Do you mean you want to backup your CMOS settings?
Backing up a BIOS is not the sort of thing most want to do and is usually only possible if your motherboard manufacturer offers it as part of its BIOS flash utility (flashing a BIOS is not recommended unless absolutely necessary).
If you are referring to backing up your CMOS values then the good old pen and paper seems to be the preferred option although there are a number of routines that purport to do it. Suggest you search the web for "CMOS backup". Cant help with any of these routines as I havnt used them, sorry.