ASIC Flow Diagram

Special cells and their Importance

Types of cells: Well taps (Tap Cells): This is non-logic cells. Tap cells are needed to reduce substrate and well resistance to prevent latch up. These cells generally used when the all the standard or most of the cells does not have well or substrate. - It is inserted at specific interval in the design and distance is defined as per foundry rule for specific technology. -We can insert at every row, every other row or stagger patterns also. - Most preferable way to insert the well tap is to stagger way because of reduce the total number of cells insertion in the design and reduce the total area utilization by those tap cells. End cap Cells: -This are the preplaced physical only cells. -Insert to meet certain design rules -Insert at the end of the site row, top and bottom side of the block boundary and every macro boundary. - This will also helps to reduce the drc's nearer to macros as the standard cells do not placed near to the macros. -This cells only

PD Interview Questions with Answers

PD Interview Questions with Answers: 1) How can you reduce dynamic power? – Reduce switching activity by designing good RTL - Clock gating -Architectural improvements -Reduce supply voltage -Use multiple voltage domains-Multi vdd 2) What are the vectors of dynamic power? Voltage and Current 3) How will you do power planning? 4) If you have both IR drop and congestion how will you fix it? -Spread macros -Spread standard cells -Increase strap width -Increase number of straps -Use proper blockage 5) Is increasing power line width and providing more number of straps are the only solution to IR drop? -Spread macros -Spread standard cells -Use proper blockage 6) In a reg to reg path if you have setup problem where will you insert buffer-near to launching flop or capture flop? Why? (buffers are inserted for fixing fanout voilations and hence they reduce setup voilation; otherwise we try to fix setup voilation with the sizing of cells; now just assume that you must inser

Metal Filling Styles

Metal Filling: Whether performed by the designer or by the foundry, metal fill is a mandatory step at advanced nodes to ensure manufacturability and high yield. It involves filling the empty or white spaces near the design with metal polygons to ensure regular planarization of the wafer. Foundry-mandated fill requirements stipulate that the fill density be within specified maximum and minimum parameters. While regular planarization is crucial to prevent over or under polishing of signal routes and active circuitry, metal fill can also negatively affect timing due to increased capacitive coupling to the nearby nets. Thus, the designer must ensure that the metal fill is done without impacting timing-critical nets. In other words, the fill needs to be timing-aware. Timing-awareness is also needed when the engineering change order (ECO) arrives late in the design cycle. The ECOs require the designer to change the layout and fill around the affected area. Thus, the fill method

Asic- Physical Design

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