Filling of Deep Trench by Epitaxial SiC Growth

Abstract

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.

Review of Silicon Carbide Processing for Power MOSFET

“…The epitaxial growth of SJ by trench filling is shown in Figure 12a and by multi epitaxial growth in Figure 12b. The trench filling epitaxial growth process is done by dry etching at the beginning to form a deep trench, and then, on the trench surface, an epitaxial layer is grown in the trench [167,168]. The multi-epitaxial growth method is a fabrication method that is used to achieve a certain thickness of drift-layer by combining epitaxial growth and the ion implantation method of fabrication [166].…”

Filling 4H-SiC trench towards selective epitaxial growth by adding HCl to CVD process

“…9,10) The line (L) and space (S) dimensions of the line pattern on the mask used for trench lithography were 1 and 1.5 µm, respectively, and the trench depths (D) were about 4.7 and 5 µm, respectively. The HWCVD system with a rotary substrate was utilized.…”

“…7) Therefore, trench filling by epitaxially filling doped SiC into trenches of the opposite conductivity type is considered the preferable method for constructing SiC-SJ structures. [8][9][10][11][12][13][14] In previous literature, 4H-SiC trenches with depths of up to 7 µm and aspect ratios of about 2-4 have been completely or half-filled by using hot-wall chemical vapor deposition (HWCVD) with a conventional gas system, SiH 4 : C 3 H 8 : H 2 . [8][9][10][11][12][13] However, Schöner et al mentioned the necessity of maintaining a slow growth rate and long duration of trench filling to minimize excessive growth outside of the trenches.…”

“…[8][9][10][11][12][13][14] In previous literature, 4H-SiC trenches with depths of up to 7 µm and aspect ratios of about 2-4 have been completely or half-filled by using hot-wall chemical vapor deposition (HWCVD) with a conventional gas system, SiH 4 : C 3 H 8 : H 2 . [8][9][10][11][12][13] However, Schöner et al mentioned the necessity of maintaining a slow growth rate and long duration of trench filling to minimize excessive growth outside of the trenches. 13) Though few details have been released, it is conjectured that the motivation for minimizing the growth outside of the trenches was to avoid the potential risk of void formation (fast closing around the trench's top corner) during long-duration growth.…”

“…Apparently, overgrowth on the mesa requires the additional process of device planarization (polishing) after the growth, and therefore, it degrades productivity. [8][9][10][11] In the CVD filling of a Si trench, to minimize the excessive growth on the mesa top and trench top corner, Yamauchi et al reported a nonmasked method of filling Si trenches by flowing HCl and SiH 2 Cl 2 together. HCl was added to prevent growth around the trench tops, which was predicted based on the fact that the reaction of Cl-Si is faster than that of Si-Si.…”