WO2014112430A1 - シリコンエッチング液およびエッチング方法並びに微小電気機械素子 - Google Patents
シリコンエッチング液およびエッチング方法並びに微小電気機械素子 Download PDFInfo
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- WO2014112430A1 WO2014112430A1 PCT/JP2014/050279 JP2014050279W WO2014112430A1 WO 2014112430 A1 WO2014112430 A1 WO 2014112430A1 JP 2014050279 W JP2014050279 W JP 2014050279W WO 2014112430 A1 WO2014112430 A1 WO 2014112430A1
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- WIPO (PCT)
- Prior art keywords
- thiouracil
- silicon
- etching
- methyl
- silicon etching
- Prior art date
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- 238000005530 etching Methods 0.000 title claims abstract description 163
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 76
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 75
- 239000010703 silicon Substances 0.000 title claims abstract description 75
- 238000000034 method Methods 0.000 title claims abstract description 31
- 239000007788 liquid Substances 0.000 title claims abstract description 13
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims abstract description 40
- UMGDCJDMYOKAJW-UHFFFAOYSA-N thiourea group Chemical group NC(=S)N UMGDCJDMYOKAJW-UHFFFAOYSA-N 0.000 claims abstract description 36
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 33
- 150000001923 cyclic compounds Chemical class 0.000 claims abstract description 29
- AVXURJPOCDRRFD-UHFFFAOYSA-N Hydroxylamine Chemical compound ON AVXURJPOCDRRFD-UHFFFAOYSA-N 0.000 claims abstract description 24
- 229910021421 monocrystalline silicon Inorganic materials 0.000 claims abstract description 19
- 125000000962 organic group Chemical group 0.000 claims abstract description 6
- 229920006395 saturated elastomer Polymers 0.000 claims abstract description 6
- 150000008044 alkali metal hydroxides Chemical class 0.000 claims description 10
- NVHNGVXBCWYLFA-UHFFFAOYSA-N 1,3-diazinane-2-thione Chemical compound S=C1NCCCN1 NVHNGVXBCWYLFA-UHFFFAOYSA-N 0.000 claims description 8
- RVBUGGBMJDPOST-UHFFFAOYSA-N 2-thiobarbituric acid Chemical compound O=C1CC(=O)NC(=S)N1 RVBUGGBMJDPOST-UHFFFAOYSA-N 0.000 claims description 8
- PDQAZBWRQCGBEV-UHFFFAOYSA-N Ethylenethiourea Chemical compound S=C1NCCN1 PDQAZBWRQCGBEV-UHFFFAOYSA-N 0.000 claims description 8
- ZEMGGZBWXRYJHK-UHFFFAOYSA-N thiouracil Chemical compound O=C1C=CNC(=S)N1 ZEMGGZBWXRYJHK-UHFFFAOYSA-N 0.000 claims description 8
- -1 thioba Vital Chemical compound 0.000 claims description 6
- OZOSSJWZNHBBDV-UHFFFAOYSA-N 1,3,5-trimethyl-2-sulfanylidene-1,3-diazinane-4,6-dione Chemical compound CC1C(=O)N(C)C(=S)N(C)C1=O OZOSSJWZNHBBDV-UHFFFAOYSA-N 0.000 claims description 5
- KKGQZFFYBBQLKI-UHFFFAOYSA-N 1,3-dimethyl-2-sulfanylidenepyrimidin-4-one Chemical compound CN1C=CC(=O)N(C)C1=S KKGQZFFYBBQLKI-UHFFFAOYSA-N 0.000 claims description 5
- QAMXFYYZTPYIKZ-UHFFFAOYSA-N 1,5-dimethyl-2-sulfanylidenepyrimidin-4-one Chemical compound CC1=CN(C)C(=S)NC1=O QAMXFYYZTPYIKZ-UHFFFAOYSA-N 0.000 claims description 5
- NHYBHTWIHXJICP-UHFFFAOYSA-N 1-methyl-2-sulfanylidenepyrimidin-4-one Chemical compound CN1C=CC(=O)NC1=S NHYBHTWIHXJICP-UHFFFAOYSA-N 0.000 claims description 5
- KMJMDWDBNHZINA-UHFFFAOYSA-N 3-methyl-2-sulfanylidene-1h-pyrimidin-4-one Chemical compound CN1C(=O)C=CNC1=S KMJMDWDBNHZINA-UHFFFAOYSA-N 0.000 claims description 5
- CVUUUVXCTJCXGC-UHFFFAOYSA-N 5-butyl-6-ethyl-2-sulfanylidene-1h-pyrimidin-4-one Chemical compound CCCCC1=C(CC)NC(=S)NC1=O CVUUUVXCTJCXGC-UHFFFAOYSA-N 0.000 claims description 5
- CTHUKFGHEPDDJE-UHFFFAOYSA-N 5-butyl-6-methyl-2-sulfanylidene-1h-pyrimidin-4-one Chemical compound CCCCC1=C(C)NC(=S)NC1=O CTHUKFGHEPDDJE-UHFFFAOYSA-N 0.000 claims description 5
- VURDXXXEUABMQP-UHFFFAOYSA-N 5-butyl-6-propyl-2-sulfanylidene-1h-pyrimidin-4-one Chemical compound CCCCC1=C(CCC)NC(=S)NC1=O VURDXXXEUABMQP-UHFFFAOYSA-N 0.000 claims description 5
- JYBWJPAOAQCXAX-UHFFFAOYSA-N 5-ethyl-2-sulfanylidene-1h-pyrimidin-4-one Chemical compound CCC1=CNC(=S)NC1=O JYBWJPAOAQCXAX-UHFFFAOYSA-N 0.000 claims description 5
- ZJMBNUYBNVJABC-UHFFFAOYSA-N 5-ethyl-5-(2-methylpropyl)-2-sulfanylidene-1,3-diazinane-4,6-dione Chemical compound CC(C)CC1(CC)C(=O)NC(=S)NC1=O ZJMBNUYBNVJABC-UHFFFAOYSA-N 0.000 claims description 5
- UTGGJYGCTHNWFC-UHFFFAOYSA-N 5-hexyl-2-sulfanylidene-1h-pyrimidin-4-one Chemical compound CCCCCCC1=CNC(=S)NC1=O UTGGJYGCTHNWFC-UHFFFAOYSA-N 0.000 claims description 5
- RWJRFPUNLXBCML-UHFFFAOYSA-N 5-propyl-2-sulfanylidene-1h-pyrimidin-4-one Chemical compound CCCC1=CNC(=S)NC1=O RWJRFPUNLXBCML-UHFFFAOYSA-N 0.000 claims description 5
- CZCACHQVHFLZIT-UHFFFAOYSA-N 6-butyl-5-methyl-2-sulfanylidene-1H-pyrimidin-4-one Chemical compound CC=1C(NC(NC1CCCC)=S)=O CZCACHQVHFLZIT-UHFFFAOYSA-N 0.000 claims description 5
- HWGBHCRJGXAGEU-UHFFFAOYSA-N Methylthiouracil Chemical compound CC1=CC(=O)NC(=S)N1 HWGBHCRJGXAGEU-UHFFFAOYSA-N 0.000 claims description 5
- 229960002545 methylthiouracil Drugs 0.000 claims description 5
- SHBTUGJAKBRBBJ-UHFFFAOYSA-N 1,3-diethyl-2-sulfanylidene-1,3-diazinane-4,6-dione Chemical compound CCN1C(=O)CC(=O)N(CC)C1=S SHBTUGJAKBRBBJ-UHFFFAOYSA-N 0.000 claims description 3
- MEAKRQUSGACTFV-UHFFFAOYSA-N 5,6-dimethyl-2-sulfanylidene-1h-pyrimidin-4-one Chemical compound CC=1NC(=S)NC(=O)C=1C MEAKRQUSGACTFV-UHFFFAOYSA-N 0.000 claims description 3
- XZVYOSIHDWNKKK-UHFFFAOYSA-N 6-methyl-5-propyl-2-sulfanylidene-1h-pyrimidin-4-one Chemical compound CCCC1=C(C)NC(=S)NC1=O XZVYOSIHDWNKKK-UHFFFAOYSA-N 0.000 claims description 3
