Semiconductor Wafer Inspection via Swath Segmentation
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Solution Overview
Problem
The photolithography process for semiconductor device fabrication faces challenges with interference and diffraction of light due to decreasing distances between mask patterns, leading to defects in the printed wafer layout, which existing inspection methods fail to accurately detect and correct.
Innovation Solution
A method and system for inspecting semiconductor wafers by scanning multiple swaths, producing and comparing image sets to detect defects, using a computer to process image data and select reference images for accurate defect detection, and adjusting photolithography conditions based on detected defects to minimize defect occurrence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple image sets from different inspection swaths are combined to produce reference images for defect detection, then the coverage area increases, but misalignment and detection accuracy deteriorate due to scanning position variations
Solution Approach 1:
The patent divides the wafer inspection into multiple separate inspection swaths, each processed independently to produce its own reference image. This segmentation allows each swath to be handled with precise local alignment, avoiding the misalignment problems that would occur if trying to combine all swaths into a single reference image. The segmentation principle resolves the contradiction by enabling area coverage through multiple swaths while maintaining detection accuracy through independent processing of each swath.
2Productivity
If distances between mask patterns are decreased to increase circuit density, then the productivity improves, but light interference and diffraction increase causing printing defects
Solution Approach 1:
The patent employs a feedback mechanism where the inspection system detects actual printing defects caused by light interference and diffraction, and this information is fed back to adjust the photolithography process parameters. The system compares target images with reference images to identify defects, then uses this feedback to optimize printing conditions, enabling higher circuit density while compensating for the harmful optical effects through process adjustment.
3Device complexity
If conventional inspection methods are used to detect wafer defects, then the device complexity remains low, but defect detection accuracy is insufficient for modern semiconductor requirements
Solution Approach 1:
The patent transitions from conventional single-swath inspection to multi-swath inspection with independent reference image generation for each swath. This dimensional change in the inspection approach - treating each swath as a separate inspection dimension - enables higher defect detection accuracy by allowing precise local reference creation and comparison, while the modular nature of the approach keeps the overall system complexity manageable through standardized processing steps.
Data Source
AI summary
A method of inspecting a semiconductor wafer is provided, the method includes scanning a plurality of inspection swaths on a wafer to obtain a plurality of image sets and producing a plurality of reference images from the plurality of image sets, respectively. The method of inspecting a semiconductor wafer further includes selecting a plurality of target images from the plurality of image sets, respectively. The method of inspecting a semiconductor wafer additionally includes comparing each reference image of the plurality of reference images with each target image of the plurality of target images to detect a defect image from each of the plurality of target images. A reference image being compared and a target image being compared are images scanned from the same inspection swath.