JP2014041911A - Polishing composition, and manufacturing method of compound semiconductor substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compound semiconductor substrate, and a polishing composition which especially enables the high-speed polishing of an InP substrate, and to provide a manufacturing method of the compound semiconductor substrate by use of the polishing composition.SOLUTION: A polishing composition comprises: a fatty acid salt of an alkali metal; colloidal silica; and an oxidizer. The fatty acid salt of the alkali metal has a concentration of 1.7×10-8.6×10mol/kg.

Description

  The present invention relates to a polishing composition suitable for polishing a compound semiconductor substrate and a method for producing a compound semiconductor substrate.

  Since compound semiconductors including indium phosphide (hereinafter also referred to as InP) semiconductors have superior light receiving and emitting functions and heat resistance compared to silicon semiconductors, they constitute semiconductor devices such as laser diodes and solar cells. Widely used as a substrate for growing epitaxial layers.

  In order to grow an epitaxial layer on an InP substrate, it is necessary to mirror polish the surface before the growth. Various polishing compositions are known for use in this polishing. For example, polishing compositions comprising additives such as water, abrasive grains, and surfactants are known (Japanese Patent Application Laid-Open No. 4-291723 (Patent Document 1), Japanese Patent Application Laid-Open No. 2003-100671 (Patent Document). 2), Japanese Patent Application Laid-Open No. 2006-019740 (Patent Document 3), Japanese Patent No. 4126186 (Patent Document 4), Hamamoto et al., “Behavior of Surfactant on Processing Properties in CMP Slurries”, Saitama University Area Journal of Joint Research Center, Vol.2, 23-26 (2001) (Non-Patent Document 1)).

JP-A-4-291723 Japanese Patent Laid-Open No. 2003-100671 JP 2006-019740 A Japanese Patent No. 4126186

Hamamoto et al., “Behavior of Surfactant on Processing Properties in CMP Slurries”, Bulletin of Saitama University Regional Joint Research Center, Vol. 2, 23-26 (2001)

  As described above, in order to use an InP substrate for a semiconductor device, it is required that the surface thereof be a surface having extremely high uniformity and flatness by mirror polishing. However, since the InP substrate is more likely to break on the surface with weak atomic bonding force due to crystal anisotropy than the silicon substrate, the polishing rate (hereinafter also referred to as the polishing rate) cannot be increased during polishing. There was a problem with productivity.

  With the polishing compositions described in Patent Documents 1 to 4 and Non-Patent Document 1, high-speed polishing of InP substrates is difficult, and does not provide a sufficient solution to the above problems. Moreover, the polishing composition described in Patent Document 4 has many blending components, which is not preferable from the viewpoint of raw material procurement and raw material cost.

  The present invention has been made in view of the circumstances as described above, and an object of the present invention is to provide a polishing composition that enables high-speed polishing of a compound semiconductor substrate, particularly an InP substrate, and the polishing. An object of the present invention is to provide a method for producing a compound semiconductor substrate using the composition for use.

  In order to solve the above problems, the present inventors have conducted extensive research on the components constituting the polishing composition. As a result, it is possible to add an alkali metal fatty acid salt to the polishing composition. It is found to be extremely effective for polishing, and when a specific combination is adopted as a compounding component of the polishing composition, high-speed polishing of a compound semiconductor substrate, particularly an InP substrate, can be realized by the interaction of each component. The present invention has been completed.

That is, the polishing composition of the present invention is a polishing composition containing an alkali metal fatty acid salt, colloidal silica, and an oxidizing agent, and the concentration of the alkali metal fatty acid salt is 1.7 ×. 10 ⁻⁴ mol / kg or more and 8.6 × 10 ⁻⁴ mol / kg or less.

  By providing the above configuration, the polishing composition of the present invention can perform high-speed polishing of a compound semiconductor substrate, particularly an InP substrate.

  The alkali metal fatty acid salt is preferably sodium laurate and / or sodium oleate.

  The colloidal silica preferably has an average particle size of 10 nm to 100 nm.

  The oxidizing agent is preferably sodium dichloroisocyanurate and / or potassium dichloroisocyanurate.

  The present invention also relates to a method for producing a compound semiconductor substrate, the method comprising the steps of preparing a compound semiconductor substrate, and polishing the surface of the compound semiconductor substrate using the above polishing composition. And a step of cleaning the surface of the compound semiconductor substrate.

