Metal silicide/poly-Si Schottky diodes for uncooled microbolometers

TL;DR

This paper investigates nickel silicide/polycrystalline silicon Schottky diodes as temperature sensors for uncooled microbolometer IR focal plane arrays, analyzing their structure, composition, and electrical properties at various temperatures.

Contribution

It presents a low-temperature synthesis method for nickel silicide/poly-Si films and characterizes their structural and electrical properties for IR sensor applications.

Findings

Rectification ratios vary from ~100 to ~20 between 22°C and 70°C

Diodes exceed a rectification ratio of 1000 at 80K

Temperature coefficients of voltage and current are 0.3-0.6%/K and ~2.5%/K respectively

Abstract

Nickel silicide Schottky diodes formed on polycrystalline Si<P> films are proposed as temperature sensors of monolithic uncooled microbolometer IR focal plane arrays. Structure and composition of nickel silicide/polycrystalline silicon films synthesized in a low-temperature process are examined by means of transmission electron microscopy. The Ni silicide is identified as multi-phase compound composed by 20 to 40% of Ni3Si, 30 to 60% of Ni2Si and 10 to 30% of NiSi with probable minor content of NiSi2 at the silicide/poly-Si interface. Rectification ratios of the Schottky diodes vary from ~100 to ~20 for the temperature increasing from 22 to 70C; they exceed 1000 at 80K. A barrier of ~0.95 eV is found to control the photovoltage spectra at room temperature. A set of barriers is observed in photo-emf spectra at 80K and attributed to the Ni-silicide/poly-Si interface. Absolute values of temperature coefficients of voltage and current are found to vary from 0.3 to 0.6%/K for forward biasing and around 2.5%/K for reverse biasing of the diodes.