Asymmetrical Alignment Mark Arrangement for Wafer Positioning
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Solution Overview
Problem
Conventional semiconductor wafer alignment processes using stepper or scanner apparatuses often experience alignment jumps due to factors like interference patterns, wrong shift settings, and symmetrical design of alignment marks, leading to inaccuracies in lithographic exposure.
Innovation Solution
An asymmetrical alignment mark arrangement with varying widths and pitches between neighboring marks is introduced, allowing for detection and avoidance of alignment jumps without relying on software solutions, by producing distinct optical signals for correct alignment and deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If symmetrical alignment marks with equal widths and pitches are used, then the alignment process is simple and consistent, but alignment jumps occur due to interference patterns and indistinct optical signals
Solution Approach 1:
The patent applies asymmetry by configuring alignment marks with different widths and/or different pitches between neighboring marks. This creates distinct optical signals when illuminated, allowing the detection system to reliably identify correct alignment positions and avoid alignment jumps, thereby resolving the contradiction between alignment reliability and arrangement simplicity.
2Reliability
If software solutions are used to detect alignment jumps, then alignment monitoring is enhanced, but the system becomes more complex and software may fail under certain conditions
Solution Approach 1:
The patent replaces the software-based detection system with an optical-based detection system. By using asymmetrical alignment marks that produce distinct optical signals under illumination, the system inherently provides reliable alignment jump detection through optical means, eliminating the need for complex software solutions and their associated failure modes.
3Measurement precision
If all alignment marks have the same width and pitch, then manufacturing is easier, but optical signals become indistinct making alignment detection difficult
Solution Approach 1:
The patent applies local quality by making specific alignment marks within the arrangement have different widths and/or pitches while others may remain standard. This localized variation creates sufficient optical signal distinction for precise alignment detection without requiring all marks to be different, thus balancing manufacturing ease with detection precision.
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
The asymmetrical alignment mark arrangement effectively detects and prevents alignment errors, enhancing the accuracy of wafer alignment during lithographic processes by providing clear optical signals for correct positioning.
Implementation Method 1
collecting reflected light from the alignment mark arrangement
Data Source
AI summary
In various embodiments, an alignment mark arrangement may include a plurality of alignment marks disposed next to each other in a row, wherein at least one of the following holds true: a first alignment mark of the plurality of alignment marks has a first width and a second alignment mark of the plurality of alignment marks has a second width that is different from the first width; a first pair of neighboring alignment marks of the plurality of alignment marks is arranged at a first pitch and a second pair of neighboring alignment marks of the plurality of alignment marks is arranged at a second pitch that is different from the first pitch.