Phase change memory using multiple stacks of PCM materials
AssigneeInternational Business Machines Corporation
InventorsTian Shen, Heng Wu, Kevin W. Brew, Jingyun Zhang
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Abstract
A method is presented for improved linearity of a phase change memory (PCM) cell structure. The method includes forming a bottom electrode over a substrate, constructing a PCM stack including a plurality of PCM layers each having a different crystallization temperature over the bottom electrode, and forming a top electrode over the PCM stack. The crystallization temperature varies in an ascending order from the bottom electrode to the top electrode.
Claims13
A method for improved linearity of a phase change memory (PCM) cell structure, the method comprising:
- forming a bottom electrode over a substrate;
- forming a heating element in direct contact with a top surface of the bottom electrode;
- forming a resistive liner defining a planar surface across its entire length, such that the planar resistive liner surface extends, in its entirety, above a top surface of the heating element;
- constructing a PCM stack including a plurality of PCM layers each having a different crystallization temperature over the bottom electrode, the PCM stack directly contacting a top surface of the resistive liner;
- and
- forming a top electrode over the PCM stack,
- wherein the crystallization temperature varies in an ascending order from the bottom electrode to the top electrode.
A semiconductor structure comprising:
- a bottom electrode disposed over a substrate;
- a heating element disposed in direct contact with a top surface of the bottom electrode;
- a resistive liner defining a planar surface across its entire length, such that the planar resistive liner surface extends, in its entirety, above a top surface of the heating element;
- a phase change memory (PCM) stack including a plurality of PCM layers each having a different crystallization temperature disposed over the bottom electrode, the PCM stack directly contacting a top surface of the resistive liner;
- and
- a top electrode disposed over the PCM stack,
- wherein the crystallization temperature varies in a descending order within a portion or an entirety of the PCM stack.
A semiconductor structure comprising:
- a bottom electrode disposed over a substrate;
- a heating element disposed in direct contact with a top surface of the bottom electrode;
- a resistive liner defining a planar surface across its entire length, such that the planar resistive liner surface extends, in its entirety, above a top surface of the heating element;
- a phase change memory (PCM) stack including a plurality of PCM layers each having a different crystallization temperature disposed over the bottom electrode, wherein each of the plurality of PCM layers includes a Ge—Sb—Te (germanium-antimony-tellurium or “GST”) alloy, the PCM stack directly contacting a top surface of the resistive liner;
- and
- a top electrode disposed over the PCM stack,
- wherein the crystallization temperature varies in an ascending order from the bottom electrode to the top electrode.
Dependencies are inferred from the claim text.