Electro-static discharge protection circuit with bimodal resistance characteristics
First Claim
1. An electronic discharge protection circuit integrated in a CMOS integrated circuit chip having a substrate and an electrical contact pad, comprising:
- a first region of a p conductivity type semiconductor material formed in said substrate;
a single field effect transistor formed in said first region, said field effect transistor having highly doped source and drain regions of said n conductivity type formed at spaced apart locations in said first region and a channel region formed by the portion of said p conductivity type first region between said spaced apart source and drain regions, wherein one of said source or drain regions is positioned adjacent said well region and extends partially into said well region, wherein said field effect transistor is subject to breakdown conduction in response to externally generated voltage surges applied to said pad;
a well region of an n conductivity type semiconductor material formed in said substrate adjacent said first region and having a resistively to current flowing from said pad to said field effect transistor that increases upon breakdown of said field effect transistor; and
wherein said well region is electrically coupled to said contact pad at a position spaced apart from sad first region.
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Accused Products
Abstract
An electrostatic discharge protection circuit employing an extended resistive structure having bimodal resistance characteristics in series with an input/output buffer circuit and an input/output electrical contact pad on an integrated circuit. The extended resistive structure is integrally formed with the device or devices in the buffer circuit most susceptible to damage due to ESD breakdown effects In a first resistance mode during normal circuit operations, the resistor has a low resistance value and introduces virtually no additional load to the input/output buffer circuitry. In a second mode of operation during ESD discharge, the resistor has a second significantly higher resistance which reduces current values during the ESD event thereby protecting the buffer circuit. Thick oxide snap-back device is also employed to provide a parallel ESD discharge path with low power dissipation.
74 Citations
13 Claims
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1. An electronic discharge protection circuit integrated in a CMOS integrated circuit chip having a substrate and an electrical contact pad, comprising:
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a first region of a p conductivity type semiconductor material formed in said substrate; a single field effect transistor formed in said first region, said field effect transistor having highly doped source and drain regions of said n conductivity type formed at spaced apart locations in said first region and a channel region formed by the portion of said p conductivity type first region between said spaced apart source and drain regions, wherein one of said source or drain regions is positioned adjacent said well region and extends partially into said well region, wherein said field effect transistor is subject to breakdown conduction in response to externally generated voltage surges applied to said pad; a well region of an n conductivity type semiconductor material formed in said substrate adjacent said first region and having a resistively to current flowing from said pad to said field effect transistor that increases upon breakdown of said field effect transistor; and wherein said well region is electrically coupled to said contact pad at a position spaced apart from sad first region. - View Dependent Claims (2, 3)
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4. An improved integrated circuit, comprising:
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a substrate of a first conductivity type semiconductor material having an upper major surface; an electrical contact pad formed on said upper major surface of said substrate; a single field effect transistor formed on said upper major surface of said substrate, said field effect transistor having a source region, a channel region and a drain region formed in said substrate, wherein said source and drain regions are spaced apart highly doped regions of a second conductivity type formed in said substrate and wherein said channel region has a length defined by the spacing between the source region and the drain region, and wherein said source, drain and channel regions have a width dimension substantially grater than the channel length, and wherein said field effect transistor is subject to breakdown conduction in response to externally generated voltage surges applied to said pad; a lightly doped region of said second conductivity type formed adjacent said field effect transistor and having an extended contact region with said field effect transistor along said width dimension and having a resistively to current flowing from said pad to said field effect transistor that increases upon breakdown of said field effect transistor; a highly doped contact region of said second conductivity type formed on said upper major surface of said substrate, spaced apart from said field effect transistor by said lightly doped region; and conductive means, electrically coupled to said highly doped contact region and said pad, for providing an electrical contact therebetween. - View Dependent Claims (5, 6, 7, 8, 9)
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10. An improved integrated circuit device comprising:
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a substrate of a first conductivity type semiconductor material having an upper major surface; an electrical contact pad formed on said upper major surface of said substrate; a single field effect transistor formed on said upper major surface of said substrate, said field effect transistor having a source region, a channel region and a drain region formed in said substrate and a gate oxide layer formed over said channel region, wherein said source and drain regions are spaced apart highly doped substrate and wherein said channel region has a length defined by the spacing between the source region and the drain region, and wherein said channel length is less than 2 microns and said gate oxide thickness is less than 275 Å and
wherein said field effect transistor has a width perpendicular to the length of said channel region, and wherein said field effect transitory is subject to breakdown conduction in response to externally generated voltage surges applied to said pad;a lightly doped region of said second conductivity type formed adjacent said field effect transistor and having an extended contact region with said field effect transistor along the width dimension and having a resistively to current flowing from said pad to sad field effect transistor that increases upon breakdown of said field effect transistor; a highly doped contact region of said second conductivity type formed on said upper major surface of said substrate, spaced apart from said field effect transistor by said lightly doped region; and conductive means, electrically coupled to said highly doped contact region and said pad, for providing an electrical contact therebetween. - View Dependent Claims (11, 12, 13)
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Specification