REGULATING ELECTRICAL FUSE PROGRAMMING CURRENT

• US 20100014373A1
• Filed: 07/21/2008
• Published: 01/21/2010
• Est. Priority Date: 07/21/2008
• Status: Active Grant

• Current Assignee: GlobalFoundries, Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: Anand, Darren L., Goss, John R., Fifield, John A.
• Granted Patent: US 7,911,820 B2
• Time in Patent Office: Days
• US Class Current: 365/225.700
• 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

An apparatus for regulating eFUSE programming current includes a current control generator receiving an input reference current through a first current path of reference fuses, the input reference current proportional to a desired eFUSE programming current; a second current path including a reference programming FET and a second group of reference fuses; and a voltage comparator coupled to a gate terminal of the reference programming FET so as to adjust the gate voltage of the reference programming FET to equalize a first voltage across the first current path with a second voltage across the second current path. The gate voltage of the reference programming FET is an output of the current control generator, coupled to corresponding gates of one or more selected programming devices of an eFUSE array such that the selected programming devices source the desired eFUSE programming current to a selected eFUSE to be programmed.

Claims

1. An apparatus for regulating electrical fuse (eFUSE) programming current in semiconductor devices, comprising:

a current control generator configured to receive an input reference current through a first current path that includes a first group of reference fuses, the input reference current proportional to a desired eFUSE programming current;

a second current path associated with the current control generator, the second current path including a reference programming FET and a second group of reference fuses; and

a voltage comparator associated with the current control generator, with an output of the voltage comparator coupled to a gate terminal of the reference programming FET so as to adjust the gate voltage of the reference programming FET to equalize a first voltage across the first current path with a second voltage across the second current path;

wherein the gate voltage of the reference programming FET is an output of the current control generator, coupled to corresponding gates of one or more selected programming devices of an eFUSE array such that each of the one or more selected programming devices sources the desired eFUSE programming current to a selected eFUSE to be programmed.

2. The apparatus of claim 1, wherein the magnitude of the reference current is a scaled down factor with respect to the desired programming current so as to prevent programming of the first group of reference fuses.

3. The apparatus of claim 1, wherein the reference programming FET and each of the programming devices of the eFUSE array comprise PFET devices having source terminals thereof are coupled to a programming voltage that is higher than a nominal V_DD logic high supply rail voltage.

4. The apparatus of claim 3, further comprising a current control block associated with each column of the eFUSE array, the current control block configured to selectively pass the gate voltage of the reference programming PFET to the gate of the corresponding programming PFET device of the eFUSE array.

5. The apparatus of claim 4, wherein the current control block further comprises:

an NFET/PFET pass gate pair having an input node coupled to the gate of the reference programming PFET and an output node coupled to the gate of the corresponding programming PFET device of the eFUSE array;

a gate terminal of the NFET of the NFET/PFET pass gate pair coupled to a column select signal, and a gate terminal of the PFET of the NFET/PFET pass gate pair coupled to an inverted value of the column select signal;

a pull up PFET device having a gate terminal coupled to the column select signal, a source terminal coupled to the programming voltage, and a drain terminal coupled to the gate of the programming PFET device of the eFUSE array;

wherein the NFET/PFET pass gate pair is deactivated whenever the column select signal is not asserted so as to prevent coupling of the gate voltage of the reference programming PFET to the gate of the programming PFET device of the eFUSE array, and wherein the pull up PFET device is activated whenever the column select signal is not asserted so as to maintain the programming PFET device of the eFUSE array in a nonconductive state; and

wherein the NFET/PFET pass gate pair is activated whenever the column select signal is asserted so as to pass the gate voltage of the reference programming PFET to the gate of the programming PFET device of the eFUSE array.

6. The apparatus of claim 5, wherein the voltage of the column select signal in the asserted state is substantially equal to the programming voltage.

7. The apparatus of claim 2, wherein the first and second current paths each include an NFET having a conductive strength that is scaled with respect to corresponding NFETS included in programming paths of each of the eFUSEs.

8. An electrical fuse (eFUSE) array with programming current control, comprising:

a plurality of bitlines arranged in columns;

a plurality of bitcells associated with each bitline, each bitcell comprising an eFUSE device coupled to the associated bitline and a programming NFET in series with the eFUSE device, with each programming NFET controlled by one of a plurality of row select control signals;

a current control generator configured to receive an input reference current through a first current path that includes a first group of reference fuses, the input reference current proportional to a desired eFUSE programming current;

a second current path associated with the current control generator, the second current path including a reference programming PFET and a second group of reference fuses; and

a voltage comparator associated with the current control generator, with an output of the voltage comparator coupled to a gate terminal of the reference programming PFET so as to adjust the gate voltage of the reference programming PFET to equalize a first voltage across the first current path with a second voltage across the second current path;

wherein the gate voltage of the reference programming PFET is an output of the current control generator, coupled to corresponding gates of programming PFET devices associated with each bitline such that each of the one or more selected programming devices sources the desired eFUSE programming current to a selected eFUSE to be programmed.

