Tungsten Gapfill Using Molybdenum Co-Flow for Void-Free Features
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Solution Overview
Problem
Conventional deposition methods struggle to achieve defect-free filling of high aspect ratio features in semiconductor manufacturing due to the formation of mushroom-shaped film profiles, leading to premature pinching off and voids, and existing solutions either reduce throughput or alter the physical properties of the deposited film.
Innovation Solution
A method involving simultaneous exposure of a substrate with a tungsten halide, a molybdenum halide, and a reductant to form bottom-up tungsten gapfill, reducing the deposition rate by adding a molybdenum halide to the tungsten CVD process, which controls the deposition rate and prevents substantial deposition on the top surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional deposition methods are used to fill high aspect ratio features, then the deposition process is simple and fast, but the film forms a mushroom shape profile causing pinching off and voids in the lower region
Solution Approach 1:
A molybdenum halide intermediary substance is introduced into the tungsten CVD process to modulate the deposition rate. The molybdenum halide acts as a mediator that temporarily occupies deposition sites and releases tungsten more slowly, enabling uniform bottom-up filling of high aspect ratio features without mushroom-shaped profiles
Solution Approach 2:
The deposition rate parameter is dynamically changed by introducing molybdenum halide into the reaction chamber. This chemical parameter modification transforms the deposition kinetics from rapid top-down growth to controlled bottom-up filling, achieving uniform film distribution in high aspect ratio structures
2Manufacturing precision
If dep-etch processes are used to achieve bottom-up filling, then the film profile is improved, but the throughput decreases due to alternating deposition and etch modes
Solution Approach 1:
The deposition and etch processes are merged into a single continuous deposition step by incorporating molybdenum halide into the CVD process. This combination eliminates the need for alternating deposition and etch cycles while maintaining bottom-up filling capability, thereby improving throughput
Solution Approach 2:
The useful action of material deposition continues uninterrupted throughout the process. By using molybdenum halide to control deposition kinetics, the process maintains continuous tungsten deposition without requiring intermittent etching steps, achieving both bottom-up filling and high throughput
3Manufacturing precision
If poisoning treatment with radical treatments or chemical inhibitors is used, then bottom-up filling is achieved, but the film resistivity increases
Solution Approach 1:
Instead of using chemical inhibitors that alter film properties, the molybdenum halide temporarily changes the deposition kinetics parameter during the process. The molybdenum species are volatile and do not remain in the final film, preserving the tungsten's electrical properties while controlling the deposition rate
4Manufacturing precision
If molybdenum halide is added to reduce tungsten deposition rate, then bottom-up filling is achieved, but the process complexity increases
Solution Approach 1:
The molybdenum halide serves multiple functions simultaneously: it controls deposition rate, enables bottom-up filling, and maintains film quality. This multi-functionality reduces the need for separate process steps, offsetting the initial complexity addition with process consolidation
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 enables defect-free filling of high aspect ratio features without significant resistivity changes and increased throughput, ensuring uniform tungsten deposition within the feature without voids or seams.
Implementation Method 1
A method involves simultaneously exposing a substrate with a feature therein to flows of a tungsten halide, a molybdenum halide and a reductant
Implementation Method 2
adding a flow of a molybdenum halide to a tungsten CVD process comprising a flow of a tungsten halide and a reductant
Data Source
AI summary
Some embodiments of the disclosure relate to methods for forming a bottom-up tungsten gapfill. Some embodiments of the disclosure relate to methods for reducing the deposition rate of tungsten by chemical vapor deposition. A molybdenum halide precursor is added to a tungsten halide precursor and a reductant. The co-flow of tungsten halide and molybdenum halide demonstrates either reduced or eliminated tungsten growth.