Pre-collapsed cMUT Cell Plug for High-Frequency Operation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing pre-collapsed capacitive micro-machined transducer cells, such as those disclosed in WO 2010/097729 A1, are not suitable for high-frequency applications due to the high collapse pressure required, which exceeds the strength of the retention member, making it difficult to maintain the membrane in a pre-collapsed state.
Innovation Solution
A pre-collapsed capacitive micro-machined transducer cell design featuring a membrane with a plug located in a subarea of the total membrane area, which is shaped to permanently fix the edge portion of the membrane to the substrate, providing sufficient strength to maintain the membrane in a collapsed state without relying on a retention layer that could be reversible.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a retention member is used to hold the membrane in a pre-collapsed state, then the membrane can be maintained in a collapsed configuration, but the retention member cannot withstand the high collapse pressure required for high-frequency cMUT cells
Solution Approach 1:
The patent removes the retention member entirely and replaces it with a plug structure integrated into the membrane itself. The plug is formed by depositing material through the hole in the membrane, creating an internal anchoring structure that eliminates the need for external retention members. This extraction of the retention member resolves the strength limitation while maintaining the pre-collapsed state through the plug's mechanical interlocking with the membrane and substrate.
Solution Approach 2:
The plug acts as an intermediary structure between the membrane and substrate, providing a mechanical connection that withstands high collapse pressures. Rather than relying on a separate retention member, the plug is formed within the membrane material itself, creating a unified structure that mediates the mechanical stresses between the membrane and substrate while maintaining the pre-collapsed configuration.
2Adaptability or versatility
If ambient air pressure is used to collapse the membrane, then low-frequency cMUT cells with large diameter membranes can be pre-collapsed, but the method fails for high-frequency cMUT cells with small membrane diameter requiring collapse pressure exceeding 5 Bar or 10 Bar
Solution Approach 1:
The plug is formed in advance during the manufacturing process, before the device is subjected to high collapse pressures during operation. By pre-forming the plug structure through material deposition and selective removal, the membrane is prepared to withstand the high pressures required for high-frequency operation. This preliminary structural preparation enables the membrane to be collapsed under high pressure without requiring a retention member.
Solution Approach 2:
The plug is localized to a specific region within the membrane (occupying less than 50% of the membrane area), providing localized reinforcement exactly where needed to anchor the collapsed membrane to the substrate. This local quality approach allows the membrane to maintain flexibility in most areas while having a specific reinforced zone that withstands the high collapse pressures required for high-frequency operation.
3Reliability
If a retention layer is used to maintain the collapsed state, then the membrane can be held in place, but the fixation is reversible and not sufficient for high-pressure applications
Solution Approach 1:
The patent eliminates the retention layer and replaces it with a plug structure that provides irreversible mechanical fixation. The plug is formed by depositing material through the hole in the membrane and then selectively removing portions of the deposited layer, creating a structure that is mechanically interlocked with both the membrane and substrate. This extraction of the retention layer provides permanent, non-reversible fixation capable of withstanding high collapse pressures.
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 allows for the creation of high-frequency pre-collapsed capacitive micro-machined transducer cells with improved bias voltage independence and increased design freedom, as the plug provides a permanent fixation mechanism that can withstand higher pressures, enabling effective operation at frequencies above 8 MHz.
Implementation Method 1
the plug is shaped to contact or to be fixed to the substrate, thereby permanently fixing the edge portion of the membrane to the substrate
Implementation Method 2
the variation in the capacitance between the electrodes can be detected. Thereby the ultrasound waves are transformed into a corresponding electrical signal
Implementation Method 3
an electrical signal applied to the electrodes causes the membrane to move or vibrate and thereby transmitting ultrasound waves
Data Source
Figure 1
Figure 2
Figure 3a~3d
AI summary
The present invention relates to a pre-collapsed capacitive micro-machined transducer cell (10) comprising a substrate (12), and a membrane (14) covering a total membrane area (Atotal), wherein a cavity (20) is formed between the membrane (14) and the substrate (12), the membrane (14) comprising a hole (15) and an edge portion (14a) surrounding the hole (15), the edge portion (14a) of the membrane (14) being collapsed to the substrate (12). The cell further comprises a plug (30) arranged in the hole (15) of the membrane (14), the plug (30) being located only in a subarea (Asub) of the total membrane area (Atotal). The present invention further relates to a method of manufacturing such pre- collapsed capacitive micro-machined transducer cell (10).