Structures and methods for reducing thermal expansion mismatch during integrated circuit packaging

A semiconductor structure, comprising:

• a first metal layer comprising a first device metal structure over a substrate;
• a dielectric region formed over the first metal layer, wherein the dielectric region comprises a top dummy metal structure over the first device metal structure, and a dielectric material interfacing a sidewall of the top dummy metal structure and having a lower coefficient of thermal expansion than the top dummy metal structure;
• and
• a polymer region formed over the dielectric region, wherein the polymer region comprises a dummy metal redistribution layer (RDL) structure, wherein the polymer region has a higher coefficient of thermal expansion than that of the dielectric region, and the dummy metal RDL structure decreases an average coefficient of thermal expansion of the polymer region.

A method for manufacturing a semiconductor structure, comprising:

• forming a first metal layer comprising a first device metal structure over a substrate;
• forming a dielectric region over the first metal layer, wherein the dielectric region is formed by:
• forming a plurality of metal layers each of which comprises a dummy metal structure embedded in the dielectric region over the first device metal structure, and forming an inter-metal dielectric layer comprising dielectric material between each pair of two adjacent metal layers in the plurality of metal layers;
• and
• forming a polymer region over the dielectric region, wherein:
• the polymer region comprises a redistribution layer (RDL) comprising a dummy metal RDL structure,
• the polymer region has a higher coefficient of thermal expansion than that of the dielectric region, and the dummy metal RDL structure decreases an average coefficient of thermal expansion of the polymer region, wherein the dummy metal structures have a higher coefficient of thermal expansion than that of the dielectric material interfacing sidewalls of the dummy metal structures.