what is the best software to simulate slotlines

I have very thin slotline (10um width) can anyone advice me which software can be suitable for simulating such thin line

IE3D from Zeland has a feature that allows to simulate efficiently slot structures in infinite ground planes:

Magnetic current modeling of slot structures.
For slotted structures such as coplanar waveguides (CPWs), CPW antennas and slot-coupled patch antennas, IE3D can model the electric field distribution on the slots. It saves simulation time and memory.

Regards
Z