The spatial distribution of the ECR plasma density has been measured by usi
ng an eccentric Langmuir probe. The result indicates that the plasma densit
y is very uniform in the axis Z = 50 cm and radial phi = 12 cm. Effect of t
he radial uniformity of plasma density on the uniformity of deposition rate
and thin film thickness is analyzed. The repeatability to prepare silicon
nitride thin film of a specified thickness is discussed. The relation of th
e deposition process with the deposition rate of silicon nitride thin film
is investigated and the dependence of the practical application on process
parameters has been obtained for the deposition thin film with ECR-PECVD te
chnology.