Fabrication and characterization of integrated micro-thermoelectric coolers using chemical and physical vapor deposition

• Applicants: Dr. Heiko Reith, since 12/2020; Professor Dr. Stephan Schulz
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: from 2019 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 423406119

Micro-thermoelectric coolers (µTECs) are intended to provide cooling locally at the electronic component where heat is produced or a punctual and precise control of the temperature is necessary. A promising potential application of µTECs is the local temperature control of optoelectronic components. Laser, especially for data transmission, require an extremely precise temperature control. If the laser cavity is exposed to temperature fluctuations, its geometrical dimensions vary due to thermal expansion, immediately reducing the efficiency of the data transmission. Today, typically the complete macroscopic assembly is actively cooled. An additional heater is placed close to the optoelectronic component for the required precise temperature stabilization. The total efficiency of the data transmission could be improved at reduced costs by the substitution of today’s technological solution by a temperature stabilization using integrated µTECs directly at the optoelectronic component. The state-of-the-art thermoelectric material in µTECs is produced by an electrochemical plating method since this is compatible with the requirements of a CMOS (complementary metal oxide semiconductor) back-end technology, but suffers from its poor thermoelectric conversion efficiency. However, the cooling power for the target-application can hereby not be realized due to the poor material’s quality, and thermoelectric material with a noticeably higher conversion efficiency would be requested. Therefore, there is a clear demand for technological solutions providing thermoelectric material with significantly increased conversion efficiency within a technology that is still fully compatible with CMOS back-end.The maximum allowed processing temperatures for the thermoelectric material is 200 °C, which is a challenge for the synthetic approach. While electrochemical plating methods are compatible with this temperature regime, the quality of the obtained material is not sufficient. There are two other deposition techniques that will be studied within this project: Chemical vapor deposition (CVD) and physical vapor deposition (PVD). For the CVD, the low substrate temperatures will be achieved by the use of thermolabile metalorganic precursors combined with special single-source-precursors that contain the building units of the material already at the molecular level. The same strategy will be applied for PVD, chosing processing temperatures such that a sufficient vapor pressure of the precursors is given.The principle feasibility of both approaches could be substantiated within preliminary work of the two applicants’ teams. But fundamental and systematic studies of the underlying mechanisms is now requested to allow for successful implementation of these two synthetic approaches into devices fabrication. This shall be realized by this project application.

• DFG Programme: Research Grants
• Ehemalige Antragstellerin: Professorin Dr. Gabi Schierning, until 11/2020