Encoder Head Multi-Angle Beam Positioning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current measurement systems in semiconductor processing face challenges in achieving precise positioning of reticles and wafers due to limitations in accuracy and reliability, particularly in monitoring the relative movement between objects along multiple axes.
Innovation Solution
A measurement system utilizing a grating coupled with an encoder head that directs measurement beams at different angles and wavelengths, employing imperfect corner cubes for redirecting diffracted beams to minimize stray light and enhance contrast, allowing for precise determination of object position along multiple axes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single measurement beam is used to monitor position, then the device complexity is low, but the measurement precision is insufficient for high accuracy positioning requirements
Solution Approach 1:
The measurement system is segmented into multiple independent measurement beams, each operating at different wavelengths and angles. This allows each beam to contribute independently to the overall measurement precision without requiring complete system redesign, thereby improving positioning accuracy while managing complexity through modular architecture
Solution Approach 2:
The patent introduces multiple dimensions of measurement by using beams at different wavelengths (spectral dimension) and different incident angles (spatial dimension). This multi-dimensional approach enhances measurement precision by capturing position information from multiple independent perspectives simultaneously
2Measurement precision
If multiple measurement beams at different wavelengths are used, then the measurement precision improves, but the loss of substance increases due to multiple light sources and components
Solution Approach 1:
The grating structure serves multiple functions simultaneously: it diffracts multiple wavelengths, redirects multiple beams, and provides the measurement reference for all beams. This multi-functionality reduces the need for separate components for each wavelength, thereby minimizing material loss while maintaining high measurement precision
3Ease of operation
If traditional corner cubes are used for beam redirection, then the ease of operation is good, but object-generated harmful factors increase due to stray light and reduced contrast
Solution Approach 1:
Instead of using traditional corner cubes that reflect light in all directions, the patent employs gratings with locally optimized diffraction properties that redirect light precisely into the desired measurement path. This local optimization of light redirection quality minimizes stray light generation while maintaining ease of beam alignment
Solution Approach 2:
The patent converts the potentially harmful stray light from traditional corner cubes into beneficial diffracted orders. By using gratings, the redirected beams systematically channel light into specific +1 and -1 orders that carry measurement information, transforming what would be waste light into useful measurement signals
4Measurement precision
If measurement beams are directed at different angles, then the measurement precision improves through multi-axis monitoring, but the device complexity increases due to additional redirectors and alignment requirements
Solution Approach 1:
The grating serves as a universal element that handles multiple beam angles and directions simultaneously. A single grating structure redirects multiple measurement beams at different angles into their respective measurement paths, eliminating the need for separate redirectors for each beam and reducing overall device complexity while maintaining multi-axis measurement precision
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 solution improves the accuracy and reliability of position measurement, enabling precise positioning of reticles and wafers, which is critical for high-quality semiconductor manufacturing by minimizing errors and maintaining high contrast even under tilts and shear conditions.
Implementation Method 1
the first measurement beam impinging on the grating creates a +1 order beam directed back at the encoder head, and the second measurement beam impinging on the grating creates a −1 order beam directed back at the encoder head
Implementation Method 2
the encoder head includes (i) a first redirector that redirects the +1 order beam of the first measurement beam back at the grating, and (ii) a second redirector that redirects the −1 order beam of the second measurement beam back at the grating. For example, in one such embodiment, each redirector can be an imperfect corner cube
Data Source
AI summary
A measurement system (22) for measuring the position of a work piece (28) along a first axis includes a grating (234), and an encoder head (238) that directs a first measurement beam (240) at the grating (234) at a first angle, and directs a second measurement beam (242) at the grating (234) at a second angle. An absolute value of the first angle relative to a normal (244) of the grating (234) is different from an absolute value of the second angle relative to the normal (244) of the grating (234). Additionally, the first measurement beam (240) has a first wavelength, and the second measurement beam (242) has a second wavelength that can be different from the first wavelength. Further, the first measurement beam (240) and the second measurement beam (242) can impinge at approximately the same location on the grating (234).