APCVD Reactor Conclusions

Operational Control: Systems are slow to adjust to temperature changes, and somewhat sensitive to ambient conditions since they are open. Care in tool siting and fab surroundings is important.

Film uniformity: Wafer transport velocity and all gas flows must be very precisely controlled to obtain good uniformity in the direction of wafer travel. (This is relatively easy to do, since operation is continuous, without turn-on transients.) High molar flows mean short diffusion lengths: careful adjustment of gas metering is thus required to obtain good film uniformity perpendicular to travel. Wafer edge effects are significant.

Productivity advantages: Continuous operation without loading or pumpdown delays means potentially high throughput. Continuous operation also means gas controls run in steady-state mode with no transients for turn-on and turn-off.

Productivity disadvantages: Actual area of deposition is much narrower than the wafer, so peak deposition rate is very high for a given average rate. In consequence, average rates may be relatively low for a given film quality. Larger wafers give reduced WPH out for a given deposition rate.

Major changes in operating conditions (especially temperature) take several hours to stabilize.

Periodic manual cleaning of injectors and transport paths are required.

It’s important to note that when toxic chemicals are used, care is necessary to make sure that purge flows between the injectors are sufficient to ensure toxics do not escape into the environment.

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