A PROCESS FOR FABRICATING LOW VOLTAGE/DEEP JUNCTION ZENERS AND RECTIFIERS
Original Publication Date: 1991-Apr-01
Included in the Prior Art Database: 2001-Nov-28
Two boron ion implantations into a heavily doped phosphorous substrate are used to obtain both a deep junction and an extremely steep junction gradient in addition to a very high boron surface concentration. The first ion implantation step together with the appropriate diffusion cycle sets the junction to approximately 75% of its final depth. The second ion implantation step combined with the appropriate diffusion cycle overlaps the first diffused profile and allows one to steepen the junction gradient in addition to enhancing the surface concentration. It was found that up to three times the historic junction depth was achieved while maintaining the required junction steepness. This technique is extremely valuable in reducing vulnerability to surface defects generated in fabrication.