CMUT TSV Substrate Plug Layout for Smaller Array Die Size
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Solution Overview
Problem
Conventional capacitive micromachined ultrasonic transducer (CMUT) devices face challenges with increased die size and complex packaging due to the need for bond pads and interconnect routing lines, which complicates the manufacturing process and increases costs.
Innovation Solution
The CMUT device employs a through-substrate via (TSV) for electrical connection, eliminating the need for bond pads by using a single electrically common movable membrane for each CMUT element, allowing independent addressing and reducing the number of mask levels required in the fabrication process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bond pads and interconnect routing lines are used to provide electrical contact to CMUT elements, then electrical connection is achieved, but die size increases and packaging complexity increases
Solution Approach 1:
The patent extracts and eliminates the bond pads and interconnect routing lines from the conventional CMUT structure. Instead of using separate bond pads placed remote from the CMUT elements, the invention integrates the electrical connection directly through the substrate via (TSV) technology, removing the unnecessary components that increase die size while maintaining reliable electrical connection.
Solution Approach 2:
The patent transitions from a planar connection approach (bond pads on the surface) to a three-dimensional approach by routing electrical connections through the substrate depth. The TSV technology creates vertical pathways through the substrate, allowing electrical contact to be established in the depth dimension rather than requiring additional surface area, thus reducing die size while maintaining connection reliability.
2Ease of manufacture
If bond pads are placed remote from CMUT elements to facilitate packaging, then packaging is enabled, but die size increases and manufacturing complexity increases
Solution Approach 1:
The patent removes the bond pads and complex interconnect routing from the device structure. By eliminating these components, the device becomes simpler to manufacture and package, as the TSV-based connection integrates the electrical pathway directly through the substrate without requiring separate bonding operations or complex routing patterns.
Solution Approach 2:
The patent merges the electrical connection function directly into the substrate structure through TSV technology. Instead of having separate bond pads and routing lines as distinct components, the electrical connection is integrated into the substrate itself, simplifying both the manufacturing process and the packaging procedure by reducing the number of discrete elements that must be handled.
3Reliability
If multiple bond pads are used for each CMUT element, then electrical contact is provided, but the number of mask levels and fabrication complexity increase
Solution Approach 1:
The patent extracts and eliminates the multiple bond pads and their associated interconnect routing from the conventional fabrication approach. By using TSV technology, the electrical contact is achieved through a single integrated pathway through the substrate, removing the need for multiple separate bonding operations and reducing the number of photolithography mask levels required.
Solution Approach 2:
The patent combines multiple electrical connection functions into a single TSV structure. Instead of requiring separate bond pads and routing lines for each CMUT element, the TSV integrates the electrical pathway directly through the substrate, reducing fabrication complexity by minimizing the number of patterning and bonding steps while maintaining reliable electrical contact.
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 results in a smaller CMUT array die size, simplified packaging, and reduced costs, while maintaining or improving ultrasonic output pressure and spatial resolution.
Implementation Method 1
a through-substrate via (TSV) formed in the first substrate and providing an electrical connection from a bottom side of the first substrate to a top plate of the CMUT element
Implementation Method 2
capacitive micromachined ultrasonic transducer (CMUT) device
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
A capacitive micromachined ultrasonic transducer (CMUT) device 100 includes at least one CMUT cell 100a including a first substrate 101 of a single crystal material having a top side including a patterned dielectric layer thereon including a thick 106 and a thin 107 dielectric region, and a through- substrate via (TSV) 111 extending a full thickness of the first substrate. The TSV is formed of the single crystal material, is electrically isolated by isolation regions 131 in the single crystal material, and is positioned under a top side contact area 102a of the first substrate. A membrane layer 120b is bonded to the thick dielectric region and over the thin dielectric region to provide a movable membrane over a microelectromechanical system (MEMS) cavity 114. A metal layer 161 is over the top side substrate contact area and over the movable membrane including coupling of the top side substrate contact area to the movable membrane.