Darren Thomson

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...

Real-time material quality prediction, fault detection, and contamination control in AlGaN∕GaN high electron mobility transistor metalorganic chemical vapor deposition process using in situ chemical sensing

Gallium nitride and its alloys promise to be key materials for future heterojunction 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 meet this challenge, in situ mass spectrometry was implemented in AlGaN∕GaN∕AlN metalorganic chemical vapor deposition processes as a real-time process and wafer state metrology tool. In particular, the various pregrowth gas phase impurity levels within the reactor, measured by mass spectrometry in real time, were correlated to photoluminescence band-edge and deep-level properties measured postprocess. Band-edge intensities increased and deep-level intensities decreased with lower oxygen-containing impurity levels in the pregrowth environment. These real-time indications of oxygen impurity incorporation were used for fault detection and to ...

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...