Polishing agents, composite semiconductor manufacturing processes and semiconductor device manufacturing processes

Abstract

Polishing agent for Gaαln(1-α)AsβP(1-β) compound semiconductors (where 0 ≤ α ≤ 1; 0 ≤ β ≤ 1), wherein the polishing agent contains: a carbonate of an alkali metal; an organic salt of an alkali metal; a chlorine-based oxidizing agent; and a phosphate of an alkali metal; wherein the sum of the concentrations of the carbonate of an alkali metal and the organic salt of an alkali metal is between 0.01 mol / l and inclusive of 0.02 mol / l, the organic salt of an alkali metal is sodium dicarboxylate, the sodium dicarboxylate is at least a substance selectable from the group consisting of sodium tartrate, sodium malate and sodium succinate, and the polishing agent is free of abrasive grains.

Description

Technical FieldThe present invention relates to polishing agents, methods for manufacturing a compound semiconductor, and methods for manufacturing semiconductor devices, and more particularly relates to polishing agents for a GaαIn(1-α)AsβP(1-β) compound semiconductor (where 0≤α≤1; 0≤β≤1), and compound semiconductor manufacturing methods and semiconductor device manufacturing methods using the agents.Underlying State of the ArtGaαIn(1-α)AsβP(1-β) compound semiconductors (where 0≤α≤1; 0≤β≤1) (GaαIn(1-α)AsβP(1-β) hereinafter also referred to as "GalnAsP", gallium indium arsenide phosphide) are further used as substrates for growing epitaxial layers that constitute semiconductor microelectronic devices such as semiconductor lasers, LEDs (light emitting diodes), and high-speed circuit elements. The substrates are polished before the epitaxial layers are formed. Examples of polishing agents used in such polishing are described in Japanese Patent No. JP 3 147 168 B2 (Patent Document 1), Japanese Unexamined Patent Application Publication No. JP 2004-327 614 A (Patent Document 2), Japanese Unexamined Patent Application Publication JP 2008-300 422 A, and elsewhere.The above-mentioned Patent Document 1 discloses a polishing agent containing chlorinated isocyanuric acid, an alkali metal sulfate, an alkali metal phosphate and a carbonate of an alkali metal. The above-mentioned Patent Document 2 discloses a polishing agent consisting of silica, sodium dichloroisocyanurate, sodium sulfate, sodium tripolyphosphate, sodium carbonate and citric acid. The above-mentioned Patent Document 3 discloses the use of a chlorine-based oxidizing agent in a first polishing step and the use of an inorganic former consisting of, among others, sodium carbonate and sodium tripolyphosphate in a subsequent second polishing step.US 2007 / 007 5041 A1 discloses polishing agents for compound semiconductors for chemical mechanical polishing, wherein malic acid is contained as the acid component on the one hand in one embodiment and sodium carbonate Na 2 CO 3 is contained instead of this in another embodiment.Literature DirectoryPatent LiteraturePatent Document 1: Japanese Patent No. JP 3 147 168 B2Patent Document 2: Japanese Unexamined Patent Application Publication No. JP 2004-327 614 APatent Document 3:Japanese Unexamined Patent Application Publication No. JP 2008-300 422 AOverview of the InventionTechnical ProblemThe polishing methods using the polishing agents of the above-mentioned Patent Documents 1 to 3 employ a chemical polishing process which, while oxidizing the substrate surface, simultaneously removes the oxidation layer. In this process, sufficient control of the action of the polishing agent presents difficulties. When the oxidizing performance of the polishing agent increases too much, the "haze" (micro roughness of the surface) on the substrate surface increases, while when its alkalinity becomes too strong, LPDs (light spot defects) in the substrate surface increase. On the other hand, if the chemical effect is too weak, the mechanical effect becomes relatively stronger, so that scratches, micro roughness, and the like on the substrate surface increase. Further, if the chemical effect is too weak, the polishing rate (polishing rate) decreases.The fact that avoiding the deterioration of the surface quality of a compound semiconductor after polishing and at the same time improving the polishing rate have become important tasks is due to the fact that the interaction of the chemical components constituting the polishing agent is still to be illuminated. As a result of extensive research efforts, the present inventors have arrived at the present invention by finding that the chemical composition of the polishing agent is essential for achieving the above-discussed important objects and by further discovering compositions that are most suitable for making the solution of these two important objects possible.That is, an object of the present invention is to provide a polishing agent and a compound semiconductor manufacturing method and a semiconductor device manufacturing method using the agent, thereby advantageously maintaining the surface quality of compound semiconductor substrates after polishing and at the same time enabling polishing at a high polishing rate.Solution of the ProblemA polishing agent of the present invention is a polishing agent for GaαIn(1-α)Asβ(1-β) compound semiconductors (wherein 0≤α≤1; 0≤β≤1), and contains a carbonate of an alkali metal, an organic salt of an alkali metal, i.e., a salt of an alkali metal of an organic acid, a chlorine-based oxidizing agent, and a phosphate of an alkali metal, the sum of the concentrations of the carbonate of the alkali metal and the organic salt of the alkali metal being between 0.01 mol / L and 0.02 mol / L, inclusive. In the aforementioned polishing agent, the organic salt of an alkali metal is a sodium dicarboxylate. The sodium dicarboxylate is at least one substance selected from the group consisting of sodium tartrate, sodium malate and sodium succinate. Furthermore, the polishing agent is free of abrasive grains.Polishing GalnAsP compound semiconductor surfaces using a polishing agent of the present invention reduces surface haze (micro roughness of the surface), LPDs (light spot defects), and the like. And since the chemical effect of a polishing agent of the present invention does not become excessively weak, scratching and micro-roughness can be reduced. Thus, polishing GalnAsP compound semiconductor surfaces using a polishing agent of the present invention allows the surface quality to be maintained advantageously. In addition, polishing GalnAsP compound semiconductor surfaces using a polishing agent of the present invention makes it possible to prevent the polishing rate from decreasing. Accordingly, with the aid of a polishing agent of the present invention, an advantageous quality of the compound semiconductor surfaces can be maintained and, in addition, high polishing rates can be maintained. Sodium dicarboxylate, which is at least one substance selected from the group consisting of sodium tartrate, sodium malate and sodium succinate, has advantages in polishing properties, stability and cost. Since the polishing agent is free of abrasive grains, the surface quality is improved. Namely, this weakens scratching, roughness and the like.In the aforementioned polishing agent, the carbonate of an alkali metal is preferably sodium carbonate. In this case, the concentration of the sodium carbonate in the polishing agent is preferably between 0.008 mol / L and 0.018 mol / L inclusive.Further, at a sodium carbonate concentration of not less than 0.008 mol / L, an increase in turbidity can be controlled to a minimum, and further, when the concentration of sodium carbonate is not more than 0.018 mol / L, the increase in LPDs can be controlled to a minimum.In the aforementioned polishing agent, the chlorine-based oxidizing agent is preferably sodium dichloroisocyanurate. In this case, the concentration of the sodium dichloroisocyanurate in the polishing agent is preferably between 0.035 mol / L and 0.060 mol / L inclusive.At a concentration of sodium dichloroisocyanurate of not less than 0.035 mol / l, a decrease in polishing rate can be further controlled. When the concentration of sodium dichloroisocyanurate is not more than 0.060 mol / l, an increase in turbidity can be further controlled.In the aforementioned polishing agent, the alkali metal phosphate is preferably sodium tripolyphosphate. In this case, the concentration of the sodium tripolyphosphate in the polishing agent is preferably between 0.015 mol / L and 0.025 mol / L.At a concentration of sodium tripolyphosphate of not less than 0.015 mol / l, a decrease in polishing rate can be further controlled. A concentration of the sodium tripolyphosphate of not more than 0.025 mol / l prevents an increase in the thickness of the surface