An embodiment is a method including depositing a first flowable film over a substrate in a processing region, the first flowable film comprising silicon and nitrogen, curing the first flowable film in a first step at a first temperature with a first process gas and ultra-violet light, the first process gas including oxygen, curing the first flowable film in a second step at a second temperature with a second process gas and ultra-violet light, the second process gas being different than the first process gas, and annealing the cured first flowable film at a third temperature to convert the cured first flowable film into a silicon oxide film over the substrate.