Segmented Getter Openings for Uniform CMUT Cavity Pressure

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Solution Overview

Problem

Existing micromachined ultrasonic transducer devices face issues with variability in operating parameters due to differences in cavity pressures during manufacturing and bonding, leading to potential collapse voltage and transmit/receive pressure sensitivity, along with surface planarization difficulties that affect membrane bonding integrity.

Innovation Solution

The implementation of segmented getter openings and via structures that are offset from the transducer cavity footprint, combined with a bypass metal structure, to control cavity pressure and maintain electrical conductivity during manufacturing, using low-temperature bonding processes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If getter openings are formed in the bottom cavity layer to consume gaseous materials during bonding, then cavity pressure uniformity is improved, but electrical conductivity between vias and substrate may be compromised

Engineering Contradiction:

Improvecavity pressure uniformityVSAvoidelectrical conductivity

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The getter openings are segmented into multiple discrete openings distributed across the bottom cavity layer, rather than a single continuous opening. This segmentation allows selective exposure of getter material in specific regions while preserving electrical conductivity pathways in other regions, resolving the contradiction between pressure uniformity and electrical conductivity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the bottom cavity layer are treated differently: some regions have getter openings to consume gaseous materials and improve pressure uniformity, while other regions maintain continuous metal layers to ensure electrical conductivity. This local differentiation resolves the contradiction by applying different functions to different spatial locations.

Inventive Principle:

Principle #3Local quality

2Reliability

If vias are disposed directly beneath the transducer cavity footprint for electrical connection, then electrical conductivity is improved, but surface planarization becomes difficult affecting bonding integrity

Engineering Contradiction:

Improveelectrical conductivityVSAvoidsurface planarization

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The vias are extracted from their traditional position directly beneath the cavity footprint and relocated to peripheral regions. This extraction removes the source of surface planarization problems from the critical bonding area, while electrical conductivity is maintained through alternative pathways, resolving the contradiction between conductivity and planarization.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The via placement strategy transitions from a two-dimensional arrangement directly under the cavity to a three-dimensional configuration where vias are positioned in peripheral regions at different spatial locations. This dimensional repositioning allows electrical connection while avoiding interference with surface planarization in the bonding region.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Reliability

If low-temperature bonding processes are used to maintain via conductivity, then electrical conductivity is preserved, but bonding integrity may be compromised

Engineering Contradiction:

Improveelectrical conductivityVSAvoidbonding integrity

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The via structures are preliminarily configured with offset positioning and protective configurations before the bonding process. This preliminary arrangement ensures that the via regions are already optimized for conductivity preservation, allowing low-temperature bonding to be used without compromising either conductivity or bonding integrity.

Inventive Principle:

Principle #10Preliminary action

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 approach ensures uniform cavity pressure, improves bonding integrity, and maintains electrical conductivity, enhancing the manufacturing process margin and yield of micromachined ultrasonic transducers.

Implementation Method 1

the exposed regions of the bypass metal structure serve as a getter material to consume one or more gaseous materials present in the transducer cavity during bonding of the transducer membrane

Methodology Applied

Scientific EffectGettering: Gettering

Data Source

PatentUS12515240B2Segmented getter openings for micromachined ultrasound transducer devices

Publication Date: 2026.01.06 BFLY OPERATIONS INC

AI summary

An ultrasonic transducer device includes a bottom electrode layer of a transducer cavity disposed over a substrate, and a plurality of vias that electrically connect the bottom electrode layer with the substrate. A bottom cavity layer is disposed over the bottom electrode layer, and one or more openings are formed in the bottom cavity layer so as to expose a region of the bottom electrode layer, wherein locations of the one or more openings are segments that are disposed proximate an outer perimeter of the transducer cavity and substantially correspond to locations where the plurality of vias are not disposed directly beneath.