疊層阻障層鈦/氮化鈦及氮化鉭應用於銅金屬化及鋁金屬化之研究

Abstract

本研究中，提出一種新穎的疊層鈦/氮化鈦擴散阻障層，並成功的應用在銅金屬化及鋁金屬化之製程。疊層鈦/氮化鈦可阻斷氮化鈦柱狀晶體的的快速通道，並且延緩金屬與矽間的相互擴散。實驗中，係利用物理氣相沉積法沉積金屬薄膜，而疊層鈦/氮化鈦在不破真空情況下依序地沉積在基材上。本研究分別使用TEM，SEM，XRD，RBS，SIMS，AES及AFM分析材料特性，並藉由量測片電阻，接觸電阻及漏電流評估材料阻障的效果。 實驗結果顯示，氮化鈦中置入一層鈦金屬，可使氮化鈦形成不連續晶界。而在鋁金屬化製程中，疊層鈦/氮化鈦比單層氮化鈦具有較佳的阻障效果。但是較多的金屬鈦或較厚的金屬鈦，將提高金屬鈦和鋁的反應，產生較多的鈦鋁化合物且減少氮化鈦的整體厚度，進而影響薄膜阻障效果。所以為了改善阻障效果，應減少金屬鈦的整體厚度。 氮化鈦置入較多的金屬鈦層，可促進銅金屬化製程中的阻障效能，由結果得知銅往矽層的擴散速率減緩，改善了擴散阻障層的阻障特性。此外，本研究使用不同氮流量濺鍍氮化鉭。結果顯示氮化鉭的晶粒尺寸隨著氮流量增加而減小，而氮化鉭薄膜的壓應力亦隨著氮流量增加而降低。因金屬鉭易與矽自發反應產生鉭矽化合物，所以使用較高的氮流量濺鍍氮化鉭可獲得較佳的阻障效果。

In this research, a novel multilayered Ti/TiN diffusion barrier was proposed and successfully applied for Cu and Al metallization. Multilayered Ti/TiN could block fast diffusion path of columnar grain structure in TiN diffusion barrier, and hence alleviates the interdiffusion between metal and silicon. Metal films were deposited by physical vapor deposition, and multilayered Ti/TiN was deposited sequentially without vacuum break. TEM, SEM, XRD, RBS, SIMS, AES, and AFM were used for material characterization. Sheet resistance, contact resistance, and junction leakage current were measured and used to evaluate the barrier performance. It was found that TiN grain boundary was discontinuous while a Ti layer was inserted in TiN. Multilayered Ti/TiN has better barrier performance than single-layer TiN in Al metallization. However, more titanium layer or thickness enhanced chemical reactions between titanium and aluminum, produced more titanium-aluminum compounds, and reduced the total effective thickness of titanium nitride, and hence barrier performance would be affected. Total thickness of introduced Ti layers should be reduced to improve barrier performance. The more titanium layers were inserted in TiN, the more enhanced barriers was obtained in Cu metallization. It was found that the diffusion of copper into silicon was slowed and hence barrier performance was improved. On the other hand, tantalum nitride was reactively sputtered by various nitrogen/argon flow ratios. It was found that grain size of tantalum nitride reduced with increasing nitrogen flow ratio. Compressive stress of the tantalum nitride thin film would lower as sputtering at high nitrogen flow ratio. The barrier performance of tantalum nitride deposited at high nitrogen flw ratio was better because tantalum reacted spontaneously with silicon producing tantalum-silicon compounds.