- QGVNJRROSLYGKF-UHFFFAOYSA-N thiobarbital Chemical compound CCC1(CC)C(=O)NC(=S)NC1=O QGVNJRROSLYGKF-UHFFFAOYSA-N 0.000 claims description 3
- NWWZLDXOHWTTKD-UHFFFAOYSA-N 1,3-dimethyl-2-sulfanylidene-1,3-diazinane-4,6-dione Chemical compound CN1C(=O)CC(=O)N(C)C1=S NWWZLDXOHWTTKD-UHFFFAOYSA-N 0.000 claims description 2
- ZULFBEOZXBJCSU-UHFFFAOYSA-N CC1=C(C(NC(N1)=S)=O)CCC.CC=1C(NC(NC1C)=S)=O Chemical compound CC1=C(C(NC(N1)=S)=O)CCC.CC=1C(NC(NC1C)=S)=O ZULFBEOZXBJCSU-UHFFFAOYSA-N 0.000 claims description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 abstract description 32
- 229910052802 copper Inorganic materials 0.000 abstract description 32
- 239000010949 copper Substances 0.000 abstract description 32
- JPVYNHNXODAKFH-UHFFFAOYSA-N Cu2+ Chemical compound [Cu+2] JPVYNHNXODAKFH-UHFFFAOYSA-N 0.000 abstract description 4
- 229910001431 copper ion Inorganic materials 0.000 abstract description 4
- 230000001771 impaired effect Effects 0.000 abstract description 4
- 150000003376 silicon Chemical class 0.000 abstract description 2
- 239000000243 solution Substances 0.000 description 65
- 239000000758 substrate Substances 0.000 description 13
- 239000007864 aqueous solution Substances 0.000 description 12
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 10
- 150000001875 compounds Chemical class 0.000 description 10
- WGTYBPLFGIVFAS-UHFFFAOYSA-M tetramethylammonium hydroxide Chemical compound [OH-].C[N+](C)(C)C WGTYBPLFGIVFAS-UHFFFAOYSA-M 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 8
- 239000002253 acid Substances 0.000 description 7
- 239000000463 material Substances 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 238000012545 processing Methods 0.000 description 5
- 239000004065 semiconductor Substances 0.000 description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 4
- 239000003513 alkali Substances 0.000 description 4
- 239000013078 crystal Substances 0.000 description 4
- 229910021642 ultra pure water Inorganic materials 0.000 description 4
- 239000012498 ultrapure water Substances 0.000 description 4
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 229910017604 nitric acid Inorganic materials 0.000 description 3
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 3
- 239000004810 polytetrafluoroethylene Substances 0.000 description 3
- 229910052814 silicon oxide Inorganic materials 0.000 description 3
- 238000010792 warming Methods 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- OAKJQQAXSVQMHS-UHFFFAOYSA-N Hydrazine Chemical compound NN OAKJQQAXSVQMHS-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 239000004202 carbamide Substances 0.000 description 2
- YCIMNLLNPGFGHC-UHFFFAOYSA-N catechol Chemical compound OC1=CC=CC=C1O YCIMNLLNPGFGHC-UHFFFAOYSA-N 0.000 description 2
- 125000004122 cyclic group Chemical group 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000001747 exhibiting effect Effects 0.000 description 2
- 238000004128 high performance liquid chromatography Methods 0.000 description 2
- 150000002443 hydroxylamines Chemical class 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910021578 Iron(III) chloride Inorganic materials 0.000 description 1
- BAVYZALUXZFZLV-UHFFFAOYSA-O Methylammonium ion Chemical compound [NH3+]C BAVYZALUXZFZLV-UHFFFAOYSA-O 0.000 description 1
- 0 S=C1NC*CN1 Chemical compound S=C1NC*CN1 0.000 description 1
- 229910052581 Si3N4 Inorganic materials 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 150000001447 alkali salts Chemical class 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 1
- 239000000920 calcium hydroxide Substances 0.000 description 1
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 229910000365 copper sulfate Inorganic materials 0.000 description 1
- ARUVKPQLZAKDPS-UHFFFAOYSA-L copper(II) sulfate Chemical compound [Cu+2].[O-][S+2]([O-])([O-])[O-] ARUVKPQLZAKDPS-UHFFFAOYSA-L 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 238000001312 dry etching Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 150000004679 hydroxides Chemical class 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 229910021506 iron(II) hydroxide Inorganic materials 0.000 description 1
- NCNCGGDMXMBVIA-UHFFFAOYSA-L iron(ii) hydroxide Chemical compound [OH-].[OH-].[Fe+2] NCNCGGDMXMBVIA-UHFFFAOYSA-L 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 229920002120 photoresistant polymer Polymers 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000012552 review Methods 0.000 description 1
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 1
- ABTOQLMXBSRXSM-UHFFFAOYSA-N silicon tetrafluoride Chemical compound F[Si](F)(F)F ABTOQLMXBSRXSM-UHFFFAOYSA-N 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 150000005846 sugar alcohols Chemical class 0.000 description 1
- 125000000446 sulfanediyl group Chemical group *S* 0.000 description 1
- 150000003573 thiols Chemical class 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
- H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
- H01L21/30604—Chemical etching
- H01L21/30608—Anisotropic liquid etching
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
- B81C1/00—Manufacture or treatment of devices or systems in or on a substrate
- B81C1/00436—Shaping materials, i.e. techniques for structuring the substrate or the layers on the substrate
- B81C1/00523—Etching material
- B81C1/00539—Wet etching
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K13/00—Etching, surface-brightening or pickling compositions
