When you say "backup", I'm assuming you want to create a physical backup disk that you can play while placing the original in your archive. First you'll need a Blu-Ray reader/burner which you probably already have.
You need to install a copy of AnyDVD HD on your machine. Once that's done, a small fox symbol should appear in your system tray at the bottom of the screen. Load your original disc, and AnyDVD will do its thing for a few seconds and analyze the disc. When that finishes, RIGHT click on the fox symbol and choose "save to image". You'll need to have a location established on your hard drive, and sufficient space for the content (up to 50GB in some cases). When you right click on the fox symbol, a pop-up dialog box will allow you to indicate where you want the image to be saved. Click RUN. A progress screen appears.
When AnyDVD HD finishes, you should have an image of your original disc saved to your hard drive. Now you need to burn that image to a blank BD.
You can use one of SlySoft's products like CloneBD. Personally, I use ImgBurn which is a third party product. In any case, the software used needs an ability to burn an image to a disc (you can't burn that image file directly to a disc and expect it to play in a standalone player). You'll choose the image file that was created by AnyDVD HD.
Using that software and an appropriate sized blank (25 or DL 50 GB), you should get an exact copy of the original (including 3D BDs) when it finishes. CloneBD will allow you to shrink content to make it fit a 25GB blank whereas ImgBurn doesn't have that capability, although for uncompressed copies (which I personally prefer), I've had great success with the latter.