Optical access to the wafer for the in-situ process monitoring and control is a requirement for the advanced MOCVD equipment. Depending on their location and design, viewports can affect the reactor flow dynamics and temperature distribution inside the growth chamber thus ultimately affecting the deposition process. Furthermore, deposition on the viewport can influence the accuracy of in-situ measurements.

We have investigated viewport influence on the MOCVD vertical rotating disc reactors manufactured by EMCORE Corporation. Viewport transmittance was established for different conditions and viewport types. Computational fluid dynamics was utilized to establish conditions at which viewport has no considerable influence on deposition results. The validity of model predictions was verified by examining the results of actual deposition runs on the reactor. We have demonstrated that under typical EMCORE reactor operating conditions, viewports presence on the reactor inlet flange and a purge flow through it have minimal effect on the reactor flow dynamics and ultimately on material growth rate and thickness uniformity.