Selective Source/Drain Contacts Without Liners for Lower Resistance
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Solution Overview
Problem
High source/drain contact resistance due to high resistivity from titanium nitride and tungsten nucleation layers, which increases as contact critical dimension scales, leading to degradation in chip performance.
Innovation Solution
Fabrication of semiconductor devices with selective contacts that eliminate sidewall liners and nucleation layers, maximizing the proportion of critical dimension occupied by conductive materials, thereby reducing resistivity and enhancing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If titanium nitride and tungsten nucleation layers are used in source/drain contacts, then contact formation reliability is improved, but contact resistivity increases due to high resistivity of these layers
Solution Approach 1:
The patent removes the titanium nitride liner and tungsten nucleation layer from the contact structure. By extracting these high-resistivity layers that were previously necessary for contact formation reliability, the invention achieves lower contact resistivity while maintaining reliability through alternative means such as direct tungsten contact to the semiconductor substrate.
Solution Approach 2:
The invention changes the material composition and structural parameters of the contact. Instead of using multiple layers including TiN and W nucleation layers, the patent employs a simplified structure with direct tungsten deposition, altering the electrical and structural parameters to reduce resistivity while preserving contact reliability.
2Length of moving object
If contact critical dimension is scaled down, then device miniaturization is achieved, but source/drain contact resistance increases due to higher resistivity portion
Solution Approach 1:
By removing the TiN liner and W nucleation layer from the contact structure, the patent eliminates the high-resistivity portions that would otherwise occupy a larger proportion of the scaled-down contact dimension, thereby reducing contact resistance despite the smaller critical dimension.
Solution Approach 2:
The invention applies different material qualities to different regions: direct tungsten contact is used at the critical contact interface where low resistivity is essential, while other regions maintain necessary structural properties. This localized optimization of material quality reduces contact resistance in the critical dimension.
Data Source
AI summary
Disclosed are devices that include a contact for electrical connection with a source/drain. The contact occupies a full width of a contact well other than areas occupied by sidewall spacers. As a result, high resistivity (due to the presence of liners and nucleation layers within the contact well in conventional devices) is reduced or eliminated.