Multiple-bit electrical fuses
View Patent ↗A method for forming a semiconductor device includes forming a nanosheet stack comprising alternating layers of a first material and a second material on a substrate. The method further includes removing portions of the stack to form tapered stack sidewalls, which have a taper angle in relation to a horizontal surface of the substrate. The method further includes converting the second material to a resistive material. The layers that include the resistive material form one or more electrical fuses.
1. A semiconductor device comprising:
a nanosheet stack on a semiconductor substrate, the nanosheet stack comprising tapered sidewalls formed on a substrate, the nanosheet structure further comprising a first electrical fuse vertically stacked on a second electrical fuse, wherein a length of the first electrical fuse is less than a length of the second electrical fuse to define a multiple-bit fuse;
a common anode and cathode shared by the first and second electrical fuses;
a dielectric material isolating the first and second electrical fuses; and
a pair of conductor contacts electrically connected to the anode and cathode,
wherein the tapered sidewalls have a taper angle in relation to a horizontal surface of the substrate, and wherein the taper angle extends inward from the semiconductor substrate toward an upper surface of the nanosheet stack.
2. The semiconductor device of claim 1 , wherein the at least one electrical fuse includes a plurality of electrical fuses.
3. The semiconductor device of claim 2 , wherein the plurality of electrical fuses defines two or more nanosheet layers comprising a second material.
4. The semiconductor device of claim 3 , wherein each nanosheet layer forms a separate electrical fuse.
5. The semiconductor device of claim 4 , wherein each electrical fuse is configured to operate as a memory storage device.
6. The semiconductor device of claim 5 , wherein the tapered sidewalls form electrical fuses of predetermined variable lengths.
7. The semiconductor device of claim 6 , wherein the variable lengths define variable resistances.
8. The semiconductor device of claim 1 , wherein the taper angle sets a different breakdown voltage for each electrical fuse among the one or more electrical fuses, and wherein each electrical fuse is programmed by applying the breakdown voltage.
9. The semiconductor device of claim 6 , wherein the plurality of electrical fuses define a combined resistive value based on the variable lengths of each electrical fuse being arranged in parallel to each other.
10. The semiconductor device of claim 6 , wherein the variable lengths create different combined resistances.
11. The semiconductor device of claim 10 , wherein the combined resistance increases from an upper surface of the nanosheet layers stack to the substrate.
12. The semiconductor device of claim 10 , wherein a length of each electrical fuse defines a breakdown voltage.
13. The semiconductor device of claim 11 , wherein each electrical fuses has a different breakdown voltage with respect to one another.
14. The semiconductor device of claim 10 , wherein the breakdown voltages increase from an upper surface of the nanosheet layers stack to the substrate.
15. The semiconductor device of claim 1 , wherein the at least one electric fuse is covered with an opaque material.
16. The semiconductor device of claim 15 , wherein the opaque material inhibits reverse engineering of the at least one electric fuses resistant.
17. The semiconductor device of claim 1 , wherein the electrical fuses are configured to store bits of information.
18. The semiconductor device of claim 17 , wherein the bits of information are stored based on a state of each electrical fuse.
19. The semiconductor device of claim 18 , wherein the state is one of a closed state or an open state.
20. The semiconductor device of claim 19 , wherein each electrical fuse transitions from the closed state to the open state when an applied voltage exceeds the breakdown voltage.