Thankyou dinesh, Can u plz tell me if a signal is to be sheilded, can v provide one side with VDD metal and other side with GND metal sheilding...? if yes why ?
More the shielding more de-coupled cap, and more total cap, more delay, and hence you lose sharper rising and falling edges.
If you use only GND line, and assuming which has finite parasitic resistance and not a separate SVSS line [as mentioned by steadymind] - you add ground bounce. If you use both VDD & GND at an equal distance from signal wire, you may have some advantage of balancing - the VDD-GND difference remains less affected. At the same time your signal is more vulnerable to glitches due to other switching logic [if they are on the same VDD/VSS rail], instead of one attacker you have two now.
Go ahead and check how the rising and falling edges looks in case you shield with VDD instead of VSS, of course I am assuming analysis is post-extraction [i.e. after parasitic extraction].
Check out - if you get any energy advantage [c*vdd^2/2] - in case you use one side with VDD & other with VSS?
If you can drive [have flexibility, Si routing space, design-time, to implement a SVSS feed from PAD methodology, what about using SVSS = VDD+VSS/2?
Analyze the scenario, when the dielectric is loss-less and when lossy.