Design And Analysis Of The Novel Partial SOI LIGBT

Lateral power devices are the core devices of Smart Power Integrated Circuits(SPIC)and High Voltage Integrated Circuits(HVIC).Lateral insulated gate bipolar transistors(LIGBT)have the advantages of strong conduction capability,high withstand voltage characteristics,and high integration.It is widely used in various electronic power systems and is a typical representative of power semiconductor devices.Although the LIGBT has a low forward voltage drop,the existence of a large number of unbalanced carriers in the drift region limits the switching speed and leads to a high turn-off loss.Therefore,the contradiction between the turn-off time and the forward voltage drop has been the core problem of horizontal IGBT devices.Shortening the turn-off time of the device and reducing the turn-off loss are always the main problems that researchers solve.By optimizing the electric field distribution of the device to increase the withstand voltage,the size of the device can be reduced,which helps to indirectly alleviate the contradiction between the off time and the forward voltage drop,such as field plate,RESURF,VLD technology,etc.,in which the electric field modulation technology changes The structural parameters of the device further modulate the surface electric field distribution in the drift region,and the surface electric field distribution of the device can be greatly optimized by the above-mentioned method.In this case,the related theory of electric field modulation technology has been innovatively proposed and widely used in LDMOS.It modulates and changes the electric field distribution on the surface of the drift region by changing the electric field distribution of the buried layer of the device,which greatly improves the performance of the characteristic parameters of the lateral power device.The research work of this paper mainly includes:Combining electric field modulation technology,PSOI structure temperature characteristics and RESURF technology,this paper designs and studies two LIGBT power devices with fast and low power consumption performance.The ISE-TCAD simulation software is used to establish the structural models of the two proposed devices,and the device performance is simulated and simulated by the control variable method.The proposed device has a P-type buried layer and a part of an SOI layer,and is called a BPSOI LIGBT.Due to the additional field modulation effect of the P-type buried layer and part of the SOI layer,two new peaks are generated on the surface electric field distribution of the device,which improves the valley bottom,reduces the peak value at both ends of the source and drain,and makes the surface electric field distribution more uniform,Can obtain smaller device size and higher breakdown voltage.The smaller device size has a shorter drift region length and stores fewer carriers,which is beneficial to the fast turn-off of the device.The simulation results show that under the same size condition(drift zone length L_D=15μm),the breakdown voltage of the proposed device is 26%higher than that of traditional SOI LIGBT and 84%higher than that of traditional SOI LIGBT.This is conducive to reducing the size of the device,thereby reducing the length of the drift region LD,so that the drift region can obtain fewer stored carriers.A smaller drift region length LD can quickly deplete the drift region and obtain a shorter depletion region length.The shorter the depletion region length,the smaller the number of stored carriers,which is more conducive to the turn-off of the device and can reduce the turn-off Time and turn-off loss.The turn-off time of the proposed device is 15.8ns,the turn-off time of SOI LIGBT is 37.5ns,and the turn-off time is greatly reduced.When the forward voltage drop is 2.05V,the turn-off time of the proposed device is 71%shorter than that of the traditional SOI LIGBT.Therefore,the proposed device has a better compromise between forward voltage drop and off-time than the traditional SOI LIGBT.In addition,the proposed device retains some of the characteristics of SOI LIGBT devices,which can effectively alleviate the self-heating effect of traditional SOI LIGBT.On the basis of previous research,APSOI LIGBT is proposed.The buried layer with a lower dielectric constant is used.As the ratio between the dielectric constant of the drift region Si and the buried layer is larger,the breakdown voltage of the buried layer here is greater,thus increasing the breakdown voltage of the device.Under the same thickness of the buried layer,the surface electric field under the buried layer here is close to four times that of the PSOI LIGBT.At the same time,using the different dielectric constants of different types of buried layers,the surface electric field will generate new electric field peaks at the junction of different buried layers to increase the vertical withstand voltage of the device and increase the breakdown voltage of the device.The existence of the silicon window makes it easier for the heat of the device to be introduced into the base area,alleviating the self-heating effect of the traditional SOI structure,and is beneficial to improving the working stability of the device.The turn-off time of APSOI LIGBT is 32ns,the turn-off time of BPSOI LIGBT is34.3ns,and the turn-off time is slightly improved.When V_F=1.23V,the Toff of this structure is 34%lower than that of the BPSOI LIGBT.This structure has a better compromise relationship between off-time and forward voltage drop,and lower power consumption.