Antifuse programming current limiter

• US 6,545,928 B1
• Filed: 09/25/2001
• Issued: 04/08/2003
• Est. Priority Date: 09/25/2001
• Status: Active Grant

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Bell, Debra M.
• Primary Examiner(s): Nelms, David
• Assistant Examiner(s): HO, TU TU V
• Application Number:
  US09/964,110
• Publication Number:
  US 20030058725A1
• Time in Patent Office: 560 Days
• Field of Search: 365/225.7, 365/200, 365/96
• US Class Current: 365/225.7
• CPC Class Codes: G11C 17/16 using electrically-fusible links
• CPC Class Codes: G11C 17/18 Auxiliary circuits, e.g. for writing into memory

Abstract

Methods for enhancing the programming of antifuses are discussed. The methods include accessing an antifuse in an antifuse bank by providing an address, raising a signal source to a high voltage level for programming the antifuse, sensing current flowing through the antifuse, and inhibiting current from flowing through the antifuse without having to delay by a programmed time period when the current is sensed by the act of sensing. The act of inhibiting continues to inhibit current from flowing until another address is provided. The methods also include accessing antifuses in multiple banks and programming them simultaneously.

Claims

1. An antifuse bank, comprising:

a signal source for providing a high voltage level for programming the antifuse bank;

at least one antifuse having a dielectric interposed between two electrodes;

at least one selector to select the at least one antifuse corresponding to an address;

a current sensor having a sense terminal coupled to one electrode of the at least one antifuse and further having an enable terminal, the current sensor providing an active enable signal in response to sensing a current at the sense terminal exceeding a current threshold; and

a current limiter having a first connection coupled to the signal source, a second connection coupled to the enable terminal, and a third connection coupled to the at least one selector, the current limiter allowing current to be inhibited from flowing through the at least one antifuse in response to an active enable signal.

2. The antifuse bank of claim 1, wherein the signal source has two states, one of the two states includes a low voltage level, and the other of the two states includes the high voltage level that is asserted for programming the antifuse bank.

3. The antifuse bank of claim 1, wherein the two electrodes are electrically coupled when the at least one antifuse is programmed by the high voltage level of the voltage source.

4. The antifuse bank of claim 1, wherein each selector has a first input electrode to receive a column address and a second input electrode to receive a row address.

5. The antifuse bank of claim 4, wherein when the column address is high and when the row address is low, a complete circuit path is formed from the voltage source to ground so that the at least one antifuse is programmed.

6. A computer system, comprising:

a processor;

a memory system that comprises a plurality of memory modules, one of the plurality of the memory modules comprises a plurality of memory devices;

a plurality of command links coupled to the plurality of memory devices to communicate at least one command signal;

a plurality of data links coupled to the plurality of memory devices to communicate data;

a memory controller;

at least one user interface device, wherein the at least one user interface device includes a monitor;

at least one output device, wherein the at least one output device includes a printer;

at least one bulk storage device, wherein at least one memory device of the plurality of memory devices includes an antifuse bank comprising;

a signal source having a high voltage level for programming the antifuse bank;

at least one antifuse having a dielectric interposed between two electrodes;

at least one selector to select the at least one antifuse corresponding to an address;

a current sensor having a sense terminal coupled to one electrode of the at least one antifuse and further having an enable terminal, the current sensor providing an active enable signal in response to sensing a current at the sense terminal exceeding a current threshold; and

a current limiter having a first terminal coupled to the signal source, a second terminal coupled to the enable terminal, and a third terminal coupled to the at least one selector, in response to an active enable signal, the current limiter inhibiting current from flowing through the at least one antifuse until the at least one access circuit receives another address, without having to delay by a delay circuit for a programmed time period.

7. A method for programming an antifuse bank, comprising:

accessing the antifuse bank by providing a row address and a column address;

raising a signal source to a high voltage level for programming the antifuse bank;

programming an antifuse by coupling the antifuse to the signal source; and

inhibiting current from flowing through the antifuse without delaying by a programmed time period and sensing current flowing through the antifuse before the act of inhibiting is executed.

8. The method of claim 7, wherein accessing the antifuse bank includes providing a column address, wherein the column address addresses the antifuse as well as other antifuses within the antifuse bank.

9. The method of claim 7, wherein programming the antifuse includes breaking a dielectric between two terminals of the antifuse so that the two terminals are electrically shorted to conduct current from the voltage source.

10. The method of claim 7, wherein accessing the antifuse bank includes providing a row address, wherein the row address addresses the antifuse bank as well as other antifuse banks.

11. An antifuse bank, comprising:

a signal source having a high voltage level for programming the antifuse bank;

at least one antifuse having a dielectric interposed between two electrodes;

at least one current sensor having one terminal coupled to the signal source and another terminal coupled to the at least one antifuse;

at least one selector to select the at least one antifuse corresponding to an address;

at least one switch having a first electrode coupled to the at least one antifuse, a second electrode coupled to the at least one selector, and a third electrode; and

an inhibitor coupled to the third electrode of the at least one switch, the inhibitor inhibiting current from flowing through the at least one antifuse by opening the at least one switch without having to delay by a programmed time period.

12. The antifuse bank of claim 11, wherein the at least one current sensor includes only one current sensor.

13. The antifuse bank of claim 11, wherein the at least one current sensor includes at least two current sensors.

14. The antifuse bank of claim 11, wherein the at least one switch includes an n-channel transistor having a gate, source, and drain, the gate coupled to the inhibitor, the drain coupled to the antifuse, and the source coupled to the at least one selector.

