化學機械研磨用納米氧化鋁粉之合成

Abstract

近年來在半導體工業中，積體電路為了要達到0.35μm以下的線寬以及多重金屬連線，全面平坦化是必須的，而最能夠達成全面平坦化要求的技術就是化學機械研磨。在化學機械研磨時所使用的研磨液需要有大量納米級粉體懸浮於漿液中，所以本實驗研究利用化學法來製作能達此一要求之納米級的氧化鋁粉體。 本實驗以鋁醇鹽經水解再經過煆燒後來獲得超微細氧化鋁粉末，發現鋁醇鹽水解與粉末煆燒均會影響粉末最後之性質。不同水解條件如溶媒種類、水量等會明顯地影響後續煆燒時的相變化及粉體在水溶液中的粒徑分佈情況，並可藉由煆燒條件來控制所形成氧化鋁的組成相。本實驗中以異丙醇為溶媒所製得之粉末，在水溶液中會有較良好的分散效果。在單一粒徑方面，θ- Al2O3粉末的粒徑在10∼30nm，α- Al2O3粉末的粒徑在50∼200nm之間，皆可達到納米級粉末之要求。 本實驗並以合適的煆燒條件來控制氧化鋁粉體之相組成，再進行二氧化矽薄膜之化學機械研磨，探討磨除率、不均勻度、粗糙度以及刮痕之影響。本實驗所製得之粉末對照商用粉末之研磨效果後，發現混合相(α+θ)的氧化鋁粉末對二氧化矽薄膜有較高及穩定的磨除速率，及可接受的粗糙度與均勻度。在研磨後的表面粗糙度方面，若氧化鋁粉體主要組成相為α相時，會因為較大的粒徑而造成較大的表面粗糙度及較多的刮痕；反之若組成相主要為θ相時，較小的粒徑在研磨後可獲得最佳的表面粗糙度以及較少的刮痕。

Recently, global planarization has became indispensable in the IC industry in order to obtain line width smaller than 0.35 μm and for multiple metallization connection process. The most capable technique to achieve global planarization is chemical mechanical polishing (CMP), in which process large amount of ultrafine (nano-sized) abrasive powders are dispersed in the appropriate solutions forming the CMP slurries. The present work intends to prepare the nano-sized Al2O3 CMP powders using chemical method. The study employs the method of hydrolyzing aluminum alkoxide to produce ultrafine alumina powder. It is found that both of the hydrolysis and the subsequent calcining processes will affect the properties of as-formed powder. The hydrolyzing condition, e.g. solvent and water content etc., apparently play the important roles in the phase transformation during the subsequent calcining stage and the dispersion of powder in aqueous medium. It is also found that the constituent phases of as-formed alumina are controllable through appropriate calcining conditions. The as-formed powder prepared from isopropanolic medium has good dispersion in the deionized water. Sizes of various phase aluminas range between 10-30 nm for θ- Al2O3 and 50-200 nm for α- Al2O3, and this obviously meet the nano-sized CMP powder requirement. Finally, CMP of silicon oxide is performed using as-formed alumina powders of controlled phase constituents; effects on removal rate, non-uniformity, roughness and abrasive characters are studied. It is found that, comparing the as-formed powders with commercial powders, by using mixed α+θ alumina higher and more stable removal rate allied with acceptable roughness and uniformity can be achieved on CMP of silicon oxide thin film. Theα-alumina powder usually gives rise to more scratches and rougher surface finish due to its larger particle size; on the contrary, polishing with theθ-alumina powder usually results in less scratches with uniform roughness owing to its smaller particle size.