IMPROVING PIRANHA ETCH PROCESS RESULTS IN SILICON WAFER CLEANING
With several key variables interdependent, accurate control with traditional control systems is not easy and results can be varied. The mixture, with periodic addition or spiking with hydrogen peroxide, has a useful life of only about one day. Modutek has developed a control strategy that improves process results while reducing chemical use.
The Modutek “Bleed and Feed” Process Control Strategy Delivers Improved Results
Modutek’s “Bleed and Feed” process control strategy keeps the concentration of the Piranha mixture at the desired level while increasing the lifespan of the mixture. The company uses a two-tank “clean” and “dirty” tank design. When the concentration of hydrogen peroxide in the dirty tank goes down, a small amount of mixture is drained from the tank and is replaced by an equal amount from the clean tank. The clean tank then receives a fresh amount of mixture. The clean tank and dirty tank mixtures and the amounts of the bleed and the feed are all programmable so that the desired concentrations can be maintained for an extended period. Using the “Bleed and Feed” method, the Piranha mixture has a much longer life span
“Bleed and Feed” Control Strategy Advantages
The Modutek “Bleed and Feed” Process Control Delivers Substantial Benefits
With more precise control of the process and a more stable Piranha mixture, Modutek’s “Bleed and Feed” process control improves Piranha etching results. Specific benefits include the following: