High Aspect Ratio, High Resolution, and Broad Process Window Description of a Low Loss Photodielectric for 5G HS/HF Applications Using High and Low Numerical Aperture Photolithography Tools

Fifth Generation (5G) network and high speed/high frequency (HS/HF) technology is the key to setting higher transmission rates and improved connectivity but will require significant innovation from materials to enable the manufacturing and performance of future networks. Photoimageable Dielectrics (PID) are set to play a large role in the manufacturing of panel and wafer level packaging of 5G circuits, but PID materials and imaging mechanisms currently rely on chemistry with high dipole moments and heteroatoms which possess dielectric losses (Df) too high for 5G devices at desirable form factors. A newly developed polymer platform has been identified as a potential useful material for 5G PID, the new material possessing a low Df (0.004 at 30GHz) at a low curing temperature (under 200°C for one hour), self-priming adhesion to relevant substrates (silicon, copper, silicon nitride, polyimide), low moisture absorption, as well as a desirable solvent based developer: propylene glycol monomethyl ether acetate (PGMEA). Herein, targeting a 15 μm final film thickness, the effect of processing conditions on resolution, via shape and process window are described on a high numerical aperture (NA = 0.48) stepper, a low NA (0.1) stepper, and a Mask Aligner through different soft and post exposure bake conditions. High resolution (6 μm via) and high aspect ratio (2.5:1) can be achieved. Elements critical to the lithographic process including Bossung curves, bake conditions and tradeoffs in resolution versus desirable side-wall angle over different tools demonstrate processing surfaces towards the successful implementation of photodielectrics for 5G applications with stringent lithographic requirements.