Microlithography Illumination System Irradiance Adjustment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current microlithographic illumination systems face challenges in finely adjusting spatial irradiance distribution without incurring significant light losses, which can lead to variations in critical dimensions and image quality due to field-dependent angular irradiance distributions.
Innovation Solution
An illumination system utilizing a spatial light modulator with a light splitter to direct a significant portion of the projection light along a non-modulation path, minimizing interactions with the spatial light modulator, while using a spatial light modulator only in the modulation path to adjust the irradiance distribution, thereby reducing light losses and maintaining optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the projection light is fully modulated by the spatial light modulator to adjust irradiance distribution, then the irradiance adjustment precision is improved, but the light loss increases significantly
Solution Approach 1:
The patent segments the projection light into two separate paths: a modulation light path where light is modulated by the spatial light modulator to adjust irradiance distribution, and a non-modulation light path where light passes through without modulation. This segmentation allows only the necessary portion of light to be modulated, reducing overall light loss while maintaining irradiance adjustment precision through the modulated component.
Solution Approach 2:
The patent applies local quality by selectively modulating only the portion of light that requires irradiance adjustment, rather than uniformly modulating all projection light. The spatial light modulator is positioned to modulate specific light bundles, creating locally optimized irradiance distribution without subjecting the entire light field to modulation losses.
2Ease of operation
If the spatial light modulator is positioned to modulate all projection light, then the irradiance distribution control is improved, but the light loss and adverse effects on light properties increase
Solution Approach 1:
The illumination system is segmented into distinct optical paths: one containing the spatial light modulator for controlled modulation and another excluding it for unmodulated light transmission. This allows irradiance distribution control through the modulated path while preserving light properties in the non-modulated path, reducing overall light loss.
Solution Approach 2:
The patent introduces an intermediary optical configuration where the spatial light modulator acts as a selective mediator rather than a universal one. By positioning the modulator to intercept only specific light bundles, it mediates irradiance adjustment locally without forcing all light through the modulation process, thereby reducing adverse effects on light properties.
3Manufacturing precision
If a conventional illumination system modulates all light to achieve uniform irradiance, then the manufacturing precision is improved, but the productivity decreases due to light losses
Solution Approach 1:
The patent segments the illumination system into modulated and non-modulated light paths, allowing critical dimension control through precise irradiance adjustment in the modulated path while maintaining high exposure throughput by preserving the full intensity of unmodulated light. This segmentation enables manufacturing precision without sacrificing productivity.
Solution Approach 2:
The patent changes the parameter of light modulation from a binary all-or-nothing approach to a selective partial modulation approach. By adjusting which light bundles undergo modulation and to what extent, the system optimizes both critical dimension control (through precise irradiance adjustment where needed) and exposure throughput (by minimizing unnecessary modulation of other light bundles).
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
Enables precise adjustment of spatial irradiance distribution with minimal adverse effects on the light, reducing light losses and maintaining image quality by directing most of the light along a non-modulation path and using the spatial light modulator only for necessary adjustments.
Implementation Method 1
a light splitter that splits the projection light into modulated light that propagates along a modulation light path and non-modulated light that propagates along a non-modulation light path
Implementation Method 2
The spatial light modulator has an array of light deflection elements that are configured to be individually controlled and is arranged in the modulation light path to modulate the modulated light
Implementation Method 3
The modulated light and the non-modulated light superimpose on the surface
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An illumination system of a microlithographic projection apparatus (10) comprises an irradiance adjustment unit (52) that adjusts an irradiance distribution of projection light on a surface (S). The irradiance adjustment unit (52) comprises a spatial light modulator (54a, 54b; 154) having an array of light deflection elements (55) and a light splitter (56a, 56b; 56; 156a) that splits the projection light into modulated light (58a, 58b; 158) that propagates along a modulation light path (59a, 59b; 159) and non-modulated light (60a, 60b; 160a, 160c, 160d) that propagates along a non-modulation light path (63; 163a, 163c, 163d). The spatial light modulator (54a, 54b; 154) is only arranged in the modulation light path (59a, 59b; 159), but not in the non- modulation light path (63; 163a, 163c, 163d). The modulated light (58a, 58b; 158) and the non-modulated light (60a, 60b; 160a, 160c, 160d) superimpose on the surface.