polishing method, by using an alkaline aqueous polishing liquid adjusted to pH7 to 10, containing 5 to 40 wt.% of colloidal silica to water to peel off the defective layer whose crystallinity of the surface part is not single crystal, to form a super smooth crystal face consisting of the interface of a crystalline part and a defective layer part. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for forming an ultra-smooth crystal face by polishing a hard single crystal material that is difficult to perform chemical polishing or mechanical polishing.
[0002]
[Prior art]
A semiconductor wafer is usually manufactured by cutting a columnar semiconductor single crystal block into a wafer of a predetermined thickness using a diamond saw or the like, but a damaged layer including micro cracks and dislocations is generated on the cut surface. Therefore, a series of finishing processes such as (1) chamfering, (2) double-sided lapping, (3) chemical polishing, (4) polishing, (5) cleaning, etc., are performed, and a flattened surface is formed without a damaged layer or unevenness on the wafer surface. A high degree mirror surface is formed. Polishing is also performed to remove the insulating oxide film and the metal film on the surface of the semiconductor substrate.
[0003]
In the case of an insulating oxide film such as Si or a II-VI compound semiconductor crystal material, SiO ₂ or the like, as the polishing step, an alkaline aqueous polishing slurry in which colloidal silica is dispersed is applied to a polishing pad such as a rotary single-side polishing apparatus and a workpiece. And a method of performing chemical mechanical polishing (CMP) while supplying between them (Patent Documents 1 to 6).
[0004]
However, SiC is a chemically stable and non-reactive substance far more chemically than Si, is a hard material next to diamond, and is difficult to polish by a CMP method using colloidal silica similar to a Si crystal substrate. For example, a method of polishing using diamond abrasive grains has been adopted (Patent Documents 7 and 8). In addition, a group III nitride represented by GaN, which is a hard material, has also been preferably polished using diamond abrasive grains (Patent Document 9).
[0005]
Instead of the chemical mechanical method, a chemical vaporization method using plasma has been developed in order to remove a residual defect such as a work-affected layer on the surface of a SiC single crystal (Patent Document 10). Patent Document 10 discloses, as examples of a conventional method for removing residual defects on the surface of a SiC single crystal wafer, a liquid etching method using a high-temperature molten salt such as potassium hydroxide, a high-concentration potassium hydroxide aqueous solution and chromium. An anodic etching method using an acid or oxalic acid as an electrolyte and a method of oxidizing the surface and subsequently removing the oxidized portion are exemplified. In addition, as a method for planarizing a SiC crystal substrate, a mechanochemical polishing method using chromium oxide as free abrasive grains has been developed (Patent Documents 11 and 12).
[0006]
[Patent Document 1]
Japanese Patent Publication No. Hei 7-12590 [Patent Document 2]
JP-A-10-308379 [Patent Document 3]
JP-A-11-31675 [Patent Document 4]
Japanese Patent No. 3099002 [Patent Document 5]
JP 2001-7063 A [Patent Document 6]
JP 2001-9078 A [Patent Document 7]
JP-A-8-323604 [Patent Document 8]
JP-A-11-188610 [Patent Document 9]
JP 2001-322899 A [Patent Document 10]
Japanese Unexamined Patent Publication No. 5-500883 (Patent No. 2771697) [Patent Document 11]
JP-A-7-80770 [Patent Document 12]
JP 2001-205555 A
[Problems to be solved by the invention]
Semiconductor devices are often formed on epitaxial thin films grown on bulk substrates. This is because the VLSI requires a layer that incorporates an electrically active element that is controlled with higher precision. In order to lower the voltage and increase the speed of the operation of electronic devices, which are required at present, it is necessary to control the electrically active elements and to make the crystal structure uniform from the viewpoint of the charge carrier. In addition, since the portion used as a device is a region of several hundred nanometers or less from the surface, control of the crystal structure near the surface is a key point that affects device characteristics.
