Mirror Array for EUV Mask Characterization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Microlithography mask characterization in projection illumination apparatuses is hindered by the inability to rapidly and reliably analyze defects due to limitations in existing inspection methods, particularly with EUV light sources that cannot switch on and off quickly, and the need for precise illumination control.
Innovation Solution
A method and apparatus utilizing a mirror array with independently adjustable mirror elements to outcouple light from the beam path, allowing for defined illumination times and intensity detection, enabling the differentiation of mask defects from light source fluctuations and achieving greyscale adjustments and beam path separation without high-speed shutters or transmissive materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If EUV light source is used for mask characterization, then measurement precision is improved, but the light source cannot switch on and off quickly enough for rapid defect analysis
Solution Approach 1:
A mirror array is introduced as an intermediary component between the EUV light source and the mask. The mirror elements can be independently tilted to control light reflection, effectively acting as a shutter without requiring the light source itself to switch rapidly. This mediator enables precise control of illumination timing while maintaining the benefits of EUV light for high-resolution imaging.
Solution Approach 2:
The mirror elements are made dynamically adjustable through tilting mechanisms that allow each mirror element to change its orientation independently. This dynamic control enables rapid switching of light paths, allowing the system to achieve fast effective shuttering speeds even though the light source itself remains continuously operating. The dynamic mirror array resolves the contradiction by decoupling light source operation from illumination control.
2Duration of action of moving object
If high-speed shutter is used to control illumination time, then illumination time control is improved, but device complexity increases
Solution Approach 1:
The patent replaces traditional mechanical high-speed shutter mechanisms with a mirror array system controlled by tilting mechanisms. Instead of using complex mechanical shutters that open and close rapidly, the system uses electronically controlled mirror tilting to redirect light paths. This substitution reduces mechanical complexity while achieving the same illumination time control function through optical path management.
3Ease of operation
If transmissive materials are used for beam path control, then ease of operation is improved, but manufacturing precision requirements increase due to material limitations at EUV wavelengths
Solution Approach 1:
The patent replaces transmissive optical materials with reflective mirror elements for beam path control. At EUV wavelengths, transmissive materials require extremely high manufacturing precision to avoid scattering and absorption losses. By using reflective mirrors, the system achieves beam path control without the stringent fabrication requirements of transmissive materials, while maintaining ease of operation through mirror tilting mechanisms.
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 fast and reliable microlithography mask characterization by normalizing image data to light source energy fluctuations, avoiding incorrect defect identification and allowing for precise greyscale adjustments and vertical incidence illumination, thus improving the accuracy of defect detection in microlithography processes.
Implementation Method 1
at least intermittently, a portion of the light emitted by the light source is outcoupled from the used beam path by use of a mirror array having a multitude of independently adjustable mirror elements
Implementation Method 2
wherein, intermittently by use of the mirror array, all light is outcoupled from the used beam path for establishment of a defined illumination time of the sensor unit
Data Source
AI summary
The invention relates to a method and an apparatus for characterizing a microlithography mask. In one aspect, in a method according to the invention, the mask to be characterized is illuminated with light from a light source via an illumination optics unit, said light having a wavelength of less than 30 nm, wherein light that passes in a used beam path from the light source via the mask to a sensor unit is evaluated, wherein, at least intermittently, a portion of the light emitted by the light source is outcoupled from the used beam path by use of a mirror array having a multitude of independently adjustable mirror elements, and wherein, intermittently by use of the mirror array, all light is outcoupled from the used beam path for establishment of a defined illumination time of the sensor unit.