Device marking ID/Serial number on the inner layer of ICs?

Hi there,

Is it true that manufacturers imprint device markings (i.e. Manufacturer's P/N/ID) on some inner layer(s) inside the device in addition to the marking on the outer surface packaging of ICs?  If so, how deep/difficult is it to reveal via basic grinding/etching processes?

On some of our products' PCB assemblies, we have been applying an IC obfuscation (i.e. laser etching) process on all ICs in addition to potting (i.e. conformal coating) for intellectual property purposes.  

The main objective of this process is to eliminate all device markings visible on the top surface of all ICs that would serve as defense against 'low-level copycats' from duplicating our design (i.e. what type/brand of IC used in the circuit,etc.) and then make it harder for them by conformal coating the whole PCB assembly.

I am aware that every product could be reverse-engineered on some level.  However, If we could keep these 'low-level copycats' at bay, then we can focus on having a case against the 'big-time' ones.

Therefore, we need to investigate if both the etching and coating process is effective in ensuring that there is a high level of difficulty and/or cost involved for the  'low-level copycats' to duplicate our designs.   

If there are device markings hidden inside ICs, then 'digging deeper' would reveal the devices' identity - the only question is how deep/difficult it is.

If anybody can confirm/has done experimentations with regard to this issue, kindly share your results/suggestions.

Thanks and Regards,

-Felix-