Many people have been discusing name check and fingerprinting. My understanding as follow:
Background check includes name check and fingerprinting check, usually fingerprinting will be very fast, in very rare case you will be found match the criminal database unless you were caught for some reasons and your fingerprint in the database of FBI, otherwise your fingerprint will be completed within days.
The reason why your case is delayed is due to name check which take long time for FBI, because this depends on many factors which hard to identify within short time especially for those people whose name and information got match in the FBI database.
Anyway, you have to pass both fingerprinting and name check, and then USCIS will consider your security check has been cleared, after that your case will be proceeded and case will be approved.