[0008]
Epitaxial films are fabricated on highly planarized substrate surfaces. The flattening may be performed on a crystal low index plane or on a plane having an off angle of several degrees in order to promote lattice plane growth. In any case, non-uniform polishing results in local oxidized regions and disordered crystal structure at the epitaxial growth interface. From these locations, microscopic defects grow in the epitaxial film, which causes problems such as a decrease in carrier mobility and a hindrance to high-speed device operation due to space charge.
[0009]
In addition, after the device is formed, a defect grows from these points during device operation and the device is destroyed. The miniaturization of the area on a substrate occupied by one device has been permitted, and a defect per atomic step, which has been conventionally allowed, has appeared as an “electronic defect”.
[0010]
The major difference between the SiC semiconductor device fabrication process and the Si semiconductor device fabrication process is that the temperature of the epitaxial growth or ion implantation process exceeds 1500 ° C., and the atom transfer on the outermost surface starts to occur. Atomic movement occurs due to micro lattice distortion, unevenness, and the like, and generates an uneven surface called step bunching, which is recrystallized and grown stepwise. In addition, since the carrier mobility has a large dependence on the crystal orientation and the epitaxial growth mode has a large dependence on the crystal orientation, it may be necessary to obtain various crystal planes.
[0011]
Further, the SiC semiconductor is a compound composed of two types of elements in which the atomic radii of Si and C are greatly different, and C clusters and the like grow near the surface to form an electronic level and reduce the operation speed of the MOS device. Such as physical properties. In addition, the expected device operating temperature of the SiC semiconductor is around 500 ° C. or higher, the reverse breakdown voltage is a high voltage of several thousand volts, and the forward current is several hundred amps / □. Used in an environment where defects are likely to occur during operation. From these facts, it is needless to say that the SiC semiconductor substrate is not only flat but also has few crystal defects.
[0012]
In the polishing method for flattening the surface of the SiC semiconductor at the atomic radius level using hard abrasive grains such as diamond as described in the above-mentioned conventional technique, the crystal structure near the surface layer of the polished surface is broken or crystallized by polishing stress. And a non-crystalline layer is formed. Further, in polishing with hard abrasive grains, a cutting mark having a depth exceeding 10 nm is generated during polishing, and a non-crystalline layer is generated around the cutting mark.
[0013]
The same applies to chemical catalytic polishing methods such as chromium oxide and titanium oxide as chemical methods for removing a non-crystalline layer, and in these chemical methods, a metal element by an abrasive is chemically applied to a polished surface. Bonding and persistence causes surface metal contamination.
[0014]
As described above, SiC, a group III nitride semiconductor single crystal, which cannot sufficiently obtain a crystalline surface by thermal, chemical, and mechanical surface treatment, barium titanate, barium niobate, tellurium dioxide, molybdic acid A single-crystal substrate such as an oxide single crystal for an optical material such as lead or a single-crystal substrate such as a dielectric ceramic cannot be obtained by polishing, so a device is formed on the surface, and a single crystal substrate is formed on the surface. The desired characteristics required in the growth of a single crystal film were not obtained.
[0015]
According to the present invention, it is possible to obtain a single-crystal substrate having a single-crystal surface having no electrical problem by using a polishing process by using a polishing process. It is an object of the present invention to provide a surface treatment method capable of measuring a thickness of 1 nm or less by an AFM method.
[0016]
Further, a problem has arisen regarding the crystallinity near the outermost surface of the epitaxial film. "Polishing" an epitaxially grown film has not previously been considered. This seems to be due to the consciousness of contamination due to the polishing action, but mainly due to the assumption that the epitaxial film has excellent crystallinity.
[0017]
At the end of the epitaxial growth for forming the surface, the supply of atoms is disturbed, which causes several layers of structural disorder. In evaluations focusing only on the flatness of the outermost surface, such as AFM, a flatness having only one layer of irregularities is obtained. However, when the crystal structure is evaluated, there is an epitaxial film in which several layers are amorphous. Simply examining only the flatness, such as AFM, is not sufficient as a method for inspecting the surface of an electronic device substrate. Such a problem has become remarkable because slight lattice distortion has been miniaturized in a MOS transistor structure using a crystal surface to such an extent that characteristics are affected.
