利用雷射退火改善離子佈值後P型4H-碳化矽及蕭基二極體之電性研究

Abstract

近年來由於環保意識抬頭，在綠能省電必須有所改善，避免能源浪費，功率元件在產品上的材料應用有所突破，因為碳化矽本身的優異材料特性相較於矽，有著更好的省電模式，因為碳化矽有著相對於矽十倍大的臨界電場值，由於這個原因可以大幅減少磊晶層的厚度以及減少元件的導通電阻。蕭基二極體的導通電阻主要受三種阻值影響，包括磊晶層阻值、基板阻值、歐姆接觸阻值。為了降低接觸電阻，可以透過製成方式來減少接觸電阻來改善元件的導通電阻。在蕭基二極體的順向偏壓，利用一些方式調整元件的導通電壓值，例如，更換金屬或利用退火方式改善。為了增加元件的崩潰電壓，通常會在金屬與半導體邊緣做一層保護，以降低邊緣的電場值。有些方法是在n型碳化矽中利用離子佈值形成p型碳化矽，來減少在逆偏時的產生的大電場。但目前在活化p型碳化矽的退火溫度非常高，以及在爐管退火完之後會劣化碳化矽表面粗糙度，降低元件的崩潰電壓。而本篇利用248nm波長KrF雷射退火來改善此現象，並討論受體載子是否有活化以及改善棚離子的擴散現象。

In recent years, due to the rise of environmental awareness, Green energy saving must be improved. To reduce power dissipation, the breakthrough of power device used in material which can improve performance . Due to material property of SiC was batter than Si, and SiC had better performance of power loss. The breakdown field of SiC was ten times higher than Si. It could be significantly reduce the thickness of epi-layer and on-resistance of device. The on resistance of schottky barrier diodes was composed of the resistance of epi, substrate and ohmic contact. For reducing the resistance of ohmic contace, we could use the way of annealing to reduce the on resistance of device. In forward bias characteristic of Schottky barrier diodes, we could deposit different schottky metal or the condition of annealing way to adjust the forward voltage of schottky barrier diodes. Usually it will deposit a passivation between metal and semiconductor for raising the breakdown voltage of device. Some of way to raise the breakdown voltage was using ion implantation to form p-type SiC in n-type SiC which could reduce the electric field between metal and semiconductor. But now there has some problems in activating P-type SiC. Due to annealing temperature in furnace is very high, which will cause the degradation of surface of SiC. It will reduce the performance of breakdown voltage. This letter will use 248-nm KrF Laser annealing system to improve the problem. Discussing whether the acceptor activation and the phenomenon of B atoms diffusion.