An integrated circuit (IC) device is provided. The IC device includes a first die including a first substrate and a second die including a second substrate. A plasma-reflecting layer is included on an upper surface of the first die. The plasma-reflecting layer is configured to reflect a plasma therefrom. The second substrate is bonded to the first die so as to form a cavity, wherein a lower surface of the cavity is lined by the plasma-reflecting layer. A dielectric protection layer is present on a lower surface of the second die and lines the upper surface of the cavity. A material of the second substrate has a first etch rate for the plasma and a material of the dielectric protection layer has a second etch rate for the plasma. The second etch rate is less than the first etch rate.