Lateral NPN Protect Device
Original Publication Date: 1980-Jul-01
Included in the Prior Art Database: 2005-Feb-13
Consider the vertical structure of the thick oxide lateral NPN protect device shown in Fig. 1. It is known that surface fields and junction curvatures affect the avalanche breakdown of planar diodes. When surface fields are in the same direction as the reverse biased breakdown fields near the junction, the breakdown voltage decreases. Furthermore, when the junction curvature decreases, the breakdown voltage likewise decreases. The reasons are that the surface fields while in the right direction assist the reverse biased fields in reaching the critical field for avalanche breakdown and that small junction curvatures enhance the local reverse biased fields.