Wafer Alignment Using Exposure Tool Offset Measurement
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Solution Overview
Problem
Current wafer alignment methods suffer from reduced accuracy due to deviations in measurement tools, as alignment and overlay marks are measured by different tools, leading to enhanced total deviations.
Innovation Solution
The method involves using the exposure tool to measure the offset distance between pre-layer and current-layer alignment marks, eliminating the need for an overlay tool and replacing its function with the alignment mark, thereby avoiding additional tool deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If alignment marks and overlay marks are measured by different tools (exposure tool and overlay tool), then comprehensive measurement coverage is achieved, but total measurement deviations are enhanced and alignment accuracy deteriorates
Solution Approach 1:
The patent merges the functions of the exposure tool and overlay tool by enabling the exposure tool to perform both alignment marking and offset measurement. This consolidation eliminates the need for separate overlay tool measurements, thereby reducing cumulative measurement deviations and improving alignment accuracy while simplifying the measurement system architecture
Solution Approach 2:
The exposure tool is designed to perform multiple functions: creating alignment marks, creating overlay marks, and measuring offset distances between them. This multi-functionality eliminates the need for dedicated overlay measurement capabilities in separate equipment, reducing system complexity and measurement error accumulation
2Measurement precision
If overlay marks are used in addition to alignment marks, then overlay measurement capability is provided, but the complexity of the measurement system increases
Solution Approach 1:
The alignment mark structure is designed to serve dual purposes: it acts as both an alignment reference and an overlay measurement reference. The same mark formation process and measurement system are used for both functions, eliminating the need for separate overlay mark structures and reducing overall system complexity
Solution Approach 2:
The patent combines the alignment mark and overlay mark functions into a single integrated measurement approach using the same physical marks and measurement system. This merging eliminates redundant measurement infrastructure while maintaining comprehensive measurement capability
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 enhances wafer alignment accuracy by consolidating measurements within a single tool, reducing errors and eliminating the need for overlay marks, thus improving the precision of electric circuit pattern formation.
Implementation Method 1
the exposure tool illuminates the alignment marks, and the reflected light signal produced by the alignment marks is read by the exposure tool to obtain precise alignment
Data Source
AI summary
A method for wafer alignment includes the following steps. First, a wafer including a first material layer and a second material layer on the top of the first material layer is provided, wherein the first material layer includes a first alignment mark. Then, the wafer is aligned in an exposure tool. After that, the second material layer is patterned to form a second alignment mark. Finally, an offset distance between the first alignment mark and the second alignment mark is measured in the exposure tool.