My back door is top half glass and I need a way to make it more secure

there are decorative bars you can put on the glass part if the back door, if you are concerned about someone breaking it and getting in. Otherwise, you can opt for a solid wood or metal door.

My mom's house had a side door like that too. My mom was tiny, 5'1" so on the wood portion of the door he installed a heavy duty deadbolt with a key entry. He did reframe the door to beef it up to make it more secure.

If your door can be opened when you aren't at home, you really need to have the door reframed with a deadbolt key entry lock as Naomie said, or get a solid wood or metal door as Diana said. Security is important. If your existing door can be reframed & a deadbolt added, you can order decorative, easy to install interior metal security bars from Ace Hardware. We have used them on several doors and windows. You can use hooks and hang pots of herbs on the bars. For added security, we replace our glass storm door with a metal "Security Screen Door" from Lowes. They come in different colors and are very attractive. We had a keyed deadbolt lock installed on it also. Good luck!

We installed a good Dead bolt key lock.