Anamorphic Prism Illumination Module for Semiconductor Wafer Inspection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing inspection systems for semiconductor wafers face challenges in achieving high throughput while maintaining sensitivity, particularly in double dark field tools, where the shape and size of the illumination aperture affect the efficiency of particle detection.
Innovation Solution
An adjustable asymmetrical magnification illumination module using a pair of anamorphic prisms, a parallel plate, and rotating elements allows for the conversion of a circular radiation beam into an elliptical beam, enabling larger off-axis illumination angles and improved sensitivity by controlling the width-to-length ratio of the radiation beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a circular illumination aperture is used, then the system maintains simple structure and alignment, but the throughput and sensitivity are limited due to fixed illumination angles
Solution Approach 1:
The illumination system is segmented into multiple independent anamorphic prism pairs, each capable of being selectively positioned in the optical path. This allows the system to switch between different illumination configurations (circular, elliptical, linear) without requiring a completely different optical design for each mode, thereby improving throughput while managing complexity through modular architecture.
Solution Approach 2:
The illumination module incorporates dynamic elements including rotating stages and movable prism pairs that can adjust the illumination aperture shape and orientation in real-time. This dynamic adaptability allows the system to optimize illumination angles and spot shapes for different inspection scenarios, enhancing both throughput and sensitivity without permanent structural complexity.
2Productivity
If the illumination aperture is enlarged to increase throughput, then more light reaches the sample, but the illumination angles become too shallow reducing sensitivity for off-axis particle detection
Solution Approach 1:
Anamorphic prism pairs are used to create asymmetric (elliptical or linear) illumination apertures from the circular input beam. This asymmetric transformation allows the illumination to cover larger angular ranges in specific directions while maintaining appropriate spot sizes, thereby increasing throughput without sacrificing the off-axis illumination angles needed for sensitive particle detection.
Solution Approach 2:
The system changes the illumination parameters (aperture shape, orientation, and size) dynamically by rotating the anamorphic prism pairs and adjusting their positions. This allows optimization of the illumination cone angles to simultaneously achieve high throughput through larger aperture utilization and high sensitivity through appropriate off-axis angle coverage.
3Measurement precision
If the illumination spot size is reduced to improve resolution, then smaller particles can be detected, but the collection area decreases reducing throughput
Solution Approach 1:
The system uses anamorphic prism pairs to transform the circular illumination spot into elliptical or linear spots, effectively utilizing the angular dimension more efficiently. This dimensional transformation allows the illumination to cover larger angular ranges (improving throughput) while maintaining appropriate spot sizes for resolution (improving detection capability), resolving the trade-off between spot size and collection area.
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 enhances throughput and sensitivity in inspection systems by allowing for adjustable illumination configurations without replacing existing telescopes, enabling modular operation and improved particle detection capabilities.
Implementation Method 1
pair of anamorphic prisms configured to asymmetrically magnify a first radiation beam to provide a second radiation beam
Implementation Method 2
rotating elements for rotating the anamorphic prisms in order to adjust the asymmetrical magnification of the radiation beam
Data Source
AI summary
An illumination module that includes a pair of anamorphic prisms that comprises a first anamorphic prism and a second anamorphic prism; wherein the pair of anamorphic prisms is configured to (a) receive a first radiation beam that propagates along a first optical axis, and (b) asymmetrically magnify the first radiation beam to provide a second radiation beam that propagates along a second optical axis that is parallel to the first optical axis; and a rectangular prism that is configured to receive the second radiation beam and perform a lateral shift of the second radiation beam to provide a third radiation beam; and a rotating mechanism that is configured to change an asymmetrical magnification of the pair of anamorphic prisms by rotating at least one of the first anamorphic prism and the second anamorphic prism.