Simulation Of A Novel Structure Microwave Power SiGe HBT

We demonstrate a novel structure of microwave power SiGe HBTs, which reduces the total base-collector capacitance (Csc) by the way that the collector layers below the extrinsic base region are substituted with SiCh trenches. Methods to fabricate this new microwave power SiGe HBTs are explored and the key process to planar the silicon surface has been developed.The device was studied by using 2-D device simulation to investigate the characteristics of the novel structure SiGe HBT and pave the way for optimizing its microwave performance. Simulation results show that the total base-collector capacitance is reduced by the way that collector layers below the extrinsic base region are filled with SiGY Two collector structures were simulated, which were different in the width of the collector layers (O.Sjam for low power application and 4. 5um for high power application, VCE=4.5V and VcE=28V respectively). In a typical situation, the novel structure yields a power gain about 2dB higher than the conventional structure and an increase of 10-25% in the maximum oscillation frequency/max was observed from the numerical analysis.We also found that the novel structure has some negative influence for the high-voltage SiGe HBT. The threshold current density of Kirk effect and/T decreases while the trench depth is increasing. These effects have been investigated from a theoretical point of view and give a detail explain with Current Spreading effect.