Peeling-free porous capping material

A method for forming a dielectric structure, the method comprising:

• providing a substrate;
• depositing a low-k dielectric layer comprising a porogen over the substrate;
• in-situ depositing a low-k cap layer comprising the porogen on the low-k dielectric layer, wherein the low-k dielectric layer and the low-k cap layer are formed of substantially same precursors;
• and
• curing the low-k dielectric layer and the low-k cap layer simultaneously to remove the porogen and to create a first porosity in the low-k dielectric layer and a second porosity in the low-k cap layer, wherein the second porosity is less than the first porosity.

A semiconductor structure comprising:

• a substrate;
• a low-k dielectric layer over the substrate;
• and
• a low-k cap layer on the low-k dielectric layer, wherein the low-k dielectric layer and the low-k cap layer comprise substantially similar materials, and wherein a first porosity in the low-k dielectric layer is greater than a second porosity in the low-k cap layer.