Study On The Design Of High Performance RF Semiconductor Power Devices And Their Reliability

RF power amplifier device is the core component of the wireless base station,which amplifies RF signal to make a good wireless coverage.Nowadays,human is faced with environmental crisis and energy challenge,so,it is an urgent task to reduce the energy consumption of daily operations in the base station.Some main base station suppliers have developed and provided a high efficient green base station.Therefore,it is very improtant to systematically study the high performance power amplifier based on GaAs HBT?LDMOS and GaN technology.The main academic contributions of this dissertation are as follows:(1)Performance degradation and breakdown events of several PA dies are measured for different ESD voltages described by the human body model(HBM),with different TFRs chosen for both DCS and GSM bands,respectively.An economic way is proposed and validated for effectively suppressing the ESD impact on the on-chip GaAs HBT PA by introducing some appropriate TFRs at its input port.(2)Temperature distribution over the PA die is obtained using Finite Element Method(FEM)algorithm and a thermal Infrared Scanner(IR),respectively.Further,an improved design for the GaAs HBT PA chip is performed,fabricated and tested,with its PVT variation suppressed effectively.(3)The breakdown effect of power amplifier based on LDMOSFET in high power microwave pulse is designed and simulated,and the key parameters affecting the reliability of power amplifier are analyzed.A test experiment is set up to determine if the thermal reliability of bonding wires or die breakdown issues happened after ruggedness testing.The temperature distribution of LDMOSFET die surface and bonding wires array are also captured by a thermal infrared scanner.It is found that the temperature distribution is intimately related with the profiles of the bonding wires array.Finally,an improved LDMOS design in optimizing the bonding wires profile is proposed.(4)RF performance of PA will change under the shielding cover.Both S-parameters and input-output responses of the PA sample for different heights(H)and widths(W)of the shielding covers are measured using one Automation Testing Bench.A calibrated factor for the input bonding wires and the concept of loop loss are introduced into one new circuit model so as to achieve good correlation of the structure.It is further found that,even the cover height is reduced,the S-parameters of PA can be effectively improved through optimization of its internal impedance matching networks consisting of multiple bonding wires.Some key technical issues are addressed for improving electromagnetic compatibility(EMC)design of metallic shielding cavity for achieving better RF performance of LDMOSFET-based power amplifier(PA)in PCB.An interactive influence between the PA and PCB is studied in detail.The most sensitive feedback path of electromagnetic interference(EMI)inside the shielding cavity is characterized and a metallic isolation wall is introduced between the input(gate)and output(drain)of the LDMOSFET die for suppressing inner coupling effects.This research should be useful for the development of compact PA modules with our desired EMC performance.(5)The basic theory of wideband feedback amplifier is investigated in this paper.A broadband single stage AlGaN/GaN HEMT amplifier has been designed with 10 dB gain over the frequency range from 100 MHz to 3.5GHz.A new method of using negative feedback is used to get so broadband performance.A tradeoff between input VSWR and gain flatness has been made to get best RF performance which reflect the advantage of AlGaN/GaN technology.And then,a high efficient AlGaN/GaN HEMT power amplifier using inverse class F method is designed because of the small output capacitance of AlGaN/GaN.It is proved that the design is good enough when compared with the simulation and measurement.The output power is higher than 10 W within 74% efficiency,and gain is a about 20 dB within 0.6dB flatness.(6)Finally,the effect of AlGaN/GaN devices after injecting high power microwave pulse is investigated.The breakdown characterisitic is measured under different pulse width.And finally scanning electron microscope(SEM)cross-section images and spectrum analysis are made.The damage position of the chip are precisely displayed,which provides guidance for further strengthening electromagnetic protection design.For the researches listed above,some design using LDMOS,GaAs HBT,and AlGaN/GaN are taped out,designed and fabricated.The validity and efficiency of our investigations have been demonstrated by the good agreements among the measured,simulated and modeled results.