oxide film.In the aforementioned polishing agent, the pH is preferably between 8.5 and 9.5 inclusive, and the redox potential y (mV) when the pH is given as x satisfies -60x+1,400≤y≤ -60x+1,700.When the pH is in the range just mentioned and the redox potential is not lower than -60x+1,400, it is possible to enhance the oxidizing effect on the surface of the compound semiconductor, whereby a drop in polishing rate can be further controlled. When the pH is in the range just mentioned and the redox potential is not greater than -60x+1,700, too much progress of oxidation of the compound semiconductor surface is prevented. An increase in turbidity can thereby be further controlled, and similarly LPDs can be further controlled to a minimum. Moreover, corrosion effect on the polishing pad and the tool can be kept to a minimum, thereby enabling polishing in a stabilized state.A compound semiconductor manufacturing method of the present invention includes a step of preparing a GaαIn(1-α)AsβP(1-β) compound semiconductor (where 0≤α≤1; 0≤β≤1), and a step of polishing the surface of the compound semiconductor using a polishing agent according to any one of the foregoing descriptions. In the aforementioned polishing agent, the organic salt of an alkali metal is a sodium dicarboxylate. The sodium dicarboxylate is at least one substance selected from the group consisting of sodium tartrate, sodium malate and sodium succinate. Furthermore, the polishing agent is free of abrasive grains.According to a compound semiconductor manufacturing method of the present invention, a polishing agent according to any one of the foregoing descriptions is used, whereby it is possible to maintain favorable quality of the compound semiconductor surface and also a high polishing rate can be maintained.In the polishing step of the aforementioned compound semiconductor manufacturing method, polishing is preferably performed such that, at a viscosity of the polishing agents of η (mPa • s), a peripheral velocity V (m / s), and the applied pressure P (kPa), the stress coefficient expressed as η × V / P is between 0.08 × 10 -9 and 0.30 × 10 -9 inclusive.If the stress coefficient L is not less than 0.08×10 -9, the stress on the compound semiconductor during the polishing step can be prevented from increasing vigorously. Thereby, an increase in the scratches and micro roughness of the semiconductor surface can be prevented, and thereby an increase in the LPDs can be simultaneously controlled. A load coefficient L of not more than 0.30×10 -9 allows minimization of the drop in polishing rate and also controls an increase in haze.The aforementioned compound semiconductor manufacturing method preferably includes a step of washing the compound semiconductor surface after the above-described polishing step. This makes it possible to advantageously maintain the quality of the compound semiconductor surface.In the aforementioned compound semiconductor manufacturing method, it is preferable that in the preparation step, GaAs (gallium arsenide) is prepared as the compound semiconductor, and that the polishing step and the washing step make the compound semiconductor have a surface oxygen (O) concentration between 4 atomic % and 12 atomic % inclusive and a surface chlorine (Cl) concentration between 120×10 10 atoms / cm 2 and 1,500×10 10 atoms / cm 2 inclusive.By polishing the GaAs in such a manner that the oxygen concentration is not less than 4 atomic % and the chlorine concentration is not less than 120×10 10 atoms / cm 2 a high-resistivity layer can be prevented from forming at the interface when an epitaxial layer is formed on the GaAs. By polishing the GaAs in an At manner that the oxygen concentration is not greater than 12 atomic % and the chlorine concentration is not greater than 1,500×10 10 atoms / cm 2 deterioration in crystallinity of the epitaxial layer as well as roughness and similar drop in quality can be controlled.In the aforementioned compound semiconductor manufacturing method, preferably, the polishing step and the washing step configure the compound semiconductor to have a surface sulfur (S) concentration of 120×10 10 atoms / cm 2 and 1,500×10 10 atoms / cm 2 inclusive.Thereby, when the epitaxial layers are formed on the compound semiconductor, it becomes possible to form epitaxial layers in which favorable quality is maintained.A semiconductor device manufacturing method of the present invention includes a step of preparing a compound semiconductor manufactured by a compound semiconductor manufacturing method according to any one of the foregoing descriptions, and a step of forming an at least single-laminar epitaxial layer on the prepared compound semiconductor.In the compound semiconductor preparation step which is a constituent of a compound semiconductor manufacturing method of the present invention, a polishing agent is used which makes it possible to favorably maintain the surface quality of the compound semiconductor as well as a high polishing rate. Deterioration of the quality of the epitaxial layers formed on the surface of a compound semiconductor obtained in the foregoing preparation step and, moreover, formation of a high-resistivity layer at the junction between the epitaxial layer and the compound semiconductor can thus be controlled. Consequently, it is possible to manufacture semiconductor devices having favorable quality.Advantageous Effects of the InventionWith the aid of a polishing agent of the present invention, the surface quality of a compound semiconductor can be advantageously maintained and, in addition, a high polishing rate can be maintained. Further, in accordance with a compound semiconductor manufacturing method of the present invention, a polishing agent of the present invention is used, whereby a compound semiconductor of an advantageous surface quality can be obtained. According to a semiconductor device manufacturing method of the present invention, the formation of a high-resistivity layer at the junction between the epitaxial layer and the compound semiconductor can be controlled, thereby enabling the manufacture of semiconductor devices having favorable quality.Brief Description of the DrawingsFIG. 1 is a cross-sectional view illustrating, in simplified form, a compound semiconductor of a second embodiment of the present invention. FIG. 2 is a flow chart showing a manufacturing process in a third embodiment of the present invention. FIG. 3 is a cross-sectional view showing, in simplified form, a semiconductor device of a fourth embodiment of the present invention. FIG. 4 is a flow chart showing a manufacturing process of a fifth embodiment of the present invention.DESCRIPTION OF THE EMBODIMENTSHereinafter, description will be made of embodiments and embodiments of the present invention with reference to the drawings. It is to be understood that, hereinafter, identical or corresponding parts are denoted by identical reference numerals in the drawings, and description thereof will not be repeated.Mode 1Next, an explanation will be given of a polishing agent which is Mode 1 of the present invention. A polishing agent of the present Embodiment 1 is a polishing agent used in a GaαIn(1-α)AsβP(1-β) compound semiconductor (where 0≤α≤1; 0≤β≤1), and includes a carbonate of an alkali metal, an organic salt of an alkali metal, a chlorine-based oxidizing agent, and a phosphate of an alkali metal.The sum of the concentrations of the carbonate of an alkali metal and the organic salt of an alkali metal is between 0.01 mol / l and 0.02 mol / l inclusive, and preferably between 0.014 mol / l and 0.016 mol / l inclusive.The pH of the polishing agent can be adjusted by the amount of carbonate of an alkali metal added.In addition, by setting the sum of the two concentrations to be in the above-mentioned range, the etching effect of the polishing agent can be controlled. Further, by setting the sum of the concentrations to be in the above-mentioned range, the concentration of available chlorine in the polishing agent can be controlled.In total, by containing both a carbonate of an alkali metal and an organic salt of an alkali metal, while making the sums of their concentrations within the aforementioned range, both the favorable surface quality (surface properties) and a high polishing rate can be handled. Haze increases with the sum of the concentrations of the carbonate of an alkali metal and the organic salt of an alkali metal of less than 0.01 mol / L, while LPDs increase with a sum of more than 0.02 mol / L.A carbonate of an alkali metal refers to a compound (salt) containing an alkali metal ion and a carbon ion (CO 32) ; sodium carbonate and potassium carbonate are examples that can be cited. It is understood that an "alkali metal" refers to a metal atom