Optical Overlay Metrology for Symmetric Unit Cell Patterning
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Solution Overview
Problem
The increasing complexity of semiconductor manufacturing requires precise control of overlay and critical dimension (CD) in lithographic processes to ensure accurate patterning, as errors can lead to device failure and electrical issues, necessitating improved metrology techniques for real-time monitoring and adjustment.
Innovation Solution
A method involving a hardware computer system that determines overlay by analyzing optical characteristic values from radiation redirected by a unit cell with geometric symmetry, using mathematical models to simulate changes in optical response and calculate weights for accurate overlay measurement, enabling separate determination of overlay values between different parts of the unit cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional lithographic processes are used for manufacturing semiconductor devices, then production can proceed with standard equipment and methods, but overlay and critical dimension errors occur leading to device failure and electrical issues
Solution Approach 1:
The patent implements a feedback mechanism where overlay measurements are taken on the substrate using a metrology apparatus, and these measurements are used to adjust patterning process parameters in real-time. The system determines overlay values between different layers or target portions and feeds this information back to the lithographic apparatus to correct positioning errors, thereby maintaining manufacturing precision and device reliability
Solution Approach 2:
The patent replaces direct mechanical measurement and adjustment methods with optical measurement techniques. Instead of using mechanical probes or contact-based alignment methods, the system uses radiation (light) to measure overlay parameters and determines process parameters through optical characteristic analysis, enabling non-contact, high-precision measurements that don't interfere with the manufacturing process
2Measurement precision
If overlay measurements are performed using traditional metrology methods, then basic alignment can be monitored, but precise determination of overlay values between different parts of the unit cell cannot be achieved
Solution Approach 1:
The patent divides the measurement task into segments by determining overlay values between different parts of the unit cell separately. Instead of measuring overall overlay in a single step, the system breaks down the measurement into multiple comparative measurements between adjacent target portions or layers, allowing for more precise local overlay determination while using a systematic approach to manage complexity
Solution Approach 2:
The patent creates a universal metrology method that can determine overlay values for different parts of the unit cell using the same measurement and calculation framework. The method is applicable to various lithographic processes and substrate types, providing a multi-functional solution that handles different measurement scenarios through a unified approach, thereby reducing overall system complexity
3Manufacturing precision
If real-time monitoring and adjustment of patterning parameters is implemented, then manufacturing precision can be maintained, but process complexity and measurement requirements increase
Solution Approach 1:
The patent implements a self-service measurement system where the substrate itself contains target structures that serve as built-in measurement references. These targets are integrated into the product substrate, eliminating the need for separate dedicated measurement substrates. The system uses these self-contained targets to perform real-time overlay measurements and adjustments, reducing external complexity while maintaining precision
Solution Approach 2:
The patent focuses on determining and adjusting specific patterning process parameters such as overlay values, focus, and exposure dose through measurements of optical characteristics. By identifying and controlling the most critical parameters that affect manufacturing precision, the system achieves high accuracy without needing to monitor and control all possible process variables, thereby managing complexity effectively
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 allows for precise measurement and adjustment of overlay and CD, reducing errors and improving the accuracy of the patterning process, thereby enhancing the reliability and performance of semiconductor devices.
Implementation Method 1
obtaining a detected representation of radiation redirected by one or more physical instances of a unit cell
Implementation Method 2
obtaining a detected representation of radiation redirected by one or more physical instances of a unit cell
Data Source
AI summary
A method of determining overlay of a patterning process, the method including: obtaining a detected representation of radiation redirected by one or more physical instances of a unit cell, wherein the unit cell has geometric symmetry at a nominal value of overlay and wherein the detected representation of the radiation was obtained by illuminating a substrate with a radiation beam such that a beam spot on the substrate was filled with the one or more physical instances of the unit cell; and determining, from optical characteristic values from the detected radiation representation, a value of a first overlay for the unit cell separately from a second overlay for the unit cell that is also obtainable from the same optical characteristic values, wherein the first overlay is in a different direction than the second overlay or between a different combination of parts of the unit cell than the second overlay.