Here, the step of polishing using the polishing composition is a step of polishing by applying a load of 50 g / cm ² or more and 150 g / cm ² or less using the polishing composition and a hard polishing cloth. A method for producing a compound semiconductor substrate is preferred.

  Moreover, it is preferable that the process of grind | polishing using the said polishing composition is a manufacturing method of a compound semiconductor substrate which is a process of grind | polishing both surfaces of the said compound semiconductor substrate.

  The compound semiconductor substrate is preferably an indium phosphide substrate (InP substrate).

  The polishing composition of the present invention can increase the polishing rate, and even when high-speed polishing is performed, the finished quality of the substrate can be adapted to a semiconductor device. In particular, it exhibits an excellent effect in polishing an InP substrate.

It is a flowchart which shows the manufacturing method of the compound semiconductor substrate of this invention. It is a conceptual diagram of the polishing process at the time of using the conventional polishing composition. It is a conceptual diagram of the grinding | polishing process at the time of using the polishing composition of this invention.

Hereinafter, embodiments according to the present invention will be described in more detail.
<Polishing composition>
In the polishing composition of the present invention, colloidal silica is dispersed as abrasive grains in a liquid solvent such as ultrapure water, and an oxidizing agent and an alkali metal fatty acid salt as an additive are dissolved in the liquid solvent. doing. The alkali metal fatty acid salt is contained at a concentration of 1.7 × 10 ⁻⁴ mol / kg or more and 8.6 × 10 ⁻⁴ mol / kg or less. Such a polishing composition can contain any other component as long as it contains the above-mentioned alkali metal fatty acid salt, colloidal silica, and an oxidizing agent. As an arbitrary component, a dispersing agent, a thickener, etc. can be mentioned, for example.

<Alkali metal fatty acid salt>
The polishing composition of the present invention contains an alkali metal fatty acid salt as an additive. And as above-mentioned, this additive needs to be a salt. For example, when a fatty acid is used as an additive, the effect of the present invention cannot be obtained because it is hardly soluble in a solvent such as ultrapure water.

  Here, the alkali metal means an element belonging to Group 1 in the periodic table, that is, lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). Show.

  Moreover, a fatty acid shows the carboxylic acid of a long chain hydrocarbon. The fatty acid may contain a double bond in the long chain or may contain a branched chain. Here, the fatty acid preferably has a hydrophobic group, and preferably has an alkyl group including a main chain having 8 to 18 carbon atoms. Here, the main chain means a long chain having the largest number of carbon atoms in the molecule.

  The alkali metal fatty acid salt refers to a compound containing the alkali metal ion and the fatty acid ion. Examples of such compounds include sodium laurate, potassium laurate, sodium oleate, potassium oleate, sodium caprylate, and potassium caprylate. Among these, sodium laurate, sodium oleate Or these combination is preferable. That is, the alkali metal fatty acid salt is preferably sodium laurate and / or sodium oleate.

The concentration of the fatty acid salt of the alkali metal needs to be 1.7 × 10 ⁻⁴ mol / kg or more and 8.6 × 10 ⁻⁴ mol / kg or less, preferably 3.5 × 10 ⁻⁴ mol. / Kg or more and 8.6 × 10 ⁻⁴ mol / kg or less, more preferably 3.5 × 10 ⁻⁴ mol / kg or more and 4.3 × 10 ⁻⁴ mol / kg or less. . When the concentration of the alkali metal fatty acid salt is less than 1.7 × 10 ⁻⁴ mol / kg, a sufficient polishing rate tends to be not obtained. On the other hand, when the concentration of the alkali metal fatty acid salt exceeds 8.6 × 10 ⁻⁴ mol / kg, the effect tends to be saturated, but it can be added as long as economic efficiency is ignored.

<Colloidal silica>
The polishing composition of the present invention contains colloidal silica as polishing abrasive grains. Here, colloidal silica refers to a colloid of silicon dioxide (SiO ₂ ) particles or hydrates thereof.

  The average particle size of the colloidal silica is preferably 10 nm or more and 100 nm or less, more preferably 50 nm or more and 100 nm or less. If the average particle size is less than 10 nm, it is not preferable from the viewpoint of economy due to a decrease in polishing rate, and if it exceeds 100 nm, it is not preferable from the viewpoint of dispersibility. The average particle diameter of the colloidal silica can be measured by a dynamic light scattering method, a laser diffraction method, a centrifugal sedimentation method, or the like. In the present invention, a value measured by the dynamic light scattering method is adopted. .

