Multiscale thermal simulation methodology for advanced MOSFETs at cryogenic temperatures

Details

Supervisors

Raskin, Jean-Pierre

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil électricien, à finalité spécialisée

Abstract

enThe field of cryogenic electronics is becoming increasingly important for applications such as quantum com puting where conventional CMOS circuits must operate at temperatures far below room temperature under strict thermal limitations. Under these conditions, the thermal behaviour of advanced MOSFETs changes significantly, making self-heating and thermal coupling important considerations for device and circuit design. This thesis develops a multiscale thermal simulation methodology for advanced MOSFET structures at cryogenic temperatures, using FD-SOI technology as a reference. The methodology starts with the technological parameters. The layout is processed and simplified in KLayout 0.30.7 to build a three-dimensional model in COMSOL Mul tiphysics 6.2 whose thermal behaviour can be simulated. The results of the simulations are then compared using device geometries derived from experimental structures. The influence of the simulated domain, material properties, boundary conditions, thermal excitation and geometrical simplifications is investigated. Simulations performed at room and cryogenic temperatures are compared with published experimental results to assess the capabilities and limitations of the proposed approach. The results highlight the strong dependence of thermal behaviour on temperature, geometry and modelling assumptions. The developed methodology provides a basis for further improvement toward more accurate and scalable electrothermal modelling of advanced cryogenic semiconductor devices. Finally, this work identifies numerous limitations and areas for improvement, providing a basis for the future development of more accurate and comprehensive thermal simulation methodologies for advanced cryogenic MOS FETs. These limitations include necessary technological and parametric simplifications to obtain computationally efficient simulations, size and memory limitations making certain geometries unable to be simulated, and the neglect of the interface thermal resistance which is especially important for cryogenic simulations. Furthermore, as the thermal-coupling phenomenon studied is heavily affected by technological and geometrical parameters of the devices simulated, more simulations should be done in the future using different technologies and geometries to be able to compare them to additional data from experimental measurements.