Photomask Segmented Light-Shielding for Resolution and Defect Control
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Solution Overview
Problem
The existing photomask technologies face challenges in simultaneously forming fine isolated line patterns and large line patterns with high resolution and without resist defects, as they either suffer from reduced resolution or resist defects due to the presence of side lobes and unexposed regions when using enhancer masks with chemically amplified resists and immersion exposure processes.
Innovation Solution
A photomask design featuring a first light-shielding pattern with a semi-light-shielding portion and an auxiliary pattern, and a second light-shielding pattern with a semi-light-shielding portion and a light-shielding portion, where the light-shielding portion has a specific width to prevent side lobes and resist defects, allowing for the formation of both fine and large line patterns with improved resolution and reduced defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an enhancer mask is used to form fine isolated line patterns, then the resolution is improved, but side lobe formation occurs and resist defects are generated
Solution Approach 1:
The light-shielding pattern is divided into multiple regions with different light-shielding properties: a first light-shielding region with first light-shielding properties and a second light-shielding region with second light-shielding properties. This segmentation allows different portions of the pattern to be formed with different optical characteristics, suppressing side lobe formation while maintaining resolution for fine isolated line patterns.
Solution Approach 2:
Different regions of the photomask are assigned different light-shielding properties tailored to their specific function. The first light-shielding region uses properties optimized for fine pattern formation, while the second light-shielding region uses properties that suppress unwanted side lobes. This local optimization resolves the contradiction between achieving high resolution and preventing harmful side effects.
2Manufacturing precision
If oblique-incidence exposure is used to form densely arranged line patterns, then the depth of focus is improved, but the contrast and depth of focus of isolated line patterns are deteriorated
Solution Approach 1:
The photomask pattern is segmented into densely arranged line pattern regions and isolated line pattern regions. Each region can be exposed with optimized lighting conditions through the use of different light-shielding properties in different areas, allowing dense patterns to benefit from oblique-incidence exposure while isolated patterns maintain high contrast.
Solution Approach 2:
Different areas of the photomask are designed with local optical properties that match the exposure requirements of the underlying pattern. This allows the system to simultaneously optimize for both dense pattern formation (requiring oblique incidence) and isolated pattern formation (requiring vertical incidence) without compromise.
3Measurement precision
If a light source of low coherence is used to form isolated fine line patterns, then the contrast is improved, but the formation of dense patterns becomes difficult
Solution Approach 1:
The photomask is designed with segmented light-shielding regions that have different optical properties. This segmentation allows the use of low coherence light sources to form isolated fine line patterns with high contrast, while the specific structural design of different regions enables dense patterns to be formed simultaneously without requiring high coherence.
Solution Approach 2:
Different regions of the photomask are optimized for different pattern types. The light-shielding properties in each region are tailored to work effectively with low coherence light sources for isolated patterns, while the geometric design of dense pattern regions compensates for the lower coherence to enable their formation.
4Adaptability or versatility
If a light source of medium degree of coherence is used to balance both isolated and dense patterns, then both pattern types can be formed, but the effects of vertical and oblique incident light components cancel each other
Solution Approach 1:
The photomask pattern is segmented into distinct regions with different light-shielding properties. This segmentation allows each region to be optimized for its specific pattern type (isolated or dense), eliminating the need to use medium coherence light that compromises the refinement of either pattern type. Each region can achieve optimal refinement with appropriately tailored optical properties.
Solution Approach 2:
Different regions of the photomask are assigned local optical properties that maximize pattern refinement for their specific function. This local optimization eliminates the cancellation effect of using medium coherence light, as each region independently achieves optimal performance for its intended pattern type without being constrained by the need to balance conflicting requirements.
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 proposed photomask design effectively suppresses the reduction of resolution and occurrence of resist defects, enabling the simultaneous formation of fine and large line patterns with enhanced contrast and pattern fidelity, suitable for advanced semiconductor fabrication.
Implementation Method 1
light passing through the auxiliary pattern 13 cancels a portion of light passing through the opening 14 and coming around the back of the semi-light-shielding portion 12
Data Source
AI summary
A photomask includes: a transparent substrate having a transparent property against exposing light; a first light-shielding pattern formed on the transparent substrate and having a first dimension; a second light-shielding pattern formed on the transparent substrate and having a second dimension larger than the first dimension; and an opening provided in part of the transparent substrate where the first light-shielding pattern and the second light-shielding pattern are not formed. The first light-shielding pattern includes a first semi-light-shielding portion and an auxiliary pattern which is arranged within the first semi-light-shielding portion and allows the exposing light to pass through in an opposite phase with respect to the first semi-light-shielding portion. The second light-shielding pattern includes a second semi-light-shielding portion and a light-shielding portion which does not substantially allow the exposing light to pass through.