In situ chemical sensing in AlGaN/GaN high electron mobility transistor metalorganic chemical vapor deposition process for real-time prediction of product crystal quality and advanced process control

Gallium nitride and its alloys promise to be key materials for future semiconductor devices aimed at high frequency, high power electronic applications. However, manufacturing for such high performance products is challenged by reproducibility and material quality constraints that are notably higher than those required for optoelectronic applications. To this end, in situ mass spectrometry was implemented in AlGaN∕GaN∕AlN∕SiC metalorganic chemical vapor deposition processes 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 byproducts, as well as other residual gas species. Using the methane/ethane ratio, the GaN epilayer crystal quality was shown to be predictable in real time to a precision of 2%–5%. This was verified by postprocess x-ray diffraction using the full-width at half-maximum height of GaN on-axis (002) and off-axis (102) rocking curve peaks as a me...