Metal silicide/poly-Si Schottky diodes for uncooled microbolometers

Area of Science:

• Materials Science
• Semiconductor Physics
• Infrared Technology

Background:

• Monolithic uncooled microbolometer infrared focal plane arrays require efficient temperature sensing elements.
• Nickel silicide/polycrystalline silicon structures offer potential for integrated temperature sensing.

Purpose of the Study:

• To investigate nickel silicide/polycrystalline silicon films for use as temperature sensors.
• To characterize the structure, composition, and electrical properties of these diodes.

Main Methods:

• Transmission electron microscopy (TEM) for structural and compositional analysis.
• Electrical characterization of Schottky diodes, including rectification ratio and barrier height measurements.
• Photo-electromotive force (photo-EMF) spectroscopy to analyze interface properties.

Main Results:

• Nickel silicide formed is a multi-phase compound (Ni3Si, Ni2Si, NiSi, minor NiSi2).
• Schottky diodes exhibit temperature-dependent rectification ratios, decreasing from ~100 to ~20 (22–70°C) and exceeding 1,000 at 80 K.
• Barrier height of ~0.95 eV controls room temperature photovoltage; multiple barriers observed at 80 K.
• Temperature coefficients of voltage and current range from 0.3–0.6%/°C (forward bias) and ~2.5%/°C (reverse bias).

Conclusions:

• Nickel silicide Schottky diodes on polycrystalline silicon are suitable temperature sensors for infrared focal plane arrays.
• The multi-phase nature of nickel silicide and interface properties influence diode performance.
• The diodes demonstrate significant temperature sensitivity across a broad temperature range.