Patent Document ID: 5461559
Application ID: 08131536
Patent Flag: 1

Claim One:
1. A hierarchial control system for controlling and improving epitaxial thin films grown with molecular beam epitaxy (MBE), using a plurality of MBE Knudsen cells which supply fluxes of different elements, each Knudsen cell having a heater and a shutter; the control system being arranged in a hierarchy comprising: input-output control means for MBE instrumentation; inner-control-loop means that qualifies MBE process dynamics prior to MBE growth; self-directed-control-loop means that quantifies MBE growth progress in-situ for precise film thickness, composition, and interfacial sharpness; and data transfer means using inter-application communications for transferring data among individual control units; wherein the input-output control means comprises sensor and actuator interfaces coupled to temperature and flux sensors and to the shutter for each Knudsen cell, and a PID (Proportional, Integral, Derivative) controller coupled to the heater of each Knudsen cell to control the temperature; wherein the inner-control-loop means comprises an adaptive gain bandwidth (AGB) unit which includes means for quantifying thermal dynamics of the MBE Knudsen cells, using temperature data and PID algorithm data for a Knudsen cell from the input-output control means via said data transfer means; a beam equivalent pressure (BEP) calibrator unit which includes means to quantify flux emission from each Knudsen cell, using temperature data and ion beam pressure data for a Knudsen cell and ion gauge from the input-output control means via said data transfer means; and a shutter opening transient compensator (SOTC) unit which includes means to quantify the effects of shutter cycle loading on the effective flux emission from each Knudsen cell, using temperature data and ion beam pressure data and shutter data for a Knudsen cell and ion gage from the input-output control means via said data transfer means; and wherein the self-directed-control-loop means comprises a growth control unit which includes means for essential recipe execution, using temperature, BEP, and shutter opening transient data from the AGB, BEP, and SOTC units via said data transfer means; a flux setpoint control unit which includes means to calculate precise Knudsen cell thermal setpoints for required flux output density, using temperature and BEP data for the Knudsen cell from the input-output control means and BEP unit via said data transfer means; and expert system inference engine means for guiding recipe flux requirements via in-situ sensor data, using temperature, pressure, and shutter data from the input-output control means and the AGB, BEP, and SOTC data from the respective AGB, BEP, and SOTC units via said data transfer means.