矽化鎳和矽化鈷的熱穩定性及電阻研究

Abstract

本論文主要在探討矽化鎳和矽化鈷的熱穩定性及片電阻變化情形,此外, 在本論文中也針對金屬矽化物所引起元件特性的影響做了一些探討,例如 對閘極氧化層的破壞以及P/N接面的漏電流影響. 因為矽化鎳結塊在900度 時就發生,因此它並不適用於高溫製程. 而矽化鈷擁有比矽化鎳較好的熱 穩定性,在我們的實驗中,我們可以發現在1100oC的金屬矽化溫度以下,矽 化鈷可以一直維持相當低的片電阻值. 但是矽化鈷最主要的問題在於金屬 矽化的過程中消耗掉比較多的矽原子層.我們使用矽化物/多晶矽結構作為 閘極電極,可以降低閘極電極的阻值,但也會對閘極的電特性產生不良影 響. 因為矽化鈷所消耗掉的矽比較多而且對閘極氧化層也會造成較大的應 力作用,所以對MOS電容的電特性影響會比矽化鎳的使用更嚴重. 藉由崩潰 電荷,崩潰電場強度,平衡能帶電壓的變化來評估閘極氧化層的特性可發現 矽化鈷的使用會比矽化鎳造成更嚴重的電特性劣化. 此外,較薄的多晶矽 層,較厚的金屬層,以及較高的金屬矽化溫度都會對元件的電特性造成比較 嚴重的損害. In this thesis, we study the thermal stability and sheet resistance behavior of Nickel and Cobalt silicide. Moreover, Silicide induced device degradations such as polycide gate oxide degradation and junction leakage , are also discussed in the thesis. For Ni silicide, because of 900oC starting agglomeration temperature, Ni silicide is not suitable for high temperature processes. For Co silicide, it has better thermal stability than Ni silicide but the major concern needed to be solved is the large Si consumption. As in the experiments, we discovered that Co silicide can maintain a low sheet resistance until silicidation takes place at 1100oC.Polycide gate MOS structure with 6nm thickness of gate oxide and with polycide gate formed from various polysilicon and Co, Ni film thickness was studied. Because Co silicide has larger Si consumption and bigger induced stress than Ni silicide, it was shown that Co polycide structure can result in more server device degradation, such as flat band voltage shift, charge to oxide breakdown, and oxide breakdown field. We also can discover that thicker metal film, thinner polysilicon film, and higher silicidation temperature can also damage the device performance.