CMUT Transducer Manufacturing via Localized Oxidation
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Solution Overview
Problem
Existing CMUT transducers face challenges in manufacturing processes that result in limitations such as geometric and mechanical characteristics affecting resonance frequency, leading to suboptimal performance.
Innovation Solution
A method for manufacturing CMUT transducers involves forming silicon oxide layers and localized oxidation to create cavities, followed by direct bonding to close the cavities, ensuring precise control over geometric characteristics and improving resonance frequency stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional manufacturing methods are used for CMUT transducers, then the manufacturing process is simpler, but the resonance frequency stability and geometric precision are insufficient
Solution Approach 1:
The method performs preliminary oxidation to form a first silicon oxide layer before defining the cavity, and uses localized oxidation to form walls with precise height control. This preliminary structuring enables precise cavity depth control in subsequent steps without requiring complex real-time adjustment mechanisms during the main manufacturing process.
Solution Approach 2:
The manufacturing process is divided into distinct sequential steps: forming a first silicon oxide layer, defining cavity locations, forming localized oxidation walls, forming a second silicon oxide layer, and closing cavities. This segmentation allows each step to be optimized independently for precision while maintaining overall process manageability.
2Reliability
If conventional manufacturing methods are used for CMUT transducers, then the manufacturing process is faster, but the resonance frequency characteristics are suboptimal
Solution Approach 1:
The method changes the oxidation parameters by performing localized oxidation only in specific regions where cavity walls are needed, rather than uniform oxidation across the entire substrate. This selective parameter application achieves precise geometric control over cavity depth and shape, directly improving resonance frequency stability without requiring excessive process time.
Solution Approach 2:
The patent replaces mechanical drilling or etching methods for cavity formation with a chemical oxidation process. The localized oxidation chemically transforms silicon into silicon oxide walls with controlled heights, providing superior geometric precision and resonance frequency control compared to mechanical approaches, while maintaining reasonable manufacturing throughput.
3Manufacturing precision
If precise control over cavity depth is implemented, then resonance frequency stability improves, but the manufacturing complexity increases
Solution Approach 1:
The manufacturing process uses periodic cycles of oxidation and deposition: first silicon oxide layer formation, localized oxidation for walls, then second silicon oxide layer formation to close cavities. This periodic repetition of controlled transformations achieves precise resonance frequency control through cumulative geometric refinement while keeping each individual step relatively simple and well-understood.
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 method enhances the manufacturing process by allowing for precise control over cavity depth and membrane characteristics, leading to improved resonance frequency stability and enhanced performance of CMUT transducers.
Implementation Method 1
in step a), the first layer of silicon oxide is formed by thermal oxidation in dry growth of said face of the first layer of silicon and, in step b), the second layer of silicon oxide is formed by thermal oxidation in dry growth of said face of the second layer of silicon
Implementation Method 2
forming, on the side of said face of the first layer of silicon, by localized oxidation of the silicon of the first layer of silicon, walls of silicon oxide having a height greater than the thickness of the first layer of silicon oxide
Implementation Method 3
in step d), the assembly comprising the second silicon layer and the second silicon oxide layer is fixed to the assembly comprising the first silicon layer, the first silicon oxide layer and the silicon oxide walls, so as to close the cavity of the transducer
Data Source
Figure 1A~1E
Figure 1F~1I
Figure 2A~2D
AI summary
This description relates to a method for manufacturing a CMUT transducer, comprising the following steps: a) forming a first layer of silicon oxide (103) on one face of a first silicon layer (101) defining a first electrode of the transducer; b) forming a second layer of silicon oxide (111) on one face of a second silicon layer (113); c) after step a), forming, on the side of said face of the first silicon layer (101), by localized oxidation of the silicon of the first silicon layer (101), silicon oxide walls (107); and d) after steps b) and c), transferring and fixing the assembly comprising the second silicon layer (113) and the second silicon oxide layer (111) onto the assembly comprising the first silicon layer (101), the first silicon oxide layer (103) and the silicon oxide walls (107).