Characterization of Warpage of Ultra-Low-K Dielectric Materials and Correlation with Modulus and Coefficient of Thermal Expansion

Advanced high-performance computing (HPC) and artificial intelligence (AI) systems demand arger glass package systems that may extend to 200 mm × 200 mm package size. This large package sizes invariably require stringent properties of the insulation/build-up layers consisting of low to Ultra-low K (ULK) dielectric polymers. The inclusion of ULK polymer layers is of great importance to improve latency, signal integrity and energy per bit owing to their reduced capacitance. However, ULK polymers are typically without any added filler particles and hence need to be thoroughly characterized to realize a good control on yield ad reliability. Particularly in the case of fine line RDL (< 2 μm Lines/Spaces) both RDL critical dimensions yield and reliability depend upon the warpage, surface roughness of the dielectric insulation layer. Hence it is of great significance to measure the warpage of the ULK layer in order to understand the influence of warpage on yield of fine line RDL across the entire length of the package. By virtue of the molecular groups present in ULK polymers which consist of moderately fluorinated to perfluorinated moieties in the backbone, evaluation of potential correlation between warpage to yield, adhesion strength and surface roughness is of great importance. The ULK polymers investigated in this paper include photo-imageable and non-photo-imageable dielectric polymers.