Composite Metrology for High Resolution CD Uniformity
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Solution Overview
Problem
Current optical metrology systems for semiconductor wafers lack the necessary spatial resolution and throughput to effectively measure the uniformity of thin films and critical dimensions, particularly in small regions, which is crucial for semiconductor memory chip production.
Innovation Solution
A composite metrology approach combining broadband reflectometry or spectroscopic ellipsometry with high spatial resolution techniques like Beam Profile Reflectometer (BPR) or Beam Profile Ellipsometer (BPE), using calibration samples to create a correlation table that allows for rapid, high-resolution measurements and interpolation to derive parameter values, potentially aided by neural networks for adaptive correlation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If broadband reflectometry or spectroscopic ellipsometry is used, then measurement accuracy is improved, but spatial resolution deteriorates due to larger spot sizes
Solution Approach 1:
The patent combines broadband reflectometry/spectroscopic ellipsometry (for accurate parameter measurement) with high spatial resolution techniques (BPR or BPE) into a composite metrology system. The broadband technique provides accurate thin film and CD parameters, while the high spatial resolution technique provides the necessary spatial resolution for mapping uniformity across small regions.
Solution Approach 2:
The patent introduces a correlation table as an intermediary that links the broadband measurements (accurate but low spatial resolution) with the high spatial resolution measurements. This correlation table enables the transfer of accurate parameter information from broadband measurements to the high spatial resolution measurement grid, resolving the contradiction between accuracy and spatial resolution.
2Manufacturing precision
If high spatial resolution measurements are taken at many points, then uniformity evaluation is improved, but measurement time increases making the process too slow
Solution Approach 1:
The patent performs preliminary measurements using broadband reflectometry or spectroscopic ellipsometry to obtain accurate thin film and CD parameters before conducting the high spatial resolution mapping. These preliminary measurements are used to create the correlation table, which then enables rapid parameter extraction during the uniformity mapping phase without requiring time-consuming complex regressions at each measurement point.
Solution Approach 2:
The patent creates a correlation table that copies the relationship between broadband measurements and high spatial resolution measurements. This correlation table serves as a lookup reference that enables rapid parameter determination during uniformity mapping, avoiding the need to perform complex regressions at each of the many measurement points required for high-resolution uniformity evaluation.
3Measurement precision
If complex regressions are performed at each measurement point, then parameter accuracy is improved, but processing time increases beyond acceptable limits
Solution Approach 1:
The patent performs the complex regression analysis in advance during the calibration phase using broadband measurements, and stores the results in a correlation table. During subsequent high spatial resolution measurements, the system simply looks up parameters in this pre-computed correlation table rather than performing complex regressions at each measurement point, dramatically reducing processing time while maintaining parameter accuracy.
Solution Approach 2:
The patent copies the complex regression results into a correlation table that can be rapidly queried. Instead of repeating the complex regression calculations at each measurement point, the system uses the pre-computed correlation table to quickly retrieve accurate parameter values, eliminating the time-consuming aspect while preserving the accuracy benefits of complex regression analysis.
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 method enables high-resolution, high-throughput measurements of thin film and critical dimension parameters, improving the ability to assess uniformity and variability within small regions on semiconductor wafers, thereby enhancing process control and efficiency.
Implementation Method 1
broadband reflectometry (BB) and spectroscopic ellipsometry (SE)
Implementation Method 2
Beam Profile Ellipsometer (BPE)
Implementation Method 3
use a highly focused single wavelength laser output for a probe beam
Implementation Method 4
Beam Profile Reflectometer (BPR)
Data Source
AI summary
An optical metrology method is disclosed for evaluating the uniformity of characteristics within a semiconductor region having repeating features such a memory die. The method includes obtaining measurements with a probe laser beam having a spot size on the order of micron. These measurements are compared to calibration information obtained from calibration measurements. The calibration information is derived by measuring calibration samples with the probe laser beam and at least one other technology having added information content. In the preferred embodiment, the other technology includes at least one of spectroscopic reflectometry or spectroscopic ellipsometry.