Diamond Wafer in Electronics Applications

Progress in power electronic devices is currently accepted through the use of wide bandgap materials (WBG). Among them, CVD diamond is the material with the most promising characteristics in terms of breakdown voltage, on-resistance, thermal conductance, or carrier mobility.

Silicon is a well-established semiconductor material that has addressed the requirements of energy conversion for more than 50 years. However, it is widely recognised that a real step-improvement in power electronics will be obtained by employing devices based on wide bandgap semiconductor materials. These materials have superior electrical characteristics for power devices when compared to silicon. Many grid applications use multilevel converters, with 3.3 kV (4.5 kV IGBT pressed (or stack) pack is commonly used fo HVDC and now 6.5 kV is also commercially available) silicon power semiconductors that need to be set in series to reach the required voltage level. Higher voltage capability devices are then highly required, 15 kV being a first step. To reach a high level current, paralleling of devices is required. Power electronic devices based on wide bandgap semiconductors are now resulting in substantial improvements in the performance of power electronics systems by offering higher blocking voltages, improved efficiency and reliability (higher performance/cost ratio), easier paralleling, and reduced thermal requirements, thus leading to the realization of more efficient green electronic systems.

Among wide bandgap semiconductors, diamond is considered to be the ultimate semiconductor for applications in high-power electronics due to its exceptional properties. Its dielectric breakdown strength is three times higher than in silicon carbide (SiC) and more than 30 times higher than in silicon (Si). In addition, unlike most other WBG semiconductors, the carrier mobility is very high for the CVD diamond, and the thermal conductivity is unsurpassed. Power device engineering is interested in minimising the on-resistance for a given breakdown voltage capability. Diamond is the best candidate, and even Ga2O3, despite its lower carrier mobility, is better than SiC and GaN thanks to its high critical electric field.

An important aspect to rise is that Si power semiconductor switches used in 90% of the power applications market are metal-oxide semiconductor (MOS) gate-controlled devices (vertically diffused metal-oxide semiconductor, VDMOS, IGBT). Thyristor-based structures (integrated gate-commutated thyristors IGCT; gate turn-off thyristors, GTO) are still used for high-power high-voltage applications, mainly because of the lack of equivalent performance MOS controlled devices. This is something that diamond could solve considering its very high breakdown field above 10 MV/cm. In general, WBG semiconductors could open the way to novel concepts and applications in the high-voltage field such as electric transport and energy generation and distribution.

Diamond, as a material with exceptional properties, could provide solutions to industry by providing diodes and transistors that withstand voltages above 10 kV.

CSMH focuses on the R&D and production of diamond wafers. It has excellent R&D capabilities, excellent independent innovation capabilities, more than ten years of technology accumulation, and continuous breakthroughs in core key technologies. It is committed to becoming the world's leading wide-bandgap semiconductor materials and devices. The company's core products are wafer-level diamond heat sinks, GaN-on-diamond epitaxial wafers, aluminum nitride films and piezoelectric materials.

The company has the ability to design MPCVD equipment. It is the first company in China to master the core process of MPCVD to prepare high-quality diamond and realize mass production. It also creates an efficient and precise machining method for the atomic-level surface of diamond based on plasma-assisted polishing. The roughness is reduced from tens of microns to less than 1 nm, reaching the standard of semiconductor-level applications. High-power semiconductor lasers using diamond wafers have been used in optical communications, and are also used in laser diodes, power transistors, and electronic packaging materials.