Actel Corporation, Inc.

Abdelshafy A Eltoukhy

John L McCollum

Frank W Hawley

Ying W Go

Douglas C Galbraith

Gregory William Bakker

Michael G Ahrens

Abdul R Forouhi

Esmat Z Hamdy

Chenming Hu

Steve S Chiang

An antifuse comprises a lower electrode formed from a metal layer in a microcircuit. A interlayer dielectric layer is disposed over the lower electrode and has an aperture formed therein. A conductive plug, formed from a material such as tungsten, is formed in the aperture. The upper surface of the interlayer dielectric is etched back to create a raised portion of the plug. The upper edges of the plug are rounded. An antifuse layer, preferably comprising a silicon nitride, amorphous silicon, silicon nitride sandwich incorporating a thin silicon dioxide layer above or below the amorphous silicon layer or such a sandwich structure covered by a titanium nitride layer, is disposed above the plug. An upper electrode, preferably comprising a metal layer is disposed over the antifuse layer.

Raised tungsten plug antifuse and fabrication processes

A metal-to-metal antifuse disposed between two aluminum metallization layers in a CMOS integrated circuit or similar structure includes an antifuse material layer having a substantially aluminum-free conductive link. The substantially aluminum-free link is formed by forming a first barrier metal layer out of TiN having a first thickness, a second barrier metal layer out of TiN having a second thickness which may be less than said first thickness, the first and second barrier metal layers separating the antifuse material layer from first and second electrodes. The antifuse is programmed by applying a voltage potential capable of programming the antifuse across the electrodes with the more positive side of the potential applied to the electrode adjacent the barrier metal layer having the least thickness. In another aspect of the invention, an antifuse having a first barrier metal layer of a first thickness and a second barrier metal layer of a second thickness may be fabricated wherein the first thickness is less than the second thickness and wherein programming of the antifuse is accomplished by placing the more positive voltage of the programming voltage supply on the electrode of the antifuse adjacent the first barrier metal layer.

Metal-to-metal via-type antifuse

Fabrication process for raised tungsten plug antifuse

An antifuse may be fabricated as a part of an integrated circuit in a layer located above and insulated from the semiconductor substrate. The antifuse includes a lower first metal electrode, a first antifuse dielectric layer, preferably silicon nitride, disposed on the lower first electrode and an antifuse layer, preferably amorphous silicon, disposed on the first dielectric layer. An inter-layer dielectric layer is disposed on the antifuse layer and includes an antifuse via formed completely therethrough. A second antifuse dielectric layer, preferably silicon nitride, is disposed over the amorphous silicon layer in the antifuse via, and an upper second metal electrode is disposed over the second dielectric layer in the antifuse via.

Electrically programmable antifuse incorporating dielectric and

A metal-to-metal antifuse disposed between two aluminum metallization layers in a CMOS integrated circuit or similar structure includes an antifuse material layer having an aluminum-free conductive link. The aluminum-free link is formed by forming a first barrier metal layer out of TiN having a first thickness, a second barrier metal layer out of TiN having a second thickness which may be less than said first thickness, the first and second barrier metal layers separating the antifuse material layer from first and second electrodes. The antifuse is programmed by applying a voltage potential capable of programming the antifuse across the electrodes with the more positive side of the potential applied to the electrode adjacent the barrier metal layer having the least thickness. In another aspect of the invention, an antifuse having a first barrier metal layer of a first thickness and a second barrier metal layer of a second thickness may be fabricated wherein the first thickness is less than the second thickness and wherein programming of the antifuse is accomplished by placing the more positive voltage of the programming voltage supply on the electrode of the antifuse adjacent the first barrier metal layer.

