Korean researchers identify internal structure of 'killer defect' in SiC power semiconductors

Demand for high-voltage, high-quality silicon carbide power semiconductors has surged in recent years. Yet mass-producing these high-value devices has proven difficult, as killer defects that arise during epitaxial growth continue to undermine manufacturing yields.

Trapezoidal defects larger than 1,000 micrometers are among the most destructive, capable of rendering an entire chip unusable. Despite their severity, the precise mechanism by which they form and expand had remained one of the field's most persistent unsolved problems.

A research team led by Na Mun-gyeong at the Korea Electrotechnology Research Institute's Next-Generation Semiconductor Research Center has, for the first time in the world, identified the internal structure and formation mechanism of these killer defects — a critical type of manufacturing flaw in silicon carbide (SiC) power semiconductors. The team conducted the research jointly with a group led by Hong Soon-gu, a professor at Chungnam National University, and analytical firm Horiba STEC Korea.

SiC power semiconductors are compound semiconductors in which silicon and carbon are bonded in a 1:1 ratio. Compared with conventional single-silicon power semiconductors, they can withstand voltages ten times higher and operating temperatures three times greater, making them a next-generation solution for maximizing power conversion efficiency.

SiC power semiconductors are completed through an epitaxy process, in which carbon and silicon atoms are stacked layer by layer with precision atop a substrate — a process comparable to weaving thread into fabric. Even the slightest misalignment in the atomic arrangement can produce killer defects, also known as stacking faults, which sharply reduce the yield of entire semiconductor chips.

These defects had previously been understood to share the same fundamental characteristics as other known defects, differing only in size and shape.

The joint research team focused on unusual striations observed inside trapezoidal defects — features that had gone unnoticed until now. To uncover the true structure of the defects, the team combined eight analytical techniques, including photoluminescence mapping, spectral analysis, atomic-level interpretation and density functional theory calculations. The effort drew on some of South Korea's most advanced national research infrastructure — among them a high-resolution scanning transmission electron microscope at the Gumi Electronics and Information Technology Institute, the Nurion supercomputer at the Korea Institute of Science and Technology Information, and synchrotron equipment at the Pohang Light Source — and was carried out over more than a year.

The team discovered that trapezoidal defects in fact contain multiple interlocking faults — up to 32 layers deep — arranged in a complex internal structure. The researchers also confirmed that during the manufacturing process, defects propagate into the epitaxial layer, a thin film built up by stacking semiconductor material, and that they can spontaneously change shape and expand. Researchers and industry observers expect the findings to provide a direct foundation for achieving defect-free wafer yields in mass production.

"This is a meaningful achievement — the first in the world to reveal, at the atomic level, the complex internal structure and evolution of the large trapezoidal defects that have long degraded power semiconductor performance," Na said. "We will continue to work with a sense of mission at the forefront of research, so that South Korea can advance beyond SiC material self-sufficiency and emerge as a technology powerhouse leading global power semiconductor dominance."

The findings were published in Acta Materialia, an international journal covering materials science.