Patent Grant
9238755
The present invention relates to a polishing composition to be used for polishing an object including a portion containing a high-mobility material (hereinafter, also referred to as a high-mobility material portion), such as a group IV material and a group III-V compound, and a portion containing a silicon material (hereinafter, also referred to as a silicon material portion), such as silicon oxide. The present invention also relates to a polishing method and substrate production method using the polishing composition.
High-mobility channel materials, which are capable of improving the carrier mobility of transistors, have been studied as a means of reducing power consumption and improving performance (operating characteristic) of a transistor. Improving the carrier transport property of a channel increases the drain current flowing when the channel is in ON-state, thereby allowing the power supply voltage to be decreased while obtaining a sufficient ON-state current. This combination brings about higher MOSFET performance at low electric power.
Group III-V compounds, such as gallium arsenide (GaAs), group IV materials, such as silicon germanium (SiGe) and germanium (Ge), and graphene, which consists of only carbon (C), have higher electron and hole mobility than that of silicon and an excellent carrier transport property, and are expected to be used as the high-mobility channel material. Particularly, a channel using a group IV material, which is easier in introduction than a group III-V compound, is positively studied. There is as yet no established technique for growing a group III-V compound channel with high crystallinity and controlling the channel to have a desired shape. Also, the group III-V compound channel has no advantage in terms of cost over the channel using a group IV material.
A high-mobility material channel can be formed by polishing an object including a high-mobility material portion and a silicon material portion. In this case, when a polishing composition is used that can polish the high-mobility material portion with higher selectivity over the silicon material portion, the high-mobility material portion can be efficiently polished and removed. Also, since loss of oxide such as silicon oxide is decreased, a withstand voltage between wiring layers is secured. Further, in a subsequent photolithography process, the decreased loss of oxide facilitates focusing of the exposure light, thereby stabilizing the process (see Patent Document 1). However, a polishing composition described in, for example, Patent Document 2 or 3 and conventionally used for polishing a compound semiconductor substrate consisting of only a group IV compound does not, when used for polishing an object including a high-mobility material portion and a silicon material portion, exhibit sufficiently high polishing selectivity for the high-mobility material portion.
Patent Document 1: Japanese Laid-Open Patent Publication No. 11-204520
Patent Document 2: Japanese Laid-Open Patent Publication No. 2010-130009
Patent Document 3: Japanese National Phase Laid-Open Patent Publication No. 2010-519740
Accordingly, it is an objective of the present invention to provide a polishing composition that can, when used for polishing an object including a high-mobility material portion and a silicon material portion, exhibit high polishing selectivity for the high-mobility material portion and to provide a polishing method and substrate production method using the polishing composition.
In order to achieve the above-mentioned objective and in accordance with a first aspect of the present invention, provided is a polishing composition to be used for polishing an object including a high-mobility material portion and a silicon material portion. The polishing composition contains an oxidizing agent and abrasive grains having an average primary particle diameter of 40 nm or less.
The polishing composition preferably further contains a hydrolysis-suppressing compound that bonds to a surface OH group of the silicon material portion to function to suppress hydrolysis of the silicon material portion.
In accordance with a second aspect of the present invention, provided is a polishing composition to be used for polishing an object including a high-mobility material portion and a silicon material portion. The polishing composition contains abrasive grains, an oxidizing agent, and a hydrolysis-suppressing compound that bonds to a surface OH group of the silicon material portion to function to suppress hydrolysis of the silicon material portion.
The polishing compositions of the first and second aspects preferably have a neutral pH.
In accordance with a third aspect of the present invention, provided is a method for polishing an object including a high-mobility material portion and a silicon material portion with the polishing composition of the first or second aspect.
In accordance with a fourth aspect of the present invention, provided is a method for producing a substrate by polishing an object including a high-mobility material portion and a silicon material portion with the polishing composition of the first or second aspect.
The present invention succeeds in providing a polishing composition that can, when used for polishing an object including a high-mobility material portion and a silicon material portion, exhibit high polishing selectivity for the high-mobility material portion, and a polishing method and substrate production method using the polishing composition.
