The present disclosure relates to an integrated chip comprising a pair of first metal lines over a substrate. A first interlayer dielectric (ILD) layer is laterally between the pair of first metal lines. The first ILD layer comprises a first dielectric material. A pair of spacers are on opposite sides of the first ILD layer and are laterally separated from the first ILD layer by a pair of cavities. The pair of spacers comprise a second dielectric material. Further, the pair of cavities are defined by opposing sidewalls of the first ILD layer and sidewalls of the pair of spacers that face the first ILD layer.