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Sanity checks before floorplan in Physical design Sanity checks are an important step for physical design engineers to make sure that the inputs received for physical design are correct and consistent. Any issues in the input may cause problems in the later stages. So it is important to perform the sanity checks in the initial stage that is when the design is loaded in PnR tool and before the start of the floorplan. Here is a list of checks which must be performed before floorplan of design. Figure-1: Sanity checks before floorplan Library Check: In library check, basically, we validate the libraries before starting the physical design by checking the consistency between the physical and logical library.  It also checks the quality of both libraries and reports the error if any. The cells used in the design must be present in the logical as well as in the physical library. Innovus commands: check_design -physicalLibrary :  This command will check the physical library and report that al

🇼‌🇭‌🇾‌ 🇫‌🇱‌🇴‌🇦‌🇹‌ 🇴‌🇺‌🇹‌🇵‌🇺‌🇹‌ 🇦‌🇷‌🇪‌ 🇮‌🇬‌🇳‌🇴‌🇷‌🇪‌🇩‌ 🇧‌🇺‌🇹‌ 🇳‌🇴‌🇹‌ 🇫‌🇱‌🇴‌🇦‌🇹‌ 🇬‌🇦‌🇹‌🇪‌ 🇮‌🇳‌🇵‌🇺‌🇹‌🇸‌ Float gate inputs may pickup any value. So 1.Both the transistors may form the conduction path and short circuit VDD&VSS. Power dissipation increases. 2.ESD signals directly enter the gate and destroy the gate oxide. 3.Inputs may pick up  the unnecessary signals from the by side nets and destroy the functionality of the down the stage circuits. 4.To avoid these problems we connect the spare gate inputs either to 1/0. Floating output's Connected to the drain & source and is not a problem to the device structure.

  Why order of filling is form more width filler cells to low width filler cells?       It forms the wide metal due to continuous placement of low width filler cells. Creates Metal slotting rule violation. The CMP damascene process also introduces undesirable side effects, including dielectric  erosion and metal dishing.     Please always insert fat fillers first and then thin fillers afterwards. To avoid the metal-slot-rule      violation, please do not only use thin filler cells to fill large I/O spacing. For example, use one 20um pitch filler cell (PFILLER20) and one 10um pitch filler cell (PFILLER10) instead of using 6 “5um pitch” filler cells (PFILLER5) to fill 30um spacing. In addition, if spacing is larger than one cell pitch, please first insert core power cell  and I/O power cell. Then insert filler cells to fill up the rest of spacing for ESD robustness. 

Why the resistivity of the top metal layers will be low compared to the lower metal layers eve though you use the same metal for all the layers? Theoretically, one would want to have all metal layers with low resistance. Practically, there are limitations - cost and technology - that lead to finite metal resistance .All metal layers can be made of copper, and copper has much lower resistance than aluminum (~1.7e-6 Ohm*cm vs ~2.7e-6 Ohm*cm). However copper technology is more expensive than aluminum technology, so there is a cost-performance trade-off.  From technology viewpoint, you can make a metal layer very thick (to make sheet rho value lower), but then you can not make metal line very narrow (lateral coupling capacitance increases and results the cross talk) .So if you want to achieve very fine metal pitch (to provide high integration density - i.e. number of devices per unit area), the metal thickness can not be made very large. The solution is to use thinner (and thus more resist

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