Transient Thermal Behavior of Third-Generation SiGe HBTs with Shallow Trench Isolation

With the aid of the thermal-electrical model of the 0.12μm SiGe heterojunction bipolar transistor (HBT) with shallow trench isolation (STI), the transient thermal behavior of the device is studied. Both thermal time constant (τ) and thermal capacitance (C
_TH
) are adopted to represent the transient thermal behavior. Furthermore, the influence of pulse power, thickness and depth of shallow trench isolation on τ and C
_TH
are studied. It is shown that both τ and C
_TH
are increased with the increase of pulse power. With the increase of shallow trench thickness (t
_s
), τ is almost increased linearly, which leads to the prolongation of time to reach thermal steady-state for STI device. At the same time, with the increase of shallow trench depth (d
_s
), C
_TH
is decreased obviously, which leads to the weakness of ability to store heat of HBT with STI. In addition, τ is increased slightly with the increase of d
_s
and C
_TH
is insensitive to variation of t
_s
. The results above shed light on the improvement of the transient thermal behavior of shallow trench-isolated SiGe HBTs.