Oblique Deposition and Etch Patterning for Tip-to-Tip CD Control
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Solution Overview
Problem
The semiconductor industry faces challenges in precisely controlling the tip-to-tip critical dimension (CD) of features on substrates, particularly at sub-resolution dimensions and small feature sizes, due to stochastic effects in extreme ultraviolet lithography (EUVL).
Innovation Solution
The method involves using oblique deposition to deposit an etch mask material on the sidewalls of patterned photoresist openings, followed by an oblique etch process to refine the openings, thereby reducing initial CD variations and improving CD control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional lithographic processes are used to expose patterns onto substrates, then the manufacturing process is simple and straightforward, but the precision of feature dimensions and pitch control deteriorates as feature sizes shrink below optical resolution limits
Solution Approach 1:
The patent segments the pattern transfer process into multiple steps: initial lithographic exposure to create a relaxed pattern, followed by oblique deposition to create sidewall masks, and selective etching to achieve the final refined pattern. This segmentation allows each step to optimize for its specific function, achieving precision beyond single-step lithography capabilities.
Solution Approach 2:
The patent introduces a temporal dimension by performing sequential operations (deposition then etching) and a spatial dimension through oblique angles. The oblique deposition at non-normal angles creates asymmetric material distribution on sidewalls, adding dimensional control that transforms the 2D lithographic pattern into a 3D structured mask for precise feature definition.
2Manufacturing precision
If the lithographic exposure dose is increased to improve pattern definition, then the pattern precision improves, but the energy consumption and potential substrate damage increase
Solution Approach 1:
The patent performs preliminary lithographic exposure at a lower, safer dose to create an initial pattern that does not require maximum precision. The subsequent oblique deposition and selective etching steps refine this initial pattern, achieving the final precision without requiring the lithographic step to operate at high energy doses that could damage the substrate.
3Manufacturing precision
If oblique deposition is performed at high angles to achieve preferential sidewall coverage, then the mask material coverage on sidewalls improves, but the deposition rate and uniformity deteriorate
Solution Approach 1:
The patent applies oblique deposition at angles that provide sufficient sidewall coverage without requiring maximum oblique angles. The deposition parameters are optimized to achieve the minimum necessary sidewall mask thickness for effective pattern transfer, accepting slightly reduced sidewall coverage in exchange for significantly improved deposition rate and uniformity across the substrate.
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 tip-to-tip CD variation, allowing for more precise control of feature dimensions, even at small scales, and reduces the dose requirement for lithographic exposure, enhancing process efficiency.
Implementation Method 1
depositing a mask material preferentially on the first side within the initial openings using an oblique deposition process performed at a first angle inclined from the first side
Implementation Method 2
removing a portion of the patterned photoresist using an oblique etch process performed at a second angle inclined from the second side
Implementation Method 3
performing a first oblique gas cluster ion beam (GCIB) process to preferentially deposit a mask material within the initial openings on the first side
Implementation Method 4
performing a second oblique gas cluster ion beam (GCIB) process to form final openings by preferentially removing a portion of the photoresist
Data Source
AI summary
A method of processing a substrate that includes receiving a patterned photoresist formed over a substrate, the patterned photoresist defining initial openings, each of the initial openings including a first side and an opposite second side along a first direction; depositing a mask material preferentially on the first side within the initial openings using an oblique deposition process performed at a first angle inclined from the first side; and removing a portion of the patterned photoresist using an oblique etch process performed at a second angle inclined from the second side, the mask material and a remaining portion of the patterned photoresist defining final openings.