There is an example workspace in ADS. It is called 'Spiral Inductor on Silicon'. When you just open this workspace, there are graphs showing effective inductance value of the spiral inductor in .dds file.
When I implement the stack up file provided by the foundry and then run the EM simulation, I start seeing 'zero' effective inductance. That was the problem and I was searching for its reason.
Now, while writing this post, one of my colleague showed me that there seems no via between the conductors of inductor. I checked the substrate file and indeed the last two up metals are not connected with each other through any via. So I defined that via in the substrate file and checked from the 3D view of inductor that the last two conductors are connected and run the EM simulation again. Thank God, a reasonable inductance value is obtained with this configuration.
Thank you for your help..