Projection Exposure Apparatus Wavefront Correction for Mask Aberrations
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current projection exposure apparatuses for microlithography face challenges in correcting structure- and pitch-dependent aberrations, particularly astigmatism, due to rigorous mask effects, which affect imaging quality and integration density, especially with increasing numerical apertures and wavelengths.
Innovation Solution
The method involves wavefront manipulation using manipulators within the projection exposure apparatus, combined with adjustments in illumination settings and polarization, to compensate for mask-induced aberrations by accounting for prior information on mask structures, including structure directions, pitches, and widths, thereby optimizing the wavefront and improving imaging performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the numerical aperture NA is increased to reduce the critical dimension CD, then the resolution is improved, but the depth of focus DOF is reduced and the process window is reduced
Solution Approach 1:
The patent changes the polarization state of illumination light as a parameter to compensate for mask-induced wavefront aberrations. By switching between different polarization states (s-polarization, p-polarization, circular polarization) and adjusting the illumination setting, the system optimizes imaging conditions for different mask structures and pitches, thereby maintaining a larger process window while achieving high resolution with increased numerical aperture.
2Manufacturing precision
If wavefront manipulation is applied to correct mask-induced aberrations, then imaging quality is improved, but device complexity is increased
Solution Approach 1:
The patent makes the illumination system multi-functional by enabling it to provide different polarization states and illumination settings through a unified optical path. The same illumination system can switch between s-polarization, p-polarization, circular polarization, and various illumination modes (conventional, annular, dipole, quadrupole) without requiring separate dedicated systems, thereby reducing overall device complexity while achieving wavefront correction.
Solution Approach 2:
The patent uses parameter changes in the illumination system (polarization state, illumination setting) to achieve wavefront manipulation for correcting mask-induced aberrations. By adjusting these illumination parameters based on the specific mask structure and pitch, the system corrects imaging quality without adding complex mechanical or optical correction elements.
3Manufacturing precision
If different illumination settings and polarization states are used to correct aberrations for different pitches and structure directions, then manufacturing precision is improved, but ease of operation is worsened
Solution Approach 1:
The patent implements a feedback mechanism where the control unit determines the appropriate illumination setting and polarization state based on the specific pitch and structure direction of the mask pattern being exposed. The system automatically adjusts the illumination parameters according to the detected or pre-programmed pattern characteristics, eliminating the need for manual intervention and simplifying operation while maintaining high precision for different structures.
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 approach enhances the process window and reduces wavefront aberrations, leading to improved imaging quality and integration density, with fewer rejects in integrated circuit production, by effectively addressing structure- and pitch-dependent aberrations induced by the mask.
Implementation Method 1
wavefront manipulation using manipulators within the projection exposure apparatus, combined with adjustments in illumination settings and polarization, to compensate for mask-induced aberrations
Implementation Method 2
The type of illumination is designated as a setting. A distinction is made between coherent illumination, incoherent illumination with a a setting of between 0 and 1, annular illuminations, X- or Y-dipole settings with different, illuminated aperture angles, and quadrupole settings
Data Source
AI summary
The disclosure relates to a method for adapting a projection exposure apparatus for microlithography to a mask having structures with different pitches and/or different structure widths in different structure directions. Wavefront aberrations induced by the mask are reduced by a manipulator of the projection exposure apparatus for microlithography.