The Research Of 4H-SiC Junction Barrier Schottky Diode

As the third generation semiuconductor material,silicon carbide(SiC)has excellent properties and can be used in high-voltage,high-frequency,high-temperature fields such as electric vehicles,motor drives,and defense industry.Silicon carbide power diodes are an indispensable power device with rectifying and unidirectional conduction functions in integrated circuits.SiC junction barrier schottky(JBS)diode is an important SiC power diode,and SiC JBS diode have been attracted wide attentions because of combining the advantages of schottky barrier diode(SBD)and PiN diode.In this paper,the new structure of SiC JBS diode is rationally designed by studying metal semiconductor contact theory,PiN structure theory,super junction(SJ)technology and channel structure theory.And a new 4H-SiC Separated Floating Trench and SJ(S-FT SJ)JBS diode is proposed.The 4H-SiC S-FT SJ JBS diode has a low specific on-resistance(Ron,sp)while having a high breakdown voltage(BV),and breaks the limit of the silicon carbide unipolar device.(1)The properties of silicon carbide materials,metal semiconductor contact theory,P-i-N structure theory,SJ and trench technology are studied.SiC JBS diode is based on the silicon carbide,and the structure is consist of the metal semiconductor contact with P-i-N structure.The use of SJ and trench technology in the silicon carbide junction barrier schottky diode can improve the performance of the device while ensuring the device with high breakdown voltage,it can also ensure the device has low specific on-resistance.(2)The new 4H-SiC S-FT SJ JBS diode is proposed.The first feature of the 4H-SiC S-FT SJ JBS diode is the introduction of a SJ structure into body of the device.The SJ can optimize the electric field distribution in the drift layer while increasing the concentration of the drift layer of the device,therefore,the SJ can simultaneously reduce the device specific on-resistance and improve the breakdown voltage of the device.The second feature is to introduce a floating oxide trench isolated from the P+strip in the body of the device,and the floating oxide trench can increase the contact area between the drift layer and the metal anode,that is to say,schottky barrier area is increased,which ultimately increases the current density of the device during forward conduction and reduces the specific on-resistance of the device.The oxide trench and the drift layer can constitute a metal-insulator-semiconductor(MIS)structure which can withstand a partial of voltage when the device is on the off state.Compared with the conventional structure,the breakdown voltage of 4H-SiC S-FT SJ JBS diode is increased by 29.6%,and the specific on-resistance is by 50%.(3)The process design flow of the proposed 4H-SiC S-FT SJ JBS diode is carried out under the condition of the existing process technology,and the process characteristics of silicon carbide oxidation,etching,ion implantation,schottky contact,and ohmic contact are analyzed.Finally,the layout of the 4H-SiC S-FT SJ JBS diode was designed according to the layout design rules.