Optical Grating Pitch and Orientation Measurement With Aperture Filtering
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Solution Overview
Problem
Conventional measurement systems experience a decrease in accuracy and repeatability when measuring optical device structures on transparent substrates due to multi-reflection beams interfering with the measurement device, which affects the precision of pitch and orientation measurements.
Innovation Solution
A measurement system incorporating an aperture filtering component to reduce interference from multi-reflection beams by positioning an aperture in front of a mirror to filter out unwanted reflections, allowing only the primary light beam to reach the detector, thereby improving spatial resolution and accuracy of pitch and orientation measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional measurement systems are used to measure optical device structures on transparent substrates, then the measurement process can be performed, but multi-reflection beams interfere with the measurement device causing decreased accuracy and repeatability
Solution Approach 1:
The patent extracts and removes the harmful multi-reflection beams from the measurement system by introducing an aperture that blocks these interfering beams while allowing the primary measurement beam to pass through. This selectively removes the harmful component without affecting the useful measurement function.
Solution Approach 2:
The aperture acts as an intermediary element between the light source and the detector, mediating the interaction by filtering out harmful multi-reflection beams while permitting the primary beam to reach the detector. This intermediary component resolves the contradiction by selectively transmitting useful light and blocking harmful reflections.
2Measurement precision
If an aperture filtering component is added to block multi-reflection beams, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The aperture is a simple, inexpensive optical component that can be easily manufactured and integrated into the measurement system. Rather than using complex active filtering systems, the patent employs a passive, straightforward aperture structure that provides effective beam filtering without adding significant complexity or cost to the system.
3Measurement precision
If the aperture is positioned to filter multi-reflection beams, then spatial resolution improves, but the system requires precise positioning and alignment
Solution Approach 1:
The patent employs preliminary alignment procedures and positioning mechanisms that establish the correct aperture placement before measurements begin. By pre-positioning the aperture in the correct location relative to the optical path and using alignment features, the system reduces the difficulty of detecting and measuring during actual operation.
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
The aperture filtering component enhances the precision and reliability of measuring optical device structures by minimizing interference from multi-reflection beams, resulting in a high-resolution map of pitch and orientation angles with improved accuracy and reliability.
Implementation Method 1
an aperture filtering component to reduce interference from multi-reflection beams by positioning an aperture in front of a mirror to filter out unwanted reflections
Implementation Method 2
The light beam diffracts off a top surface of the first optical device structure
Implementation Method 3
a first lens disposed between the substrate and the light source and configured to focus the light beam to the substrate
Implementation Method 4
configured to direct the light beam to a mirror, an aperture disposed in front of the mirror
Data Source
AI summary
Embodiments described herein provide for a measurement system having an aperture filtering component and methods of utilizing the measurement system. The measurement system described herein includes a measurement arm and a stage. The measurement arm projects a light beam to a top surface of an optical device structure. Multi-reflection beams resulting from reflections and diffraction off other surfaces of a non-opaque substrate leads to interference. The measurement arm includes an aperture (e.g., an aperture filtering component) that filters the multi-reflection beams from being relayed to the detector. As such, only images of the light beam are relayed to the detector.