Segmented Source/Drain Contact Structure to Prevent Contact Merging
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Solution Overview
Problem
In semiconductor integrated circuits, the formation of source/drain contacts is challenging due to the difficulty in preventing adjacent contact openings from merging, leading to circuit malfunctions as the spacing between device features decreases, making it hard to maintain the integrity and performance of multi-gate devices.
Innovation Solution
A method is introduced to form a larger contact opening uniting a group of individually formed contact openings to expose a row of source/drain features between adjacent gate structures, followed by a cut metal process to divide the continuous source/drain contact into segments corresponding to individual features, thereby preventing merging and enhancing contact integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If contact openings are formed by etching dielectric layers covering source/drain features, then source/drain contacts can be formed to connect source/drain features, but adjacent contact openings merge into one larger contact opening causing shorts
Solution Approach 1:
The patent divides a single continuous metal contact rail into multiple separate contact segments by forming isolation features between adjacent source/drain features. This segmentation prevents the merging of contact openings while maintaining electrical connectivity to multiple source/drain features, thereby resolving the contradiction between contact integrity and manufacturing precision
Solution Approach 2:
The patent introduces isolation features (dielectric material) as intermediary elements between adjacent metal contact segments. These isolation features act as mediators that physically separate the contact openings while allowing the metal contact rail to extend continuously underneath, preventing shorts while maintaining electrical connectivity
2Productivity
If spacing between device features is decreased to increase functional density, then production efficiency increases and costs decrease, but contact openings above adjacent source/drain features merge
Solution Approach 1:
The patent resolves the spacing conflict by moving the separation mechanism to a different dimensional level. Instead of relying on top-down contact opening separation, the isolation features are formed at the metal contact rail level (below the dielectric layer), creating separation in the vertical dimension while allowing continuous metal extension in the horizontal dimension. This enables decreased spacing between source/drain features without contact merging
3Reliability
If a continuous metal contact rail is formed to connect multiple source/drain features, then electrical connectivity is improved, but adjacent contacts short when contact openings merge
Solution Approach 1:
The patent segments the continuous metal contact rail into separate contact segments by forming isolation features between them. Each segment maintains electrical connectivity to its corresponding source/drain feature while the isolation features prevent harmful short circuits between adjacent contacts, resolving the contradiction between connectivity and short prevention
Solution Approach 2:
The patent converts the potential harmful effect of metal continuity (which could cause shorts) into a beneficial feature. The continuous metal rail structure is retained for manufacturing simplicity and electrical connectivity, while isolation features are strategically placed to convert this continuity into segmented connectivity that prevents shorts while maintaining the benefits of continuous formation
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 effectively prevents adjacent source/drain contacts from merging, reduces contact resistance, and maintains the performance of multi-gate devices by ensuring accurate electrical connections without shorts, which is particularly beneficial in sub-10 nanometer technology process nodes.
Implementation Method 1
forming contact openings by etching dielectric layers covering the source/drain features to expose source/drain features in respective contact openings
Implementation Method 2
depositing metal material(s) into contact openings to form source/drain contacts
Implementation Method 3
it is typical to epitaxially grow some semiconductor materials over semiconductor fins as source/drain features
Data Source
AI summary
A method includes forming first and second fins disposed on a substrate, forming a gate structure over the first and second fins, epitaxially growing a first source/drain (S/D) feature on the first fin and a second S/D feature on the second fin, depositing a dielectric layer covering the first and second S/D features, etching the dielectric layer to form a trench exposing the first and second S/D features, forming a metal structure in the trench and extending from the first S/D feature to the second S/D feature, performing a cut metal process to form an opening dividing the metal structure into a first segment over the first S/D feature and a second segment over the second S/D feature, and depositing an isolation feature in the opening. The isolation feature separates the first segment from the second segment.