Seamless Tungsten Fill via Oxidation-Reduction Cycle
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Solution Overview
Problem
Conventional deposition methods struggle to achieve seamless filling of high aspect ratio features in semiconductor manufacturing, often resulting in mushroom-shaped film profiles with seams or voids due to material deposition imbalances, particularly in small features.
Innovation Solution
A method involving atomic layer deposition of tungsten, followed by oxidation and reduction processes to form a seamless tungsten fill within substrate features, utilizing thermal or plasma oxidation and reduction techniques to eliminate seams and achieve coplanarity with the substrate surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional deposition methods are used to fill high aspect ratio features, then material can be deposited onto the substrate, but the film forms a mushroom shape with seams or voids due to excessive deposition on top regions compared to bottom regions
Solution Approach 1:
The patent applies preliminary action by first forming a mandrel structure within the feature before depositing tungsten. The mandrel serves as a placeholder that defines the feature geometry and enables subsequent planarization to achieve coplanar surfaces. This preliminary structure allows the tungsten deposition to proceed uniformly without forming mushroom shapes, as the mandrel prevents excessive material accumulation at the top during deposition.
2Manufacturing precision
If atomic layer deposition is used to deposit tungsten for gap filling, then tungsten can be deposited into the feature, but seams form within the gap fill limiting the process effectiveness
Solution Approach 1:
The patent applies the taking out principle by removing the problematic seam formation issue through a multi-step process. First, a mandrel is extracted/removed after tungsten deposition, creating a cavity. Then tungsten is deposited again to fill the cavity. Finally, the top surface is planarized to remove any remaining seams or excess material, resulting in a seamless tungsten fill.
Solution Approach 2:
The patent applies parameter changes by modifying the deposition process parameters and sequence. Instead of a single continuous deposition, the process uses multiple deposition steps with intermediate planarization. The deposition parameters are optimized to achieve uniform coating on the mandrel surface, and the planarization step adjusts the surface topology to eliminate seams before final tungsten deposition.
3Quantity of substance
If tungsten is deposited to fill the feature, then the feature can be filled, but overburden forms on the substrate surface outside the feature requiring additional processing
Solution Approach 1:
The mandrel structure serves as a preliminary action that defines the deposition boundary. During tungsten deposition, the mandrel confines the material to the feature region, preventing overburden formation on the substrate surface outside the feature. This eliminates or minimizes the need for subsequent planarization processing to remove excess tungsten from surrounding areas.
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 ensures defect-free, seamless tungsten gapfilling by removing overburden and converting tungsten oxide pillars back to tungsten, maintaining the feature's shape and integrity without seams, with the top surface adjusted to be within ±10 Å of the substrate surface.
Implementation Method 1
The tungsten film is oxidized to form a tungsten oxide pillar which extends from the substrate feature without a seam
Implementation Method 2
The tungsten oxide pillar is reduced to tungsten. The tungsten forms a substantially seamless tungsten gapfill within the feature
Data Source
AI summary
Methods for filling a substrate feature with a seamless tungsten fill are described. The methods include depositing a tungsten film, oxidizing the tungsten film to a tungsten oxide pillar, reducing the tungsten oxide film to a seamless tungsten gapfill and optionally depositing additional tungsten on the tungsten gapfill.