MRAM Bottom Electrode Tapered Profile for Short Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current semiconductor manufacturing techniques for MRAM structures face issues with redeposition and partial metallic shorts due to the size of the bottom electrode (BEL), which affects switching efficiency and resistance, particularly when the MTJ size is reduced.
Innovation Solution
A sub-lithographic bottom electrode connection is formed with a small top surface to avoid partial shorts and a larger bottom surface to prevent excessive resistance increase, involving a method that includes patterning a mask, etching openings, depositing conductive barrier and fill materials, and planarizing to create a multi-layered magnetic tunnel junction structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the bottom electrode size is reduced to increase switching efficiency, then switching efficiency is improved, but partial metallic shorts occur
Solution Approach 1:
The bottom electrode transitions from a planar two-dimensional structure to a three-dimensional structure with a tapered profile, where the top surface area is smaller than the bottom surface area. This dimensional change allows the electrode to maintain small top dimensions for efficient switching while having larger bottom dimensions that prevent partial metallic shorts.
Solution Approach 2:
The bottom electrode employs an asymmetric geometry where the top surface area is deliberately made smaller than the bottom surface area. This asymmetric design resolves the contradiction by having the small top area optimize switching efficiency while the larger bottom area prevents partial metallic shorts.
2Productivity
If the bottom electrode size is reduced to increase switching efficiency, then switching efficiency is improved, but resistance increases excessively
Solution Approach 1:
The bottom electrode adopts a three-dimensional tapered structure where the vertical dimension creates a gradient in cross-sectional area. The small top area enables efficient switching, while the progressively larger bottom area maintains low resistance by providing sufficient conductive path area.
Solution Approach 2:
The asymmetric bottom electrode design with smaller top area and larger bottom area resolves the contradiction between switching efficiency and resistance. The small top area optimizes switching efficiency, while the larger bottom area ensures adequate current carrying capacity and prevents excessive resistance.
3Productivity
If a small bottom electrode is used, then switching efficiency is improved, but metal fill requirements become more stringent
Solution Approach 1:
The tapered three-dimensional structure of the bottom electrode creates a volume expansion from the small top area to the larger bottom area. This volumetric approach allows the metal fill to be optimized at the bottom where space is available, while maintaining the small top footprint required for efficient switching.
Solution Approach 2:
The asymmetric bottom electrode geometry with larger bottom area provides more space for metal fill deposition and consolidation, making the manufacturing process more robust. The small top area maintains switching efficiency, while the larger bottom area facilitates easier metal fill without requiring extremely stringent process controls.
Data Source
AI summary
A semiconductor structure and fabrication method of forming a semiconductor structure. The structure is a MRAM element having a first conductive electrode embedded in a first interconnect dielectric material layer upon which a multi-layered magnetic tunnel junction (MTJ) memory element is formed in a magnetoresistive random access memory (MRAM) device area. The first conductive electrode includes a first end having a top surface of a first surface area and a second end having a bottom surface of a second surface area, the first surface area being smaller than the second surface area. The second end of the bottom electrode includes a barrier liner material including a metal fill material, and the first end of the bottom electrode is a pillar structure formed as a result of an etchback process in which the metal barrier liner is recessed relative to the metal fill material.