[0018]
Therefore, in addition to evaluating the lattice arrangement of several layers, it is also important to fabricate a Schottky electrode and evaluate its characteristics. As the device size cannot ignore the surface structure of the epitaxial film, in addition to the flatness evaluation, the crystal structure evaluation of several layers on the surface and the electronic defect evaluation are evaluated as "Surface microfabrication". Is required.
[0019]
[Means for Solving the Problems]
The present inventor has made use of the synergistic action of colloidal silica and an alkaline solution without using hard abrasive grains such as diamond and silicon carbide powder and chemical catalyst materials conventionally used for polishing hard materials. It has been found that a crystal layer on the surface of a SiC or group III nitride single crystal substrate, which has been considered extremely difficult to polish, can efficiently remove a defect layer that is not a single crystal to form an ultra-smooth crystal plane.
In addition, this method is used to remove a defect layer on the surface of a single crystal substrate made of an oxide or a dielectric or to remove an epitaxial film made of SiC, a group III nitride, an oxide or a dielectric formed on a single crystal substrate. It has been found that the method can be applied to the removal of a defect layer on the surface.
[0020]
That is, the present invention provides (1) a rotary buff polishing method or an ultrasonic vibration polishing method using an alkaline aqueous polishing liquid containing 5 to 40% by weight of colloidal silica with respect to water and adjusting the pH to 7 to 10. Polishing a single-crystal substrate made of SiC, group III nitride, oxide, or dielectric to remove a defect layer having a surface portion that is not single-crystal, thereby removing a boundary between the crystalline portion and the defect layer portion. A method for forming an ultra-smooth crystal surface of a single crystal substrate, comprising forming an ultra-smooth surface comprising a surface.
Further, the present invention provides (2) a defect layer having non-single-crystallinity due to an existing layer on a single-crystal substrate, a layer generated during pre-stage rough polishing of a single-crystal substrate, or a high-temperature process strain exceeding 500 ° C. (1) The method for forming an ultra-smooth crystal plane of a single crystal substrate according to the above (1), wherein the layer is formed on the single crystal substrate.
Further, according to the present invention, (3) the defect layer whose crystallinity is not a single crystal is a layer having a depth of 100 nm introduced into the semiconductor single crystal substrate by ion implantation, and the surface of the defect layer is removed by the removal of the defect layer. (1) The method for forming an ultra-smooth crystal surface of a single crystal substrate according to the above (1), wherein the uneven structure is selectively produced.
[0021]
Further, the present invention provides (4) a rotary buff polishing method or an ultrasonic vibration polishing method using an alkaline aqueous polishing liquid containing 5 to 40% by weight of colloidal silica with respect to water and adjusting the pH to 7 to 10. By polishing an epitaxial film made of SiC, group III nitride, oxide, or dielectric formed on a single crystal substrate by the above method, a defect layer in which the crystallinity of the surface portion is not a single crystal is peeled off to remove the crystalline portion Forming an ultra-smooth surface comprising a boundary surface between a semiconductor layer and a defect layer portion.
Also, in the present invention, (5) the alkaline aqueous polishing liquid has a polishing capability in which the removal rate of the defective layer by polishing is at least 10 times faster than the removal rate of the crystalline portion by polishing. ) To (4).
Further, the present invention is (6) the method for forming an ultra-smooth crystal surface according to any one of the above (1) to (5), wherein the polished surface is polished without being exposed to the atmosphere.
In the present invention, (7) the ultra-smooth surface has an unevenness of 1 nm or less as measured by a Wyko method (optical surface roughness measuring device) and an AFM method. Any one of the methods for forming an ultra-smooth crystal face.
