Special measures for chamber are not necessary as long as differences of plasma parameters do not affect device paramters or yield. 

Different plasma parameters have different effects. The electron collision rate indicates variations of the process chemistry, in particular  the state of the chamber wall (conditioning). The electron density indicates hardware related issues such as e-chuck, spare parts, and RF (contact aging, matchbox load and tuning, ...). Therefore plasma parameters are reliable indicators for chamber matching or comparison. Attention: The chamber comparison use a real production recipe and test wafers which are close to production wafers (mask, open area, ...)

Recommended measures for chamber matching are:



Chamber conditioning is one of the most likely reason for chamber mismatch (RF time, gas temperature, etc.).

Hardware check:

Variances in the hardware can lead to chamber mismatch (e.g., matchbox). Other reasons for chamber mismatch are RF contact erosion, feedthroughs, and mechanical parts (wafer handler, slit valve liner door, etc.). Also, check the Baratron and mass flow controller (MFC).

Spare part check:

Spare parts are subject to wear. Therefore they have to be removed and refurbished (or replaced) regularely. Usually, each spare part kit has a kit number which provides information how often it has been refurbished. Keeping track of this information is recommended.


The diagram shows collision rate for two chambers. The outliers are caused by a faulty spare part kit.