ESD protection device and method
First Claim
1. A method for forming a bipolar transistor electrostatic discharge (ESD) clamp, comprising:
- 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; and
forming a dielectric-semiconductor interface overlying at least the intermediate portion;
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).
18 Assignments
0 Petitions
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.
14 Citations
18 Claims
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1. 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; and forming a dielectric-semiconductor interface overlying at least the intermediate portion; 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 (2, 3, 4, 5, 6, 7)
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8. A method for forming a bipolar transistor electrostatic discharge (ESD) clamp coupled to first and second external terminals between which a core circuit is coupled, the method comprising:
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forming an emitter region of a first doping density electrically coupled to the first terminal; forming a collector region of a second doping density electrically coupled to the second terminal; forming a base region of a third doping density located between the emitter region and the collector region; and forming a further region of a fourth doping density located between the base region and the collector region, at least the further region extending to an overlying dielectric-semiconductor interface; wherein the 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 (9, 10, 11, 12, 13, 14, 15)
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16. A method for producing a bipolar transistor electrostatic discharge (ESD) clamp coupled to first and second terminals, the method comprising:
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forming in a substrate an emitter coupled to the first terminal; forming in the substrate a collector coupled to the second terminal; forming in the substrate a base between the emitter and the collector; forming a dielectric-semiconductor interface at or near a first surface of the substrate; and producing the bipolar transistor ESD clamp to further include an intermediate semiconductor portion in the substrate, which is coupled between the base and the collector, which is more lightly doped than the base and the collector, and which extends to the dielectric-semiconductor interface; 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 (17, 18)
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Specification