Circuit for cancelling and replacing redundant elements

• US 5,838,620 A
• Filed: 02/06/1997
• Issued: 11/17/1998
• Est. Priority Date: 04/05/1995
• Status: Expired due to Term

• Current Assignee: Conversant Intellectual Property Management Inc (MOSAID Technologies Inc. (f/k/a Conversant Intellectual Property Management))
• Original Assignee: Micron Technology, Inc.
• Inventors: Ong, Adrian E., Zagar, Paul S.
• Primary Examiner(s): ZARABIAN, AMIR
• Application Number:
  US08/796,148
• Time in Patent Office: 649 Days
• Field of Search: 365/200, 365/149, 365/225.7, 365/96
• US Class Current: 365/200
• CPC Class Codes: G11C 29/785 with redundancy programming schemes
• CPC Class Codes: G11C 29/838 with substitution of defective spares

Abstract

In an integrated circuit having addressable primary elements and redundant elements which can be programmed to replace primary elements, a circuit and method are provided for cancelling and replacing redundant elements. A circuit is described which can be used in a memory such as a dynamic random access memory (DRAM) which uses a selectively blowable anti-fuse to disable a redundant element which was previously programmed to replace a defective primary element. The disclosure describes a method for permanently cancelling the defective redundant element and replacing the defective redundant element with another redundant element.

Claims

1. A method of repairing an integrated circuit, the method comprising the steps of;

programming a first redundant element to respond to an address of a defective selectively addressable primary element;

one time enabling the first redundant element;

permanently disabling the first redundant element after the step of one time enabling the first redundant element;

programming a second redundant element to respond to an address of the defective selectively addressable primary element; and

one time enabling the second redundant element.

2. The method of claim 1 wherein the integrated circuit is a dynamic random access memory (DRAM) and the first and second redundant elements, and the primary element are memory elements.

3. The method of claim 1 wherein the step of programming a first redundant element comprises the step of selectively blowing a fuse circuit in a fuse bank enable circuit.

4. The method of claim 1 wherein the step of permanently disabling the first redundant element comprises the step of selectively blowing a fuse circuit in a cancel fuse circuit.