- C09K13/02—Etching, surface-brightening or pickling compositions containing an alkali metal hydroxide
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K13/00—Etching, surface-brightening or pickling compositions
- C09K13/04—Etching, surface-brightening or pickling compositions containing an inorganic acid
- C09K13/08—Etching, surface-brightening or pickling compositions containing an inorganic acid containing a fluorine compound
Definitions
- the present invention relates to a silicon etching process, and more particularly to a silicon etching solution and a silicon etching method used for manufacturing micro electromechanical element (MEMS) parts and semiconductor devices.
- MEMS micro electromechanical element
- etching is performed using an acid-based etchant which is a mixed aqueous solution in which components such as hydrofluoric acid and nitric acid are added, or potassium hydroxide (KOH), tetrahydroxide
- an alkaline etching solution that is an aqueous solution such as methylammonium (TMAH).
- the silicon surface is oxidized by a component having an oxidizing action such as nitric acid to produce silicon oxide, and this silicon oxide is dissolved as silicon fluoride by hydrofluoric acid or the like, so that etching is performed. proceed.
- a feature of etching with an acid-based etchant is that etching proceeds isotropically.
- the etching rate of the acid-based etching solution varies depending on the mixing ratio of hydrofluoric acid and nitric acid, and is about 1 to 100 ⁇ m / min.
- the acid-based etching solution corrodes metal wiring such as copper and aluminum, and thus is difficult to use in a process in which metal coexists.
- etching when an alkaline etching solution is used, silicon is dissolved as silicate ions by the hydroxy anion in the solution, and at this time, water is reduced to generate hydrogen.
- etching when etching is performed with an alkaline etching solution, unlike an acid etching solution, etching with single crystal silicon proceeds while exhibiting anisotropy. This is based on the fact that there is a difference in the dissolution rate of silicon for each crystal plane orientation of silicon, which is also called crystal anisotropic etching. Microscopically, etching proceeds while maintaining anisotropy when viewed microscopically, but since the crystal grain orientation is randomly distributed, macroscopically isotropic etching seems to proceed. Looks like. In amorphous, etching proceeds isotropically both microscopically and macroscopically.
- an aqueous solution of sodium hydroxide (NaOH), ammonia, hydrazine, or the like is used in addition to an aqueous solution of KOH and TMAH.
- NaOH sodium hydroxide
- TMAH TMAH
- a long processing time of several hours to several tens of hours is often required depending on a target processing shape, temperature conditions for processing, and the like.
- Patent Document 1 discloses a technique of using an aqueous solution obtained by adding hydroxylamines to TMAH as an etching solution.
- Patent Document 2 discloses a technique in which an aqueous solution in which a specific compound such as iron, iron (III) chloride, or iron (II) hydroxide is added to TMAH is used as an etching solution. It is disclosed that the combination of iron and hydroxylamine is particularly suitable for the etching rate.
- Patent Document 3 discloses a technique in which an aqueous solution obtained by adding hydroxylamines to KOH is used as an etching solution.
- Patent Document 4 discloses an etching solution comprising an alkali reducing compound and an anticorrosive agent (such as sugar, sugar alcohol, catechol).
- Patent Document 5 discloses a technique for suppressing the decomposition of hydroxylamine by adding an acid to an alkali.
- Patent Document 6 discloses a technique for suppressing decomposition of hydroxylamine by adding an alkali salt to alkali and hydroxylamine.
- Patent Document 7 is a patent including KOH, hydroxylamine, and urea, but it is a patent related to development of a photoresist, and there is no description about a silicon etching solution and an etching method.
- Patent Document 8 discloses a silicon etching solution that dissolves single crystal silicon anisotropically, and (1) one or more alkaline hydroxides selected from potassium hydroxide, sodium hydroxide, and tetramethylammonium hydroxide. (2) A silicon etching solution characterized in that it is an alkaline aqueous solution containing hydroxylamine and (3) a thiourea group. There is no description about a cyclic compound having a structure.
- the alkaline etching solution containing hydroxylamine as disclosed in Patent Document 1 has a feature that the etching rate is greatly improved as compared with an alkaline etching solution not containing hydroxylamine, but the etching solution is added for a long time. If heated, hydroxylamine may decompose.
- the etching rate is greatly reduced when copper or copper ions are present (Non-Patent Document 1).
- copper is often used as a wiring material in the manufacturing process of semiconductor devices and MEMS parts, and an alkaline etching solution containing hydroxylamine has a feature that the etching rate of silicon is high. When the semiconductor substrate is immersed in an etching solution, there is a disadvantage that the etching rate of silicon is remarkably reduced.
- the present invention aims to solve at least one of the above-mentioned problems in the prior art.
