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Research on Major Technology of MOCVD Gas Delivery System

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Tutor: LiuSheng;GanZhiYin
School: Huazhong University of Science and Technology
Course: Subtle manufacturing engineering
Keywords: MOCVD,Gas delivery system,Pressure stabilization,Constant flow
CLC: TN304.055
Type: Master's thesis
Year:  2008
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MOCVD (Metal Organic Chemical Vapor Deposition) is the technology to grow high quality semiconductor material films. It can be applied in many fields such as LED, semiconductor laser device and solar cell. The cost of existing MOCVD equipments is very high, which are strongly dependent on importation. Therefore it is thoroughly necessary to carry out the research of MOCVD equioment, whether to the semiconductor field, new energy and the advanced technology development of national defence.MOCVD equipment can be divided into several systems:reactor chamber system which is the nuclear part of the equipment, calefaction and cooling system, gas delivery system and the control system of the equipment. This paper is mainly foucs on the gas delivery system, constitute structure and control technic related in this system. Also personal opinion about the developing orientation of gas delivery system is given in this paper.The fuction of gas delivery system is incuding transportation of all the gases to the reactor and then to the exhaust for waste treatment after reaction. This system constitute of source gas providing system, Run/Vent main pipes sysem, source pipe system, purge gas system,exhaust system and leak test. After being purified and dried in the source gas providing system, part of the H2 (or N2) flowed to the Run/Vent main pipes system as dilute gas, and part of it flowed through the source pipe system as carrier gas. The carrier gas then flowed to the Run/Vent system with MO sources, and finally flowed to the reactor, while the after reaction gases were delivered to the exhaust system. As the pipes in the chamber are very complicated, and to avoid any cliff deposition, it is needed continually gas purging. Meanwhile, the equipment needed periodical leak test checkment for safty.The control over pressure stabilization and constant flow is very important. Pressure stabilization includes three related system: one is the chamber pressure control located in the exhaust system. This closed loop control system is consisted of pressure transducer, pressure controller and throttle valve. The other system is by seting the input point of the PC to control the pressure inside the bubber which contains MO source. The third one is the differential pressure control system in the Run/Vent main pipe line. Designing of the two Make up lines is based on the auto-compensation theory. It maintains a constant flow into the reactor at all times by switching the two lines between Run and Vent.
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