Diffractive Optical Element Displacement for Microlithography Illumination
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Solution Overview
Problem
Current microlithographic illumination systems face limitations in producing continuously variable irradiance distributions in the pupil plane, with existing methods such as diffractive optical elements offering restricted flexibility due to limited degrees of freedom, leading to inefficiencies and light losses.
Innovation Solution
The use of two or more diffractive optical elements with a displacement mechanism to change their mutual spatial arrangement, allowing for independent variation of irradiance distributions by overlapping or superimposing their effects, thereby increasing the range of possible irradiance distributions and reducing sensitivity to light source fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single diffractive optical element is used to define irradiance distribution in the pupil plane, then the system structure remains simple, but the flexibility and range of possible irradiance distributions are limited
Solution Approach 1:
The illumination system divides the single diffractive optical element into multiple separate diffractive optical elements (at least two). Each element can be independently positioned and adjusted, allowing the system to generate a broader range of irradiance distributions by combining their effects. This segmentation enables greater adaptability without requiring each individual element to be overly complex.
Solution Approach 2:
The patent introduces an additional spatial dimension by arranging multiple diffractive optical elements in different positions within the illumination path. By controlling the mutual spatial arrangement of these elements, the system expands the degrees of freedom for defining irradiance distributions, effectively adding a dimensional aspect to the control mechanism.
2Productivity
If conventional illumination settings are used, then the system operation remains simple, but light losses occur and efficiency is reduced
Solution Approach 1:
The system transitions from static conventional illumination settings to a dynamic configuration using multiple diffractive optical elements with adjustable spatial arrangements. This dynamic capability allows the system to optimize light distribution in real-time, directing more light effectively to the mask and reducing losses, thereby improving overall illumination efficiency and productivity.
3Ease of operation
If the spatial arrangement of diffractive optical elements is fixed, then the system structure remains stable, but the ability to finely adjust illumination settings is restricted
Solution Approach 1:
The system incorporates a displacement mechanism that enables dynamic adjustment of the mutual spatial arrangement of the diffractive optical elements. This allows operators to finely tune the illumination settings by adjusting element positions, achieving precise control over irradiance distributions while maintaining a relatively stable overall system structure.
Solution Approach 2:
The patent replaces complex mechanical adjustment systems with a more streamlined displacement mechanism that specifically targets the positioning of diffractive optical elements. This substitution simplifies the overall mechanical complexity while enhancing the precision of illumination adjustments through controlled spatial reconfiguration of the optical elements.
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 flexibility and stability of irradiance distribution control in the pupil plane, reducing light losses and improving the ability to finely adjust illumination settings, while maintaining high precision and efficiency.
Implementation Method 1
an irradiance distribution of projection light in a pupil plane depends on diffractive effects produced by the diffractive optical elements
Data Source
AI summary
An illumination system of a microlithographic projection exposure apparatus includes a light source to produce projection light beam, and a first and a second diffractive optical element between the light source and a pupil plane of the illumination system. The diffractive effect produced by each diffractive optical element depends on the position of a light field that is irradiated by the projection light on the diffractive optical elements. A displacement mechanism changes the mutual spatial arrangement of the diffractive optical elements. In at least one of the mutual spatial arrangements, which can be obtained with the help of the displacement mechanism, the light field extends both over the first and the second diffractive optical element. This makes it possible to produce in a simple manner continuously variable illumination settings.