- the present invention particularly when silicon is etched using an etching solution containing hydroxylamine, even when copper is present in the semiconductor substrate, the etching rate is kept high and the stability of the etching solution is not impaired. It is an object to provide an etching solution. It is another object of the present invention to provide a semiconductor substrate having a silicon substrate processed by an etching method using the etching solution and a MEMS.
- the present inventors contain an alkali metal hydroxide, a hydroxylamine, and a cyclic compound having a specific structure in which thiourea groups are connected and N and N ′ are connected.
- the inventors found that the etching rate of silicon does not decrease even when copper and / or copper ions are present, and the stability of the etching solution is not impaired, and the present invention has been completed. That is, the present invention relates to a silicon etching solution, an etching method, and MEMS, and is as follows.
- a silicon etching solution for dissolving single crystal silicon anisotropically comprising (1) potassium hydroxide or sodium hydroxide, (2) hydroxylamine, and (3) a thiourea group, N, N It is a silicon etching liquid characterized by containing a cyclic compound represented by the following general formula (I) connecting '.
- Q represents an organic group having a saturated or unsaturated carbon-carbon bond.
- a cyclic compound represented by the general formula (I) having a thiourea group and connecting N and N ′ is ethylenethiourea, propylenethiourea, 2-thiouracil, 2-thiobarbituric acid, 6 -Methyl-2-thiouracil, 5-butyl-6-ethyl-2-thiouracil, 5-butyl-6-methyl-2-thiouracil, 5-butyl-6-propyl-2-thiouracil, 5,6-dimethyl-2 -Thiouracil, 6-methyl-5-propyl-2-thiouracil, 5-propylthiouracil, 5-methyl-6-butyl-2-thiouracil, 5-hexyl-2-thiouracil, 5-ethyl-2-thiouracil, 1-methyl-2-thiouracil, 3-methyl-2-thiouracil, 1,3-dimethyl-2-thiouracil, 1,5-dimethyl-2-thiouracil, thio Rubital, 5- (2-methyl
- the cyclic compound represented by the general formula (I) having a thiourea group and connecting N and N ′ is selected from ethylenethiourea, propylenethiourea, 2-thiouracil, and 2-thiobarbituric acid. It is a silicon etching liquid as described in said ⁇ 1> which is 1 or more types chosen from these groups.
- the concentration of (1) potassium hydroxide or sodium hydroxide is 7 to 45% by mass
- the concentration of (2) hydroxylamine is 5 to 15% by mass
- the thiourea group is The silicon etching according to any one of ⁇ 1> to ⁇ 3>, wherein the concentration of the cyclic compound represented by the general formula (I) in which N and N ′ are connected is 0.00001 to 1.5% by mass It is a liquid.
- a silicon etching method for dissolving single crystal silicon anisotropically comprising (1) an alkali metal hydroxide, (2) hydroxylamine, and (3) a thiourea group, and N, N ′
- a silicon etching method characterized by using a silicon etching solution containing a cyclic compound represented by the following general formula (I) in which (In general formula (I), Q represents an organic group having a saturated or unsaturated carbon-carbon bond.)
- ⁇ 7> The concentration of (1) alkali metal hydroxide is 7 to 45% by mass, the concentration of (2) hydroxylamine is 5 to 15% by mass, and (3) has a thiourea group.
- ⁇ 8> A microelectromechanical element manufactured using the silicon etching solution according to any one of ⁇ 1> to ⁇ 4>.
- the present invention when an alkaline aqueous solution containing hydroxylamine is used to etch silicon containing copper and copper wiring in the silicon substrate or having copper and copper wiring on the silicon substrate, copper is further contained in the etching solution.
- an etching solution that exhibits a high silicon etching rate and does not impair the stability of the etching solution can be provided. This is presumably because the compound having a thiourea group used in the present invention has a cyclic structure and, as a result, is difficult to decompose.
- the concentration of hydroxylamine used in the present invention can be appropriately determined according to the desired silicon etching rate, and is preferably in the range of 5 to 15% by mass with respect to the total amount of the silicon etching solution. More preferably, it is in the range of 7 to 13% by mass, particularly preferably 9 to 11% by mass. If the content is 5 to 15% by mass, silicon can be effectively etched.
- the alkali metal hydroxide used in the present invention is preferably potassium hydroxide, sodium hydroxide or calcium hydroxide, and particularly preferably potassium hydroxide.
- the concentration of the alkali metal hydroxide used in the present invention may be a conventional alkali compound concentration capable of obtaining desired etching characteristics. However, the solubility of the alkali metal hydroxide in water and the concentration of hydroxylamine and thiol in the etching solution may be used. It can be appropriately determined depending on the concentration of urea, and is preferably in the range of 7 to 45% by mass, more preferably 10 to 40% by mass, and particularly preferably 15 to 35% by mass with respect to the total amount of the silicon etching solution. Used in the range of If it is in the range of 7 to 45% by mass, silicon can be effectively etched.
- a cyclic compound represented by the following general formula (I) having a thiourea group and connecting N and N ′ is used.
- Q represents an organic group having a saturated or unsaturated carbon-carbon bond.
- Specific examples of the cyclic compound represented by the general formula (I) having a thiourea group and connecting N and N ′ include ethylenethiourea, propylenethiourea, 2-thiouracil, 2-thiobarbituric acid, 6-methyl -2-thiouracil, 5-butyl-6-ethyl-2-thiouracil, 5-butyl-6-methyl-2-thiouracil, 5-butyl-6-propyl-2-thiouracil, 5,6-dimethyl-2-thiouracil 6-methyl-5-propyl-2-thiouracil, 5-propylthiouracil, 5-methyl-6-butyl-2-thiouracil, 5-hexyl-2-thiouracil, 5-ethyl-2-thiouracil, 5-ethyl
- the concentration of the cyclic compound represented by the general formula (I) having a thiourea group and connecting N and N ′ used in the present invention is 0.00001% by mass to 1.% by mass with respect to the total amount of the silicon etching solution. 5 mass% is preferable, 0.00005 mass% to 0.5 mass% is more preferable, and 0.0001 mass% to 0.1 mass% is particularly preferable. If it is in the range of 0.00001% by mass to 1.5% by mass, silicon can be effectively etched.
