Electrically programmable fuse bit
View Patent ↗One-time programmable (OTP) nonvolatile fuse memory cells are disclosed that do not require decoding or addressing for reading their data content. Each fuse memory cell has its content latched at its output and available at all times and can be used, for example, for code storage memories, serial configuration memories, and as individual fuse bits for ID (identification), trimming, and other post-fabrication System-on-Chip (SoC) customization needs.
1. A nonvolatile programmable read only memory cell with continuously available data content without decoding or addressing, the memory cell comprising:
a select transistor having a source, a drain, and a gate, wherein the source or the drain of the select transistor is connected to a first voltage and the other of the source and the drain forms a first connection point; and
a fuse transistor having a source, a drain, and a gate, wherein:
the source, the drain, or the source and the drain of the fuse transistor forms a second connection point, wherein the second connection point is an output port of the memory cell;
the first and the second connection points are electrically connected; and
data of certain logic level is programmed in the cell through permanently altering at least one physical characteristic of the fuse transistor by turning on the select transistor and applying a controlled high voltage to the gate of the fuse transistor for a predetermined period of time, wherein in CMOS implementation of the memory cell, the fuse and the select transistors are “Native.”
2. The memory cell of claim 1 , wherein the first and the second connection points are connected together through at least one high-voltage-protection transistor having a source, a drain, and a gate, and wherein the source or the drain of the high-voltage-protection transistor is connected to the first connection point and the other of the source and the drain of the high-voltage-protection transistor is connected to the second connection point.
3. The memory cell of claim 1 , wherein the memory cell implemented using CMOS processes.
4. The memory cell of claim 1 , wherein the memory cell data is verified by applying a voltage to the gate of the fuse transistor which is lower than the programming voltage.
5. The memory cell of claim 1 , wherein altering at least one physical characteristic of the transistor is achieved by breaking down dielectric or gate oxide of the fuse transistor.
6. The memory cell of claim 1 wherein transistors are NMOS transistors.
7. The memory cell of claim 1 wherein transistors are PMOS transistors.
8. A nonvolatile programmable read only memory cell with continuously available data content without decoding or addressing, the memory cell comprising:
a select transistor having a source, a drain, and a gate, wherein the source or the drain of the select transistor is connected to a first voltage and the other of the source and the drain forms a first connection point; and
a fuse transistor having a source, a drain, and a gate, wherein:
the source, the drain, or the source and the drain of the fuse transistor forms a second connection point, wherein the second connection point is an output port of the memory cell;
the first and the second connection points are electrically connected; and
data of certain logic level is programmed in the cell through permanently altering at least one physical characteristic of the fuse transistor by turning on the select transistor and applying a controlled high voltage to the gate of the fuse transistor for a predetermined period of time, wherein in a CMOS implementation of the memory cell, N-type well implants are co-implanted with the N+ Source/Drain implant creating a graded junction due to the presence of the NWELL implant.