Thermal conductivity of heavily doped low-pressure chemical vapor deposited polycrystalline silicon films

Abstract

The lateral thermal conductivity of heavily doped low‐pressure chemical vapor deposited polycrystalline silicon films is measured using polycrystalline silicon microbridges elevated three micrometers above a silicon substrate. The bridges, lightly doped in their central regions and heavily doped elsewhere, are fabricated using a sacrificial silicon‐dioxide layer and phosphorus out‐diffusion from doped oxide. Voltage‐current characteristics measured on the bridges both under high vacuum and in silicone oil are used to calculate lateral thermal conductivity in the polycrystalline silicon. The experimental values for the thermal conductivity of heavily doped polycrystalline silicon range from 0.29 to 0.34 W cm⁻¹ K⁻¹ and average 0.32 W cm⁻¹ K⁻¹. These values agree closely with results obtained by a second method that employs uniformly doped polycrystalline silicon bridges. In the second method, high‐vacuum, voltage‐current characteristics are measured and the indicated thermal conductivities for two samples are 0.29 and 0.30 W cm⁻¹ K⁻¹, respectively.