The InGaAs planar detectors with SiNx film as diffusion mask were fabricated SiNx films were grown by plasma enhanced chemical vapor deposition(PECVD) or by low temperature ICP-CVD inductively coupled plasma chemical vapor deposition(ICPCVD). The photoelectric responses of the detectors made with the two methods were investigated. It turns out that the two kinds of devices have similar performance in the average response rate 0.73 and 0.78 A/W, the average peak detectivity 6.20E11 and 6.32E11 cmHz1/2W-1, and the quantum efficiency 56.0% and 62.0%, respectively. However， the average dark current densities of the detectors is much different, with the values of 312.9nA/cm2 and 206nA/cm2 (-0.1V), respectively. By fitting with experimental data to electrical transport theory, the mechanism of dark current was analyzed. The results indicate that the device using SiNx deposited by ICP-CVD has reduced ohmic dark current in comparison with devices with SiNx deposited by PECVD.