THERMAL CONDUCTIVITY OF DOPED POLYSILICON LAYERS

Abstract

Polycrystalline silicon is common in microdevices for which thermal design is important. This study measures the lateral thermal conductivity of a boron-doped polysilicon layer at temperatures ranging from 20 to 320 K. The polysilicon layer is 1 µm thick with a doping concentration of l×lO¹⁹ cm^-3, and the measurements are performed using electrical-resistance thermometry in a suspended membrane structure. The room temperature thermal conductivity of the doped polysilicon layer is 45.3 W/m K, which is nearly an order of magnitude lower than that for a single-crystal silicon layer with the same dopant concentration. Phonon transport modeling and AFM grain size measurements suggest that annealing in this sample strongly reduces the importance of grain-boundary scattering.