Basic 2Basic 2 Anisotropic Wet-etching of Silicon ...

1 Basic 2 Basic 2 Anisotropic Wet-etchingof Silicon : characterization and modeling of changeablemodeling of changeable AnisotropypyProf K SatoProf. K. SatoDept. of Micro/Nano Systems EngineeringNagoya UniversityBasic 2 Anisotropic Wet-etching of Silicon : Prof. K. SatoCharacterization and modeling of changeable AnisotropyCOE for Education and Research of Micro-Nano Mechatronics, Nagoya UniversityOrientation Dependent Etching(Conventional Products) 110 111 112 100 SiO2 111 100 SiO2 SiDiaphragmDeep grooves on a (110) waferDiaphragm on a (100) waferBasic 2 Anisotropic Wet-etching of Silicon : Prof.

2 K. SatoCharacterization and modeling of changeable AnisotropyCOE for Education and Research of Micro-Nano Mechatronics, Nagoya UniversityVariation in etching profile on (100) Silicon waferGroove Wall Orientations(111)(100)(110)(111) (100) (110)KOHTMAHKOHTMAHKOH/IPATMAH/f t tTMAHEDPTMAHTMAH/surfactantEDPB asic 2 Anisotropic Wet-etching of Silicon : Prof. K. SatoCharacterization and modeling of changeable AnisotropyCOE for Education and Research of Micro-Nano Mechatronics, Nagoya UniversityVariation in etching profile on (110) Silicon waferGroove Wall OrientationsGroove Wall Orientations(111) (111) (100) (110)KOHTMAHEDPKOHTMAHEDPKOHTMAHKOH/IPAT MAH/surfactantEDPEDPEDPEDPB asic 2 Anisotropic Wet-etching of Silicon : Prof.

3 K. SatoCharacterization and modeling of changeable AnisotropyCOE for Education and Research of Micro-Nano Mechatronics, Nagoya UniversityNon-conventional 3-D microstructures using KOH Anisotropic etchingEtchingfrombothsidesofawaferTwost epetchingusingtwomasklayers Etching from bothsidesofawaferTwo-stepetchingusingtwo masklayersK. Sato, et al, Proc. IFToMM Intl. Micromechanism Symp. (Tokyo, ) 155-160 Basic 2 Anisotropic Wet-etching of Silicon : Prof. K. SatoCharacterization and modeling of changeable AnisotropyCOE for Education and Research of Micro-Nano Mechatronics, Nagoya UniversityDensely Arrayed Silicon Needles with a Pitch Distance of 200 microns Aiming at Transdermal Drug DeliveryMShikidaet al :ProcMEMS03 (Kyoto 2003) 562M.

4 Shikidaet al.:Proc. MEMS-03 (Kyoto, 2003), 562 Basic 2 Anisotropic Wet-etching of Silicon : Prof. K. SatoCharacterization and modeling of changeable AnisotropyCOE for Education and Research of Micro-Nano Mechatronics, Nagoya UniversityNew types of anisotropically etched 3-D structures: Curved, Sharp-cornered, 45-degree-angled V-grooves Prem Pal: Jpn. J. Appl. Phys. 49 (2010)056702[][100][110][110] Basic 2 Anisotropic Wet-etching of Silicon : Prof.

5 K. SatoCharacterization and modeling of changeable AnisotropyCOE for Education and Research of Micro-Nano Mechatronics, Nagoya UniversityAnisotropic chemical etching of Sifrom MEMS Point of View Etching SolutionsKOH, TMAH , EDP , N2H4, NaOH, CsOH, Chemical reactionSi + 2OH-+ 2H2 OSi(OH)+HSiO(OH)2+2H Si(OH)4+ H2 SiO2(OH)22-+ 2H2 What are known;Si (111) shows an extremely low etch rateSi (111) shows an extremely low etch techniques: B-dope, Electro-chemical, ApplicationsDiaphragms, V-grooves, CantileversDiaphragms, Vgrooves, Cantilevers ---Limitations in fabricated shapesMany mysteriesBasic 2 Anisotropic Wet-etching of Silicon : Prof.

6 K. SatoCharacterization and modeling of changeable AnisotropyCOE for Education and Research of Micro-Nano Mechatronics, Nagoya UniversityMany mysteriesSequential reactions of Si etching in alkaline solutionSi+ 2OH-+ 2H2O SiO2(OH)22-+ 2H2ffThis is the results of the following steps.(R. A. Wind, Hines, Surface Science 460 (2000) 21-38) SiH2+ OH-+ H2O SiHOH+ H2+ OH-222 SiHOH+ OH-+ H2O Si(OH)2+ H2 + OH-(Si)Si(OH) HO (SiH)Si(OH)( Si)2 Si(OH)2+ H2O ( Si-H) Si(OH)4Si(OH)4+ OH- SiO2(OH)22-+ H2O()42()22 Basic 2 Anisotropic Wet-etching of Silicon : Prof.

7 K. SatoCharacterization and modeling of changeable AnisotropyCOE for Education and Research of Micro-Nano Mechatronics, Nagoya UniversityContentsCharacterization of Anisotropic EtchingCharacterization of Anisotropic Etchingin macroscopic domains Dangling-Bond Model does not tell the truth,because no dynamics included. y Step Flow Model explains anisotropy in the vicinity of Si (111)vicinity of Si (111) *Rditb tKOHd TMAH*Reversed anisotropy between KOH and TMAH*Etched shape clearly reflects atomic-step pypbehavior in the vicinity of Si (111) Basic 2 Anisotropic Wet-etching of Silicon : Prof.

8 K. SatoCharacterization and modeling of changeable AnisotropyCOE for Education and Research of Micro-Nano Mechatronics, Nagoya UniversityContentsCharacterization of Anisotropic EtchingCharacterization of Anisotropic Etchingin macroscopic domains DliBdMdl dttllthtth Dangling-Bond Model does not tell the truth,because no dynamics included. Step Flow Model explains anisotropy in the vicinity of Si (111) ctyoS( )*Reversed anisotropy between KOH and TMAH*Reversed anisotropy between KOH and TMAH*Etched shape clearly reflects atomic-step behavior in the vicinity of Si (111) Basic 2 Anisotropic Wet-etching of Silicon : Prof.

9 K. SatoCharacterization and modeling of changeable AnisotropyCOE for Education and Research of Micro-Nano Mechatronics, Nagoya UniversityEtching rate measurementK. Sato et al.: Sensors and Actuators A-64 (1998) 87-93.(110)contactprobe(110)contactprobe R=22mmprobing networkR 22mmR(001)()(110)-Hemispherical specimen of single-crystal Silicon Basic 2 Anisotropic Wet-etching of Silicon : Prof. K. SatoCharacterization and modeling of changeable AnisotropyCOE for Education and Research of Micro-Nano Mechatronics, Nagoya UniversityHemispherical specimenBeforeAfter Maximum etching depth: 100 - 150 mBasic 2 Anisotropic Wet-etching of Silicon : Prof.

10 K. SatoCharacterization and modeling of changeable AnisotropyCOE for Education and Research of Micro-Nano Mechatronics, Nagoya UniversityEtching rate contour map for a KOH solution(100)K. Sato et al.: Sensors and Actuators A-64 (1998) (111)(100)60 (110)30 0 0 30(110)90 0 0 30 60 90 (100)NAGOYA UNIVERSITY(100)minmaxBasic 2 Anisotropic Wet-etching of Silicon : Prof. K. SatoCharacterization and modeling of changeable AnisotropyCOE for Education and Research of Micro-Nano Mechatronics, Nagoya UniversityEffects of a surfactant added to TMAH solutionK.