The End of SWM and the Start of QTEM Mode
When SWM ends at f
e
, the next mode begins: Quasi-TEM mode (QTEM). In order to accurately quantify the transition of SWM to
QTEM mode, we need to utilize a 3D field-solver. For this simulation example, Ansys HFSS was utilized.
The main difference between the HFSS model and the Keysight ADS model is the inclusion of a redistribution layer (RDL) both above
and below the TSV S/G pair and a more complex stack-up of various materials.
SiO
2
E-Field "Capture and Release": Transitioning from SWM to QTEM with Ansys HFSS
Ansys HFSS allows viewing the magnitude of the E-field that is "captured" in the thin SiO
2
layer during the SWM of the TSV.
Looking at Figure 5, at 1 GHz there is a significant amount of E-field "captured" in the SiO
2
layer.
However, as the silicon relaxation frequency (f
e
)/~ 6 GHz is approached, the silicon transitions from a conductor to an effectively pure
dielectric, which allows the E-fields to penetrate into the silicon.
4
Figure 5. E-field magnitude at 1 GHz
Figure 6. E-field magnitude at 5 GHz
