# US 5,708,289 A · Pad protection diode structure > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,708,289 A - Document ID: US5708289A - Status: Granted - Kind: A - Application number: 08/608,642 - Filed: 1996-02-29 - Granted: 1998-01-13 - Earliest claimed: 1996-02-29 - Assignees: SGS-Thomson Microelectronics S.A. - Inventors: Richard A. Blanchard - Web page: https://patentgrep.com/patent/US5708289A ## CPC - H10D 89/611: {using diodes as protective elements} - H10D 89/60: Integrated devices comprising arrangements for electrical or thermal protection, e.g. protection circuits against electrostatic discharge [ESD] - H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES ## Abstract A protection structure and method are provided for protecting a first pad of an integrated circuit, the integrated circuit having a second pad to receive a first supply voltage. The protection structure includes a first region of a first conductivity type coupled to the first pad; a second region of a second conductivity type coupled to the second pad; a substrate of the second conductivity type contacting the first and second regions; and an epitaxial layer of the first conductivity type. The epitaxial layer has an epitaxial region that contacts the first and second regions. A first diode can be formed outside the substrate between the first and second pads through at least two of the first region, the second region, and the epitaxial region. The protection structure may include a first portion and a second portion, wherein each portion has a different voltage threshold. Accordingly, the first diode can be formed through the second portion, but not the first portion. Hence, the protection structure will not cause interference to a sensitive component adjacent the first portion. ## Claims ### Claim 1 A protection structure for protecting a first pad of an integrated circuit, the integrated circuit having a second pad to receive a first supply voltage, the protection structure comprising: a first region of a first conductivity type coupled to the first pad; a second region of a second conductivity type coupled to the second pad; a substrate of the second conductivity type contacting the first and second regions; and an epitaxial layer of the first conductivity type, the epitaxial layer having a contiguous epitaxial region that contacts the first and second regions, wherein a first diode is formed outside the substrate between the first and second pads through at least two of the first region, the second region, and the epitaxial region. ### Claim 2 (depends on 1) The protection structure of claim 1, wherein the epitaxial region is disposed between the first and second regions, wherein the substrate has a first doping concentration, and wherein the epitaxial region has a second doping concentration that is higher than the first doping concentration so that the first diode is formed through the epitaxial region. ### Claim 3 (depends on 2) The protection structure of claim 2, wherein the epitaxial region further contacts the substrate. ### Claim 4 (depends on 3) The protection structure of claim 3, wherein the second region includes a first highly doped area coupled to the second pad, and a lowly doped area disposed between the first highly doped area and the substrate. ### Claim 5 (depends on 4) The protection structure of claim 4, wherein the second region further includes a second highly doped area disposed between the lowly doped area and the substrate, and wherein the second highly doped area contacts the epitaxial region to form a conduction junction of the first diode. ### Claim 6 (depends on 4) The protection structure of claim 4, wherein the first highly doped area contacts the epitaxial region to form a conduction junction of the first diode. ### Claim 7 (depends on 1) The protection structure of claim 1, wherein the first region contacts the second region to form a conduction junction of the first diode so that the first diode is not formed through the epitaxial region. ### Claim 8 (depends on 7) The protection structure of claim 7, wherein the epitaxial region is disposed between the conduction junction and the substrate. ### Claim 9 (depends on 1) The protection structure of claim 1, wherein the second region includes a highly doped buried layer contacting the substrate. ### Claim 10 (depends on 9) The protection structure of claim 9, further comprising: a lowly doped region of the first conductivity type disposed between the epitaxial region and the substrate to form a boundary therebetween. ### Claim 11 (depends on 10) The protection structure of claim 10, wherein each of the epitaxial region and the lowly doped region has a doping concentration that is highest along the boundary. ### Claim 12 (depends on 1) The protection structure of claim 1, wherein the integrated circuit further includes a third pad to receive a second supply voltage, the protection structure further comprising: a second diode coupled between the first and third pads. ### Claim 13 (depends on 1) The protection structure of claim 1 in combination with the integrated circuit, wherein the integrated circuit further includes a component disposed adjacent the protection structure, wherein the protection structure includes a first portion having a first conduction junction with a first voltage threshold and a second portion having a second conduction junction with a second voltage threshold, and wherein the first and second voltage thresholds are different. ### Claim 14 (depends on 13) The combination of claim 13, wherein the protection structure is arranged so that carrier flow occurs only in the second portion when a voltage having a value between the first and second thresholds is applied to the first pad. ### Claim 15 (depends on 13) The combination of claim 13, wherein the protection structure is arranged so that carrier flow does not occur in the first portion when a voltage having a value between the first and second thresholds is applied to the first pad. ### Claim 16 (depends on 1) The protection structure of claim 1, wherein the second region contacts the epitaxial region to form a conduction junction, and wherein at least a portion of the epitaxial region is disposed between the conduction junction and the substrate. ### Claim 17 (depends on 1) The protection structure of claim 1, wherein the contiguous epitaxial region that contacts the first and second regions further contacts the substrate, and wherein the contiguous epitaxial region includes an uninterrupted path of lowly doped semiconductor material of the first conductivity type to provide a conduction path between the first and