MEMS Transducer Alignment via Integrated Diaphragms
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Solution Overview
Problem
The production of MEMS transducers for ultrasonic wave transmission/reception faces challenges such as high temperature damage to signal detection circuits, low yield due to separate circuit requirements, and high-cost, low-accuracy alignment of MEMS and electronic circuit substrates, especially in high-density connections.
Innovation Solution
A method involving the formation of multiple diaphragms on a substrate with a piezoelectric material layer and subsequent openings, using alignment diaphragms for precise alignment and bonding of MEMS and electronic circuit substrates, enabling accurate and cost-effective connection without dedicated high-accuracy equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high temperature annealing is performed to deposit piezoelectric thin film on MEMS substrate, then piezoelectric film quality is improved, but signal detection circuit is damaged
Solution Approach 1:
The production process is segmented into separate stages: MEMS substrate fabrication (including piezoelectric film deposition at high temperature) is performed independently from electronic circuit substrate fabrication. The two substrates are then bonded together through alignment marks, allowing the piezoelectric film to be deposited at high temperature without exposing the sensitive circuits to thermal damage.
Solution Approach 2:
Alignment marks serve as intermediaries that enable precise positioning and bonding between the MEMS substrate and electronic circuit substrate. These marks allow the two separately fabricated substrates to be accurately aligned and connected without requiring simultaneous high-temperature processing, thus protecting the circuits while achieving film quality.
2Object-affected harmful factors
If MEMS substrate and electronic circuit substrate are manufactured individually and then bonded together, then circuit damage from high temperature is avoided, but alignment accuracy is insufficient without dedicated equipment
Solution Approach 1:
The MEMS substrate itself provides the alignment function through its integrated alignment marks. The alignment marks are formed as part of the MEMS substrate fabrication process, eliminating the need for separate alignment equipment or additional alignment components. This self-aligning mechanism achieves high connection accuracy through simple overlay bonding.
3Manufacturing precision
If dedicated equipment for highly mechanically accurate alignment is used, then alignment accuracy is improved, but production cost increases greatly
Solution Approach 1:
The alignment marks are formed using standard photolithography and etching processes that are already part of the MEMS fabrication sequence. These marks can be created with simple geometric patterns that require no specialized equipment, replacing expensive dedicated alignment machinery with low-cost photolithographic features that achieve the same positioning function.
4Adaptability or versatility
If multiple MEMS substrates of different sizes and shapes are prepared for different ultrasound probes, then probe versatility is improved, but production complexity and cost increase
Solution Approach 1:
The alignment mark structure is designed with universal applicability across different MEMS substrate sizes and shapes. The same alignment mark formation process and bonding methodology can be applied to various probe types (linear, convex, sector, etc.), allowing a single production line to manufacture multiple probe configurations without requiring dedicated equipment or complex process variations for each substrate type.
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 method allows for high-accuracy and cost-effective connection of MEMS and electronic circuit substrates, reducing the risk of connection errors and enabling the use of a common electronic circuit for various ultrasound probes, thereby improving the yield and reducing production costs.
Implementation Method 1
The diaphragm has a unimorph structure in which a piezoelectric thin film (actuator layer) such as PTZ is formed on a substrate
Data Source
AI summary
Substrate is produced by using a MEMS technique to form multiple diaphragms in a substrate by forming piezoelectric material layer on one surface of the substrate and thereafter by forming openings in the substrate from the other surface of the substrate; substrate and substrate on which signal detection circuit is formed are aligned to each other using at least one of multiple diaphragms as alignment diaphragm; and substrate and substrate are bonded together.