Ultrasonic RF Output Tuning With Phase-Aligned Resonance Control
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Solution Overview
Problem
Conventional ultrasonic systems for cleaning and processing parts, such as semiconductor wafers, face issues with damage caused by single frequency or narrow band ultrasound, leading to resonant and cavitation-related damages, non-uniform processing, and inefficiencies with varying chemistries, particularly in megasonic systems where transducer reliability is compromised due to high frequency stress and beam effects.
Innovation Solution
A system with an RF generator that automatically tunes its output circuit to align voltage and current phases using a tunable resonant frequency, phase detection, and adjustable inductance, ensuring optimal ultrasonic transmission by positioning a moveable metallic core within a variable inductor, thereby reducing resonant frequencies and enhancing processing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If single frequency or narrow band ultrasound is used, then the system is simple to operate, but resonant and cavitation-related damages occur
Solution Approach 1:
The patent implements automatic frequency sweeping that dynamically changes the operating frequency over time, transitioning from static single-frequency operation to dynamic multi-frequency operation. This prevents resonant and cavitation damages while maintaining ease of operation through automated control.
Solution Approach 2:
The system automatically changes the frequency parameter during operation, sweeping through a range of frequencies rather than operating at a fixed frequency. This parameter change eliminates harmful resonant effects while the automated sweeping mechanism keeps the system easy to operate.
2Device complexity
If single frequency ultrasound is used, then the generator design is simple, but processing uniformity deteriorates
Solution Approach 1:
The generator automatically sweeps through multiple frequencies dynamically, preventing standing waves and improving processing uniformity. The automated frequency modulation adds complexity but maintains simplicity through intelligent control algorithms.
Solution Approach 2:
The system incorporates automatic frequency sweeping with control mechanisms that monitor and adjust the operating frequency to maintain optimal processing conditions, improving uniformity while managing complexity through automated feedback control.
3Manufacturing precision
If high frequency megasonic transducers are used, then processing precision is improved, but transducer reliability deteriorates
Solution Approach 1:
The system dynamically sweeps through frequencies including megasonic ranges, allowing high-frequency processing precision while avoiding continuous operation that would compromise transducer reliability. The automated frequency modulation enables occasional high-precision processing without sustained stress.
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 solution reduces resonant damages, improves processing uniformity, and increases ultrasonic activity by aligning voltage and current phases, addressing the limitations of conventional systems and enhancing the reliability and efficiency of ultrasonic processing across different frequencies and chemistries.
Implementation Method 1
a phase detector circuit for measuring a phase differential between the output voltage waveform and the output current waveform, wherein the phase detector circuit has an XOR gate that receives a voltage signal input and a current signal input
Implementation Method 2
an adjustable inductor, and a motor controller evaluates the updated positioning instructions and then automatically repositions or maintains the position of a moveable metallic core within a variable inductor
Implementation Method 3
Typical ultrasound transducers are, for example, made from materials such as piezoelectrics, ceramics, or magnetostrictive
Implementation Method 4
Other ultrasound transducers are made of alloys that possess magnetostriction properties which cause them to expand or contract under the influence of a magnetic field
Implementation Method 5
The interaction between the energized liquid and the object create the desired cleaning or processing action
Implementation Method 6
By driving the transducer at its operational resonant frequency, e.g., 18 kHz, 25 kHz, 40 kHz, 670 kHz or 1 MHz, the transducer imparts ultrasonic energy to the liquid
Data Source
AI summary
A system for delivering ultrasonic energy to a transducer load has at least one ultrasonic transducer, and a radio frequency (RF) generator for delivering RF power to the transducer load. The RF generator has an output circuit that has at least one tunable resonant frequency, a voltage circuitry system that senses an output voltage waveform, a current circuitry system that senses an output current waveform, and a phase detector circuit for measuring a phase differential between the output voltage waveform and the output current waveform. The phase detector circuit has an XOR gate that receive a voltage signal input and a current signal input, a comparator that compares the measured phase differential to a desired phase difference to generate a phase value; and a motor controller evaluates the phase value and based on the phase value automatically repositions or maintains the position of a moveable metallic core within a variable inductor, to generate a desired ultrasonic transmission in a liquid wherein the voltage and current phases are approximately aligned.