- the etching target is usually immersed in a heated etching solution, taken out after a predetermined time, and the etching solution adhering to the target is washed away with water or the like and then attached.
- the method of drying the water is taken.
- the etching temperature is preferably 40 ° C. or higher and lower than the boiling point, more preferably 50 ° C. to 90 ° C., particularly preferably 70 ° C. to 90 ° C. If the etching temperature is within this range, silicon can be effectively etched.
- a suitable processing temperature may be appropriately determined in consideration of suppressing a change in the composition of the etching solution.
- Etching time can be appropriately selected depending on etching conditions and etching target. Usually, it is 1 to 300 minutes, preferably 10 to 180 minutes, more preferably 10 to 120 minutes, and particularly preferably 20 to 90 minutes, but a suitable treatment time may be appropriately determined.
- An object to be etched in the present invention is a substrate containing single crystal silicon, and single crystal silicon is present in the entire region or a partial region of the substrate.
- the copper etching rate in both cases whether the copper as the wiring material is exposed on the substrate surface from the beginning or the copper inside the substrate is exposed on the surface by etching of silicon, The decrease can be suppressed.
- Single crystal silicon may be in a single layer or in a state of being laminated in multiple layers. Those which are ion-doped in the whole region or a partial region of these substrates are also objects of etching treatment.
- materials such as silicon oxide films, silicon nitride films, silicon organic films, and metal films such as aluminum films, chromium films, and gold films are present on the surface of the etching object or inside the object. And included in the object of the etching process in the present invention.
- the object to be etched used for the evaluation is a single crystal silicon (100) (sometimes simply referred to as silicon (100)) wafer.
- One side of the silicon (100) wafer is covered with a protective film made of a silicon thermal oxide film, and a part of the silicon thermal oxide film is removed by dry etching on the other side.
- the silicon surface (0.25 cm ⁇ 0.25 cm) has a pattern shape that is regularly exposed.
- This silicon (100) wafer was immersed in a 1% by mass hydrofluoric acid aqueous solution at 23 ° C. for 15 minutes immediately before etching, and then rinsed with ultrapure water and dried. By this hydrofluoric acid aqueous solution treatment, the silicon natural oxide film formed on the surface of the exposed portion of the patterned silicon surface was removed, and then the next etching treatment was performed.
- Method of etching single crystal silicon (100) wafer and method of calculating etching rate (SiER) Etching solution 40 g is put in a polytetrafluoroethylene container and the container is immersed in a hot water bath for etching. The temperature of the liquid was heated to 80 ° C. After the temperature of the etching solution reaches 80 ° C., a single crystal silicon (100) wafer (1 cm ⁇ 1 cm) and a 0.5 cm ⁇ 0.5 cm copper flake (copper thickness is 6000 mm) are simultaneously immersed in the etching solution. Then, immersion treatment was performed for 30 minutes, and then the single crystal silicon (100) wafer was taken out and rinsed and dried with ultrapure water.
- SiER etching rate
- the single crystal silicon (100) wafer that has been subjected to the etching process has a pattern portion that is recessed from the surroundings as the single crystal silicon is etched, and the height difference between the etched portion and the unetched portion is measured.
- the etching depth of the single crystal silicon (100) plane in 30 minutes was obtained.
- a value obtained by dividing the etching depth by 30 was calculated as an etching rate (unit: ⁇ m / min) of the single crystal silicon (100) plane.
- Examples 1 to 13 and Comparative Examples 1 to 4 Etching treatment was performed using the etching solution described in Table 1, and the results are shown in Table 1.
- the structural formula of “a cyclic compound represented by the general formula (I) having a thiourea group and connecting N and N ′” used in Examples 1 to 13 is shown below.
- Comparative Examples 1 to 4 having a thiourea group and not containing the cyclic compound represented by the general formula (I) in which N and N ′ are connected had a significantly lower etching rate than the corresponding Examples 1 to 13. .
- Examples 14 to 20 and Comparative Example 5 The results are summarized in Table 2, except that 0.0001% by mass of copper sulfate was contained in the etching solution shown in Table 2 (excluding copper flakes).
- the cyclic compound represented by the general formula (I) having a thiourea group and connecting N and N ′ is used not only in the case where copper flakes coexist in the etching solution, but also in etching. Even when copper was dissolved in the liquid, it had the ability to suppress a decrease in the etching rate.
- Comparative Example 5 the cyclic compound represented by the general formula (I) having a thiourea group and connecting N and N ′ is not added
- it has a thiourea group and connects N and N ′.
- the etching rate was clearly lower than in Examples 14 to 20 where the cyclic compound represented by the general formula (I) was added.
- the thickness of the copper flakes was measured again with a fluorescent X-ray analyzer, and the etching depth of the copper flakes in 60 minutes was determined by determining the difference in film thickness before and after the treatment. A value obtained by dividing the etching depth by 60 was calculated as a copper etching rate (unit: ⁇ / min).
- the etching solution contains a cyclic compound represented by the general formula (I) having a thiourea group and connecting N and N ′
- the etching rate of copper is less than 1 kg / min.
- the cyclic compound represented by the general formula (I) connecting N and N ′ was not included, the etching rate of copper was 10 ⁇ / min or more.
- the cyclic compound represented by the general formula (I) having a thiourea group and connecting N and N ′ has only the effect of not reducing the etching rate of silicon even when copper is present as a wiring material. It was also found that there is an effect of preventing dissolution of copper as a wiring material. Incidentally, the silicon etching rate was the same value as in Tables 1 and 2 (not shown in the table).
- Examples 27 to 31 and Comparative Examples 7 to 8 Method of measuring concentration of compound having thiourea group before and after warming storage in etching solution
- a part of the etching solution shown in Table 4 is collected and diluted with ultrapure water (concentration of about 0.00001% by mass).
- High-performance liquid chromatography measurement was performed, and the concentration of the compound having a thiourea group in the etching solution was measured to obtain the additive concentration before warm storage. Thereafter, 100 g of the etching solution was placed in a polytetrafluoroethylene container, and this container was immersed in a 50 ° C. hot water bath and held for 72 hours.
