ESD PROTECTION DEVICE AND METHOD
First Claim
1. An electronic assembly, comprising:
- first and second external terminals;
a core circuit coupled between the first and second external terminals;
a bipolar transistor electrostatic discharge (ESD) clamp coupled between the first and second external terminals, wherein the bipolar transistor electrostatic discharge (ESD) clam comprises;
an emitter region of a first doping density electrically coupled to the first terminal, a collector region of a second doping density electrically coupled to the second terminal, a base region of a third doping density located between the emitter region and the collector region, and a further region of a fourth doping density located between the base region and the collector region, wherein at least the further region extends to an overlying dielectric-semiconductor interface; and
whereinthe base region has a first dopant boundary with the further region and the collector region has a second dopant boundary with the further region and wherein at least one of the first and second dopant boundaries has a maximum dopant density at a distance Y>
0 beneath the dielectric-semiconductor interface.
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Accused Products
Abstract
An electrostatic discharge (ESD) protection clamp (21, 21′, 70, 700) for protecting associated devices or circuits (24), comprises a bipolar transistors (21, 21′, 70, 700) in which doping of facing base (75) and collector (86) regions is arranged so that avalanche breakdown occurs preferentially within a portion (84, 85) of the base region (74, 75) of the device (70, 700) away from the overlying dielectric-semiconductor interface (791). Maximum variations (ΔVt1)MAX of ESD triggering voltage Vt1 as a function of base-collector spacing dimensions D due, for example, to different azimuthal orientations of transistors (21, 21′, 70, 700) on a semiconductor die or wafer is much reduced. Triggering voltage consistency and manufacturing yield are improved.
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Citations
20 Claims
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1. An electronic assembly, comprising:
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first and second external terminals; a core circuit coupled between the first and second external terminals; a bipolar transistor electrostatic discharge (ESD) clamp coupled between the first and second external terminals, wherein the bipolar transistor electrostatic discharge (ESD) clam comprises; an emitter region of a first doping density electrically coupled to the first terminal, a collector region of a second doping density electrically coupled to the second terminal, a base region of a third doping density located between the emitter region and the collector region, and a further region of a fourth doping density located between the base region and the collector region, wherein at least the further region extends to an overlying dielectric-semiconductor interface; and
whereinthe base region has a first dopant boundary with the further region and the collector region has a second dopant boundary with the further region and wherein at least one of the first and second dopant boundaries has a maximum dopant density at a distance Y>
0 beneath the dielectric-semiconductor interface. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for forming a bipolar transistor electrostatic discharge (ESD) clamp, comprising:
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providing a semiconductor substrate having a first region of a first conductivity type or a second conductivity type and first and second dopant density, respectively, extending to a first surface; forming a first WELL region of a third conductivity type and third doping density extending from the first surface into the first region and having a first lateral boundary; forming a second WELL region of a fourth conductivity type opposite the third conductivity type and having a fourth doping density extending into the first WELL region and having a second lateral boundary separated from the first lateral boundary by a minimum distance D across an intermediate portion of the first region having a fifth dopant density; forming a dielectric-semiconductor interface overlying at least the intermediate portion, and wherein; either;
(i) the minimum distance D is located beneath the dielectric-semiconductor interface by a distance Y>
0, or (ii) the third and fourth doping densities exceed the fifth doping density at a distance Y>
0 below the dielectric-semiconductor interface by at least a factor of 5, or (iii) both (i) and (ii). - View Dependent Claims (11, 12, 13, 14, 15, 16)
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17. A bipolar transistor electrostatic discharge (ESD) clamp formed in a substrate having a first surface, and coupled to first and second terminals, and comprising:
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an emitter coupled to the first terminal, a collector coupled to the second terminal, a base located between the emitter and the collector and an intermediate semiconductor portion coupled between the base and the collector and more lightly doped than the base and the collector; wherein at least the intermediate semiconductor portion extends to a dielectric-semiconductor interface at or near the first surface; and wherein the intermediate semiconductor portion has a first interface with the base and second interface with the collector extending away from the dielectric-semiconductor interface and wherein the first and second interfaces have a minimum separation D located a distance Y>
0 below the dielectric-semiconductor interface. - View Dependent Claims (18, 19, 20)
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Specification