Integrated circuit fuse array
The fuse array described herein is very compact and uses little semiconductor area because of its crosspoint architecture. The disclosed crosspoint architecture reduces the number of conductors that must be run horizontally or vertically through each bit cell. As a result, the area required for each bit cell is significantly reduced. In one embodiment, a selected set of voltages on various wordlines and bitlines are used to program the fuses to produce programmed fuses having a tighter distribution of impedances. Similarly, a selected set of voltages on various wordlines and bitlines are used to read the fuses.
1. A method for programming a first fuse, the method comprising:
providing a plurality of fuses arranged in an array, the array comprising a plurality of fuse wordlines and bitlines, wherein the plurality of fuses comprise the first fuse;
providing a first voltage to a selected wordline;
providing a second voltage to a non-selected wordline, wherein a magnitude of the second voltage is greater than a magnitude of the first voltage; and
providing a third voltage to a selected bitline, wherein a magnitude of the third voltage is greater than the magnitude of the second voltage; and
wherein the first fuse is programmed in response to the steps of providing the first, second, and third voltages.
2. A method as in claim 1 , wherein the first fuse is electrically programmable.
3. A method as in claim 1 , wherein a second fuse is coupled to the selected bitline and the non-selected wordline, and wherein the second fuse remains unprogrammed in response to the steps of providing the second and third voltages.
4. A method as in claim 3 , further comprising:
providing a fourth voltage to a non-selected bitline, wherein a magnitude of the fourth voltage is approximately equal to the magnitude of the first voltage.
5. A method as in claim 4 , wherein a third fuse is coupled to the non-selected bitline and the non-selected wordline, and wherein the third fuse remains unprogrammed in response to the steps of providing the second and fourth voltages.
6. A method as in claim 5 , wherein a fourth fuse is coupled to the non-selected bitline and the selected wordline, and wherein the fourth fuse remains unprogrammed in response to the steps of providing the first and fourth voltages.
7. A method as in claim 1 , wherein the first voltage is approximately equal to a first power supply voltage, the second voltage is approximately equal to a second power supply voltage.
8. A method as in claim 7 , wherein the magnitude of the third voltage is greater than twice a magnitude of the second power supply voltage.
9. A method as in claim 1 , wherein a transistor coupled to the selected bitline and the non-selected wordline is back biased in response to the steps of providing the first, second, and third voltages.
10. A method for reading a first fuse, the method comprising:
providing a plurality of fuses arranged in an array, the array comprising a plurality of fuse wordlines and bitlines, wherein the plurality of fuses comprise the first fuse;
providing a first voltage to a selected wordline;
providing a second voltage to a non-selected wordline, wherein a magnitude of the second voltage is greater than a magnitude of the first voltage; and
providing a third voltage to a selected bitline, wherein a magnitude of the third voltage is approximately equal to the magnitude of the second voltage; and
reading the first fuse in response to the steps of providing the first, second, and third voltages.
11. A method as in claim 10 , wherein the first fuse is electrically programmable.
12. A method as in claim 10 , wherein the step of reading comprises comparing a current on the selected bitline and a plurality of currents on a plurality of non-selected bitlines.
13. A method as in claim 10 , wherein a second fuse is coupled to the selected bitline and the non-selected wordline, and wherein the second fuse remains unread in response to the steps of providing the second and third voltages.
14. A method as in claim 13 , wherein reading the first fuse does not program the second fuse.
15. A method as in claim 13 , further comprising:
providing a fourth voltage to a non-selected bitline, wherein a magnitude of the fourth voltage is approximately equal to the magnitude of the first voltage.
16. A method as in claim 15 , wherein a third fuse is coupled to the non-selected bitline and the non-selected wordline, and wherein the third fuse remains unread in response to the steps of providing the second and fourth voltages.
17. A method as in claim 16 , wherein a fourth fuse is coupled to the non-selected bitline and the selected wordline, and wherein the fourth fuse remains unread in response to the steps of providing the first and fourth voltages.
18. A method as in claim 17 , wherein reading the first fuse does not program the second, third, and fourth fuses.
19. A method for accessing a first fuse, the method comprising:
providing a plurality of fuses arranged in an array, the array comprising a plurality of fuse wordlines and bitlines, wherein the plurality of fuses comprise the first fuse;
providing a first voltage to a selected wordline;
providing a second voltage to a non-selected wordline, wherein a magnitude of the second voltage is greater than a magnitude of the first voltage; and
providing a third voltage to a selected bitline, wherein a magnitude of the third voltage is greater than or approximately equal to the magnitude of the second voltage.
20. A method as in claim 19 , further comprising:
providing an address corresponding to the first fuse;
using the address to select the selected wordline; and
using the address to select the selected bitline.