element belonging to Group I of the traditional IUPAC nomenclature system (IUPAC-International Union of Pure and Applied Chemistry)-i.e., lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).The concentration of the carbonate of an alkali metal is preferably between 0.008 mol / l and 0.018 mol / l. A concentration of at least 0.008 mol / l allows turbidity increase to be controlled to a minimum. A concentration of at most 0.018 mol / l allows the control of the increase of LPDs to a minimum.An organic salt of an alkali metal refers to a compound (salt) containing an alkali metal ion and an organic acid ion; organic sodium salts and organic potassium salts are examples that can be cited. For the organic sodium salt, a sodium dicarboxylate is preferable in terms of polishing properties, stability and cost. In addition, the supplementary addition of a metal for purposes of complexing effect is effective in keeping the contamination under control and improving the polishing rate. In the same regard, the sodium dicarboxylate is a substance selected from the group consisting of sodium tartrate, sodium malate and sodium succinate.The concentration of the organic salt of an alkali metal is preferably between 0.002 mol / L and 0.004 mol / L inclusive. The addition of an organic salt of an alkali metal at a concentration of at least 0.002 mol / L makes it possible to further emphasize the effect of controlling the etching effect of the polishing agent. When the concentration of the organic salt of an alkali metal is at most 0.004 mol / l, it is possible to prevent the concentration of available chlorine from dropping inside the polishing agent. Moreover, an increase in the carbon dioxide concentration in the waste water, the biochemical oxygen demand (BOD), and the chemical oxygen demand (COD) can be prevented to avoid occurrence of environmental problems.A chlorine-based oxidant refers to a compound, such as a hypochlorite, that contains chlorination (CIO -). Alternatively, the chlorine-based oxidizing agent refers to a compound, such as a salt of a chlorinated isocyanuric acid, containing a solid substance that releases chlorinations (CIO -) when dissolved in water. The chlorine-based oxidizing agent may be, for example, sodium dichloroisocyanurate, potassium dichloroisocyanurate or trichloroisocyanurate. Of these, sodium dichloroisocyanurate is preferable. The chlorine-based oxidizing agent promotes the oxidation of the compound semiconductor surface.The concentration of the chlorine-based oxidizing agent is preferably between 0.035 mol / L and including 0.060 mol / L, and more preferably between 0.040 mol / L and including 0.050 mol / L. At a concentration of the chlorine-based oxidizing agent of at least 0.035 mol / L, a decrease in the polishing rate can be prevented, and at a concentration of at least 0.040 mol / L, a further decrease in the polishing rate can be prevented. On the other hand, when the concentration of the chlorine-based oxidizing agent is at most 0.060 mol / L, an increase in turbidity can be controlled, and when the concentration is not more than 0.050 mol / L, an increase in turbidity can be further controlled.An alkali metal phosphate refers to a compound (salt) containing an alkali metal ion and a phosphate ion, and may be, for example, an orthophosphate, a pyrophosphate, a tripolyphosphate, a tetraphosphate, or a hexphosphate. Of these, sodium tripolyphosphate is preferable. The alkali metal phosphate serves to dissolve oxidation films formed on the surface of the compound semiconductors. In addition, the supplementary addition of a metal for purposes of complexing effect is effective in keeping the contamination under control and improving the polishing rate.The concentration of the alkali metal phosphate is preferably between 0.015 mol / L and 0.025 mol / L inclusive, and more preferably between 0.018 mol / L and 0.022 mol / L inclusive. At a concentration of the alkali metal phosphate of at least 0.015 mol / L, an increase in the thickness of the oxidation layer formed on the surface can be prevented, and when the concentration is at least 0.018 mol / L, an increase in the thickness of the oxidation layer can be additionally prevented. On the other hand, when the concentration of the alkali metal phosphate is at most 0.025 mol / L, a decrease in the polishing rate can be prevented, and when it is at most 0.022 mol / L, a decrease in the polishing rate can be additionally prevented.The pH of the polishing agent is preferably between 8.5 and 9.5 inclusive. In this case, the surface of the compound semiconductor can be oxidized efficiently, whereby a high polishing rate can be maintained.Preferably, the redox potential y (mV) of the polishing agent, when the pH is given as x, satisfies -60x+1,400≤y-60x+1,700. If the redox potential y of the polishing agent is at least -60x+1,400, attenuation of the oxidizing effect on the compound semiconductor surface can be prevented, whereby a drop in the polishing rate can be avoided. Moreover, an increase in the mechanical effect can be prevented, whereby an increase in the scratch and the micro roughness can be avoided. If the redox potential y of the polishing agent is at most -60x+1,700, excessive progress of oxidation of the compound semiconductor surface can be avoided, whereby the increase in haze can be kept to a minimum. Further, the corrosion effect on the polishing pad and the tool can be prevented from increasing too much, thereby enabling polishing in a stable state. Here, scratching can be evaluated by optical microscopic examination or by visual examination under illumination with a fluorescent lamp or spot beam. Micro roughness can be evaluated by AFM or with an optical interferometric profiler.A polishing agent in the present embodiment 1 is used on a GaαIn(1-α)AsβP(1-β) compound semiconductor (where 0≤α≤1; 0≤β≤1). That is, a polishing agent in the present embodiment 1 is used on GaAs, InP (indium phosphide), and crystal alloys thereof. A polishing agent in the present embodiment 1 is preferably used on a crystal of at least 50% Ga or As, and more preferably on GaAs.When a GaαIn(1-α)AsβP(1-β) compound semiconductor (where 0≤α≤1; 0≤β≤1) is used as a substrate for epitaxial growth, the quality of the substrate surface is becoming important. The surface quality differs from the quality of the crystal mass. The chemical durability of GalnAsP is high as compared with Si, and in polishing agents for Si, the surface oxidation does not easily progress. Accordingly, in polishing agents for Si during a GalnAsP polishing process, the mechanical effect is predominant, so that scratches and micro roughness on the substrate surface increase. Further, the polishing rate falls, thereby causing productivity problems.Against this drawback, in order to increase the chemical effect of the polishing agent used on GaαIn(1-α)AsβP(1-β)(where 0≤α≤1; 0≤β≤1), a technique is conceivable in which an oxidizing agent is added to increase the redox potential. However, since the chemical durability of GaαIn(1-α)AsβP(1-β)(where 0≤α≤1; 0≤β≤1) is low as compared with GaN (gallium nitride) and AlN (aluminum nitride), there is a risk of variation by the chemical action of the polishing agent and the atmosphere, so that control of the surface is remarkably difficult. Moreover, the effect of the chemical components differs depending on the nature of the substrate material, and the suitability of a pH or potential or a pH adjuster or oxidizer differs depending on the nature of each crystal material.From these points of view, the polishing agents mentioned in the aforementioned Patent Documents 1 to 3 were unsuitable for satisfying both the surface properties and the polishing rate.The present inventors have found that in a polishing agent, in addition to utilizing the oxidation properties that a chlorine-based oxidizing agent has with respect to the area of a compound semiconductor and the properties of removing an oxidation film having alkali metal phosphate by including a carbonate of an alkali metal and an organic salt of an alkali metal, the sum of concentrations thereof is between 0.01 mol / L and 0.02 mol / L inclusive, the adjustment of the pH and the etching effect of the polishing agent can be controlled. As a result, the present inventors have first demonstrated that the polishing rate and the quality of the polished GalnAsP surface can be controlled by using a polishing agent of the present Embodiment 1. Accordingly, by using a polishing agent of the present Embodiment 1 to polish GalnAsP, the quality of the GalnAsP surface can be maintained advantageously and also a high polishing rate can be maintained.It is to be understood that, as long as the sum of the concentrations of the carbonate of an