Question about etching InAlAs/InGaAs - Alternative masking layers

Jim McVittie mcvittie at cis.Stanford.EDU
Mon Aug 18 11:26:06 PDT 2008

Hi Crystal,

The In material etch process on the PQ is run hot. The chuck temp is set
to around 170C with the sample running near 200C. This is too hot for a
resist mask. You to use either an oxide or a nitride mask. The selectivity
to oxide is around 10:1.


On Sun, 17 Aug 2008, Crystal Rose Kenney wrote:

> In my experiments I have an MBE stack of InAlAs and InGaAs materials. I need to etch down about 150nm and place contacts in those holes. I was initially planning on using photoresist as my mask layer, first by opening the areas to etch and then evaporating metal into the holes and doing liftoff. 
> However, because of the high bias needed to etch InAlAs that doesn't look like a viable option. I do not wish to use two lithography steps of the same mask layer (karlsuss mask) because I am concerned about misalignment issues since I need good contact of metal on the sides of the contact holes. Are there other masking layers that could be used in this case? I need something that could stand a high bias (possibly using pquest) for etching and then use the same mask layer to evaporate metal and then have some way of removing said mask layer. 
> I'm also open to suggestions for alternative processing steps. Thank you in advance for your help.
> ~Crystal Kenney

Jim McVittie, Ph.D.    			Senior Research Scientist 
Allen Center for Integrated Systems     Electrical Engineering
Stanford University             	jmcvittie at
Rm. 336, 330 Serra Mall			Fax: (650) 723-4659
Stanford, CA 94305-4075			Tel: (650) 725-3640

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