  Moreover, 2.0 mass% or more and 10.0 mass% or less are preferable, and, as for content of the said colloidal silica in the polishing composition of this invention, 2.0 mass% or more and 7.0 mass% or less are more preferable. Is preferred. When the colloidal silica content is less than 2.0% by mass, it is not preferable from the viewpoint of economy due to a decrease in the polishing rate, and when it exceeds 10.0% by mass, it is not preferable from the viewpoint of economy due to an increase in usage.

<Oxidizing agent>
The polishing composition of the present invention contains an oxidizing agent. Here, the oxidizing agent is preferably a compound containing a halogen oxoacid ion. Here, as the halogen oxoacid ion, for example, hypochlorite ion, chlorite ion, chlorate ion, perchlorate ion, hypobromite ion, bromate ion, bromate ion, perbromate acid Ion, hypoiodite ion, iodate ion, iodate ion, periodate ion, and the like. Of these, a compound containing a chlorate ion (that is, a chlorine-based oxidant) is more preferable. Here, chlorinated oxidants include not only compounds containing chlorate ions (ClO ⁻ ) such as hypochlorite, but also chloric acid by dissolving in water such as chlorinated isocyanurates. Also included are compounds containing solid materials that generate ions (ClO ⁻ ).

  Examples of the chlorine-based oxidant include sodium dichloroisocyanurate, potassium dichloroisocyanurate, and trichloroisocyanuric acid. From the viewpoint of solubility in a solvent, sodium dichloroisocyanurate and / or dichloroisocyanurate Potassium acid is preferred.

  The concentration of the oxidizing agent in the polishing composition of the present invention is preferably 0.05 mol / kg or more and 0.23 mol / kg or less, more preferably 0.09 mol / kg or more and 0.23 mol / kg or less. It is preferable that

<Method for producing compound semiconductor substrate>
Hereinafter, the manufacturing method of the compound semiconductor substrate of this invention using said polishing composition is demonstrated in detail.

  As shown in FIG. 1, the method for producing a compound semiconductor substrate of the present invention comprises a step of preparing a compound semiconductor substrate, a step of polishing the surface of the compound semiconductor substrate using the above-described polishing composition of the present invention, and And a step of cleaning the surface of the compound semiconductor substrate.

<S1: Step of preparing a compound semiconductor substrate>
In this step (step S1), a compound semiconductor substrate is prepared. First, an ingot of a compound semiconductor is grown by an HB method (horizontal Bridgman method), a VB method (vertical Bridgman method), or the like. The grown ingot is subjected to peripheral processing, slicing, grinding, lapping, polishing, cleaning, and the like to produce a compound semiconductor substrate. Here, in order to improve the flatness of the compound semiconductor substrate, machining such as grinding and lapping may be performed. In order to reduce the roughness and remove the work-affected layer, CMP (chemical mechanical polishing), chemical polishing, or the like may be performed after the processing.

<Compound semiconductor substrate>
The compound semiconductor may be a bulk crystal, or may be a thin film formed on a substrate made of a bulk crystal, for example.

  The polishing composition of the present invention is particularly suitable for polishing an indium phosphide semiconductor substrate (InP substrate) because it can achieve a very good polishing rate and substrate quality after polishing. Therefore, in the compound semiconductor substrate manufacturing method of the present invention, the compound semiconductor substrate is preferably an InP substrate.

<S2: Step of Polishing Surface of Compound Semiconductor Substrate Using Polishing Composition>
Next, in the step of polishing the surface of the compound semiconductor substrate using the polishing composition (step S2), the surface of the compound semiconductor substrate is finish-polished using the polishing composition of the present invention.

<Polishing device>
As the polishing apparatus used in step S2, any conventionally known polishing apparatus can be adopted as a semiconductor substrate polishing apparatus. As such a polishing apparatus, for example, a polishing cloth is pasted on a circular surface plate, a polishing composition is dropped thereon, and the surface plate and the carrier holding the substrate (wafer) rotate together. By doing so (that is, when the substrate moves in a planetary motion), a rotary type polishing apparatus that performs polishing by bringing the substrate into contact with the polishing composition can be used.

  Here, in the compound semiconductor substrate manufacturing method of the present invention, the polishing apparatus is preferably a polishing apparatus capable of double-side polishing.

