Why does 2012 Sp-3 always include a full backup

I want to to do a log backup and a differential backup of my SQL dB's. Basically create 2 incremental backups and slecting the log and a second Incremental selecting Differential. Everytime I go to create a Tape Backup I get Full which cannot be deleted. I would prefer to seperate the backups but I am confounded by the inabilty to get rid of the Full backup.