Semiconductor structure and forming method thereof

The invention discloses a semiconductor structure and a forming method thereof, the structure comprises a wafer, the wafer comprises a substrate and a dielectric layer located on the substrate, an interconnection structure is formed in the dielectric layer, and the interconnection structure comprises a top interconnection layer farthest from the substrate; the low-refractive-index dielectric layer is located at the top of the top interconnection layer; the one or more grooves are located in the low-refractive-index dielectric layer; the high-refractive-index dielectric layer is located at the top of the low-refractive-index dielectric layer and is filled in the groove; the metal bonding layer is located on the side portion of the groove and sequentially penetrates through the high-refractive-index dielectric layer and the low-refractive-index dielectric layer, and the metal bonding layer is electrically connected with the top interconnection layer. The probability that the top of the metal bonding layer is re