Gas Flow Control Apparatus In-Situ Calibration Using Reference Gas
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Solution Overview
Problem
Current mass flow control technologies in semiconductor fabrication face challenges in achieving accurate and rapid calibration, especially for hazardous gases, which requires costly abatement systems and specialized facilities or equipment, leading to increased downtime and inefficiency.
Innovation Solution
A method for in-situ calibration of gas flow control apparatuses using a reference gas to determine the volume of a gas box and create a gas map for process gases, allowing for precise control and reduced calibration time without the need for purge cycles or specialized equipment, by measuring pressure and flow rates within the apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional calibration methods using hazardous gases are employed, then calibration accuracy can be achieved, but costly abatement systems and specialized facilities are required, leading to increased equipment costs and downtime
Solution Approach 1:
The patent uses a reference gas (non-hazardous) as an intermediary substance to perform calibration that would traditionally require hazardous gases. The reference gas flows through the same flow path and interacts with the same sensors, allowing indirect calibration of the hazardous gas measurement system without actually introducing hazardous substances, thereby eliminating the need for expensive abatement systems while maintaining calibration accuracy
Solution Approach 2:
The patent creates a copy of the calibration process using a reference gas that mimics the flow characteristics of hazardous gases but without the associated dangers. By measuring pressure differential responses to the reference gas and using these measurements to generate calibration data, the system replicates the essential calibration function without requiring actual hazardous gas handling infrastructure
2Measurement precision
If traditional calibration methods are used, then calibration can be performed, but purge cycles are required, increasing calibration time and reducing productivity
Solution Approach 1:
The calibration system performs self-calibration by using the reference gas to automatically generate calibration data through pressure differential measurements. The system controller automatically processes the measurements and generates calibration coefficients without requiring external intervention or time-consuming purge cycles, enabling rapid recalibration during normal operation
Solution Approach 2:
The patent enables calibration to be performed continuously during normal operation without interrupting the gas flow or requiring purge cycles. The reference gas is introduced alongside or in place of process gas, allowing calibration measurements to be taken continuously, thereby maintaining productivity while ensuring measurement accuracy
3Measurement precision
If hazardous gas calibration is performed, then accurate gas map data can be obtained, but specialized facilities and abatement systems are needed, increasing system complexity
Solution Approach 1:
The reference gas acts as an intermediary that allows the system to obtain accurate gas map data without directly using hazardous gases. The pressure differential measurements taken with the reference gas provide sufficient information to generate accurate calibration coefficients and gas maps, eliminating the need for specialized hazardous gas handling facilities
Solution Approach 2:
The patent replaces the mechanical/chemical requirement for hazardous gas abatement systems with a measurement-based approach using pressure differential sensors and computational algorithms. By substituting the need for physical hazardous gas handling infrastructure with electronic sensing and data processing, the system achieves the same calibration objective without the associated facility requirements
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 and efficient calibration of gas flow control systems, minimizing downtime and equipment costs by utilizing existing instrumentation and avoiding the need for hazardous gas abatement systems, while ensuring precise control and consistency in gas delivery.
Implementation Method 1
A pressure transducer measures the pressure within the gas box as the reference gas is provided to the gas box
Implementation Method 2
a valve in the gas flow path, a characterized flow restrictor in the gas flow path
Data Source
AI summary
Apparatuses for controlling gas flow are important components for delivering process gases for semiconductor fabrication. In one embodiment, a method of calibrating an apparatus for controlling gas flow is disclosed. Specifically, the apparatus may be calibrated on installation using a two-step process of measuring the volume of gas box downstream from the apparatus by flowing nitrogen gas into the gas box and measuring the resulting temperature and rate of pressure rise. Using the computed volume of the gas box, a sweep of several mass flow rates may be performed using the process gas and the gas map for the process gas. The apparatus is calibrated based on the measured temperature and pressure values, which allow calculation of the actual mass flow rate for the process gas as compared with the commanded mass flow rates.