Physical Design is a process of transforming a circuit description into physical layout which describes the position of cells and routes for the interconnections between them. It is the result of a synthesized netlist that has been placed and routed. The design flow deals with various steps involved such as follows: Synthesized netlist ⇓ Partitioning ⇓ Sanity checks ⇓ Floorplan ⇓ Power plan ⇓ Placement ⇓ Clock Tree Structure (CTS) ⇓ Routing ⇓ Signoff Sanity checks has to be performed before every stage in order to check whether our design is meeting the requirements for the next stage (or) whether its properly designed. Basically, a code(program) is developed that explains us the RTL characteristics of the chip to be designed. That will be done by the front end engineers(RTL design team). The developed code is then compiled and as a result, a synthesized netlist is obtained. It contains the gate level model for the respective RTL code. .def is the output file at each s...
Temperature affects the performance of the
design both when its turned ON or OFF.
When the device is in OFF state, minority
charge carrier concentration (conc.) increases with the increase in
temperature. (*As we know, temperature affects the minority charge carrier
concentration but not majority charge carriers.)
The leakage current increases with the incr. in minority charge
carriers which inturn incr. the temp. and it goes on..
(*1οC↑ →
7% Iο↑)
Temp.↑ →
Minority carrier conc.↑ → Leakage current↑
→ Temp↑
It leads to Static Power Dissipation and at some
stage, the device may break.
When the device is in ON state, mobility(µ) and threshold voltage(Vt) will get affected by
temperature. Before going through this, we must recall the relation between µ and Id, Vt and Id.
At >65nm, Gate override voltage (Vdd - Vt) is large. So, the
changes in threshold voltage due to temperature is negligible and the effect on
mobility dominates on Id.
At <=65nm, (Vdd - Vt) is small because of
scaling of supply voltage(Vdd) due to low power
concerns. So, even the small change in threshold voltage due to temperature
variation effects the delay.
Effect
on mobility
When
temperature(T) incr, the charge carriers gets energized and their
movement speeds up. As a result, they collide with each other and the mobility
of the charge carriers gets decreased.
It
affects the Id(drain
current) such that the delay of the device increases.
T↑
→ µ↓ → Id↓
→ D↑
Effect on Threshold voltage
When
Temperature incr, the threshold voltage decreases. It inturn increases Id, resulting in the degradation of performance of the design.
T↑ → Vt↓
→ Id↑
→ D↓
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