<Hard polishing cloth>
The abrasive cloth may be made of a foamable resin or a non-foamable resin. Alternatively, a laminated polishing cloth using a nonwoven fabric or urethane foam may be used as the base of the hard polishing layer. In the method for producing a compound semiconductor substrate of the present invention, the polishing cloth is preferably a hard polishing cloth. For example, when the polishing cloth is a polyurethane polishing cloth, the Asker C hardness is 61 degrees or more and 86 degrees or less. It is preferable that the angle is 66 degrees or more and 80 degrees or less. Here, the Asker C hardness can be measured using, for example, a spring-type hardness meter.

<Polishing rate>
For the polishing rate, the thickness of the compound semiconductor substrate before and after processing is measured with a conventionally known film thickness meter, and the amount of change in film thickness (that is, the difference between the thickness before processing and the thickness after processing) is divided by the processing time. Can be calculated.

  And in the manufacturing method of the compound semiconductor substrate of this invention, it is preferable that the said polishing rate is 0.20 micrometer / min or more and 1.00 micrometer / min or less. Furthermore, when the compound semiconductor substrate is an InP substrate, it is preferably 0.30 μm / min or more and 0.60 μm / min or less. For example, when the polishing composition of the present invention is used, a polishing rate of 0.30 μm / min or more and 0.60 μm / min or less can be obtained. When a polishing composition having a polishing rate of less than 0.20 μm / min is used, investment in polishing equipment becomes excessive, which is not preferable from the viewpoint of production cost. In addition, when a polishing composition having a polishing rate exceeding 1.00 μm / min is used, it is difficult to control the thickness, which is not preferable from the viewpoint of substrate quality.

<Load>
In the method for producing a compound semiconductor substrate of the present invention, the step of polishing is a step of polishing by applying a load of 50 g / cm ² or more and 150 g / cm ² or less using a polishing composition and a hard polishing cloth. It is preferable. The load is more preferably 50 g / cm ² or more and 120 g / cm ² or less. Thus, it is possible to apply a relatively low load by using the polishing composition of the present invention. When the polishing composition of the present invention is not used, it is necessary to increase the polishing rate by applying a high load in order to improve tact. In this way, when a high load is applied, the in-plane temperature distribution of the polishing cloth becomes large, which shortens the life of the polishing cloth and increases the frequency of replacement of the polishing cloth. Is not preferable. Further, the partial wear of the polishing cloth is promoted, so that the flatness of the finished substrate is deteriorated, which is not preferable from the viewpoint of substrate quality.

Moreover, the manufacturing method of the compound semiconductor substrate of this invention can be applied to double-sided polishing process by using the polishing composition of this invention and a load being the said range. That is, the polishing step is preferably a step of polishing both surfaces of the compound semiconductor substrate. In the case of double-sided polishing, the edge of the substrate (wafer) that is the object to be polished is in contact with the hole end surface that fixes the wafer, so if the load exceeds 200 g / cm ² , A large stress is generated between the edge of the wafer and the end surface of the hole, and in some cases, vibration is applied to the edge, and a defect occurs in the edge of the wafer. According to the method for producing a compound semiconductor substrate of the present invention, as described above, since the load does not exceed 150 g / cm ² , stable double-side polishing is possible.

<S3: Step of cleaning the surface of the compound semiconductor substrate>
Next, in the step of cleaning the surface of the compound semiconductor substrate (step S3), the polished substrate surface is cleaned. The cleaning method is not particularly limited, and any conventionally known method may be used. For example, bubbling or ultrasonic waves may be applied during cleaning. As the cleaning liquid, for example, pure water, isopropyl alcohol, or the like can be used. For example, an etching liquid such as a choline (2-hydroxyethyltrimethylammonium hydroxide) aqueous solution may be used.

  A compound semiconductor substrate can be manufactured by implementing the above process (step S1-S3).

<Evaluation of compound semiconductor substrate surface>
The object of the present invention is to increase the polishing rate and improve the quality of the finished substrate. Here, in order for the epitaxial layer to be able to grow on the substrate (that is, to have epi-ready quality), (A) “the number of fine particles of 0.265 μm or more” is 100 / wafer or less as the finished quality of the substrate. Yes, (B) Surface micro-roughness and defects (hereinafter also referred to as “HAZE”) are 3.0 ppm or less, (C) “TTV (Total Thickness Variation)” is 10 μm or less, and (D) “D” It is required that “WARP” is 10 μm or less.

  Here, the above (A) and (B) can be measured by a foreign matter inspection apparatus using a light scattering method, and the above (C) and (D) can be measured by an optical flatness measuring apparatus. Can be measured.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Example 1>
<Preparation of polishing composition>
10.5 g of granular sodium laurate was added to 200 mL of ultrapure water at 50 ° C. and stirred to prepare a 0.22 mol / kg dilute sodium laurate solution.

