What is an MPCVD system?

1. Diamond‑growth technology is becoming increasingly familiar to the public, and the development of MPCVD equipment has also reached a new stage. So, what exactly is MPCVD equipment?

MPCVD, known in Chinese as microwave plasma chemical vapor deposition, is an outstanding diamond‑growth technology. Its operating principle involves generating microwaves via a microwave source; under the influence of the microwave field, the process gases are excited into a plasma state. A plasma is an ionized gaseous substance composed of positively and negatively charged ions formed when some electrons are stripped from atoms and atomic clusters. The plasma takes on a spherical shape and forms on the diamond substrate, with its high temperature enabling the substrate to be heated to a specified level. Using an MPCVD system with 5 kW of microwave power, it is possible to deposit tool‑grade, heat‑sink‑grade, and optical‑grade diamond films at rates on the order of micrometers per hour.

MPCVD equipment can deposit high-purity diamond films, and the deposition rate can be increased by boosting the microwave power. Device designers have reduced the microwave frequency from 2.45 GHz to 915 MHz. When using an MPCVD system operating at 915 MHz, the microwave power can be significantly elevated; this increase in power substantially accelerates the diamond‑film deposition rate, thereby lowering production costs and enhancing manufacturing efficiency. Typically, MPCVD systems at 2.45 GHz have microwave powers that do not exceed 8 kW. Reducing the microwave frequency allows for a larger cross-sectional area of the standing-wave cavity, which in turn expands the effective deposition area. Consequently, the diameter of the deposited diamond film grows from 50 mm at 1.5 kW microwave power to 250 mm at 75 kW microwave power.

2. MPCVD equipment plays a crucial role in the diamond industry—so what advantages make it the preferred choice?

Diamond is also hailed as a semiconductor, owing to its wide bandgap, high breakdown electric field, high carrier mobility, and high thermal conductivity. However, in industrial applications, the demand for large‑size, high‑quality single‑crystal diamond remains substantial, posing a major bottleneck that limits its broader adoption. Consequently, through ongoing research and development, MPCVD technology has emerged as one of the most promising approaches, thanks to its microwave energy’s non‑polluting nature, the relative purity of its gaseous precursors, and the absence of catalysts or impurities—advantages that set it apart. MPCVD primarily relies on electrodeless discharge, yielding a clean plasma; moreover, its microwave discharge zone is highly localized rather than diffuse, enabling the activation of various atomic species such as atomic hydrogen. The resulting ions possess low kinetic energy, thereby avoiding etching of the already grown diamond and providing protective benefits to the growing layer.

Because the microwave power in MPCVD equipment can be adjusted continuously and smoothly, the deposition temperature can vary steadily over a wide range. This enables MPCVD to overcome the major drawback of DC arc‑discharge CVD—namely, the frequent ignition and extinction of the arc, which subject both the substrate and the diamond film to severe thermal shocks, leading to easy delamination of the diamond film from the substrate. As a result, diamond films deposited by MPCVD are much less prone to peeling off. Compared with hot‑filament HFCVD, MPCVD avoids the contamination of the diamond film caused by evaporation from the hot metal filament, as well as the filament’s sensitivity to highly corrosive gases such as high‑concentration oxygen and halogen‑containing species. Consequently, MPCVD allows for a far broader selection of process gases than HFCVD, thereby reducing unnecessary losses. In contrast to oxy‑acetylene flame‑based methods, by optimizing the design of the MPCVD reaction chamber, it is possible to generate a large‑area, stable plasma sphere within the deposition chamber, facilitating uniform, large‑area deposition of diamond films. Thus, the superiority of MPCVD—employing microwave‑plasma technology—for preparing diamond films stands out prominently among all available techniques.

3. In which fields and industries can MPCVD equipment be applied?

The growth and deposition of diamond, as we know it, are inseparable from MPCVD equipment, because achieving high‑quality diamond films requires the use of such systems. The resonant cavity of an MPCVD reactor lacks internal electrodes, thereby eliminating contamination caused by electrode arcing. Moreover, MPCVD operates over a broad range of process pressures, producing plasmas that are dense, spatially extensive, highly stable, and free from contact with the chamber walls—thus preventing wall‑induced contamination of the film. In the past, industry typically relied on conventional magnetron power sources in MPCVD systems, a practice adopted when no superior alternative was available. However, with rapid technological advances, replacing magnetrons with solid‑state RF/microwave power sources has emerged as a new trend in MPCVD applications. Consequently, the MPCVD method, with its distinctive advantages, has become one of the most promising approaches for depositing high‑quality diamond films. It is also well suited for growing optical, electronic, and tool‑grade diamond coatings, as well as single‑crystal diamond and graphene, while playing a significant role in surface treatment and the low‑temperature growth of oxide layers.

MPCVD equipment can also directly grow graphene on target substrate materials; for instance, within the temperature range of 240–700 °C, it can fabricate high‑quality graphene on various substrates, thereby further expanding the scope of graphene’s applications in the microelectronics field.