[labnetwork] Challenging Oxide Etch Process

[Reger, Ronald K]

Dear Colleagues,

One of our faculty members has a process he needs to run in which nano-scale oxide definition is required to expose a gold contact pad.  With our shared-use RIEs we are very concerned about Au contamination in our etch tools, particularly for our electron device researchers.  We're seeking your input from your facilities whether you may have etch tools that allow Au processing for these specialty kinds of processes, and if you have a procedure for dealing with such contamination.  A generic sketch about what our faculty member needs is shown below.

So, have you dealt with this contamination issue with your multi-use tools before, and how do you deal with mitigating the contamination?  Do any of you have a tool that could be used by this research group?

Thanks very much in advance.

Ron Reger
Birck Nanotechnology Center
Purdue University


Generic process steps:

Fabrication need: metal connection to a sub-micron-size metal pad buried under <=50nm ALD oxide (HfO2 or Al2O3).

Conventional fabrication steps (see sketch attached):
 (1) cover metal pad with etch-resistive metal, e.g. Au,
 (2) ALD-grow oxide (20-50nm),
 (3) define a sum-micron PMMA mask using e-beam lithography,
 (4) dry etch oxide with Au serving as a stop-etch layer (ICP-assisted etch using BCl3 or SF6 gases),
 (5-6) subsequent standard e-beam lithography to connect the exposed Au pad to the outside circuit.

Problem: Au (or any other metal which forms non-volatile compounds in RIE system) may be problematic for some electron device processes and is restricted from being used in shared-use RIE oxide etchers.

Current work-around: for large (>10 micron) pads steps (3-4) can be performed by optical lithography + wet etch in HF. e-beam resists like PMMA are attacked by HF and this work-around cannot be used if sub-micron lithography is needed.
[cid:926E0593-F8D0-4658-9033-EEF1A6A25DF1 at lfytina2.metronetinc.net]

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