Scaled-down phase change memory cell in recessed heater

An integrated circuit including at least one semiconductor structure, the at least one semiconductor structure comprising:

• a first electrode;
• an insulating layer formed on at least a portion of an upper surface of the first electrode;
• a pillar traversing the insulating layer and being recessed relative to an upper surface of the insulating layer, the pillar comprising a heater formed on at least a portion of the upper surface of the first electrode and a collar formed on sidewalls of the insulating layer proximate the heater and on at least a portion of an upper surface of the heater, wherein the heater is formed of carbon or titanium nitride or tantalum nitride, and wherein the heater has a width that is less than a width of the first electrode;
• a phase change material layer formed on at least a portion of the upper surface of the insulating layer and filling a volume defined by the upper surface of the heater and an upper surface of the collar, at least a portion of the phase change material being in physical contact with the carbon or titanium nitride or tantalum nitride material forming the upper surface of the heater;
• and
• at least a second electrode farmed on at least a portion of an upper surface of the phase change material layer,
• wherein the collar is configured so as to concentrate a flow of current from the phase change material layer formed on the upper surface of the insulating layer to within the phase change material filling said defined volume and cause a state transition of substantially all of the phase change material filling said defined volume due to localized heating, when a switching current signal is applied between the first and second electrodes.

A memory circuit, comprising:

• a plurality of nonvolatile memory cells;
• and
• a plurality of bit lines and word lines operatively coupled to the memory cells for selectively accessing one or more of the memory cells;
• wherein at least a given one of the memory cells comprises:
• a first electrode;
• an insulating layer formed on at least a portion of an upper surface of the first electrode;
• a pillar traversing the insulating layer and being recessed relative to an upper surface of the insulating layer, the pillar comprising as heater farmed on at least a portion of the upper surface of the first electrode and a collar formed on sidewalls of the insulating layer proximate the heater and on at least a portion of an upper surface of the heater, a lower surface of the collar being formed entirely on the at least a portion of the upper surface of the heater, wherein the heater is formed of carbon or titanium nitride or tantalum nitride, and wherein the heater has a width that is less than a width of the first electrode;
• a phase change material layer formed on at least as portion of the upper surface of the insulating layer and filling a volume defined by the upper surface of the heater and an upper surface of the collar, at least a portion of the phase change material being in physical contact with the carbon or titanium nitride or tantalum nitride material forming the upper surface of the heater and the upper surface of the collar;
• and
• at least a second electrode formed on at least a portion of an upper surface of the phase change material layer,
• wherein the collar is configured so as to concentrate a flow of current from the phase change material layer finned on the upper surface of the insulating layer to within the phase change material filling said defined volume and cause a state transition of substantially all of the phase change material tilling said defined volume due to localized heating, when a switching current signal is applied between the first and second electrodes.

A method of forming a semiconductor structure configurable for use as a nonvolatile storage element, the method comprising the steps of:

• forming a first electrode;
• forming an insulating layer on at least a portion of an upper surface of the first electrode;
• forming a pillar traversing the insulating layer and being recessed relative to an upper surface of the insulating layer, the pillar comprising a heater formed on at least a portion of the upper surface of the first electrode and a collar formed on sidewalls of the insulating layer proximate the heater and on at least a portion of an upper surface of the heater, a lower surface of the collar being formed entirely on the at least a portion of the upper surface of the heater, wherein the beater is formed of carbon or titanium nitride or tantalum nitride, and wherein the heater has a width that is less than a width of the first electrode;
• forming a phase change material layer on at least a portion of the upper surface of the insulating layer and filling a volume defined by the upper surface of the heater and an upper surface of the collar, at least a portion of the phase change material being in physical contact with the carbon or titanium nitride or tantalum nitride material forming the upper surface of the heater and the upper surface of the collar;
• and
• forming at least a second electrode on at least a portion of an upper surface of the phase change material layer,
• wherein the collar is configured so as to concentrate a flow of current from the phase change material layer formed on the upper surface of the insulating layer to within the phase change material filling said defined volume and cause a state transition of substantially all of the phase change material tilling said defined volume due to localized heating, when a switching current signal is applied between the first and second electrodes.