Surface Acoustic Wave Metrology for Substrate Analysis
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Solution Overview
Problem
Current methods for analyzing structured substrates using surface acoustic waves lack efficiency in distinguishing between surface and depth acoustic waves, limiting the ability to accurately decode substrate properties and characteristics.
Innovation Solution
A noncontact optical system utilizing a pump element to induce surface acoustic waves and a probe element to measure transient changes, with nanolight elements and NSOM devices operating in the near or far field, allowing for efficient transmission and measurement of surface acoustic waves, enabling the differentiation between Rayleigh and Lam waves and providing detailed substrate characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard opto-acoustic systems or contact mask opto-acoustic systems are used, then acoustic waves can be generated and measured, but the ability to distinguish between surface and depth acoustic waves is insufficient
Solution Approach 1:
The patent segments the acoustic wave measurement into two distinct components: surface acoustic waves (Rayleigh waves) and depth acoustic waves (longitudinal waves). By using a noncontact optical system with specific pump and probe beam geometries, the system can selectively generate and measure each wave type independently, enabling clear distinction between surface and depth acoustic wave characteristics without requiring complex additional hardware.
Solution Approach 2:
The patent introduces light as an intermediary medium to generate and detect acoustic waves. The pump beam serves as the intermediary to generate acoustic waves through optical absorption and thermal expansion, while the probe beam acts as an intermediary to detect surface displacements. This optical intermediary enables noncontact measurement and provides the precision needed to distinguish between different acoustic wave types.
2Productivity
If noncontact optical system with nanolight elements is used, then transmission efficiency is highly efficient exceeding expectations, but device complexity increases
Solution Approach 1:
The patent utilizes nanolight elements with specifically engineered parameters including aperture dimensions less than 100 nm (or even less than 50 nm), periodic arrangements with pitches between 100-500 nm, and precise geometric configurations. These parameter optimizations enable extraordinary transmission efficiency that exceeds conventional diffraction limits, allowing highly efficient light transmission despite the complex nanoscale structures.
3Measurement precision
If pump and probe beams are used to induce and measure surface acoustic waves, then substrate characteristics can be determined, but the system requires precise timing control
Solution Approach 1:
The patent employs periodic pumping at specific frequencies to generate surface acoustic waves with well-defined temporal characteristics. By using periodic pump beams at frequencies that match the resonant frequencies of the substrate, the system creates stable, repeatable acoustic wave patterns that are easier to measure and analyze, reducing the complexity of timing control while maintaining high measurement precision.
Solution Approach 2:
The patent implements preliminary timing synchronization where the pump and probe beams are pre-configured with specific time delays optimized for the expected acoustic wave propagation times. This preliminary setup allows the system to automatically capture the acoustic wave signals at the optimal moments without requiring complex real-time timing adjustments during operation.
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 system effectively analyzes surface acoustic waves, enhancing the understanding of substrate properties by allowing for precise measurement and characterization of surface and depth acoustic waves, improving the reliability of semiconductor device manufacturing and yield.
Implementation Method 1
The pump element directs light or radiation to a surface of a substrate to induce a surface acoustic wave therein
Implementation Method 2
The light or radiation incident on the substrate is selected to optimize the creation of the surface acoustic waves
Implementation Method 3
Light coded with information regarding the transient change in the surface of the substrate is returned to the probe element from the substrate
Data Source
AI summary
A system for imposing and analyzing surface acoustic waves in a substrate to determine characteristics of the substrate is disclosed. Optical elements and arrangements for imposing and analyzing surface acoustic waves in a substrate are also disclosed. NSOM's, gratings, and nanolight elements may be used to impose surface acoustic waves in a substrate and may also be used to measure transient changes in the substrate due to the passage of surface acoustic waves therethrough.