Title :
Control of a III-V MOCVD process using ultraviolet absorption and ultrasonic concentration monitoring
Author :
Flynn, Monique Gaffney ; Smith, Roy ; Abraham, Patrick ; Denbaars, Steven
Author_Institution :
Litton Guidance & Control Syst., Draper (C.S.) Lab., Cambridge, MA, USA
fDate :
9/1/2001 12:00:00 AM
Abstract :
Metalorganic chemical vapor deposition (MOCVD) is a key technology for the growth of compound semiconductors. This process has traditionally lacked real-time growth monitoring and control, which limits the precise reproducibility needed for high performance devices. Two complementary control approaches for the MOCVD process are investigated experimentally. The first one is a feedforward disturbance rejection strategy using ultrasonic concentration measurements to reject source gas bubbler disturbances. The second one is a feedback system using an ultraviolet absorption sensor for real-time monitoring of reaction chamber gas concentrations. Post-growth X-ray diffraction and photoluminescence of InP/GaInAs superlattice test devices are used to evaluate the control system performance
Keywords :
MOCVD; closed loop systems; computerised monitoring; feedback; process control; real-time systems; semiconductor device manufacture; US concentration monitoring; compound semiconductor growth; disturbance rejection; feedback; feedforward; metalorganic chemical vapor deposition; process control; reaction chamber; real-time systems; ultraviolet absorption; Chemical technology; Chemical vapor deposition; Electromagnetic wave absorption; Feedback; Gas detectors; III-V semiconductor materials; MOCVD; Monitoring; Reproducibility of results; Ultrasonic variables measurement;
Journal_Title :
Control Systems Technology, IEEE Transactions on
