In this article, the narrow-width effect (NWE) of 4H-SiC MOSFETs with local oxidation of SiC (LOCOSiC) isolation is reported. A channel width-dependent current hump was observed in the subthreshold region for n-type 4H-SiC MOSFETs with LOCOSiC, and a channel width-dependent threshold voltage ( Vth{V} _{th} ) shift was observed for p-type 4H-SiC MOSFETs with LOCOSiC. This unusual NWE arises from the increase in the gate oxide thickness from the channel center toward the isolation edge and is different from the conventional NWE found in local oxidation of silicon (LOCOS) technology, which arises from the charge stored in the parasitic field oxide (FOX) capacitor and lateral dopant encroachment. A H2O diffusion and oxidation model is proposed in this article to explain the growth of a long bird’s beak in 4H-SiC MOSFETs with LOCOSiC. Technology computer-aided design (TCAD) simulations were executed to explore the H2O diffusion behavior of these MOSFETs, and an analytical formula was derived to predict the oxide layer thickness and length of bird’s beak along the diffusion path in the H2O diffusion and oxidation model. The problems caused by the long bird’s beak and unusual NWE can be overcome by increasing the overetching time of the pad oxide removal and marginally decreasing the thickness of the FOX layer. Therefore, the NWE of the LOCOSiC isolation is expected to be weaker than that of the LOCOS isolation because field implantation is unnecessary, and thus, dopant encroachment does not occur in the LOCOSiC technology.

中文翻译：

---

具有 SiC 隔离局部氧化功能的 4H-SiC MOSFET 窄宽效应的建模和表征


在本文中，报道了具有 SiC 局部氧化 (LOCOSiC) 隔离的 4H-SiC MOSFET 的窄宽度效应 (NWE)。在具有 LOCOSiC 的 n 型 4H-SiC MOSFET 的亚阈值区域中观察到了沟道宽度相关的电流峰，并且在 p 型 4H 中观察到了沟道宽度相关的阈值电压 ( Vth{V} _{th} ) 偏移-采用 LOCOSiC 的 SiC MOSFET。这种不寻常的 NWE 是由于栅极氧化物厚度从沟道中心向隔离边缘增加而产生的，与硅局部氧化 (LOCOS) 技术中发现的传统 NWE 不同，后者是由存储在寄生场氧化物中的电荷引起的。 FOX）电容器和横向掺杂剂侵蚀。本文提出了 H2O 扩散和氧化模型来解释采用 LOCOSiC 的 4H-SiC MOSFET 中长鸟嘴的生长。通过技术计算机辅助设计 (TCAD) 模拟来探索这些 MOSFET 的 H2O 扩散行为，并推导出解析公式来预测 H2O 扩散和氧化模型中沿扩散路径的氧化层厚度和鸟嘴长度。由长鸟嘴和不寻常的NWE引起的问题可以通过增加去除焊盘氧化物的过蚀刻时间和稍微减小FOX层的厚度来克服。因此，LOCOSiC隔离的NWE预计会比LOCOS隔离的NWE弱，因为不需要场注入，因此在LOCOSiC技术中不会发生掺杂剂侵蚀。