MOCVD Process Introduction

When the MOCVD device mixes the II or III metal organic compound with the hydride of the IV or V element to pass into the reaction chamber, when the mixed gas flows through the surface of the heated substrate, the thermally decomposition reaction occurs on the surface of the substrate, and epitaxial growth A monocrystalline film. Compared to other epitaxial growth technologies, MOCVD technology has the advantage: (1) Each component and dopant for growth compound semiconductor material are accepted into the reaction chamber in a gaseous manner, and therefore, the gaseous source can be accurately controlled. The flow and interworking time control the component, doping concentration, thickness, and the like. Can be used to grow thin layers and ultra-thin materials. (2) reaction

The MOCVD device mixes the II or III metal organic compound with the hydride of the IV or V element to pass into the reaction chamber, and the mixed gas flows through the surface of the substrate, and the heat decomposition reaction occurs on the surface of the substrate. It is epitaxial to grow the compound single crystal film. Compared to other epitaxial growth techniques, MOCVD technology has the advantage:

(1) Each component and dopant for growth compound semiconductor material are gaseous The reaction chamber is accessed, and therefore, the components, doping concentrations, thickness, and the like can be controlled by accurately controlling the flow of gaseous sources and the interworking time. Can be used to grow thin layers and ultra-thin materials.

(2) The gas flow rate in the reaction chamber is faster. Therefore, when the components and doping concentrations of the multivariate compound are needed, the possibility of reducing the memory effect can be reduced. This facilitates the severity of the steep interface, suitable for the growth of heterogeneous structures and superlattice, quantum well material.

(3) The crystal growth is carried out in a thermally solved chemical reaction, and is an epitaxial growth in a single temperature zone. As long as the uniformity of the reaction source airflow and temperature distribution can be controlled, the uniformity of the epitaxial material can be ensured. Therefore, suitable for multiple pieces of epitaxial growth, which is convenient for industrialized mass production.

MOCVD的工作流程图

, the crystal growth rate is proportional to the flow rate of the III source, and therefore, the growth rate adjustment range is wide. The faster growth rate is suitable for mass growth.

(5) Use more flexible. In principle, as long as the suitable raw material can be selected, the MOCVD growth of the material containing the element can be made. It is more different from the type of metal organic compound which is available as a reaction source, and has a certain difference.

(6) Due to the low requirements of vacuum, the structure of the reaction chamber is simpler.

(7) With the development of detection techniques, the growth process of MOCVD can be monitored.

In fact, for MOCVD and MBE technologyIt is noted that the performance of the epitaxial structure and the device used is not very different. The most attractive place for MOCVD technology is its versatility, as long as it is possible to select a suitable metal organic source, epitaxial growth can be performed. And as long as the uniform distribution of airflow and temperature can obtain large-scale uniform materials, it is suitable for large-scale industrial production.

Most of the main disadvantages of MOCVD technologies are related to the response sources used. The first is that the metal organic compound and hydride source are expensive, followed by partial sources of flammable and explosive or poisonous, therefore has certain hazards, and after the product needs to be harmlessly treated to avoid causing Environmental pollution. In addition, since other elements (such as C, H, etc.) employed are contained in the source, it is necessary to carefully control the reaction process to avoid introducing non-intentionally doped impurities.

The process of typically MOCVD growth can be described as follows: The reactive source material that is accurately controlled is in carrier gas (usually H2, and there are also N2) The reaction chamber that is introduced into the quartz or stainless steel is carried out, and the surface reaction occurs after the substrate, and the substrate is placed on the heated base. The exhaust gas remaining after the reaction is scavenging from the reaction chamber, and the system is discharged by removing the particulate and toxic exhaust gas treatment device. The MOCVD work is shown in the figure.

MOCVD workframe

A MOCVD growth device can be scaled to the following 4 parts.

(1) Gas operating system:

gas operating system includes controlling III metal organic sources and V The gas stream of the hydride source and all valves, pumps, and various equipment and pipes used in their mixtures. Among them, it is most important that the amount of raw material for reacting the reaction chamber is accurately controlled. It mainly includes a mass flow controller (MFC) controlling flow, a pressure controller (PC) controlled by pressure, and a water bath constant temperature controlled to metal organic source (ThorMal Bath.

(2) Reaction chamber:

The reaction chamber is the core component of the MOCVD growth system, the reaction chamber Design is a crucial impact on the effect of growth. Different MOCVD equipment manufacturers have different designs of the reaction chamber. However, the final purpose is to avoid the presence of from the wall jet and turbulence in the reaction chamber, ensuring only the laminar flow, thereby achieving a uniform distribution of the airflow and temperature in the reaction chamber, which is advantageous for uniform growth. There are three main methods of the substrate in the MOCVD system: radiofrequency heating Infrared radiation heating and resistance heating. In the radio frequency heating mode, the base of the graphite is heated by the radio frequency coil by inducing coupling. This type of heating is often used in large reaction chambers, but the system is usually too complicated. In order to avoid the complexity of the system, in a slightly small reaction chamber, an infrared radiation heating method is usually used. The thermal energy generated by the halogen tungsten lamp is converted to infrared radiation energy, and the base of the graphite absorbs such radiation and converts it back heat. In the resistance heating method, the thermal energy is provided by current flow through the metal base. (4) Tail gas treatment system: Most of the sources used in the MOCVD system are flammable It is exploding, and the hydride source in the rain has a poisonous, so the reactive exhaust gas must be treated. The method usually used is to remove the exhaust gas to the particles (e.g., P ornaments) of the microparticles (e.g., P,,,,,,,,,, using a detoxification solution using a detoxification solution. Another way of detoxification uses a combustion chamber. A high temperature furnace is included in the combustion chamber, and the material in the exhaust gas can be picked and oxidized at 900 to 1 000 ° C, thereby achieving harmlessness. The product produced by the reaction was deposited on the inner wall of the quartz tube, which can be easily removed.

Original article,author:zongmuLi,If reprinted,Please indicate the source:http://madedesign.net/index.php/2020/12/25/mocvd-process-introduction/

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