垂直型高電壓4H-SiC碳化矽二極體之研發

Development of High-Voltage 4H-SiC Vertical Diodes

鄭期尹(Cheng, Chi Yin)

指導教授 ： 黃智方

國立清華大學/電機資訊學院/電子工程研究所/碩士(2012年)

https://doi.org/10.6843/NTHU.2012.00576

摘要

本篇論文探討4H-SiC垂直型高電壓二極體之研製，包含了PiN二極體以及鈦溝渠式接面位障蕭基二極體。傳統垂直型PiN二極體製作於磊晶基板上，長時間使用會有正向電位降衰退的情形。本篇論文製作於經磨薄過的半絕緣基板上，輔以離子佈植作為N+及P+區域，期能有一良好正向特性，兼有足夠的反向崩潰能力。很可惜地實驗結果並不如預期，在電壓接近200伏特時元件才導通。
溝渠式接面位障蕭基二極體為接面位障蕭基二極體之改良。藉由溝渠式的結構設計，可降低表面電場減少蕭基位障降低效應，使漏電流下降，故此結構可以使用低功函數的蕭基金屬，如鈦。如此便可同時有低的導通電壓卻不會有高的漏電流。在元件設計、製作以及特性探討上，針對不同的溝渠間距、溝渠深度、邊緣保護設計做特性分析，並以模擬去預測元件特性。溝渠式接面位障蕭基二極體元件於反向偏壓900伏特時漏電流為接面位障蕭基二極體的百分之一。在電流密度為100〖 A/cm〗^2時，其中溝渠深度1μm與溝渠寬度2μm的元件，順向電位為1.35伏特，反向漏電流密度約為1×〖10〗^(-3) 〖A/cm〗^2. 當溝渠式接面位障蕭基二極體元件操作於高電流密度時，可觀察到有導電率調變的現象。

關鍵字

碳化矽 ； 二極體 ； 高電壓 ； 垂直型

並列摘要

Abstract
This thesis investigated the design and the fabrication of high-voltage 4H-SiC vertical diodes, including PiN diodes and Ti-TJBSs (Titanium Trench Junction Barrier Schottky Diode). Conventional PiN diode is fabricated on epitaxial wafers. Its forward voltage drop will degrade after stress due to bipolar degradation. In this work, PiN diodes on the thinned HPSI (High Purity Semi-Insulating) wafer were fabricated, with ion implantations to form the n+ and p+ region. It is expected to feature good forward characteristics and sufficient reverse blocking capability. Unfortunately, the experiment results were not as expected, with a large turn-on voltage of 200V.
TJBS is an improvement of JBS. With the trench structure, the p+ region is deeper and the surface electric field can be reduced. In this case, the barrier lowering effect can be reduced. Therefore, TJBS can adopt low work function metal, such as titanium, as its Schottky metal. As a result, a low forward voltage drop can be achieved without suffering high leakage currents. The effects of trench spacing, trench depth, device size, and edge termination have been simulated and analyzed. When a reverse bias of 900V is applied, the leakage current of TJBS is 100 times smaller than that of JBS. As for a current density of 100A/cm2, the forward voltage drop is 1.35V and the leakage current density is about 1×〖10〗^(-3) 〖A/cm〗^2. The phenomenon of conductivity modulation is also observed when the TJBS diodes are operated at high current density in the PiN mode.

並列關鍵字

SiC ； Diode ； High-Voltage ； Vertical

參考文獻

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