[0022]
[Action]
SiC is a material that is said to be the hardest next to diamond, and has a very strong bond between Si and C. However, a defect layer having a non-single crystallinity has a broken bond. When the alkaline aqueous polishing liquid of the present invention is used, the colloidal silica silica fine particles dispersed in the polishing liquid selectively attack the portion where the defect region is present, and the carbon atom whose bond with the oxygen atom of the silica is broken is chemically converted. It is presumed that the reaction is repeatedly performed in which the silicon is chemically bonded, vaporized and desorbed, and then the remaining silicon is dissolved in colloidal silica and desorbed.
[0023]
In order to efficiently promote such a reaction, the alkaline aqueous polishing liquid desirably contains about 5 to 40% by weight of colloidal silica based on water. If the content of colloidal silica is less than about 5% by weight, polishing cannot be performed. If the content exceeds about 40% by weight, colloidal silica aggregates to increase the particle size, which is not preferable because the polished surface is damaged. More preferably, it is about 5 to 15% by weight. The average particle size of the colloidal silica is 0.5 μm or less, more preferably 0.1 μm or less. When the particle size is larger than 0.5 μm, the polished surface becomes rough.
[0024]
NaOH and KOH in the alkaline aqueous polishing liquid have an effect of etching a defect layer whose crystallinity is not a single crystal. Colloidal silica selectively polishes a portion having a defect region. In the case of NaOH or KOH, in addition to that, a single crystal portion is also etched away at a low speed. Since this effect is stronger in NaOH than in KOH, KOH is more preferable. When the concentration of NaOH or KOH is high, the polishing is not terminated in the single crystal region, the polishing proceeds one after another, and the single crystal portion is also cut. Therefore, the pH needs to be adjusted to 10 or less.
[0025]
By setting the colloidal silica and the alkaline solution under such conditions, the removal rate of the defective layer by polishing can be at least ten times faster than the removal rate of the crystalline portion by polishing due to the synergistic action of both. As described above, when the degree of alkali is small, while the crystal defects are actively removed, the polishing rate is as fast as about 100 nm to 300 nm / 10 minutes, but the polishing rate is rapidly reduced to 1/100 at the time of hitting the single crystal portion. Since it is reduced to about 1/10, it is convenient to maintain crystallinity and obtain a smooth surface.
[0026]
Therefore, even if the polishing time is not strictly determined in advance for the sample, when the crystalline surface comes out, the polishing is changed to slow polishing. Therefore, polishing stops at a clear interface between the defect layer and the crystal layer, so that only the defect layer can be selectively peeled off, and the unevenness at the interface between the crystal layer and the defect layer is on the order of several nanometers. Since the surface does not spread to several tens of nanometers, an ultra-smooth surface of several nanometers can be obtained by polishing this interface.
[0027]
In the case of a semiconductor single crystal made of a group III nitride such as GaN, an oxide single crystal for an optical material such as barium titanate, barium niobate, tellurium dioxide, lead molybdate, or a single crystal material such as a dielectric ceramic. When the polishing liquid of the present invention is used, the polishing rate of the defective layer is extremely high, and only the region of the defective layer is polished, and the same effect as the polishing of SiC can be obtained.
[0028]
Further, after introducing a defect layer having a depth of 100 nm level by a method capable of positively introducing a defect layer having irregularities such as ion implantation, a 100 nm level irregular structure was selectively formed on the surface by removing the defect layer. However, the boundary surface between the defect layer and the crystal layer can form an ultra-smooth surface having irregularities of several nanometers or less by this method.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
An example in which a semiconductor single crystal substrate is polished by a rotary buff polishing method according to the method of the present invention will be described with reference to FIGS. FIG. 1A is a cross-sectional view showing a state in which a semiconductor single crystal is bonded and fixed to a jig for fixing the semiconductor single crystal, and FIG. 1B is a bottom view thereof. FIG. 2 is a cross-sectional view showing an arrangement relationship between a colloidal silica-dispersed alkaline aqueous solution during polishing and a jig, a polishing table, and a polishing cloth used for polishing.
