脉冲压力MOCVD沉积氧化铝薄膜的生长机理及工艺参数控制研究
A study on the growth mechanism and the process parameters controlling aluminum oxide thin films deposition by pulsed pressure MOCVD
摘要：
采用脉冲压力金属有机化学气相沉积（PP-MOCVD）方法，在不同的沉积条件下，在硅衬底上制备了氧化铝薄膜。目前的研究调查的沉积膜的生长机制和薄膜形态的控制，通过改变PP-MOCVD的工艺参数-选择溶剂，浓度和存在的屏蔽。使用仲丁醇铝（ASB）作为铝源，同时使用己烷和甲苯作为溶剂。薄膜在475 ℃下以不同的前体浓度沉积。据观察，溶剂的选择对表面形态没有影响，但它影响沉积速率。无论生长条件如何，提高的沉积速率、相对接近的蒸发焓（ΔH）值和膜的均匀性表明己烷是比甲苯更好的ASB溶剂。本文提出了一种薄膜生长的气相沉积和气相冷凝混合模型，其中五种不同的机理导致了固体薄膜的形成。这些包括在低到达速率下的气相沉积、在高到达速率下的气相沉积、Leidenfrost气溶胶形成、异质颗粒形成和液滴撞击。需要控制的重要参数是前体通量到达速率，其可以通过改变前体浓度、使用具有低ΔH的溶剂以及在衬底上存在屏蔽来控制，这影响膜的表面形态和生长速率。
英文摘要：
Aluminum oxide thin films were deposited on silicon substrates under different deposition conditions using pulse pressure metal organic chemical vapour deposition (PP-MOCVD). The current study investigates into the growth mechanism of the deposited film and the control of the film morphology by varying the processing parameters of PP-MOCVD - choice of solvent, concentration, and presence of a shield. Aluminum sec-butoxide (ASB) was used as the aluminum source while hexane and toluene were used as the solvents. The films were deposited at 475oC at different precursor concentrations. It was observed that the choice of solvent has no effect on the surface morphology, but it influenced the deposition rate. The improved deposition rate, relatively close enthalpy of vaporisation (ΔH) values and uniformity of the film, irrespective of the growth conditions, showed that hexane was a better solvent for ASB than toluene. A hybrid mode of vapour deposition and vapour condensation model for thin film growth is proposed where five different mechanisms lead to a solid film formation. These include vapour phase deposition under low arrival rate, vapour phase deposition under high arrival rate, Leidenfrost aerosol formation, heterogeneous particle formation and liquid droplet impingement. The important parameter that needs to be controlled is the precursor flux arrival rate which can be controlled by varying the precursor concentration, use of a solvent with a low ΔH and the presence of a shield over the substrate, which influences the surface morphology and the growth rate of the films.
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