second regions. ### Claim 18 An integrated circuit comprising: a first power pad; a second power pad; a third pad to receive a signal; and a protection structure that protects the third pad, the protection structure including a plurality of regions including a plurality of P regions and a plurality of N regions that together form a plurality of PN junctions, each of the plurality of PN junctions being formed at a physical intersection between one of the plurality of P regions and one of the plurality of N regions, at least one of the plurality of regions being a lowly doped region, the protection structure being arranged so that every path between the first power pad and the second power pad passes through the lowly doped region and at least three of the plurality of PN junctions, wherein at least one of the plurality of regions forms a portion of a diode disposed between the second power pad and the third pad to protect the third pad, wherein another one of the plurality of regions forms a substrate such that the diode is disposed outside the substrate, and wherein the plurality of regions is arranged to prevent carrier flow from the diode from causing a latch-up condition between the first power pad and the second power pad. ### Claim 19 (depends on 18) The integrated circuit of claim 18, and wherein the plurality of regions is arranged such that carrier flow from the diode does not pass through the substrate. ### Claim 20 (depends on 19) The integrated circuit of claim 19, wherein the lowly doped region is a portion of an epitaxial layer contacting the substrate, and wherein carrier flow from the diode is directed through the portion of the epitaxial layer so that the carrier flow does not pass through the substrate. ### Claim 21 A method for protecting a signal pad of an integrated circuit, the signal pad being adapted to receive a signal, the integrated circuit including a first power pad to receive a first supply reference, and a second power pad to receive a second supply reference, the method comprising the step of: forming a protection structure including a plurality of regions including a plurality of P regions and a plurality of N regions that together form a plurality of PN junctions, each of the plurality of PN junctions being formed at a physical intersection between one of the plurality of P regions and one of the plurality of N regions, at least one of the plurality of regions being a lowly doped region, the protection structure being arranged so that every path between the first power pad and the second power pad passes through the lowly doped region and at least three of the plurality of PN junctions, wherein at least one of the plurality of regions forms a portion of a diode in the integrated circuit between the signal pad and the first power pad to protect the signal pad, wherein another one of the plurality of regions forms a substrate such that the diode is disposed outside the substrate, the diode being disposed so that when the diode is activated, carrier flow from the diode cannot cause a latch-up condition between the first power pad and the second power pad. ### Claim 22 (depends on 21) The method of claim 21, wherein the substrate has a first doping concentration, and wherein the step of forming includes a step of: providing, as the lowly doped region, an epitaxial region of an epitaxial layer that contacts the substrate, the epitaxial region having a second doping concentration that is higher than the first doping concentration so that a conducting path of the diode is formed outside the substrate and through the epitaxial region. ### Claim 23 (depends on 21) The method of claim 21, wherein the step of forming includes a step of: providing, as the lowly doped region, at least a portion of an epitaxial layer between a conduction junction of the diode and the substrate. ### Claim 24 (depends on 21) The method of claim 21, wherein the step of forming includes steps of: providing a buried layer that contacts the substrate; and providing, as the lowly doped region, an epitaxial region of an epitaxial layer that contacts the buried layer so that the buried layer is disposed between the epitaxial region and the substrate to form a conducting path of the diode that is outside the substrate and through a boundary between the epitaxial region and the buried layer. ### Claim 25 An integrated circuit, comprising: a first pad to receive a signal; a second power pad to a receive a supply reference; a component; and a protection structure, coupled between the first pad and the second power pad, that protects the first pad, the protection structure including a first portion adjacent the component and a second portion, wherein the first portion has a first conduction junction with a first voltage threshold, wherein the second portion has a second conduction junction with a second voltage threshold, and wherein the first and the second voltage thresholds are different. ### Claim 26 (depends on 25) The integrated circuit of claim 25, wherein the protection structure is arranged so that carrier flow through the protection structure occurs only through the second portion when a voltage having a value between the first and second thresholds is applied to the first pad. ### Claim 27 (depends on 25) The integrated circuit of claim 25, wherein the protection structure is arranged so that carrier flow does not occur through the first portion of the protection structure when a voltage having a value between the first and second thresholds is applied to the first pad. ### Claim 28 A protection structure for protecting a first pad of an integrated circuit, the integrated circuit having a second pad to receive a supply voltage, the protection structure comprising: a first region of a first conductivity type coupled to the first pad; a second region of a second conductivity type having a first highly doped area coupled to the second pad and a lowly doped area; and a substrate of the second conductivity type contacting the first and second regions, wherein the lowly doped area of the second region is disposed between the first highly doped area of the second region and the substrate, and wherein a diode is formed outside the substrate between the first and second regions. ### Claim 29 (depends on 28) The protection structure of claim 28, wherein the second region further includes a second highly doped area disposed between the lowly doped area and the substrate. ### Claim 30 (depends on 29) The protection structure of claim 29, wherein both the first highly doped area and the lowly doped area are diffusion areas, and the second highly doped area is a buried area.