Electron cyclotron resonance deposition and plasma diagnostics of a-Si:H and a-C:H films

Abstract

Electron cyclotron resonance (ECR) microwave plasma enhanced deposition processes have been developed for depositing amorphous silicon (a-Si:H) and amorphous carbon (a-C:H) films. The ECR plasma is generated by a 2.45 GHz microwave power source and a resonant magnetic field in a cylindrical plasma chamber; the film is then deposited remotely using the extracted ECR plasma through a divergent magnetic field with or without radio frequency power bias. A high deposition rate of about 25 Å s−1 and a light-to-dark conductivity ratio of 1 × 105 for a-Si:H films have been obtained by the ECR process using a pure silane plasma. The methane and silane ECR plasmas used for a-C:H and a-Si:H film depositions are analyzed by optical emission spectroscopy (OES) of SiH∗, CH∗ and H∗ excited states. Steady-state OES studies have established a linear correlation between the SiH∗ emission intensity and the film deposition rate. This linear correlation suggests that SiH∗ species are related to the neutral radicals which are responsible for the a-Si:H film deposition. Hard and soft a-C:H films have been deposited by ECR with and without r.f. bias power, respectively. The ECR-deposited a-C:H films have been characterized by fluorescence, IR and Raman spectroscopy. The r.f. bias to the substrate is found to play a critical role in determing the film structure and the carbon bonding configuration of ECR-deposited a-C:H films.