A first embodiment of the present invention will be described below.
A polishing composition of the present embodiment is prepared by mixing specific abrasive grains and an oxidizing agent with water. Therefore, the polishing composition contains a specific abrasive grains and an oxidizing agent.
The polishing composition is used for polishing an object including a high-mobility material portion and a silicon material portion, and specifically for the purpose of selectively polishing a high-mobility material portion in an application for polishing the object to produce a substrate. A high-mobility material as referred to herein means a material having higher electron or hole mobility than that of a silicon material. Examples of the high-mobility material include group III-V compounds, such as gallium phosphide (GaP), indium phosphide (InP), gallium arsenide (GaAs), indium arsenide (InAs), and indium antimonide (InSb), and group IV group materials, such as silicon germanium (SiGe) and germanium (Ge). Examples of the silicon material include polysilicon, silicon oxide, and silicon nitride. For example, the silicon material has an electron mobility of 1,600 cm2/V·s and a hole mobility of 430 cm2/V·s. By contrast, the high-mobility material, that is, indium phosphide has an electron mobility of 5,400 cm2/V·s and a hole mobility of 200 cm2/V·s, gallium arsenide has an electron mobility of 8,500 cm2/V·s and a hole mobility of 400 cm2/V·s, indium arsenide has an electron mobility of 40,000 cm2/V·s and a hole mobility of 500 cm2/V·s; indium antimonide has an electron mobility of 77,000 cm2/V·s and a hole mobility of 850 cm2/V·s, and germanium has an electron mobility of 3,900 cm2/V·s and a hole mobility of 1,900 cm2/V·s. The high-mobility material has at least one of electron mobility and hole mobility values significantly higher than that of the silicon material.
(Abrasive Grains)
The abrasive grains contained in the polishing composition have an average primary particle diameter of 40 nm or less. When the abrasive grains having a small average primary particle diameter of 40 nm or less are used, the polishing rate of the silicon material portion with the polishing composition is advantageously much lower than the polishing rate of the high-mobility material portion with the polishing composition as compared with the case where abrasive grains having an average primary particle diameter of more than 40 nm are used. The value of the average primary particle diameter of the abrasive grains can be calculated, for example, based on the specific surface area of the abrasive grains measured by the BET method.
The abrasive grains in the polishing composition may be any of inorganic particles and organic particles. Specific examples of inorganic particles include particles made of a metal oxide, such as silica, alumina, ceria, and titania. Specific examples of organic particles include polymethyl methacrylate (PMMA) particles. Among them, silica particles are preferable, and colloidal silica is particularly preferable.
The content of the abrasive grains in the polishing composition is preferably 20% by mass or less, more preferably 15% by mass or less, and still more preferably 10% by mass or less. As the abrasive grain content decreases, the material cost of the polishing composition can be reduced, and additionally, the aggregation of the abrasive grains is less likely to occur.
The average secondary particle diameter of the abrasive grains is preferably 170 nm or less, more preferably 150 nm or less, and still more preferably 120 nm or less. As the average secondary particle diameter of the abrasive grains decreases, a polished surface with fewer scratches is easily obtained by polishing the object with the polishing composition. The value of the average secondary particle diameter of the abrasive grains can be measured, for example, by a laser light scattering method.
(Oxidizing Agent)
Although the type of the oxidizing agent contained in the polishing composition is not particularly limited, the oxidizing agent preferably has a standard electrode potential of 0.3 V or more. When an oxidizing agent having a standard electrode potential of 0.3 V or more is used, the polishing rate of the high-mobility material portion with the polishing composition is advantageously enhanced as compared with when an oxidizing agent having a standard electrode potential of less than 0.3 V is used. Specific examples of an oxidizing agent having a standard electrode potential of 0.3 V or more include hydrogen peroxide, sodium peroxide, barium peroxide, an organic oxidizing agent, ozone water, a silver (II) salt, an iron (III) salt, permanganic acid, chromic acid, dichromic acid, peroxodisulfuric acid, peroxophosphoric acid, peroxosulfuric acid, peroxoboric acid, performic acid, peracetic acid, perbenzoic acid, perphthalic acid, hypochlorous acid, hypobromous acid, hypoiodous acid, chloric acid, chlorous acid, perchloric acid, bromic acid, iodic acid, periodic acid, sulfuric acid, persulfuric acid, citric acid, dichloroisocyanuric acid, and salts thereof. Among them, hydrogen peroxide, ammonium persulfate, hypochlorous acid, periodic acid, and sodium dichloroisocyanurate are preferable since the polishing rate of the high-mobility material portion with the polishing composition is greatly enhanced.
