Ti/NiSi/Si及TiN/NiSi/Si堆疊結構

Abstract

本論文中，我們主要探討矽化鎳（NiSi）的材料特性與應用於超大積體電路上的相關製程技術。首先是探討矽化鎳的片電阻效應熱穩定性，當製程溫度超過700℃時，矽化鎳片電阻的大幅上升將會限制其在高溫製程上的應用。因此為了改善矽化鎳的特性，我們用了兩種多層堆疊金屬結構來增加矽化鎳的熱穩定性，分別是鈦/鎳/矽（Ti/Ni/Si）和氮化鈦/鎳/矽（TiN/Ni/Si）。含鈦和氮化鈦的多層金屬結構很明顯的改善了矽化鎳在片電阻方面的熱穩定性。以鈦為保護層的矽化鎳P/N接面可以在鈦的保護下，阻擋了在矽化的過程中氧原子的進入。而以氮化鈦為保護層的P/N接面則是因為氮化鈦中的氮和矽反應產生氮化矽層，所以在矽化過程中氮化矽層阻擋了氧原子的進入。因此含鈦以及含氮化鈦的多層金屬結構下的矽化鎳片電阻特性非常相似，其在800℃高溫處理下仍能保持穩定的低片電阻值。此外我們也探討氟離子或氮離子的植入對矽化鎳影響。在形成P/N接面之前，先利用氮離子或氟離子的植入來改善矽化鎳的特性，提高了矽化鎳在高溫應用上的可能性。我們發現到氟離子的植入可以讓矽化鎳的片電阻在製程溫度超過800℃時才開始大幅上升。而且有氮離子和氟離子植入之P/N接面的漏電流也比沒有植入的減小了許多。這是因為氮離子和氟離子減緩了鎳跟矽的反應，使得矽化鎳（NiSi）轉變為矽化二鎳（Ni2Si）的溫度大幅提高。

In this thesis, we have studied basic material properties of nickel silicide and some key process technology relevant to ULSI applications. First, sheet resistance behavior of Ni silicide was investigated. The degradation of sheet resistance occurred at 700ºC limits the applications of Ni silicide in high temperature procedure. In order to improve the performance of Ni silicide films, we proposed two kinds of bilayer structures, Ti/Ni/Si and TiN/Ni/Si, to improve the thermal stability of NiSi. Ti- and TiN-contained bilayer structures clearly improved the thermal stability of sheet resistance. Ni silicide p+/n junction using Ti as a capping layer can suppress oxygen contaminant during silicidation. And Ni silicide p+/n junction using TiN as a capping layer can form a nitride layer to prevent NiSi oxidation. Hence, the characteristics of sheet resistance for Ti- and TiN-contained bilayer structures are very similar. It can maintain a low sheet resistance after 800ºC RTA treatment. Moreover, the influence of nitrogen or fluorine implantation on Ni silicide was also considered. Nitrogen or fluorine implanted before p+/n junction formation can improve the thermal stability, and enhanced the possibility of applications to Ni silicide in high temperature procedure. We find that fluorine implantation can slow down sheet resistance degradation of Ni silicide and let it greatly increase only after 800ºC annealing. Besides, with fluorine or nitrogen implantation also reduced the leakage current of Ni silicide p+/n junction. This is because that nitrogen and fluorine retarded the reaction of Ni and Si, and the temperature for NiSi transforming into NiSi2 was increased.