alkali metal and the organic salt of an alkali metal in the polishing agent during polishing is between 0.01 mol / L and 0.02 mol / L inclusive, even if a part of the organic salt of an alkali metal is replaced with an organic acid and sodium hydroxide, or a part of the carbonate of an alkali metal is replaced with a carbonic acid and sodium hydroxide, the same resultant advantages as just explained are obtained. Nevertheless, in view of its chemical stability and ease of handling, the inclusion of an additive by an organic salt of an alkali metal and a carbonate of an alkali metal is preferable.Mode 2Mode 2 of the present invention relates to a compound semiconductor. FIG. 1 is a cross-sectional view showing, in simplified form, a compound semiconductor 10 of Embodiment 2. Referring to FIG. 1, an explanation will be given of the compound semiconductor 10 of the present Embodiment 2.As shown in FIG. 1, the compound semiconductor 10 is a substrate having a surface 11. Compound semiconductor 10 is a GaαIn(1-α)AsβP(1-β) compound semiconductor (where 0≤α≤1; 0≤β≤1), preferably a crystal having at least 50% Ga or As, and more preferably GaAs.The method for growing the aforementioned compound semiconductor crystal is not specifically specified; it can be grown by methods such as HB (horizontal Bridgman) technique, LEC (liquid enclosed Czochralski) technique, and VB (vertical Bridgman) technique.The face 11 has an oxygen concentration between 4 atomic % and 12 atomic % inclusive, and preferably an oxygen concentration between 5 atomic % and 10 atomic % inclusive. When the oxygen concentration is at least 4 atomic %, formation of a high-resistivity layer at the junction can be controlled during growth of an epitaxial layer formed on the compound semiconductor 10. If it is at least 5 atomic %, the formation of a high-resistivity layer can be further kept to a minimum. If the oxygen concentration does not exceed 12 atomic %, deterioration of epitaxial layer crystallinity, roughness and similar deterioration of quality can be controlled. If it is not more than 10 atomic %, the deterioration of the quality of the epitaxial layer can be further kept to a minimum.It is understood that the aforementioned oxygen concentrations are values determined by, for example, Auger electron spectroscopy (AES) or X-ray photoelectron spectroscopy (XPS). AES characterizes the chemical composition by means of the electron exit depth according to Auger up to a 5-nm level from the epi surface along the surface 11.The surface 11 preferably has a chlorine concentration between 120×10 10 atoms / cm 2 and including 1,500×10 10 atoms / cm 2 and preferably a chlorine concentration between 200×10 10 atoms / cm 2 and including 1,000×10 10 atoms / cm 2. When the chlorine concentration is not less than 120×10 10 atoms / cm 2, the formation of a high-resistivity layer at the junction during the growth of an epitaxial layer formed on the compound semiconductor 10 can be controlled. If it is not less than 200×10 10atoms / cm 2, the formation of a high-resistivity layer can be further kept to a minimum. If the chlorine concentration is not more than 1,500×10 10 atoms / cm 2, deterioration of epitaxial layer crystallinity, roughness and similar drops of their quality can be controlled. If it is not larger than 1,000×10 10atoms / cm 2, the deterioration of the quality of the epitaxial layer can be further kept to a minimum.The surface 11 preferably has a sulfur concentration between 120×10 10 atoms / cm 2 and including 1,500×10 16 atoms / cm 2 and more preferably a sulfur concentration between 150×10 10 atoms / cm 2 and including 1,000×10 10 atoms / cm 2. If the sulfur concentration is not less than 120×10 10 atoms / cm 2, the formation of a high-resistivity layer at the junction during the growth of an epitaxial layer formed on the compound semiconductor 10 can be controlled. If it is not less than 200×10 10atoms / cm 2, the formation of a high-resistivity layer can be further kept to a minimum. If the sulfur concentration is not more than 1,500×10 10 atoms / cm 2, deterioration of epitaxial layer crystallinity, roughness and similar drops of their quality can be controlled. If it is not larger than 1,000×10 10atoms / cm 2, the deterioration of the quality of the epitaxial layer can be further kept to a minimum.It is understood that the aforementioned chlorine concentrations and sulfur concentrations are values determined with TXRF, for example.TXRF characterizes the chemical composition by means of the X-ray probe depth, for example up to a 5 nm level from the epi surface along the surface 11. "the surface 11" here has a thickness obtained by measuring its constituents with the aid of TXRF or AES, the thickness being in the order of, for example, 5 nm.Moreover, the difference between the surface and internal chemical compositions of the compound semiconductor 10 and the chemical composition of the junction between the compound semiconductor 10 and the epitaxial layer formed thereon can be characterized by, for example, performing depth analysis using SIMS.The haze in the area 11 is preferably not greater than 1.6 ppm, more preferably not greater than 1.0 ppm.Similarly, the LPDs in the area 11 are preferably less than 14 defects / substrate, and more preferably at most 10 defects / substrate.Here, the aforementioned haze and LPD values are determined by, for example, surface scanning.In addition, an oxidation layer (not shown) may be formed on the surface 11. In this case, the thickness of the oxidation layer is preferably not greater than 1 nm, and more preferably not greater than 0.8 nm. Such a configuration can prevent deterioration of the quality of the epitaxial layer formed on the compound semiconductor. It is noted that the thickness of the oxidation layer just described is a value determined with an ellipsometer.Mode 3The embodiment of the present invention relates to a manufacturing method, wherein a compound semiconductor 10 of the embodiment 2 is manufactured by the manufacturing method. The manufacturing process of Embodiment 3 is shown in the flowchart of FIG. 2. Next, referring to FIGS. 1 and 2, an explanation will be given of a manufacturing method of the present Embodiment 3.Reference is now made to FIG. 2. In a manufacturing method of Embodiment 3, a GaαIn(1-α)AsβP(1-β) compound semiconductor (where 0≤α≤1; 0≤β≤1) is initially prepared (step S1). The compound semiconductors prepared in step S1 are preferably crystals having not less than 50% Ga or As, and are more preferably GaAs. In step S 1, substrates having one surface are prepared as compound semiconductors.In step S 1, for example, the following processes are performed. Initially, a ingot of a GalnAsP compound semiconductor is grown by the HB technique, the VB technique or the like. The ingot produced by the crystal growth is subjected to processes including machining the ingot along its peripheral edge and slicing it, and grinding, lapping, polishing and washing the slices to produce the compound semiconductors. In order to planarize the compound semiconductors, mechanical operations such as grinding and lapping may be performed. As surface finishing operations after polishing, in order to reduce roughness and remove the laminars materially changed by the machining operations, CMP (chemical mechanical polishing), chemical polishing or the like may be performed.It is understood that the compound semiconductors prepared in step S 1 may be, for example, a bulk crystal or a thin film formed on a basic shape consisting of a bulk crystal or the like.Next, the polishing agent of Embodiment 1 is used to finish polishing the surface of the compound semiconductors (step S2). In step S 2, the polishing agent does not contain abrasive grains from the viewpoint of improving the surface quality. Thereby, scratches, roughness, and the like are alleviated.In step S 2, polishing is preferably performed in a manner such that, at a viscosity of the polishing agent of η (mPa·s), the rotational speed V (m / s), and the applied pressure P (kPa), the load coefficient L expressed as η×V / P is between 0.08×10 -9 and 0.30×10 -9 inclusive. If the load coefficient L is not less than 0.08×10 -9, a sharp increase in the load on the compound semiconductors during polishing can be avoided, whereby an increase in the scratch, the micro roughness, and the like can be prevented, and further an increase in the LPDs can be controlled. When the load coefficient L is not more than 0.30×10 -9, a decrease in polishing rate can be prevented and an increase in haze can be controlled. Furthermore, the content of CI in the faces of the compound semiconductor can be kept to a minimum.It is understood that the above-mentioned viscosity can be adjusted by the concentrations