鋁摻雜氮化鈦薄膜對銅之擴散阻礙能力的強化現象

本研究利用反應性共生濺鍍（co-sputtering）的方式，在不同的N2／Ar分壓混合比例下，於p型（100）矽晶基材上沉積TiN以及Ti1-xAlxN薄膜，並使用電性量測、掠角X光繞射以及穿透式電子顯微術（TEM）、拉塞福背向散射能譜儀（RBS），探討TiN與微量鋁含量（x = 0.1）的Ti1-xAlxN薄膜的電氣、微結構特性及對銅的擴散阻礙效果。這些結果一致呈現：Al的微量摻雜能調節阻礙層的微結構而顯著地提高對Cu的擴散阻障性能。TEM影像顯示，剛沉積的TiN與Ti0.9Al0.1N薄膜（均40 nm）均具有NaCl結構的單一相。但是，TiN薄膜為孔隙柱狀晶粒，而Ti09Al0.1N則具有緻密的等軸晶微結構。高溫（450-650℃）處理前、後的Si/TiN（或Ti0.9Al0.1N）/Cu金屬化結構之綜合評估結果揭示：Si/TiN/Cu在600℃時會因TiN的晶粒成長，而使Cu沿著其粗大柱狀晶粒擴散進入Si的內部，並形成Cu3Si使得表面銅膜大量消失，導致結構片電阻值之迅速上升。反之，Si/Ti0.9Al0.1N/Cu經過更嚴峻的高溫（650℃）測試以後，其整體結構仍維持十分完整。此種超乎尋常的優異性歸因於Ti0.9Al0.1N薄膜具有較TiN晶粒細微之纖維狀結構，且在高溫環境下並無明顯的晶粒成長現象，因此能較TiN更有效地阻擋銅擴散至矽晶內部。

This work employs grazing-incidence X-ray diffraction (GIXRD), transmission electron microscopy (TEM), Rutherford backscattering spectrometry (RBS), and electrical measurement to examine the effectiveness and failure behavior of sputter-deposited TiN and Al-doped TiN thin films as diffusion barriers for Cu metallization. Results based on these analyses consistently confirmed that the performance of TiN (40 nm thick) can be greatly improved by lightly doping Al of only 10 at.% Al, i.e., Ti0.9Al0.1N. The as-deposited TiN barriers possess a NaCl-type and voided-columnar (~ 5 nm) microstructure, which, upon annealing (≧500℃), are transformed into equiaxed, coarse (~ 20 nm) grains, providing short diffusion routes, i.e., grain boundaries, for Cu to penetrate the TiN, ultimately forming pyramidal precipitates of Cu3Si. Conversely, the Ti0.9Al0.1N barriers still maintain a fibrous, fine (~ 4.5 nm) columnar microstructure after high-temperature annealing, and can be highly effective in retarding Cu penetration.