Megasonic Cleaner Tank Protrusions for Uniform Cavitation
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Solution Overview
Problem
The CMP process leaves fine particles on wafers, which can cause damage in subsequent processes, and existing cleaning methods struggle to efficiently remove particles smaller than 3 μm due to the formation of a viscous boundary during cleaning.
Innovation Solution
A megasonic cleaner with a water tank design featuring transducers on the bottom and inner walls that generate waves to create cavitations within the viscous boundary, ensuring uniform cavitation distribution across the wafer surface, supported by strategically positioned rollers to rotate and stabilize the wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional cleaning methods are used, then the cleaning process is simple, but fine particles smaller than 3 μm cannot be effectively removed due to viscous boundary formation
Solution Approach 1:
The water tank is divided into multiple regions with different wall configurations. The front wall has a first region (facing the wafer) and a second region (side wall), while the rear wall has a third region and a fourth region. This segmentation allows different wall portions to serve different functions in wave reflection and cavitation generation, enabling effective particle removal while maintaining a relatively simple overall structure.
Solution Approach 2:
The invention introduces angular relationships between wall regions and wave propagation directions. The first region forms a first angle with the bottom wall, the second region forms a second angle, and these angles are designed to optimize wave reflection patterns. This angular/dimensional approach creates effective cavitation fields that penetrate the viscous boundary without requiring complex mechanical cleaning components.
2Manufacturing precision
If transducers are arranged to maximize cavitation, then cleaning effectiveness improves, but uniform cavitation distribution across the wafer surface becomes difficult to achieve
Solution Approach 1:
Different wall regions are assigned different geometric properties to create localized cavitation effects. The first region on the front wall and the third region on the rear wall are configured to reflect waves toward the wafer surface, while the second and fourth regions on the side walls provide additional reflection paths. This local differentiation of wall properties ensures uniform cavitation distribution across the entire wafer surface without requiring complex transducer positioning.
Solution Approach 2:
The water tank is designed with symmetric wall configurations where opposite walls have corresponding regions with matching angles and geometries. This symmetric/equipotential design ensures that wave reflection and cavitation generation are uniform across the wafer surface, creating consistent cleaning conditions throughout the treatment area without requiring complex asymmetric transducer arrangements.
3Ease of manufacture
If the water tank structure is simplified, then manufacturing cost decreases, but wave reflection and cavitation generation become insufficient
Solution Approach 1:
The wall regions serve multiple functions: they contain the cleaning fluid, reflect acoustic waves, and create cavitation fields. The angled configurations of the first, second, third, and fourth regions simultaneously perform structural support and acoustic wave management functions. This multi-functionality allows the water tank to achieve effective cleaning performance while maintaining a relatively simple, cost-effective structure without requiring additional complex components.
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 design enhances cleaning efficiency and reliability, ensuring that over 95% of the wafer surface experiences cavitations, thereby improving manufacturing yield by effectively removing fine particles and preventing defects in subsequent semiconductor processes.
Implementation Method 1
transducers arranged on the bottom wall and configured to transmit energy in the form of waves into the fluid, wherein each of the pair of opposite inner walls has a first protrusion that protrudes into an internal space of the water tank
Implementation Method 2
A megasonic cleaner with a water tank design featuring transducers on the bottom and inner walls that generate waves to create cavitations within the viscous boundary
Implementation Method 3
first protrusion that protrudes into an internal space of the water tank, and a shortest distance between the first protrusion and the bottom wall is greater than or equal to the distances between the plurality of supporting units and the bottom wall
Data Source
AI summary
A megasonic cleaner includes a water tank that includes a pair of opposite inner walls and a bottom wall connected thereto, and that accommodates a fluid therein; a plurality of supporting units arranged in the water tank at predetermined positions that support a wafer; and at least one transducer arranged on the bottom wall that transmits energy in the form of waves into the fluid, where each of the opposite inner walls has a first protrusion that protrudes into an internal space of the water tank, the first protrusion being spaced above the bottom wall and positioned at an height that is greater than or equal to a height of the centers of the plurality of supporting units.