Spacer Material for Memory Contact Structure
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Solution Overview
Problem
Existing memory devices face challenges in maintaining uniformity and preventing resistance variations due to step height differences in chemical mechanical polishing processes and metallic residue redeposition during MTJ etching, which can lead to shunt failures and deteriorated characteristics of variable resistance elements.
Innovation Solution
The use of a spacer material with a lower etch rate than silicon nitride, such as SiBN, SiCN, or SiBCN, is implemented to maintain uniform thickness and prevent redeposition of metallic residues, ensuring a rectangular cross-section and minimizing CD variations and shunt failures in the MTJ structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional spacer material (silicon nitride) is used, then the manufacturing process is simple and well-established, but the spacer thickness becomes non-uniform due to step height differences in CMP processes and CD variations occur
Solution Approach 1:
The patent changes the material parameter of the spacer from conventional silicon nitride to materials with lower etch rates (such as silicon oxynitride, silicon oxycarbon nitride, or silicon carbon nitride). This parameter change enables the spacer to maintain uniform thickness through subsequent CMP and etching processes, preventing CD variations in the MTJ structure while remaining compatible with existing manufacturing processes
Solution Approach 2:
The patent employs composite material strategies by using spacers made from materials like silicon oxynitride or silicon oxycarbon nitride that combine properties of different materials. These composite materials provide both the low etch rate needed for thickness uniformity and the mechanical properties required for process compatibility, effectively resolving the contradiction between precision and complexity
2Reliability
If standard etching processes are used for MTJ structure, then the process is straightforward, but metallic residues are redeposited causing shunt failures
Solution Approach 1:
The patent introduces a specially designed spacer structure as an intermediary element that prevents direct contact between metallic residues and the MTJ structure. The spacer with its low etch rate material acts as a protective barrier, intercepting redeposited metallic particles and preventing them from causing shunt failures in the variable resistance element, thus improving reliability without significantly complicating the manufacturing process
3Productivity
If the spacer material has high etch rate (silicon nitride), then the etching process is fast and efficient, but the spacer thickness varies due to step height differences
Solution Approach 1:
The patent deliberately changes the etch rate parameter of the spacer material from high (silicon nitride) to low (silicon oxynitride, silicon oxycarbon nitride, or silicon carbon nitride). This parameter change sacrifices some etching speed but gains significant improvement in spacer thickness uniformity, preventing CD variations in the MTJ structure. The overall productivity is maintained because the slower etching of this specific spacer layer does not become the bottleneck of the entire manufacturing process
Data Source
AI summary
An electronic device may include a semiconductor memory, and the semiconductor memory may include a substrate; an interlayer dielectric layer formed 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 comprises: a spacer formed on sidewalls of the contact hole in the interlayer dielectric layer and including a material having a lower etch rate than that of silicon nitride (SiN); 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.