Cylindrical Multipass Cell for Compact IR Monitoring
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Solution Overview
Problem
Existing fluid monitoring systems face challenges in achieving a balance between long path lengths for sensitive detection and compact, small-volume configurations, particularly in applications like semiconductor manufacturing where space is limited, while maintaining efficient optical coupling and manufacturability.
Innovation Solution
A multipass cell assembly with an arcuate or cylindrical circumscribing member featuring inwardly facing reflective surfaces, allowing for multiple reflections of light within a compact optical reflection chamber, which extends the optical path length while maintaining a small sample volume, and includes a light input structure, output structure, fluid inlet, and outlet for interaction with the fluid stream.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a long path length is used for optical monitoring, then measurement sensitivity is improved, but the device volume increases
Solution Approach 1:
The patent transitions from a linear one-dimensional optical path to a multi-dimensional path by introducing multiple reflections between mirrors. The optical beam traverses the sample cell multiple times in different directions, effectively extending the path length from a single straight line to a complex three-dimensional trajectory, achieving long path length in a compact volume
Solution Approach 2:
The patent implements a nested configuration where multiple optical passes are contained within a single compact cell structure. The light beam performs multiple reflections between mirrors positioned within the cell, nesting multiple interaction paths within the physical boundaries of one sample cell, thereby achieving extended path length without proportional volume increase
2Measurement precision
If multiple reflections are implemented to extend path length, then measurement sensitivity improves, but device complexity increases
Solution Approach 1:
The cylindrical or arcuate wall structure serves multiple functions simultaneously: it provides the physical boundaries of the sample cell, acts as a support structure for the mirrors, and creates the geometric configuration necessary for multiple optical reflections. This multi-functionality reduces the need for separate components, thereby managing complexity while achieving extended path length
Solution Approach 2:
The patent employs curved cylindrical or arcuate walls instead of flat surfaces, creating a geometry that naturally facilitates multiple reflections. The curved geometry allows the optical beam to bounce between mirrors and walls in a controlled manner, achieving multiple passes without requiring complex mirror positioning mechanisms or adjustable components
3Volume of stationary object
If a compact form factor is used to reduce volume, then space utilization improves, but optical coupling efficiency deteriorates
Solution Approach 1:
The mirrors are pre-positioned and fixed at specific angles and locations within the cell during manufacturing, establishing the optical path geometry before the device is put into service. This preliminary configuration ensures that the compact cell design inherently provides the necessary optical coupling efficiency without requiring complex alignment procedures or adjustable 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
The multipass cell assembly enhances measurement sensitivity by extending the optical path length, reduces sample volume requirements, and achieves efficient optical signal utilization, while maintaining a compact form factor suitable for space-constrained applications like semiconductor manufacturing.
Implementation Method 1
multi-pass optical reflection chamber... inwardly facing reflective surface... generates multipass optical reflection of light impinged thereon
Implementation Method 2
infrared radiation is passed through a sample cell to interact with a fluid stream flow through the cell... the transmitted or reflected signal passes out of the sample cell and impinges on an infrared detector
Data Source
AI summary
A multipass cell assembly for monitoring of fluid is described, as well as fluid processing systems utilizing same, and associated methods of use of such multipass cell assembly for fluid monitoring. The multipass cell assembly is usefully employed in fluid processing operations such as monitoring of vapor deposition process reactants, e.g., reactants used for vapor deposition metallization of tungsten from a tungsten carbonyl precursor.