Integrated Overlay Target Design for Electron Beam Metrology
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current semiconductor manufacturing processes face challenges in accurately measuring overlay errors between patterned layers, which affects yield and production time, as conventional overlay metrology techniques are not sufficient for complex devices and require separate targets for imaging and scatterometry methods.
Innovation Solution
The development of a target design incorporating electron beam overlay elements and AIMid elements with diagonal fine segmentation and regions of interest, allowing for combined optical and electron beam overlay measurements, reducing measurement time and improving accuracy by integrating both technologies into a single target.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate targets are used for imaging and scatterometry overlay measurements, then each measurement method can be optimized independently, but the total measurement time increases and wafer area is wasted
Solution Approach 1:
The patent combines imaging-based overlay (IBO) targets and scatterometry-based overlay (SBO) targets into a single integrated overlay target structure. The target includes both periodic grating structures for scatterometry measurement and asymmetric structures for imaging measurement, allowing both measurement methods to be performed on the same target area simultaneously, thereby reducing total measurement time and avoiding duplicate wafer area usage
Solution Approach 2:
The integrated target design serves multiple functions: it provides measurement features for both imaging-based overlay measurement and scatterometry-based overlay measurement. The target structure includes periodic gratings that can be measured by scatterometry methods and asymmetric elements that can be measured by imaging methods, making the target universal for both measurement techniques
2Measurement precision
If conventional overlay targets are used, then the target structure is simple, but the measurement accuracy is insufficient for complex semiconductor devices
Solution Approach 1:
The overlay target is segmented into distinct functional regions: periodic grating structures for scatterometry measurement and asymmetric structures for imaging measurement. Each segment is optimized for its specific measurement method, with the periodic gratings providing precise diffraction patterns for scatterometry and the asymmetric elements providing clear positional references for imaging-based measurement
Solution Approach 2:
The target employs a composite structural design that integrates different geometric patterns (periodic gratings and asymmetric structures) within a single target. This composite approach allows the target to provide distinct measurement signals for both imaging and scatterometry methods, enhancing overall measurement accuracy for complex semiconductor device structures
3Reliability
If multiple overlay measurement methods are performed separately, then comprehensive overlay data can be obtained, but the processing time and computational resources increase
Solution Approach 1:
The patent merges imaging-based and scatterometry-based measurement capabilities into a single target structure, enabling simultaneous or integrated measurement processes. This integration allows comprehensive overlay error detection from multiple measurement approaches while reducing the total processing time and computational overhead compared to performing separate measurements
Data Source
AI summary
Electron beam overlay targets and method of performing overlay measurements on a target using a semiconductor metrology tool are provided. One target includes a plurality of electron beam overlay elements and a plurality of two-dimensional elements that provide at least one two-dimensional imaging. The plurality of two dimensional elements are an array of evenly-spaced polygonal gratings across at least three rows and at least three columns. Another target includes a plurality of electron beam overlay elements and a plurality of AIMid elements. Each of the electron beam overlay elements includes at least two gratings that are overlaid at a perpendicular orientation to each other. The plurality of AIMid elements includes at least two gratings that are overlaid at a perpendicular orientation to each other.