Can your software handle inverting curved features?
Within AutoCAD the shape are likely to be defined with a curve primitive, such as a ‘polyline bulge’. AutoCAD may still draw these as a ‘rough’ approximation, even though the curves are well defined within its database.
When the AutoCAD is converted to GDSII, there is no curve primitive, everything has to be represented as polygons. The software which converts the DXF to GDSII will usually have some options to control how smooth any curves will be after the data has been converted.
If you are inputting the DXF to L-Edit then saving this as GDSII then you will need to look at your L-Edit configuration options available when inputting DXF data. If you are using a separate program, such as DXF2GDS produced by Artwork Conversion Software, then it is an option when this conversion is performed.
One thing to note is that: the smoother the curves, the larger the GDS data file, and this may result in the masks needing to be written on more advanced machines which can handle the large data volumes or longer mask write times. (None of our mask writing tools have a curve primitive in their data formats, so you need to represent the curve as a polygon for writing the mask anyway).
You need to decide how smooth the curves need to be to suit your process requirements.