of the chemical components or by adding a highly viscous organic compound such as ethylene glycol.After the adjustment of the polishing agent used in step S 2, the time until it is used for polishing is preferably within 60 minutes. In 60 minutes, the decrease in the effect of the polishing agent can be minimized, whereby the deterioration of the scratch, the micro roughness, and the like can be avoided. From this consideration, the time is preferably 40 minutes, but more preferably between 5 minutes and 30 minutes inclusive.By using a polishing agent of Mode 1, the polishing rate at step S 2 may be 1.8 μm / minute or more, for example.In step S 2, the polishing is preferably performed in a manner in which the chlorine concentration of the compound semiconductor surfaces is between 120×10 10 atoms / cm 2 and including 1,500×10 10 atoms / cm 2 and more preferably, the polishing is performed in a manner in which it is between 200×10 10 atoms / cm 2 and including 1,000×10 10 atoms / cm 2. The chlorine concentration in the compound semiconductor areas can be adjusted by using the stress coefficient L described above. In particular, the chlorine concentration in the compound semiconductor areas having a high stress coefficient L can be raised, while the chlorine concentration in the areas can be reduced by a low stress coefficient L. In addition, the chlorine concentration in the compound semiconductor surfaces can be adjusted by the concentration of the chlorine ions in the polishing agent.In step S 2, polishing is performed in a manner in which the oxygen concentration in the compound semiconductor surfaces is preferably between 4 at % and 12 at % inclusive, and more preferably between 5 at % and 10 at % inclusive. The oxygen concentration in the compound semiconductor surfaces can be adjusted by means of the redox potential of the polishing agent. In order to realize an oxygen concentration in the above range, a polishing agent is used which has, for example, a pH value between 8.5 and 9.5 inclusive and whose redox potential y (mV) satisfies -60x+1,400≤y≤-60x+1,700 when the pH value is given as x. In order to improve the gains of the device, it is preferable that the chlorine concentration in the areas be between 120×10 10 atoms / cm 2 and 1,500×10 10 atoms / cm 2 inclusive, and the oxygen concentration be between 4 atomic % and 12 atomic % inclusive. For this purpose, it is preferable to use a polishing agent whose redox potential satisfies y (mV) when the pH is given as x -60x+1,400≤y≤ -60x+1,700 in order to polish under conditions where the load coefficient L is between 0.08×10 -9 and 0.30×10 -9 inclusive.Moreover, in step S 2, polishing is preferably performed such that the sulfur concentration in the areas is between 120×10 10 atoms / cm 2 and 1,500×10 10 atoms / cm 2 inclusive.Next, the compound semiconductor surfaces are washed (step S3). During the washing in step S 3, bubbling or ultrasonic waves may be used. Examples that can be cited for this type of washing include washing in IPA (isopropyl alcohol), washing in choline, and washing in ultra pure water. In these cases, contaminants can be effectively removed and particles can be reduced. In addition, a trace concentration of sulfuric acid can be added to the ultra pure water. In this case, the S concentration in the areas can be kept to a minimum. The S concentration in the surfaces of the compound semiconductors after washing is preferably between 120×10 10 atoms / cm 2 and including 1,500×10 10 atoms / cm 2 and more preferably between 150×10 10 atoms / cm 2 and including 1,000×10 10 atoms / cm 2.Further, the thickness of the oxidation layer on the compound semiconductor surfaces can be reduced by washing step S 3. The thickness of the oxidation layer after washing is preferably not greater than 1 nm, and more preferably not greater than 0.8 nm.If the chlorine concentration in the areas of the compound semiconductors reached in step S 2 after polishing is less than 120×10 10 atoms / cm 2 or exceeds 1,500×10 10 atoms / cm 2, then in step S 3, the washing process is preferably carried out such that the chlorine concentration in the areas will be between 120×10 10 atoms / cm 2 and including 1,500×10 10 atoms / cm 2.Similarly, if the oxygen concentration in the areas of the compound semiconductors obtained in step S2 after polishing is less than 4 atomic % or exceeds 12 atomic %, then in step S3, the washing process is preferably carried out such that the oxygen concentration in the areas is between 4 atomic % and 12 atomic % inclusive.Examples which can be cited for the above-described manner of washing include washing in hydrochloric acid, washing in choline and washing in ultra pure water.If the sulfur concentration in the areas of the compound semiconductors reached in step S 2 is below 120×10 10 atoms / cm 2 or exceeds 1,50010 10 atoms / cm 2, after polishing, then in step S 3, the washing is preferably carried out such that the sulfur concentration in the areas is between 120×10 10 atoms / cm 2 and including 1,500×10 10 atoms / cm 2.A compound semiconductor 10 of FIG. 1 of Mode 2 can be manufactured by executing the aforementioned steps (steps S 1 to S 3).According to a manufacturing method of Embodiment 3, in that a polishing agent of Embodiment 1 is used, the concentration of impurities in the surface 11 of the compound semiconductors 10 can be controlled to an appropriate extent. Accordingly, when using a compound semiconductor 10 as a substrate for LEDs, lasers, or similar semiconductor devices, formation of a high-resistivity layer at the junction between the substrate and the epitaxial layer(s) can be suppressed to a minimum. Consequently, the use of the compound semiconductors for manufacturing semiconductor devices can prevent the increase in resistance, whereby a decrease in light emission efficiency can be minimized.Mode 4FIG. 3 is a cross-sectional view illustrating, in simplified form, a semiconductor device 20 in an embodiment 4 of the present invention. Referring to FIG. 3, a description will be given of the semiconductor device 20 of the present Embodiment 4.Reference is made to FIG. 3. A semiconductor device 20 of Mode 4 is provided with a compound semiconductor 10 of Mode 2, an epitaxial layer 21 formed on the surface 11 of the compound semiconductor 10, an electrode 22 formed on the epitaxial layer 21, and an electrode 23 formed on the compound semiconductor 10 on the side thereof facing away from the epitaxial layer. The semiconductor device may be, for example, a light emitting device such as a light emitting diode or laser diode, a microelectronic device such as a rectifier, a bipolar transistor, a field effect transistor or a HEMT (High Electron Mobility Transistor), a semiconductor sensor such as a temperature sensor, a pressure sensor, a radiation sensor or a non-visible UV ray detector, or a SAW device (Surface Acoustic Wave Device). In the present embodiment 4, the epitaxial layer 21 preferably includes an active layer, and the semiconductor device is a laser or an LED.Mode 5Mode 5 of the present invention relates to a manufacturing method of manufacturing a semiconductor device 20 of Mode 4 of the present invention by the manufacturing method.FIG. 4 is a flowchart showing a flow for manufacturing a semiconductor device 20. An explanation will be given of a manufacturing method in Mode 5 of the present invention.Reference is made to FIG. 4. Step S 1 of preparing a compound semiconductor 10 in Mode 2, Step S 2 of polishing for finishing, and Step S 3 of washing are performed.Next, an epitaxial layer 21 is formed on the surface 11 of the compound semiconductor 10 (step S 4). Examples of techniques by which the epitaxial layer 21 is formed include MOCVD (Metal Organic Chemical Vapor Deposition), MBE (Molecular Beam Epitaxy), or other vapor phase technique, as well as LPE (Liquid Phase Epitaxy) or other liquid phase technique.Next, an electrode 22 is formed on the epitaxial layer 21 and an electrode 23 is formed on the compound semiconductor 10 on the side thereof which is opposite from the epitaxial layer 21 (step S 5). The electrodes may be formed together on the one side of the epitaxial layer 21. The electrodes 22 and 23 are formed by vapor deposition, for example. Moreover, dicing and package mounting may be performed.The execution of the above-described steps (steps S 1 to S 5) makes it possible to produce a semiconductor device 20 as shown in FIG. 3. In a semiconductor device manufactured in this manner, since the surface properties of the surface 11 of the compound semiconductor 10 are advantageously maintained, impurities at the junction between the compound semiconductor 10 and the epitaxial layer 21 are controlled. Accordingly, in an embodiment