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
-Pen-Tung Sah MEMS Research Center,
-Xiamen University, CHINA
XMU HOME:
http://memsc.xmu.edu.cn/mems_renchaiduiwu/XuYuan_Chen-Group/index_1.html