[0030]
The semiconductor single crystal 1 to be polished is fixed to the lower surface of the disk 3 at the lower end of the fixing jig 2 by using an adhesive and uniformly spaced at appropriate intervals. The fixing jig 2 is supported in the vertical through hole of the horizontal polishing jig 4 so that the polishing surface of the semiconductor single crystal 1 always keeps horizontal, and the fixing jig 2 and the horizontal polishing jig 4 rotate smoothly with each other. Try to do each other. The fixing jig 2 and the horizontal polishing jig 4 are made of metal or ceramics.
[0031]
A non-metallic material 5, for example, a crystalline substrate or a Si substrate of the same type as the semiconductor single crystal 1 is bonded to several places on the lower surface of the end of the horizontal polishing jig 4. When a metal material is used in place of the nonmetallic material 5, when metal atoms and colloidal silica are under pressure, silica particles aggregate while taking in metal ions, forming hard large particles. This is unsuitable because it even scrapes the crystal plane.
[0032]
The colloidal silica-dispersed alkaline aqueous polishing liquid 6 is stored on the rotary polishing table 7 by the edge 8 of the rotary polishing table 7. It is preferable that the semiconductor single crystal 1 is always immersed in the colloidal silica-dispersed alkaline aqueous polishing liquid because the air does not come into contact with the semiconductor single crystal 1 and the polishing surface suppresses the incorporation of oxygen from the atmosphere. . When the polished surface comes into contact with the atmosphere, colloidal silica aggregates on the polished surface, and the particle size of the silica increases. Therefore, an inert gas atmosphere such as an argon gas may be used.
[0033]
A polishing buff 9 is arranged on the rotary polishing table 7, and the surface of the semiconductor single crystal 1 is rotationally polished by the polishing buff 9. As the polishing buff 9, a urethane foam, a polyester fiber non-woven fabric, artificial leather, a polyester fiber non-woven fabric and a polyurethane foam laminated structure can be used. The polishing is preferably performed by a rotary polishing method using a polishing buff, with the polishing surface pressure set to about 1.4 kg / cm ² or less and the relative sliding speed of the polishing surface set to about 1 m / min or less.
[0034]
The substrate 5 adhered to several positions on the lower surface of the end portion of the horizontal polishing jig 4 touches the polishing buff, but this portion is not a metal but a crystalline substrate or a Si substrate of the same type as the semiconductor single crystal 1. In the case of a metal, it is polished to form metal particles, which are used as nuclei to prevent silica from agglomerating and silica abrasive grains from being enlarged. Such agglomerated silica is extremely hard and causes defects (breaking the crystal lattice) in the polished surface, so that it is important to prevent this.
[0035]
As described above, the rotary polishing method using a polishing buff has been described as a specific example. However, the method of the present invention employs the above-mentioned specific alkaline aqueous polishing liquid, and the surface to be polished has a synergistic polishing action of colloidal silica and an alkaline liquid. The same effect can be obtained by a method using a hard plate instead of a buff, an ultrasonic vibration polishing method, or the like.
[0036]
【Example】
Example 1
An abrasive stock solution prepared by adding 50% by weight of colloidal silica having a particle size of 0.1 μm to ion-exchanged pure water (formulated by Fujimi Incorporated) is diluted with ion-exchanged pure water to 30% by weight of colloidal silica. And KOH to prepare a polishing solution having a pH of 8. Using a polishing apparatus as shown in FIG. 1 and FIG. 2, (0001) plane, (1120) plane, and (1100) plane are cut out, and silicon carbide of # 400 to # 3000, alumina of 1 micron particle diameter, A 1 cm square, 0.3 mm thick SiC single crystal wrapped with a diamond abrasive having a particle size of 0.5 micron was polished.
[0037]
A duralumin platen was used, and a polishing pad was a polyurethane pad TD87 manufactured by Poval Kogyo Co., Ltd. The temperature of the polishing liquid was kept below 50 ° C. The depth of the polishing liquid is 8 mm. The polishing pressure was 1.4 kg / cm ² , and the rotation speed of the polishing table was 80 cm / s. The polished surface of SiC was a (0001) plane, and the polishing time was 10 minutes. Under these conditions, the amorphous SiC layer having a thickness of 100 nm was peeled off by polishing. The surface smoothness at this time was 0.6 nm in RMS value.
