Impact of the collector region fabrication on electrical characteristics of HCBT structures in 180 nm BiCMOS technology

Methods for the extrinsic collector fabrication of the Horizontal Current Bipolar transistor (HCBT) in 180 nm BiCMOS technology are presented. Electrical characteristics of the structure with implanted extrinsic collector and the structure which uses heavily doped n+ polysilicon for the extrinsic collector region are compared. Inferior RF performance of the HCBT with n+ poly extrinsic collector is attributed to increased collector series resistance. Both structures are analyzed by 2D process and device simulations. It is shown that increased collector resistance is associated eather with an interfacial layer between silicon n-hill and extrinsic collector polysilicon or collector contact resistance rather then with the collector polysilicon thickness.