Stats

  • Locked Locked
  • Replies 11
  • Subscribers 144
  • Views 18189
  • Members are here 0
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

What is the best way to stream out a cellview that contains pcell instance

richardyuan

When I stream out the cellview that contains pcell install, i usually set the options with "Convert Pcells to Geometry" and "Convert Paths to Polygons" checked.

But after streaming out and streaming in,  the shapes didn't keep the related positions to the others as in the orginial cellview. 

I tried another way:

1. Flatten the pcell instance in the cellview first.

2. Merge the shape in same layer (will break the shape into pieces).

3. Stream out and stream in.

Now the shapes stand their positions well, though broken into pieces.

I don't like to flat the pcell instance, as it is convenient to save parameters in the cellview. 

Is there a better way to stream out? 

  • richardyuan
    Stream out with "Convert Pcells to Geometry" checked, shapes lost positions when stream in.
  • richardyuan

    pcell instance flattened and merged, shapes broken into pieces:

     

  • tweeks

    Could you make the differences between the images a bit more obvious?  They look almost the same to me.  I can see a tiny difference with the overlap of the rectangle at the top of the curvy piece, but I'm not sure it is a real difference--the merged result looks like it would be the same.

     

    By the way, this layout looks cool. :)  It's rare to see such a fluid, curvy shape.

  • richardyuan

    Yeah, the layout is based on a MEMS project. You know MEMS demands all kinds of strange shapes.

    The additional part I draw a green box is to avoid a sharp connection of two curves. You can see the effect from my third post.

    But if I don't break the shapes, the additional part seems move up a little and left a sharp connection after stream-out/stream-in.

    The part moves somehow 0.5um or so.

     

  • tweeks

    Thanks, that helps a lot!

    So the curvey thing is the pcell?

    It would help to know what version of pipo/Xstream you are running. 

    I've seen stream out move contacts around on fluid guard rings (or maybe they were MPPs, can't remember), so this sort of thing does happen now and then.  Usually the solution is to use a newer version of stream out.   Your version looks pretty old....

     

  • tweeks

    There are lots of explanations for what's going on.  Maybe the wrong pcell code is getting loaded by stream out (or stream in).  Maybe stream out/in is just buggy.  Maybe if you flattened the pcell before streaming out, or converted it to a regular instance before streaming out, it would work better.

    Sorry I don't have good ideas--Andrew would probably have better suggestions, though really you should raise this with your local AE.

  • richardyuan

    Hi tweeks,

    I think i got some clues.

    The outer ring becomes polygon with fewer edges after stream-out/stream-in, changing its distance to the marked shape at the connection.. 

    The outer ring is created by dbCreateDonut. I change the conic sides from 20 to 300 at "Layout Editor", then convert the ring to polygon. When stream-out/stream-in, the marked place looks normal now.

     Now I have another question, does the "conic sides" has any relationship with the layout grid? What is the recommended "conic sides" if the grid resolution is set to 0.01?

  • Andrew Beckett

    richardyuan said:
     Now I have another question, does the "conic sides" has any relationship with the layout grid? What is the recommended "conic sides" if the grid resolution is set to 0.01?

     

    I don't think that's an answerable question, since the number of conic sides that is appropriate will depend upon the size of the shape that is being converted to a polygon. If you want to avoid ambiguity, you could always do a dbConvertDonutToPolygon in the pcell code itself, and then what you see in the layout should be what you get in the stream file.

    Regards,

    Andrew.

Community Guidelines

The Cadence Design Communities support Cadence users and technologists interacting to exchange ideas, news, technical information, and best practices to solve problems and get the most from Cadence technology. The community is open to everyone, and to provide the most value, we require participants to follow our Community Guidelines that facilitate a quality exchange of ideas and information. By accessing, contributing, using or downloading any materials from the site, you agree to be bound by the full Community Guidelines.