Multi-Head Optical Measuring Apparatus for Semiconductor Wafer Height
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Solution Overview
Problem
Existing measuring apparatuses are inefficient in measuring the height of semiconductor wafers at multiple points without reducing the measurement wavelength band per head, as they struggle to accurately correlate reflected light signals from multiple heads due to simultaneous detection by a single light detector.
Innovation Solution
A measuring apparatus with a holding unit and a measuring unit that includes multiple heads, optical fibers, and a controller to shift light application timings and detect returning light individually from each head, using a two-dimensional sensor to separate and detect light signals from multiple heads without reducing the measurement wavelength band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple heads are used to measure multiple points simultaneously, then productivity is improved, but the ability to correlate reflected light signals accurately deteriorates
Solution Approach 1:
The patent applies periodic action by sequentially activating different heads at different time points rather than simultaneously. The control unit controls the light source and shutter to emit light from the first head at a first time point and from the second head at a second time point, enabling the light detector to distinguish between signals from different heads through temporal separation while maintaining measurement efficiency
Solution Approach 2:
The patent introduces a shutter as an intermediary component between the light source and the measurand. The shutter selectively transmits or blocks light from different heads at different time points, acting as a mediator that enables temporal separation of light paths and allows the single light detector to accurately correlate signals with their respective sources
2Productivity
If filters are provided for each head to measure different wavelength bands, then productivity is improved, but the measurement wavelength band per head is reduced
Solution Approach 1:
Instead of using filters that would divide the wavelength band, the patent uses periodic temporal separation to allow a single head to measure across the entire wavelength band sequentially. The light source emits light in a predetermined wavelength band, and by controlling the timing of light emission from different heads, the system achieves multi-point measurement without restricting the wavelength range
Solution Approach 2:
The patent changes the temporal parameter (time of light emission) rather than the spectral parameter (wavelength band). By varying the time at which each head receives and emits light, the system distinguishes between multiple measurement points while maintaining the full wavelength band availability for each head, avoiding the need for wavelength-selective filters
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 efficient measurement of the height of semiconductor wafers at multiple points without reducing the measurement wavelength band per head, allowing for precise determination of the height and thickness of the wafer surface.
Implementation Method 1
The light in the predetermined wavelength band is diffracted by the lens due to the axial chromatic aberration into light rays that are converged at different positions on an optical axis depending on the wavelengths of the light rays
Implementation Method 2
the light ray focused on the upper surface of the measurand and having a predetermined wavelength is reflected by the measurand and mainly introduced through the lens into an optical fiber
Data Source
AI summary
A measuring apparatus includes a holding unit and a measuring unit. The measuring unit includes a first optical fiber for transmitting light emitted from a light source, a branching member for branching the light transmitted through the first optical fiber to at least two measuring optical fibers, a plurality of heads including respective beam condensers for converging the light branched by the branching member onto a measurand, a shutter device for shifting timings of application of the light applied from the heads to the measurand, a second optical fiber branched from the branching member and transmitting returning light reflected from the measurand, a spectroscopic unit having a light detector for detecting the returning light, and a controller for controlling the shutter device to control the timings of application of the light applied from the heads to the measurand and controlling the light detector to detect the returning light individually.