Zou, The particulars of the power are dependant on the electrode geometry, i.e. assuming a capacitive reactor diameters and spacing of the electrodes. -Mike Martin U. of Louisville >>> "Xiaojing Zou"09/22/06 6:14 PM >>> Thanks a lot for your information. Since you have experience in this case, I'd like to ask more about the etching process. What is the RF power do you use ??? I found some group use 300-500 W high power, while others use 25W. Do you know what is the difference between them???