I. Introduction
In recent years, with the development of the semiconductor industry and the advent of the high-speed optoelectronic information era, LPE, VPE and other technologies have become less and less important in the semiconductor industry. Compared with MOCVD technology, MBE is more complicated and more expensive than MOCVD technology. It has a slow growth rate and is unsuitable for pC-long compound single crystals containing high vapor pressure elements (such as P), which is not suitable for industrial production. Metal Organic Chemical Vapor Deposition (MOCVD) was proposed in 1968 by Manasevit et al. of Rockaway Corporation of the United States to prepare a new single crystal film for the substrate; it was put into practical use in the early 1980s. After nearly 20 years of rapid development, it has become one of the key technologies for the preparation of semiconductor materials. It is widely used in the preparation of various thin film materials including semiconductor devices, optical devices, gas sensors, superconducting thin film materials, ferroelectric/ferromagnetic films, and high dielectric materials.
Second, the main technical characteristics of MOCVD
Most of the MOCVD equipment manufactured at home and abroad use a gaseous source to transport the film. The gaseous source MOCVD equipment transports the MO source to the reaction chamber in a gaseous state. The gas transported in the transport pipeline is controlled by the flow rate of the MO source fed to the reaction chamber. Therefore, it is required for the MO source precursor to have high vapor pressure and good thermal stability. The deposition of some functional metal oxide films by gaseous source MOCVD requires that the selected metalorganic materials should have high molecular stability at high vapor pressures to avoid decomposition during transport. However, due to the complex composition of some functional metal oxides, it is difficult to synthesize a gaseous MO source and a liquid MO source having a higher vapor pressure, and a MO source precursor having a low vapor pressure and poor thermal stability cannot be bubbled. The bubbler is transported by the carrier gas to the reaction chamber.
However, the use of liquid source transport is an important research direction at home and abroad. The liquid source is sent to the vaporization chamber to obtain a gaseous source material, and then sent to the reaction chamber through flow control, or the liquid precursor is directly injected into the reaction chamber, and vaporized and deposited in the reaction chamber. The advantage of this method is that the source transportation mode is simplified, the requirements on the source material are reduced, and the alternate deposition of a plurality of films is facilitated to obtain a super-characteristic structure.
Third, the advantages and disadvantages of MOCVD technology
MOCVD technology has unique advantages in thin film crystal growth:
1. It can prepare high-purity film materials at a lower temperature, reducing the thermal defects and intrinsic impurity content of the materials;
2, can reach the atomic level precision control film thickness;
3. The mass flow meter is easy to control the composition and doping amount of the compound;
4. Through the rapid and dead zone switching of the gas source, the type or proportion of the reactants can be flexibly changed to achieve a sudden change in the interface of the film growth interface. Achieve a steep interface;
5. The film growth can be completed in a large area, uniformly and highly reproducibly. Suitable for industrial production;
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