Source/Drain Contact Layout to Prevent Gate Shorts
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Solution Overview
Problem
As integrated circuit technologies progress towards smaller technology nodes, electrical shorts can occur between adjacent metal gates and source/drain contacts, affecting the overall performance of IC devices due to etch variation, mask overlay issues, and critical dimension uniformity limitations during the formation of source/drain contact openings.
Innovation Solution
A semiconductor structure is designed with a source/drain contact having a first portion directly above the source/drain feature and a second portion directly over an isolation feature adjacent to a gate isolation structure, where the second portion has a reduced width and depth compared to the first portion to minimize electrical shorts between metal gate segments and source/drain contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If source/drain contact openings are formed using conventional processes, then manufacturing is simpler, but electrical shorts occur between metal gates and source/drain contacts due to etch variation, mask overlay issues, and critical dimension uniformity limitations
Solution Approach 1:
The source/drain contact structure is divided into multiple portions: a first portion within the trench directly over the source/drain feature, and a second portion extending over the isolation feature. This segmentation allows the contact to be positioned away from the metal gate while maintaining electrical connection, preventing electrical shorts caused by conventional single-structure contacts
Solution Approach 2:
The contact structure extends in multiple spatial dimensions - vertically into the trench and horizontally over the isolation feature. This multi-dimensional configuration allows the contact to achieve both electrical connection functionality and spatial separation from the metal gate, resolving the contradiction between reliability and complexity
2Reliability
If the source/drain contact is positioned closer to the metal gate to reduce resistance, then contact resistance decreases, but electrical shorts occur due to process variations
Solution Approach 1:
The isolation feature serves as an intermediary structure between the source/drain contact and the metal gate. By extending the contact over this intermediary, the design achieves spatial separation to prevent shorts while the direct connection to the source/drain feature maintains low resistance, resolving the contradiction between reliability and manufacturing precision
3Reliability
If the contact width is reduced to avoid shorts, then electrical short prevention improves, but contact resistance increases
Solution Approach 1:
The contact structure exhibits different properties in different portions: the first portion within the trench has dimensions optimized for low resistance connection to the source/drain feature, while the second portion over the isolation feature has reduced width for spatial separation from the gate. This local differentiation resolves the contradiction between short prevention and resistance control
Data Source
AI summary
Semiconductor structures and methods of forming the same are provided. In an embodiment, an exemplary semiconductor structure includes a source/drain feature over a substrate; a metal gate structure extending lengthwise along a first direction and adjacent to the source/drain feature; a gate isolation structure extending lengthwise along a second direction substantially perpendicular to the first direction, and a source/drain contact electrically coupled to the source/drain feature and including a first portion directly above the source/drain feature and a second portion extending from the first portion along the first direction. In embodiments, the gate isolation structure divides the metal gate structure into two isolated portions. In embodiments, the first portion has a first width along the second direction and the second portion has a second width along the second direction, the first width being greater than the second width.