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Research Highlights, Progress towards Practical Application of Diamond Semiconductor Wafers

Energy and Environment
Progress towards Practical Application of Diamond Semiconductor Wafers
YAMADA Hideaki
Advanced Power Electronics Research Center

Production of single crystal diamonds from gas

The world's first crack-free single crystal diamonds with cm3 class volume have been produced using the microwave plasma CVD method with gas as the raw material.

Figure: cm<sup>3</sup> class single crystal diamond produced from gas (left), and commercially available single crystal diamond substrate manufactured using the high temperature high pressure method (right)
cm3 class single crystal diamond produced from gas (left), and commercially available single crystal diamond substrate manufactured using the high temperature high pressure method (right)

Diamond - the highest level of semiconductor material

Diamond has multiple electrical and thermal physical property values that rank among the highest of all substances, and widespread application is expected over diverse fields such as spintronics and more advanced generation power electronics. However, the lack of a supply system for large-size wafers is a barrier to practical application. This research used the Strategic Innovation Promotion Program (SIP) to challenge technology for increasing single crystal sizes, which is a bottleneck issue.

Photo: Single crystal diamonds

A large step towards realization of large-sized wafers

This research produced some of the world's largest crystals by a method that uses gas as the raw material, which makes it easy to scale up the synthesis area. When using the conventional method, the thickness achieved by a single synthesis is limited to the sub-millimeter order, and cracks occur when lamination is performed multiple times to achieve a thick film. To overcome these issues, simulations were conducted to drastically modify the synthesis equipment and review the synthesis conditions. These results enabled to synthesize a thickness of 2 to 5 mm with a single synthesis, and to grow crystals without cracks even when forming a thick film.

Photo: Single crystal diamonds

Accelerate development of next-generation power semiconductors

High quality inch-class single crystal semiconductor wafers will be produced as a base for realizing diamond power semiconductors, with the objective of social implementation.

Photo: YAMADA Hideaki

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