Method for programming antifuses for reliable programmed links

• US 5,502,395 A
• Filed: 05/25/1994
• Issued: 03/26/1996
• Est. Priority Date: 05/25/1994
• Status: Expired due to Term

• Current Assignee: Crosspoint Solutions Incorporated
• Original Assignee: Crosspoint Solutions Incorporated
• Inventors: Allen, William J.
• Primary Examiner(s): Regan, Maura K.
• Application Number:
  US08/249,001
• Time in Patent Office: 671 Days
• Field of Search: 324/713, 324/715, 324/525, 324/550, 307/202.1
• US Class Current: 324/713
• CPC Class Codes: G11C 17/18 Auxiliary circuits, e.g. for writing into memory
• CPC Class Codes: G11C 29/02 Detection or location of defective auxiliary circuits, e.g. defective refresh counters
• CPC Class Codes: G11C 29/027 in fuses
• CPC Class Codes: G11C 29/028 with adaption or trimming of parameters
• CPC Class Codes: G11C 29/50 Marginal testing, e.g. race, voltage or current testing
• CPC Class Codes: G11C 29/50008 of impedance

Abstract

A method for programming antifuses is described. Programming current pulses are driven through a selected antifuse. The resistance through the antifuse is then measured and compared to a predetermined resistance value. These measuring, comparing and driving steps are repeated until the measured resistance is less than a predetermined resistance value and the antifuse is annealed by driving a predetermined amount of current through the antifuse for a first predetermined amount of time and ramping down the current in a predetermined manner in a second predetermined amount of time. With this programming method no complex methods and circuits to reverse the polarities of voltage across and currents through the antifuse are required.

Claims

1. A method of programming selected antifuses in a plurality of antifuses in an integrated circuit, said method comprising

driving a programming pulse of current through a selected previously unprogrammed antifuse;

measuring a resistance through said antifuse after said programming pulse;

comparing said measured resistance with a predetermined resistance value;

repeating said driving, measuring and comparing steps until said measured resistance is less than a predetermined resistance value; and

driving a current at a predetermined voltage through said antifuse for a first predetermined amount of time and ramping down said current in a predetermined manner in a second predetermined amount of time;

whereby said selected antifuses have low and stable programmed resistances.

2. The method of claim 1 wherein said programming pulses are unidirectional.

3. The method of claim 1 wherein said pulse driving step comprises driving said pulse of current at a predetermined magnitude for a third predetermined amount of time.

4. The method of claim 3 wherein said predetermined magnitude comprises 15 mA.

5. The method of claim 3 wherein said third predetermined amount of time comprises 0.5 mS.

6. The method of claim 1 wherein said first predetermined amount of time comprises 10 mS.

7. The method of claim 1 wherein said predetermined manner is a linear decrease.

8. The method of claim 3 wherein said repeating step comprises the substep of increasing said predetermined magnitude in said programming pulse driving step after said driving, measuring and comparing steps are repeated a predetermined number of times without said measured resistance having decreased below said predetermined resistance value.

9. The method of claim 1 further comprising the steps of:

after said current driving step, remeasuring said resistance of said antifuse; and

if said resistance value has changed, returning to said first driving step.