Integrated circuit packages and methods of forming the same

In an embodiment, a device includes: a first integrated circuit die; a second integrated circuit die bonded to the first integrated circuit die in a face-to-back manner; a dummy semiconductor feature adjacent the second integrated circuit die and bonded to the first integrated circuit die; a support substrate attached to the dummy semiconductor feature and the second integrated circuit die; and a passivation layer extending along a top surface of the support substrate, an outer sidewall of the dummy semiconductor feature, an outer sidewall of the first integrated circuit die, and a top surface of the first integrated circuit die.