Impact of isolation scheme on thermal resistance and collector-substrate capacitance of SiGe HBTs

5. Reliability

“…Thermal issues have become a serious concern in SiGe HBTs due to the concurrent impact of the following factors: (i) the shrinking of the intrinsic device has induced a growth in power density within the base-collector SCR for a given bias condition; (ii) the trench isolation -exploited to reduce parasitics, crosstalk, and increase f MAX -limits the heat spreading since trenches are filled with materials suffering from low thermal conductivity [Rie05,dAl10,You11,Pet15]. This mechanism is even exacerbated by lateral scaling, which results in a horizontal reduction of the Si volume embraced by trenches; (iii) HBTs are operated at high current densities to boost the frequency performance, which entails a further increase in dissipated power density [Cre13].…”

Advanced thermal simulation of SiGe:C HBTs including back-end-of-line

“…Unfortunately, thermal issues have become a serious concern in SiGe HBTs due to the concurrent impact of the following factors: (i) the intrinsic device shrinking has induced a growth in power density within the base-collector depletion region; (ii) the trench isolationexploited to reduce parasitics and increase f maxgives rise to a limited heat spreading since trenches are filled with low conductivity materials [6][7][8][9]. This mechanism is even exacerbated by the lateral scaling, which results in a horizontal reduction of the Si volume embraced by trenches; (iii) HBTs are operated at high current densities to boost the frequency performance, which entails a further increase in dissipated power density [2].…”