Non-Zero Order Diffraction for Photolithography Process Control
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Solution Overview
Problem
Current scatterometry-based process control methods for photolithography face challenges such as long calculation times, inadequate real-time capabilities, and complex relationships between process parameters, which hinder their application in production environments requiring fast feedback.
Innovation Solution
A method involving the use of a periodic structure on a semiconductor wafer, illuminated with light to produce a non-zero order diffraction signal, which is matched with a reference signature to control manufacturing processes, specifically adjusting exposure energy and focus conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If scatterometry is used for process control with periodic structures, then measurement accuracy is improved, but calculation time increases making real-time control difficult
Solution Approach 1:
The patent pre-calculates and stores diffraction signatures for various structure parameters (width, height, side wall angle) in lookup tables before actual measurement. During real-time process control, the system only needs to query these pre-computed tables rather than performing complex calculations, thus achieving both high measurement accuracy and fast response time for real-time control
Solution Approach 2:
The system creates simplified models or representative signatures of complex diffraction patterns that can be quickly compared against measured data. Instead of performing full electromagnetic simulations during measurement, the system uses pre-computed signature copies that capture the essential characteristics needed for accurate parameter extraction
2Measurement precision
If detailed structural knowledge is required for scatterometry modeling, then measurement accuracy is improved, but setup time and complexity increase
Solution Approach 1:
The system transforms the complex inverse problem of extracting multiple structural parameters into a simpler matching problem by changing the parameter space. Instead of directly solving for all structure parameters simultaneously, the system uses pre-computed signatures across a range of parameter values and finds the best match, significantly reducing computational complexity and setup requirements
Solution Approach 2:
Material characterization and optical constant determination are performed in advance during system setup, and these values are stored for use in subsequent measurements. This preliminary characterization eliminates the need for repeated material analysis during production, reducing both setup complexity and measurement time while maintaining accuracy
3Area of stationary object
If the period of periodic structure is small, then space is saved on wafer, but diffraction signal strength decreases
Solution Approach 1:
The system transitions from relying solely on in-plane diffraction (which requires large periods) to utilizing out-of-plane diffraction signals by implementing oblique illumination geometry. This dimensional change allows the use of smaller periodic structures that would be necessary for high-density patterning while still generating sufficient diffraction signal strength for accurate measurement
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 enables efficient and accurate real-time control of photolithographic processes by reducing sensitivity to underlying layers and improving the reliability of measurements, thus enhancing the applicability of scatterometry-based systems in production settings.
Implementation Method 1
illuminating the periodic structure with a light, thereby producing a non-zero order diffraction signal
Data Source
AI summary
A method of controlling a manufacturing process, the method including the steps of a) providing a testing area with a periodic structure, where the periodic structure includes a series of sets of patterned features, b) illuminating the periodic structure with a light, thereby producing a non-zero order diffraction signal, c) collecting the diffraction signal to produce a test signature, d) matching the test signature with a reference signature, where the reference signature was previously produced by performing steps a), b), and c) with respect to a reference structure that is at least similar to the periodic structure, and e) controlling a manufacturing process using a control setting set associated with the matching reference signature.