HITACT - High-Detectivity Infrared Thermopile Arrays Featuring CMOS Integration of Telluride Materials

Thermoelectric infrared (IR) sensor arrays are a key enabling technology for non-contact temperature measurement and high-precision thermal imaging. Whether used for temperature monitoring in industrial production, contactless vital sign measurement in medical applications, or person detection in security systems, high-performance IR sensing is in growing demand.

However, state-of-the-art thermopile arrays are reaching their performance limits, as commonly used materials (such as doped polysilicon) significantly restrict thermal resolution. This is where the Saxon collaborative project HITACT (High-Detectivity Infrared Thermopile Arrays with CMOS Integration of Tellurides) comes in.

What is the goal of the HITACT project?

The aim of the project is to establish the technological foundation for a completely new generation of IR sensor arrays. For this purpose, highly efficient thermoelectric material classes such as bismuth telluride and antimony telluride are being integrated directly into a system-on-chip (CMOS) process for the first time.

The targeted performance specifications of the new sensors set new benchmarks:

• Highest temperature resolution (NETD): < 20 mK
• Minimised pixel size: < 45 µm

The Innovative Approach: Monolithic BEoL Integration

Integrating telluride materials into conventional CMOS manufacturing has long been considered impractical due to strict cleanroom contamination requirements. The HITACT project overcomes this challenge with a novel MEMS device concept: the sensor pixels are positioned on vacuum cavities that are monolithically integrated into the CMOS wafer's Backend-of-the-Line (BEoL) layer stack. As a result, the processing of the new thermoelectric materials takes place only after completion of the main CMOS fabrication process. At the same time, the vacuum cavities provide excellent thermal insulation, resulting in high thermal resistance and enabling the sensor's outstanding temperature resolution.

Application Areas

The projected performance improvements open up entirely new market opportunities and application fields:

• Industry: High-precision temperature monitoring and enhanced process control in manufacturing environments.
• Medical Technology: Contactless vital sign monitoring and support for the early detection of inflammation and cancer.
• Ambient Assisted Living (AAL): Reliable, privacy-preserving fall detection for assisted living and elderly care.
• Security & Mobility: Advanced human detection (e.g. at airports) and deployment in autonomous vehicles and unmanned systems (UxVs).
• Environmental Monitoring: High-precision thermal sensing for environmental data acquisition and climate-related monitoring applications.

The project is funded through the ERDF/JTF technology funding programme of the Free State of Saxony and brings together the complementary expertise of three leading partners based in Dresden:

• Fraunhofer IPMS – MEMS Technology & Semiconductor Integration: As the project lead for MEMS technology, Fraunhofer IPMS is responsible for the complete MEMS process development and the advanced Backend-of-the-Line (BEoL) integration on CMOS wafers. A key focus is cleanroom defect and contamination management to ensure the reliable integration of the novel telluride material classes. This work establishes the technological foundation for the subsequent transfer of the process to the institute's industrial 200 mm ADMONT KET pilot line.
• Heimann Sensor GmbH: A global leader in thermopile array technology, Heimann Sensor is responsible for device concept development, simulation, sensor design, and the characterization of the demonstrators.
• Leibniz Institute for Solid State and Materials Research Dresden (IFW Dresden): An internationally recognized research institute specializing in micro-thermoelectric modules, IFW Dresden is responsible for material synthesis, PVD thin-film optimization, and process development.