銅金屬化之磷化銦鎵/砷化鎵異質接面雙載子電晶體製作及其特性量測

Abstract

自從IBM成功的將銅金屬化導入超大型積體電路矽基版製程後，銅金屬化被廣泛的運用至工業界中。但是至今在砷化鎵元件中，有關於銅金屬化製程的研究報告依然十分的少，所以研發N型砷化鎵銅金屬化歐姆接觸對於銅金屬化之異質接面雙載子電晶體的發展是十分重要的；因此本論文將鈀/鍺/銅歐姆接觸應用至N型砷化鎵及將鉑/鈦/鉑/銅應用至P型砷化鎵歐姆接觸上，以鈦/鉑/銅為連接導線（其中鉑為銅之擴散阻障層），最後亦成功的製作出銅金屬化磷化銦鎵/砷化鎵異質接面雙載子電晶體。 本論文的實驗結果顯示，在低溫退火下，鈀/鍺/銅歐姆接觸就具備了低接觸電阻；且最低接觸電阻發生在250°C退火20分鐘後，其電阻值為5.73 x 10-7 Ω-cm2。而銅金屬化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；在功率特性方面，射極面積為4x20μm2之元件，其功率效率37%。此外，在高電流密度100kA/cm2之電流加速測試24小時後，其元件特性穩定，且將元件施以200°C、24小時的熱處理後只有些微的改變。這些結果顯示以鈀/鍺/銅及鉑/鈦/鉑/銅為歐姆接觸可將銅製程金屬化應用在磷化銦鎵/砷化鎵異質接面雙載子電晶體。

Copper metallization has been extensively used in the silicon industry since IBM announced its success in silicon VLSI process. However, even though copper metallization has become very popular in the fabrication of Si devices, there are only a few reports on the copper metallization of GaAs devices. So developing a Cu-metallized ohmic contact for n-type GaAs to implement Cu-metallized GaAs HBTs is important. In this study, the Cu-metallized InGaP/GaAs HBTs using Pd/Ge/Cu ohmic contact to n-type GaAs and Pt/Ti/Pt ohmic contact to p+-type GaAs and Ti/Pt/Cu for interconnect metals with Pt as the diffusion barrier has been successfully fabricated. The Pd (150 Å)/Ge (1500 Å)/Cu (1500 Å) metal structure forms a low contact resistance ohmic contact to n-type GaAs at a low annealing temperature. The lowest specific contact resistivity is 5.73 x 10-7 Ω-cm2 when annealed at 250 °C for 20 min. The common emitter I-V curves of these Cu-metallized HBTs showed similar electrical characteristics as those for HBTs metallized with conventional Au-metallized HBTs. The power efficiency of 4x20-μm2-emitter-area of Cu-metallized devices was about 37%. During both the current-accelerated stress test (100 kA/cm2 stress for 24h) and the thermal stability test (annealing at 200°C for 24 hours), the Cu-metallized HBT with Pd/Ge/Cu ohmic contact showed slightly degradation in electrical characteristics. The results show that the novel Pd/Ge/Cu ohmic contact and Pt/Ti/Pt/Cu ohmic contact can be used on Cu-metallized InGaP/GaAs HBTs, and exhibit good device performance.