System and method for increasing breakdown voltage of locos isolated devices

Abstract

An efficient method is disclosed for increasing the breakdown voltage of an integrated circuit device that is isolated by a local oxidation of silicon (LOCOS) process. The method comprises forming a portion of a field oxide in an integrated circuit so that the field oxide has a gradual profile. The gradual profile of the field oxide reduces impact ionization in the field oxide by creating a reduced value of electric field for a given value of applied voltage. The reduction in impact ionization increases the breakdown voltage of the integrated circuit. The gradual profile is formed by using an increased thickness of pad oxide and a reduced thickness of silicon nitride during a field oxide oxidation process.

1 . A method for increasing a breakdown voltage in an integrated circuit, said method comprising the steps of:
 forming a portion of a field oxide in said integrated circuit so that said portion of said field oxide has a gradual profile; and   using said gradual profile of said portion of said field oxide to reduce impact ionization in said portion of field oxide to increase said breakdown voltage of said integrated circuit   
     
     
         2 - 20 . (canceled)