Gas Flow Metrology Calibration for Chamber Flow Matching
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Solution Overview
Problem
Existing flow metrology systems in substrate processing systems face challenges in achieving accurate and repeatable flow rate measurements due to factors such as orifice geometric variations, gas property differences, and sensor calibration inaccuracies, leading to unit-to-unit reproducibility issues.
Innovation Solution
A method for calibrating gas flow metrology systems involves measuring temperature and pressure using reference sensors, performing flow rate measurements with both the metrology system and a reference system, and determining transfer functions for different calibration gases. This method accounts for orifice geometric variations and gas property differences, allowing for accurate scaling and interpolation for various gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flow rate measurements are performed using existing metrology systems, then flow rate verification is achieved, but unit-to-unit reproducibility is poor due to orifice geometric variations and sensor calibration inaccuracies
Solution Approach 1:
The patent applies parameter changes by introducing temperature and pressure scaling factors that adjust the operating conditions of the metrology system. By measuring temperature and pressure and applying scaling functions, the system compensates for environmental variations that cause measurement drift, thereby improving both reliability and precision of flow rate measurements across different units.
Solution Approach 2:
The patent implements feedback mechanisms by continuously monitoring temperature and pressure parameters and using this information to adjust flow rate measurements in real-time. The scaling functions act as feedback loops that correct measurement deviations caused by environmental changes, sensor variations, and orifice geometric differences, significantly improving unit-to-unit reproducibility.
2Measurement precision
If reference measurements are performed with multiple calibration gases, then gas property differences are accounted for, but calibration complexity increases
Solution Approach 1:
The patent uses parameter changes by introducing gas-specific scaling factors that account for differences in gas properties such as molecular weight and viscosity. By measuring temperature and pressure and applying gas-specific scaling functions, the system accurately compensates for gas property variations without requiring complex hardware modifications, thereby improving measurement precision while managing calibration complexity through software-based solutions.
Data Source
AI summary
A method for calibrating a gas flow metrology system for a substrate processing system includes a) measuring temperature using a first temperature sensor and a reference temperature sensor over a predetermined temperature range and determining a first transfer function; b) measuring pressure using a first pressure sensor and a reference pressure sensor over a predetermined pressure range using a first calibration gas and determining a second transfer function; c) performing a first plurality of flow rate measurements in a predetermined flow rate range with a first metrology system and a reference metrology system, wherein the first metrology system and the reference metrology system use a first orifice size and the first calibration gas; and d) scaling temperature and pressure using the first transfer function and the second transfer function, respectively, and determining a corresponding transfer function for the first calibration gas based on the first plurality of flow rate measurements.