Effects of Target Compliance on a High-Speed Droplet Impact

High speed spray cleaning which utilize droplets impact has been used for removing contaminants from wafer surface. When a droplet impacts a solid surface at high speed, the contact periphery expands very quickly and liquid compressibility plays an important role in the initial dynamics and the formation of lateral jets. Impact results in high pressures that can clean or damage the surface. In this study, we numerically investigated a high speed droplet impacts on a solid wall. In order to compare the available theory and experiments, 1D, 2D and axisymmetric solutions are obtained. The generated pressures, shock speeds, and the lateral jetting mechanism are investigated; especially the effect of target compliance is focused. Introduction As the feature sizes of microelectronic devices is reduced, physical force, such as Megasonic, laser shock wave cleaning and high speed spray (two-fluid jet, earosol) cleaning is required to remove nano-scale particles. The main goal of this contamination control is to clean the surface without device damage. In order to avoid the damage, cleaning in the process window which is used the force between pattern collapse and particle removal is important [1]. To accomplish the evaluation of removal force of a high speed spray, we should estimate the generated pressure during a high speed droplet impact. When a high speed droplet impacts on a solid wall, there is an important initial stage during which the curved liquid surface is compressed and non-uniform pressure distribution is generated. This initial stage creates high pressure which is greater than the well-known water hammer pressure