Investigation of anode-side temperature effect in 1200V FWD cosmic ray failure

This paper presents a new cosmic ray failure mechanism of FWDs based on TCAD, and proposes novel FWDs with higher withstanding capability against cosmic rays, which induce device failure. The novel FWDs have a very thin additional P⁺ layers on the surface of the anode layer to prevent catastrophic temperature rise due to high energy ion irradiation. The high energy Si ions, which are generated by the neutron irradiation, induce high temperature rise in the anode surface. TCAD analysis shows that if the anode surface temperature becomes so high, large minority carrier generation in the surface causes electron current injection from the P⁺ surface, resulting in high temperature increase and the resultant silicon melting inside FWDs. In the novel FWDs, the temperature rise is suppressed by the additional P⁺ layer. Experimental verification was also executed to confirm the successful suppression of the device failure by neutron irradiation.