Diffraction Overlay Target with Programmed Shifts
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Solution Overview
Problem
Current semiconductor processing techniques face challenges in accurately measuring overlay errors in complex structures with multiple patterns, leading to increased footprint and reduced throughput due to the need for multiple measurement pads and separate measurements.
Innovation Solution
A method using a target with a plurality of diffraction-based overlay pads, each with programmed shifts between periodic patterns, to simultaneously measure multiple overlay errors by illuminating with oblique or normal incident radiation and analyzing the resulting radiation using Mueller matrix elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate sets of targets are generated for each individual overlay error measurement, then measurement accuracy is improved, but the footprint increases and throughput is reduced
Solution Approach 1:
The patent combines multiple overlay error measurements into a single integrated target structure. Instead of using separate target sets for each overlay error, the invention creates one target containing multiple periodic patterns that can simultaneously measure all overlay errors. This merging approach maintains measurement accuracy while reducing the total number of targets needed and enabling simultaneous measurements, thereby improving throughput.
Solution Approach 2:
The patent designs a universal target structure that performs multiple measurement functions simultaneously. The single target with multiple periodic patterns can measure multiple different overlay errors in one measurement cycle, making the measurement system multi-functional. This eliminates the need for separate specialized targets for each measurement type, thus improving both space efficiency and measurement throughput.
2Measurement precision
If separate sets of targets are generated for each individual overlay error measurement, then measurement completeness is improved, but the footprint increases
Solution Approach 1:
The patent merges multiple measurement functions into a single compact target structure. By integrating multiple periodic patterns representing different overlay errors into one target, the invention reduces the total footprint required compared to using separate target sets. The combined target maintains the ability to measure all overlay errors completely while occupying less space on the substrate.
Solution Approach 2:
The patent arranges multiple periodic patterns in a spatial configuration within the single target, utilizing different spatial dimensions and orientations. This dimensional arrangement allows multiple overlay error measurements to be packed into a smaller footprint by efficiently using the available two-dimensional space, rather than requiring separate linear arrays of targets.
3Measurement precision
If multiple measurement pads are used to measure multiple overlay errors, then measurement completeness is improved, but measurement time increases
Solution Approach 1:
The patent merges multiple measurement functions into a single target that can be measured simultaneously. Instead of sequentially measuring multiple overlay errors using separate pads, the invention creates one integrated target where all overlay errors are measured in a single measurement operation. This eliminates the time required to switch between different measurement pads and enables parallel data acquisition, significantly reducing total measurement time.
Solution Approach 2:
The patent enables continuous measurement of all overlay errors in a single uninterrupted measurement cycle. The simultaneous measurement approach maintains continuous useful action throughout the measurement process, rather than introducing idle time for switching between different measurement pads or targets. This continuous measurement capability reduces the total time required to obtain complete overlay error data.
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 reduces the footprint and measurement time by allowing simultaneous determination of multiple overlay errors with fewer pads, improving alignment accuracy and process efficiency in semiconductor manufacturing.
Implementation Method 1
diffraction based overlay metrology
Data Source
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AI summary
A plurality of overlay errors in a structure is determined using a target that includes a plurality of diffraction based overlay pads. Each diffraction based overlay pad has the same number of periodic patterns as the structure under test. Additionally, each diffraction based overlay pad includes a programmed shift between each pair of periodic patterns. The pads are illuminated and the resulting light is detected and used to simultaneously determine the plurality of overlay errors in the structure based on the programmed shifts. The overlay errors may be determined using a subset of elements of the Mueller matrix or by using the resulting spectra from the pads.