EUV Lithography Exposure Segmentation for Mask Defect Mitigation
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Solution Overview
Problem
Conventional EUV lithography masks suffer from microscopic defects that cause phase errors in reflected light, impacting printability and patterning fidelity, which are difficult to inspect and repair.
Innovation Solution
A hybrid lithography exposure process involving multiple exposure steps with doses less than the optimized exposure dose is used to form a patterned resist layer, reducing the impact of defects by distributing their effect across multiple exposures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional EUV lithography masks are used with single exposure process, then manufacturing process is simple, but mask defects cause phase errors that severely impact patterning fidelity
Solution Approach 1:
The single lithography exposure process is segmented into multiple exposure processes. Each exposure process uses a different mask pattern (from different masks or different sub-regions) to expose the same resist layer. This segmentation distributes the impact of any single mask defect across multiple exposures, preventing a single defect from causing catastrophic patterning failures.
Solution Approach 2:
Instead of using a single optimized exposure dose that would be fully impacted by mask defects, the patent applies multiple partial exposures with doses less than the optimized exposure dose. The cumulative effect of these partial exposures achieves the desired patterning while the defect impact from any single exposure is sub-threshold and does not print.
2Manufacturing precision
If multiple exposure processes are used to reduce defect impact, then patterning fidelity is maintained, but manufacturing time increases
Solution Approach 1:
The patent implements a periodic exposure scheme where the same resist pattern is exposed multiple times with different mask patterns in a systematic sequence. This periodic action ensures that defect impacts are distributed uniformly across the production process, and the regularity of the process allows for efficient scheduling and resource utilization.
3Manufacturing precision
If high quality defect-free masks are used, then patterning fidelity is maintained, but manufacturing costs increase significantly
Solution Approach 1:
The patent converts the harmful effect of mask defects into a manageable parameter by designing a lithography process where defects are intentionally distributed across multiple exposures. Masks with reasonable defect levels can be used, and the hybrid exposure process ensures that no single defect prints, effectively converting a quality problem into a process control opportunity.
Solution Approach 2:
The patent changes the exposure dose parameter from a single optimized value to multiple sub-optimized values distributed across several exposures. This parameter change ensures that the cumulative exposure achieves the desired patterning fidelity while individual exposure doses remain below the defect print threshold, allowing the use of masks with higher acceptable defect densities.
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 hybrid process effectively minimizes the impact of defects on lithography processes, maintaining patterning fidelity while reducing manufacturing costs by utilizing masks with reasonable defects.
Implementation Method 1
performing a first exposure process to image a first pattern of a first sub-region of a first mask to the resist layer; performing a second exposure process to image a second pattern of a second sub-region of the first mask to the resist layer
Implementation Method 2
EUV lithography uses a reflective mask (also referred to as a reticle) to transfer a pattern of a layer of an integrated circuit device to a wafer
Data Source
AI summary
An extreme ultraviolet lithography method is disclosed. In an example, the EUVL method includes forming a resist layer on a substrate; performing a first exposure process to image a first pattern of a first sub-region of a first mask to the resist layer; performing a second exposure process to image a second pattern of a second sub-region of the first mask to the resist layer; and performing a third exposure process to image a third pattern of a first sub-region of a second mask to the resist layer. The second and third patterns are identical to the first pattern. The first, second and third exposure processes collectively form a latent image of the first pattern on the resist layer.