Overlay Mask Multi-Layer Alignment Measurement
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Solution Overview
Problem
Conventional overlay marks in integrated circuits (ICs) primarily measure alignment accuracy between adjacent layers, failing to effectively address displacement issues between non-adjacent layers, which can compromise IC performance.
Innovation Solution
An overlay mask design featuring a plurality of first, second, and third patterns arranged within different pitches, with portions of the third patterns alternating with the first and second patterns in specific directions, allowing for more diverse mark design and convenient overlay measurement across multiple layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional overlay marks measure only adjacent layers, then the measurement process is simple, but alignment accuracy between non-adjacent layers cannot be ensured
Solution Approach 1:
The patent combines multiple overlay measurement functions into a single integrated mark structure. The overlay mark includes first, second, and third patterns that can simultaneously measure alignment between multiple layers (e.g., layer 1-2, 2-3, 1-3) rather than requiring separate marks for each adjacent layer pair. This merging approach enables comprehensive multi-layer overlay measurement while maintaining a unified mark design.
Solution Approach 2:
The overlay mark is designed with universal applicability for measuring alignment across multiple layers. The third pattern serves multiple functions by being measurable against both the first and second patterns, allowing the same mark structure to provide alignment data for various layer combinations. This multi-functionality eliminates the need for different mark designs for different measurement scenarios.
2Productivity
If multiple overlay measurements are performed separately for different layer pairs, then each measurement can be precise, but the total measurement time increases
Solution Approach 1:
The patent merges multiple overlay measurements into a single integrated mark that can be measured simultaneously. By incorporating first, second, and third patterns in specific spatial relationships, the system enables concurrent measurement of alignment between multiple layer pairs (e.g., L1-L2, L2-L3, L1-L3) in one measurement operation, thereby improving productivity and reducing measurement time.
Solution Approach 2:
The overlay mark is pre-configured with multiple patterns positioned at predetermined locations and orientations before the measurement process begins. This preliminary arrangement of patterns allows the measurement system to capture all necessary alignment data in a single operation without requiring sequential measurements for each layer pair, thus eliminating time loss.
3Area of stationary object
If overlay marks use uniform pattern arrangement, then manufacturing is simple, but area utilization efficiency is reduced
Solution Approach 1:
The patent applies local quality by varying the arrangement and configuration of patterns in different regions of the overlay mark. Instead of uniform arrangement throughout, specific local areas contain optimized pattern configurations tailored to their measurement functions. For example, different regions may contain patterns optimized for different measurement directions or layer pairs, maximizing area utilization while maintaining manufacturability through localized design variations.
Data Source
AI summary
An overlay mask includes a plurality of first patterns, a plurality of second patterns and a plurality of third patterns. The first patterns are arranged within a first pitch. The second patterns are arranged within a second pitch. A first portion of the third patterns are arranged alternately with the first patterns, within the first pitch, and a second portion of the third patterns are arranged alternately with the second patterns, within the second pitch, and the first pitch is not equal to the second pitch.