Oblique Low-Coherence Interferometer for Plasma Temperature Measurement
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Solution Overview
Problem
Conventional temperature measuring methods using low-coherence interferometers in plasma processing apparatuses often compromise plasma process uniformity by requiring a hole in the holding stage or upper electrode for light emission, which affects the precision and uniformity of the plasma process.
Innovation Solution
A plasma processing apparatus and method utilizing a low-coherence interferometer that emits measurement light obliquely through a light source window and receives reflected light through a light-receiving window, eliminating the need for a hole in the holding stage or upper electrode, allowing for precise temperature measurement without disrupting the plasma process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a hole is formed in the holding stage or upper electrode for light emission, then temperature measurement can be performed, but plasma process uniformity deteriorates
Solution Approach 1:
A light-transmitting window is introduced as an intermediary component in the chamber wall to allow light passage without compromising the structural integrity and plasma uniformity of the holding stage or upper electrode. The window serves as a mediator that enables optical access while maintaining plasma process quality.
Solution Approach 2:
The measurement system transitions from a vertical light emission approach (requiring holes in electrodes) to an oblique emission approach through side windows. This dimensional change in light path orientation eliminates the need for disruptive holes in the plasma-generating components.
2Measurement precision
If conventional temperature measuring methods are used, then temperature can be measured, but the structure becomes complex or measurement precision is insufficient
Solution Approach 1:
The patent replaces complex mechanical temperature measurement systems (such as contact thermometers or multi-component optical systems requiring holes in electrodes) with a simplified low-coherence interferometer system that measures temperature through refractive index changes, enabling non-contact, non-intrusive 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 high-precision and uniform plasma processing by accurately measuring substrate temperatures without compromising the plasma process uniformity, ensuring consistent film formation and etching results.
Implementation Method 1
interference between reflected lights of the n measurement lights and a reflected light of the reference light reflected by a reference light reflecting unit is measured to simultaneously measure temperatures of the plurality of measurement points
Implementation Method 2
a temperature measuring technology using a low-coherence interferometer which can directly measure a temperature of a substrate
Implementation Method 3
a measurement light is vertically emitted to a surface of an object to be measured through the hole to measure a temperature of the object
Data Source
AI summary
A plasma processing apparatus and a temperature measuring method that may measure a temperature of an object in a processing chamber by a low-coherence interferometer without forming a hole in a holding stage or an upper electrode of the plasma processing apparatus, thereby performing a plasma process of a substrate with high precision and uniformity. The plasma processing apparatus is implemented by disposing a light source collimator outside of a light source window, disposing a light-receiving collimator outside of a light-receiving window, allowing a measurement light emitted from the light source collimator to pass through the light source window to be obliquely emitted to a surface of the object to be measured, and allowing the reflected measurement light to pass through the light-receiving window to be incident on the light-receiving collimator. The temperature of the object in the processing chamber may be measured by the low-coherence interferometer.