The correlation between the breakdown voltage of power devices passivated by semi-insulating polycrystalline silicon and the effective density of interface charges

摘要

Mesa-structured high-voltage diodes have been passivated by semi-insulating polycrystalline silicon (SIPOS) and silicon nitride thin films. An effective density of fixed interface charges was determined by applying high-frequency capacitance-voltage measurements to metal-SIPOS-silicon and metal-silicon-nitride-silicon capacitors. The reverse breakdown voltage and the density of fixed interface charges of SIPOS-silicon samples depend on the annealing temperature while the corresponding values of silicon-nitride-silicon samples could be varied by the ammonia-to-silane flow ratio of chemical vapor deposition. Using a Poisson solver, the breakdown voltage of the diodes is calculated in relation to the density of fixed interface charges assuming an isolating passivation layer. Experimental and theoretical values of the breakdown voltage in relation to the density of fixed interface charges agree very well for both SIPOS and silicon-nitride-passivated samples. These findings reveal the physical meaning of an effective density of interface charges determined in SIPOS-silicon samples by capacitance-voltage measurements.