CONDITIONING / ONE PRODUCT: PRODUCT AND PROCESS MIX
Process mix means using recipes with different chemistries in one
chamber. This usally leads to first wafer effects.
If a product or process mix is unavoidable, the first wafer effect can
controlled by product management. The optimum of the
product or process
switch depends on tool and process. The following link shows a comparison
processing or almost dedicated chamber operation
The deposition of byproducts at the chamber wall and in the vacuum
system leads to memory effects - when the underlying chemistry is
changed. This is due to diffusion of 'old' byproducts from the
system back into the chamber. It takes sometimes more than one wet
cycle to reach the new chemical
equilibrium. The example below shows that about 4000
wafers needed to
a stable process.