A method includes putting a first package component into contact with a second package component. The first package component comprises a first dielectric layer including a first dielectric material, and the first dielectric material is a silicon-oxide-based dielectric material. The second package component includes a second dielectric layer including a second dielectric material different from the first dielectric material. The second dielectric material comprises silicon and an element selected from the group consisting of carbon, nitrogen, and combinations thereof. An annealing process is performed to bond the first dielectric layer to the second dielectric layer.