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Reactive ion etch of GaAs and Al0.3Ga0.7As using BCl3 (boron
trichloride) and SF6 (sulfur hexafluoride) gas mixture is
described , and compared with the results using SiCl4
(silicon tetrachloride) and SF6 g-as mixture . There is
obvious difference in etching rate for both GaAs and
Al0.3Ga0.7As etch using BCl3/SF6 and SiCl4/SF6 gases.
The effect of the variables such as power , pressure ,
and gas compositions on the etch rate and resulting
etched surface morphology are studied . in theis study, the
gas composition of BCL3/SF6 used is 9/1, at theis gas
composition, the ethcing is nost effective. If SF6 ratio is too
high, it's found that both GaAs and Al3 Ga0.7As have poor etch
rage. When BCl3/SF6 ratio is 9/1 and low power, high GaAs to
Al0.3Ga0.7As selectivity can be obtained. However, when etched
at higher pressure, the etch rage of Al0.3Ga0.7As can be
slightly faster than GaAs. In this thesis, the best eching
selectivity between GaAs/AlGaAs is about 100 when Bcl3/SF6 are
used and about 200 when SiCl4/SF6 are used. This is due to the
fact that boron can react with fluoride easier than aluninum.
This fact also results in higher AlGaAs to GaAs eching rete
(selectivity>3), which is not observed when using SiCl4/SF6 as
the etching gases.
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