[mems-talk] Minimum feature size using wet etching - 3micro-m?

[Martyn Gadsdon]

Dear All,

I am trying to make a nanowire grating using a simple process. I am spinning 
a layer of photoresist on top of a ~50nm layer of silver or aluminium. The 
photoresist is then exposed and developed to have a sinusiodal profile, of  
between 200 and 300nm pitch, where the troughs of the profile expose the 
metal underneath. I then aim to etch the exposed areas of metal using 
typical chemistries such as H3PO4:HAc:HNO3:H2O to leave an array of parallel 
metallic wires of the same pitch. However, I seem to be having problems and 
never seem to be able to etch the exposed areas.

I have looked into this on the web and came across a short presentation.

The link is:

ccms.ntu.edu.tw/~chihiwu/ch09%20rev3.ppt

and on the slide discussing the disadvantages of wet etching they state:

"Can’t pattern sub-3micro-m feature"

I have worked out they are at the National Taiwan University, but I can not 
find the actual author's name or email address to enquire directly to them, 
so I thought I'd try to see if anyone else can confirm their statement.

Can anyone tell me if this is correct and may be the reason why I cannot wet 
etch my 200-300nm profiles, and if so perhaps provide a reference I can look 
up and quote.

Thank you very much for your time.

Martyn Gadsdon