Piezo-Shifted Detector Array for High Resolution Plasma Thickness Measurement
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Solution Overview
Problem
Current measuring technologies, such as those using CCD or photodiode arrays, are limited in wavelength resolution power, restricting the thickness of examination targets that can be measured, particularly in plasma processing applications, where thick members like focus rings cannot be accurately assessed.
Innovation Solution
A measuring apparatus with a wavelength dispersion device and a detector array, combined with a piezoelectric device, increases wavelength resolution power by shifting the photodetection elements, allowing for the measurement of thicker targets by effectively doubling the sampling number through frequency domain analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a spectroscope using a CCD array or photodiode array is used for measurement, then spectrum data can be acquired instantly, but the wavelength resolution power is limited by the number of elements and cannot be increased beyond physical limitations
Solution Approach 1:
The patent applies the dynamics principle by making the detector movable through piezoelectric actuation. The detector is shifted by d/m where d is the width of each photodetection element and m is an integer equal to or greater than 2. This dynamic positioning allows the same physical detector array to sample multiple wavelength positions, effectively increasing the wavelength resolution power beyond the fixed limitation imposed by the number of elements.
2Manufacturing precision
If the wavelength resolution power is limited, then the device structure remains simple, but the thickness range of measurable examination targets is restricted to very thin objects
Solution Approach 1:
By dynamically shifting the detector position using piezoelectric devices, the system increases the effective sampling number in the wavelength domain. This enables measurement of thicker examination targets such as focus rings in plasma processing apparatus, which were previously impossible to measure with fixed detector arrays.
3Measurement precision
If more photodetection elements are added to increase wavelength resolution power, then thicker targets can be measured, but the device complexity and cost increase
Solution Approach 1:
Instead of adding more photodetection elements, the patent dynamically repositions the existing detector array using piezoelectric devices. The detector is shifted by d/m where d is the element width and m≥2, allowing the same physical elements to effectively sample more wavelength points, thereby increasing wavelength resolution power without increasing device complexity.
Solution Approach 2:
The patent changes the positional parameter of the detector array through piezoelectric actuation. By shifting the detector position, the system effectively changes the sampling points in the wavelength domain, achieving higher wavelength resolution power from the same physical detector configuration.
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 the accurate measurement of thicker examination targets, such as focus rings, in plasma processing environments, enhancing the thickness range and reducing manufacturing costs by eliminating the need for movable mirrors and improving temperature control accuracy.
Implementation Method 1
a wavelength dispersion device which disperses light reflected by one surface of an examination target having a thickness and light reflected by a rear surface of the examination target, as incident light
Implementation Method 2
a piezoelectric device which is attached to the detector to convert an applied voltage into a mechanical power
Implementation Method 3
a detector in which a plurality of photodetection elements receiving light dispersed by the wavelength dispersion device and detecting a power of the received light
Data Source
AI summary
Provided a measuring apparatus includes a wavelength dispersion device which dispersed light reflected by one surface of an examination target having a thickness D and light reflected by a rear surface of the examination target, as incident light, a detector in which a plurality of photodetection elements receiving light dispersed by the wavelength dispersion device and detecting a power of the received light in are provided in an array shape, and a piezoelectric device which is attached to the detector to convert an applied voltage into a mechanical power, wherein the detector detects the power of the received light when the detector is shifted by the mechanical power converted by the piezoelectric device as much as d/m, where d is a width of each of the photodetection elements in an array direction and m is an integer equal to or greater than 2.