Quasi-Atomic Layer Etching for Pattern Density Control
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Solution Overview
Problem
Conventional dry plasma etching faces challenges in maintaining critical dimensions of complex features due to pattern density-dependent etching and micro-loading effects, which become more pronounced with increasing pitch scaling in semiconductor fabrication.
Innovation Solution
A quasi-atomic layer etching (Q-ALE) process is employed during soft-mask open, utilizing a thin conformal polymer layer to precisely transfer mask patterns into underlying layers, with controlled polymer deposition and etching cycles to maintain pattern fidelity and adjust critical dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional dry plasma etching is used for pattern transfer, then etching process can be performed, but critical dimensions of complex features cannot be maintained due to pattern density-dependent etching and micro-loading effects
Solution Approach 1:
The etching process is segmented into multiple alternating steps: a deposition step that forms a conformal polymer layer, followed by an etching step that removes material. This segmentation allows the polymer to act as a protective mask during etching, preventing pattern density-dependent effects and micro-loading by uniformly protecting all features regardless of their density or aspect ratio.
Solution Approach 2:
A conformal polymer layer is introduced as an intermediary between the plasma etching environment and the features being etched. This polymer layer serves as a protective intermediary that prevents direct plasma interaction with the features, thereby eliminating the harmful pattern density effects while still allowing controlled material removal where needed.
2Adaptability or versatility
If pitch scaling is increased to meet diverse application requirements, then circuit complexity increases, but pattern density effects and micro-loading become more pronounced
Solution Approach 1:
The process segments the interaction between plasma and features by introducing alternating deposition and etching cycles. The deposition phase builds up a protective polymer layer that is then used during the etching phase, ensuring that all features receive uniform protection regardless of pitch or density, thereby maintaining precision even as circuit complexity increases.
Solution Approach 2:
The process changes the parameters of the etching environment by controlling polymer deposition thickness and composition through the deposition step. By adjusting deposition conditions (gas composition, power, time), the polymer layer properties are optimized to provide uniform protection across features of varying sizes and densities, enabling precise pattern transfer at scaled dimensions.
3Manufacturing precision
If a conformal polymer layer is deposited for polymer-assisted etching, then etch selectivity and dimensional control improve, but process complexity increases
Solution Approach 1:
The process merges deposition and etching functions into a unified polymer-assisted etching cycle. The same polymer deposition step that protects features during etching also serves as the basis for the etching process itself, eliminating the need for separate mask deposition and simplifying the overall process flow despite the alternating cycle structure.
Solution Approach 2:
The conformal polymer layer is self-formed through automated deposition processes that conform to the feature geometry. The polymer automatically adjusts its thickness and distribution to match the underlying feature structure, eliminating the need for manual mask alignment or complex masking procedures, thereby reducing operational complexity.
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 Q-ALE process enables precise transfer of complex patterns with improved etch selectivity and dimensional control, reducing pattern density effects and micro-loading issues, allowing for precise tuning of critical dimensions and maintaining aspect ratios, especially beneficial for EUV and 193 nm resist processes.
Implementation Method 1
a relatively thin layer of conformal polymer (nm thickness range) can be used to precisely etch and transfer the desired relief pattern
Implementation Method 2
Conventional dry plasma etching, when used for pattern transfer, has challenges in maintaining CDs of various features
Data Source
AI summary
Techniques herein include an etch process that etches a layer of material incrementally, similar to mono-layer etching of atomic layer etching (ALE), but not necessarily including self-limiting, mono-layer action of ALE. Such techniques can be considered as quasi-atomic layer etching (Q-ALE). Techniques herein are beneficial to precision etching applications such as during soft-mask open. Techniques herein enable precise transfer of a given mask pattern into an underlying layer. By carefully controlling the polymer deposition relative to polymer assisted etching through its temporal cycle, a very thin layer of conformal polymer can be activated and used to precisely etch and transfer the desired patterns.