Dielectric Property Measurement Using RF Capacitance Calibration
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Solution Overview
Problem
Current methods for measuring dielectric properties of parts in plasma processing systems are inaccurate due to the use of small sample coupons that may not represent the material composition of full-sized parts, and the measurements are often taken at different frequencies than those used in plasma processing, leading to extrapolation errors.
Innovation Solution
A method involving an apparatus with an electrically grounded chamber, a lower electrode connected to an RF transmission rod, and an upper electrode, which uses a capacitance meter to measure capacitance between the RF rod and the upper electrode at various separation distances, allowing for the determination of dielectric constant and loss tangent by simulating the resonance frequency and calculating the capacitance of the part.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If small sample coupons are used for measurement, then measurement time and complexity are reduced, but measurement precision deteriorates because the sample may not represent the material composition of the full-sized part
Solution Approach 1:
The measurement process is segmented into two distinct phases: (1) calibration phase using small sample coupons to establish the relationship between capacitance and dielectric properties, and (2) measurement phase using the calibrated apparatus with the full-sized part. This segmentation allows the benefits of quick small-sample calibration while achieving accurate full-part measurement results.
Solution Approach 2:
The small sample coupon serves as a representative copy or model of the full-sized part's material composition. By calibrating the measurement system with the coupon (copy) and then applying the same measurement parameters to the actual part, the system transfers the calibration data to achieve accurate measurements without requiring the coupon itself to be the full-sized part.
2Adaptability or versatility
If dielectric properties are measured at different frequencies than operating frequency, then measurement flexibility is improved, but measurement precision deteriorates due to frequency-dependent dielectric properties requiring extrapolation
Solution Approach 1:
The system performs preliminary calibration measurements at the actual operating frequency (e.g., 13.56 MHz) before conducting the actual dielectric property measurement. By pre-establishing the capacitance-dielectric property relationship at the correct frequency through calibration, the system eliminates the need for frequency extrapolation and ensures measurement accuracy at the operating frequency.
Solution Approach 2:
The measurement system dynamically adjusts the RF frequency parameter to match the actual operating frequency of the plasma processing equipment. By changing the frequency parameter from a fixed calibration frequency to the variable operating frequency, the system ensures that dielectric properties are measured at the correct frequency without requiring extrapolation.
3Measurement precision
If full-sized parts are measured directly, then measurement precision is improved, but device complexity and measurement time increase
Solution Approach 1:
The small sample coupon acts as an intermediary element in the measurement process. It is used to calibrate the measurement system and establish the capacitance-dielectric property relationship, serving as a mediator between the measurement apparatus and the full-sized part. This intermediary approach simplifies the overall process by separating calibration from measurement.
Solution Approach 2:
The measurement process is divided into calibration (using coupon) and measurement (using full part) segments. This segmentation reduces device complexity by allowing the use of a simpler calibration setup with the coupon, while the full measurement apparatus only needs to perform the actual measurement at operating frequency without requiring complex calibration mechanisms.
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 accurate measurement of dielectric properties of full-sized parts at the operating frequency of RF power, reducing extrapolation errors and providing precise data for plasma processing systems.
Implementation Method 1
using the capacitance meter to measure and record the capacitance between the RF rod and the upper electrode
Implementation Method 2
transmitting radiofrequency (RF) power through a processing gas
Implementation Method 3
a plasma is generated by transmitting radiofrequency (RF) power through a processing gas
Data Source
AI summary
A method is disclosed for calibrating a capacitance of an apparatus for measuring dielectric properties of a part. The apparatus includes an electrically grounded chamber, a lower electrode disposed within the chamber and connected to a radiofrequency (RF) transmission rod, an electrically grounded upper electrode disposed within the chamber above the lower electrode, and a variable capacitor connected to control transmission of RF power through the RF transmission rod to the lower electrode. A method is also disclosed for determining a capacitance of a part through use of the apparatus. A method is also disclosed for determining a dielectric constant of a part through use of the apparatus. A method is also disclosed for determining a loss tangent of a part through use of the apparatus.