Polycrystalline silicon diode string for ESD protection of different power supply connections
AssigneeTaiwan Semiconductor Manufacturing Company, Ltd.
InventorsKuo Reay Peng, Jian-Hsing Lee, Shui-Hung Chen
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Abstract
An ESD protection circuit protects integrated circuits having multiple power supply voltage sources from damage when an ESD event causes excessive differential voltages between the multiple separate power supply voltage sources. The ESD protection circuit has a string of serially connected lateral polycrystalline silicon diodes characterized by consistent turn-on threshold voltage level such that as the number of stage of the ESD protection circuit increase, the turn-on voltage threshold of the ESD protection circuit increase linearly.
Claims28
An electrostatic discharge circuit connected between a first power supply voltage source and a second power supply voltage source to protect internal integrated circuits from damage due to an electrostatic discharge, said electrostatic discharge circuit comprising:
- a plurality of serially connected polycrystalline silicon diodes formed on a surface of a substrate, each diode having a first electrode and second electrode, said plurality of serially connected polycrystalline diodes including a first diode of the plurality of 9 diodes has its first electrode connected to the first power supply voltage source, and a last diode having its second electrode connected to the second power supply voltage source,
- wherein the first electrode is a first region of a polycrystalline silicon being heavily doped with an impurity of a first type and the second electrode is a second region of a polycrystalline silicon being heavily doped with an impurity of a second type, said second region being adjoined to the first region to form an electrical junction.
An integrated circuit formed on a substrate comprising:
- a first power distribution network connected to a first power supply voltage source;
- a second power distribution network connected to a second power supply voltage source;
- a plurality of internal circuits connected between the first and second power distribution networks;
- and
- an electrostatic discharge circuit connected between a first power supply voltage source and a second power supply voltage source to protect said internal circuits from an ESD event, said electrostatic discharge circuit comprising:
- a plurality of serially connected polycrystalline silicon diodes formed on a surface of a substrate, each diode having a first electrode and second electrode, said plurality of serially connected polycrystalline diodes including a first diode of the plurality of diodes has its first electrode connected to the first power supply voltage source, and a last diode having its second electrode connected to the second power supply voltage source,
- wherein the first electrode is a first region of a polycrystalline silicon being heavily doped with an impurity of a first type and the second electrode is a second region of a polycrystalline silicon being heavily doped with an impurity of a second type, said second region being adjoined to the first region to form an electrical junction.
A method for forming an electrostatic discharge circuit comprising serially connected polycrystalline silicon diodes, said method comprising the steps of:
- providing a substrate;
- forming polycrystalline silicon members upon said substrate:
- doping a first portion of each of said polycrystalline silicon members with an impurity of a first type;
- doping a second portion of each of said polycrystalline silicon members with an impurity of a second type such that a junction is formed where the first portion of each of said polycrystalline silicon members adjoins said second portion of said polycrystalline members;
- connecting the second portion of one polycrystalline section to the first portion of a subsequent polycrystalline silicon member;
- connecting the first portion of a first polycrystalline silicon member to a first power supply voltage source;
- and
- connecting the second portion of a last polycrystalline silicon member to a second power supply voltage source.
Dependencies are inferred from the claim text.