Acoustic Wafer Clearance Measurement for Non-Contact Tool Gap Control
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Solution Overview
Problem
Conventional techniques for measuring and controlling the clearance between fabrication tools and semiconductor or mask substrates are inadequate, particularly for larger, more fragile, and non-uniform workpieces, which increases the risk of accidental contact and fabrication errors.
Innovation Solution
The implementation of an acoustic measurement system using a transducer to measure the gap between fabrication tools and substrates in real-time during the fabrication process, allowing for precise control without physical contact, utilizing piezoelectric ultrasonic transducers and acoustic impedance matching layers to enhance sensitivity and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional measurement techniques are used to control clearance between fabrication tools and substrates, then the fabrication process can operate with simpler equipment, but the measurement precision and reliability are insufficient especially for larger substrates
Solution Approach 1:
The patent replaces conventional mechanical measurement systems with an acoustic measurement system. A transducer converts electrical signals to acoustic waves that propagate through the substrate, and another transducer detects the reflected acoustic waves. This acoustic field-based measurement method provides higher precision for clearance measurement between fabrication tools and substrates without requiring direct mechanical contact, thereby improving measurement precision while avoiding the complexity of mechanical contact systems.
Solution Approach 2:
The patent introduces acoustic waves as an intermediary medium to measure clearance. The acoustic waves propagate through the substrate and reflect off the fabrication tool, allowing indirect measurement of the gap distance. This intermediary approach enables precise measurement without physical contact between the measurement system and the substrate-tool interface, solving the problem of insufficient measurement precision for larger substrates.
2Productivity
If larger semiconductor substrates are used to increase production efficiency, then more circuits can be fabricated concurrently, but the substrates become more fragile and prone to warping increasing contact risk
Solution Approach 1:
The patent replaces mechanical contact-based clearance control with acoustic wave-based measurement. By using acoustic waves that propagate through the substrate and reflect off the fabrication tool, the system can precisely measure and control clearance without mechanical contact. This eliminates the risk of contact damage to larger, more fragile substrates while maintaining the productivity benefits of using larger wafers.
Solution Approach 2:
The patent implements a feedback control system where acoustic wave measurements of clearance are continuously monitored and fed back to adjust the position of fabrication tools. The system measures the actual clearance using acoustic waves, compares it to the desired clearance, and automatically adjusts tool positioning to maintain optimal gap distance. This feedback mechanism ensures reliable operation with larger substrates by preventing contact even when substrates warp or have surface irregularities.
3Manufacturing precision
If fabrication tools are moved closer to substrates to improve process control and reduce fluid disruptions, then process quality improves, but the risk of accidental contact increases
Solution Approach 1:
The patent replaces mechanical proximity sensing with acoustic wave-based clearance measurement. By transmitting acoustic waves through the substrate and detecting reflections from the fabrication tool, the system can precisely measure the gap distance at very close distances without risk of contact. This enables fabrication tools to operate at optimal close proximity for improved process control while the acoustic measurement system continuously monitors clearance to prevent contact.
Solution Approach 2:
The patent performs preliminary acoustic measurement of clearance before fabrication operations begin. The system measures the initial gap distance using acoustic waves, adjusts tool positioning to achieve optimal clearance, and establishes a safe operating distance before any fabrication process starts. This preliminary action ensures that tools are positioned correctly and safely close to substrates before processing begins, improving manufacturing precision while preventing contact.
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 precise and real-time control of the clearance between tools and substrates, reducing the risk of contact and improving the accuracy and safety of the fabrication process, especially for larger and more fragile workpieces, while allowing for continuous operation without disrupting the process.
Implementation Method 1
A transducer disposed on a bottom surface of the substrate opposite the gap conducts an acoustic signal through the substrate
Implementation Method 2
The transducer receives a first echo from a surface of the substrate that defines the gap and a second echo from a surface of the tool that further defines the gap
Implementation Method 3
utilizing piezoelectric ultrasonic transducers
Data Source
AI summary
Methods and systems disclosed herein use acoustic energy to determine a gap between a wafer and an integrated circuit (IC) processing system and/or determine a thickness of a material layer of the wafer during IC processing implemented by the IC processing system. An exemplary method includes emitting acoustic energy through a substrate and a material layer disposed thereover. The substrate is positioned within an IC processing system. The method further includes receiving reflected acoustic energy from a surface of the substrate and a surface of the material layer disposed thereover and converting the reflected acoustic energy into electrical signals. The electrical signals indicate a thickness of the material layer.