HgCdTe MWIR PECVD SiN passivated photodiodes

To determine a suitable passivation and insulation layer for HgCdTe photodiodes, the properties of various low temperature plasma-enhanced chemical vapour deposition (PECVD) SiN films were investigated. Metal-insulator-metal (MIM) capacitors were fabricated on silicon to determine a suitable PECVD SiN film for insulation of HgCdTe diodes. It was found that PECVD process temperature of 125degC, at high power, and low process pressure gave the best film characteristics. These films were stable in atmosphere, as shown by FTIR measurements, which also shows oxidation of low power, high process pressure films. HgCdTe photodiodes were fabricated with PECVD SiN films with 200 W RF power, 300 mTorr pressure, and a SiN₄:NH₃:N₂ 5:45:100 gas ratio. Gated diode measurements indicated that R₀A values of 3.0times10⁶ Omega cm² are achievable with fine-tuning of the SiN charge.