Recessed Bottom Electrode Structure for Lower-Power PCRAM
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Solution Overview
Problem
Existing phase-change random access memory (PCRAM) devices face challenges in reducing write current and write power without incurring high process costs, particularly due to the need for advanced photolithography and etch processes.
Innovation Solution
The formation of a recess in the bottom electrode of the PCRAM structure reduces the width of the electrode without using advanced photolithography and etch processes, achieved by forming spacers on the sidewalls of the opening and recessing the conductive layer, thereby reducing the write current and power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If advanced photolithography and etch processes are used to reduce the width of the bottom electrode, then the write current and power consumption are reduced, but the production cost increases
Solution Approach 1:
A recess is formed in the bottom electrode before depositing the phase change material and top electrode. This preliminary structural modification allows the bottom electrode width to be reduced without requiring advanced photolithography and etch processes, thereby reducing write power while avoiding increased production costs
Solution Approach 2:
The bottom electrode is designed with non-uniform width, featuring a narrower region at the location where it interfaces with the phase change material. This local variation in geometry reduces the write current and power consumption while maintaining manufacturing compatibility with standard processes
2Reliability
If the width of the bottom electrode is reduced, then the write current is reduced, but advanced photolithography and etch processes are required
Solution Approach 1:
The recess in the bottom electrode is formed in advance, before subsequent material deposition steps. This allows the electrode width to be reduced through a simple structural modification rather than requiring complex advanced photolithography and etch processes, thereby reducing write current while maintaining process simplicity
Solution Approach 2:
Instead of reducing the bottom electrode width through planar photolithography patterns, the invention uses a vertical dimension approach by forming a recess. This dimensional change allows width reduction to be achieved through depth-based structuring rather than lateral patterning, avoiding the need for advanced photolithography
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method allows for cost-effective reduction in write current and power while maintaining the integrity of the PCRAM device, enhancing its operational efficiency and reducing process costs.
Implementation Method 1
The chalcogenide semiconductors, also called phase change materials, have a crystalline state and an amorphous state. In the crystalline state, the phase change materials have a low resistivity, while in the amorphous state they have a high resistivity. The resistivity ratios of the phase change materials in the amorphous and crystalline states are typically greater than 1000 and thus the phase change memory devices are unlikely to have erroneous reading. The chalcogenide materials are stable at certain temperature ranges in both crystalline and amorphous states and can be switched back and forth between the two states by electric pulses.
Data Source
AI summary
A device and a method of forming same are provided. The device includes a substrate, a first dielectric layer over the substrate, a bottom electrode extending through the first dielectric layer, a phase-change layer over the bottom electrode, and a top electrode over the phase-change layer. The phase-change layer includes a first portion extending into the bottom electrode and a second portion over the first portion and the first dielectric layer. A width of the first portion decreases as the first portion extends toward the substrate. The second portion has a first width. The top electrode has the first width.