應用鈀/鍺/銅歐姆接觸至砷化銦鎵之全面銅金屬化磷化銦鎵/砷化鎵異質接面雙載子電晶體

Abstract

在這篇論文中，成功的發展出使用鈀/鍺/銅歐姆接觸至N型砷化銦鎵上，且成功的運用至全面銅金屬化磷化銦鎵/砷化鎵異質接面雙載子電晶體中。 在低溫退火(250°C)下，鈀/鍺/銅歐姆接觸即具備了低接觸電阻(1 x 10-6 Ω-cm2)。經由X光繞射儀、歐傑電子縱深分析、穿透式電子顯微鏡和能量分散式X射線分析的分析結果，鈀/鍺/銅歐姆接觸形成機制和微結構反應都已被研究了解；且鈀/鍺/銅歐姆接觸經過250°C、24小時的熱穩定測試後，其接觸電阻幾乎沒有變化。 接著將鈀/鍺/銅歐姆接觸應用至全面銅金屬化磷化銦鎵/砷化鎵異質接面雙載子電晶體，並使用鉑/鈦/鉑/銅為P型砷化鎵歐姆接觸、鈦/鉑/銅為連接導線（其中鉑為銅之擴散阻障層）。量測結果顯示，全面銅金屬異質接面雙載子電晶體的直流特性和使用傳統金金屬化的特性相當；此外，將元件施以在高電流密度100kA/cm2之電流加速測試24小時後，其元件特性也並沒有明顯改變。結果顯示將鈀/鍺/銅歐姆接觸應用至全面銅金屬化磷化銦鎵/砷化鎵異質接面雙載子電晶體其元件特性十分的優異。

The Pd/Ge/Cu ohmic contacts to n-type InGaAs is investigated. The Au-free fully Cu-metallized InGaP/GaAs HBTs using Pd/Ge/Cu ohmic contact to n-type InGaAs also has been successfully fabricated for the first time.

Low specific contact resistivity of 1x10-6 Ω-cm2 was achieved at a low annealing temperature (250 °C). The ohmic contact formation mechanisms and microstructure evolution were investigated using x-ray diffraction (XRD), Auger electron spectroscopy (AES) depth profiles, transmission electron microscopy (TEM) and energy dispersive spectrometer (EDX). The thermal stability test of the Pd/Ge/Cu ohmic contact on InGaAs was also performed at 250 °C for 72 hours and showed no obvious degradation on Pd/Ge/Cu ohmic contact after the annealing. In addition, the sheet resistance got to high temperature of 550 °C for 20min also showed no obvious rising.

The Pd/Ge/Cu ohmic contact was applied to the fully Cu-metallized InGaP/GaAs HBTs as the emitter and collector metals. The base metal was Pt/Ti/Pt/Cu, SiNx was used for passivation, and Ti/Pt/Cu was used for interconnect metals with Pt as the diffusion barrier. The common emitter I-V curves and current gain (β) of these Cu-metallized HBTs using Pd/Ge/Cu ohmic contact on InGaAs cap layer showed similar electrical characteristics as those for conventional Au-metallized HBTs.

The high current test was performed at a high emitter current density of 100kA/cm2 for the fully Cu-metallized HBT with Pd/Ge/Cu ohmic contact showed almost no obvious degradation in electrical characteristics. The results show that the novel Pd/Ge/Cu ohmic contact can be used on InGaAs Cap layer of fully Cu-metallized InGaP/GaAs HBTs exhibit good device performance.