Growth and quality control of MBE SiGe-HBT structures for analog IC applications

MBE-based SiGe/Si heterostructures prepared by molecular beam epitaxy (MBE) are described in this study with an aim at manufacturing SiGe heterojunction bipolar transistors (HBTs) for the applications in analog ICs. Based on the simulations made by Medici, MBE-based SiGe/Si heterostructures have been designed and grown. The quality of the MBE layered heterostructures has been characterized by reflection high-energy electron diffraction, X-ray diffraction, secondary ion mass spectrometry and spreading resistance. Furthermore, SiGe-HBTs have been fabricated using the 3 μm process technology. The experimental results indicate that both the direct current (DC) characteristics and the cutoff frequency of SiGe HBTs are satisfactory. The current gain β of HBT devices is 50, when the collector voltage V_C=2 V and the collector current I_C=5 mA. The cutoff frequency f _T=5.1 GHz. And the uniformity of the cutoff frequency of HBT is quite good. The Gummel plot of an MBE-grown SiGe HBT with the common-emitter configuration shows the excellent performance