Novel low leakage current cascaded diode structure

A method for forming a cascaded diode providing ESD protection to portions of integrated circuits with reduced substrate leakage current, said cascaded diode being a chain of coupled elemental diodes, comprising:

• fabricating elemental diodes by forming for each diode, an n-well in a p-substrate, a p region and an n region in the n-well, and forming a deep n-well disposed tinder and connected to the n-well;
• connecting electrically the p region of a first elemental diode to a pin or pad at the higher potential side of said portion of an integrated circuit to be protected and the n region of said first elemental region to the p region of the following intermediate elemental diode;
• connecting electrically the p region of an intermediate diode to the n region of the preceding elemental diode and said n region of an intermediate elemental diode to the p region of the following elemental diode;
• connecting electrically the p region a last elemental diode to the n region of the preceding elemental diode and its said n region to the other end of said portion of an integrated circuit.

A method for forming a cascaded diode acting as a Vdd-to-Vss clamp with reduced substrate leakage current and providing ESD protection, said cascaded diode being a chain of coupled elemental diodes, comprising:

• fabricating elemental diodes by forming for each diode, an n-well in a p-substrate, a p region and an n region in the n-well, and forming a deep n-well disposed under and connected to the n-well;
• connecting electrically the p region of a first elemental diode to Vdd, the n region of said first elemental region to the p region of the following intermediate elemental diode;
• connecting electrically the p region of an intermediate diode to the n region of the preceding elemental diode and said n region of an intermediate elemental diode to the p region of the following elemental diode;
• connecting electrically the p region a last elemental diode to the n region of the preceding elemental diode and its said n region to Vss.

A method for forming a cascaded diode acting as a coupling clamp, Vdd-to-Vddo or Vss-to-Vsso, with reduced substrate leakage current and providing ESD protection, said cascaded diode being a chain of coupled elemental diodes, comprising:

• fabricating elemental diodes by forming for each diode, an n-well in a p-substrate, a p region and an n region in the n-well, and forming a deep n-well disposed under and connected to the n-well;
• connecting electrically the p region of a first elemental diode to Vddo, for Vdd-to-Vddo, or to Vs so, for Vss-to-Vsso, and the n region of said first elemental region to the p region of the following intermediate elemental diode;
• connecting electrically the p region of an intermediate diode to the n region of the preceding elemental diode and said n region of an intermediate elemental diode to the p region of the following elemental diode;
• connecting electrically the p region a last elemental diode to the n region of the preceding elemental diode and its said n region to Vdd, for Vdd-to-Vddo, or Vss, for Vss-to-Vsso.

A method for forming a cascaded diode acting as a high-voltage-tolerant I/O-to-Vdd clamp, with reduced substrate leakage current and providing ESD protection, said cascaded diode being a chain of coupled elemental diodes, comprising:

• fabricating elemental diodes by forming for each diode, an n-well in a p-substrate, a p region and an n region in the n-well, and forming a deep n-well disposed under and connected to the n-well;
• connecting electrically the p region of a first elemental diode to a high-voltage-tolerant I/O pad, and the n region of said first elemental region to the p region of the following intermediate elemental diode;
• connecting electrically the p region of an intermediate diode to the n region of the preceding elemental diode and said n region of an intermediate elemental diode to the p region of the following elemental diode;
• connecting electrically the p region a last elemental diode to the n region of the preceding elemental diode and its said n region to Vdd.