15. The antifuse bank of claim 11, wherein the at least one selector includes an n-channel transistor having a gate, source, and drain, the gate coupled to the column address, the drain coupled to the second electrode of the at least one switch, and the source coupled to the row address.

16. A method for programming an antifuse bank, comprising:

accessing an antifuse by providing an address;

raising a signal source to a high voltage level for programming the antifuse;

sensing current flowing through the antifuse; and

inhibiting current from flowing through the antifuse without delaying by a delaying circuitry when the current is sensed by the act of sensing, wherein the act of inhibiting continues to inhibit current from flowing until reading of the programmed state of the antifuse is desired, or accessing another fuse in the bank is desired.

17. The method of claim 16, wherein sensing includes sensing by only one current sensor.

18. The method of claim 16, wherein sensing includes sensing by at least two current sensors.

19. The method of claim 16, wherein inhibiting includes switching a switch to open a conductive path so that current is inhibited from flowing through the antifuse.

20. The method of claim 16, wherein inhibiting includes switching a switch to close a conductive path for programming or reading the antifuse.

21. A method for limiting current through an antifuse, comprising:

closing a switch that couples the antifuse to a selector;

selecting the antifuse for programming by providing an address to the selector;

detecting a voltage from sensing current flowing through the antifuse;

generating an enabled signal when the act of detecting detects the voltage; and

inhibiting current from flowing through the antifuse when the enabled signal is generated by opening the switch until the address is changed or reading the fuse is desired.

22. The method of claim 21, wherein selecting includes providing an address to the access circuit to close an access switch so as to create a conductive path for current to flow to program the antifuse.

23. The method of claim 21, further comprising closing the switch while opening another switch after the antifuse is programmed.

24. The method of claim 21, wherein the act of detecting a voltage is executed only during the programming of an antifuse.

25. The method of claim 21, wherein the method does not proceed in the order presented.

26. A circuit for enhancing programming of an antifuse bank which includes multiple antifuses, each antifuse having a dielectric between two electrodes, the circuit comprising:

a signal source for programming an antifuse;

at least one resistor having a lead coupled to the voltage source, and another lead coupled to one of the two electrodes of the antifuse to define a node;

at least one switching transistor having a gate, a source, and a drain coupled to the other of the two electrodes of the antifuse; and

a latch having a complementary output coupled to the gate of the at least one switching transistor and providing a control signal out of the complementary output to control the at least one switching transistor, the latch transitioning the control signal to reverse-bias the at least one switching transistor when sufficient current flows across the at least one resistor, the latch transitioning the control signal to forward-bias the at least one switching transistor when inhibiting current is no longer desired.

27. The circuit of claim 26, further comprising a comparator having an output, a positive input coupled to the voltage source, and a negative input coupled to the node.

28. The circuit of claim 27, further comprising a p-channel transistor having a gate coupled to the output of the comparator, a source coupled to a supply voltage, and a drain coupled to the latch.

29. The circuit of claim 28, wherein the latch includes a reset input port for receiving a DQ signal.

30. The circuit of claim 29, further comprising an access transistor having a drain coupled to the source of the switching transistor, a gate coupled to a complementary of the DQ signal, and a source coupled to a column address.

31. A method for enhancing programming of an antifuse bank which includes a set of antifuses, each antifuse having a dielectric between two electrodes, the method comprising:

providing a signal source for programming an antifuse;

sensing current by at least one resistor having a lead coupled to the voltage source, and another lead coupled to one of the two electrodes of the antifuse to define a node;

switching by at least one switching transistor having a gate, a source, and a drain, wherein the drain of the at least one switching transistor is coupled to the other of the two electrodes of the antifuse; and

latching by a latch having a complementary output coupled to the gate of the at least one switching transistor and providing a control signal out of the complementary output to control the at least one switching transistor, the latch transitioning the control signal to reverse-bias the at least one switching transistor when current flows across the at least one resistor, the latch transitioning the control signal to forward-bias the at least one switching transistor when inhibiting current is no longer desired.

32. The method of claim 31, further comprising comparing by a comparator having an output, a positive input coupled to the voltage source, and a negative input coupled to the node.

33. The method of claim 32, further comprising enabling the latch by a p-channel transistor having a gate coupled to the output of the comparator, a source coupled to a supply voltage, and a drain coupled to the latch.

34. The method of claim 33, further comprising resetting the latch by inputting a DQ signal into a reset input port of the latch.

35. The method of claim 34, further comprising an access transistor having a drain coupled to the source of the switching transistor, a gate coupled to a complementary of the DQ signal, and source coupled to a column address.

36. A number of antifuse banks, each antifuse bank comprising:

a signal source for programming the number of antifuse banks;

a plurality of antifuses in each antifuse bank, the plurality of antifuses coupled to the signal source, the plurality of antifuses adapted to be accessed by a plurality of row addresses and one column address;

a current sensor coupled to each antifuse bank for generating an enable signal in response to sensing a current exceeding a current threshold; and

a current limiter coupled to the plurality of antifuses for inhibiting current from flowing through the plurality of antifuses in response to the enable signal without having to delay by a programmed time period.

37. The number of antifuse banks of claim 36, wherein a fuse in each bank can be programmed simultaneously.

38. The number of antifuse banks of claim 36, wherein the current limiter includes an inhibitor circuit that decouples the plurality of antifuses from ground so as to inhibit current from flowing.

39. The number of antifuse banks of claim 38, wherein the current limiter includes a latch that is set when current flows across one of the at least four antifuses.

40. The number of antifuse banks of claim 39, wherein the latch is reset when the one column address is changed.