What you are your work are "worth" is of little importance.

The ONLY way you are going to get a significant salary raise (where significant is defined as more than they're planning to give you), is if you are ready to walk.

So.

1. Have a number in mind. (ie. what are others similar in the same company making?).

2. They'll offer you less than that.

3. Say: I'm truly sorry, but I can't accept that offer, it would be hurting myself, so I have to respectfully resign. (Don't bluff, mean it)

That's really the best way.