Apparatus and method for measuring programmed antifuse resistance

• US 5,414,364 A
• Filed: 09/08/1993
• Issued: 05/09/1995
• Est. Priority Date: 09/08/1993
• Status: Expired due to Term

• Current Assignee: Actel Corporation (Microchip Technology Incorporated)
• Original Assignee: Actel Corporation (Microchip Technology Incorporated)
• Inventors: McCollum, John L.
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): DO, DIEP N
• Application Number:
  US08/117,955
• Time in Patent Office: 608 Days
• Field of Search: 324/550, 324/691, 324/713, 324/715, 324/719, 324/158 R, 324/158.1, 307/202.1, 307/465, 365/96, 371/22.5, 371/22.6, 257/530
• US Class Current: 324/550
• CPC Class Codes: G01R 27/14 Measuring resistance by measuring current or voltage obtained from a reference source G01R27/16, G01R27/20, G01R27/22 take precedence
• CPC Class Codes: G01R 31/2884 using dedicated test connectors, test elements or test circuits on the IC under test G01R31/2855 takes precedence
• CPC Class Codes: G11C 17/16 using electrically-fusible links
• CPC Class Codes: G11C 29/02 Detection or location of defective auxiliary circuits, e.g. defective refresh counters
• CPC Class Codes: H01L 22/14 for electrical parameters, e.g. resistance, deep-levels, CV, diffusions by electrical means

Abstract

Apparatus for measuring the resistance of a programmed antifuse in an integrated circuit is integrated on the same integrated circuit as the antifuse and is controlled by a programming circuit disposed on an integrated circuit and comprises a first voltage sensing transistor having a first drain/source electrically connected to a first I/O pad, a gate electrically connected to the programming circuit, and a second drain/source electrically connected to a first electrode of the antifuse, and a second voltage sensing transistor having a first drain/source electrically connected to a second I/O pad, a gate electrically connected to the programming circuit, and a second drain/source electrically connected to a second electrode of the antifuse.

Claims

1. In an integrated circuit having a plurality of antifuses disposed thereon, each of said antifuses having a first electrode and a second electrode, and further having antifuse programming circuitry disposed thereon for selectively configuring a programming path between the first and second electrodes of a selected one of the plurality of antifuses and a source of programming potential, a circuit for determining the resistance of a programmed one of said antifuses comprising:

a first voltage-sensing I/O pad;

a second voltage-sensing I/O pad;

antifuse selection means for selecting one of said antifuses;

first circuit path means, responsive to said selection means, for creating a first voltage-sensing circuit path from said first voltage-sensing I/O pad to the first electrode of an antifuse selected by said selection means, said first voltage-sensing circuit path independent from said programming path;

second circuit path means, responsive to said selection means, for creating a second voltage-sensing circuit path from said second voltage-sensing I/O pad to the second electrode of said antifuse selected by said selection means, said second voltage-sensing circuit path independent from said programming path.

2. A method for determining the resistance of a programmed antifuse disposed in an integrated circuit, including the steps of:

providing a first voltage-sensing circuit path from a first voltage sensing I/O pad on the integrated circuit to a first terminal of the antifuse;

providing a second voltage-sensing circuit path from a second voltage sensing I/O pad on the integrated circuit to a second terminal of the antifuse;

providing a known soaking current to said antifuse from a programming voltage source through a programming path configured from programming circuitry located on said integrated circuit, said programming path independent of said first and second voltage-sensing circuit paths;

measuring the voltage between said first and second voltage-sensing I/O pads with a high impedance voltmeter.

3. In an integrated circuit having a plurality of antifuses disposed thereon, each of said antifuses having a first electrode and a second electrode, and further having antifuse programming circuitry disposed thereon for selectively configuring a programming path between the first and second electrodes of a selected one of the plurality of antifuses and a source of programming potential, a circuit for determining the resistance of a programmed one of said antifuses comprising:

a first voltage-sensing I/O pad;

a second voltage-sensing I/O pad;

first voltage sensing path circuitry, responsive to control signals from said antifuse programming circuitry, for selectively creating a first voltage-sensing circuit path from said first voltage-sensing I/O pad to the first electrode of said selected one of said antifuses, said first voltage-sensing circuit path independent from said programming path; and

second voltage sensing path circuitry, responsive to control signals from said antifuse programming circuitry, for selectively creating a second voltage-sensing circuit path from said second voltage-sensing I/O pad to the second electrode of said selected one of said antifuses, said second voltage-sensing circuit path independent from said programming path.

4. In an integrated circuit having a plurality of antifuses disposed thereon, each of said antifuses having a first electrode and a second electrode, and further having antifuse programming circuitry disposed thereon for selectively configuring a programming path between the first and second electrodes of a selected one of the plurality of antifuses and a source of programming potential, a circuit for determining the resistance of a programmed one of said antifuses comprising:

a first voltage-sensing I/O pad;

a second voltage-sensing I/O pad;

at least one first voltage sensing transistor connected between said first voltage-sensing I/O pad and the first electrode of said selected one of said antifuses, responsive to control signals from said antifuse programming circuitry, for selectively creating a first voltage-sensing circuit path from said first voltage-sensing I/O pad to said first electrode of said selected one of said antifuses, said first voltage-sensing circuit path independent from said programming path; and

at least one second voltage sensing transistor connected between said second voltage-sensing I/O pad and the first electrode of said selected one of said antifuses, responsive to control signals from said antifuse programming circuitry, for selectively creating a second voltage-sensing circuit path from said second voltage-sensing I/O pad to said second electrode of said selected one of said antifuses, said first voltage-sensing circuit path independent from said programming path.