Request to use lampoly or p5000 to etch semi-clean wafers

Mary Tang mtang at
Fri Oct 9 12:00:16 PDT 2009

Hi Nahid --

It's agreed, your request is approved for both the poly etch chamber in 
p5000etch and in lampoly, with the EBR considerations you describe.



Nahid Harjee wrote:
> SpecMat,
> I am designing a process to fabricate single crystal silicon 
> cantilevers that are 3 um thick. The narrowest cantilevers are 14 um 
> wide and have 4 "legs" at the clamped end that are 2 um wide. I am 
> trying to select a tool to etch the 3 um of silicon to define the 
> cantilever that will produce straight sidewalls. In the past, I have 
> used stsetch to define wider cantilevers. However, I am concerned that 
> the scalloping resulting from this tool will make it difficult to etch 
> the 2 um legs of the new design. Thus, I am writing to propose that I 
> perform this etch with HBr/Cl2 chemistry in lampoly or p5000. What 
> makes this process non-standard is that my wafers will be semi-clean 
> at this point. The step prior to defining the cantilevers is 
> deposition of 1500 A of Al in gryphon which is then patterned with a 
> wet etch in Al-11. During the Si etch, the Al will never be exposed to 
> the plasma (it will be covered by 3 um of resist). However, there is a 
> chance that there will be trace Al on the exposed Si from the Al-11 
> bath. At the most recent process clinic, Keith Best raised the point 
> that there may be exposed Al in the EBR region of my wafers. In order 
> to minimize this possibility, I can use 5 mm EBR for the Al litho and 
> 2 mm EBR for the cantilever litho, ensuring there's a buffer of 3 mm 
> of resist with no Al below it.
> I look foward to hearing your decision on the proposed process or if 
> there is a tool that is better suited for this process, I welcome any 
> suggestions.
> Thanks,
> nh
> -- 
> Nahid Harjee
> Ph.D. Candidate
> Electrical Engineering
> Stanford University
> 408-761-8651

Mary X. Tang, Ph.D.
Stanford Nanofabrication Facility
CIS Room 136, Mail Code 4070
Stanford, CA  94305
mtang at

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