Methods for preventing disturbance of antifuses during programming

• US 5,194,759 A
• Filed: 02/13/1992
• Issued: 03/16/1993
• Est. Priority Date: 05/18/1990
• Status: Expired due to Term

• Current Assignee: Actel Corporation (Microchip Technology Incorporated)
• Original Assignee: Actel Corporation (Microchip Technology Incorporated)
• Inventors: El-Ayat, Khaled A., Hayes, Kenneth D., Bakker, Gregory W., Speers, Theodore M.
• Primary Examiner(s): Heyman, John S.
• Assistant Examiner(s): Cunningham, Terry D.
• Application Number:
  US07/835,221
• Time in Patent Office: 397 Days
• Field of Search: 307/202.1, 307/465, 307/468, 365/96, 365/225.7
• US Class Current: 327/525
• CPC Class Codes: G11C 17/18 Auxiliary circuits, e.g. for writing into memory

Abstract

A method to minimize disturbance of an already programmed antifuse while programming other antifuses in a circuit includes the steps of determining a preferred order in which to program the antifuses and programming them in the preferred order. High initial programming and soak currents are selected such that the disturb current is small with respect thereto. The magnitude of the disturb current is increased to a value that maintains the antifuse resistance or improves it rather than adversely affect it. Where a circuit node containing a first already programmed antifuse is positioned such that parasitic capacitances may discharge through that antifuse during the programming of a second antifuse, the magnitude of the charge stored at parasitic capacitances associated with the programming path is reduced by reducing the programming voltage when this programming situation is detected. After the initial rupturing of the antifuse dielectric is detected, the programming voltage is increased to its normal value for the soaking period.

Claims

1. A method for minimizing disturbance to a first already programmed antifuse programmed at a programming voltage having a first magnitude developed between an ungrounded potential and a grounded potential caused by the subsequent programming of a second antifuse, including the steps of:

reducing the magnitude of said programming voltage to said second antifuse from said first magnitude to a second, lower magnitude when a condition exists that said first antifuse is electrically connected to a circuit node which will be at said ungrounded potential of said programming voltage to be applied during the programming of said second antifuse and further if said first antifuse is not in the path of programming current through said second antifuse;

applying said programming voltage of said second magnitude to said second antifuse;

increasing said programming voltage to said first magnitude when said second antifuse begins to draw current; and

applying a programming voltage having one of said first and said second magnitudes to said second antifuse when said condition does not exist.