9. The eFUSE array of claim 8, wherein the magnitude of the reference current is a scaled down factor with respect to the desired programming current so as to prevent programming of the first group of reference fuses.

10. The eFUSE array of claim 8, wherein the source terminals of the reference programming PFET and the programming PFET devices associated with each bitline are coupled to a programming voltage that is higher than a nominal V_DD logic high supply rail voltage.

11. The eFUSE array of claim 10, further comprising a current control block associated with each bitline, the current control block configured to selectively pass the gate voltage of the reference programming PFET to the gate of the corresponding programming PFET device of a selected bitcell coupled to the bitline.

12. The eFUSE array of claim 11, wherein the current control block further comprises:

an NFET/PFET pass gate pair having an input node coupled to the gate of the reference programming PFET and an output node coupled to the gate of the corresponding programming PFET device of the eFUSE array;

a gate terminal of the NFET of the NFET/PFET pass gate pair coupled to a column select signal, and a gate terminal of the PFET of the NFET/PFET pass gate pair coupled to an inverted value of the column select signal;

a pull up PFET device having a gate terminal coupled to the column select signal, a source terminal coupled to the programming voltage, and a drain terminal coupled to the gate of the programming PFET device of the eFUSE array;

wherein the NFET/PFET pass gate pair is deactivated whenever the column select signal is not asserted so as to prevent coupling of the gate voltage of the reference programming PFET to the gate of the programming PFET device of the eFUSE array, and wherein the pull up PFET device is activated whenever the column select signal is not asserted so as to maintain the programming PFET device of the eFUSE array in a nonconductive state; and

wherein the NFET/PFET pass gate pair is activated whenever the column select signal is asserted so as to pass the gate voltage of the reference programming PFET to the gate of the programming PFET device of the associated bitline.

13. The eFUSE array of claim 12, wherein the voltage of the column select signal in the asserted state is substantially equal to the programming voltage.

14. The eFUSE array of claim 9, wherein the first and second current paths each include an NFET having a conductive strength that is scaled with respect to corresponding NFETs included in each bitcell.

15. A method for regulating electrical fuse (eFUSE) programming current in semiconductor devices, the method comprising:

configuring a current control generator to receive an input reference current through a first current path that includes a first group of reference fuses, the input reference current proportional to a desired eFUSE programming current;

configuring a second current path associated with the current control generator, the second current path including a reference programming FET and a second group of reference fuses; and

configuring a voltage comparator associated with the current control generator, with an output of the voltage comparator coupled to a gate terminal of the reference programming FET so as to adjust the gate voltage of the reference programming FET to equalize a first voltage across the first current path with a second voltage across the second current path;

wherein the gate voltage of the reference programming FET is an output of the current control generator, coupled to corresponding gates of one or more selected programming devices of an eFUSE array such that each of the one or more selected programming devices sources the desired eFUSE programming current to a selected eFUSE to be programmed.

16. The method of claim 15, wherein the magnitude of the reference current is a scaled down factor with respect to the desired programming current so as to prevent programming of the first group of reference fuses.

17. The method of claim 15, wherein the reference programming FET and each of the programming devices of the eFUSE array comprise PFET devices having source terminals thereof are coupled to a programming voltage that is higher than a nominal V_DD logic high supply rail voltage.

18. The apparatus of claim 17, further comprising configuring a current control block associated with each column of the eFUSE array, the current control block configured to selectively pass the gate voltage of the reference programming PFET to the gate of the corresponding programming PFET device of the eFUSE array, wherein configuring the current control block further comprises:

coupling an NFET/PFET pass gate pair having an input node to the gate of the reference programming PFET and coupling an output node to the gate of the corresponding programming PFET device of the eFUSE array;

coupling a gate terminal of the NFET of the NFET/PFET pass gate pair to a column select signal, and coupling a gate terminal of the PFET of the NFET/PFET pass gate pair to an inverted value of the column select signal;

coupling a pull up PFET device having a gate terminal to the column select signal, coupling a source terminal coupled to the programming voltage, and coupling a drain terminal to the gate of the programming PFET device of the eFUSE array;

wherein the NFET/PFET pass gate pair is deactivated whenever the column select signal is not asserted so as to prevent coupling of the gate voltage of the reference programming PFET to the gate of the programming PFET device of the eFUSE array, and wherein the pull up PFET device is activated whenever the column select signal is not asserted so as to maintain the programming PFET device of the eFUSE array in a nonconductive state; and

wherein the NFET/PFET pass gate pair is activated whenever the column select signal is asserted so as to pass the gate voltage of the reference programming PFET to the gate of the programming PFET device of the eFUSE array.

19. The method of claim 18, wherein the voltage of the column select signal in the asserted state is substantially equal to the programming voltage.

20. The apparatus of claim 16, wherein the first and second current paths each include an NFET having a conductive strength that is scaled with respect to corresponding NFETS included in programming paths of each of the eFUSEs.