A wafer gap conductivity cell determined which rinsing parameters control the removal of wafer cleaning and etching solutions. The first part of this study focused on set up and calibration of the conductivity cell. Sodium chloride solutions with known ionic conductivities are used as model fluids. Wafer rinsing experiments showing the concentration as a function of time are analyzed. The sensitivity of the wafer gap conductivity cell is compared to a wall mounted probe, the typical method used to measure rinsing efficiency. The conductivity results are explained using a fluid dynamics model of the wafer gap.
The second part of this study focused on using the wafer gap conductivity cell to study the removal of chemicals typically used in wafer cleaning processes. Experimental results show the effect of tank geometry and flow parameters on the time required for rinsing. Analysis shows the rinse process can be modeled by assuming convective fluid flow and ideal mixing. These results provide critical insight into the most important wafer rinsing parameters.