Re: Do I need to place spacer between the ESD pads?
It seems like the spacers are made up from some diodes
so if the people place spacers between the ESD pads, the area of diode will increase
If I just connect the ESD pads together with large metal layers(as the power supply on ESD pads form the power ring), there will be some gaps? I am still a little confused what do you refer to as GAP?
Honestly I do nor know what you mean by "spacers" but it might be that those are the ESD structures between VDD/GND. In general you have ESD protection on I/Os for each signal but to provide path under any conditions usually you have to put some additional structures between power rails. Those you can place anywhere (theoreticaly) and so it those spacers are mede from "some diodes" it might be they they serve this purpose.
Go through the ESD design rules for your process to make sure.