Low-Stress Silicon Nitride LPCVD

Low stress nitride is performed at a high ratio of DCS to NH3 flow rates (typically ~ 6). The consequence of such silicon-enriched deposition is a very low tensile stress. The stress depends mainly on the gas mixing ratio and the process temperature. The processing pressure is typically a few Torr or lower. Increasing the pressure and the temperature increases the deposition but sacrifices the uniformity.

Applications: MEMS structures, diffusion barriers, passivation layers, oxidation masks, etch masks, ion implant masks, insulation, encapsulation, mechanical protection, gate dielectrics, optical waveguides, CMP and etch stop layers.

  • Typical film thickness: 0.1 - 2 µm
  • Refractive index at 550 nm / 2.0 - 2.3
  • Batch Size: 50
  • Deposition rate: 3 - 4.5 nm/min
  • Gases: dichlorosilane, ammonia
  • Uniformity: < 5%
  • Stress: 50 - 300 MPa
  • Deposition Temperature: 800 - 840 °C Flat

LPCVD Processes