where the semiconductor device 20 is, for example, a light emitting device, with the reduction in factors hindering the inflow of electrons into the active layer, the characteristics of the light emitting device can be advantageously maintained. Moreover, semiconductor devices 20 can be manufactured by Mode 5 to improve gains.Embodiment 1In the present embodiment, the effectiveness of a polishing agent containing a carbonate of an alkali metal, an organic salt of an alkali metal, a chlorine-based oxidizing agent and a phosphate of an alkali metal, and in which the sum of the concentrations of the carbonate of an alkali metal and the organic salt of an alkali metal was between 0.01 mol / L and 0.02 mol / L inclusive, was studied.Examples 1-6 of the present invention and Comparative Examples 1-9Initially, a Si-doped GaAs substrate grown by the VB technique was prepared as compound semiconductors.Thereafter, its peripheral edge was machined, cut into disks, and both sides of the disks were lapped and wet-etched, thereby producing non-specular substrates 76 mm in diameter and 550 μm in thickness, respectively. The respective substrates were bonded to a ceramic plate, followed by single-side polishing as a primary polishing. For the one-side polishing, CMP was carried out by means of a polishing agent containing colloidal silica (step S1). The primary polish made the GaAs substrates specular.Next, polishing agents of the compositions shown in Table I and Table II were prepared as polishing agents of Examples 1 to 6 of the present invention and Comparative Examples 1 to 9, respectively. The respective polishing agents were used to perform respective polishings on the prepared GaAs substrates. As the polishing apparatus, a machine having a plate of 820 mm in diameter, wherein the polishing pads used were of a wild leather, was used (step S2).After the finishing finish polishing, the GaAs substrates were peeled from the plate and subjected to an IPA washing process, a choline washing process and a ultrapure water washing process (step S3). The thickness of each substrate was 500 μm. Thus, compound semiconductors according to Examples 1 to 6 of the present invention and Comparative Examples were produced.Evaluation MethodThe polishing rates were respectively determined on the compound semiconductors of Examples 1 to 6 of the present invention and Comparative Examples 1 to 9. The results are shown as polishing rates ("polishing speed (μm / min)") in Tables I and II shown below.Surfscan ®6220 of KLA-Tencor Corporation was used to determine the LPDs and haze in the surfaces of the compound semiconductors of Examples 1 to 6 of the present invention and Comparative Examples 1 to 9 on which polishing was carried out. The results are shown in Tables I and II below.On the polished surface of the compound semiconductors of Examples 1 to 6 of the present invention and Comparative Examples 1 to 9, an epitaxial layer was formed by MOCVD, and the PL intensity was determined according to a PL intensity determination method under the following conditions. A light emitting layer having a multiquantum well structure formed of an n-type Al x1 Ga y1 In 1-x1-y1 P semiconductor layer (where 0 < x 1; 0 < y 1; x 1+ y 1< 1) and five pairs of well layers (Ga y3 In 1-y3 P layers (where 0<y 3< 1)) and barrier layers (Al x4 Ga y4 In 1-x4-y4 P layers (where 0<x 4; 0 < y 4; x 4+ y 4< 1)) a p-type Al x2 Ga y2 In 1-x2-y2 P-type semiconductor layer (where 0<x 2; 0 < y 2; x 2+ y 2< 1) and a p-type GaAs contact layer were formed as an epitaxial layer. With an excitation beam wavelength of 532 nm, light between 600 nm and 700 nm inclusive was scattered and detected with a photomultiplier to measure the PL intensity. As the measuring device, a PLM 150 manufactured by Nanometrics Inc. was used. The results are recorded as "PL intensity" (units: a.u.) at "epi-properties" in Table I and Table II listed below (step S4).Then, an Au-Zn contact electrode as a p-side electrode was formed on the p-type GaAs contact layers of Examples 1 to 6 of the present invention and Comparative Examples 1 to 9 by vacuum evaporation deposition. On the main surface, which is where the group III-V compound semiconductor layer was not formed, of the n-type GaAs semiconductor substrate, an Au-Ge contact electrode was formed as an n-side electrode by vacuum deposition (step S5). The gains of the semiconductor devices thus fabricated were determined. The results are recorded as "gain" for "device properties" in Table I and Table II, listed below. Table I Table IMolarity of polishing agentNa carbonate (mol / l)0,0080,0080,0120,0140,0140,018Na malate (mol / l)0,0020,0040,0020,0020,0040,002Na-dichloroisocyanurate (mol / l)0,030,030,030,030,030,03Na tripolyphosphate (mol / l)0,020,020,020,020,020,02Polishing PropertiesPolishing Rate (μm / min)1,81,92222,2Substrate PropertiesLPDs (Defects / Substrate)4567810Turbidity (ppm)1,210,910,860,850,92Epi PropertiesPL intensity (a.u.)1,21,61,81,71,51,4Device CharacteristicsGain (%)566275705853Table IITable IIMolarity of polishing agentNa carbonate (mol / .)0,0080,0060,0240,0200,020000,0080,008Na malate (mol / l)00,00200,00400,010,020,0040,004Na-dichorisocyanurate (mol / l)0,030,030,030,030,030,030,0300,03Na tripolyphosphate (mol / l)0,020,020,020,020,020,020,020,020Polishing PropertiesPolishing Rate (μm / min)1,41,32,32,3,2,20,90,80,40,3Substrate PropertiesLPDs (Defects / Substrate)7541321412132224Turbidity (ppm)2,12,31,2112,82,81,41,5Epi PropertiesPL intensity (a.u.)0,60,40,80,91,00,20,20,50,4Device CharacteristicsGain (%)1002428450000Evaluation resultsOn the area of the compound semiconductors of Examples 1 to 6 of the present invention, as shown in Table 1, the sum of the concentrations of the carbonate of an alkali metal and the organic salt of an alkali metal was between 0.01 mol / L and 0.02 mol / L inclusive, and the LPDs were 10 (defects / substrate) or less, while the haze was 1.2 ppm or less, so that a preferable quality of the areas could be maintained. Moreover, the polishing rates for Examples 1 to 6 of the present invention were 1.8 μm / minute or more, which means that a high polishing rate could be maintained.Forming an epitaxial layer on the surface of the compound semiconductors produced using the polishing agents of Examples 1 to 6 of the present invention made it possible to set the PL intensity to 1.2 and more, among others, and allowed maintenance of high quality of the epitaxial layer.The production of semiconductor devices using compound semiconductors produced by the polishing agents of Examples 1 to 6 of the present invention enabled a gain of at least 53%.On the other hand, as shown in Table II, Comparative Example 1 using a polishing agent containing little carbonate of an alkali metal and no organic salt of an alkali metal and Comparative Example 2 using a polishing agent whose sum of the carbonate of an alkali metal and the organic salt was small, the haze was high and the polishing rate was low.In Comparative Example 3 using a polishing agent having a large carbonate of an alkali metal and no organic salt of an alkali metal and Comparative Example 4 whose sum of the carbonate of an alkali metal and the organic salt was large, the LPDs were high.In Comparative Example 5 using a polishing agent containing no organic salt, the LPDs were high. In Comparative Examples 6 and 7 using a polishing agent containing no carbonate of an alkali metal, the haze and the LPDs were high and the polishing rate was low.In Comparative Example 8 using a polishing agent containing no chlorine-based oxidizing agent, the haze and the LPDs were high and the polishing rate was low. In Comparative Example 9 using a polishing agent containing no alkali metal phosphate, the haze and LPDs were high and the polishing rate was low.Further, the formation of epitaxial layers using the compound semiconductors of Comparative Examples 1 to 9 resulted in PL intensities lower than those of Examples 1 to 6 of the present invention. Similarly, the gains when semiconductor devices were manufactured using the compound semiconductors of Comparative Examples 1 to 9 were lower than those in Examples 1 to 6 of the present invention. From these facts, it is clear that the deterioration of the quality of the semiconductor device is due to the fact that the quality of the compound semiconductor surfaces is low.As is apparent from the foregoing, it has been confirmed that according to the present invention, by using a polishing agent containing a carbonate of an alkali metal, an organic salt of an alkali metal, a chlorine-based oxidizing agent and a phosphate of an alkali metal and in which the sum of the concentrations of the carbonate of an alkali metal and the organic salt of an alkali metal is between 