Acousto-Optic Traveling Lens Wafer Inspection Throughput
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Solution Overview
Problem
Conventional semiconductor wafer inspection systems face limitations in throughput due to the speed and quality of single laser beam scanning, leading to suboptimal data rates and potential scan aberrations, which hinder the ability to achieve high-resolution, high-speed imaging required for submicron semiconductor manufacturing.
Innovation Solution
A system utilizing a first traveling lens acousto-optic device and a collection module with a second traveling lens acousto-optic device, along with illumination and detection optics, to generate and manipulate beams that scan the object while maintaining a fixed focal point, thereby increasing throughput and reducing cross-talk and thermal damage risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single laser beam is used for scanning the object, then the system can achieve high resolution imaging, but the throughput and data rate are limited
Solution Approach 1:
The patent divides the single laser beam into multiple parallel beams using a beam splitter and scanning mirrors. This allows simultaneous illumination of multiple points on the object, enabling parallel data acquisition while maintaining the resolution quality of individual beams. The segmented beam approach increases throughput by processing multiple spatial locations concurrently.
Solution Approach 2:
The patent introduces a temporal dimension to the scanning process by rapidly switching between multiple beams in a time-multiplexed manner. The system scans multiple beams across the object surface in sequence, with each beam capturing data from a different location. This dimensional approach to beam control enables high-speed parallel imaging while maintaining the optical quality of individual beams.
2Illumination intensity
If high brightness laser sources are used to improve illumination intensity, then imaging quality improves, but thermal damage to the object may occur
Solution Approach 1:
The total laser power is divided into multiple parallel beams, so each individual beam carries only a fraction of the total power. This segmentation of energy distribution maintains adequate illumination intensity for high-quality imaging while reducing the power density at any single point on the object, thereby minimizing thermal damage risk.
Solution Approach 2:
The system uses continuous wave laser sources that are modulated into multiple parallel beams rather than using pulsed high-power illumination. This continuous action distributed across multiple beams provides steady illumination intensity needed for high-quality imaging while avoiding the peak power concentrations that cause thermal damage.
3Productivity
If multiple beams are used to scan the object, then throughput increases, but cross-talk between beams may occur
Solution Approach 1:
The patent uses spatial light modulators and precise scanning mirror systems as intermediaries to control and separate the multiple beams. These intermediary components ensure that each beam remains spatially distinct and properly directed at its target location on the object, preventing cross-talk between adjacent beams while maintaining the throughput benefits of parallel scanning.
4Speed
If a rotating mirror system is used for scanning, then the scanning speed can be increased, but scan aberrations and limited illumination brightness occur
Solution Approach 1:
Instead of using a single rotating mirror to scan one beam, the patent segments the illumination into multiple parallel beams and uses separate scanning control for each beam. This segmentation allows each beam to be scanned independently with optimized trajectories, reducing scan aberrations while maintaining high scanning speeds through parallel processing.
Solution Approach 2:
The patent replaces traditional mechanical rotating mirror systems with acousto-optic modulators and electronically controlled scanning mirrors. This substitution eliminates the mechanical inertia and vibration issues of rotating mirrors, enabling faster and more accurate beam positioning without scan aberrations, while maintaining high scanning speeds through electronic control.
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 configuration enhances the throughput of semiconductor wafer inspection systems while maintaining or improving the accuracy and reliability of data collection, enabling higher data rates necessary for submicron structure inspection.
Implementation Method 1
a first traveling lens acousto-optic device that may be configured to generate a first traveling lens that propagates through an active region of the first traveling lens acousto-optic device
Implementation Method 2
illumination optics that may be configured to receive the input beam and to output, in response to the input beam, an output beam that scans the object at a second direction
Implementation Method 3
optically manipulate the collected beam to provide a counter-scan beam is directed towards the detection unit and has a focal point that is positioned at a same location regardless of the propagation of the collected beam along the third direction
Data Source
AI summary
A system, including an illumination module that comprises (a) a first traveling lens acousto-optic device; (b) a light source for illuminating the first traveling lens to provide an input beam that propagates along a first direction; (c) illumination optics for outputting an output beam that scans the object at a second direction; a detection unit; and a collection module for collecting a collected beam from the object, wherein the collected beam propagates along a third direction; and optically manipulating the collected beam to provide a counter-scan beam is directed towards the detection unit and has a focal point that is positioned at a same location regardless of the propagation of the collected beam along the third direction.