Hello everyone!

I am a undergraduate student in Peking University, China.

I have been doing some experiments on silicon dioxide sacrificial layer
etching lately. And I used 4 parts NH4F (40%), 2 parts glycerin and 1 part
HF(40%) as the etchant. I noticed that the etching rate of silicon dioxide
was about 5000A/min at room temperature, far above those rates reported in
literatures even without heating. Can the fabrication method of SiO2 make
such a big difference in etching rate? Or is there any other possible
explanations for that?

Also, I found that Aluminum's etching rate was lower when the etchant
solution's temperature increased. Does that make any sense? Since normally
the etching rate should go up when heated, right? I tried to explain this
from a chemical kinetics' point of view, but was limited because of my major
(electrical engineering). So was that I screwed up my experiments? (though I
hope it's not likely) Or would anyone can tell me the reason, please?

Thank you for your time!

Best wishes!

btw, are there any differences between glycerin and glycerol? Their Chinese
meanings are exactly the same.

--
Yours, Travis (Xiaoning, Wang)
Undergraduate Research Assistant
MEMS Research Center
Institute of Microelectronics
School of Electrical Engineering and Computer Science
Peking University, Beijing, P.R.China