Micro-shift Divisional Exposure for Sub-Resolution Photoresist Patterning
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Solution Overview
Problem
Current photolithography techniques face limitations in achieving fine line patterns due to the resolution limits of photoresist patterns, particularly in increasing pattern density and forming lines and spaces below the resolution limit of exposure apparatuses.
Innovation Solution
The proposed method involves a micro-shift divisional exposure technique, where a reticle is shifted below the line width of a mask pattern, allowing for two divisional exposures with energies higher than or equal to the threshold energy, overlapping the spatial distribution of exposure energies to form a photoresist pattern with reduced line width and suppressed undercut, enabling the formation of patterns finer than what is achievable by single overexposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If single photolithography exposure is used, then the process is simple and fast, but the line width cannot be reduced below the resolution limit of the exposure apparatus
Solution Approach 1:
The patent divides a single photolithography exposure into two separate exposure steps with different reticle positions. The first exposure uses a reticle positioned at a first location, and the second exposure uses a reticle positioned at a second location offset from the first. This segmentation allows each exposure to contribute differently to the final pattern, enabling line widths below the resolution limit by combining the effects of both exposures.
Solution Approach 2:
The patent introduces a positional dimension to the exposure process by moving the reticle between two different locations during the two exposure steps. This dimensional change in reticle positioning enables the system to achieve sub-resolution line widths by utilizing the spatial relationship between the two exposure positions and the corresponding photoresist patterns.
2Manufacturing precision
If double patterning is used to increase pattern density, then the line width can be reduced, but the resolution limit of the photoresist pattern increases
Solution Approach 1:
The patent segments the exposure process into two distinct steps with different reticle positions, where each exposure creates a photoresist pattern that contributes to the final sub-resolution pattern. The first exposure creates a pattern at a first position, and the second exposure creates a pattern at a second position, and the combination of these segmented patterns achieves the desired fine line width while maintaining pattern integrity.
3Manufacturing precision
If high exposure energy is used to reduce line width, then the line width decreases, but the photoresist pattern may collapse
Solution Approach 1:
The patent segments the total exposure energy into two separate exposure steps, each using a portion of the total energy. By distributing the exposure energy across two steps rather than applying it all at once, the patent achieves the desired line width reduction while preventing photoresist pattern collapse that would occur with a single high-energy exposure.
Solution Approach 2:
The patent employs periodic action by performing two sequential exposure steps with reticles positioned at different locations. This periodic exposure process allows the photoresist to be exposed in controlled increments, building up the pattern gradually and maintaining structural integrity while achieving the target line width.
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 method effectively reduces the line width of photoresist patterns to 20 nm, surpassing the resolution limit of ArF immersion processes, and maintains pattern integrity by preventing collapse, achieving a line-to-space width ratio of 1:3 and an aspect ratio of 4 or less.
Implementation Method 1
Photolithography is technology for transferring a mask pattern of a reticle to a photoresist
Data Source
AI summary
A patterning method includes: forming a first photoresist layer on a substrate; performing first divisional exposure on the first photoresist layer with first exposure energy, higher than or equal to threshold energy, using a reticle having lines and spaces of a mask pattern and an exposure apparatus; and shifting the reticle below a line width of the mask pattern and performing second divisional exposure on the first photoresist layer with second exposure energy, higher than or equal to the threshold energy, using the reticle to form a photoresist pattern. A spatial distribution of the first exposure energy may overlap a spatial distribution of the second exposure energy.