微波电子回旋共振等离子体化学气相淀积法制备非晶氟化碳薄膜的研究

采用电子回旋共振等离子体化学气相淀积(ECR-CVD)法，以C₄F₈和CH₄为源气体制备了非晶氟化碳(a-C：F)薄膜.X射线电子能谱(XPS)和傅里叶变换红外光谱(FTIR)分析表明，a-C：F薄膜退火后厚度减小是由于位于a-C：F薄膜交联结构末端的C—C和CF₃结合态的热稳定性较差，导致退火时容易生成气态挥发物造成的.a-C：F膜介电常数在300℃氮气气氛中退火后由于电子极化增大和薄膜密度增加而上升，界面态陷阱密度从(5—9)×10¹¹eV^-1·cm^-2降至(4—6)×10¹¹eV^-1·cm^-2.a-C：F薄膜导电行为在低场强区域呈现欧姆特性，在高场强区域符合 Poole-Frankel机理.非定域π电子在带尾形成陷阱且陷阱能量在退火后降低，从而使更多陷阱电子在场增强热激发作用下进入导带并引起电流增大. 关键词： a-C：F ECR-CVD 键结构 电学性质

Study of fluorinated amorphous carbon films prepared by electron cyclotron resonance chemical vapor deposition

Fluorinated amorphous carbon(a-C:F) films were deposited using C₄F₈ and CH₄ as precursor gases by electron cyclotron resonance chemical vapor deposition (ECR-CVD). Analysis of chemical compositions and bond structures by Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) shows that the loss of CF₃ and C—C termination bonds are liable for inducing reduction of film thickness after heat treatment through out-gassing process. The dielectric constant of a-C:F films increases due to increased electronic polarization and enhanced film density and the interface trap density decreases from (5—9)×10¹¹eV^-1cm^-2 to (4—6)×10¹¹eV^-1cm^-2 after 300℃ annealing in a nitrogen environment. The current-voltage characteristics of α-C:F films was explained by ohmic conduction at low fields and Poole-Frankel conduction at high electric fields. The trap energy of the traps at band tails formed by the delocalized π electrons decreases after annealing, leading to the increase of leakage current due to field-enhanced thermal excitation of trapped electrons into the conduction band.