To improve the cleaning processes in recent semiconductor manufacturing processes, it is important to understand the solidification phenomenon and its impact on nanometer−scale patterns. In this study, the origin of the forces acting on a silica surface from an ice−solidification interface was investigated using molecular dynamics simulations. The microscopic forces were determined by appropriately averaging the forces acting on the silica wall from the water molecules in time and space. During the solidification processes, the time evolutions of these microscopic forces for changing the time−averaged widths were investigated for the crystalline and amorphous silica surfaces. The results indicated that the fluctuation of microscopic forces increased after the solidification interface makes contact with the wall surface. This tendency was clearly observed for longer time−averaged widths and was also more pronounced on an amorphous silica surface with a random configuration of the silanol groups.