SCR cell for electrical overstress protection of electronic circuits

An input protection device for protecting a circuit structure which is coupled to a first node, said device comprising:

• a first lightly-doped region having a first conductivity type;
• a second lightly-doped region formed in said first lightly-doped region, said second lightly-doped region having a second conductivity type;
• a first heavily-doped region formed in said second lightly-doped region, said first heavily-doped region having said second conductivity type and being electrically connected to said first node;
• a second heavily-doped region formed in said second lightly-doped region, said second heavily-doped region having said first conductivity type and being electrically connected to said first node;
• a third lightly-doped region formed in said first lightly-doped region, said third lightly-doped region having said second conductivity type and being at a spacing from said second lightly-doped region;
• a third heavily-doped region formed in said third lightly-doped region, said third heavily-doped region having said first conductivity type and being electrically connected to a second node;
• a fourth heavily-doped region formed in said third lightly-doped region, said fourth heavily-doped region having said second conductivity type and being electrically connected to said second node;
• and
• a fifth heavily-doped isolated region formed in said first lightly-doped region, interposed between and spaced apart from said second lightly-doped region and said third lightly-doped region, said fifth lightly-doped region having said first conductivity type, wherein relative position of said fifth heavily-doped region with respect to said second and third lightly-doped regions establishes operating parameters for said input protection device.

An input protection device fabricated on an integrated circuit for protecting a circuit structure which is coupled to a first node, said device comprising:

• a first lightly-doped region of P-type material, said first lightly-doped region formed as a well on an Epitaxial layer (EPI) substrate of N-type material, the first lightly-doped region and the EPI substrate being substantially separated by a layer of heavily-doped P-type material;
• a second lightly-doped region of N-type material formed in said first lightly-doped region;
• a first heavily-doped region of N-type material formed in said second lightly-doped region, said first heavily-doped region being electrically connected to said first node;
• a second heavily-doped region of P-type material formed in said second lightly-doped region, said second heavily-doped region being electrically connected to said first node;
• a third lightly-doped region of N-type material formed in said first lightly-doped region, said third lightly-doped region being at a spacing from said second lightly-doped region;
• a third heavily-doped region of P-type material formed in said third lightly-doped region, said third heavily-doped region being electrically connected to a second node;
• a fourth heavily-doped region of N-type material formed in said third lightly-doped region, said fourth heavily-doped region being electrically connected to said second node;
• a fifth heavily-doped isolated region of P-type material formed in said first lightly-doped region, interposed between and spaced apart from said second lightly-doped region and said third lightly-doped region, wherein relative position of said fifth heavily-doped region with respect to said second and third lightly-doped regions establishes operating parameters for said input protection device;
• and
• at least one isolation plug bounding said device, said at least one isolation plug comprising a region of heavily doped N-type material extending substantially from a surface portion of the device to the EPI substrate;
• the spacing between said first heavily-doped region and said third heavily-doped region being greater than the spacing between said second heavily-doped region and said third heavily-doped region, and the spacing between said fifth heavily-doped region and said third heavily-doped region being greater than the spacing between said fourth heavily-doped region and said third heavily-doped region.