In situ chemical sensing in AlGaN∕GaN metal organic chemical vapor deposition process for precision film thickness metrology and real-time advanced process control

In situ mass spectrometry is implemented in AlGaN∕GaN∕AlN metalorganic chemical vapor deposition processes on SiC substrates as a real-time process- and wafer-state metrology tool. Dynamic chemical sensing through the process cycle, carried out downstream from the wafer, revealed generation of methane and ethane reaction by-products as well as other residual gas species. The methane and ethane by-products are believed to reflect the two parallel chemical reaction pathways leading to GaN-based materials growth, namely the gas phase adduct formation route and the direct surface decomposition of the metalorganic precursor, respectively. Having detected both types of by-products as evidence for the presence of both paths, we monitored and integrated the methane and ethane signals to derive a real-time film thickness metric. Integrating the sum of the two by-product signals in this manner through the AlGaN growth period (∼1min or less) enabled us to predict the AlGaN cap layer thickness (∼20nm) to within ∼1% o...