RF Reference Measuring Circuit With LC Matching for Plasma Drive Calibration
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Solution Overview
Problem
Existing substrate processing systems face inefficiencies due to impedance mismatches between RF direct drive circuits and existing RF power meters and dummy loads, making it difficult to measure and calibrate RF power or bias output accurately.
Innovation Solution
Incorporating an RF reference measuring circuit with an LC circuit that matches the impedance of direct drive circuits to that of RF power meters and dummy loads, using a make-break connector to facilitate connections between the direct drive circuit and processing chamber loads, allowing for accurate measurements with existing equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the direct drive circuit is connected directly to existing coaxial cables and RF power meters, then the connection is simple, but impedance mismatch causes power reflection and measurement inaccuracy
Solution Approach 1:
An LC matching circuit is introduced as an intermediary component between the direct drive circuit and the existing coaxial cables/RF power meters. This matching circuit transforms the low impedance output of the direct drive circuit to match the 50-ohm impedance of standard coaxial cables and RF power meters, enabling accurate measurements without requiring modification of the existing equipment.
2Loss of energy
If impedance matching is implemented using traditional methods, then power reflection is reduced, but the cost of new equipment increases
Solution Approach 1:
The LC matching circuit serves as a cost-effective intermediary solution that achieves impedance matching without requiring replacement of expensive existing equipment. The circuit uses standard inductors and capacitors to transform impedances, allowing the system to maintain low power reflection losses while utilizing existing coaxial cables and RF power meters.
Solution Approach 2:
The matching circuit changes the electrical parameters (impedance) of the signal path by using LC components to transform the low impedance output of the direct drive circuit to the 50-ohm impedance level required by standard RF measurement equipment, thereby reducing power reflection without changing the physical equipment.
3Productivity
If the direct drive circuit operates at low impedance, then it is efficient for plasma generation, but it cannot be measured with standard high impedance equipment
Solution Approach 1:
The LC matching circuit acts as a mediator that preserves the low-impedance operation of the direct drive circuit for efficient plasma generation while simultaneously providing impedance transformation to enable measurement with standard high-impedance RF equipment. The matching circuit is configured to present low impedance to the plasma load while transforming to 50-ohm output for measurement.
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
Enables efficient and accurate measurement of RF power and bias signals generated by direct drive systems, reducing costs and improving operational consistency by matching impedances and allowing for periodic calibration.
Implementation Method 1
The LC circuit is configured to match the impedance of the drive circuit to the RF power meter and the dummy load
Implementation Method 2
The make-break connector is configured to connect the drive circuit to one of the RF reference measuring circuit and a processing chamber load
Data Source
AI summary
A substrate processing system includes a drive circuit, an RF reference measuring circuit, and a make-break connector. The drive circuit generates an RF drive signal at a first RF frequency. The RF reference measuring circuit includes an LC circuit having an input impedance and an output impedance. An output of the LC circuit connects to an RF power meter and a dummy load. The make-break connector connects the drive circuit to one of the RF reference measuring circuit and a processing chamber load including a component of the substrate processing system. An output impedance of the drive circuit matches an impedance of an input impedance of the LC circuit. The output impedance of the drive circuit does not match impedances of the RF power meter and the dummy load. The LC circuit matches the impedance of the drive circuit to the RF power meter and the dummy load.