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 ...
Real-time sensing and metrology for atomic layer deposition processes and manufacturing
In situ quadrupole mass spectrometry (QMS) has been integrated to an atomic layer deposition (ALD) reactor to achieve real-time chemical diagnostic and wafer-state metrology. The process investigated was tungsten ALD using WF6 and SiH4. The UHV-based substrate-heated ALD reactor incorporated a minireactor chamber to simulate the small reaction volume anticipated for manufacturing tools in order to achieve adequate throughput. Mass spectrometry revealed essential surface reaction dynamics through real-time signals associated with by-product generation as well as reactant introduction and depletion for each ALD half-cycle. The by-product QMS signal was then integrated in real time over each exposure and plotted against process cycle number to directly observe ALD film growth, leading to two valuable metrologies. First, the integrated by-product QMS value changes with cycle number, directly reflecting the nucleation kinetics. Specifically, QMS values increase with cycle number during the nucleation phase and...
High temperature adduct formation of trimethylgallium and ammonia
High temperature gas phase reactions between trimethylgallium (TMG) and ammonia were studied by means of in situ mass spectroscopy in an isothermal flow tube reactor. The temperature, pressure, and reaction time were chosen to emulate the gas phase environment typical of the metal–organic vapor phase epitaxy (MOVPE) of GaN. The main gas phase species is [(CH 3)2Ga:NH2]x, where most probably x=3, resulting from the very fast adduct formation followed by elimination of methane. The further gas phase decomposition of this species proceeds through the stepwise elimination of methane. These studies indicate that little TMG exists within the growth ambient under most MOVPE growth conditions. The further gas phase reaction of [(CH3)2Ga:NH 2]x may be responsible for the strong dependence of the MOVPE GaN growth rate and uniformity commonly observed.