ESD clamp with auto biasing under high injection conditions

Abstract

In a dual direction ESD protection circuit formed from multiple base-emitter fingers that include a SiGe base region, and a common sub-collector region, the I-V characteristics are adjusted by including P+ regions to define SCR structures that are operable to sink positive and negative ESD pulses, and adjusting the layout and distances between regions and the number of regions.

1 . A dual direction ESD protection circuit, comprising
 multiple base-emitter regions with a shared sub-collector defining a multi-finger NPN, and   multiple P+ diffusion regions, at least one of the P+ diffusion regions being connected to one or more base-emitter regions and to a pad, and at least one other of the P+ diffusion regions being connected to one or more other base-emitter regions and to ground, the bases of the base-emitter regions including selective base epitaxial regions.   
     
     
         2 . A dual direction ESD protection circuit of  claim 1 , wherein the P+ diffusion regions comprise P+ diffusion fingers or P+ diffusion rings. 
     
     
         3 . A dual direction ESD protection circuit of  claim 1 , wherein the selective base epitaxial regions comprise SiGe base epi regions. 
     
     
         4 . A dual direction ESD protection circuit of  claim 1 , wherein the base-emitter regions connected to the pad each comprise an emitter connected directly to the pad and a base connected to the pad via a resistor. 
     
     
         5 . A dual direction ESD protection circuit of  claim 1 , wherein the base-emitter regions connected to ground each comprise an emitter connected directly to ground and a base connected to ground via a resistor. 
     
     
         6 . A direction ESD protection circuit, comprising
 at least one first NPN BJT,   at least one second NPN BJT, wherein the NPN BJTs share a common collector region and each have a base and an emitter, wherein each base includes a selective base epitaxial region, the circuit further comprising   at least one first P+ diffusion region connected to the base and emitter of the at least one first NPN BJT, and   at least on second P+ diffusion region connected to the base and emitter region of the at least one second NPN BJT.   
     
     
         7 . A dual direction ESD protection circuit of  claim 6 , wherein the P+ diffusion regions comprise P+ diffusion fingers or P+ diffusion rings. 
     
     
         8 . A dual direction ESD protection circuit of  claim 6 , wherein the selective base epitaxial region comprises a SiGe base epi. 
     
     
         9 . A dual direction ESD protection circuit of  claim 6 , wherein the emitter and base of the at least one first NPN BJT are connected to a high voltage rail, and the emitter and base of the at least one second NPN BJT are connected to ground. 
     
     
         10 . A dual direction ESD protection circuit of  claim 9 , wherein the base of the at least one first NPN BJT is connected to the high voltage rail via a first resistor, and the base of the at least one second NPN BJT is connected to ground via a second resistor. 
     
     
         11 . A dual direction ESD protection circuit of  claim 6 , wherein the at least one first P+ diffusion region is formed in an N-type region to define a first diode, and the at least one second P+ diffusion region is formed in an N-type region to define a second diode. 
     
     
         12 . A dual direction ESD protection circuit of  claim 11 , wherein the N-type regions comprise a shared N-epitaxial region. 
     
     
         13 . A method of controlling the current-voltage curve of a dual direction protection circuit that includes multiple bases with selective base epitaxial regions, multiple emitters, and a shared collector defining a multi-finger NPN, and further including multiple P+ diffusion regions, at least one of the P+ diffusion regions being connected to one or more bases and emitters and to a pad, and at least one other of the P+ diffusion regions being connected to one or more other bases and emitters and to ground, the method comprising
 adjusting at least one of, the number of P+ diffusion regions connected to the one or more bases and emitters and to the pad, the number of P+ diffusion regions connected to the one or more bases and emitters and to ground, the number of bases and emitters connected to the pad, the number of bases and emitters connected to ground, and the distance between one or more of the P+ regions and one or more of the emitters.   
     
     
         14 . A method of  claim 13 , wherein the bases and emitters connected to the pad comprise an emitter connected directly to the pad and a base connected to the pad via at least one first resistor, and the bases and emitters connected to ground comprise an emitter connected directly to ground and a base connected to ground via at least one second resistor, the method comprising adjusting at least one of, at least one first resistor value, and at least one second resistor value. 
     
     
         15 . A method of  claim 14 , wherein the selective base epitaxial region comprises a SiGe base epitaxial region.