Ultrasound: a new era of prosperity for CMUT and PMUT

Extracted from:
• Ultrasound Sensing Technologies 2020, Yole Développement, 2020
• Butterfly Network iQ CMUT Sensor, System Plus Consulting, 2020


  • Market figures and trends:
    The ultrasound sensing module market is expected to reach US$6.2 billion in 2025 with a 5.1% CAGR between 2019 and 2025.
    Ultrasound sensing market could be divided in different applications in which technologies and frequencies, as well as main drivers could highlight the technology of choice.
    ADAS applications are the bigger market segment expecting to reach US$4.3 billion. They use conventional bulk piezoelectric transducer technologies, while consumer and medical applications start to use CMUT and PMUT and grow two times faster offering new market opportunities.
  • Competitive landscape and supply chain:
    Players are mostly separated by technologies. A low number of them are either developing CMUT and PMUT knowledge.
    In the automotive sector, players like Continental are participating in projects to integrate MUT technologies for in-cabin gesture recognition.
    Today the MUT industry is structuring, with players such as Qualcomm and TDK Chirp offering off-the shelf solutions or platforms.
    Emerging ultrasound technologies not only compete with standard piezoelectric bulk technologies, but also with other types of detection such as 3D sensing and radar technologies.
  • COVID-19 pandemic:
    Although the COVID-19 pandemic has reduced the shipment of cars and smartphones, ultrasound imaging has been recognized as an early and safe detection technique for respiratory issues, accelerating the adoption of handheld point of care ultrasound devices.

“In 2019, the ultrasound sensing module industry was an impressive market of US$4.6 billion”, states Jérôme Mouly, Team Lead Analyst, Sensing & Actuating at Yole Développement (Yole). “In 2025, it is estimated at US$6.2 billion with a 5.1% CAGR between 2019 and 2025. This market is a mix of applications, ranging from those that have reached a certain threshold of maturity, to others that are emerging with growth opportunities”.
Ultrasound technologies have recently experienced renewed momentum linked to the development of microsystem technologies. After more than 30 years of development, CMUT and PMUT devices were finally integrated and recently marketed. But what is the status of this industry today? Have these new developments received wide adoption? What are the applications and opportunities of interest?

In this promising context, both partners, Yole and System Plus Consulting investigate disruptive ultrasound technologies and related markets. They point out the latest innovations and underline the business opportunities through an extensive collection of market and technology reports.
Released today, the Ultrasound Sensing Technologies 2020 report from Yole gives detailed analysis of the ultrasound industry. This report provides forecast metrics for each ultrasound sensing module and delivers an in-depth understanding of the ecosystem and players. Including market trends, revenues and forecasts, supply chain, technology roadmaps, take away and outlook, this study also shares key technical insights and analysis on future technology trends and challenges.
In parallel, the reverse engineering & costing company, System Plus Consulting releases the Butterfly Network iQ CMUT Sensor report, to analyze the CMUT chip. This study includes the complete teardown and cost analysis of the ultrasonic MEMS transducer and the ASIC die developed by Butterfly Network.
What are the economic and technological challenges of the ultrasound industry? What are the market drivers of the market? Who are the key suppliers and what technologies do they provide? How will evolve the PMUT and CMUT technologies? What are the impacts of COVID-19 on the ultrasound market?
Yole and System Plus Consulting are pleased to present today the state of the art of the ultrasound world.

As analyzed by Yole’s team in the new Ultrasound Sensing Technologies 2020 report, most of these new opportunities are due to developments in ultrasound micro technologies. Indeed, the miniaturization and technical specifications of MUT have made it possible to imagine applications where miniaturization and high integration are essential, or where volumes are large and component cost is key. Among these opportunities, the integration of ultrasound modules in VR headsets for gesture-recognition applications and fingerprint biometrics for smartphones and tablets in the consumer market, as well as point-of-care ultrasound in the medical sector, show strong growth with an expected CAGR of 81% for VR headsets integrating ultrasound sensing, between 2019 and 2025. For most of the fastest-growing applications over the period 2019 - 2025, the use of alternatives to bulk piezoelectric technologies has been one of the enablers. Also, these applications make it possible to create new opportunities, e.g. using touch sensing commands to replace physical buttons on smartphones and tablets, or even image-guided therapeutic devices (for example, catheters) for IVUS in the medical interventional sector requiring single use product. Here again, CMUT and PMUT have shown growing interest.

MUT technologies, whether capacitive or piezoelectric, have their own characteristics and are not always suitable for all applications. CMUT allow excellent image resolution, which makes them candidates for medical imaging applications. PMUT are more suited to detection which allows them to be integrated into applications such as biometric fingerprint and time-of-flight applications in the air like for gesture recognition.
According to Alexis Debray, PhD., Technology & Market Analyst, MEMS, Sensors & Photonics at Yole:
“Beyond the capacitive and piezoelectric operating principles, the choice of MUT and ASIC assembly can also be decisive for the final module size. The fabrication of cavities and membranes can use surface micromachining or wafer bonding technologies. The challenges of stiction when releasing the sacrificial layers sometimes leads to alternative wafer bonding using two SOI wafers, but with around 15% higher manufacturing costs”.
In fact, the latter choice was made by Butterfly Network for its point of care ultrasound probe.
Indeed, in the Butterfly Network iQ CMUT Sensor report, System Plus Consulting’s analysts affirm that Butterfly Network has developed a large CMUT die, intended to be integrated into a handheld medical ultrasound. Known as the iQ probe, it is based on semiconductor technology and is manufactured by a semiconductor supply chain. This solution reduces manufacturing cost and produces very small CMUT elements.
According to Sylvain Hallereau, Senior Cost Engineer at System Plus Consulting:
“The secret of the first semiconductor CMUT is not only in the MEMS die but also in the integration with the ASIC die. The ASIC die has all the functions to drive pulse generation, measure the echo, run Butterfly Network’s algorithms and communicate with the processor on the PCB”.
Each CMUT is driven by a block with CMOS logic, analog reading circuit and LDMOS transistors for the emission. The ASIC die and the CMUT die are bonded together at wafer-level and a part of the process is common for the two wafers after the bonding for TSV connection.
On the other hand, the choice of materials and techniques for depositing the piezoelectric layers of PMUT devices will force manufacturers to adapt their clean rooms. Indeed, while AlN is a material compatible with cleanroom environments, PZT is much more difficult to use, often requiring the use of foundries that have adapted this manufacturing process.
Lastly, miniaturization of the components is often linked with an optimization of the architecture: transducer close to the ASIC. The integration challenges are numerous; monolithic approaches are very advantageous in terms of final footprint, whereas MUT-on-CMOS approaches are a compromise that is much more convenient to manufacture. And what about the emerging technologies requiring flexibility and stretching for non-planar and conformable applications? All the technological choices and their challenges are included in this report, along with roadmaps and comparison tables.

All year long, Yole Développement and System Plus Consulting publish numerous reports related to sensing & actuating technologies and markets. In addition, experts realize various key presentations and organize key conferences. Make sure to be aware of the latest news coming from the industry and get an overview of our activities, including interviews with leading companies and more on i-Micronews. Stay tuned!

CAGR: Compound Annual Growth Rate
MUT : Micromachined Ultrasound Transducers
PMUT : Piezoelectric Micromachined Ultrasonic Transducers
CMUT : Capacitive Micromachined Ultrasonic Transducers
VR: Virtual Reality
IVUS : Intravascular Ultrasound
PCB : Printed Circuit Board
TSV: Through Silicon Via
AIN : Aluminum Nitride
PZT: Lead Zirconate Titanate
ASIC: Application Specific Integrated Circuit