Reduced operating temperature of active layer Si covered by nanocrystalline diamond film

This paper reports the heat dissipation ability of nanocrystalline diamond (NCD) film used as an insulator in interconnection layers. The thermal resistance is used as an evidence for evaluating particular ability. There are two points to measure, that is to say, the temperature in the active Si region and that of the nearest point at the top of the insulating film. We used a thin film Si resistor covered with NCD or silicon dioxide (SiO₂) on a silicon on insulator substrate. The NCD film was deposited by microwave-plasma chemical vapor deposition at 400 °C, while the SiO₂ film was deposited by plasma-enhanced chemical vapor deposition at 350 °C. The thickness of the NCD film was 600 nm, while that of the SiO₂ film was 300 and 500 nm. The aluminium (Al) was deposited by sputtering and patterned on the top of the insulating-film. Heat was applied to the resistor by directly applying electricity to the resistor. The temperature of the Si resistor and Al was determined from the resistance change. It was found that the thermal resistance of NCD film was approximately 14 % less than that of SiO₂ film, leading to the reduction of the thin-film Si temperature by 20 °C, even though it was thicker than 100 nm.