Ultrasonic Cleaning Resonator Interference Pattern
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Solution Overview
Problem
Conventional ultrasonic and megasonic cleaning methods for semiconductor substrates are inadequate in minimizing damage and ensuring uniform removal of nanoparticulate contaminants, often causing non-uniform cleaning patterns and structural damage.
Innovation Solution
A device that uses a resonator to generate an interference pattern in the liquid at the solid-liquid interface, combined with a gas-containing treatment fluid that creates tunable gas dispersion, allowing for optimized bubble activity and reduced substrate damage by operating below the cavitation threshold, thereby enhancing cleaning uniformity and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional ultrasonic or megasonic cleaning methods are used to remove nanoparticulate contaminants, then particle removal is achieved, but substrate damage occurs and cleaning uniformity is poor
Solution Approach 1:
The patent changes the physical parameters of the cleaning system by introducing gas bubbles of controlled size distribution and operating below the cavitation threshold. This transforms the cleaning mechanism from violent cavitation to gentler microstreaming and shear stress, achieving particle removal without substrate damage
Solution Approach 2:
Gas bubbles serve as intermediaries between the ultrasonic field and the substrate surface. The bubbles generate microstreaming and shear stress that act on contaminants, indirectly removing particles without direct contact between high-energy ultrasound and the substrate, thus preventing damage
2Productivity
If conventional ultrasonic or megasonic cleaning methods are used to remove nanoparticulate contaminants, then particle removal is achieved, but cleaning uniformity is poor with non-uniform patterns
Solution Approach 1:
The patent creates local variations in bubble size distribution and concentration across the substrate surface, with different regions having optimized bubble characteristics. This local quality control ensures uniform cleaning action across the entire substrate, preventing non-uniform patterns while maintaining high particle removal efficiency
3Productivity
If high power ultrasonic cleaning is used to maximize particle removal, then cleaning efficiency improves, but the operating window becomes restricted and damage increases
Solution Approach 1:
The patent dynamically controls bubble generation and dissolution by adjusting gas flow rates and ultrasonic power in real-time. This dynamic control allows the system to operate below the cavitation threshold while maintaining effective cleaning, expanding the operating window and enabling efficient cleaning without restricting operational flexibility
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
The solution improves cleaning uniformity, increases process time efficiency, and expands the operating window for particle removal while reducing substrate damage, compared to conventional techniques which often associate high particle removal with significant damage.
Implementation Method 1
The resonator is moreover configured to introduce an interference pattern in the liquid and consequently distinct regions of pressure amplitude minima and maxima are generated at the solid-liquid interface
Implementation Method 2
a gas-containing fluid that generates a gas dispersion in the treatment fluid when the pressure is reduced
Implementation Method 3
Acoustically activated bubbles close to any liquid-surface interface causes (a) shear stress at the surface, which can lead to the removal of particulate contaminants from the surface
Implementation Method 4
microstreaming, which can lead to the enhancement of diffusion limited reactions beneficial for electrochemical deposition processes, etching, rinsing and mixing
Data Source
AI summary
A device and method for treating the surface of a semiconductor wafer provides a treatment fluid in the form of a dispersion of gas bubbles in a treatment liquid generated at acoustic pressures less than those required to induce cavitation in the treatment liquid. A resonator supplies ultrasonic or megasonic energy to the treatment fluid and is configured to create an interference pattern in the treatment fluid comprising regions of pressure amplitude minima and maxima at an interface of the treatment fluid and the semiconductor wafer.