Every dry clean increases the total process time and decreases the wafer throughput and tool productivity (OEE).
The optimization of a dry clean is not only a question of process stability but also MTBC.
When the dry clean is too short, process stability (first wafers) is affected and more wet cleans can be necessary!
|Dry clean in etch chamber
|Typically, etch processes mostly are very complex because various materials are etched. Therefore, the chamber gets covered with a mix of several byproducts, plasma polymers, and parts of the mask sputtered during the process.
Parameter drift after dry clean shown by the electron collision rate.
|Dry clean at Novellus SPEED
|Due to the use of insulating
material for deposition chamber wall parts,the grounded
electrode is smaller than the RF driven electrode. This means
the energy of the
ions going to the grounded chamber wall is higher than the ion energy
at the RF driven electrode.Therefore the sputter rate in the
back etch step at the grounded
wall is high and leads to a removal of the films deposited during the
deposition. Hence the deposition rate at the wall is much
lower than at the wafer and the ceramic dome.
At the Novellus Speed the bias voltage is usually positve (normal case = negative)