- the etching solution was taken out, and the concentration of the compound having a thiourea group in the etching solution after warming storage was measured using high performance liquid chromatography, and the thiourea group decreased during the warming storage.
- the concentration of the compound was determined.
- the change in concentration during heating storage was negligible.
- the compound in which N and N ′ having a thiourea group used in Comparative Examples 7 to 8 are not connected a significant decrease in concentration was observed.
- the example can provide an etching solution in which the stability of the etching solution is not impaired. This is presumably because the compound having a thiourea group used in the present invention has a cyclic structure and, as a result, is difficult to decompose.
- an etching solution that does not decrease the etching rate of silicon, does not etch copper that is a wiring material, and further does not impair stability. It can be provided and is industrially useful.
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Abstract
Description
特許文献2には、TMAHに鉄、塩化鉄(III)、水酸化鉄(II)などの特定の化合物を添加した水溶液をエッチング液として使用する技術が開示されている。エッチング速度は、鉄とヒドロキシルアミンを併用する組み合わせが特に好適であることが開示されている。
特許文献3には、KOHにヒドロキシルアミン類を添加した水溶液をエッチング液として使用する技術が開示されている。
特許文献4には、アルカリ還元性化合物と防食剤(糖、糖アルコール、カテコール等)からなるエッチング液が開示されている。
特許文献5には、アルカリに酸を添加することでヒドロキシルアミンの分解を抑制する技術が開示されている。
特許文献6には、アルカリとヒドロキシルアミンにアルカリ塩を添加することでヒドロキシルアミンの分解を抑制する技術が開示されている。
KOH、ヒドロキシルアミン、尿素を含む特許として特許文献7があるが、フォトレジストの現像に関する特許であり、シリコンエッチング液およびエッチング方法に関する記載は一切ない。また、チオ尿素基を有しN,N’を繋いだ特定構造を有する環状化合物に関する記載も一切ない。
特許文献8には、単結晶シリコンを異方性に溶解するシリコンエッチング液であって、(1)水酸化カリウム、水酸化ナトリウムおよび水酸化テトラメチルアンモニウムから選ばれる1種以上のアルカリ性水酸化物、(2)ヒドロキシルアミン、および(3)チオ尿素基を含有したアルカリ性水溶液であることを特徴とするシリコンエッチング液が開示されているが、チオ尿素基を有しN,N’を繋いだ特定構造を有する環状化合物に関する記載は一切ない。
また、Si(110)のエッチングにおいて、銅もしくは銅イオンが存在するとエッチング速度が大きく低下することが知られている(非特許文献1)。
近年半導体デバイスやMEMS部品の製造工程において、配線材料として銅が使われることが多くなり、ヒドロキシルアミンを含有するアルカリ系エッチング液は、シリコンのエッチング速度が高いという特長を有するが、銅配線等を有する半導体基板をエッチング液中に浸漬すると、シリコンのエッチング速度が著しく低下するという欠点を有する。
<1> 単結晶シリコンを異方性に溶解するシリコンエッチング液であって、(1)水酸化カリウムまたは水酸化ナトリウム、(2)ヒドロキシルアミン、および(3)チオ尿素基を有しN,N’を繋いだ下記一般式(I)で表される環状化合物を含有することを特徴とするシリコンエッチング液である。
<2> 前記(3)チオ尿素基を有しN,N’を繋いだ一般式(I)で表される環状化合物が、エチレンチオ尿素、プロピレンチオ尿素、2-チオウラシル、2-チオバルビツル酸、6-メチル-2-チオウラシル、5-ブチル-6-エチル-2-チオウラシル、5-ブチル-6-メチル-2-チオウラシル、5-ブチル-6-プロピル-2-チオウラシル、5,6-ジメチル-2-チオウラシル、6-メチル-5-プロピル-2-チオウラシル、5-プロピルチオウラシル、5-メチル-6-ブチル-2-チオウラシル、5-へキシル-2-チオウラシル、5-エチル-2-チオウラシル、1-メチル-2-チオウラシル、3-メチル-2-チオウラシル、1,3-ジメチル-2-チオウラシル、1,5-ジメチル-2-チオウラシル、チオバルビタール、5-(2-メチルプロピル)-5-エチル-2-チオバルビツル酸、1,3-ジエチル-2-チオバルビツル酸、1,3,5-トリメチル-2-チオバルビツル酸、および1,3‐ジメチル-2-チオバルビツル酸からなる群より選ばれる1種以上である上記<1>に記載のシリコンエッチング液である。
<3> 前記(3)チオ尿素基を有しN,N’を繋いだ一般式(I)で表される環状化合物が、エチレンチオ尿素、プロピレンチオ尿素、2-チオウラシル、および2-チオバルビツル酸からなる群より選ばれる1種以上である上記<1>に記載のシリコンエッチング液である。
