Mass Flow Controller Gas Concentration Thermal Sensor
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Solution Overview
Problem
The precision delivery of a gas in processing environments, such as plasma processing, is hindered by the difficulty in determining the concentration of a processing gas within a gas stream due to mixing with a carrier gas, which affects mass flow rate control.
Innovation Solution
A system comprising a mass flow controller with a thermal mass flow sensor and gas concentration meter that uses upstream and bridge-derived temperature signals to calculate the concentration of the processing gas, enabling precise control of the processing gas mass flow rate through a control valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a vaporizer is used to vaporize a source substance into a processing gas and a pressurized carrier gas is used to force the processing gas to the process environment, then the processing gas can be delivered to the process environment, but the concentration of the processing gas becomes difficult to determine due to mixing with the carrier gas
Solution Approach 1:
The patent introduces a thermal mass flow sensor as an intermediary device that measures the heat transfer properties of the gas stream. By using the sensor as a mediator between the mixed gas stream and the control system, the concentration of processing gas can be determined indirectly through thermal measurements without requiring direct chemical analysis of the mixed stream.
Solution Approach 2:
The patent replaces direct chemical or compositional measurement methods with a thermal measurement approach. Instead of using complex analytical instruments to determine gas concentration, a thermal mass flow sensor uses heat transfer principles to infer processing gas concentration from the thermal properties of the mixed carrier gas and processing gas stream.
2Productivity
If the concentration of processing gas is difficult to determine due to mixing with carrier gas, then gas delivery can proceed, but the mass flow rate control precision deteriorates
Solution Approach 1:
The patent implements a feedback control system where the thermal mass flow sensor continuously measures the processing gas concentration and feeds this information back to the controller. The controller adjusts the carrier gas flow or processing gas vaporization rate based on the measured concentration, creating a closed-loop system that maintains precise mass flow rate control despite the mixing of gases.
Solution Approach 2:
The patent substitutes direct mass flow measurement of the mixed gas stream with thermal measurement-based inference. By measuring thermal properties and using calculations based on known carrier gas and processing gas characteristics, the system achieves precise mass flow rate control without requiring direct measurement of the mixed stream composition.
3Length of moving object
If structure dimensions continue to diminish in size, then processing capability increases, but the precision requirement for mass flow rate increases
Solution Approach 1:
The feedback control system continuously monitors processing gas concentration and adjusts flow parameters in real-time, enabling precise mass flow rate control that is essential for processing ever-smaller structures. The closed-loop control compensates for variations and maintains the required precision as structure dimensions decrease.
Solution Approach 2:
The system dynamically adjusts flow parameters such as carrier gas pressure, vaporization temperature, and flow rates based on real-time measurements. By changing these parameters adaptively, the system maintains precise mass flow rate control required for processing smaller and smaller structures with diminishing tolerance margins.
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 system accurately measures and controls the concentration of the processing gas in the gas stream, ensuring precise mass flow rates, which is critical as structure dimensions decrease, enhancing the precision of processing operations.
Implementation Method 1
A thermal mass flow sensor is coupled to the main flow path, and the thermal mass flow sensor is configured to provide a bridge-derived temperature signal indicative of a bridge-derived temperature and a gas-stream-flow-rate signal indicative of a mass flow rate of the gas stream
Data Source
AI summary
Systems and method for detecting a concentration of a gas in a gas stream are disclosed. A method includes receiving a gas stream including a carrier gas and a processing gas. Bridge signals of a mass flow sensor are used to produce a processing-gas concentration signal and a gas-stream mass flow rate signal. The gas stream is controlled so a mass flow rate of the processing gas equals a processing-gas-setpoint signal. In some variations, the processing-gas-concentration signal is produced using an upstream temperature of the gas stream and a bridge-derived temperature.