Measurement of buried oxide thermal conductivity for accurate electrothermal simulation of SOI devices

Finite element simulations demonstrate that the thermal conductivity of the buried oxide is an important parameter for the modeling of the thermal beh avior of silicon-on-insulator (SOI) devices. There is much uncertainty abou t the conductivity of different forms of SiO2, particularly that of buried oxides. This paper presents a novel approach to measure this conductivity, using structures that are compatible with standard bipolar or CMOS processe s. Thermal conductivity values of 0.66 and 0.82 W/mK, respectively, were fo und for 300-nm BESOI and 420-nm SIMOX oxides at room temperature. The measu red variations of thermal conductivity with temperature agree well with bul k SiO2 behavior. Better agreement between measurement and finite element si mulation of MOSFET thermal resistance is obtained by using these extracted thermal conductivity values. It is also shown that the role of the silicon substrate in determining the thermal resistance of the device can be calcul ated using a simple analytical model. This Is important when one wishes to calculate accurately individual thermal resistances of transistors in a giv en circuit.