Lithographic Mask Phase-Shifted Portion Resolution
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Solution Overview
Problem
As semiconductor devices with smaller feature sizes approach the wavelength of the radiation source, optical distortion leads to difficulties in resolving features due to diffraction and interference effects, resulting in a loss of correspondence between the lithographic mask image and the patterned photosensitive material, necessitating improved lithographic printing resolution and process window.
Innovation Solution
A lithographic mask comprising an optically transparent substrate with an attenuated Phase Shift Mask (PSM) pattern and a phase-shifted optically transparent portion adjacent to the PSM pattern, which enhances image resolution by causing destructive interference and improving the edge sharpening of the pattern in the photosensitive material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the minimum feature size is decreased to increase device density, then the number of individual devices per chip increases, but the lithographic printing resolution deteriorates due to diffraction and interference effects
Solution Approach 1:
The patent converts the harmful diffraction and interference effects into beneficial features by strategically placing phase-shifted transparent portions at specific locations. These portions create controlled phase shifts that generate destructive interference at critical points, transforming the previously harmful optical effects into useful tools for sharpening patterns and improving resolution at reduced feature sizes
Solution Approach 2:
The patent applies different optical properties to different regions of the mask. By placing phase-shifted transparent portions only at specific locations adjacent to attenuated PSM patterns, the mask creates localized phase shifts that improve resolution at critical areas while maintaining standard properties elsewhere, thereby enhancing device density without compromising overall manufacturing precision
2Ease of manufacture
If conventional lithographic masks are used, then the manufacturing process is simple, but optical distortion causes loss of correspondence between mask image and patterned material
Solution Approach 1:
The patent segments the mask into distinct functional regions: attenuated PSM patterns for pattern formation and phase-shifted transparent portions for optical correction. This segmentation allows each region to perform its specific function optimally while maintaining overall mask manufacturability through established lithographic processes
Solution Approach 2:
The phase-shifted transparent portions act as intermediary elements between the incident radiation and the photosensitive material. These intermediary portions introduce controlled phase shifts that compensate for optical distortions, mediating the interaction to achieve better image correspondence while requiring only moderate increases in mask fabrication complexity
3Length of moving object
If feature sizes approach the radiation wavelength, then device miniaturization is achieved, but diffraction effects increase causing resolution loss
Solution Approach 1:
The patent changes the optical parameters of the mask by introducing phase-shifted transparent portions with specific optical path differences. These parameter changes create controlled phase shifts that modify the diffraction pattern, allowing better resolution even as feature sizes approach the radiation wavelength
Solution Approach 2:
The patent converts the harmful diffraction effects into beneficial sharpening features. By strategically placing phase-shifted portions, the diffraction pattern is modified to create destructive interference at unwanted locations and constructive interference at desired locations, turning the previously harmful diffraction into a useful resolution-enhancing 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 improves image resolution and moves the aerial image closer to the isofocal operating point, increasing the depth of focus and process window, thereby facilitating the fabrication of small geometry semiconductor devices with enhanced precision.
Implementation Method 1
enhances image resolution by causing destructive interference and improving the edge sharpening of the pattern in the photosensitive material
Data Source
AI summary
Methods for fabricating a semiconductor device and a lithographic mask of use in that method are provided for. The lithographic mask comprises an optically transparent substrate, an attPSM pattern overlying the optically transparent substrate, and a phase shifted optically transparent portion adjacent to and aligned with an edge of the attPSM pattern.