Effects of Deposition Method of PECVD Silicon Nitride as MIM Capacitor Dielectric for GaAs HBT Technology

Thin silicon nitride (Si3N4) films deposited using plasma-enhanced chemical deposition (PECVD) method have been used as metalinsulator-metal (MIM) capacitor dielectric for GaAs heterojunction bipolar transistor (HBT) technology. The characteristics of the films, which were deposited at 300C, were found to be dependent on how the PECVD film was deposited. A silicon nitride film deposited as a multi-layer-layer film has different properties compared to a film deposited under the same processing conditions as a single layer film. When used as MIM capacitor dielectric, the multi-layer Si3N4 film is shown to have significantly superior and higher dielectric breakdown voltage and lower leakage current characteristics, as compared to the single layer film, while the capacitance density is found to be similar. Additionally, the multi-layer Si3N4 film is shown to have lower compressive stress and lower refractive index, indicating that the characteristics of the film are influenced by the additional interfaces present in a multi-layer film.