  Next, 45 g of sodium dichloroisocyanurate as an oxidizing agent was added to 4.5 L of ultrapure water and stirred for 5 minutes using a stirrer. After stirring for 5 minutes, it was visually confirmed that sodium dichloroisocyanurate was completely dissolved in ultrapure water.

  Next, 500 mL of colloidal silica having an average particle diameter of 80 nm and a silica concentration of 40.5% by mass and 10 mL of the above diluted sodium laurate solution are added to ultrapure water in which sodium dichloroisocyanurate is dissolved. Then, the polishing composition of Example 1 was obtained by further stirring for 5 minutes.

The polishing composition of Example 1 has a sodium laurate concentration of 4.3 × 10 ⁻⁴ mol / kg, a colloidal silica content of 5.0 mass%, and a sodium dichloroisocyanurate concentration. Was 0.12 mol / kg.

<Preparation of polishing equipment>
First, a polyurethane polishing cloth was prepared. When the Asker C hardness of this polyurethane polishing cloth was measured with a spring type hardness meter, it was 62 to 72 degrees. Next, the polyurethane polishing cloth was affixed to an upper surface plate and a lower surface plate of a CMP apparatus capable of double-side polishing. Next, a carrier on which diamond pellets were attached was set, and dressing treatment was performed for 20 minutes while supplying pure water on a surface plate to remove dirt on the surface of the polishing cloth and make fuzz uniform.

<InP substrate polishing>
Four glass epoxy carriers on which three circular substrates (wafers) can be set were set on the surface plate of the CMP apparatus, and three InP single crystal circular substrates (thickness: 730 μm) were set on each carrier ( That is, 12 InP single crystal circular substrates were set).

The upper surface plate was placed on the carrier, and the pressure was adjusted so that the load was 100 g / cm ² . Then, the relative speed between the substrate surface and the upper and lower surface plates was set to 20 rpm, and polishing was performed for 90 minutes while supplying the polishing composition of Example 1 at 300 mL / min.

<Evaluation of polishing rate>
The substrate thickness before and after polishing was measured using a non-contact laser displacement sensor, and the polishing rate was calculated. The results are shown in Table 1.

<Examination of alkali metal fatty acid salt concentration>
<Examples 2 to 4 and Comparative Example 1>
The polishing compositions of Examples 2 to 4 and Comparative Example 1 were obtained in the same manner as in Example 1 except that the concentration of sodium laurate in the polishing composition was changed to the concentration shown in Table 1. Then, using the polishing compositions of Examples 2 to 4 and Comparative Example 1, the InP single crystal substrate was polished in the same manner as in Example 1, and the polishing rate was calculated. The results are shown in Table 1.

<Examination of additive types>
<Example 5 and Comparative Examples 2-6>
Polishing compositions of Example 5 and Comparative Examples 2 to 6 were obtained in the same manner as Example 1 except that the combination of additives and liquid solvent shown in Table 1 was used instead of sodium laurate. .

  In the polishing compositions of Comparative Examples 2 to 4, each additive (Comparative Example 2: caprylic acid, Comparative Example 3: pelargonic acid, Comparative Example 4: capric acid) was added to the liquid solvent and stirred. However, the additive was hardly dissolved. Furthermore, as a comparative test, the liquid solvent was ultrapure water at 50 ° C., and stirring was similarly performed, but the additive was hardly dissolved.

  Then, using the polishing compositions of Example 5 and Comparative Examples 2 to 6, the InP single crystal substrate was polished in the same manner as in Example 1, and the polishing rate was calculated. The results are shown in Table 1.

<Example 6>
In the preparation of the polishing composition of Example 1, the same procedure as in Example 1 was carried out except that 40 g (0.05 mol / kg) of sodium sulfate was added simultaneously with sodium dichloroisocyanurate and dissolved in ultrapure water. The polishing composition of Example 6 was obtained.

  Then, using the polishing composition of Example 6, the InP single crystal substrate was polished in the same manner as in Example 1, and the polishing rate was calculated. The results are shown in Table 1.

As is apparent from Table 1, the polishing composition of the present invention is a polishing composition containing an alkali metal fatty acid salt, colloidal silica, and an oxidizing agent, and the concentration of the alkali metal fatty acid salt. Was 1.7 × 10 ⁻⁴ mol / kg or more and 8.6 × 10 ⁻⁴ mol / kg or less, and it was confirmed that the polishing rate could be increased.