<4> 前記(1)水酸化カリウムまたは水酸化ナトリウムの濃度が7~45質量%であり、前記(2)ヒドロキシルアミンの濃度が5~15質量%であり、前記(3)チオ尿素基を有しN,N’を繋いだ一般式(I)で表される環状化合物の濃度が0.00001~1.5質量%である上記<1>~<3>のいずれかに記載のシリコンエッチング液である。
<5> 単結晶シリコンを異方性に溶解するシリコンエッチング方法であって、(1)アルカリ金属水酸化物、(2)ヒドロキシルアミン、および(3)チオ尿素基を有し、N,N’を繋いだ下記一般式(I)で表される環状化合物を含有するシリコンエッチング液を用いることを特徴とするシリコンエッチング方法である。
<6> 前記(1)アルカリ金属水酸化物が水酸化カリウムまたは水酸化ナトリウムから選ばれる1種以上であり、前記(3)チオ尿素基を有しN,N’を繋いだ一般式(I)で表される環状化合物が、エチレンチオ尿素、プロピレンチオ尿素、2-チオウラシル、2-チオバルビツル酸、6-メチル-2-チオウラシル、5-ブチル-6-エチル-2-チオウラシル、5-ブチル-6-メチル-2-チオウラシル、5-ブチル-6-プロピル-2-チオウラシル、5,6-ジメチル-2-チオウラシル、6-メチル-5-プロピル-2-チオウラシル、5-プロピルチオウラシル、5-メチル-6-ブチル-2-チオウラシル、5-へキシル-2-チオウラシル、5-エチル-2-チオウラシル、1-メチル-2-チオウラシル、3-メチル-2-チオウラシル、1,3-ジメチル-2-チオウラシル、1,5-ジメチル-2-チオウラシル、チオバルビタール、5-(2-メチルプロピル)-5-エチル-2-チオバルビツル酸、1,3-ジエチル-2-チオバルビツル酸、1,3,5-トリメチル-2-チオバルビツル酸、および1,3-ジメチル-2-チオバルビツル酸からなる群より選ばれる1種以上である上記<5>に記載のシリコンエッチング方法である。
<7> 前記(1)アルカリ金属水酸化物の濃度が7~45質量%であり、前記(2)ヒドロキシルアミンの濃度が5~15質量%であり、前記(3)チオ尿素基を有しN,N’を繋いだ一般式(I)で表される環状化合物の濃度が0.00001~1.5質量%である上記<5>または<6>に記載のシリコンエッチング方法である。
<8> 上記<1>~<4>のいずれかに記載のシリコンエッチング液を用いて製造された微小電気機械素子である。
本発明に用いるヒドロキシルアミンの濃度は、所望のシリコンエッチング速度に応じて適宜決定することが可能であり、シリコンエッチング液の全量に対して好ましくは5~15質量%の範囲で用いられる。さらに好ましくは7~13質量%の範囲であり、9~11質量%が特に好ましい。5~15質量%であれば、効果的にシリコンをエッチングすることができる。
チオ尿素基を有しN,N’を繋いだ前記一般式(I)で表される環状化合物の具体例としては、エチレンチオ尿素、プロピレンチオ尿素、2-チオウラシル、2-チオバルビツル酸、6-メチル-2-チオウラシル、5-ブチル-6-エチル-2-チオウラシル、5-ブチル-6-メチル-2-チオウラシル、5-ブチル-6-プロピル-2-チオウラシル、5,6-ジメチル-2-チオウラシル、6-メチル-5-プロピル-2-チオウラシル、5-プロピルチオウラシル、5-メチル-6-ブチル-2-チオウラシル、5-へキシル-2-チオウラシル、5-エチル-2-チオウラシル、1-メチル-2-チオウラシル、3-メチル-2-チオウラシル、1,3-ジメチル-2-チオウラシル、1,5-ジメチル-2-チオウラシル、チオバルビタール、5-(2-メチルプロピル)-5-エチル-2-チオバルビツル酸、1,3-ジエチル-2-チオバルビツル酸、1,3,5-トリメチル-2-チオバルビツル酸、及び1,3-ジメチル-2-チオバルビツル酸が好ましく挙げられ、更に好ましくは、以下の構造式で表されるエチレンチオ尿素、プロピレンチオ尿素、2-チオウラシル、及び2-チオバルビツル酸が挙げられる。
なお、本発明によれば、配線材料である銅が、基板表面に初めから露出していても、シリコンのエッチングによって基板内部の銅が表面に露出しても、どちらの場合でもシリコンエッチング速度の低下を抑制することができる。単結晶シリコンは単層でも多層に積層された状態でも構わない。これらの基板の全域または一部領域にイオンドープしたものもエッチング処理の対象物となる。また、シリコン酸化膜、シリコン窒化膜、シリコン有機膜等の材料や、アルミニウム膜、クロム膜、金膜などの金属膜が上記のエッチング対象物の表面や対象物内部に存在しているものについても、本発明におけるエッチング処理の対象物に含まれる。
エッチング液(後述)40gをポリテトラフルオロエチレン製の容器に入れ、この容器を湯浴中に浸してエッチング液の温度を80℃に加温した。エッチング液の温度が80℃に達した後、単結晶シリコン(100)ウェハ(1cm×1cm)と0.5cm×0.5cmの銅薄片(銅の厚みは6000Å)をエッチング液の中に同時に浸し、30分間浸漬処理を行い、その後、単結晶シリコン(100)ウェハを取り出して超純水によるリンスおよび乾燥を行った。エッチング処理を行った単結晶シリコン(100)ウェハは、単結晶シリコンのエッチングに伴いパターン部分が周囲よりも窪んだ状態になり、エッチングされた部分とエッチングされていない部分との高低差を測定することによって、30分間での単結晶シリコン(100)面のエッチング深さを求めた。このエッチング深さを30で割った値を単結晶シリコン(100)面のエッチング速度(単位はμm/分)として算出した。
表1記載のエッチング液を用いてエッチング処理を行い、結果を表1に記した。実施例1~13で使用した「チオ尿素基を有しN,N’を繋いだ一般式(I)で表される環状化合物」の構造式を以下に示す。チオ尿素基を有し、N,N’を繋いだ一般式(I)で表される環状化合物を含まない比較例1~4は、対応する実施例1~13より明らかにエッチング速度が小さかった。
表2記載のエッチング液に硫酸銅を0.0001質量%含有させた(銅薄片は含まず)以外は、実施例1~13と同様に行い、結果を表2にまとめた。
実施例14~20は、チオ尿素基を有しN,N’を繋いだ一般式(I)で表される環状化合物が、銅薄片がエッチング液中に共存している場合だけでなく、エッチング液中に銅が溶解している場合においても、エッチング速度の低下を抑制する性能を有していた。
