We performed deep trench filling by using epitaxial SiC growth. It was found that the trench filling condition depend on trench width. A high growth temperature was needed to fill a narrow trench and a low growth temperature was needed to fill a wide trench structure. We optimized the filling condition and successfully filled 7μ m deep and 2 μm wide trench without void formation. We also investigated the 2D doping distribution of the filled area by SSRM. As a result, it is found that the existence of a sub-trench was related to the generation of a doping distribution in the filled area. The trench filling mechanism and doping distribution are discussed.

We have tried to fabricate a super junction (SJ) structure in SiC semiconductors by the trench-filling technique. After the deep trench formation by dry etching, epitaxial layer is grown over the trench surface. Doping profile of the embedded p-type epitaxial region between the trenches is evaluated by a scanning spreading resistance microscopy (SSRM). The SSRM result reveals that the doping profile is not uniform and there exists a low concentration region along the trench side-wall. Based on the SSRM result, two-dimensional device simulations are performed using pn-type test structures with the non-uniform SJ drift layer. The simulation result shows that blocking voltage of the test structure can be optimized and becomes comparable to that of the ideal one by adjusting the concentration design of the embedded layer to balance the total charge in SJ structure.

Super-junction (SJ) devices have been developed to improve the trade-off relationship between the blocking voltage (VBD) and specific on-resistance in unipolar power devices. This SJ structure effect is expected in SiC unipolar devices. Multi-epitaxial growth is a known fabrication method for SJ structures where epitaxial growth and ion implantation are repeated alternately until a certain drift-layer thickness is achieved. In this study, we fabricated two types of test elemental groups with an SJ structure to evaluate the breakdown voltage (VBD) and specific resistivity of the drift layer (Rdrift). Experimental results show that VBDexceeded the theoretical limit of the 4H-SiC by 300V, and Rdriftagreed well with the estimated value from the device simulation. The beneficial effects of the SJ structure in the SiC material on VBDand Rdriftwere confirmed for the first time.

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