The Development of Semi-Insulating Silicon Substrates for Microwave Devices

The concept of fully encapsulated, semi-insulating silicon (SI-Si) Czochralski silicon on insulator substrates for silicon microwave devices is presented. The experimental results show that, using gold as a compensating deep level impurity in silicon, a resistivity of 180 k cm is achieved in this work. Sufficiently high resistivity substrates for microwave applications are obtained by depositing gold on silicon and annealing for 1 h at 1000 degrees C. Silicon dioxide and silicon nitride are considered as diffusion barriers for use in the new technology. At 1000 degrees C, the diffusivity of gold in plasma-enhanced chemical vapor deposited silicon nitride is similar to 3.7x10(-13) cm(2) s(-1), whereas for silicon dioxide, it is less than 6x10(-14) cm(2) s(-1). These results imply that silicon nitride would be ineffective as a diffusion barrier in the SI-Si technology but that a 600 nm thick buried silicon dioxide might allow devices to be processed with a thermal budget of up to 15 h at 1000 degrees C without impurity contamination.