Method of programming an improved metal-to-metal via-type antifuse

An antifuse comprises first and second electrodes separated by an antifuse material having a thickness selected to impart a desired target programming voltage to the antifuse. The antifuse material comprises a solid material stable at temperatures below about 600.degree. C., having a defect density less than about 100 defects/cm.sup.2, a breakdown field less than about 10 megavolts/cm, a dielectric constant lower than about 4.0, a resistivity of greater than about 10.sup.4 ohm-cm. The antifuse material may comprise organic materials such as polyimides compatible with high-temperature processes including cured polyamic acids, pre-imidazed polymers, photo-sensitive polyimides, and other polimides such as pyralin, probimide, PIQ, etc. The antifuse materials of the present invention also include fluorinated polymers having very low dielectric constants, such as teflon, paralines, polyphenylquinoxaline, benzocyclobutene polymers, and perfluoropolymers.

Antifuse with improved antifuse material

An additional column (or row) track is provided in an antifuse based interconnect array containing circuit structures identical to the circuit structures in the remaining columns of the array, except that antifuse vias are filled with contact or via plugs. These plug antifuse substitutes are addressable in the same manner and by the same circuitry as the antifuses on the integrated circuit. The programmed antifuse is addressed, a test voltage is placed on the V.sub.pp input pin on the integrated circuit, and the current drawn by the antifuse is measured. The plug antifuse substitute is addressed, the test voltage is placed on the V.sub.pp input pin on the integrated circuit, and the current drawn by the plug antifuse substitute is measured. The resistance of the entire circuit path which includes the programmed antifuse is calculated using the test voltage and the measured antifuse current and the resistance of the entire circuit path which includes the plug antifuse substitute is calculated using the test voltage and the measured plug antifuse substitute current. The difference between the two resistance values is an accurate measure of the resistance of the programmed antifuse.

Apparatus and method for determining the resistance of antifuses in an

Antifuses having minimum areas are formed by a process including the steps of forming doped regions in a semiconductor substrate, forming a dielectric layer over the surface of the substrate, performing masking and etching steps to form apertures in the dielectric layer over portions of the doped regions where antifuses are to be formed, depositing a second dielectric layer over the first dielectric layer and the apertures, the second dielectric layer having a faster etch rate than the first dielectric layer, etching the second dielectric layer to leave spacers at the edges of the apertures, forming the antifuse dielectric in the apertures, and forming upper antifuse electrodes over the antifuse dielectric. In another process, a process for forming antifuses includes the steps of forming a dielectric layer over the surface of a semiconductor substrate, forming a first layer of polysilicon over the insulating layer, forming apertures in between portions of the first polysilicon layer where antifuses are to be formed, doping the exposed regions in the substrate using the polysilicon as a masking member, depositing an oxide over the polysilicon regions, etching the oxide to expose the substrate between the regions of first layer polysilicon, forming the antifuse dielectric in the apertures, and forming upper antifuse electrodes over the antifuse dielectric. The process of the present invention may also be used to form antifuses in layers above the substrate.

Method of forming antifuses having minimum areas

Apparatus and method determining the resistance of antifuses in an array

A circuit for preventing false programming of unselected anti-fuses in an anti-fuse array includes a series impedance including a plurality of transistors which may be used for partial address selection connected between a source of programming voltage and a bit line.

Circuit for preventing false programming of anti-fuse elements

A semiconductor or substrate of a first conductivity type includes a well structure of a second conductivity type formed therein. A first low voltage MOS transistor includes spaced apart source and drain regions of the first conductivity type in the well. A first transistor gate lies above a channel region which is disposed between the source and drain regions of the first low voltage MOS transistor and is separated therefrom by a gate dielectric having a first thickness. A second high voltage transistor includes spaced apart source and drain regions of the first conductivity type in the well. A second transistor gate lies above a channel region which is disposed between the source and drain regions of the second high voltage transistor and is separated therefrom by a gate dielectric having a second thickness which is greater than the thickness of the gate dielectric of the first low voltage MOS transistor. A first contact diffusion, having the same conductivity type as the well, is located at the edge of the well closest to the first low voltage transistor, and is connected to a source of voltage. A second contact diffusion, having the same conductivity type as the well, is located at the edge of the well closest to the second high voltage transistor, and is also connected to the source of voltage.

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San Jose, CA, United States of America

Abdelshafy A Eltoukhy