<p>Silicon nitride (SiNx) films are widely used in electronic devices due to their insulating, chemical, and mechanical properties. However, residual stress generated during the deposition can change the properties. This study explores controlling stress in SiNx films using gas cluster ion beam (GCIB) irradiation, which larger collision cross section enables more efficient surface modification compared to monomer ion beams. Experiments showed that GCIB irradiation to SiNx film reduced the stress of the surface more uniformly than that of Ar⁺ ion beam. To elucidate the mechanism of a change in the stress, we measured the chemical composition of the surface using X-ray photoemission spectroscopy (XPS). As a result, it was revealed that surface oxidation occurred after Ar-GCIB irradiation of the SiNx film due to air exposure and the formation of the oxidation layer consequently led to the change in stress.</p> Graphical abstract <p></p>