Hi @Mitch Bailey, I am trying to implement the layout of a SAR logic block as show in the figures attached. When I run DRC, I am having a grid offset error from the nmos transistors (XM1 and XM4). This occurs for nmos p-cell with L< 1.1um with and without the guardring. In the schematic, I am using W = 1.56um for the nmos. For an nmos cell with L=1.1um the original cell dimensions are w = 4.38um and h= 4.25um and w = 2.66um and 2.53um with guardring and without guarding, respectively. However, for an nmos cell with w= 1.56um and L = 1um, the original cell dimensions are w = 4.28um and h= 4.252um and w = 2.56um and 2.531um with and without guarding, respectively. It is clear that the h dimension of the original cell is off grid, which is generating the DRC error. To correct this error, I can extend the layers that are off-grid but I would like to ask you if you have any other advice. Thanks

Hi @Juan Sebastian Moya sounds like a magic device generator error so I’ll defer to @Tim Edwards.

Thanks Mitch!

I don't think this was done with magic's device generators. Some of the shapes are drawn with polygons (or possibly paths), which magic doesn't do (without some effort and pretty extensive knowledge of magic's more obscure commands). Also, magic has a database which makes it unable to generate off-grid elements. So I think these devices were created with klayout.

These devices were generated using Klayout. The off-grid error specifically affects MOSFETs with gate lengths equal to or less than 1u. It appears to be a glitch in the

fet.py

or

draw_fet.py

file. The reason I didn't catch this earlier because most of the transistors we've been using are 2u by 2u. I'm unsure who's responsible for the pymacros for gf180mcu on Klayout, but there's a small error in them. As @Juan Sebastian Moya pointed out, we can resolve it by simply adding a new layer of the same type on top of the one with the off-grid error.

Ok, let’s tag @Amro Tork then. Did mabrains create the device generators for gf180? (Sorry ’bout that Tim. Good luck with the workshop. 3am is a bit late/early for me - looking forward to the video.)