Multi-Wavelength Alignment Sensor for Semiconductor Workpiece Positioning
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Solution Overview
Problem
Conventional semiconductor workpiece alignment systems fail to accurately determine the position of workpieces with varying light transmission properties, such as silicon carbide wafers, leading to errors and inconsistencies due to their partial transparency to conventional light sources.
Innovation Solution
A workpiece alignment system utilizing a multi-wavelength, adjustable sensitivity light alignment sensor configured at a shallow angle relative to the workpiece, which emits a beam of light across a wide path and receives it at a different angle, allowing for accurate positioning by controlling sensitivity based on transmissivity and edge detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional light presence sensor is used to determine workpiece position, then the system is simple and easy to operate, but the measurement precision deteriorates for workpieces with varying light transmission properties
Solution Approach 1:
The system changes the wavelength parameter of the light source to match the optical properties of different workpiece materials. By selecting specific wavelengths where the workpiece has known absorption characteristics, the system achieves accurate position determination for various materials including silicon carbide, overcoming the limitation of conventional sensors that use fixed wavelength light sources
Solution Approach 2:
The alignment sensor is designed to handle multiple workpiece materials and transmission properties using a single multi-functional device. The sensor can detect both opaque and transparent workpieces by adjusting its operating wavelength, eliminating the need for separate sensing systems for different material types
2Measurement precision
If the light beam path is increased to improve detection accuracy for transparent workpieces, then the measurement precision improves, but the device complexity and alignment difficulty increase
Solution Approach 1:
The system transitions from measuring only light intensity to measuring the spatial distribution of light across multiple detector elements arranged in an array. This dimensional change allows the system to detect workpiece edges and positions by analyzing the pattern of light blockage across the array, improving accuracy without requiring complex alignment
3Adaptability or versatility
If a single wavelength light source is used to simplify the system, then the device complexity is reduced, but the adaptability to different workpiece materials deteriorates
Solution Approach 1:
The system uses multiple light sources emitting at different wavelengths in a periodic or sequential manner. By cycling through different wavelengths and analyzing the response at each wavelength, the system can characterize and adapt to the optical properties of various workpiece materials, achieving high versatility without requiring all wavelengths to be present simultaneously
Solution Approach 2:
The light emission system effectively creates a composite light source that combines multiple wavelengths. This composite approach allows the system to exploit the different optical absorption characteristics of various workpiece materials at different wavelengths, achieving broad material compatibility
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 system provides stable and repeatable signal read-backs, accurately determining the position of workpieces with varying transparency, reducing errors and improving handling precision across different substrate materials and thicknesses.
Implementation Method 1
a light emitter is configured to direct a beam of light at a plurality of wavelengths... a light receiver apparatus is positioned along the first path, wherein the light received apparatus is configured to receive the beam of light
Data Source
AI summary
A workpiece alignment system is provided has a light emission apparatus that directs a light beam at a plurality of wavelengths along a path at a shallow angle toward a first side of a workpiece plane at a peripheral region. A light receiver apparatus, receives the light beam on a second side opposite the first side. A rotation device selectively rotates a workpiece support. According controller determines a position of the workpiece based on an amount of the light beam received through the workpiece when the workpiece intersects the path. A sensitivity of the light receiver apparatus is controlled based on a transmissivity of the workpiece. A position of the workpiece is determined when the workpiece is rotated based on the rotational position, an amount of the light beam received, the transmissivity of the workpiece, detection of a workpiece edge, and the controlled sensitivity of the light receiver apparatus.