ESD protection circuit with segmented buffer transistor
First Claim
1. An input/output electrostatic discharge protection circuit for protecting semiconductor devices formed on an integrated circuit chip from transient voltage surges which enter through an input/output electrical contact pad on the chip, comprising:
- a field effect buffer transistor, electrically coupled between the electrical contact pad and the semiconductor devices to be protected and providing a current path between the electrical contact pad and a chip reference potential, comprising a plurality of discrete field effect transistor segments electrically connected in parallel; and
resistive means, electrically coupled in series between each transistor segment and the electrical contact pad and 15 integrally formed with each field effect transistor segment, for providing an extended resistive path between the electrical contact pad and the transistor segments.
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Accused Products
Abstract
An electrostatic discharge protection circuit for an integrated circuit employing a segmented field effect buffer transistor between the input/output pad and the active devices on the integrated cicuit. An extended resistive structure is configured in series with the segmented buffer transistor and the input/output electrical contact pad. The extended resistive structure is integrally formed with the individual segments of the buffer FET. The resistive structure may be implemented as an extended n well structure adjacent the FET segments. In a first resistance mode during normal circuit operations, the extended resistive structure 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 resistive structure has a second significantly higher resistance which reduces current values during the ESD event thereby protecting the buffer circuit. A thick oxide snap-back device is also employed to provide a parallel EDS discharge path with low power dissipation.
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Citations
18 Claims
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1. An input/output electrostatic discharge protection circuit for protecting semiconductor devices formed on an integrated circuit chip from transient voltage surges which enter through an input/output electrical contact pad on the chip, comprising:
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a field effect buffer transistor, electrically coupled between the electrical contact pad and the semiconductor devices to be protected and providing a current path between the electrical contact pad and a chip reference potential, comprising a plurality of discrete field effect transistor segments electrically connected in parallel; and resistive means, electrically coupled in series between each transistor segment and the electrical contact pad and 15 integrally formed with each field effect transistor segment, for providing an extended resistive path between the electrical contact pad and the transistor segments. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An integrated circuit, having improved resistance to electrostatic discharge events, comprising:
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a substrate of semiconductor material having an upper major surface; an electrical contact pad formed on the upper major surface of said substrate; a field effect transistor structure formed in the upper major surface of the substrate wherein the field effect structure comprises a plurality of transistor segments each having a source, channel and drain formed in the substrate, and a gate structure formed over the channel region, and wherein the field effect transistor segments extend in a direction perpendicular to the direction of current flow between the source and drain; a resistive structure formed in said upper major surface of said substrate adjacent to, and integrally coupled with, said discrete transistor segments and extending along the direction perpendicular to current flow; and a drain contact diffusion formed in said resistive structure and spaced apart from said drain diffusion and electrically connected to said contact pad. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15)
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16. An integrated circuit, having improved resistance to electrostatic discharge events, comprising:
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a substrate of semiconductor material having an upper major surface; an electrical contact pad formed on the upper major surface of said substrate; a field effect transistor structure formed in the upper major surface of the substrate wherein the field effect structure comprises a plurality of transistor segments each having a source, channel and drain formed in the substrate, and a gate structure formed over the channel region, and wherein the field effect transistor segments extend in a direction perpendicular to the direction of current flow between the source and drain; a plurality of discrete resistive structures formed in said upper major surface of said substrate adjacent to each field effect transistor segment, wherein each discrete resistive structure is integrally coupled with one field effect transistor segment and has an extended dimension along the direction perpendicular to current flow; and a drain contact diffusion formed in each of said resistive structure and spaced apart from said drain diffusion and electrically connected to said contact pad. - View Dependent Claims (17, 18)
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Specification