聚酰亚胺LB膜热解制备SiC薄膜的XPS研究

STUDY ON THE PROCESS OF PREPARING SiC FILM BY PYROLYSIS OF POLYIMIDE LB FILM

用XPS对沉积在硅基片上的聚酰亚胺LB膜以及由它真空热解制备的SiC薄膜进行了研究 ,并对其形成过程进行了跟踪分析 .XPS结果显示聚酰亚胺LB膜结构均匀 ,质量良好 ;真空热解时 ,约在 6 70℃时LB膜中的C与衬底Si反应形成SiC ;Ar离子溅射深度俄歇谱表明所制备的SiC膜中Si和C浓度成梯度分布 。

LB films of polyimide with promellitic dianhydride (PMDA) and 4,4′ diaminophenylether (ODA) structure were fabricated by so called “precursor” method,and SiC ultrathin films were obtained by pyrolyzing the polyimide LB films at a high vacuum of 1×10 -5 mbar and a temperature of 1000℃.In order to study the mechanism of this pyrolysis process,X ray photoelectron spectroscopy (XPS) technology was used to study the polyimide LB film and to trace the pyrolysis process of the LB film in situ. By probing the polyimide LB film from different angles,it was found that in the LB films,the elements were much evenly distributed,the quantitative analysis of the elements was also in very good agreement with the theoretical value.The in situ trace showed that at about 500 ℃ the molecules of polyimide decomposed to amorphous carbon; in the meantime,some small molecular weight gases were given out; the remained skeleton C in the LB film began to react with Si from substrate to form SiC at about 670 ℃.Higher temperature and longer time would be helpful for the reaction of SiC formation to proceed thoroughly.It also found that at lower temperature,the substrates were oxidized to SiO x ( x <2) by the oxygen it absorbed,but at higher temperature,the SiO x was reduced to SiC by the skeleton C in the LB films.Auger Electron Sputting (AES) spectrum indicated that the atoms of C and Si distributed gradiently in the SiC films,suggesting the mutually diffusion mechanism in the SiC formation.