The standard electrode potential is represented by the following formula when all chemical species participating in an oxidation reaction are in a normal state:
E0=−ΔG0/nF=(RT/nF)ln K
where E0 is a standard electrode potential, ΔG0 is standard Gibbs energy change of the oxidation reaction, K is a parallel constant thereof, F is a Faraday constant, T is an absolute temperature, and n is the number of electrons participating in the oxidation reaction. Therefore, since the standard electrode potential fluctuates with a temperature, a standard electrode potential at 25° C. is utilized in the present specification. The standard electrode potential of an aqueous solution system is described in, for example, Handbook of Chemistry (fundamental part) II, revised 4th edition, pp. 464-468 (edited by the Chemical Society of Japan).
The content of the oxidizing agent in the polishing composition is preferably 0.01 mol/L or more, and more preferably 0.1 mol/L or more. As the oxidizing agent content increases, the polishing rate of the high-mobility material portion with the polishing composition is enhanced.
The content of the oxidizing agent in the polishing composition is also preferably 100 mol/L or less, and more preferably 50 mol/L or less. As the oxidizing agent content decreases, the material cost of the polishing composition can be reduced, and additionally, the burden of treating the polishing composition after use in polishing, that is, the burden of waste liquid treatment can be reduced.
(pH Adjusting Agent)
The pH of the polishing composition is preferably neutral. More specifically, the pH is preferably within a range of 5 or more and 9 or less. When the pH is neutral, the polishing rate of the silicon material portion with the polishing composition is advantageously reduced.
A pH adjusting agent may be used to adjust the pH of the polishing composition to a desired value. The pH adjusting agent to be used may be any of an acid and an alkali. The pH adjusting agent may be any of inorganic and organic compounds.
According to the present embodiment, the following advantages are obtained.
A second embodiment of the present invention will be described below.
A polishing composition of the second embodiment is prepared by mixing abrasive grains, an oxidizing agent, and a hydrolysis-suppressing compound with water. Therefore, the polishing composition contains abrasive grains, an oxidizing agent, and a hydrolysis-suppressing compound.
Like the polishing composition of the first embodiment, the polishing composition of the second embodiment is used for polishing an object including a portion containing a high-mobility material, such as gallium phosphide, indium phosphide, gallium arsenide, indium arsenide, indium antimonide, silicon germanium, and germanium, and a portion containing a silicon material, such as silicon oxide, and specifically for the purpose of selectively polishing a high-mobility material portion in an application for polishing the object to produce a substrate.
(Abrasive Grains)
The abrasive grains contained in the polishing composition of the second embodiment do not need to have an average primary particle diameter of 40 nm or less. Except for this difference, the abrasive grains are the same as the abrasive grains contained in the polishing composition of the first embodiment.
(Oxidizing Agent)
The oxidizing agent contained in the polishing composition of the second embodiment is the same as the oxidizing agent contained in the polishing composition of the first embodiment.
