Re: Anisotropic Etching of 3612

Robert,

Sputtering etching is not a great way to etch resist. For one resists tend to have low ion sputter yields and thus a low etch rate/selectivity. For an ion flux of 1 mA/cm2 and an ion energy of 500eV its etch rate is only about 20 nm/m while SiO2 and Al have rates of around 33 and 64 nm/m, respectively. These numbers are from a sputter rate table I have. Note that the MRC at 100w/10mT has an est. ion flux of about 0.1mA/cm2 and a bias around -700v so its sputter rates about 1/10th of the above rates. The PQ has higher ion fluxes but you can not get high bias voltages, if you do manage to get the bias voltage up where you need it for sputtering, you usually get stainless steel sputtering from around the top window where the uwave comes in.

A second issue with sputter etching is that it is not real anisotropic compared to what one can get with plasma etching. The problems with sputter etch wall profiles are faceting at the top corners, which leads to sloped walls, and redeposition. Of course, you need very directional ions, and you are not going them with Drytek4 because it cannot go to low pressures. I guess you cannot add O2 to go the usual way of getting anistropic resist wall profiles.

Jim



----- Original Message -----
From: "Robert Chen" <robertchen@snf.stanford.edu>
To: "labmembers" <labmembers@snf.stanford.edu>
Sent: Thursday, November 8, 2012 12:19:28 AM
Subject: Anisotropic Etching of 3612

Hi All,

I'm looking for recipes to do a sputter etch of 3612, something anisotropic with an etch rate of around 300nm/min. Has anyone tried using Ar in DryTek4 or Ar in pquest to do this?

Thanks,

Robert Chen
Electrical Engineering Ph.D. Candidate
Harris MBE Group, Stanford University
http://robochen.web.stanford.edu