Micron-/nano-scale contaminants adhering to microelectronic devices with dimensions in the nanoscale regime are a challenge to cleaning processes used in existing and future technologies. Such devices/patterned surfaces are generally found in the front end of the line (FEOL) of microelectronic manufacturing and on extreme ultraviolet (EUV) photomasks used in the existing and future manufacturing processes. Effective removal of these contaminants without damage to the underlying substrate requires knowledge of the adhesion force between the contaminant particle, which may have dimensions on the order of a few tens of nanometers, and the patterned substrate. In the current work, an experimental and a continuum-based theoretical study has been presented for such systems. Specifically, patterns with nanoscale dimensions were made on photomask substrates using a focused ion beam (FIB). Adhesion forces between silicon nitride particles ranging in size from the order the feature size to the micron-scale and the patterned substrates were measured for multiple particles. The observed forces were modeled by dividing the surface of the particle and substrate into single-nm wide cylindrical elements and a macroscopic approach based on pair-wise addition was used to calculate the adhesion force between the particle and the substrate, with good agreement.