以多層 TiNi 合金作為砷化銦鎵NMOS金屬閘極材料

Abstract

近年來，很多研究致力於新的材料及結構的開發，對於未來電子元件而言，高效能及低功耗是非常重要的議題。利用金氧半場效電晶體可以有效改善其漏電流、介面缺陷以及功函數等問題的存在。此論文主要研究目的，改善其有效功函數對於電晶體元件之影響。另外，從文獻中可以得知不同的金屬材料擁有不同的功函數，其功函數進而影響平帶能階電壓，不論是高或低的有效功函數，其金屬對氧化層皆有所影響。因此，此研究主要目的是利用多層堆疊的方式，改善鈦鎳合金在氧化鉿/砷化銦鎵之金氧半電容元件的影響。從電性量測分析結果，在經過退火後，其平帶能階電壓增加了0.21V (從-0.11到0.1V)，而鈦鎳合金的有效功函數大約是4.62eV，此有效功函數的值與砷化銦鎵的導帶非常接近。我們也進一步發現，在經過5分鐘400 oC 退火後仍維持非晶相之結構，接著將退火溫度提升至700 oC，經過30秒退火後，發現其鈦鎳合金形成結晶體，此結構能有效地使合金與氧化層介面更加穩定，除了利用低功函數的鈦金屬和氧化鉿內的氧元素作結合，以及將高功函數的鎳金屬，利用擴散方式與氧化鉿界面產生反應。此研究結果發現鈦鎳合金/氧化鉿的介面層比單元素金屬更加的穩定。

For a recent year, the scaling down devices has been launched by new architecture or new materials. High efficiency and low power consumption are significantly important for electronics devices based on a new trend of electronic developments. Metal-Oxide-Semiconductor field effect transistors are concerned particularly because of its advanced properties and performance in terms of low power consumption applications. There are several considerations when studying about MOSFET such as leakage current, interface trap densities, effective work function, and interface fixed charges. This thesis focused intensely on researching the effective work function of metals. It was showed that the flat band voltage and effective work function are in a close relationship which also was inspired by previous reports on gate metals. The fact is that high effective work function metal and low effective work function metals are lead to the degradation of the oxide layer. Therefore, multilayer gate metal TiNi applied on HfO2/InGaAs MOSCAPs has been investigated. Based on electrical measurement results, the intercept of flat band voltage has increased about 0.21V from -0.1 to 0.1V after TiNi/HfO2/InGaAs MOSCAPs was annealed, and the calculated effective work function of TiNi was found approximately 4.62 eV which aligned close to the conduction band of InGaAs. This study also investigated that the amorphous phase of TiNi alloys is highly stable even in the further annealed condition at 400OC for 5 minutes and crystallized until annealed at 700OC in FG for 30 seconds. The formation of TiOxNi interfacial layer was found to prevent the further reaction of low effective work function metal Ti with O2 in HfO2 and further diffusion of high effective work function metal Ni into HfO2 layer. The study also showed that TiNi/HfO2 interface layer is much more stable than the interface layer formed by single metal.