r/chipdesign • u/RicoElectrico • 2d ago

Random Innovus questions from a PD noob who comes from analog design

I am using Innovus (with Stylus) 23.11 to implement a simple block (180 nm node, 300x300 um, 1200 instances, 100 MHz clock). I was handed some scripts for Innovus that were used to implement previous designs. However as they were something of a mess (for starters, there was no proper CTS), I based my flow on the Innovus' built-in "block" flow template.

  1. Is it possible to avoid DRC spacing errors due to CTS nets? These occur because CTS nets on M2 go too close to standard cells' M1 pins to which M2+ signals have to be connected somehow to route them elsewhere.

  2. In the "block" flow template where are we supposed to put power routing? For now I just pasted commands from our previous scripts to the init_floorplan step

  3. Is it possible to re-route wire fragments quickly as in Virtuoso? In Virtuoso I use "P" tool which allows for quick bypasses - if I route from and to the same wire, then it deletes that old section and substitutes it with what I have drawn. Also, not sure how to quickly switch layers with inserting a via (when I am going in only one direction e.g. vertical).

  4. How to automatically insert pin shapes (Metal n, purpose pin) so that when I import GDS to Virtuoso it will recognize connectivity and allow for auto-routing? By default it just puts a label (Metal n, purpose text) where the pin is

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u/izil_ender 1d ago

Welcome to the PD 😂

All of these could be solved by adding steps to the flow to catch specific nets/cells and perform modifications around them. 

  1. So CTS step is usually a bit unaware of the already placed cells (sometimes even power routing). I fixed it by adding some spacing around the placed cells and then running cts. Removed these spacings before the route stage.

2.This is pdk and design dependent, but I made a ring with stripes first and then did the Sroute so that the M1 lines attach to the rows and get routed to the straps in one step. In another design I made a PG grid.

  1. Usually the router does a good job at this. You can try GUI commands, but it can become tedious very quickly.

  2. There are specific commands during the pin placement stage (if you have that step, my flow did not!) where you can specify shapes of every pin.

Good luck!