Multibeam Surface Sensing for Ahead-of-Path Focus Control
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Solution Overview
Problem
Existing multibeam inspection systems face challenges in accurately focusing beams over large sample surfaces due to non-uniform topographies, leading to inaccurate and time-consuming topographical map measurements.
Innovation Solution
An electron-optical apparatus and method that uses a stage, charged particle device, and sensing system with proximal and distal sensors to control focus and obtain topographical information by measuring sample surface positions, allowing for improved focus control and high-throughput inspection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a multibeam system projects very large numbers of individual beams onto a large Field of View simultaneously to achieve high throughput, then productivity is improved, but manufacturing precision deteriorates due to inaccurate focus control over large areas with non-uniform topographies
Solution Approach 1:
The sensing system is divided into multiple independent sensors distributed across the Field of View, with at least one sensor positioned in different quadrants relative to the multibeam path. This segmentation allows simultaneous measurement of topography at multiple locations, enabling independent focus control for different regions of the sample surface while maintaining high throughput multibeam processing.
2Manufacturing precision
If topographical maps are obtained by measurements to correct for non-uniform topographies, then manufacturing precision is improved, but loss of time increases because measurements are time-consuming
Solution Approach 1:
The sensing system obtains topographical information about the sample surface in advance, before the multibeam processing begins. By measuring the position of the sample surface at multiple locations prior to beam projection, the system can pre-calculate and apply focus corrections, eliminating the need for time-consuming measurements during the actual inspection process.
Solution Approach 2:
The sensing system operates continuously during multibeam processing, with sensors positioned to measure topography while the multibeam processes other areas. This allows topographical data collection to occur in parallel with sample processing, maintaining continuous useful action without interrupting the high-throughput inspection workflow.
3Manufacturing precision
If topographical maps are obtained in advance to correct focus, then manufacturing precision is improved, but reliability deteriorates because surface topography may change over time or due to stage positioning inaccuracies
Solution Approach 1:
The sensing system is designed to dynamically acquire topographical data at multiple locations during the multibeam processing sequence. Rather than relying on a single static topographical map obtained beforehand, the system continuously updates topographical information from multiple sensor positions, adapting to surface changes and stage positioning variations in real-time.
Data Source
AI summary
Apparatus and methods for obtaining topographical information about a sample surface. In one arrangement, a sensing system includes a group of proximal sensors for measuring positions of respective portions of a sample surface, and a distal sensor positioned more remotely from paths of sub-beams of a multibeam than the proximal sensors. The distal sensor measures a position of a portion of the sample surface relative to the distal sensor. A control system controls a charged particle device to process the sample surface in a multibeam processable area using the multibeam. A stage causes the multibeam processable area to move along a processing path in a reference frame of the sample. The sensing system uses at least the distal sensor to obtain topographical information about the sample surface in a selected portion of the processing path before the multibeam processable area reaches the selected portion of the processing path.