Variable Resistance Memory Contact Spacer Design
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Solution Overview
Problem
Existing memory devices face challenges in maintaining uniformity of the lower contact structure during the CMP process, leading to resistance variations and redeposition of metallic residues during the MTJ etch process, which affects the performance and reliability of the variable resistance element.
Innovation Solution
The solution involves forming a spacer with a substantially uniform thickness on the sidewalls of the contact hole, using a material layer deposited in an overhanging shape, which maintains the rectangular cross-section of the contact pad and prevents CD variation and metallic residue redeposition, thereby enhancing the characteristics of the variable resistance element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional lower contact structure is used during the CMP process, then the manufacturing process is simple, but the uniformity of the lower contact structure deteriorates leading to resistance variations
Solution Approach 1:
The lower contact structure is segmented into three distinct components: a contact hole, a contact plug filling part of the contact hole, and a contact pad filling the remaining portion. This segmentation allows each component to be optimized independently for uniformity and performance, resolving the contradiction between manufacturing precision and device complexity.
Solution Approach 2:
Different regions of the lower contact structure are assigned different materials and properties: the contact hole maintains a specific geometry, the contact plug uses a conductive material for electrical connection, and the contact pad uses a different material optimized for planarity and uniformity. This local quality differentiation enables each region to contribute to overall uniformity without requiring the entire structure to be complex.
2Reliability
If the lower contact structure is not optimized, then the fabrication process is straightforward, but metallic residues are redeposited during the MTJ etch process causing shunt failures
Solution Approach 1:
The lower contact structure, including the contact hole, contact plug, and contact pad, is fabricated in advance with optimized geometry and material composition before the MTJ etch process. This preliminary action ensures that metallic residues generated during MTJ etching are prevented from redepositing on critical areas, thereby preventing shunt failures without complicating the overall manufacturing process.
Solution Approach 2:
The contact pad acts as an intermediary layer between the contact plug and the variable resistance element. This intermediary structure is specifically designed to prevent metallic residue redeposition during the MTJ etch process, serving as a protective barrier that maintains reliability while keeping the fabrication process manageable.
3Manufacturing precision
If the contact pad geometry is not controlled, then the fabrication process is simple, but CD variation occurs affecting the performance of the variable resistance element
Solution Approach 1:
The geometry parameters of the contact pad, including its width, length, and thickness, are precisely controlled and optimized. By changing and fixing these parameters to specific values, the contact pad maintains uniform critical dimensions throughout the wafer, preventing CD variation in the variable resistance element while avoiding excessive structural complexity.
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 approach improves the uniformity of the lower contact structure, prevents resistance variations, and minimizes shunt failures, resulting in improved performance and reliability of the variable resistance element.
Implementation Method 1
a spacer formed on sidewalls of the contact hole in the interlayer dielectric layer and having a substantially uniform thickness
Implementation Method 2
The contact plug and the contact pad may include a metal-containing material
Data Source
AI summary
This technology provides an electronic device. An electronic device in accordance with an implementation of this document may include a semiconductor memory for storing data, and the semiconductor memory may include a substrate; an interlayer dielectric layer over the substrate and patterned to include a contact hole; a lower contact structure formed over the substrate in the contact hole; and a variable resistance element formed over and electrically coupled to the lower contact structure, wherein the lower contact structure may include: a spacer formed on sidewalls of the contact hole in the interlayer dielectric layer and having a substantially uniform thickness along a direction perpendicular to a surface of the substrate; a contact plug filling a portion of the contact hole; and a contact pad formed over the contact plug and filling a remaining portion of the contact hole.