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 ...
Dynamic rate and thickness metrology during poly‐Si rapid thermal chemical vapor deposition from SiH4 using real time insitu mass spectrometry
Real‐time in situ mass spectrometry has been applied to poly‐Si rapid thermal chemical vapor deposition (RTCVD) (from SiH4) on thermally grown SiO2 as a way to determine film thickness at the end of the process and to infer dynamic deposition rate during the process for run‐to‐run and real‐time control applications. Monitoring process ambient at 5 Torr is achieved using two‐stage differential pumping of a sampling aperture in the exhaust stream, and a rapid response time (∼1 s for a ∼30 s process cycle) allows for real time sensing of reactant input, product generation, and reactant depletion. Active mass spectrometric sampling of the reaction by‐product (H2 generated by SiH4 decomposition) provides a monitor of the total reaction/deposition rate during poly‐Si RTCVD in the range 550–850°C. Product generation as a function of temperature is readily distinguished from reactant cracking fragments by spectral analysis. A well‐defined monotonic correlation between the time‐integrated H+2 product signal and th...
Vapor pressures of the adducts formed during AlGaN organometallic vapor-phase epitaxy
We have measured the vapor pressure of the adducts of trimethylgallium (TMGa) and trimethylaluminum (TMAl) with ammonia near room temperature. The vapor pressures of the mixtures of the adducts were also measured and found to obey Raoult’s law. Both the gallium and aluminum adduct have a relatively low vapor pressure (410 mtorr and 74 mtorr, respectively, at 19°C), which places limits on the design and operation of AlGaN organometallic vapor-phase epitaxy (OMVPE) reactors. Adduct condensation may also be the explanation for numerous observations of powders and crystals inside OMVPE reactors.