Variable Impedance Memory Contact Structure Using Etch Stop Layers
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Solution Overview
Problem
Conventional conductive bridging random access memory (CBRAM) and resistive RAM (RRAM) elements face challenges in processing due to defects in patterned metal electrodes and thermal instability caused by large interface areas between active electrodes and solid electrolytes, particularly during the back-end-of-line (BEOL) fabrication process.
Innovation Solution
The implementation of memory elements with reduced electrode contact areas using an etch stop layer and hard etch mask structures, which allow for the formation of memory elements without patterning and etching a blanket electrode layer, thereby minimizing defects and ensuring uniform performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a blanket layer of metal (such as silver) is used for the active electrode, then the electrode can be formed without patterning steps, but the processing becomes difficult due to resulting defects
Solution Approach 1:
The patent divides the electrode formation process into segments: first forming a continuous blanket layer, then using etch stop layers and hard etch masks to create discrete contact regions. This segmentation allows the benefits of blanket layer formation while achieving the precision of patterned electrodes without direct patterning of the metal layer itself.
Solution Approach 2:
The patent introduces intermediary layers (etch stop layers and hard etch masks) between the blanket metal layer and the underlying structures. These intermediaries enable precise definition of electrode contact areas through etching processes without requiring direct photolithographic patterning of the metal, thus reducing defects while maintaining ease of formation.
2Reliability
If a large interface area between active electrode and solid electrolyte is used, then better contact is achieved, but thermal instability and performance variations increase
Solution Approach 1:
The patent applies local quality by creating distinct regions with different interface areas. The etch stop layer and hard etch mask define localized contact regions where the electrode interfaces with the solid electrolyte. This allows optimization of contact quality in specific locations while maintaining smaller overall interface areas to reduce thermal instability and performance variations.
Data Source
AI summary
A memory element can include an opening formed within at least one insulating layer formed on an etch stop layer that exposes a first electrode portion and the etch stop layer at a bottom of the opening; a second electrode portion, formed on at least a side surface of the opening and in contact with the first electrode portion, the second electrode portion not filling the opening and being substantially not formed over a top surface of the at least one insulating layer; and at least one memory layer formed on a top surface of the at least one insulating layer and in contact with the second electrode portion, the at least one memory layer being reversibly programmable between at least two impedance states. Methods of forming such memory elements are also disclosed.