| Summary: | 碩士 === 國立中央大學 === 電機工程學系 === 85 === The main purpose of our study in this thesis is to investigate a
new kind of RIE etchant,and apply this new gas mixture for gate-
recess etching in InP-basedHEMT fabrication.There are four kinds
of gas mixture to be proposed here.In order to achieve the
selective dry etching between InAlAs and InGaAs,the
characteristics of BCl3+CHF3 and BCl3+CF4 gas mixtures in the
aspects of etching rates, selectivity, etched profile, surface
roughness, RIE induced damage and damage recovery will be
studied in detail. We will propose reasonable explanations about
some unexpected results in this study.In conclusion,a
selectivity of 2.7 was obtained by optimizing the BCl3+CHF3 RIE
etching condition.If the In-composition in the material
decreases from 0.52 to 0.15,the selectivity between InGaAs and
InAlAs will increases from 2.7 to 11.The highest selectivity
obtained by BCl3+CF4 RIE etching is only 2.3.After PL and TLM
measurements,we found that the damage induced by BCl3+CHF3
etchant is smaller than that induced by BCl3+CF4 etchant.The
damage induced by RIE etching can also be recovered by RTA
processing.Besides,the profile of BCl3+CHF3 etched materials is
sharper than that of BCl3+CF4 etched materials.These results
mentioned above may be due to the higher polymerization rate in
CHF3 plasma.These residues can be removed by buffered HF
dipping.The performance of InP-based HEMT demonstrates gm=300mS/
mm,fT=34GHz and fmax=75GHZ.
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