Low leakage capacitor for analog floating-gate integrated circuits
AssigneeTexas Instruments Incorporated
InventorsImran Mahmood Khan, Allan T. Mitchell, Kaiping Liu
Life of this patent
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Abstract
An analog floating-gate electrode in an integrated circuit, and method of fabricating the same, in which trapped charge can be stored for long durations. The analog floating-gate electrode is formed in a polycrystalline silicon gate level, and includes portions serving as a transistor gate electrode, a plate of a metal-to-poly storage capacitor, and a plate of poly-to-active tunneling capacitors. Silicide-block silicon dioxide blocks the formation of silicide cladding on the electrode, while other polysilicon structures in the integrated circuit are silicide-clad.
Claims13
An integrated circuit formed at a semiconductor surface of a body, including an electrically programmable capacitor structure for an analog semiconductor integrated circuit, the integrated circuit comprising:
- a first polysilicon electrode;
- silicide-block silicon dioxide disposed over the first polysilicon electrode, the silicide-block silicon dioxide being free of nitrogen;
- a capacitor dielectric film disposed over the silicide-block silicon dioxide over the first polysilicon electrode, the capacitor dielectric film comprising nitrogen;
- a first conductive plate, comprising a metal and disposed over a first portion of the first polysilicon electrode with the capacitor dielectric film and the silicide-block silicon dioxide therebetween;
- a second polysilicon electrode, having at least a portion clad with a metal silicide, the second polysilicon electrode formed from the same polysilicon layer as the first polysilicon electrode;
- and
- a second conductive plate, comprising a metal and disposed over the clad portion of the second polysilicon electrode with the capacitor dielectric film therebetween.
An analog circuit, formed at a semiconductor surface of a body, the circuit comprising:
- first and second transistors, each having source and drain regions formed at an active region of the semiconductor surface, and having a gate electrode;
- a storage capacitor, having a first plate coupled to the gate of the first transistor, and having a second plate coupled to a reference voltage;
- a first tunnel capacitor, having a first plate connected to the first plate of the storage capacitor, and a second plate coupled to a first terminal;
- a second tunnel capacitor, having a first plate connected to the first plate of the storage capacitor, and a second plate coupled to a second terminal;
- wherein the first plate of the storage capacitor, the first plate of the first tunnel capacitor, the first plate of the second tunnel capacitor, and a gate electrode of the first transistor, are formed as portions of a first floating gate electrode comprised of polycrystalline silicon;
- wherein the gate electrode of the second transistor is comprised of polycrystalline silicon from the same level as the first floating gate electrode, and is clad with a metal silicide;
- wherein the first floating gate electrode is protected from the metal silicide by silicide-block silicon dioxide;
- wherein the second plates of the first tunnel capacitor and second tunnel capacitors are formed by an active region at the surface;
- and wherein the second plate of the storage capacitor is comprised of a metal overlying a portion of the first floating gate electrode, with a capacitor dielectric film and the silicide-block silicon dioxide therebetween.
An analog reference circuit constructed at a semiconductor surface of a body, comprising:
- an amplifier, having first and second MOS transistor inputs and an output;
- a reference capacitor, having a first plate coupled to the first input of the amplifier, and having a second plate coupled to a ground reference voltage;
- a feedback capacitor, having a first plate coupled to the second input of the amplifier, and having a second plate coupled to the output of the amplifier;
- a first tunnel capacitor, having a first plate connected to the first plate of the reference capacitor, and a second plate formed in a first active region of the semiconductor surface, and coupled to a first terminal;
- a second tunnel capacitor, having a first plate connected to the first plate of the reference capacitor, and a second plate formed in a second active region of the semiconductor surface, and coupled to a second terminal;
- wherein the first plate of the reference capacitor, the first plate of the first tunnel capacitor, the first plate of the second tunnel capacitor, and a gate of the first MOS transistor input of the amplifier, are formed as portions of a first floating gate electrode comprised of polycrystalline silicon having a silicide-block silicon dioxide film thereover;
- and wherein the second plate of the reference capacitor is formed as a portion of a common conductor layer comprised of a metal overlying a portion of the first floating gate electrode, with a capacitor dielectric film and the silicide-block silicon dioxide therebetween.
Dependencies are inferred from the claim text.