Multi-Channel Detector for Lithography Speckle Quantification
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current lithography systems using pulsed laser illumination suffer from significant micro-nonuniformities, known as speckle, which affect the uniformity of critical dimensions (CD) in printed patterns and yield, but lack effective methods to quantify these nonuniformities, especially in production settings with stringent cleanliness requirements.
Innovation Solution
A multi-channel light detector system is placed in the mask plane to measure local light energy from individual laser pulses, with high lateral resolution, allowing for the quantification of micro-nonuniformities and their contribution to CD uniformity, and can be integrated into existing exposure systems with minimal impact, using cameras and metrology masks to record and analyze illumination patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current detectors for illumination uniformity are used, then the measurement system is simple and existing equipment can be used, but the lateral resolution is insufficient to quantify speckle-like micro-nonuniformities
Solution Approach 1:
The detector system is segmented into multiple independently controllable detector channels, each capable of measuring light energy at specific lateral positions. This segmentation enables high lateral resolution by assigning each channel to a specific spatial location, allowing the system to resolve micro-nonuniformities that would be averaged out in a single-detector system.
Solution Approach 2:
The invention transitions from measuring only the average light energy (scalar measurement) to measuring the spatial distribution of light energy across multiple positions (vector field measurement). By adding the spatial dimension to the measurement, the system can resolve micro-nonuniformities and speckle patterns while maintaining manageable system complexity through structured detector arrangement.
2Manufacturing precision
If multiple laser pulses are used to average out speckle, then the illumination uniformity improves, but the measurement time increases
Solution Approach 1:
The system performs preliminary measurements of the illumination pattern using multiple detector channels simultaneously, capturing the spatial distribution of micro-nonuniformities before the actual lithography process. This preliminary characterization allows the system to identify and compensate for speckle patterns without requiring time-consuming averaging during production, as the measurement infrastructure is prepared in advance.
Solution Approach 2:
The detector system provides real-time feedback on illumination uniformity by measuring the spatial distribution of light energy across multiple positions. This feedback enables dynamic adjustment of the illumination system or compensation algorithms to correct micro-nonuniformities, achieving high CD uniformity without requiring extensive averaging time, as corrections can be applied continuously during the measurement and exposure processes.
3Reliability
If the coherence of the laser light is increased, then the speckle effect is enhanced, but the control over the illumination pattern becomes more difficult
Solution Approach 1:
The multi-channel detector system acts as an intermediary between the coherent laser source and the lithography process. By measuring the actual illumination pattern produced by the coherent light, the system provides data that can be used to model and compensate for speckle effects. This intermediary measurement capability allows the system to maintain the reliability benefits of coherent light while gaining control through data-driven correction methods.
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 measurement and quantification of micro-nonuniformities, improving CD uniformity and yield by identifying and reducing speckle and interference-related issues, leading to faster, more reliable chip production.
Implementation Method 1
A camera is placed in a plane optically equivalent to a mask plane... recording pulse energy integrated on the channels
Data Source
AI summary
This disclosure relates to lithography using pulsed laser illumination. In particular it relates to lithography for producing electronic devices on wafers using multi-mode excimer and molecular lasers, e.g. KrF, ArF, and F2 lasers. It may also apply to illumination systems where several single-mode sources are mixed or one single-mode laser beam is split and recombined with time delays, thereby creating an equivalent multimode source and to EUV lithography. Particular aspects of the present invention are described in the claims, specification and drawings.