Title :
Base thickness and high-frequency performance of SiGe HBT´s
Author :
Gruhle, A. ; Erben, U. ; Kasper, Erich
fDate :
11/1/1993 12:00:00 AM
Abstract :
Summary form only given. The influence of the base thickness on the high-frequency performance of about 20 fabricated HBTs (heterojunction bipolar transistors) has been analyzed by plotting the highest obtained fT value against base thickness. Base thickness is defined as the distance between the two Si/SiGe interfaces which usually coincide with the metallurgical pn-junctions. A steady increase of fT with decreasing base thickness can be clearly seen: starting from the first published HBTs with 50 nm base thickness which did not exceed 20 GHz, transistors with 40 nm base had 37-52 GHz and devices with 28-30 nm bases exhibited 58-91 GHz. The latest two samples had only 25 and 22 nm base thicknesses, leading to an fT of 95 GHz (fmax=50 GHz), the highest value reported for Si transistors. The base doping in the latter sample was 8×1019 cm-3 to maintain a base sheet resistance of about 1.2 kΩ
Keywords :
Ge-Si alloys; heterojunction bipolar transistors; semiconductor device testing; semiconductor materials; solid-state microwave devices; 1.2 kohm; 20 to 95 GHz; 22 to 50 nm; HBTs; Si-SiGe interface; base doping; base sheet resistance; base thickness; heterojunction bipolar transistors; high-frequency performance; metallurgical pn-junctions; Annealing; Bridges; Cutoff frequency; Doping; Electron devices; Fabrication; Germanium silicon alloys; Heterojunction bipolar transistors; Semiconductor films; Silicon germanium;
Journal_Title :
Electron Devices, IEEE Transactions on