Analytical modeling and numerical simulations of the thermal behavior of trench-isolated bipolar transistors on SOI substrates

The thermal behavior of trench-isolated structures on SOI (silicon-on-insulator) substrates is analyzed. Detailed 3-D numerical simulations have been performed to investigate the impact of all technological and material parameters of interest. A novel analytical model for the temperature field is proposed, which is based on the reduction of the domain under analysis to a silicon rectangular parallelepiped with convective boundary conditions at lateral and bottom faces. An extensive comparison with numerical results proves that the model is extremely accurate in the overall parameter range, and can be adopted for a fast evaluation of the thermal resistance of a trench SOI device as well as of the temperature gradients within the silicon island surrounded by trenches and buried oxide.