Microlithography Illumination System with Raster Module and Micro Mirror Array
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Solution Overview
Problem
Existing illumination optical systems for microlithography lack the ability to precisely control illumination intensity over the object field, particularly in terms of total intensity and directional intensity distributions, which is crucial for demanding projection tasks.
Innovation Solution
The system employs a raster module with two-stage raster arrangements and a micro mirror array controlled by a controller to adjust the tilting angles of individual mirrors, allowing for targeted manipulation of illumination light angles and intensity distributions across the object field, leveraging the dependency of emergent angles on incidence angles to achieve desired field-dependent optical effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional illumination optical system is used, then the system structure is simple, but the ability to control illumination intensity and directional distribution over the object field is insufficient
Solution Approach 1:
The illumination optical system is segmented into multiple functional modules: a micro mirror array with individually controllable mirrors, a raster module with two-stage raster arrangements, and a controller. Each module performs a specific function in manipulating illumination light properties, enabling precise control of intensity and directional distribution across different regions of the object field through coordinated operation of these segmented components.
Solution Approach 2:
The system employs dynamic control elements including a micro mirror array where each mirror can be independently tilted to different angles, and a raster module that can be positioned at different locations. The controller dynamically adjusts the tilting angles of individual mirrors and the position of the raster module in real-time to achieve desired illumination patterns, transforming a static system into a dynamically adaptable one.
2Adaptability or versatility
If the raster module is used to control illumination angles, then the directional intensity distribution is improved, but the system complexity increases due to additional components and control mechanisms
Solution Approach 1:
The raster module serves multiple functions within the illumination system: it acts as a beam splitter, a spatial filter, and an angle control element. By positioning the raster module at different locations and adjusting its orientation, the system can achieve various illumination patterns and angle distributions, making this single component a multi-functional element that reduces the need for separate dedicated components for each function.
Solution Approach 2:
The controller receives information about the desired illumination pattern and calculates the appropriate tilting angles for each mirror in the micro mirror array and the positioning of the raster module. This closed-loop control approach allows the system to automatically adjust its parameters to achieve the target illumination characteristics, reducing manual intervention and simplifying the overall control 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
This approach enables precise control of illumination angles and intensity distributions, allowing for high-precision imaging of objects with varying structural designs, enhancing the ability to define field edges and intensity distributions, thereby improving the overall performance of microlithography projection exposure systems.
Implementation Method 1
an illumination optical system (7) with a micro mirror array (10) having a large number of individually tiltable mirrors (11)
Implementation Method 2
The illumination optical system (7) can make use of the aberrations of spherical surfaces of light-guiding raster elements of the raster arrangements of the raster module (19)
Data Source
Figure 1
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Figure 3~4
AI summary
An illumination optical system (7) for microlithography is used to guide illumination light (8) from a primary light source (6) to an object field (3). A mirror array (10) of the illumination optical system (7) has a plurality of individual mirrors (11), which can be tilted independently of one another by actuators and are connected to associated tilting actuators (12).A controller (14) is used to activate the actuators (12).A raster module (19) of the illumination optical system (7) has a plurality of raster elements (28, 30) to produce a spatially distributed arrangement of secondary light sources. The raster module (19) is arranged in the region of a plane (20) of the illumination optical system (7), in which an emergent angle (ARx ), at which an illumination light part bundle (15) leaves one of the raster elements (30), is precisely allocated to a location region in the object field (3), on which the illumination light part bundle (15) impinges on the object field (3).The controller (14) is configured in such a way that a specification of a tilting angle for each individual mirror (11) is allocated to a predetermined desired course of illumination angle intensity distributions, with which object field points distributed over the object field (3) are impinged upon. The raster module (19), depending on the respective actual angle of incidence, produces another intensity course in the object field (3). The result is an illumination optical system, in which an illumination intensity over the object field can be influenced in a targeted manner with respect to the total illumination intensity and/or with respect to the intensity contributions from different illumination directions.