A couple of people suggested you could say "raise by" or "raise X on top..."
I just wanted to point out that you didn't say what the other action at the table was. If you say "raise by 15", it doesn't mean $15 on top of your $1 blind; it means $15 on top of the current bet, whatever that is. Even if nobody had raised, you were the small blind... so the bet must be at least $2 already, right? "Raise by $15" is 15 above 2... so it's the same as "Raise to $17."
If you want the total bet to be $15, the safest thing is to say "raise to $15" or "make it $15." These refer to the total bet.
If the bet had been $2 before you acted, this would be the same as saying, "raise by $13."
If the bet had been $6 before you acted, this would be the same as saying, "raise by $9."
All three of these examples put the current total at $15.
Once the bet is verbally at $15... it doesn't matter how you do it. You can add $14 to your $1, or you can put up $15 in redbirds and take back the $1... if you have a professional dealer, you can even just put up $15 in redbirds, and the dealer will take care of kicking back your $1 for you.