不同CHF_3/CH_4流量比下沉积a-C∶F∶H薄膜键结构的红外分析

INFRARED ANALYSIS OF BOND CONFIGURATION FOR THE a-C∶F∶H FILMS DEPOSITED AT VARIABLE CHF_3/CH_4 FLOW RATIOS

通过微波电子回旋共振等离子体化学气相沉积方法使用CH4 CHF3源气体制备a C∶F∶H薄膜 .红外结果表明 ,a C∶F∶H薄膜随着流量比R =[CHF3] [CHF3]+[CH4])的变化存在结构上的演变 ,R <6 4%时 ,薄膜主要是以类金刚石 (DLC)特征的结构为主 ;当R >6 4%时 ,薄膜表现为一个类聚四氟乙烯 (PTFE)的结构 ,结构单体主要为 CF2 .同时这种结构上的变化影响着薄膜的光学带隙 .在类DLC特征结构区 ,Eg 随着流量比的增加而下降 ,而在类PTFE区 ,Eg 则随着流量比的上升而上升 .a C∶F∶H薄膜在R >92 %时透射率接近 10 0 %

a-C:F:H films are prepared by microwave ECR plasma-enhanced chemical vapor deposition method at variable CHF3/CH4 gas flow raitos. The results from the Fourier transform-infra-red absorption for these films have shown that a structural evolution of the a-C: F: H film occurs at variable flow ratios R = [CHF3]/([CHF3] + [CH4]). The main structure of the films is diamond like carbon (DLC) characteristics for R less than 64%. The film presents a structure of PTFE-like as R is larger than 64%, where the dominant structural monomer is -CF2. Meanwhile, this structural evolution has also an influence on optical gap of the films. Optical gap decreases with the increase of flow ratios in the region of DLC-like characteristics I while increasing in the PTFE-like region. The transmittance of the a-C: F:H film is close to 100% for R larger than 92%.