Research On Characteristics And Mechanism Of A Novel SiGe HBT Device With Field Plate Structure

The advantages of high frequency,high gain,and low noise are provided by the SiGe HBT.Its low cost and compatibility with the silicon process make it widely used in RF circuits.This paper presents a new type of SiGe HBT device with field plate structure in the collector region.When the new structure SiGe HBT operates,based on the field plate potential,there are three modes of operation:a collector operation mode,a base operation mode,and an emitter operation mode.Multiple operating modes provide versatility for flexible device applications.Firstly,the current transport mechanism of SiGe HBT devices with novel collector field plate structures is studied.With the introduction of the field plate structure,the distribution of the electric field is improved in the collector region,the composite electron current decreases in the base region,the electron current injected from the emitter region into the collector region increases,and the collector current increases.The emitter delay time decreases with the increasing of collector current.Based on the decreasing of the carrier transit time,the frequency characteristics of the device is improved.Secondly,the characteristics of the SiGe HBT device with field plate structure is studied.The DC characteristics and frequency characteristics of the new structure are compared and analyzed.The results show that under the collector operation mode,the current gain of the device reaches 193,compared to a conventional SiGe HBT structure,the current gain is increased by approximately 22%.Under the base operation mode,the device's characteristic frequency and the maximum oscillation frequency are 72Ghz and 81Ghz,increased by 24%and 4%respectively.In the emitter operation mode,the current gain and frequency characteristics of the device are not significantly improved.Once again,the SiGe HBT device with field plate structure is optimized.The different operation modes of the device are studied,the size of the field board is changed in different operation modes.In the collector operation mode,the current gain and the characteristic frequency increase with the increase of the width and length of the field plate.But the maximum oscillation frequency of the device decreases due to the presence of parasitic capacitance.Under the base operation mode,the current gain,characteristic frequency and the maximum oscillation frequency increases with the increase of the width and length of the field plate.In the base operation mode,the size of the field plate is designed to be as large as the process allows.Finally,the electrical properties of multi-finger emitter SiGe HBT structure is analyzed.The multi-finger emitter SiGe HBT is advantageous in suppressing the emitter current edging effect,and the current gain of the device is improved.With a four-finger emitter,the current gain of device is 252.Compared to a conventional SiGe HBT structure,the current gain is increased by approximately 19%.