I recently got a summer internship, and I need a secret clearance for this. Apparently it will be interim, for obvious reasons, but I was just wondering if the background check/investigation process was any different for interim clearances than permanent ones.
I've had both internships and full-time work in the defense industry. I've never heard of anyone only getting an interim clearance. They usually grant an interim after you submit the paperwork and they start the process and decide that the likelihood of problems coming up is low.
The interim clearance exists to let you start receiving your classified training, access the classified facilities, and begin work on the projects while the investigation and paperwork are concluding.
I suppose it's possible, though, but you should prepare for the exact same paperwork and process as anyone else getting your clearance level and consult the security office after you start to learn more. If you're accessing classified material, you will have an exit briefing at the end of your internship where they will explain how long your clearance is valid and what you may need to do should a future employer need to reinstate your clearance.