(Hydrolysis-Suppressing Compound)
The hydrolysis-suppressing compound contained in the polishing composition of the second embodiment bonds to a surface OH group of the silicon material portion to function to suppress the hydrolysis of the silicon material portion. In detail, a hydrogen bond is considered to be formed between a surface OH group of the silicon material portion and an oxygen atom contained in the hydrolysis-suppressing compound. Also, a hydrogen bond is considered to be formed between a surface OH group of the silicon material portion and a nitrogen atom contained in the hydrolysis-suppressing compound. Therefore, when the hydrolysis-suppressing compound is used, the polishing rate of the silicon material portion with the polishing composition is advantageously reduced. In light of the mechanism mentioned above, the hydrolysis-suppressing compound is preferably a compound having an oxygen atom or a compound having a nitrogen atom. Specific examples of the hydrolysis-suppressing compound having an oxygen atom include alcohols, such as 1-propanol, 2-propanol, 2-propyn-1-ol, allyl alcohol, ethylene cyanohydrin, 1-butanol, 2-butanol, (S)-(+)-2-butanol, 2-methyl-1-propanol, t-butyl alcohol, perfluoro-t-butyl alcohol, crotyl alcohol, 1-pentanol, 2,2-dimethyl-1-propanol, 2-methyl-2-butanol, 3-methyl-1-butanol, S-amyl alcohol, 1-hexanol, 4-hydroxy-4-methyl-2-pentanone, 4-methyl-2-pentanol, cyclohexanol, DL-3-hexyl alcohol, 1-heptanol, 2-ethyl hexyl alcohol, (S)-(+)-2-octanol, 1-octanol, DL-3-octyl alcohol, 2-hydroxybenzyl alcohol, 2-nitrobenzyl alcohol, 3,5-dihydroxybenzyl alcohol, 3,5-dinitrobenzyl alcohol, 3-fluorobenzyl alcohol, 3-hydroxybenzyl alcohol, 4-fluorobenzyl alcohol, 4-hydroxybenzyl alcohol, benzyl alcohol, m-(trifluoromethyl)benzyl alcohol, m-aminobenzyl alcohol, m-nitrobenzyl alcohol, o-aminobenzyl alcohol, o-hydroxybenzyl alcohol, p-hydroxybenzyl alcohol, p-nitrobenzyl alcohol, 2-(p-fluorophenyl)ethanol, 2-aminophenethyl alcohol, 2-methoxybenzyl alcohol, 2-methyl-3-nitrobenzyl alcohol, 2-methyl benzyl alcohol, 2-nitrophenethyl alcohol, 2-phenyl ethanol, 3,4-dimethyl benzyl alcohol, 3-methyl-2-nitrobenzyl alcohol, 3-methyl-4-nitrobenzyl alcohol, 3-methyl benzyl alcohol, 4-fluorophenethyl alcohol, 4-hydroxy-3-methoxybenzyl alcohol, 4-methoxybenzyl alcohol, 4-methyl-3-nitrobenzyl alcohol, 5-methyl-2-nitrobenzyl alcohol, DL-α-hydroxyethyl benzene, o-(trifluoromethyl)benzyl alcohol, p-(trifluoromethyl)benzyl alcohol, p-aminophenethyl alcohol, p-hydroxyphenyl ethanol, p-methylbenzyl alcohol, S-phenethyl alcohol, and acetyleneglycol; phenols, such as 4-methylphenol, 4-ethylphenol, and 4-propylphenol; glycols, such as ethylene glycol, propylene glycol, caprylyl glycol, butylene glycol, and acetylenediol; glucamines, such as n-decanol-n-methyl-D-glucamine, n-octanoyl-n-methyl-D-glucamine, and n-nonaynol-n-methyl-D-glucamine; esters, such as glycerin ester, sorbitan ester, methoxyacetic acid, ethoxyacetic acid, 3-ethoxypropionic acid, polyoxyethylene (hereinafter, referred to as POE) sorbitan fatty acid ester, POE glycol fatty acid ester, POE hexitan fatty acid ester, and alanine ethyl ester; ethers, such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyethylene glycol alkyl ether, polyethylene glycol alkenyl ether, alkyl polyethylene glycol, alkyl polyethylene glycol alkyl ether, alkyl polyethylene glycol alkenyl ether, alkenyl polyethylene glycol, alkenyl polyethylene glycol alkyl ether, alkenyl polyethylene glycol alkenyl ether, polypropylene glycol alkyl ether, polypropylene glycol alkenyl ether, alkyl polypropylene glycol, alkyl polypropylene glycol alkyl ether, alkyl polypropylene glycol alkenyl ether, alkenyl polypropylene glycol, alkenyl polypropylene glycol alkyl ether, alkenyl polypropylene glycol alkenyl ether, POE alkylene diglyceryl ether, POE alkyl ether, POE alkyl phenyl ether, and POE polypropylene alkyl ether; and a block/random copolymer of polyoxypropylene/polyoxyethylene.
