Investigation Of Carbon Nitride Thin Film By DBD-PECVD

CN film is a new element film which has many good properties, such as high hardness, wide optical band gap, anti-oxidation at high temperature and anti erosion, and so on. It has been widely applied to micro-electron semiconductor, super-large scale integration and computer industry. In this paper, carbon nitride films on silicon substrate have been explored experimentally by DBD-PECVD plasmas, the relation between different deposition parameter and the structure properties of CN compound films are analyzed; the deposition mechanism of the CN films is studied.The carbon nitride films grow on the silicon are synthesized from CH₄/N₂, C₂H₂/N₂,and C₂H₄/N₂ gas mixtures using DBD-PECVD plasmas through changing the experiment conditions, such as the gas volume composition, deposition pressure, and the discharging frequency. The structure and properties of CN films are measured by FTIR, Raman,AFM and XPS, and the free radical is measured by OES.The results show that the processing parameters are very important effects on the films chemical structure, mechanical. The FTIR of film demonstrates the formation of covalent bonds between carbon and nitrogen atoms. Raman spectrum of film shows the films have carbon like structure and the result of AFM indicates the roughness of the film increases with decreasing N₂ volume fraction or increasing deposition pressure. XPS shows the chemical position of elements in CN film. The sp³C/ sp²C is decreasing and the content of sp³C and sp²C are increasing in CH₄/N₂ system and C₂H₄/N₂ system when the N₂ volume fraction decreases from 80% to 30%; The process of CN films deposition is diagnosed in situ through the optical emission spectra technique the effects of experimental parameters on the concentration of the precursors and the gas-phase reactions in the plasma have been obtained. Among the three gas mixtures, the film deposition rate in CH₄/N₂ gas mixtures is the lowest while that in C₂H₂/N₂ mixtures is the largest. As to the roughness of the films, the one deposited in CH₄/N₂ gas mixtures is much smoother than that in C₂H₂/N₂ and C₂H₄/N₂ mixtures, respectively. C atoms exist as C=C bond, CN double bond and CN triple bond and the N-H bond shows the existence of hydride in the film. The increase of N₂ volume fraction or deposition pressure could increase the collision probability and obtain C-N bonds.