Optical Monitoring for Photomask Etch Rate Detection
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Solution Overview
Problem
The fabrication of photomasks for advanced technology faces challenges in achieving consistent etch rate data and process uniformity due to the complexity of design and ever-decreasing device dimensions, making it difficult to determine if desired etch results are obtained for specific photomasks.
Innovation Solution
A method and apparatus for enhanced process monitoring in photomask etching using optical monitoring at different regions of the photomask to obtain desired etch rate or thickness loss, involving a plasma etch chamber with optical access ports for detecting signals from covered and uncovered areas, allowing for real-time analysis of etch rate and endpoint determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical monitoring is implemented at different regions of the photomask, then etch rate detection precision is improved, but device complexity increases
Solution Approach 1:
The optical monitoring system is divided into multiple independent radiation sources and detection channels, each monitoring specific regions (covered and uncovered areas) of the photomask. This segmentation allows precise etch rate detection at different locations while maintaining modular system architecture that manages complexity.
Solution Approach 2:
The optical monitoring system performs multiple functions simultaneously: it monitors etch rate in covered areas, monitors etch rate in uncovered areas, and provides endpoint detection. By consolidating these functions into a integrated optical system, the patent achieves high measurement precision without proportionally increasing device complexity.
2Manufacturing precision
If multiple radiation sources are used to monitor different areas, then etch uniformity measurement is improved, but process complexity increases
Solution Approach 1:
Different radiation sources are directed at different regions of the photomask (covered vs. uncovered areas) to capture local etching characteristics. This local quality approach enables measurement of etch uniformity across the photomask surface by comparing signals from specific regions, improving manufacturing precision through localized monitoring.
Solution Approach 2:
The system collects signals from multiple radiation sources simultaneously and analyzes them to determine etch rate and endpoint. The feedback from multiple channels provides comprehensive information about etch uniformity, allowing real-time process control and adjustment to maintain manufacturing precision.
3Reliability
If real-time optical monitoring is implemented, then process control is improved, but energy consumption increases
Solution Approach 1:
The optical monitoring system operates continuously during the etching process, providing real-time data for process control. By maintaining continuous monitoring rather than intermittent measurements, the system ensures reliable process control while optimizing energy usage through sustained operational efficiency.
Solution Approach 2:
The optical monitoring system uses the existing plasma environment and photomask structure to perform self-diagnosis and process characterization. The system leverages the natural optical properties of the etching process and materials, reducing the need for additional energy-intensive measurement equipment while maintaining reliable process control.
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 provides improved process control and reliable etch rate/loss of thickness monitoring, enabling consistent results across different photomasks and optimizing etching processes for advanced technology applications.
Implementation Method 1
etching a first substrate through a patterned mask layer in a plasma etch chamber
Implementation Method 2
the underlying material layer is exposed to a reactive environment, e.g., using wet or dry etching, which results in the pattern being transferred to the underlying material layer
Implementation Method 3
directing a first radiation source from the backside of the first substrate to a first area covered by the patterned mask layer, directing a second radiation source from the backside of the first substrate to a second area uncovered by the patterned mask layer, collecting a first signal reflected from the first area covered by the patterned mask layer, collecting a second signal reflected from the second area uncovered by the patterned mask layer
Data Source
AI summary
The present invention provides a method and apparatus for etching a photomask substrate with enhanced process monitoring, for example, by providing for optical monitoring at different regions of the photomask to obtain desired etch rate or thickness loss. In one embodiment, the method includes etching a first substrate through a patterned mask layer in a plasma etch chamber, the first substrate having a backside disposed on a substrate support and a front side facing away from the substrate support, directing a first radiation source from the backside of the first substrate to a first area covered by the patterned mask layer, directing a second radiation source from the backside of the first substrate to a second area uncovered by the patterned mask layer, collecting a first signal reflected from the first area covered by the patterned mask layer, collecting a second signal reflected from the second area uncovered by the patterned mask layer, and analyzing the combined first and the second signal.