Hi!

No matter polished surface or non-polished one, the chemical etchants still can
remove the silicon substrate. Probably, the etching rate will be affected by the
surface roughness.

There are lots of etchants for silicon, depending on your selection of the
etching mask. For example, for KOH etching in a long period of time, I would
suggest you to choose nitride (around hundreds of angstroms) as your mask layer;
for TMAH etching, you can choose the oxide as your etching mask. The highest
etching rate of TMAH is reported as 81 um/hr (for 8% w.t., 90 degrees
centigrade). If you need further TMAH recipe or information, you can check "P.H.
Chen et al., The characteristic behavior of TMAH water solution for anisotropic
etching on Si and SiO2, Sensors and Actuators A, Vol. 93, pp.132-137, 2001."
Good luck!!

Y.C. Lin

Dept. of Power Mechanical Engineering, National Tsing Hua University, Taiwan.


-- 原始信件內容 --
寄件地址: harish pisipati 
收件地址: [email protected]
寄件日期: 2004-03-16
信件標題: [mems-talk] Back Etching of Si wafer with KOH

Hi,
  I am trying to etch the backside of a n-silicon
wafer. The back side of the wafer is not polished.
Please let me know if the backside needs to be
polished for a faster etch or it doesn't matter. I
learnt from a previous email of the group as how to
protect the front side during a long KOH etch of the
back side. The etchant I planning to use is 50% by
weight KOH solution at 70C. Also please let me know if
you have any suggestions for me during this process.
My target device is a thin diaphragm for a pressure
sensor. If you can please give me any web links that
go through the fab details of a pressure sensor.

Thank you very much.

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-- 原始信件內容結束 --