[0038]
Example 2
An abrasive stock solution prepared by adding 50% by weight of colloidal silica having a particle size of 0.1 μm to ion-exchanged pure water (formulated by Fujimi Incorporated) is diluted with ion-exchanged pure water to 20% by weight of colloidal silica. And KOH to prepare a polishing solution having a pH of 8. Using a polishing apparatus as shown in FIGS. 1 and 2, the surface of a (0001) plane GaN having a thickness of 3 μm and grown on sapphire was polished.
[0039]
A duralumin platen was used, and a polishing pad was a polyurethane pad TD87 manufactured by Poval Kogyo Co., Ltd. The temperature of the polishing liquid was kept below 50 ° C. The depth of the polishing liquid is 8 mm. The polishing pressure was 0.6 kg / cm ² , and the rotation speed of the polishing table was 50 cm / s. Under these conditions, the surface before polishing having an RMS value of 3 nm became 2 nm after polishing.
[0040]
AFM Image of Polished SiC Semiconductor Single Crystal Surface FIG. 3 shows a surface AFM image of a 4H—SiC crystalline substrate after colloidal silica polishing. Many steps of about 0.8 nm are observed. This is equal to the lattice constant of the 4H—SiC single crystal, indicating that a single crystal surface has been obtained. A region where no crystal lattice step is observed indicates flatness exceeding the resolution of the AFM device.
[0041]
CAICISS (CoAxial Impact Collision Ion Scattering Spectrometer) Measurement Results of Polished SiC Semiconductor Single Crystal Surface FIG. 4 shows that the surface of the 6H-SiC crystalline substrate washed with hydrofluoric acid (HF) after colloidal silica polishing was washed with CAICISS. The result of evaluating the crystal structure using (direct collision ion scattering method) is shown. An ion beam is incident at an angle of 14 degrees from the surface, and the structure of three atomic layers from the surface is evaluated. Analysis of the signal shown in FIG. 4 from the known crystal structure of SiC revealed that Si atoms were arranged in a {3X} 3 structure on the resurface of the SiC single crystal.
[0042]
That is, it was found that the SiC semiconductor substrate polished by the method of the present invention was crystalline up to the outermost surface. In FIG. 4, the crystallinity at the center is evaluated by the inner of the 1-inch substrate, and the crystallinity at the outer periphery is evaluated by the outer. Outer has a lower peak and is broader than inner. This is not due to polishing, but depends on the quality of commercially available crystalline substrates.
[0043]
Furthermore, it was clarified that the crystal structure was maintained from the surface layer, and that no zinc element was adsorbed from the zinc platen during rough cutting on the outermost surface after polishing. Although the CAICISS measurement is performed after the diamond polishing, no change in the scattering intensity of the Δe atoms due to the periodicity of the crystal structure on the outermost surface as shown in FIG. 1 is observed after the diamond polishing. It has been found that colloidal silica polishing can remove a tens of nanometer damaged layer caused by diamond polishing without introducing a damaged layer.
[0044]
Electrical evaluation of metal-semiconductor contact formed on the surface of the polished SiC semiconductor single crystal Ni was deposited on the polished n-type SiC surface (Si surface) and the back surface to form electrodes. The back surface was subjected to pulsed laser irradiation to form an ohmic electrode. FIG. 5 shows the current-voltage characteristics of the polished surface Schottky electrode. The relationship between the current I and the voltage V of the Schottky electrode is expressed as I = A _exp qV / nκT where q, κ, T, and A are elementary charge, Boltzmann constant, absolute temperature, and Richardson constant, respectively. .
