Research On Irradiation Charge Modulation Mechanism And Radiation Hardening Strategy Of SOI LDMOS Devices

High voltage integrated circuit is designed to realize power control and conversion.It has important applications in aerospace power system and servo actuation system.Lateral Double-diffused MOS（LDMOS）is the core device for realizing power conversion in high voltage IC.Compared with low-voltage MOS devices,their oxidation layer is thick,with large area and high working electric field,resulting in more serious damage of Total Ionizing Dose（TID）and Single Event Effects（SEE）and more complex mechanism.Aiming at SOI-based high-voltage LDMOS devices,this thesis studies the radiation damage mechanism and radiation hardening technology around the radiation effects of TID and SEE,and carries out radiation hardening verification through experiments.The main work contents are as follows:（1）The concept of irradiation charge field(E_rc)is put forward and the different breakdown voltage shift trends of TID-induced devices are attributed to the modulation of the initial electric field by irradiation charge field.E_rc will increase the electric field of the buried oxygen layer,resulting in increased vertical breakdown voltage.E_rc will increase the surface source side electric field and decrease the drain side electric field,resulting in the lateral breakdown voltage will be monotonically decreased and first increased and then decreased.The shift trend of TID induced breakdown voltage depends on the shift trend of lower lateral breakdown voltage and vertical breakdown voltage.Based on this mechanism,the irradiation charge field inverse modulation hardening technique is proposed.Through the design of the drift region which withstand high voltage,the initial non-uniform electric field distribution of source side low drain side high type is constructed,and the traditional monotone reduction relationship between BV and radiation is changed into non-monotone reduction relationship,so as to improve the total dose radiation tolerance and realize radiation resistance reinforcement.（2）The 80V radiation-hardened SOI LDMOS device is studied based on the irradiation charge field inverse modulation hardening technology.First of all,carry out the normal characteristics design of the device,optimize the structure of drift area,field plate,n-well,etc.,to meet the requirements of normal characteristics index.Secondly,the mechanism and hardening strategy of TID effect were studied to reveal the change rule of electric field distribution and characteristic degradation mechanism under different interfacial charge field modulation,and the initial surface electric field with non-uniform distribution in the drift region was constructed by reducing the concentration of drift region and increasing field plate length and other hardening methods,so as to improve the TID tolerance of the device.Then,the SEE effect study was carried out to analyze the changing law of electric field and carrier behavior at each stage,and to reveal the single event burnout mechanism of SOI high voltage LDMOS devices.Moreover,the device’s resistance to single event burnout was improved by extending the length of n-well and cross-arranged source pole design and other hardening methods.Based on the above work,the 80V radiation-hardened SOI LDMOS device was fabricated in the cooperative agency.Test results show that BV=123 V,V_th=1.3 V.The results of total dose radiation experiment show that the relationship between breakdown voltage and radiation dose of the device has achieved non-monotonic reduction.At 200krad（Si）,the device withstands 122 V and 106 V respectively under the radiation bias in OFF and ON states,meeting the requirements of project targets.