Gas Phase Etch Trim for EUV Line Width Roughness
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Solution Overview
Problem
As geometries in substrate processing shrink, line width roughness (LWR) and line edge roughness (LER) performance degrades during the pattern transfer process, particularly at pitches approaching 30 nm or less, due to aspect ratios and materials required in small pitch processes, leading to undesirable 'wiggle' in patterned structures.
Innovation Solution
A method involving a plasma-free gas phase etch process is used to trim the critical dimension (CD) of the etch target layer, which can be combined with plasma etch trim processes, to finely tune the CD and reduce LWR/LER degradation, utilizing an isotropic gaseous chemical removal process that is selective to an etch stop layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If plasma etch trim process is used to reduce critical dimension, then line width critical dimension is improved, but line width roughness and line edge roughness degrade
Solution Approach 1:
The patent segments the CD trimming process into two distinct stages: (1) plasma etch trim to achieve initial CD reduction, and (2) gas phase non-plasma etch to perform final precision trimming. This segmentation allows each process to be optimized for its specific function, with the gas phase process providing the final roughness improvement without compromising the CD precision already achieved.
Solution Approach 2:
The gas phase non-plasma etch process acts as an intermediary step between the plasma etch trim and the final pattern. This intermediary process uses a different mechanism (chemical vapor deposition-style gas phase reaction) that is less damaging to the pattern edges, thereby mediating between the need for CD reduction and the need to maintain pattern integrity and minimize roughness.
2Manufacturing precision
If conventional plasma etching is used for pattern transfer, then critical dimension is achieved, but corner rounding occurs
Solution Approach 1:
The gas phase non-plasma etch serves as an intermediary correction step that reverses the corner rounding effect of the plasma etch. By applying a controlled amount of this second etching process, the corners are sharpened back to their original sharpness while maintaining the reduced critical dimension achieved by the first process.
Solution Approach 2:
The patent changes the fundamental parameters of the etching process by transitioning from a plasma-based mechanism to a gas phase chemical reaction mechanism. This parameter change alters the etching characteristics to be more selective and less prone to causing corner rounding, thereby preserving shape integrity while achieving CD control.
3Ease of manufacture
If photo resist critical dimension transfer scheme is used, then pattern is formed, but additional trimming process is required to achieve target CD
Solution Approach 1:
The patent merges the CD trimming function with the pattern transfer process by using the gas phase non-plasma etch to perform both tasks simultaneously: it completes the pattern transfer from photo resist to etch target layer while also achieving the final precision CD trimming in a single integrated process step.
Solution Approach 2:
The gas phase non-plasma etch process is designed to perform multiple functions: (1) complete the pattern transfer through the intervening layers, (2) achieve final precision CD trimming, and (3) minimize pattern damage and roughness. This multi-functionality reduces the need for separate process steps while maintaining ease of manufacture.
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 effectively reduces LWR/LER degradation by allowing precise control of CD trimming, maintaining pattern integrity and preventing corner rounding, while enabling narrower linewidths without significant roughness issues, thus improving the accuracy of pattern transfer in extreme ultraviolet (EUV) lithography and multiple patterning schemes.
Implementation Method 1
a gas phase non-plasma critical dimension trim process to trim a target structure
Implementation Method 2
plasma etch trim processes may be used in combination with the gas phase etch process
Data Source
AI summary
A substrate is provided with a patterned layer over a stack of one or more processing layers. The processing layers include at least one patterned layer and one etch target layer. CD trimming between the CD of the patterned layer and the CD of the etch target layer may be achieved after the pattern is transferred to the etch target layer. After the etch target layer is patterned, a plasma free gas phase etch process may be used to trim the CD of the etch target layer to finely tune the CD. In an alternate embodiment, plasma etch trim processes may be used in combination with the gas phase etch process. In such an embodiment, partial CD trimming may be achieved via the plasma etching of the various process layers and then additional CD trimming may be achieved by subjecting the etch target layer to the plasma free gas phase etch after the desired pattern has been formed in the etch target layer.