Planar RF Voltage-Current Probe for High-Temperature Plasma
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Solution Overview
Problem
Conventional voltage-current (V/I) probes are not compatible with high-temperature RF plasma processing environments, leading to inaccurate measurements of RF power due to thermal degradation and location-dependent peak voltage and current variations, resulting in inefficiencies and chamber-to-chamber process variations.
Innovation Solution
A voltage-current sensor assembly with a planar body made of non-organic, electrically insulative material, featuring a measurement opening with voltage and current pickups that can be mounted proximate to the plasma processing chamber, allowing for accurate measurement of RF power and phase in high-temperature environments, and a method for calibrating the sensor using a dummy load to determine actual RF power coupled to the chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional V/I probes are used in high-temperature RF plasma processing environments, then the probes can measure RF power, but the probes suffer thermal degradation and provide inaccurate measurements
Solution Approach 1:
The patent changes the material parameter of the probe substrate from organic (FR-4) to inorganic (alumina ceramic), which fundamentally alters the thermal stability parameter. This material substitution enables the probe to withstand high temperatures (600°C-700°C process temperatures and 100°C-200°C chamber temperatures) without thermal degradation, thereby resolving the contradiction between measurement accuracy and thermal reliability
Solution Approach 2:
The patent employs a composite structure combining inorganic alumina ceramic substrate with metallic components (bracket, mounting features). This composite construction provides both thermal stability from the ceramic and structural support from the metal, enabling the probe to maintain measurement accuracy in high-temperature environments while ensuring mechanical reliability
2Reliability
If V/I probes are located far from the plasma processing chamber to avoid heat, then the probes survive thermal conditions, but the accuracy of voltage and current measurements is greatly reduced
Solution Approach 1:
By changing the thermal resistance parameter through material substitution (organic to inorganic), the probe can now operate at higher temperatures, enabling placement closer to the plasma chamber. This parameter change removes the thermal constraint that previously forced remote probe positioning, thereby allowing accurate near-chamber measurements while maintaining probe survival
3Ease of manufacture
If conventional V/I probes with organic material substrates are used, then the probes are easier to manufacture, but they thermally degrade at temperatures greater than about 70° C.
Solution Approach 1:
The patent changes the temperature resistance parameter by substituting the substrate material from organic FR-4 to inorganic alumina ceramic. This material parameter change increases the maximum operating temperature from 70°C to above 600°C, resolving the contradiction between ease of manufacture and temperature tolerance. The ceramic substrate, while requiring different manufacturing processes, provides the necessary thermal stability for RF plasma processing environments
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 precise measurement and control of RF power in high-temperature environments, reducing chamber-to-chamber variations and improving the accuracy of RF power delivery to the processing region, thereby enhancing the efficiency and consistency of plasma processing.
Implementation Method 1
a voltage pickup disposed around the measurement opening, wherein the voltage pickup is electrically coupled to a first voltage measurement circuit
Implementation Method 2
a current pickup disposed around the measurement opening, wherein the current pickup is electrically coupled to a first current measurement circuit
Data Source
AI summary
A voltage-current sensor enables more accurate measurement of the voltage, current, and phase of RF power that is delivered to high-temperature processing region. The sensor includes a planar body comprised of a non-organic, electrically insulative material, a measurement opening formed in the planar body, a voltage pickup disposed around the measurement opening, and a current pickup disposed around the measurement opening. Because of the planar configuration and material composition of the sensor, the sensor can be disposed proximate to or in contact with a high-temperature surface of a plasma processing chamber.