Mass Flow Verifier with Dual-Mode Rate-of-Rise and Critical Flow Nozzle
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Solution Overview
Problem
Existing mass flow verifiers are limited in their ability to accurately verify fluid delivery over a wide range of flow rates without requiring a large footprint, especially for low flow rates, and struggle with unknown gases or gas mixtures, leading to inefficiencies and inaccuracies in semiconductor fabrication processes.
Innovation Solution
A mass flow verifier that combines rate-of-rise measurement techniques and critical flow nozzle methods, using multiple pressure sensors and a controller to calculate flow rates and determine gas property functions, allowing for adaptable measurement strategies across various flow ranges and gas types, including the selection between rate-of-rise and critical flow nozzle measurements based on flow rates and gas properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large chamber volume is used to improve low flow rate measurement accuracy, then measurement precision improves, but device footprint increases
Solution Approach 1:
The patent implements a dual-mode measurement system that dynamically selects between rate-of-rise measurement (for low flow rates) and critical flow nozzle measurement (for high flow rates). This dynamic adaptation allows the system to maintain high measurement precision across the entire flow range without requiring a large chamber volume, as each mode is optimized for its specific flow range.
Solution Approach 2:
The system changes measurement parameters based on flow rate conditions. For low flow rates, it uses rate-of-rise measurement with chamber pressure monitoring. For high flow rates, it switches to critical flow nozzle measurement with upstream pressure monitoring. This parameter change allows accurate measurement across wide flow ranges without increasing chamber volume.
2Measurement precision
If rate-of-rise measurement is used for low flow rates, then measurement precision improves, but gas property variations cause inaccuracies
Solution Approach 1:
The patent creates a universal measurement system that can handle both known and unknown gases across all flow ranges. By combining rate-of-rise measurement with critical flow nozzle measurement and gas property function determination, the system becomes multi-functional and adaptable to different gas types, eliminating the limitation of rate-of-rise measurement with unknown gases.
Solution Approach 2:
The system introduces gas property functions as an intermediary that bridges the gap between different measurement modes and gas types. By determining gas property functions from critical flow nozzle measurements and using them in rate-of-rise measurements, the system mediates the incompatibility between measurement precision and gas type adaptability.
3Productivity
If critical flow nozzle is used for high flow rates, then measurement speed improves, but low flow rate measurement capability deteriorates
Solution Approach 1:
The patent segments the flow rate measurement range into two distinct segments: low flow rates handled by rate-of-rise measurement and high flow rates handled by critical flow nozzle measurement. This segmentation allows each measurement mode to be optimized for its specific range, maintaining measurement precision at low flow rates while achieving high measurement speed at high flow rates.
Solution Approach 2:
The system dynamically switches between measurement modes based on the detected flow rate. When flow rate is low, it uses rate-of-rise measurement for accuracy. When flow rate is high, it switches to critical flow nozzle measurement for speed. This dynamic adaptation resolves the contradiction between measurement speed and low flow rate capability.
4Measurement precision
If separate measurement systems are used for different flow ranges, then measurement accuracy across ranges improves, but device complexity increases
Solution Approach 1:
The patent merges the rate-of-rise measurement system and critical flow nozzle measurement system into a single integrated mass flow verifier. The controller combines both measurement modes and gas property function determination into one unified system, allowing accurate flow rate verification across all ranges while avoiding the complexity of completely separate measurement systems.
Solution Approach 2:
The system is designed as a universal measurement platform that performs multiple functions: rate-of-rise measurement, critical flow nozzle measurement, and gas property function determination. This multi-functionality reduces overall system complexity compared to having separate dedicated systems for each measurement type.
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 enables accurate verification of flow rates across a wide range of flow rates, from low to high, without interrupting gas delivery, and improves measurement precision by determining gas properties, thus enhancing the operational efficiency and accuracy of mass flow verification in semiconductor fabrication systems.
Implementation Method 1
The critical flow nozzle and the flow verification process are configured to maintain the flow rate of the fluid through the nozzle at the critical flow condition such that the flow rate through the nozzle is substantially constant and substantially insensitive to any variation in pressure within the chamber downstream of the nozzle
Implementation Method 2
measuring a first flow rate based on a rate of rise in pressure of the fluid as detected by the first pressure sensor
Implementation Method 3
measuring a second flow rate based on upstream pressure detected by the second pressure sensor
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
A mass flow verifier (MFV) that is space-efficient and can verify flow rates for unknown fluids over a wide range of flow rates includes a chamber configured to receive a fluid, a critical flow nozzle connected to the chamber, and first and second pressure sensors that, respectively, detect fluid pressure in the chamber and upstream of the critical flow nozzle. A controller of the MFV is configured to verify flow rate of the fluid by, (i) at a first flow range, measuring a first flow rate based on a rate of rise in pressure of the fluid as detected by the first pressure sensor and determining a gas property function of the fluid based on pressures as detected by the first second pressure sensors, and (ii) at a second flow range, measuring a second flow rate based on pressure detected by the second pressure sensor and the determined gas property function.