Dead time in Half bridge gives weird output
"it's in floating state. So I should ideally get a zero output"


It's 'floating', so it will 'float' to a voltage determined by any parasitic elements in the circuit. MOSFET capacitance is one contributor, but other things could also have an effect (eg. Drain-Source leakage, bias supply V3).

Your oscilloscope probe presents a very high impedance - 10M&ohm; in parallel with ~10pF on x10 setting - so it acts as a very weak pull-down and currents in the nA range will have a plainly visible effect. The IRF540 has D-S leakage of up to 25uA at 100V. 

If both FETs are turned off long enough to equalize parasitic capacitances the output will float to a voltage determined by the relative D-S leakages in each FET (one pulling up, the other down).