0.01 mol / L and 0.02 mol / L inclusive, favorable quality of the semiconductor surfaces and also high polishing rates can be maintained.Embodiment 2In the present embodiment, the effectiveness of using sodium dichloroisocyanurate having a concentration between 0.035 mol / L and 0.060 mol / L inclusive as the chlorine-based oxidizing agent was studied.Examples 7 to 12 of the present inventionInitially, the same process operations as in Embodiment 1 were performed to prepare Si-doped GaAs substrates grown by the HB technique as compound semiconductors (step S1).Next, polishing agents of the compositions listed in Table III below were prepared as polishing agents for Examples 7 to 12 of the present invention, respectively. The finish polishing operation was carried out in the same manner as in Examples 1 to 6 of the present invention, but was different in that the finish polishing was carried out by using the polishing agents shown in Table III. In this way, substrates each having a diameter of 50 mm and a thickness of 400 μm were produced. This resulted in the prepared compound semiconductors of Examples 7 to 12 of the present invention.Evaluation MethodThe polishing rates (polishing rates) on and the LPDs and haze in the compound semiconductors of Examples 7 to 12 of the present invention were determined, respectively. The polishing rate, LPDs and haze were determined in the same manner as in Embodiment 1.Moreover, the PL intensity and the gain of the semiconductor device were respectively determined using the compound semiconductors of Examples 7 to 12 of the present invention in the same manner as in Embodiment 1. Table III Table IIINa carbonate (mol / l)0,0080,0080,0080,0080,0080,008Molarity of polishing agentNa malate (mol / l)0,0040,0040,0040,0040,0040,004Na-dichloroisocyanurate (mol / l)0,0300,0350,0400,0500,0600,090Na tripolyphosphate (mol / l)0,0180,0180,0180,0180,0180,018Polishing PropertiesPolishing Rate (μm / min)1,722,12,32,22,3Substrate PropertiesLPDs (Defects / Substrate)554458Turbidity (ppm)0,911,11,21,31,6Epi PropertiesPL intensity (a.u.)1,21,21,21,21,11,2Device CharacteristicsGain (%)646870727163Evaluation resultsAs shown in Table III, in the compound semiconductors of Examples 7 to 12 of the present invention, it was clear that low LPDs and haze could be maintained and that a high polishing rate could be maintained. Similarly, it was understood that it was possible to improve the properties of the epitaxial layers and the properties of the devices produced using the compound semiconductors of Examples 7 to 12 of the present invention.As is clear from Table III, it was clear that with Examples 8 to 11 of the present invention using sodium dichloroisocyanurate at a concentration of between 0.035 mol / L and 0.060 mol / L inclusive, particularly low LPDs and turbidity could be maintained while high polishing rates could be maintained. That is, the polishing rate in Example 7 of the present invention using less than 0.035 mol / L of sodium dichloroisocyanurate was lower than that in Examples 8 to 11 of the present invention. Similarly, the haze in Example 12 of the present invention using sodium dichloroisocyanurate above 0.060 mol / L was greater than in Examples 8 to 11 of the present invention.From the foregoing, it was confirmed that according to the present invention, the use of sodium dichloroisocyanurate at a concentration of 0.035 mol / L to 0.060 mol / L inclusive as a chlorine-based oxidizing agent allowed further improvement in polishing rates and allowed the quality of the compound semiconductor surfaces to be maintained at a higher level.Embodiment 3In the present embodiment, the effectiveness of the alkali metal phosphate, which is sodium tripolyphosphate at a concentration between 0.015 mol / L and 0.025 mol / L inclusive, was studiedExamples 13 to 18 of the present inventionInitially, Si-doped GaAs substrates grown by the VB technique were prepared as compound semiconductors (step S1).Next, polishing agents of the compositions listed in the following Table IV were prepared as the polishing agents of Examples 13 to 18 of the present invention. Polishing was carried out in substantially the same manner as in Examples 1 to 16 of the present invention, but was different in that the finishing polishing was carried out by using the polishing agents shown in Table III. In this way, substrates 76 mm in diameter and 650 μm in thickness were produced, respectively. This resulted in the prepared compound semiconductors of Examples 13 to 18 of the present invention.Evaluation MethodWith respect to the compound semiconductors of Examples 13 to 18 of the present invention, the polishing rates (polishing rates), the LPDs, the haze, and the thickness of the oxidation film on the finish polished surfaces were respectively determined. The polishing rate, the LPDs and the haze were determined in the same manner as in Embodiment 1. The results are shown in Table IV below.Moreover, the PL intensity and the gain of the semiconductor device were respectively determined using the compound semiconductors of Examples 13 to 18 of the present invention in the same manner as in Embodiment 1. The results are shown in Table IV below. Table IV Table IVMolarity of polishing agentNa carbonate (mol / l)0,0180,0180,0180,0180,0180,018Na malate0,0020,0020,0020,0020,0020,002Na-dichorisocyanurate (mol / l)0,030,030,030,030,030,03Na tripolyphosphate (mol / l)0,0100,0150,0180,0220,0250,035Polishing PropertiesPolishing Rate (μm / min)1,61,92,12,32,42,5Substrate PropertiesLPDs (Defects / Substrate)878679Turbidity (ppm)0,930,950,950,970,981Oxidation film thickness (nm)0,720,780,80,8211,2Epi PropertiesPL intensity (a.u.)1,31,21,11,11,11Device CharacteristicsGain Gain495253545150Evaluation resultsAs shown in Table IV, in the compound semiconductors of Examples 13 to 18 of the present invention, it was apparent that low LPDs and haze could be maintained and a high polishing rate could be maintained. Similarly, it was understood that it was possible to improve the properties of the epitaxial layers and the properties of the devices produced using the compound semiconductors of Examples 13 to 18 of the present invention.In addition, as shown in Table IV, it was clear that with Examples 14 to 17 of the present invention using sodium tripolyphosphate at a concentration between 0.015 mol / L and 0.025 mol / L inclusive, particularly low LPDs and turbidity could be maintained while high polishing rates could be maintained. That is, the polishing rate in Example 13 of the present invention using less than 0.015 mol / L sodium tripolyphosphate was lower than that of Examples 14 to 17 of the present invention. Similarly, the oxidation film thickness of Example 18 of the present invention using sodium tripolyphosphate above 0.025 mol / L was greater than that of Examples 14-17 of the present invention. Although the PL intensity once an epitaxial layer was formed using the compound semiconductor of Example 18 of the present invention was higher than that of Comparative Examples 1 to 9, it was nevertheless lower than that of Examples 14 to 17 of the present invention.From the foregoing, it was confirmed that, in accordance with the present invention, for the alkali metal phosphate using sodium tripolyphosphate at a concentration of 0.015 mol / L to 0.025 mol / L inclusive, further improvement of polishing rates was possible and the quality of the compound semiconductor surfaces could be maintained at a higher level.Embodiment 4In the present embodiment, the effectiveness of a polishing agent was studied, whose pH value was between 8.5 and 9.5 inclusive and whose redox potential y (mV) when the pH value is given as x satisfies -60x+1,400≤y≤ -60x+1,700. At the same time, the efficiency of polishing was studied in which, when the viscosity of the polishing agent is η (mPa·s), the peripheral velocity V (m / s), and the applied pressure P (kPa), the load coefficient L expressed as η × V / P is between 0.08 × 10 -9 and 0.30 × 10 -9 inclusive.Examples 19 to 28 of the present inventionInitially, Si-doped GaAs substrates grown by the VB technique were prepared as compound semiconductors (step S1).Next, in Examples 19 to 28 of the present invention, polishing agents containing sodium carbonate as the alkali metal, sodium malate as the organic salt of an alkali metal, sodium dichloroisocyanurate as the chlorine-based oxidizing agent, and sodium tripolyphosphate as the alkali metal phosphate were used, the sum of the concentrations of the carbonate of an alkali metal and the organic salt of an alkali metal being between 0.01 mol / L and 0.02 mol / L inclusive. It is noted that as for the molarity of the polishing agent of Example 23 of the present invention, the sodium carbonate was