しかし、比較例5(チオ尿素基を有しN,N’を繋いだ一般式(I)で表される環状化合物を添加していない)では、チオ尿素基を有しN,N’を繋いだ一般式(I)で表される環状化合物を添加している実施例14~20より明らかにエッチング速度が小さかった。
銅薄片のエッチング処理方法およびエッチング速度の算出方法
表3記載のエッチング液40gをポリテトラフルオロエチレン製の容器に入れ、この容器を湯浴中に浸してエッチング液の温度を80℃に加温した。エッチング液の温度が80℃に達した後、あらかじめ膜厚を蛍光X線分析装置で測定済みの2cm×2cmの銅ベタ膜(銅の厚みは6000Å)をエッチング液の中に同時に浸し、60分間浸漬処理を行い、その後、銅薄片を取り出して超純水によるリンスおよび乾燥を行った。銅薄片の膜厚を再度蛍光X線分析装置で測定し、処理前後の膜厚の差を求めることによって、60分間での銅薄片のエッチング深さを求めた。このエッチング深さを60で割った値を銅のエッチング速度(単位はÅ/分)として算出した。エッチング液にチオ尿素基を有しN,N’を繋いだ一般式(I)で表される環状化合物を含む場合は、銅のエッチング速度は1Å/min未満であるが、チオ尿素基を有しN,N’を繋いだ一般式(I)で表される環状化合物を含まない場合は、銅のエッチング速度は10Å/min以上となった。このことから、チオ尿素基を有しN,N’を繋いだ一般式(I)で表される環状化合物は、配線材料として銅が共存していてもシリコンのエッチング速度を低下させない効果だけでなく、配線材料である銅の溶解を防ぐという効果もあることがわかった。因みに、シリコンエッチング速度は表1および2と同等の値であった(表中記載略)。
エッチング液中の加温保管する前後のチオ尿素基を有する化合物の濃度測定方法
表4記載のエッチング液の一部を分取し、超純水で希釈後(濃度約0.00001質量%)、高速液体クロマトグラフィー測定を行い、エッチング液中のチオ尿素基を有する化合物の濃度を測定し、加温保管前の添加剤濃度とした。その後、エッチング液100gをポリテトラフルオロエチレン製の容器に入れ、この容器を50℃の湯浴中に浸し、72時間保持した。72時間後、エッチング液を取り出し、高速液体クロマトグラフィーを用いて、加温保管後のエッチング液中のチオ尿素基を有する化合物の濃度を測定し、加温保管中に減少したチオ尿素基を有する化合物の濃度を求めた。
実施例27~31で使用したチオ尿素基を有しN,N’を繋いだ一般式(I)で表される環状化合物の場合は、加温保管中に濃度の変化はごくわずかであったが、比較例7~8で使用したチオ尿素基を有するN,N’が繋がっていない化合物の場合は、大幅な濃度低下が見られた。このことから、実施例では、エッチング液の安定性が損なわれないエッチング液を提供することができることがわかる。これは、本発明で使用されるチオ尿素基を有する化合物が環状構造を有し、その結果、分解し難いためと考えられる。
Claims (8)
- 前記(3)チオ尿素基を有し、N,N’を繋いだ一般式(I)で表される環状化合物が、エチレンチオ尿素、プロピレンチオ尿素、2-チオウラシル、2-チオバルビツル酸、6-メチル-2-チオウラシル、5-ブチル-6-エチル-2-チオウラシル、5-ブチル-6-メチル-2-チオウラシル、5-ブチル-6-プロピル-2-チオウラシル、5,6-ジメチル-2-チオウラシル、6-メチル-5-プロピル-2-チオウラシル、5-プロピルチオウラシル、5-メチル-6-ブチル-2-チオウラシル、5-へキシル-2-チオウラシル、5-エチル-2-チオウラシル、1-メチル-2-チオウラシル、3-メチル-2-チオウラシル、1,3-ジメチル-2-チオウラシル、1,5-ジメチル-2-チオウラシル、チオバルビタール、5-(2-メチルプロピル)-5-エチル-2-チオバルビツル酸、1,3-ジエチル-2-チオバルビツル酸、1,3,5-トリメチル-2-チオバルビツル酸、および1,3‐ジメチル-2-チオバルビツル酸からなる群より選ばれる1種以上である請求項1に記載のシリコンエッチング液。
- 前記(3)チオ尿素基を有しN,N’を繋いだ一般式(I)で表される環状化合物が、エチレンチオ尿素、プロピレンチオ尿素、2-チオウラシル、および2-チオバルビツル酸からなる群より選ばれる1種以上である請求項1に記載のシリコンエッチング液。
- 前記(1)水酸化カリウムまたは水酸化ナトリウムの濃度が7~45質量%であり、前記(2)ヒドロキシルアミンの濃度が5~15質量%であり、前記(3)チオ尿素基を有しN,N’を繋いだ一般式(I)で表される環状化合物の濃度が0.00001~1.5質量%である請求項1~3のいずれかに記載のシリコンエッチング液。
- 前記(1)アルカリ金属水酸化物が水酸化カリウムまたは水酸化ナトリウムから選ばれる1種以上であり、前記(3)チオ尿素基を有しN,N’を繋いだ一般式(I)で表される環状化合物が、エチレンチオ尿素、プロピレンチオ尿素、2-チオウラシル、2-チオバルビツル酸、6-メチル-2-チオウラシル、5-ブチル-6-エチル-2-チオウラシル、5-ブチル-6-メチル-2-チオウラシル、5-ブチル-6-プロピル-2-チオウラシル、5,6-ジメチル-2-チオウラシル、6-メチル-5-プロピル-2-チオウラシル、5-プロピルチオウラシル、5-メチル-6-ブチル-2-チオウラシル、5-へキシル-2-チオウラシル、5-エチル-2-チオウラシル、1-メチル-2-チオウラシル、3-メチル-2-チオウラシル、1,3-ジメチル-2-チオウラシル、1,5-ジメチル-2-チオウラシル、チオバルビタール、5-(2-メチルプロピル)-5-エチル-2-チオバルビツル酸、1,3-ジエチル-2-チオバルビツル酸、1,3,5-トリメチル-2-チオバルビツル酸、および1,3-ジメチル-2-チオバルビツル酸からなる群より選ばれる1種以上である請求項5に記載のシリコンエッチング方法。
- 前記(1)アルカリ金属水酸化物の濃度が7~45質量%であり、前記(2)ヒドロキシルアミンの濃度が5~15質量%であり、前記(3)チオ尿素基を有しN,N’を繋いだ一般式(I)で表される環状化合物の濃度が0.00001~1.5質量%である請求項5または6に記載のシリコンエッチング方法。
- 請求項1~4のいずれかに記載のシリコンエッチング液を用いて製造された微小電気機械素子。
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