Electron Beam Column Array for Overlay and EPE Measurement
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Solution Overview
Problem
Current optical metrology techniques lack sensitivity and throughput for measuring critical parameters such as edge placement error (EPE) and overlay errors in semiconductor devices, especially at advanced fabrication nodes below 20 nanometers, leading to challenges in yield control and device manufacturing accuracy.
Innovation Solution
An array of electron beam columns is used to measure multiple die features in a single wafer pass, with each column spatially separated and oriented at an oblique angle to correct alignment and positioning errors, enabling high-precision measurements of overlay, edge placement errors, and critical dimensions without scanning mode operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If optical metrology techniques are used to measure overlay and edge placement errors, then measurement speed is improved, but measurement precision deteriorates due to lack of sensitivity to buried structures and small pitch features
Solution Approach 1:
The patent replaces optical metrology systems with an electron beam-based measurement system. Electron beams provide superior sensitivity and resolution for measuring buried structures and small pitch features at advanced semiconductor nodes, eliminating the sensitivity limitations of optical techniques while maintaining high throughput through parallel measurement capabilities.
Solution Approach 2:
The patent divides the measurement task into multiple independent electron beam columns that can simultaneously measure different regions of the wafer. This segmentation enables parallel processing of multiple die features, achieving high throughput while each individual column maintains the precision needed for accurate overlay and EPE measurements.
2Adaptability or versatility
If specialized metrology target structures are used for optical overlay measurement, then measurement capability is improved, but manufacturing compliance deteriorates because targets do not conform to design rules
Solution Approach 1:
The patent enables the actual device structures themselves to serve as the measurement targets. By measuring real device features directly with electron beam columns, the system eliminates the need for separate specialized metrology targets, thereby maintaining full compliance with design rules while preserving overlay measurement capability.
3Measurement precision
If CD-SEM tools are used to measure overlay and EPE, then measurement precision is improved, but productivity deteriorates due to inability to achieve high throughput
Solution Approach 1:
The patent employs multiple electron beam columns operating in parallel to simultaneously measure different regions of the wafer. This parallel architecture maintains the high measurement precision of electron beam techniques while achieving the high throughput previously only possible with optical methods, thereby resolving the productivity limitation of sequential CD-SEM measurement.
Solution Approach 2:
The patent transitions from sequential single-column measurement to parallel multi-column measurement, adding the dimension of spatial parallelism. This enables simultaneous measurement of multiple die features across the wafer, achieving high throughput without sacrificing the precision benefits of electron beam measurement.
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 significantly improves measurement throughput and accuracy for semiconductor devices, allowing for precise control of EPE and overlay errors, thereby enhancing device yield and conforming to design rule dimensions even at nanometer scales.
Implementation Method 1
A specimen is scanned below a plurality of electron beam columns... each of the plurality of electron beam columns performs a one dimensional measurement
Data Source
AI summary
Methods and systems for performing measurements of multiple die with an array of electron beam columns are presented herein. The wafer is scanned in a direction parallel to the die rows disposed on the wafer. The electron beam measurement columns are spatially separated in a column alignment direction. The wafer is scanned in a direction that is oriented at an oblique angle with respect to the column alignment direction such that each electron beam column measures the same row of die features on different die during the same wafer pass. The wafer is oriented with respect to the array of electron beam columns by rotating the wafer, rotating the electron beam columns, or both. In further aspects, each measurement beam is deflected to correct alignment errors between each column and the corresponding die row to be measured and to correct wafer positioning errors reported by the wafer positioning system.