Most likely Cr has pin holes in the film and the HF is penetrating
through it. Sputtered Cr is particularly prone to developing pin
holes. I've had better luck with evaporated Cr.


On Mon, Dec 13, 2010 at 7:49 AM, Xin Yan  wrote:
> Hi everyone,
>
> i want to etch the 7740 about 4 to 20 um deep.  Using Cr with Photoresist
> 5214E  as the mask,  Cr layer was produced by DC sputtering about 200nm
> thick. The etchant is 1 HF : 2 HNO3 : 2 H2O to get high etch rate about
> 2um/min  to the 7740.
>
> we met a problem that  Cr can not stand in this solution even 2minutes.
>  After about 2 min, Cr begin to  peel off.
>
>  In the 49%HF without HNO3, Cr cannot stand even 1minutes.
>
> what cause the Cr so unstable or it is supposed to be like this?  or  i need
> to change the etchant ?
>
> Thank you
>
> Yan Xin