Summary of MOCVD
MOCVD(Metal Organic Chemical Vapor Deposition) technology, also known as OMVPE, MOVPE, etc., is a new technology proposed by rockwell corporation in 1968 for the preparation of compound semiconductor single thin films. MOCVD technique is to dilute the metal organic compounds in the carrier gas and Ⅴ ethnic or Ⅵ hydride in the heated elements of substrate and decomposition reaction, the products of the reaction, reaction to the epitaxial substrate to form a technology of epitaxial film, this technique can be used to grow the high quality of the nano-scale thin film, it is because of this characteristic makes MOCVD technology is widely applied to the production and manufacture of semiconductor devices [1]. This technology has now become, II, III, V – VI family compound semiconductor devices multilayer structure to grow high quality the most flexible, lowest cost and highest efficiency technology, in recent decades with the semiconductor technology progress as the driving force of the rapid development of IT industry, especially the new semiconductor optoelectronic devices and the rapid development of microwave devices, the huge market demand and the progress of MOCVD technology, makes MOCVD demand huge key core semiconductor manufacturing equipment, optoelectronic industry, is also the most one of the special equipment for the future development. This equipment integrates precision machinery, semiconductor materials, vacuum electronics, fluid mechanics, optics, chemistry, computer and other disciplines as a whole. It is a kind of advanced special optoelectronic equipment with high degree of automation, high price and high technical integration [2]. The MOCVD equipment has been widely used in GaN (gallium nitride) epitaxial growth of semiconductor materials and blue, green or ultraviolet light emitting diode chip, heterojunction bipolar transistor (our HBT), high electron mobility transistor (HFET), solar cells, field effect tube (FET) and optical detector in manufacture and research in semiconductor devices, such as, visible MOCVD has a pivotal position in the semiconductor industry.
Overview of foreign studies
The manufacturing technology of MOCVD equipment is mastered by a few foreign companies, such as AIXTRON from Germany, Thomas Swan and EMF from Britain, Veeco from the United States, Nishia, Nippon Sanso and NissinElectric from Japan, and some companies adopt their own unique MOCVD equipment in the production process.
Principle of MOCVD device:
The MOCVD equipment mainly consists of four parts: gas system, heating system, reaction chamber and detection and control system. The gas system mainly realizes the transportation of the gas source, the accurate control of the gas flow, the accurate and quick switching of the valve and the treatment of the waste gas. The heating system is mainly used to heat the substrate where the reaction takes place, to provide the required temperature for the reaction to take place, and to meet the requirements of uniform heating, fast heating and cooling rate, and short temperature stability. Reaction chamber is the core part of the equipment, the reaction gas after transport system into the reaction chamber, in the reaction chamber and the heating of the surface of the substrate respectively in the gas phase chemical reactions and surface chemical reaction, diffusion, adsorption, adsorption reaction settlement on the substrate after a few complicated steps such as homogeneous epitaxial homogeneous or heterogeneous crystal film; The detection and control system mainly detects the temperature field, film thickness, uniformity and other parameters of the reaction chamber on line, and controls the gas path and heating system.
Heating of MOCVD system has two functions, one for the loading of organic source thermostatic waterbath provide the temperature control of the cylinder, the other is for the temperature of the reaction chamber for epitaxial growth, mainly in the reaction chamber temperature control equipment is on the surface of the graphite slide set bottom heating furnace, by changing the heating furnace of the power to regulate the temperature of the reaction chamber, in order to meet the needs of the epitaxial growth. The core of the heating system design is the design of the heating furnace, MOCVD equipment in the process of growth generally need to about 1500 ℃ heating temperature, the heating furnace of the heating element at least need to be able to bear the high temperature of 2000 ℃ above, we choose material of heating element must be able to withstand the high temperatures, and in the nature of the material under high temperature to be stable, so as to ensure electric furnace heating stably for a long time. At present, the materials suitable for this situation mainly include rhenium, tungsten and tungsten-rhenium alloy.
