Two-State Mask Lithography Resolution Enhancement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing lithography techniques face limitations such as shadowing effects and inadequate resolution, which hinder the ability to achieve high-resolution imaging and sufficient depth of focus in semiconductor manufacturing.
Innovation Solution
A lithography process utilizing a mask with two states of transmissivity and phase difference, combined with on-axis illumination and a pupil filter, to enhance imaging resolution and depth of focus by directing diffracted light and minimizing non-diffracted light, allowing for improved imaging of IC patterns on semiconductor wafers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If off-axis illumination is used, then imaging resolution is improved, but depth of focus is reduced and forbidden-pitch issues occur
Solution Approach 1:
The patent changes the illumination parameter from off-axis to on-axis illumination, which fundamentally alters the diffraction pattern and eliminates the forbidden-pitch problem while maintaining depth of focus across all pitch ranges
Solution Approach 2:
The patent segments the mask into multiple regions with different transmissivity states (first mask state with higher transmissivity, second mask state with lower transmissivity), enabling independent control of diffraction patterns from different mask regions to achieve both high resolution and extended depth of focus
2Measurement precision
If phase shift mask is used, then imaging resolution is improved, but shadowing effect increases
Solution Approach 1:
The patent applies local quality by creating different transmissivity states in different mask regions, where the first mask state region provides high transmissivity for bright features and the second mask state region provides low transmissivity for dark features, locally optimizing the mask properties to reduce shadowing effects while maintaining resolution
Solution Approach 2:
The patent converts the harmful shadowing effect into a beneficial contrast enhancement mechanism by using the shadowing regions to define dark features and the non-shadowing regions to define bright features, effectively using the shadowing effect itself as part of the imaging mechanism
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 solution achieves enhanced illumination resolution and depth of focus, enabling the production of smaller and more complex semiconductor circuits without the limitations of traditional techniques, such as off-axis illumination, which face forbidden-pitch issues and reduced depth of focus at certain pitches.
Implementation Method 1
directing diffracted light and minimizing non-diffracted light
Data Source
AI summary
A lithography process in a lithography system includes loading a mask that includes two mask states defining an integrated circuit (IC) pattern. The IC pattern includes a plurality of main polygons, wherein adjacent main polygons are assigned to different mask states; and a background includes a field in one of the mask states and a plurality of sub-resolution polygons in another of the two mask states. The lithography process further includes configuring an illuminator to generate an illuminating pattern on an illumination pupil plane of the lithography system; configuring a pupil filter on a projection pupil plane of the lithography system with a filtering pattern determined according to the illumination pattern; and performing an exposure process to a target with the illuminator, the mask, and the pupil filter. The exposure process produces diffracted light and non-diffracted light behind the mask and the pupil filter removes most of the non-diffracted light.