Research On Characteristics Of SOI LDMOS With Multi-Finger High-K Dielectric

Silicon on insulator lateral double diffusion metal oxide semiconductor（SOI LDMOS）is widely used due to its good compatibility with CMOS process,high voltage withstanding capability and low parasitic capacitance.How to improve the device performance of SOI LDMOS with higher breakdown voltage（BV）and lower specific on-resistance(R_on,sp)is one of the goals that designers have been pursuing.For this issue,a novel SOI LDMOS with multi-finger high-K dielectric is proposed.The multi-finger high-K dielectrics in the drift region have the modulation effect on the electric field,which improves the distribution of the surface electric field and the doping concentration in the drift region to enhance the device performance.It is able to balance the contradictory relationship between R_on,sp and BV very well.This thesis focuses on the new device mechanism,optimization of device structure parameters and device fabrication process.The main work includes:（1）An equal-finger high-K dielectrics LDMOS（EFHK-LDMOS）is investigated.The main structural feature is the introduction of partical high-K dielectrics in the drift region of the device,forming a structure with alternating distribution of high-K dielectrics and silicon region in the drift region near the P-well.The equal-finger high-K dielectrics are arranged in equal lengths with one end extending into the P-well region and the other end locating in the drift region at a certain distance from the drain.The proposed device structure not only modulates the electric field distribution on the surface to improve breakdown voltage,but also increases the drift doping concentration to reduce the specific on-resistance,resulting in a significantly improved device performance.The optimised EFHK-LDMOS has a 48.5%increase in breakdown voltage,an 18.9%reduction in specific on-resistance and a 172%increase in FOM when compared to conventional LDMOS.（2）A multi-finger high-K dielectrics LDMOS（MFHK-LDMOS）is proposed.The main structural innovation feature is the introduction of multi-finger high-K dielectrics with different lengths in the drift region,which are designed according to specific design rules.The lengths and widths of the multi-finger high-K dielectrics are simulated and optimised.The adjacent multi-finger high-K dielectrics of different lengths in the proposed novel MFHK-LDMOS enable the introduction of multiple electric field peaks at finger tips in the drift region to modulate the surface electric field.Moreover,the varying length of the multi-finger high-K dielectrics prevents the electric field accumulation,avoiding premature breakdown at that location and increasing the device breakdown voltage.Simulation results show that the optimised MFHK-LDMOS is able to achieve a breakdown voltage of 403.8V,a lower specific on-resistance of 18.7mΩ·cm² and a higher FOM of 8.72MW/cm².The breakdown voltage is improved by 59.2%,the specific on-resistance is redused by 37.8%and the FOM is increased by more than three times compared to the conventional LDMOS.The proposed MFHK-LDMOS shows the good balance of the conflicting relationship between R_on,sp and BV.（3）The process scheme for the new structure of multi-finger high-K dielectrics LDMOS is designed.The process simulation is carried out by the Process tool in Sentaurus.The structural and process parameters of the device are simulated and optimised to verify the feasibility of the process scheme and process parameters.