To isolate different substrates we use psub2 layer.
But it is only a marking layer and it is used only for LVS.
How does this layer impact the Mask preparation and separate the substrates in teh actual device?
yes ,it is a virtual layer only exsited in EDA tools to satify aome rules and for the purpose of convinience,used for LVS,etc.In maufacturing , it does't exist,so you can't use it for any real application.
psub2 layer is used if there is no Deep N-well to isolate digital blocks from analog blocks.
it is just used to isolate the grounds (analog and digital ground).
these grounds are virtually isolated but they have physical connection through psub.
though they are not actually created during masking, they are very important in LVS verification.