Specific examples of the hydrolysis-suppressing compound having a nitrogen atom include water-soluble alkylamines, such as bishexamethylenetriamine (BHMT), tetramethylammonium hydroxide (TMAH), tetramethylamine (TMA), tetraethylamine (TEA), dimethylamine, trimethylamine, triethylamine, propylenediamine, methylamine, ethylamine, piperazine, and piperidine; amino alcohols, such as choline hydroxide (CH), triethanolamine, diethanolamine, and ethanolamine; and water-soluble amine compounds, such as ethylenediaminetetraacetic acid (EDTA), sodium diethyldithiocarbamate, and chitosan.
The content of the hydrolysis-suppressing compound in the polishing composition is preferably 10 ppm by mass or more, and more preferably 50 ppm by mass or more. As the hydrolysis-suppressing compound content increases, the polishing rate of the silicon material portion with the polishing composition is reduced.
The content of the hydrolysis-suppressing compound in the polishing composition is also preferably 100,000 ppm by mass or less, and more preferably 50,000 ppm by mass or less. As the hydrolysis-suppressing compound content decreases, the material cost of the polishing composition can be reduced, and additionally, the burden of treating the polishing composition after use in polishing, that is, the burden of waste liquid treatment can be reduced.
(pH Adjusting Agent)
Like the polishing composition of the first embodiment, the pH of the polishing composition of the second embodiment is preferably neutral, and more specifically within a range of 5 or more and 9 or less. When the pH is neutral, the polishing rate of the silicon material portion with the polishing composition is advantageously reduced.
A pH adjusting agent may be used to adjust the pH of the polishing composition of the second embodiment to a desired value. The pH adjusting agent to be used may be any of an acid and an alkali. The pH adjusting agent may be any of inorganic and organic compounds.
According to the second embodiment, the following advantages are obtained.
The embodiments described above may be modified as follows.
Next, examples of the present invention and comparative examples will be described.
Polishing compositions of Examples 101 to 117 and Comparative Examples 101 and 102 were prepared by mixing colloidal silica and an oxidizing agent, and a hydrolysis-suppressing compound and a pH adjusting agent as required, with water. The details of the components in each of the polishing compositions and the results obtained by measuring the pH of each polishing composition are shown in Table 1.
In Table 1, “H2O2” represents hydrogen peroxide and “APS” represents ammonium persulfate. Acetic acid or potassium hydroxide was used as the pH adjusting agent.
The values of polishing rates obtained when the surfaces of a silicon germanium blanket wafer, germanium blanket wafer, and tetraethyl orthosilicate (TEOS) blanket wafer are polished under the conditions shown in Table 2 with each of the polishing compositions of Examples 101 to 117 and Comparative Examples 101 and 102 are shown in the columns entitled “polishing rate of SiGe”, “polishing rate of Ge”, and “polishing rate of TEOS”, respectively, of Table 3. The value of the polishing rate of the TEOS blanket wafer was obtained by dividing by polishing time the difference between the thicknesses of the wafer before and after polishing measured using an optical interferometric film thickness measurement apparatus. The value of the polishing rate of the silicon germanium blanket wafer and the value of the polishing rate of the germanium were obtained by dividing by the density and polishing time the difference between the weights of each of the wafers before and after polishing. The value obtained by dividing the thus obtained polishing rate of silicon germanium with each of the polishing compositions of Examples 101 to 117 and Comparative Examples 101 and 102 by the thus obtained polishing rate of TEOS with the same polishing composition is shown in the column entitled “polishing rate of SiGe/polishing rate of TEOS” of Table 3. The value obtained by dividing the thus obtained polishing rate of germanium with each polishing composition by the thus obtained polishing rate of TEOS with the same polishing composition is shown in the column entitled “polishing rate of Ge/polishing rate of TEOS” of Table 3.
