Research On The Novel Device Structure Of SOI LDMOS Based On The Trench Technology

As the core device of SOI(Silicon O n Insulator)Power Integrated C ircuit(PIC),SOI LDMOS(Lateral Double-diffused MOSFET)is widely used in the fields of aerospace,wireless communication,automotive electronics because of the advantages,such as low power dissipation,easily integrated and high speed.Enhancing the breakdown voltage and reducing the specific on resistance are the two important aspects in the power device design.For the conventional SOI LDMOS,when the breakdown voltage is enhanced,the specific on resistance is increased simultaneously.To relax the contradiction between the breakdown voltage and the specific on resistance,SOI LDMOS device structure based on trench technology is researched in detail.The breakdown characteristic and specific on-resistance characteristic of trench gate SOI and trench drain SOI are investigated in detail,then three novel device structures based on the trench technology are proposed,which include a trench gate and trench drain SOI LDMOS with vertical drain field plate,a dual trench SOI LDMOS with L shaped source field plate,a trench gate and trench source SOI LDMOS,a trench gate and trench source SOI LDMOS with vertical gate field plate.Two-dimensional simulation results show that the three novel device structures can relax the contradiction between the breakdown voltage and the specific on resistance.The innovations of this thesis are as follows:1.A SOI LDMOS with a vertical drain field plate and trench gate and trench drain is proposed,which lowers the on-resistance.A vertical field plate is used,which modulates and reduces the high electric field at the end of the drain electrode and increases the breakdown voltage.Compared with the conventional SOI LDMOS,the breakdown voltage is improved by 4% and the specific on-resistance is reduced by 53%.2.A dual trench SOI high voltage device with an L shaped source field plate is proposed.The SiO2 dielectric layer in the drift region can holds high electric field,which makes the breakdown voltage greatly increased.An L shaped source field plate reduces the specific on resistance.Compared with the conventional SOI LDMOS with the same size,the breakdown voltage is improved by 151% and the specific on-resistance is reduced by 20%.The on resistance is reduced by 80% Compared with the conventional SOI LDMOS at the same breakdown voltage.3.A SOI LDMOS with a vertical gate field plate and trench gate and trench source is proposed.The structure of trench gate and trench source widens the vertical current conduction area,which reduces the specific on-resistance.The thicker oxide layer on the right of the vertical gate field plate makes the breakdown voltage higher.Compared with the conventional SOI LDMOS,the breakdown voltage and specific on-resistance are improved by 33% and reduced by 33% respectively.