The microwave power coupling and the power absorption by eletron in ECR system are discussed here. It is discovered that the distribution of static magnetic field in ECR resonance cave

the total pressure and the microwave power are the decisive factors for providing high energy electrons. These conditions decide the range of parameters in ECRCVD thin film deposition processes. The practical deposition research of SiN thin film by ECRCVD has been made. The experimental results are consistent with the numerical calculation.