The acceptable level of the polishing rate of TEOS is 300 Å/min or less, more preferably 200 Å/min or less, and still more preferably 100 Å/min or less. The acceptable level of the value obtained by dividing the polishing rate of silicon germanium by the polishing rate of TEOS is 5 or more, more preferably 10 or more, and still more preferably 15 or more. The acceptable level of the value obtained by dividing the polishing rate of germanium by the polishing rate of TEOS is 10 or more.
As shown in Table 3, in the case of the polishing compositions of Examples 101 to 117, the value obtained by dividing the polishing rate of silicon germanium by the polishing rate of TEOS was 5 or more, or the value obtained by dividing the polishing rate of germanium by the polishing rate of TEOS was 10 or more. The obtained results are at a level that can be satisfactorily used for the purpose of selectively polishing the high-mobility material portion. Particularly, in Examples 101, 103, and 105 to 116, in which the pH is adjusted to 7, both the value obtained by dividing the polishing rate of silicon germanium by the polishing rate of TEOS and the value obtained by dividing the polishing rate of germanium by the polishing rate of TEOS were 10 or more, which is a particularly favorable result.
On the other hand, in the case of the polishing composition of Comparative Example 101, the value obtained by dividing the polishing rate of silicon germanium by the polishing rate of TEOS was less than 5 and was below the acceptable level. The obtained result is not at a level that can be satisfactorily used for the purpose of selectively polishing the high-mobility material portion.
Polishing compositions of Examples 201 to 216 and Comparative Example 201 were prepared by mixing colloidal silica and an oxidizing agent, and a hydrolysis-suppressing compound and a pH adjusting agent as required, with water. The details of the components in each of the polishing compositions and the results obtained by measuring the pH of each polishing composition are shown in Table 4.
In Table 4, “H2O2” represents hydrogen peroxide, “APS” represents ammonium persulfate, and “KOH” represents potassium hydroxide.
The values of polishing rates obtained when the surfaces of a gallium arsenide blanket wafer and tetraethyl orthosilicate (TEOS) blanket wafer are polished under the conditions shown in Table 5 with each of the polishing compositions of Examples 201 to 216 and Comparative Example 201 are shown in the columns entitled “polishing rate of GaAs” and “polishing rate of TEOS”, respectively, of Table 6. The value of the polishing rate of the TEOS blanket wafer was obtained by dividing by polishing time the difference between the thicknesses of the wafer before and after polishing measured using an optical interferometric film thickness measurement apparatus. The value of the polishing rate of the gallium arsenide blanket wafer was obtained by dividing by the density and polishing time the difference between the weights of the wafer before and after polishing. The value obtained by dividing the thus obtained polishing rate of gallium arsenide with each of the polishing compositions of Examples 201 to 216 and Comparative Example 201 by the thus obtained polishing rate of TEOS with the same polishing composition is shown in the column entitled “polishing rate of GaAs/polishing rate of TEOS” of Table 6.
The acceptable level of the polishing rate of TEOS is 300 Å/min or less, more preferably 200 Å/min or less, and still more preferably 100 Å/min or less. The acceptable level of the value obtained by dividing the polishing rate of gallium arsenide by the polishing rate of TEOS is 5 or more, more preferably 10 or more, and still more preferably 15 or more.
As shown in Table 6, in the case of the polishing compositions of Examples 201 to 216, the polishing rate of TEOS was 100 Å/min or less, or the value obtained by dividing the polishing rate of gallium arsenide by the polishing rate of TEOS was 15 or more. The obtained results are at a level that can be satisfactorily used for the purpose of selectively polishing the high-mobility material portion.
On the other hand, in the case of the polishing composition of Comparative Example 201, the value obtained by dividing the polishing rate of gallium arsenide by the polishing rate of TEOS was below the acceptable level. The obtained result is not at a level that can be satisfactorily used for the purpose of selectively polishing the high-mobility material portion.
| Number | Date | Country | Kind |
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| 2012-061154 | Mar 2012 | JP | national |
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| PCT/JP2012/080219 | 11/21/2012 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2013/077369 | 5/30/2013 | WO | A |
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