ONE CHAMBER: CONDITIONING

Plasma chambers need a wet clean at regular intervals due deposit at the chamber wall (etch byproducts). Afterwards, the chamber has to be conditioned for routine production. The layer at the chamber wall must be similar to the state when the process runs usually without any problems (POR = Process of record). Therefore, chamber pre-treatment by a conditioning procedure is a very important.

Conditioning processes usually run:

After wet clean
Before process or recipe change
After dry clean.

The conditioning process can be optimized by monitoring plasma parameters (electron collision rate, electron density). Oncethe plasma parameters are have reached a steady state, the conditioning process is complete. Monitoring plasma parameters enables dynamic conditioning and is indicative of successful wet clean or other maintenance procedures. Optimization the conditioning procedure can increase throughput and uptime due to potential time savings and reduced number of conditioning wafers.

REASON	DESCRIPTION
After wet clean	The number of wafers needed for conditioning is mostly determined empirically. Often, too many conditioning wafers are used for the process, which decreases tool uptime and Overall Equipment Effectiveness (OEE). Sometimes, it is necessary to use different wafers (e.g., blank, oxide, resist) for chamber conditioning. These wafers affect plasma chemistry and chamber wall configuration, and can actually reverse the conditioning process. These de-conditioning effects cannot be controlled by tool parameters, and may lead to process instabilities and yield loss.
Process or recipe change	The film composition at the chamber wall depends on the process (chemistry, wafer). Mixed different processes changes the chamber wall properties and usually require reconditioning. Reconditioning depends due to flaking may also occur when mixing processes with different plasma chemistries.
After dry clean	Deposition, and sometimes etch processes, need additional in-situ dry cleans to avoid excessive films at the chamber walls, and prevent particles generation due to flaking. The dry clean procedure is geared towards etching back deposits at the chamber wall and restoring surface properties. Additional conditioning (also warm-up or dummy wafers) depends on the process.