Circuit structure with enhanced electrostatic discharge protection

A silicon controlled rectifier device for protecting a circuit structure which is coupled to a first node, comprising in combination:

• a lightly doped region having a first conductivity type formed in a lightly doped substrate having a second conductivity type;
• a first heavily doped region formed in said lightly doped region having said first conductivity type, said first heavily doped region being electrically connected to said first node;
• a second heavily doped region formed in said lightly doped region having said second conductivity type, said second heavily doped region being electrically connected to said first node;
• a third heavily doped region formed in said substrate having said first conductivity type, said third heavily doped region being spaced from said lightly doped region and said third heavily doped region being electrically connected to a second node;
• a fourth heavily doped region formed in said lightly doped region having said first conductivity type, said fourth heavily doped region positioned between said second and third heavily doped regions;
• and
• a resistor having a first terminal electrically connected to said first node and having a second terminal electrically connected to said fourth heavily doped region, said combination forming a silicon controlled rectifier device which provides an over-voltage current path between said first and second nodes to protect the circuit structure from damage of the type caused by electrostatic discharge between said nodes.

A silicon controlled rectifier device for protecting a circuit structure which is coupled to a first node, comprising in combination:

• a lightly doped region having a first conductivity type formed in a lightly doped substrate having a second conductivity type;
• a first heavily doped region formed in said lightly doped region having said first conductivity type, said first heavily doped region being electrically connected to said first node;
• a second heavily doped region formed in said lightly doped region having said second conductivity type, said second heavily doped region being electrically connected to said first node;
• a third heavily doped region formed in said substrate having said first conductivity type, said third heavily doped region being spaced from said lightly doped region and said third heavily doped region being electrically connected to a second node;
• a fourth heavily doped region formed in said lightly doped substrate having said first conductivity type, said fourth heavily doped region positioned between said second and third heavily doped regions;
• and
• a resistor having a first terminal electrically connected to said first node and having a second terminal electrically connected to said fourth heavily doped region, said combination forming a silicon controlled rectifier device which provides an over-voltage current path between said first and second nodes to protect the circuit structure from damage of the type caused by electrostatic discharge between said nodes.

A semiconductor structure including an integrated circuit and protection circuitry for preventing damage to said integrated circuit during an electrostatic discharge event, said circuit formed in the surface of a lightly doped semiconductor material and connected to first and second bond pads along the surface, said protection circuitry comprising:

• a first bipolar transistor having a first p-doped region connected to the first bond pad, a second p-doped region and an n-type base region between the first and second p-doped regions;
• a second bipolar transistor having a first n-type region connected in common with the base region of said first transistor, a second n-type region and a p-type base region between the first and second n-type regions, said base region in common with the second p-doped region of the first transistor;
• and
• a third bipolar transistor having first and second regions of a first conductivity type and a base region of a second conductivity type between said first and second regions, the first region of said third transistor in common with the base region of either the first or second transistor with one of the first region and the base region of said third transistor having a higher net dopant concentration than the base region of one of the first and second transistors so that during the electrostatic discharge event said third transistor is the first in time among said three transistors to go into conduction thereby injecting current into the base region of one of said first two transistors turning said one of said first two transistors on.