set to 0.012 mol / L; the sodium malate was set to 0.006 mol / L; the sodium dichloroisocyanurate was set to 0.05 mol / L; and the sodium tripolyphosphate was set to 0.02 mol / L.Polishing was carried out in substantially the same manner as in Examples 1 to 6 of the present invention, but was different in that the finishing polishing was carried out according to the polishing conditions shown in Table V using the polishing agents just described. Substrates 76 mm in diameter and 600 μm in thickness were thereby produced in each case. This resulted in the prepared compound semiconductors of Examples 19 to 28 of the present invention.Here, the pH values of the polishing compositions listed in Table V below are values measured using a pH / concentration meter calibrated using standard buffer solutions of pH 10.0, pH 6.9, and pH 4.0.Evaluation MethodWith respect to the compound semiconductors of Examples 19 to 28 of the present invention, the polishing rates (polishing rates), the oxygen concentrations and the chlorine concentrations were determined, respectively. Oxygen concentrations were determined by AES and chlorine concentrations by TXRF. The results are shown in Table V, which is presented below.In addition, the respective gains of the semiconductor device using the compound semiconductors of Examples 19 to 28 of the present invention were determined in the same manner as in Embodiment 1. Table V Table VPolishing AgentpH9999999999Potential (mV)75086086095010501160116012101160860Polishing ConditionsLoad coefficient L π×V / P (x10-9)0,080,050,080,120,20,300,400,300,080,30Viscosity (mPa·s)0,9610,961111,210,961Circumferential speed (m / s)2,51,82,5344,554,52,54,5Pressure (kPa)30363025201515153015Polishing PropertiesPolishing Rate (μm / min)1,61,91,71,92,22,31,32,32,51,5Substrate PropertiesOxygen concentration (at %)344510121216124Chorus concentration (x 10 10 atoms / cm 2)1206012020010001500200015001201500Device CharacteristicsGain Gain36385572655135328263Evaluation resultsAs seen in Table V, in Examples 20-25, 27 and 28 of the present invention, in which the polishing agents had a pH between 8.5 and 9.5 inclusive and a redox potential y (mV) at a given pH x satisfying -60x+1,400≤y≤-60x+1,700, the surface oxygen concentration was between 4 atomic % and 12 atomic % inclusive, which was within an appropriate range.On the other hand, in Example 19 of the present invention, in which the redox potential y (mV) at a given pH x was less than -60x+1,400≤y and the oxygen concentration was 3 atomic %, the oxygen concentration was low. Besides, as for Example 26 of the present invention, in which the redox potential y (mV) at a given pH x was larger than y ≤ -60x + 1,700 and the oxygen concentration was 16 atomic %, the oxygen concentration was high.Further, in Examples 19, 21 to 24, and 26 to 28 polished in such a manner that, at a polishing agent viscosity η (mPa·s), a peripheral velocity V (m / s), and an applied pressure P (kPa), the load coefficient L expressed as η × V / P was between 0.08 × 10 -9 and 0.30 × 10 -9 inclusive, the chlorine concentration was between 120 × 10 10 atoms / cm 2 and 1,500 × 10 10 atoms / cm 2, inclusive, which was within an appropriate range.On the other hand, as for Example 20 of the present invention in which the load coefficient L was less than 0.08×10 -9 at the surface chlorine concentration of 60×10 10 atoms / cm 2 the chlorine concentration was low. In Example 25 of the present invention in which the load coefficient L was 0.3×10 -9 at a surface concentration of 2,000×10 10 atoms / cm 2 the chlorine concentration was high.Moreover, in Examples 21 to 24, 27, and 28 of the present invention polished in the polishing step such that the surface oxygen concentration was between 4 atomic % and 12 atomic % inclusive and the surface chlorine concentration was between 120×10 10 atoms / cm 2 and 1,500×10 10 atoms / cm 2 inclusive, the gains of the semiconductor device were at least 51%. From these facts, it is understood that, when the oxygen concentration and the chlorine concentration of the compound semiconductor areas are adjusted within these ranges, the surface quality can be advantageously maintained.From the foregoing, it could be confirmed that according to the present invention, with the polishing agent pH between 8.5 and 9.5 inclusive and the redox potential y (mV) satisfying -60×+1.400≤y≤-60x+1.700 at a given pH x, the surface oxygen concentration could be controlled to an appropriate range.Similarly, it could be confirmed that by polishing in a manner in which, at a polishing agent viscosity η (mPa·s), a peripheral velocity V (m / s), and an applied pressure P (kPa), the load coefficient L expressed as η×V / P is between 0.08×10 -9 and 0.30×10 -9 inclusive, the surface chlorine concentration could be controlled to an appropriate range.List of reference characters10: Compound semiconductor; 11: surface, Compound semiconductor surface 20: semiconductor device; 21: epitaxial layer; 22, 23: electrodes.

Claims

A polishing agent for Gaαln(1-α)AsβP(1-β) compound semiconductors (wherein 0 ≤ α ≤ 1; 0 ≤ β ≤ 1), the polishing agent comprising: a carbonate of an alkali metal; an organic salt of an alkali metal; a chlorine-based oxidizing agent; and a phosphate of an alkali metal; wherein the sum of the concentrations of the carbonate of an alkali metal and the organic salt of an alkali metal is between 0.01 mol / L and including 0.02 mol / L, the organic salt of an alkali metal is sodium dicarboxylate, the sodium dicarboxylate is at least one substance selected from the group consisting of sodium tartrate, sodium malate and sodium succinate, and the polishing agent is free of abrasive grains.The polishing agent of claim 1, wherein the carbonate of an alkali metal is sodium carbonate; and the concentration of said sodium carbonate is between 0.008 mol / L and 0.018 mol / L inclusive.The polishing composition of claim 1 or 2, wherein the chlorine-based oxidizing agent is sodium dichloroisocyanurate; and the concentration of said sodium dichloroisocyanurate is between 0.035 mol / L and 0.060 mol / L inclusive.The polishing composition of any one of claims 1 to 3, wherein the phosphate of an alkali metal is sodium tripolyphosphate; and the concentration of said sodium tripolyphosphate is between 0.015 mol / L and 0.025 mol / L inclusive.The polishing agent according to any one of claims 1 to 4, wherein the pH is between 8.5 and 9.5 inclusive; and the redox potential y (mV) when the pH is given as x satisfies -60x +1.400 ≤ y ≤ -60x + 1.700.A compound semiconductor manufacturing method comprising: a step (S1) of preparing a Gaαln(1-α)AsβP(1-β) compound semiconductor (10) (wherein 0 ≤ α ≤ 1; 0 ≤ β ≤ 1); and a polishing step (S2) of polishing a surface (11) of the compound semiconductor (10) using a polishing agent according to any one of claims 1 to 5, wherein the organic salt of an alkali metal is sodium dicarboxylate, the sodium dicarboxylate is at least one substance selected from the group consisting of sodium tartrate, sodium malate and sodium succinate, and the polishing agent is free of abrasive grains.The compound semiconductor manufacturing method according to claim 7, wherein in the polishing step (S2), polishing is performed such that at the Poliermittelviskositätη(mPa·s ), the peripheral velocity V (m / s), and the applied pressure P (kPa), the stress coefficient expressed as η × V / P is between 0.08 × 10 -9 and 0.30 × 10 -9 inclusive.The compound semiconductor manufacturing method according to claim 6 or 7, further comprising a washing step (S3) of the compound semiconductor surface (11) subsequent to the polishing step (S2).The compound semiconductor manufacturing method according to claim 8, wherein in the step (S1) of preparing, GaAs is prepared as the compound semiconductor (10); and by the polishing step (S2) and the washing step (S3), the compound semiconductor (10) is designed to have a surface oxygen concentration between 4 at% and 12 at% inclusive and a surface chlorine concentration between 120×10 10 atoms / cm 2 and 1,500×10 10 atoms / cm 2 inclusive.The compound semiconductor manufacturing method according to claim 8, wherein, by the polishing step (S2) and the washing step (S3), the compound semiconductor (10) is configured to have a surface sulfur concentration that is between 120×10 10 atoms / cm 2 and 1,500×10 10 atoms / cm 2 inclusive.A semiconductor device manufacturing method comprising: a step (S1) of preparing a compound semiconductor (10) manufactured by a compound semiconductor manufacturing method according to any one of claims 6 to 10; and a step (S4) of forming an at least single-laminar epitaxial layer (21) on the compound semiconductor (10).

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