RF Pedestal Temperature Measurement via Discontinuous Signal Intervals
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Solution Overview
Problem
In RF processing apparatus for semiconductors, thermal sensors embedded in the wafer heater pedestal face interference from RF signals, leading to inaccurate temperature measurement and inefficient thermal control due to their operation with small current signals compared to the intensity of the applied RF signals.
Innovation Solution
A method involving the generation of a sequence of discontinuous RF signals with time intervals, where the thermal sensor generates sensing signals during these intervals, allowing precise temperature measurement by determining the time intervals based on heat resistance or capacitance values between the heater surface and the heating coil, ensuring minimal interference from RF signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermal sensor operates continuously with small current signal during RF signal activation, then temperature monitoring is maintained, but measurement precision deteriorates due to RF signal interference and noise
Solution Approach 1:
The patent applies periodic action by switching the RF signal on and off in discrete time intervals. During the off-periods, the thermal sensor can accurately measure temperature without RF interference. The controller uses these periodic measurement windows to monitor temperature while minimizing harmful RF interference, resolving the contradiction between continuous monitoring and measurement precision.
2Productivity
If RF signal intensity is increased for effective plasma processing, then processing efficiency is improved, but temperature measurement accuracy deteriorates due to increased interference with thermal sensor signals
Solution Approach 1:
The system uses periodic action by creating distinct on-periods for high-intensity RF plasma processing and off-periods for accurate temperature measurement. This allows the RF signal to operate at high intensity for effective processing when needed, while periodically switching off to enable accurate thermal sensor readings without interference, thus resolving the contradiction between processing efficiency and measurement accuracy.
Solution Approach 2:
The controller acts as an intermediary by coordinating the RF signal and thermal sensor operations. It manages the timing and switching between RF signal activation and temperature measurement, ensuring that high-power RF processing and sensitive thermal sensing do not occur simultaneously, thereby eliminating interference while maintaining both processing efficiency and measurement accuracy.
3Use of energy by moving object
If thermal sensor uses small current signal for operation, then energy consumption is reduced, but reliability deteriorates due to susceptibility to RF signal interference
Solution Approach 1:
The patent applies periodic action by scheduling thermal sensor measurements during RF off-periods. This allows the sensor to operate with minimal current for energy efficiency while ensuring measurements are taken only during interference-free windows, thereby maintaining both low energy consumption and high measurement reliability.
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 approach enables precise temperature measurement and control in RF processing apparatus, preventing mutual interference between plasma processes and temperature measurement, thereby enhancing thermal control efficiency.
Implementation Method 1
the heater has at least one thermal sensor embedded therein used for sensing the local temperature within a pedestal zone
Implementation Method 2
the heater has at least one thermal sensor embedded therein used for sensing the local temperature within a pedestal zone
Data Source
AI summary
A method for temperature measurement used in an RF processing apparatus for semiconductor includes generating by electrodes an RF signal sequence having multiple discontinuous RF signals that are separated by a time interval; and generating a temperature sensing signal by a thermal sensor during the time interval.