The biggest improvement over the old G5 WW is that the wafers can be loaded at a very high temperature (~1000C) while the reactor is still "hot" from the previous run which takes place at 1600C. For a big chamber with eight 6" wafers, cooling it to room temperature for a human to load the wafers takes very long time. It would also take less time to heat it back up to 1600C. The robot now takes care of hot loading and unloading the wafers. Using cartridge also reduces particles contamination significantly.
There are single wafer or smaller reactors (3 wafers) that can be cooled quicker because the reactors are small. However, they can only run small number of wafers per run. That is the reason the throughputs of G5 WWC are significantly higher.
One concern I have was such high productivity reactor reduces the number of reactors needed by the customers. Aixtron must commend very high prices for such reactors to make up for that.
The key is to maintain highest wafer quality and at the same time maintain high throughputs. That is determined by controlling temperature uniformity across all the eight wafers in one single run, and can maintain that uniformity for multiple runs even with the robots load and unload at high temperatures.
Another key is to avoid SiC deposition in the chamber which creates the need of chamber cleaning; SiC is very hard and inert and therefore difficult to remove. The WW avoid the deposition of SiC on the chamber wall.
How to maintain very high temperature throughout the reactor and keep the temperature uniform on the wafer surface with the complication of hot loading and unloading with casset function is the technology that Aixtron has developed and implemented into production units, which also means proven repeatability and reliability. |
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