Hi Everybody I am exposing PMMA as a negative resist.I am trying to etch Silicon by using PMMA as mask.Gases used are Oxygen(30 SCCM) and CF4(6 SCCM) ..I tried it for 5 min and 30 min.Unfortunately whole PMMA gets removed and I don't have anything left on Silicon wafer..Can anybody please suggest me the appropriate gases , power , etch time and gas pressure Thank You Karan