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Surface treatment of SiC using NF 3 /O 2 plasma. Class presentation by Liu Yen Kang e-mail: L1492@ms35.hinet.net September 2002. Outline . Introduction of silicon carbide Surface treatment of SiC Wet etching Dry etching- RIE, ECR, ICP Conclusions.
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Surface treatment of SiC using NF3/O2 plasma Class presentation by Liu Yen Kang e-mail: L1492@ms35.hinet.net September 2002
Outline Introduction of silicon carbide Surface treatment of SiC Wet etching Dry etching- RIE, ECR, ICP Conclusions
Deposition of SiC(ECR plasma CVD) (1.3-4.7x10-3 mbar) 80-90 A 875 G 120-130 A (710 °C) Ref.: S.J. Toal, H.S.Reehal, applied surface science 138-139(1999), 424-428.
Properties of b-SiC b-SiC has wide band gap, short carrier life time, low coefficient of thermal expansion, and high thermal conductivity. but…SiC has the poor machining property (high mechanical strength, chemical stability)
Surface treatment of SiC Wet etching- molten KOH or NaOH at 873 to 1073K conventional reactor (RIE) (operating pressure 10-300 mTorr, ion flux >109 cm-3 ) Dry etching high density plasma source (ECR, ICP) (operating pressure 1-2 mTorr, ion flux >1011 cm-3 ) (with fluoride based gas )
Etching in RIE (CF4 / O2 plasma) CF4 dissociation: CF4+e- CF3+ +F + 2e- Etch mechanism: Si +4F SiF4 (volatile) C + xF CFx (Adding O2 forms CO, CO2 compounds and causes more available F atoms.) Ref.:G.Saggio, E.Verona, Materials Science and Engineering B29(1995), 176-180
Etching in ECR (CF4 / O2 plasma) Microwave power=200W RF power =70W Total flux=25sccm Etching time=20 mins. -to be continued
(etch pressure: 2.5x10-3 torr ) Residence time=(PxV)/Q (sec) (oxygen percentage: 40% ) Ref.: Alexandar L. Syrkin, Jean Marie Bluet, Materials Science and Engineering B46(1997), 374-378
Etching in RIE (NF3 / O2 plasma) NF3 dissociation: NF3+e- NF2+ +F + 2e- Etch mechanism: Si +4F SiF4 C + xF CFx (Adding O2 can enhance etch rates by forming CO, CO2 ) Ref.: Christoph Richter, Klaus Espertshuber, Materials Science and Engineering B46(1997), 160-163
Etching in ICP (NF3 / O2 orAr plasma) NF3 ,O2 , Ar 1-2 mTorr ~750 W ~250 W -to be continued Ref.: Dong-Sing WUU, Fang-Ching Liao, Jpn. J. Appl. Phys. Vol. 39 (2000), 2068-2072
-to be continued Ref.: J.J. Wang, E. S. Lambers, Solid-State Electronics Vol. 42 No.12 (1998), 2283-2282
Ref.: J.J. Wang, E.S. Lambers, Solid-State Electronics Vol.42 No.5(1998), 743-747
Conclusions • NF3 showed efficient bond-breaking in SiC rather than bombardment (CF4). • Different reactors, applied power, gases pressure (residence time) are the main parameters in etching. .