I use the 'y' layers as helpers within layout such as marking a flip point on a symmetrical cell.
Typically I'll make a path and set the width to .001; at least I used to do this until 6.1.5
Now, there is a new feature that will not allow a smaller than double manufacturing grid path so when I set the width to .001, I get this and then the width is reset to .005.
*WARNING* (LE-103007): Width of 0.005 should be an even multiple of mfgGrid (0.005) units 0. new width of 0.005has been adjusted to even multiple of mfgGrid (0.005) units 0.*WARNING* (LE-103836): The value for width should be greater than zero, setting it back to previousvalue.
I'm not sure why this is so important on a non-process layer and I'm wondering, before I file a "lost functionality" SR, if there is a variable that I can set to regain the old behavior.
There's not (as far as I can tell) a way to turn this off, other than reducing the manufacturing grid (which you can do in the tech file, and could do in an incremental tech file if you prefer not to edit the master tech file). The path width has to remain an even multiple of the DBU unit though, so if you have DBUPerUU set to 1000.0, the minimum would be 0.002 (if it's 2000.0 you can have 0.001u) - this part is an OpenAccess restriction (actually it was the same in IC5141 I believe; it's the mfgGrid check that is new in IC61X).
The tool doesn't really know whether something is a non-process layer or not (you could stream it out to a real mask layer if you chose).