Composite Transducer for Wafer Cleaning
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Solution Overview
Problem
Existing acoustic processing systems for semiconductor wafers face challenges in minimizing damage while effectively removing particles, particularly due to standing waves and heat dissipation issues, which can lead to transducer failure.
Innovation Solution
A composite transducer assembly with a convex outer surface and a concave inner surface, featuring piezoelectric pillars separated by resilient material, is used to create acoustically active and inactive areas, reducing standing waves and heat dissipation by orienting the inactive area closer to the wafer surface than the active areas, and incorporating an impedance matching layer for efficient energy transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If mechanical processes (scrubbers) are used to remove particles from wafer surfaces, then particle removal effectiveness is improved, but device damage increases
Solution Approach 1:
The patent replaces mechanical scrubbing processes with acoustic energy fields (ultrasonic/megasonic waves) to remove particles from wafer surfaces. The acoustic field creates cavitation and acoustic streaming effects in the liquid medium, which dislodge particles without direct mechanical contact, thereby maintaining high particle removal effectiveness while eliminating device damage caused by physical scrubbers.
Solution Approach 2:
The patent utilizes high-frequency acoustic vibrations (ultrasonic and megasonic ranges) to create cavitation bubbles and acoustic streaming in the liquid processing medium. These vibrations generate localized mechanical forces that detach particles from wafer surfaces without requiring direct contact with mechanical scrubbing elements, thus achieving effective particle removal while preventing device damage.
2Area of stationary object
If acoustic energy is applied to clean both wafer surfaces, then cleaning coverage is improved, but energy distribution uniformity deteriorates
Solution Approach 1:
The patent divides the acoustic processing system into separate top and bottom processing zones, each with its own transducer assembly optimized for treating one surface of the wafer. This segmentation allows independent optimization of acoustic parameters for each surface, ensuring uniform energy distribution on each side while achieving comprehensive coverage of both wafer surfaces through coordinated operation.
Solution Approach 2:
The patent transitions from single-sided to dual-sided processing by adding the dimensional aspect of treating both wafer surfaces simultaneously or sequentially. By positioning transducer assemblies on opposite sides of the wafer and using acoustic waves that propagate through the liquid medium, the system achieves uniform energy distribution across both surfaces, effectively addressing the two-dimensional cleaning coverage requirement.
3Use of energy by moving object
If transducer contacts wafer surface directly, then energy transmission efficiency is improved, but standing waves increase causing damage
Solution Approach 1:
The patent introduces a liquid coupling medium as an intermediary between the transducer and the wafer surface. The acoustic waves propagate through this liquid medium, which provides efficient energy transmission while preventing direct contact between the transducer and wafer. This intermediary layer eliminates standing wave formation that would occur with direct contact, thereby maintaining high energy transmission efficiency while preventing standing wave-induced damage.
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 configuration minimizes damage to semiconductor wafers by reducing standing waves and heat dissipation, enhancing the efficiency of particle removal and extending transducer lifespan by preventing overheating.
Implementation Method 1
The transducer is made of piezoelectric material, such as a ceramic or crystal. In operation, the transducer is coupled to a source of electrical energy. An electrical energy signal (i.e. electricity) is supplied to the transducer. The transducer converts this electrical energy signal into vibrational mechanical energy (i.e. acoustic energy)
Implementation Method 2
The transmission of the acoustic energy from the transducer to the substrates is typically accomplished by a fluid that acoustically couples the transducer to the substrate
Data Source
AI summary
An apparatus and method for processing articles utilizing acoustic energy. In one embodiment, the invention is an apparatus comprising a support; a conduit for applying a fluid to a surface of the article; and a transducer assembly comprising: a transmitting structure having a concave inner surface and a convex outer surface; a first acoustic transducer having a convex bottom surface bonded to the concave inner surface of the transmitting structure, wherein the first acoustic transducer is configured to create a first acoustically active area on the convex outer surface of the transmitting structure when the first acoustic transducer is energized; and a second acoustic transducer having a convex bottom surface bonded to the concave inner surface of the transmitting structure, wherein the second acoustic transducer is configured to create a second acoustically active area on the convex outer surface of the transmitting structure when the second acoustic transducer is energized.