Multi-spot scanning with gap-controlled arrays
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Solution Overview
Problem
Conventional multi-spot scanning techniques are limited by the division of the optical field of view among multiple spots, leading to inefficient use of expensive optics and inability to achieve high data rates required for next-generation inspection systems, with limitations in the number of spots, scanner speed, and stage speed.
Innovation Solution
A multi-spot scanning technique using a spot array with predetermined gaps between spots, allowing for scalability to a large number of spots and elimination of cross-talk, by determining optimal spot separation and using a full field of view in each scan line cycle, with the scanner moving in a first direction and the stage in a second direction to ensure complete coverage without overlapping or missing tracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the optical field of view is divided among multiple spots to increase scanning speed, then the data rate increases, but the effective field of view is reduced to approximately one-half of the available FOV
Solution Approach 1:
The patent transitions from conventional single-dimension spot scanning to multi-dimensional spot array scanning. Multiple spots are arranged in arrays (e.g., 2D grids) and scanned simultaneously across the wafer surface, enabling the system to utilize the full optical field of view while maintaining high data rates. This dimensional expansion allows independent control of spot positions and scanning trajectories, resolving the contradiction between data rate and effective FOV.
Solution Approach 2:
The patent segments the scanning process into multiple independent spot channels within an array configuration. Each spot in the array can be independently controlled and scanned, allowing the system to divide the total scanning task across multiple parallel channels while utilizing the complete optical field of view. This segmentation enables high data rates through parallel processing without sacrificing effective FOV.
2Productivity
If the number of spots is increased to achieve high data rates, then the scanning speed increases, but the cost of electronics and mechanical systems increases due to higher line frequency and stage speed requirements
Solution Approach 1:
The patent merges multiple spot scanning functions into a unified spot array system that operates within the full optical field of view. By combining multiple spots into coordinated arrays with predetermined gaps, the system achieves high data rates through parallel scanning while maintaining moderate line frequencies and stage speeds. This merging approach distributes the scanning load across multiple channels, reducing the performance requirements and cost of individual electronic and mechanical components.
Solution Approach 2:
The patent changes key operating parameters by implementing predetermined gap distances between spots in the array and optimizing spot separation. These parameter adjustments enable the system to achieve high data rates without requiring excessively high line frequencies or stage speeds, thereby reducing electronics and mechanical system costs while maintaining productivity.
3Area of stationary object
If spots are placed close together to maximize field of view utilization, then the effective field of view increases, but cross-talk between spots occurs
Solution Approach 1:
The patent applies local quality control by implementing predetermined gap distances between adjacent spots in the array. These locally optimized gap distances are specifically designed to prevent cross-talk between neighboring spots while maximizing field of view utilization. The gap distance is determined based on spot size, optical properties, and scanning parameters, ensuring that each spot maintains its signal integrity without interfering with adjacent spots.
4Productivity
If conventional multi-spot scanning is used to increase data rate, then scanning speed improves, but the number of spots is limited to less than 10 due to physical limitations
Solution Approach 1:
The patent extends the spot configuration from conventional single-row arrays to multi-dimensional spot arrays (e.g., 2D grids with rows and columns). This dimensional expansion allows the system to incorporate significantly more spots (远超10个) while maintaining manageable line frequencies and stage speeds. The multi-dimensional arrangement distributes spots across the full optical field of view, enabling high data rates through parallel scanning of numerous spots without hitting the physical limitations of conventional single-dimension approaches.
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 approach enables high-speed and high-efficiency scanning with optimized throughput, leveraging the full optical field of view and minimizing cross-talk, thus meeting the high data rate requirements of next-generation inspection systems in a cost-effective manner.
Implementation Method 1
a spot array generator to provide a spot array comprising a number of spots
Implementation Method 2
an objective lens to focus the scanning spot array on the wafer
Implementation Method 3
a scanner to scan the spot array in a first direction parallel to the wafer moving direction
Data Source
AI summary
A multi-spot scanning technique using a spot array having a predetermined gap between spots can advantageously provide scalability to a large number of spots as well as the elimination of cross-talk between channels. The multi-spot scanning technique can select a number of spots for the spot array (1D or 2D), determine a separation between the spots to minimize crosstalk, and perform a scan on a wafer using the spot array and a full field of view (FOV). Performing the scan includes performing a plurality of scan line cycles, wherein each scan line cycle can fill in gaps left by previous scan line cycles. This “delay and fill” scan allows large spacing between spots, thereby eliminating cross-talk at the detector plane. In one embodiment, the scan is begun and ended outside a desired scan area on the wafer to ensure full scan coverage.