Online proceedings - EDA Publishing Association

7-9 October 2009, Leuven, Belgium
Fig. 1 SMU solver temperature results: a temperature contour slice
through the middle of the heat source is shown
while the heat transfer to the air is neglected and thus the rest
of the exterior walls were considered adiabatic. A 2.5W heat
source was placed in the center of the Silicon block. The
dimensions of the heat source are 10 x 5 x 50 µm. The
importance of the chosen geometry is that the solver has to
deal with over four orders of magnitude changes in scales.
The results of the steady-state simulation obtained using
the self-adaptive ultra-fast (SAUF) solver
are shown in Fig.
1 while the results obtained from the Fluent package are
shown in Fig. 2. The results are presented as temperature
contours on a vertical plane (YZ plane) that cuts through the
entire domain and passes through the middle of the heat
source. The temperature contours on the external surfaces of
the heat source are also shown in Figs. 1 and 2. Given a
prescribed accuracy level of 1%, the SAUF solver took 6
seconds to complete the solution whereas the ANSYS solver
took 370 seconds and an order of magnitude more memory
usage.
Fig. 2 ANSYS Fluent solver
temperature results: a temperature
contour slice through the middle of the heat source is shown
C. 3D Thermal Characterization: Combining the
Experimental and Numerical Results
The problem considered here is structurally and materially
complex, and is made of 12-finger MOSFETs with a channel
length of 100 µm and width of 1 µm. The widths of active
regions in state-of-the-art devices are significantly smaller
than those of the present device. The advantage in using this
device, however, is that the numerically simulated behavior
could be compared with measured data. But even more
interestingly, this device provides an opportunity to
demonstrate how input problem parameters can be adjusted
to more closely reflect the actual operation of a device.
The main features of the transistors can be seen in the top
view picture of Fig. 3. The main grey stem with 12 branches
running down the center of
the device is the poly-silicon
gate, while the brightest color is the Aluminum (Al) surface
Fig. 3 Top view of 12-finger MOSFET
(100×1 µm)
Fig. 4 Horizontal and vertical planes showing numerically-simulated
3D temperature fields, assuming total power is equally divided
among the
12 fingers
©EDA Publishing/THERMINIC 2009 37
ISBN: 978-2-35500-010-2