Gas Flow Measurement in Common Supply Paths With Low Line Dependency

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Solution Overview

Problem

Conventional flow rate measurement methods in gas supply systems for semiconductor manufacturing are not accurate across multiple gas supply paths due to line dependency, leading to measurement errors.

Innovation Solution

A flow rate measuring method and device that utilize a common gas supply path with pressure and temperature sensors, and valves to calculate flow rates by measuring pressure and temperature changes before and after valve closures, reducing line dependency and enhancing accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional build-up method is used for flow rate measurement, then flow rate can be calculated using pressure rise rate, but measurement accuracy deteriorates due to line dependency in multi-path gas supply systems

Engineering Contradiction:

Improveflow rate measurement accuracyVSAvoidline dependency

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The gas supply system is segmented into multiple independent measurement paths, each with its own first valve. The common path contains a second valve. By selectively opening/closing specific first valves, flow rate can be measured for individual gas supply paths or in combination, eliminating line dependency effects that plague conventional single-path measurement methods.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The common gas supply path serves multiple functions: it acts as the measurement path for all gas supply paths simultaneously, houses shared sensors (pressure, temperature) and the second valve, and enables both individual and combined flow rate measurements. This multi-functional design resolves the line dependency problem while maintaining measurement accuracy across all paths.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Productivity

If multiple gas supply paths are measured using conventional build-up method, then flow rate control is achieved, but measurement errors increase due to line dependency

Engineering Contradiction:

Improveflow rate control capabilityVSAvoidflow rate measurement accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

Pressure sensors and temperature sensors provide real-time feedback on the state of gas in the common path. The control unit uses this feedback to calculate flow rates accurately by monitoring pressure rise rates and temperature changes, compensating for line dependency effects and enabling precise flow rate control across multiple gas supply paths.

Inventive Principle:

Principle #23Feedback

3Measurement precision

If pressure and temperature are measured after valve closure, then flow rate can be calculated, but measurement accuracy is insufficient for large flow rates in multi-path systems

Engineering Contradiction:

Improveflow rate calculation accuracyVSAvoidapplicability to large flow rates

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The first valves are closed after a predetermined time has elapsed since the second valve was closed. This preliminary timing action ensures that the measurement is taken at the optimal moment when pressure and temperature changes are most indicative of the actual flow rate, improving accuracy for large flow rates while accounting for the dynamics of multi-path gas supply systems.

Inventive Principle:

Principle #10Preliminary action

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 method allows for high-accuracy flow rate measurement across multiple gas supply paths, reducing measurement errors and ensuring precise flow control, even at large flow rates.

Implementation Method 1

measuring the rate of rise in the pressure (ΔP/Δt)

Methodology Applied

Scientific EffectPressure measurement:

Implementation Method 2

measuring the rate of rise in the pressure (ΔP/Δt) and the temperature (T)

Methodology Applied

Scientific EffectTemperature measurement:

Implementation Method 3

by flowing a gas through a predetermined reference volume (V) provided downstream of the flow rate control device

Methodology Applied

Scientific EffectGas flow:

Data Source

PatentUS11326921B2Flow rate measuring method and flow rate measuring device

Publication Date: 2022.05.10 FUJIKIN INC

AI summary

The flow rate measuring method is performed in a common gas supply system comprising a plurality of gas supply paths each having a first valve, and a gas measuring device formed downstream side of the plurality of gas supply paths, having a pressure sensor, a temperature sensor, and a downstream side second valve. The flow rate measuring method includes: a first step of opening any one of the first valves and the second valve to allow gas to flow, closing the second valve while gas is flowing, and closing the first valve after a predetermined time has elapsed, and then measuring a pressure and a temperature after the first valve has been closed; a second step of opening any one of first valves and the second valve to allow gas to flow, closing the any one of the first valve and the second valve at the same time while gas is flowing, and then measuring a pressure and temperature after the first valve and the second valve have been closed; and a third step of calculating the flow rate in accordance with the pressure and temperature measured in the first step and the pressure and temperature measured in the second step.