Transient Gas Flow Metrology via Pressure Rate of Rise
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Solution Overview
Problem
Current gas delivery and measurement systems, such as mass flow controllers, fail to accurately detect transient flow anomalies during semiconductor wafer fabrication processes, leading to potential process shifts and inaccuracies in gas flow control.
Innovation Solution
A method using a pressure rate of rise technique to calculate transient flow rates by measuring pressure and temperature data over time in a test chamber of known volume, identifying groups of data sample points, and determining lines of best fit to accurately determine transient flow rates and anomalies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard pressure rate of rise technique is used to calculate flow rate, then the measurement process is simple, but transient flow anomalies cannot be detected accurately
Solution Approach 1:
The patent divides the continuous pressure and temperature data into discrete groups of successive data sample points. Each group is processed independently to calculate ratio values and determine lines of best fit, enabling detection of transient flow anomalies at different time intervals while maintaining manageable computational complexity
Solution Approach 2:
The patent pre-calculates ratio values between pressure data and the product of temperature and gas compressibility for each data sample point before determining the final flow rate. This preliminary processing step prepares the data for more accurate transient flow detection by establishing baseline relationships between measured parameters
2Measurement precision
If groups of successive data sample points with overlap are used, then transient flow anomalies are detected more accurately, but calculation time increases
Solution Approach 1:
The patent uses overlapping groups of successive data sample points where each group shares one or more data points with adjacent groups. This provides redundant measurements that improve transient flow anomaly detection accuracy by capturing flow changes from multiple overlapping time windows, with the overlap ensuring no transient anomaly is missed between discrete measurement intervals
3Measurement precision
If line of best fit is determined for ratio values, then transient flow rate accuracy is improved, but computational complexity increases
Solution Approach 1:
The patent transforms the raw pressure and temperature measurements into ratio values that represent the relationship between pressure and the product of temperature and gas compressibility. By determining lines of best fit for these transformed parameters rather than raw measurements, the method accounts for gas behavior changes more accurately while maintaining a systematic approach to data processing
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 method provides more accurate representation of actual gas flow rates and detects transient flow anomalies not typically identified by standard techniques, ensuring precise control of gas flow during semiconductor processes.
Implementation Method 1
a method of calculating a transient flow rate of a flowed process gas uses a pressure rate of rise technique while the process gas is flowed through a mass flow controller to a chamber of a known volume
Implementation Method 2
Once gas flow has stabilized, the downstream valve may be closed, and as a result the gas pressure may begin to rise in the volume
Data Source
AI summary
A method of calculating a transient flow rate of a flowed process gas comprises flowing process gas through a mass flow controller into a chamber of known volume and measuring successive data sample points which include pressure data, temperature data, and a time value for each successive data sample point. Groups of successive data sample points are identified wherein each group shares one or more successive data sample points with another group, and ratio values are calculated for each of the successive data sample points wherein each ratio value is a ratio between the pressure data and a product of temperature and gas compressibility data for each respective time value. A line of best fit of the ratio values is determined within at least one group, and then the transient flow rate of the flowed process gas is calculated using a pressure rate of rise technique wherein the pressure rate of rise technique utilizes a ratio value determined from the line of best fit for at least one time value within the at least one group.