Wafer Test Structures for Electrical Misalignment Characterization
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Solution Overview
Problem
The semiconductor fabrication process faces challenges in efficiently characterizing and controlling feature misalignment across a wafer, which affects the electrical performance of components like transistors, and current inline measurement methods are time-consuming and impractical for every shot.
Innovation Solution
The implementation of a semiconductor wafer with intentionally misaligned electrical components, such as transistors, having different spacing distances along specific directions, and a testing system that uses wafer probe pads to electrically test these components and determine misalignment distances based on their performance parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If inline measurements are performed to characterize misalignment, then measurement precision is improved, but loss of time increases significantly
Solution Approach 1:
The wafer is divided into multiple unit areas or shots, each containing test structures that can be independently characterized. This segmentation allows selective measurement of critical areas rather than comprehensive wafer-wide measurements, reducing overall measurement time while maintaining precision for key regions.
Solution Approach 2:
Instead of measuring every shot across the wafer, the invention performs measurements on selected unit areas or shots that contain the test structures. This partial measurement approach provides sufficient misalignment characterization data without the time cost of complete wafer coverage.
2Loss of information
If every shot across the wafer is measured, then measurement completeness is improved, but productivity decreases
Solution Approach 1:
The wafer surface is segmented into multiple unit areas with specific test structures placed in selected areas. By concentrating measurement resources on these segmented test areas rather than attempting to measure every shot, the system achieves practical misalignment characterization while preserving overall wafer productivity.
3Measurement precision
If multiple electrical components with different spacing distances are formed, then misalignment characterization capability is improved, but device complexity increases
Solution Approach 1:
Different unit areas or shots contain test structures with different structural feature spacing distances, creating local variations in component geometry. This local quality differentiation enables the extraction of misalignment information across multiple spacing conditions without requiring every component on the wafer to be complex.
Solution Approach 2:
Multiple copies of test structures are created across different unit areas, with each copy having different spacing distances between structural features. These replicated structures with varied geometries provide comprehensive misalignment characterization data while keeping individual component designs relatively simple.
Data Source
AI summary
A method includes performing a fabrication process that fabricates a wafer having an upper region and unit areas arranged in rows along a first direction and columns along an orthogonal second direction and respective scribe streets between adjacent unit areas to: form first and second electrical components on or in the upper region in respective unit areas or scribe streets, the first and second electrical components spaced apart from one another and including structural features with different respective first and second spacing distances along the first direction.