Void-Free Cobalt Gap Fill via Plasma Inhibition
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Solution Overview
Problem
Conventional semiconductor fabrication methods face challenges in depositing tungsten due to increasing feature narrowness and aspect ratios, leading to void formation in features with re-entrant profiles, which results in device failure.
Innovation Solution
A method involving selective inhibition of cobalt nucleation on feature surfaces using a barrier layer and plasma treatment, followed by cobalt deposition using a cobalt-containing precursor and reducing agent, to achieve void-free cobalt filling in features with high aspect ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional CVD tungsten deposition is used, then the deposition process is simple, but voids form in features with high aspect ratios and re-entrant profiles
Solution Approach 1:
A barrier layer is deposited on the feature surfaces before cobalt deposition to control nucleation. This preliminary action prevents unwanted cobalt growth at the feature openings while allowing controlled deposition in the feature interiors, eliminating voids without requiring complex multi-step processes
Solution Approach 2:
The barrier layer provides selective inhibition of cobalt nucleation at different locations within the feature. The top surfaces and sidewalls near openings have different barrier layer properties compared to deeper regions, enabling localized control of cobalt deposition to achieve void-free filling
2Length of moving object
If features are made narrower with higher aspect ratios, then device scaling is achieved, but cobalt nucleation control becomes more difficult
Solution Approach 1:
The barrier layer acts as an intermediary between the feature geometry and cobalt deposition. It mediates the nucleation process by providing a controlled interface that prevents direct cobalt interaction with feature surfaces at openings, enabling precise nucleation control even in sub-3nm features with high aspect ratios
3Productivity
If cobalt deposition is performed without selective inhibition, then the deposition process is fast, but pinch-off occurs in re-entrant patterns
Solution Approach 1:
The barrier layer is applied in advance to prevent pinch-off by inhibiting cobalt nucleation at critical locations where re-entrant profiles would cause premature closure. This preliminary anti-action maintains feature openness during deposition, allowing complete filling without sacrificing deposition rate or uniformity
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
The method enables void-free cobalt filling in features with high aspect ratios, improving the reliability of semiconductor devices by controlling cobalt film growth and preventing pinch-off in re-entrant patterns.
Implementation Method 1
exposing the substrate to plasma generated from nitrogen-containing gas
Implementation Method 2
depositing cobalt in the feature in accordance with the differential inhibition profile... (c) is performed by chemical vapor deposition
Implementation Method 3
exposing the substrate to a cobalt-containing precursor and a reducing agent
Data Source
AI summary
Provided herein are methods of depositing void-free cobalt into features with high aspect ratios. Methods involve (a) partially filling a feature with cobalt, (b) exposing the feature to a plasma generated from nitrogen-containing gas to selectively inhibit cobalt nucleation on surfaces near or at the top of the feature, optionally repeating (a) and (b), and depositing bulk cobalt into the feature by chemical vapor deposition. Methods may also involve exposing a feature including a barrier layer to a plasma generated from nitrogen-containing gas to selectively inhibit cobalt nucleation. The methods may be performed at low temperatures less than about 400° C. using cobalt-containing precursors.