Cascaded Demultiplexer for Multi-Wavelength Lithographic Alignment
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Solution Overview
Problem
Lithographic alignment sensors face increased complexity and space constraints when adding multiple wavelengths, as each wavelength requires additional optical components that must be optically matched, complicating the multiplexer and demultiplexer systems.
Innovation Solution
A demultiplexing apparatus with multiple stages, where each stage doubles the number of demultiplexing components, allowing for efficient separation of radiation beams into unique wavelength channels without increasing the overall complexity or space requirements, using dichroic filters to divide beams into specific optical channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional wavelengths and polarizations are added to increase measurement reliability, then position measurement reliability is improved, but device complexity increases due to additional optical components
Solution Approach 1:
The patent segments the wavelength demultiplexing function into multiple cascaded stages, where each stage contains multiple demultiplexing components that work together to separate different wavelengths. This segmentation allows the system to handle multiple wavelengths systematically without requiring a single complex component, thereby improving measurement reliability while managing device complexity through modular architecture.
2Adaptability or versatility
If additional wavelengths are multiplexed into beams, then position measurement capability is improved, but multiplexer and demultiplexer complexity increases
Solution Approach 1:
The patent transitions from a single-stage demultiplexing approach to a multi-stage cascaded architecture, adding the dimension of sequential processing stages. Each stage processes a portion of the wavelength separation task, and the cascaded arrangement allows systematic handling of multiple wavelengths without proportionally increasing the complexity of individual components.
3Adaptability or versatility
If additional optical components are added to support multiple wavelengths, then wavelength diversity is improved, but space requirements increase
Solution Approach 1:
The patent implements a nested cascaded structure where multiple demultiplexing components are arranged in series stages. Each stage is contained within the overall demultiplexer assembly, and the cascaded configuration allows compact arrangement of multiple components. This nesting approach enables the system to support diverse wavelengths while minimizing the overall space footprint by efficiently packing components in a hierarchical manner.
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 the use of multiple wavelengths without increasing the alignment sensor's complexity or size, maintaining performance by efficiently separating and matching optical components within strict tolerances.
Implementation Method 1
using dichroic filters to divide beams into specific optical channels
Data Source
AI summary
A lithographic apparatus includes an alignment sensor configured to determine the position of an alignment target having a periodic structure. The alignment sensor includes a demultiplexer to demultiplex a number of intensity channels. The demultiplexer includes a number of stages arranged in series and a number of demultiplexing components, each demultiplexing component operable to divide an input radiation beam into two radiation beam portions. The first stage has a first demultiplexing component that is arranged to receive as an input radiation beam an incident radiation beam. Each successive stage is arranged such that it has twice the number of demultiplexing components as a preceding stage, each demultiplexing component of each stage after the first stage receiving as an input one of the radiation beam portions output from a demultiplexing component of the preceding stage.