jonathan d trumbull wrote:
>
> Cheol-Hyun,
>
> > Does anybody know other kinds of polymer films which has good adhesion
> > with silicon in acid or the way to increase the adhesion between
> > polyimide or parylene and silicon?
>
> The only way I have been able to get polyimide and PR to stick during a
> HF:HNO3 etch is to use an adhesion layer of Cr.  Just a 10-20 nm works
> fine.  If you can't use this for whatever reason, you might be out of
> luck.
>
> --Jonathan
>

Jonathan..

My son, a Penn State materials guy, left your note on my computer after
a weekend visit.  I am a recently retired semiconductor engineer from
IBM who worked on silicon processing my entire career. Maybe I can help
you.  I assume you are using the HF-HNO3 to etch a pattern in Si and are
trying to do it using polyimide or parylene as a mask.  As you have
learned, organic materials do not stand up well to HF/HNO3. Since you
say you've used Cr with success and are apparantly not adverse to using
another process step to produce an adhesion layer, allow me to suggest
the following method commonly used in the silicon business to wet etch
silicon or silicon nitride:

1. Deposit a layer of SiO2 (100-200nm) on the Si using either CVD,
plasma deposit, or sputtering.

2. Apply your organic resisit layer over the SiO2 and form your pattern.

3. Wet etch the SiO2 layer with BHF.

4. Remove the organic resist layer.

5. Use the patterned SiO2 as the etch mask to etch the Si with HF/HNO3.

6. Strip the SiO2 (if necessary) with BHF....


Good luck,

Joseph F. Shepard, Sr.
jfshepard@ibm.net