number of polymide wall contribution to process gas is reduced thereby creating a cleaner process a cleaner process results in less frequent maintenance the procedures for cleaning in both etch and deposition systems are basically the same of course the gases used will differ depending upon what material is to be removed from the internal surfaces in general the procedure is given by the flowchart of fig4 in the first step of cleaning a bias voltage is applied to the bias shield the bias voltage employed should never be high enough to result in physical sputtering of the surfaces sputting redistributes wall species and when the wall is clean contaminates the chamber with wall material all of the removal should occur chemically chemical cleaning means that the contamination species are removed from the chamber in the exhaust stream this implies that the gas pressure used for cleaning should be high gt 100 mtorr secondly all internal chamber surfaces should be heated to minimize recondensation further the surfaces are heated to lessen the chance that condensate removed from one surface will redeposit on another surface the law of conservation of filth states u201c you cannot get anything clean without getting something else dirty but you can get everything dirty without getting.