Non-Conformal FinFET Capping Layer for Sidewall-Limited Etching
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Solution Overview
Problem
In the formation of Fin Field-Effect Transistors (FinFETs), existing methods face challenges in creating a non-conformal capping layer that effectively protects underlying structures during etching processes while minimizing thickness on sidewalls to avoid impacting subsequent processes.
Innovation Solution
A non-conformal capping layer is formed using a plasma-assisted Atomic Layer Deposition (ALD) process, where a silicon-containing precursor is adsorbed, followed by purging and plasma generation to break bonds and deposit a dielectric layer with a top portion directly over protruding fins and minimal sidewall coverage, ensuring protection during etching and minimal impact on subsequent processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conformal capping layer is deposited to protect underlying structures during etching, then protection reliability is improved, but sidewall thickness becomes excessive and impacts subsequent processes
Solution Approach 1:
The patent applies local quality by creating a capping layer with spatially varying thickness: thick over horizontal surfaces (top of fins and isolation regions) for maximum protection, and thin or absent on vertical sidewalls to avoid process interference. This is achieved through plasma-assisted ALD where the plasma source geometry and process conditions are optimized to preferentially deposit material on horizontal surfaces while minimizing sidewall coverage.
2Manufacturing precision
If plasma power is increased to enhance non-conformal deposition, then sidewall thickness is reduced, but film quality deteriorates
Solution Approach 1:
The patent employs parameter changes by systematically optimizing multiple process variables including plasma power (50-200W), precursor flow rate (50-200 sccm), pressure (1-10 Torr), and temperature (25-100°C) to achieve the desired non-conformal deposition profile. By adjusting these parameters in combination, the process achieves both thin sidewall coverage and high film quality with conformal properties.
Solution Approach 2:
The patent uses periodic action through pulsed plasma delivery and cyclic precursor exposure during the ALD process. The plasma is applied in controlled pulses rather than continuously, allowing precise control over the non-conformal deposition profile while maintaining film quality. This periodic plasma activation enables selective deposition on different surfaces at different times during the cycle.
3Reliability
If conventional ALD is used to form a capping layer, then film quality is maintained, but deposition is conformal and excessive on sidewalls
Solution Approach 1:
The patent replaces the conventional conformal deposition mechanism with a plasma-assisted mechanism that introduces directional and selective deposition behavior. The plasma component fundamentally changes the deposition mechanics from purely chemical adsorption to a process involving plasma-generated radicals and ions that preferentially react on horizontal surfaces, thereby substituting the conventional ALD mechanism with a plasma-enhanced variant that achieves non-conformal profiles.
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 non-conformal capping layer provides enhanced protection to underlying structures during etching and has a minimal thickness on sidewalls, optimizing the FinFET formation process without compromising film quality or throughput.
Implementation Method 1
a plasma-assisted Atomic Layer Deposition (ALD) process, where a silicon-containing precursor is adsorbed, followed by purging and plasma generation to break bonds and deposit a dielectric layer
Implementation Method 2
where a silicon-containing precursor is adsorbed, followed by purging and plasma generation
Data Source
AI summary
A method includes forming a protruding structure, and forming a non-conformal film on the protruding structure using an Atomic Layer Deposition (ALD) process. The non-conformal film includes a top portion directly over the protruding structure, and a sidewall portion on a sidewall of the protruding structure. The top portion has a first thickness, and the sidewall portion has a second thickness smaller than the first thickness.