[0045]
After the polished surface is cleaned with hydrogen fluoride and a metal is deposited to produce a Schottky device, the value of a constant n (a gradient of a current with respect to a forward voltage in FIG. 5) = 1.1 or less is idealized by the ideal factor. Obtained. This value changes extremely sensitively to the state of the metal-semiconductor interface, that is, the state of the electrode deposition surface. If the current transport between the metal and the semiconductor is ideally performed, the constant n is 1. When there is a defect, the value becomes 1.2 or more. In FIG. 5, the electrodes shown by solid lines and wavy lines are characteristics of the electrodes manufactured on the same polished surface.
[0046]
【The invention's effect】
According to the method of the present invention, it is possible to obtain a single crystal electrically non-problematic surface up to the outermost surface layer by utilizing polishing processing on a semiconductor single crystal substrate. (Optical Surface Profile Roughness Measuring Apparatus) and an ultra-smooth surface of 1 nm or less as measured by the AFM method can be formed.
[Brief description of the drawings]
FIG. 1 is a sectional view (A) and a bottom view (B) showing an example of a relationship between a jig used for polishing and a semiconductor single crystal substrate to be polished when carrying out a method of the present invention. .
FIG. 2 is a cross-sectional view showing an arrangement relationship between a colloidal silica-dispersed alkaline aqueous polishing liquid during polishing and a jig, a polishing table, and a polishing cloth used for polishing.
FIG. 3 is a drawing substitute photograph showing an AFM image of a polished SiC semiconductor single crystal surface in Example 1.
FIG. 4 is a graph showing the results of CAICISS measurement of the polished SiC semiconductor single crystal surface in Example 1.
FIG. 5 is a graph showing Schottky characteristics of a metal electrode formed on the surface of a SiC semiconductor single crystal after polishing in Example 1.

Claims (7)

Using an alkaline aqueous polishing liquid containing 5 to 40% by weight of colloidal silica with respect to water and adjusting the pH to 7 to 10 by a rotary buff polishing method or an ultrasonic vibration polishing method, SiC, group III nitride, oxide A single crystal substrate made of a material or a dielectric is polished to remove a defect layer in which the crystallinity of the surface portion is not a single crystal, thereby forming an ultra-smooth surface including a boundary surface between the crystalline portion and the defect layer portion. A method for forming an ultra-smooth crystal face of a single crystal substrate, characterized in that: The defect layer whose crystallinity is not a single crystal is an existing layer on the single crystal substrate, a layer generated during the preliminary rough polishing of the single crystal substrate, or a layer generated on the single crystal substrate due to high temperature process strain exceeding 500 ° C. 2. The method for forming an ultra-smooth crystal plane of a single crystal substrate according to claim 1, wherein: The defect layer whose crystallinity is not a single crystal is a layer having a depth of 100 nm introduced into a semiconductor single crystal substrate by ion implantation, and a concave-convex structure of 100 nm level is selectively formed on the surface by removing the defect layer. 2. The method for forming an ultra-smooth crystal plane of a single crystal substrate according to claim 1, wherein: It was formed on a single crystal substrate by a rotary buff polishing method or an ultrasonic vibration polishing method using an alkaline aqueous polishing solution containing 5 to 40% by weight of colloidal silica with respect to water and adjusting the pH to 7 to 10. By polishing an epitaxial film made of SiC, a group III nitride, an oxide, or a dielectric, a defect layer whose surface portion is not a single crystal is peeled off and a boundary surface between the crystalline portion and the defect layer portion is removed. A method for forming an ultra-smooth crystal plane of an epitaxial film, characterized by forming an ultra-smooth plane comprising: 5. The ultra-smooth crystal surface forming method according to claim 1, wherein said alkaline aqueous polishing liquid has a polishing ability at which the removal rate of said defective layer by polishing is at least 10 times faster than that of said crystalline portion by polishing. Method. The method for forming an ultra-smooth crystal surface according to any one of claims 1 to 5, wherein the polished surface is polished without being exposed to the atmosphere. The method for forming an ultra-smooth crystal surface according to any one of claims 1 to 6, wherein the ultra-smooth surface has an unevenness of 1 nm or less as measured by a Wyko method (optical surface profile roughness measuring device) and an AFM method. .

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