Thanks to @JoelK for referring the verse in Yeshayahu (Isaiah) 45:7, which is where these words are found (besides the siddur, of course.)
The full expression in Isaiah is
יוצר אור ובורא חשך עושה שלום ובורא רע
"He fashions light and creates darkness; makes peace and creates
Rada"k commentary explains that the term יוצר is used for light and עושה for peace because these things must be formed or made (I don't know why the term יוצר isn't repeated for peace, but, that may be nothing more than Nach"s poetic "parallelism", here.) However, for darkness and evil, the term בורא is used because these are not actual things but rather the removal of something that exists. Darkness is the removal (absence) of light and evil is the removal (absence) of peace.
I'm inferring that as a general rule, the term יוצר is used for the fashioning of something new. However, in relating the term בורא to the "absence" of something, I don't see how that can be generalized or how Rada"k determines this. I'd appreciate if someone can edit in an explanation of this nuance.