Electrically programmable interlevel fusible link for integrated circuits

An integrated circuit comprising:

• a first conductive layer disposed on a first level of the integrated circuit;
• a second conductive layer;
• an interlevel programmable interconnect disposed between the first conductive layer and the second conductive layer and, in a nonprogrammed state, having a generally uniform cross-sectional area, the programmable interconnect having the cross-sectional area for developing a current density within the programmable interconnect from a programming current to place the programmable interconnect in a programmed state and isolate the first conductive layer from the second conductive layer, and the programmable interconnect having the cross-sectional area for developing a long-term, reliable current density from a read current when the programmable interconnect, in a nonprogrammed state, conducts a nonprogramming current;
• wherein when the first conductive layer and the second conductive layer conduct the programming current, the first conductive layer and second conductive layer respectively develop current densities which support long-term, reliable operation;
• and
• a read/write circuit, coupled to the programmable interconnect, for supplying the programming current and the read current, wherein the read/write circuit includes a switch to couple the second conductor to an output node during a read operation, and, if the programmable interconnect is in the nonprogrammed state, a read current flows from the voltage node through the programmable interconnect to the output node, wherein the read current does not exceed a long-term, reliable current density.

An electronic system including a microprocessor, a memory, and a system bus, and further including a semiconductor device fabricated in accordance with a process comprising:

• forming a first conductor of an integrated circuit;
• forming an isolation layer over the first conductor;
• forming an opening through the isolation layer to the first conductor;
• filling the opening with a fusible material to form a programmable interlevel interconnection capable of developing a destructive programming current density within the fusible material from a programming current;
• and
• forming a second conductor over the isolation layer to connect to the fusible material filling the opening;
• forming at least one via to couple a current to the programmable interlevel interconnection, wherein all or only a portion of the current flows through the via;
• wherein the semiconductor device further includes a read/write circuit including a switch to couple the second conductor to an output node during a read operation, and, if the programmable interlevel interconnection is in the nonprogrammed state, a read current flows from the voltage node through the programmable interlevel interconnection to the output node, wherein the read current does not exceed a long-term, reliable current density in the via and the programmable interlevel interconnection.

An integrated circuit comprising:

• a first conductive layer and at least a second conductive layer;
• an insulation layer between and separating the first and second conductive layers;
• a first via formed between the first and second conductive layers, the first via having a first area in plan view and containing a conductive material thereby to allow a current to flow between the first and second conductive layers;
• a second via coupled to one of the first and second conductive layers, the second via having a second area in plan view substantially less than the first area, the second area being such as to cause the current density in the second via in response to the application of a given current through the second via to exceed the current density at which the conductive material in the second via will open circuit while the same current through the first via will not cause the first via to open circuit;
• and
• a read/write circuit, coupled to the first via and the second via, to supply a programming current from a voltage node through the first via and the second via during a programming operation, the read/write circuit including a switch to couple the second conductive area to an output node during a read operation, and, if the second via is in the nonprogrammed state, a read current flows from the voltage node through the second via to the output node, wherein the read current does not exceed a long-term, reliable current density in the first via and the second via.