通过无液CO₂弯月面涂层进行的超薄膜沉积——均匀性和形态

Kim Jaehoon, Novick Brian J, Desimone Joseph M, Carbonell Ruben G

Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27606-7905, USA.

Langmuir. 2006 Jan 17;22(2):642-57. doi: 10.1021/la0521600.

Ultrathin organic films of sucrose octaacetate (SOA) were deposited on 12.5 cm diameter silicon wafer substrates using high-pressure free meniscus coating (hFMC) with liquid CO2 (l-CO2) as a coating solvent. The dry film thickness across the wafer and the morphology of deposited films were characterized as a function of coating conditions-withdrawal velocity, solution concentration, and evaporation driving force (deltaP). When no evaporation driving force was applied (deltaP = 0), highly uniform films were deposited with thickness in the range of 8-105 angstroms over the entire concentration range (3-11 wt%). Uniform films were also obtained at low concentrations (3-5 wt%) with a low evaporation driving force (deltaP = 0.0138 MPa). However, films deposited at medium to high concentrations (7-11 wt%) were thicker (110-570 angstroms) and less uniform, with larger nonuniformities at higher applied evaporation driving forces. Optical microscopy and atomic force microscopy (AFM) were used to characterize film morphology including drying defects and film roughness. Films deposited without evaporation had no apparent drying defects and very low root-mean-square (RMS) roughness (1.4-3.8 angstroms). Spinodal-like dewetting morphologies including holes with diameters in the range of 100-300 nm, and surface undulations were observed in films deposited at medium concentration (7 wt%) and low deltaP (0.0138-0.0276 MPa). At higher concentrations and higher evaporative driving forces, spinodal-like dewetting morphologies disappeared but concentric ring defect structures were observed with diameters in the range 20-125 microm. The film thickness and morphology of SOA films deposited from 1-CO2 hFMC were compared to those deposited from toluene and acetone under normal dip coating. Films deposited from l-CO2 hFMC were much thinner, more uniform, and exhibited much fewer drying defects and lower RMS roughness.

使用以液态二氧化碳（l-CO2）为涂布溶剂的高压自由弯月面涂布法（hFMC），将八乙酸蔗糖酯（SOA）的超薄有机膜沉积在直径为12.5厘米的硅片基板上。以涂布条件——提拉速度、溶液浓度和蒸发驱动力（ΔP）为函数，对整个晶圆上的干膜厚度和沉积膜的形态进行了表征。当不施加蒸发驱动力（ΔP = 0）时，在整个浓度范围（3-11 wt%）内可沉积出高度均匀的膜，厚度范围为8-105埃。在低浓度（3-5 wt%）和低蒸发驱动力（ΔP = 0.0138 MPa）下也可获得均匀的膜。然而，在中高浓度（7-11 wt%）下沉积的膜更厚（110-570埃）且均匀性较差，在较高的蒸发驱动力下不均匀性更大。使用光学显微镜和原子力显微镜（AFM）对膜形态进行表征，包括干燥缺陷和膜粗糙度。无蒸发情况下沉积的膜没有明显的干燥缺陷，均方根（RMS）粗糙度非常低（1.4-3.8埃）。在中等浓度（7 wt%）和低ΔP（0.0138-0.0276 MPa）下沉积的膜中观察到类旋节线脱湿形态，包括直径在100-300纳米范围内的孔洞和表面起伏。在较高浓度和较高蒸发驱动力下，类旋节线脱湿形态消失，但观察到直径在20-125微米范围内的同心环缺陷结构。将从l-CO2 hFMC沉积的SOA膜的膜厚度和形态与在常规浸涂条件下从甲苯和丙酮沉积的膜进行了比较。从l-CO2 hFMC沉积的膜更薄、更均匀，干燥缺陷更少，RMS粗糙度更低。