Research Of High Voltage LDMOS Devices Based On The Technology Of Bulk Electric Field Modulation

The lateral double-diffusion metal oxide semiconductor(LDMOS)devices is widely used.The current flow of the LDMOS devices is in the surface,which makes it suit the CMOS process well.LDMOS devices have characteristics of high withstand voltage and low resistance which compare to the traditional IGBT.However,the contradiction between the breakdown voltage and the on-resistance in the conventional LDMOS devices is outstanding.Nowadays,the researchers and professors have proposed many kinds of methods to improve the situation,such as surface doping technology,lightly doped technology,field plate.Reducing the conflict between the withstand voltage and on-resistance is the main part to the LDMOS devices.Because the epitaxial layer and the substrate are the main parts to withstand the reversal voltage,three kinds of LDMOS structures are proposed in this paper,based on the Reduced Surface Field and the Reduced Bulk Field.The three proposed LDMOS structures are the multiple buried p-layers in the drift region,the p buried islands in the drift region and the N+ floating islands in the substrate.The multiple buried p-layers in the drift region: This structure buries p-layers into the drift region.The buried p-layers is not one block entirely.The p-layers have intervals between them and the length of each p-layer is different.The p-layers decrease successively in the way of arithmetic progression.This structure has two gates,which means it provides two ways for the drain current.What's more,the introduced p-layers assisted deplete the drift region in the epitaxial layer,which means increasing the concentration in the epitaxial layer.The buried p-layers form more PN junctions in the drift region,which modulate the distribution of the potential.So it makes the breakdown voltage enhanced and makes the diminution Ron,sp.The simulation analysis software is MEDICI.At the condition of the 16?m length of the drift region,the Ron,sp of the structure is reduced by 52.5% and the BV of the structure improved by 36.4% than the conventional devices.The p buried islands in the drift region:This structure buries p-type islands into the drift region.It has intervals between the two islands.What's more,the p-type islands buried into the drift region deeply.The p-type islands form more PN junctions in the drift region,which modulates the distribution of electric field.The p-type islands assisted deplete the drift region in the epitaxial layer.So the structure achieves a low Ron,sp.The simulation analysis software is MEDICI.At the condition of the 30?m length of the drift region,the Ron,sp of the structure is reduced by 53.7% and the BV of the structure improved by 24.7% than the conventional devices.The N+ floating islands in the substrate: this structure buries many of n-type islands into the substrate.It has intervals between the two islands.So the buried n-type islands form PN junctions in the substrate.The PN junctions help the substrate withstand the drain voltage.At the off state the islands induce the drain potential into the substrate,which modulates the distribution of electric field,then the structure achieves a higher withstand voltage.What's more,the effective of the assisted depletion of the n-type islands make a low Ron,sp.The simulation analysis software is MEDICI.At the condition of the 40?m length of the drift region,the Ron,sp of the structure is reduced by 19.7% and the BV of the structure improved by 74.6%.