碘乙烷催化劑對銅化學氣相沉積特性之影響

Abstract

本論文使用自行組建之多腔體式低壓銅化學氣相沉積(Cu CVD)系統，以Cu(hfac)TMVS+2.4wt% TMVS當作先驅物(precursor)，探討以碘乙烷(C2H5I)作為催化劑對TaN基板做前處理，對銅膜沉積過程、銅膜性質以及管洞填充所產生的影響。催化劑的基板前處理係以濺鍍成長的TaN基板在定溫定壓條件下，曝露在碘乙烷的蒸氣之下三分鐘。由於附著在基板上的碘原子具有促進Cu(hfac)分解的作用，因此銅的成核率變快；再者，可能由於基板的表面能減小或銅膜與基板之間的介面能增加，使得銅核顆粒的接觸角(contact angle or wetting angle)變大。實驗結果發現，銅膜在碘乙烷處理過之TaN基板上具有較高的沉積速率、較低的電阻率、以及較強度的Cu(200)晶向成長傾向，但銅膜對基板的附著力則變差。銅膜沉積後在氮氣中施以400oC的後續退火處理可進一步降低銅膜的電阻率，並且改善銅膜表面的粗糙度。到目前的實驗結果顯示，碘乙烷處理對於Cu CVD的管洞填充能力並沒有明顯的改善，但是實驗結果也證實低溫低壓以及高濃度含銅氣氛有利於提昇Cu CVD的填洞能力。

This thesis studies of the effects of C2H5I catalyst on the copper chemical vapor deposition (Cu CVD), including Cu nucleation, Cu film property, and via-filling capability, using a liquid metalorganic compound of Cu(hfac)TMVS with 2.4 wt% TMVS additive as the precursor. Sputter-deposited TaN was used as the substrate for the Cu CVD and the vapor phase C2H5I was used for TaN surface treatment prior to the Cu CVD. The substrate pretreatment by C2H5I enhanced the adsorption of Cu species on the substrate surface, reduced the incubation time of nucleation, and thus accelerated the Cu film formation. The wetting angle of Cu grains nucleated on the C2H5I-treated TaN substrate surface was larger than that nucleated on the control TaN substrate (63o vs. 94o), presumably due to the increase of substrate surface energy and/or the decrease of Cu/substrate interfacial energy. The Cu films deposited on the C2H5I-treated TaN substrate all exhibited higher growth rate and lower electrical resistivity; however, they all exhibited a lower intensity peak ratio of Cu(111) to Cu(200) reflections and a degraded adhesion to the TaN substrate. Post-deposition thermal annealing at 400oC in N2 ambient was able to further reduce the film resistivity and surface roughness. Via-filling capability of Cu CVD by using vapor phase C2H5I substrate pretreatment did not exhibit an obvious improvement. However, it was found that notable improvement in via-filling capability of Cu CVD can be achieved at low deposition temperature, low deposition pressure, and high concentration of precursor species in the gas phase of CVD.