Changing "display order" of layers, and how they "step on each other"

I've got a big layer table with a bunch of "junk" layers from
the "incumbent" CAD tool. I've made a .lyp that suits me as
far as fill colors, frames, stipples.

What I can't find, is any GUI facility to "order" the layers such
that later layers "step on" earlier (in the process flow) layers,
but not vice versa, when displayed.

For example "TANK" (NPN collector) should be "underneath"
PBASE and it's OK if PBASE obscures part of the TANK rectangle.

But what I have, makes TANK blot out PBASE (if solid fill). Now,
PBASE has a higher GDS# (35/1) than TANK (99/1) and I am
stuck with the foundry's number assignments. If layer ordering
(visual stack) depends only on that, then I'm hosed. But does it?
What sets the "stack order" (NEMIT should be "above" PBASE,
PBASE "above" TANK, CONT above both NEMIT and PBASE,
MET above all.

Is there anything I can do by hand editing the .lyp to cause
the display-order to change as desired (like, is order defined
by "order of appearance" in the .lyp?

I've played with trying to make "transparent-ish stipple stacks"
but there's enough layers vertically that this ends up bending
the displayed color, as a "mash-up" (like, blue for P and red for N
ends up purple where they intersect). I'd rather allow an upper
implant to occult a lower one than try to make the lower layers
"shine through".


  • Hi Jim,

    Basically the order of the layers determines the drawing sequence. So upper layers get drawn first.
    But if you want the layers to be sorted by GDS layer/datatype, then you cannot determine the drawing order independently (at least as of now) :(

    I have some suggestions:

    1. Create two tabs - one with GDS numbering and one with drawing order. So you can switch between these versions quickly
    2. Use custom fill pattern (stipples) which are less dense and differentiate shape-wise. With a higher resolution screen this still gives a nice fill impression, but the mash-up effect will be much less pronounced.
    3. Use line styles and "crossed" style (for vias) for better visual differentiation beside stipples
    4. You can also use "transparent" mode - however this is only a RGB bitmap "OR" combination and the effect is there only if you overlay colors with different RGB bits set.


  • Thanks, Matthias,


    order of the layers determines the drawing sequence

    do you mean "order in which they appear in the .lyp",
    "order they appear in the layers window" (maybe the same?)
    or ???

    I see now how to make the tab, it's created a duplicate. But
    the "sorting" options, I don't think will help me because some
    layers are not really in bottom-up sequence (esp. the non-
    printing layers, like are Boolean'd into actual masks, but have
    to be drawn as if; like TANK is 99, well above all "real" layers,
    while ISO (= !TANK) is 17. But we draw TANK. And TANK steps
    on everything "real".

    So what's the drill, for asserting a "stack order" when neither
    name nor number are "orderly" as-taken-in?

  • You can use the four arrow buttons at the bottom of the layer view to "move" the selected layers to get the order you want.
    I thought I remembered to be able to do that with a mouse click and drag, but couldn't get that to work. I would have expected left-click + drag to move layers, but that's extending the selection.

  • That's a good tip, thanks.

    I did find that I could "copy" a layer window entry and
    "paste" it up top (creating two, same-named) and then
    deleting the old one from its original position. But that
    seems error-prone at best, and maybe unintended
    consequences left to discover. I like the arrow suggestion.

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