Non-orthogonal Target Design for Semiconductor Misregistration Measurement
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Solution Overview
Problem
Current methods for measuring misregistration in semiconductor device manufacturing are limited by low signal-to-noise ratios, as noise generated by target edges propagates in the same direction as desired output signals, making it difficult to accurately determine misregistration between layers.
Innovation Solution
A target design featuring periodic structures with pitch axes not parallel to edge axes, minimizing noise overlap with desired output signals by orienting pitch axes at 45° angles to edge axes, and using scatterometry metrology tools to analyze output signals and calculate misregistration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional target designs with pitch axes parallel to edge axes are used, then the measurement process is simple, but noise generated by target edges propagates in the same direction as desired output signals, resulting in low signal-to-noise ratio
Solution Approach 1:
The patent applies asymmetry by orienting the pitch axis of periodic structures at a specific angle (e.g., 45 degrees) relative to the edge axes of the target, rather than parallel alignment. This asymmetric orientation causes noise generated by target edges to propagate in different directions than the desired output signals, thereby improving the signal-to-noise ratio in misregistration measurements.
Solution Approach 2:
The patent introduces a new dimensional relationship by defining the pitch axis at an angular orientation relative to the edge axes, creating a multi-dimensional geometric configuration. This angular dimension separates the noise propagation direction from the signal detection direction, resolving the contradiction between measurement precision and structural simplicity.
2Measurement precision
If pitch axes are oriented at 45° angles to edge axes, then noise overlap with desired output signals is minimized, but target design and fabrication become more complex
Solution Approach 1:
The patent changes the geometric parameter of the pitch axis orientation from the conventional parallel alignment (0 degrees) to a specific angular orientation (e.g., 45 degrees) relative to the edge axes. This parameter change optimizes the separation between noise and signal propagation directions, improving measurement accuracy while the angular relationship provides clear fabrication guidelines.
Solution Approach 2:
The patent performs preliminary geometric design by pre-defining the angular relationship between pitch axes and edge axes in the target structure. This preliminary configuration ensures that when the target is fabricated and measured, the noise and signal paths are already optimally separated, reducing the need for complex post-processing or alignment adjustments during manufacturing.
3Measurement precision
If multiple pairs of periodic structures with different orientations are used, then comprehensive misregistration measurement is achieved, but target size and complexity increase
Solution Approach 1:
The patent implements multi-functionality by designing a single target structure that can measure misregistration in multiple directions (e.g., x and y directions) simultaneously. By incorporating multiple pairs of periodic structures with different angular orientations, the target serves multiple measurement functions within one integrated design, reducing the need for separate targets for different measurement directions.
Solution Approach 2:
The patent merges multiple measurement functions into a single target by combining multiple pairs of periodic structures with different orientations in one target area. This consolidation allows comprehensive misregistration measurement across different directions while optimizing the use of wafer space, achieving multi-directional measurement capability without proportionally increasing the total target area.
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 design improves the signal-to-noise ratio of misregistration measurement output signals, allowing for more accurate determination of layer misregistration and enhancing the precision of semiconductor device manufacturing processes.
Implementation Method 1
using scatterometry metrology tools to analyze output signals and calculate misregistration
Data Source
AI summary
A target for use in the measurement of misregistration between layers formed on a wafer in the manufacture of semiconductor devices, the target including a first pair of periodic structures (FPPS) and a second pair of periodic structures (SPPS), each of the FPPS and the SPPS including a first edge, a second edge, a plurality of first periodic structures formed in a first area as part of a first layer and having a first pitch along a first pitch axis, the first pitch axis not being parallel to either of the first edge or second edge, and a plurality of second periodic structures formed in a second area as part of a second layer and having the first pitch along a second pitch axis, the second pitch axis being generally parallel to the first pitch axis.