about PRs in the etch rate chart

Mary Tang mtang at snf.stanford.edu
Wed Sep 28 06:50:38 PDT 2005

Hi Hyeun-Su --

This is a generic photoresist which is no longer supplied, but is pretty 
comparable to the AZ3612 that we use now. The Olin Hunt and AZ3612 (and 
all the other standard resists) are sufficient for masking etch in BOE, 
but not for 49% HF -- resists will become holey and peel in 49% HF (I 
should add that the etch rate chart you have is from Berkeley -- it's 
quite correct, but some of the entries require some interpretation. The 
Olin Hunt is listed as "P", for peeling, and "0" for no measureable etch 
rate -- which I think really means that it could not really be measured, 
not that it doesn't etch.)

If you are doing a shallow etch (few microns) and your geometries are 
larger (>10 microns), you could probably use 7 microns of SPR220, 
hardbaked for any hour or so at 150 C (please do NOT use the singe oven 
for this - use the BlueM or hotplate instead.) If you need a deeper etch 
or finer structures, you will need a hard mask. Most commonly used are 
Cr/Au (which can be deposited in metalica) or amorphous silicon (a 
better film, but you have to send this out for deposition -- we have 
some wafers in stock which may work for you -- ask me.) We've got 
process diagrams and etch rates which I hope to post some day when I get 
around to finishing them -- if you're interested, let me know and I'll 
forward what I've got to you.

Good luck!


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

Hyeun-Su Kim wrote:

> Dear Lab members,
> Is anybody familiar with photoresist name OCG 820 or Olin Hnt? I found 
> these names from etch rate chart 
> http://snf/Process/WetProcessing/WetER2.pdf . I am looking for good 
> masking material for the glass wafer etching with HF in wbgeneral. 
> According to the chart, they seem to have zero etch rate in the HF; 
> however, I can ’ t find any vendor who deals with them. They may be 
> discontinued or have different names now. Could you please share your 
> valuable experiences about these PRs or any good masking material for 
> HF? Thank you very much.
> hyeun-su (aeonia)

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