China Achieves Breakthrough in 6-Inch AlN Single Crystal Composite Substrate and Wafer Manufacturing Process

Recently, the Songshan Lake Materials Laboratory's third-generation semiconductor team, in collaboration with Professor Jincheng Zhang and Professor Xiangdong Li from Academician Yue Hao's group at Xidian University, and Guangdong Zhien Technology Co., Ltd., successfully developed high-performance GaN HEMTs wafers based on 2-6 inch AlN single crystal composite substrates.

Thanks to the material advantages of the AlN single crystal composite substrate (dislocation density on the order of 2×10⁸ cm⁻²), the thickness of the AlGaN buffer layer was reduced to 350 nm, significantly lowering epitaxy costs while effectively controlling wafer warpage.

Research found that impurities such as Si and O on the surface of the AlN single crystal composite substrate can cause parasitic leakage channels, preventing proper HEMT device shutdown. In response, the team innovatively proposed a method of regrowing an AlN buried layer to cover the impurity layer, preventing ionization in the ultra-wide bandgap material, thus significantly suppressing leakage.

Experimental results showed that the lateral breakdown voltage of the proposed 350 nm undoped ultra-thin AlGaN buffer layer easily surpassed 10 kV, with the HEMTs achieving an off-state breakdown voltage exceeding 8 kV, dynamic current collapse below 20%, and threshold voltage drift below 10%. The reliability evaluation was preliminarily passed.