On-Line Hydride Gas Process Monitor for Silicon and Compound SemiconductorFabrication. Phase 1

摘要

The fabrication of silicon and gallium arsenide compound semiconductors requiresthe use of hydride gas precursors such as arsine, phosphine, and silane. The accurate sensing of the concentration of these gases is essential for high yield device fabrication. Presently the methods for detecting these gases for on-line process control are very expensive ($18,000 to $35,000). These units are based on ultrasonic time of flight measurements, mass spectrometry, or FTIR spectrometry. Some of these sensor technologies are prone to coating of the sensor element so that their accuracy decreases with time. Other sensors do not operate below atmospheric pressure. The inability to monitor and control the concentration of these gases directly affects the process repeatability and hence the quality of the semiconductors fabricated. This is especially true with ternary and quaternary compound optoelectronic materials such as AlGaAs and AlGaInAs, where the stoichiometry of each element must be correct for the device to be fabricated as desired. Therefore, development of an on-line sensor for process monitoring and control will enhance productivity of semiconductor manufacturing. The sensor will find applications in chemical vapor deposition (CVD), gas phase molecular beam epitaxy (MBE), silicon doping, and plasma deposition equipment.