[mems-talk] Question about tri-layer resist.

[Xiaojing Zou]

Hi:

  Currently I am doing dry etch SiO2 with Al or Cr as hard mask, which will be removed by wet etch later. But I always found the surface of the SiO2 will be damaged a little after the wet etch. So I plan to insert a thin layer of "soft materials" (like PMMA) between SiO2 and the metal layer. But a problem occurs when I bake the second resist: the metal layer will crack. The following is what I did:

1. spin and bake the first PMMA (very thin)
2. evaporate the metal layer
3. spin and bake the second resist. During the bake I can see the metal crack.

Does it mean I did not bake the first PMMA "hard"enough??  Do you have better ideas?? Thanks a lot.

Best Regards
Xiaojing Zou