Wafer Imaging Metrology Using LED Spectral Scans for High Throughput
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Solution Overview
Problem
Existing optical metrology techniques for semiconductor wafers are time-consuming and limited in throughput, particularly when measuring full wafer maps or large areas, and require complex equipment and high computational resources.
Innovation Solution
A fast full wafer scan metrology system using LEDs for illumination with different wavelengths, combined with narrow and elongated effective fields of view from area scan cameras, allows for rapid imaging and spectral analysis of the entire wafer by overlapping frames, enabling efficient measurement without significant throughput reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional optical metrology techniques (spectral reflectometry, scatterometry, ellipsometry) are used to measure critical dimensions on semiconductor wafers, then measurement precision is improved, but productivity deteriorates due to time-consuming sequential site-by-site measurement
Solution Approach 1:
The patent divides the wafer surface into multiple regions (e.g., 10-50 measurement sites) and uses parallel measurement channels to simultaneously measure multiple regions. Each channel independently measures a specific region, allowing concurrent data collection across the wafer surface, thereby increasing throughput while maintaining precision through dedicated measurement channels for each region.
2Area of stationary object
If hyperspectral imaging is used to obtain full wafer images with broad light spectrum, then area coverage is improved, but device complexity and cost increase due to requirements for fast computers, highly sensitive detectors, and large data storage resources
Solution Approach 1:
The patent extracts only the necessary spectral information by using narrowband LED illumination at specific wavelengths rather than capturing the full broad spectrum. This selective approach extracts only the critical dimension measurement data needed, eliminating the need for complex hyperspectral processing systems while still achieving full wafer area coverage through multiple measurement sites.
Solution Approach 2:
The patent uses inexpensive LED light sources with narrow spectral bandwidths instead of expensive broadband light sources and hyperspectral detectors. The LEDs provide sufficient spectral information for CD measurement at a fraction of the cost and complexity of hyperspectral imaging systems, achieving the same measurement goal with simpler, more affordable components.
3Measurement precision
If small spot size (10-50 microns) is used in scatterometry tools, then measurement precision is improved, but area coverage deteriorates making full wafer mapping problematic
Solution Approach 1:
The patent segments the wafer surface into multiple discrete measurement sites distributed across the wafer surface. Each site is measured with a focused small spot size to maintain precision, while the collection of multiple segmented measurements across different wafer regions provides comprehensive area coverage and enables full wafer mapping through systematic traversal of all measurement sites.
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
Enables rapid, efficient, and cost-effective full wafer imaging and metrology with improved throughput, providing comprehensive wafer maps and parameter measurements without the need for extensive computational resources.
Implementation Method 1
A fast full wafer scan metrology system using LEDs for illumination with different wavelengths
Implementation Method 2
generated image data represent the light intensity reflected or scattered from the tested wafer
Data Source
AI summary
A method for optical metrology of a sample, the method may include illuminating areas of the sample by sets of pulses of different wavelengths, during a movement of a variable speed of the sample; collecting light reflected from the sample, as a result of the illuminating, to provide sets of frames, each set of frames comprises partially overlapping frames associated with the different wavelengths; and processing the frames to provide optical metrology results indicative of one or more evaluated parameters of elements of the areas of the sample; wherein the processing is based on a mapping between the sets of frames and reference measurements obtained by an other optical metrology process that exhibits a higher spectral resolution than a spectral resolution obtained by the illuminating and the collecting.