  Here, in Comparative Examples 5 and 6 in which fatty acid is dissolved in alcohol, the polishing rate is improved although the effect is small. However, it is not preferable to use an organic solvent in view of the deterioration of the working environment and the increase in management costs in the production process.

  Further, from the comparison between Examples 1 and 6, it was confirmed that even when sodium sulfate was added, there was no difference in the polishing rate, and the addition of the inorganic salt had a small effect on the polishing rate.

  Although the details of the cause of the effects of the present invention are unclear, the mechanism of action expected by the present inventors will be described with reference to FIGS. FIG. 2 shows a conceptual diagram of polishing processing when no additive is used (that is, a conceptual diagram of polishing processing when the conventional polishing composition 103 is used). As shown in FIG. 2, a part of the colloidal silica 4 supplied on the polishing pad 2 contributes to the polishing by adhering to the substrate 1, and the other is discharged out of the system without contributing to the polishing. That is, only the adhered colloidal silica 4 attached to the substrate contributes to polishing.

  FIG. 3 shows a conceptual diagram of polishing when an alkali metal fatty acid salt is used as an additive (that is, a conceptual diagram of polishing when the polishing composition 3 of the present invention is used). Alkali metal fatty acid salts bind to the surface of the InP substrate and make the surface hydrophobic. For this reason, the colloidal silica 4 is easily adsorbed on the surface of the InP substrate. As a result, since the amount of colloidal silica 4 that can contribute to polishing in the supplied colloidal silica 4 increases, it is estimated that the polishing rate can be increased.

  Furthermore, after polishing one side of the 12 InP single crystal substrates mirror-polished using the polishing compositions of Examples 1 and 6 with a suede polishing cloth, the substrate was cleaned using a cleaning solution comprising an aqueous choline solution. Residues and fine particles of the polishing composition on the surface were removed.

  After drying the substrate, using a foreign matter inspection apparatus (product name “Surfscan 6220”, manufactured by KLA Tencor) using a light scattering method, (A) “number of fine particles of 0.265 μm or more” and (B) “HAZE” was evaluated. The results are shown in Table 2.

  Furthermore, (C) “TTV” and (D) “WARP” were evaluated using an optical flatness measuring device (product name “Ultra Sort”, manufactured by Corning Toropel). The results are shown in Table 2.

  In Table 2, the numerical values shown in each column indicate the average value of 12 substrates.

  As is apparent from Table 2, the method for producing a compound semiconductor substrate of the present invention includes a step of polishing using the polishing composition according to the examples of the present invention, thereby increasing the polishing rate. It was confirmed that a compound semiconductor substrate having a surface quality capable of forming an epitaxial layer was possible.

  Moreover, the improvement effect was not seen in Example 6 which added the inorganic salt compared with Example 1. FIG.

  Although the embodiments and examples of the present invention have been described as described above, it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 substrate (wafer), 2 polishing cloth, 3,103 polishing composition, 4 colloidal silica.

Claims (8)

A polishing composition comprising an alkali metal fatty acid salt, colloidal silica, and an oxidizing agent,
The polishing composition, wherein the concentration of the alkali metal fatty acid salt is 1.7 × 10 ⁻⁴ mol / kg or more and 8.6 × 10 ⁻⁴ mol / kg or less.   The polishing composition according to claim 1, wherein the alkali metal fatty acid salt is sodium laurate and / or sodium oleate.   The polishing composition according to claim 1, wherein the colloidal silica has an average particle size of 10 nm or more and 100 nm or less.   The polishing composition according to claim 1, wherein the oxidizing agent is sodium dichloroisocyanurate and / or potassium dichloroisocyanurate. Preparing a compound semiconductor substrate;
Polishing the surface of the compound semiconductor substrate with the polishing composition according to any one of claims 1 to 4,
And a step of cleaning the surface of the compound semiconductor substrate. The compound semiconductor substrate according to claim 5, wherein the polishing step is a step of applying a load of 50 g / cm ² or more and 150 g / cm ² or less using the polishing composition and a hard polishing cloth. Manufacturing method.   The method of manufacturing a compound semiconductor substrate according to claim 6, wherein the polishing step is a step of polishing both surfaces of the compound semiconductor substrate.   The method of manufacturing a compound semiconductor substrate according to claim 5, wherein the compound semiconductor substrate is an indium phosphide substrate.

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