Complementary vertical SCRs for SOI and triple well processes
AssigneeNational Semiconductor Corporation
InventorsVladislav Vashchenko, Ann Concannon, Peter J. Hopper, Marcel ter Beek
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Abstract
In an ESD protection device using a SCR-like structure, a vertical device is provided that is highly robust and easily allows the triggering voltage to be adjusted during manufacture. Furthermore it is implementable in complementary form based on PNP and NPN BJT structures, to provide both positive and negative pulse protection.
Claims6
A vertical SCR (silicon controlled rectifier) ESD (electrostatic discharge) protection structure, comprising
- a BJT structure that includes an emitter, a base, a collector, a collector contact, and a first buried layer of a first conductivity type contacting the collector and contacting the collector contact through a first sinker, and
- a second buried layer of opposite conductivity type to the first buried layer, and contacted through a second sinker, the emitter and base of the BJT being electrically connected to define one of the cathode or anode of the SCR, and the second sinker and collector contact of the BJT being electrically connected to define the other of the anode or cathode of the SCR.
A vertical SCR ESD protection structure for protecting against negative voltage swings, implementable using SOI (Silicon on insulator) or triple well process steps, comprising
- a PNP BJT structure that includes an emitter, a base, a collector with collector contact, and a p-buried layer contacting the collector through a p-type sinker, and
- an n-type sinker, and an n-buried layer substantially at the same depth as the p-buried layer and abutting the p-buried layer, the emitter being electrically connected to the base of the BJT to define an anode of the SCR, and the n-type sinker being electrically connected to the collector contact of the BJT to define a cathode of the SCR.
An adjustable ESD triggering structure, in which the triggering voltage can be adjusted, comprising
- a BJT structure that includes an emitter, a base, and a collector contacting a first buried layer through a sinker, the collector, sinker and first buried layer being of a first conductivity type, and
- a second buried layer and sinker of a second conductivity type electrically connected to the collector of the BJT, the second buried layer being arranged substantially at the same depth as the first buried layer, and abutting the first buried layer at selectable laterally defined locations.
A method of adjusting the triggering voltage of an ESD triggering structure, comprising
- providing a BJT structure having an emitter, a base, a collector, and a first sinker, and a first buried layer, the collector contacting the first buried layer through the first sinker, and wherein the collector, first sinker and first buried layer are of a first conductivity type;
- the emitter and base defining one of an anode or a cathode of a vertical SCR, and
- providing a second sinker, and a second buried layer of a second conductivity type and electrically connecting the second sinker and collector of the BJT to define the other of an anode or a cathode of the vertical SCR, the second buried layer being substantially at the same depth as the first buried layer, the method further comprising adjusting the size of one or both of the buried layers to provide a desired triggering voltage.
Dependencies are inferred from the claim text.