Evaluation of a wafer transportation speed for propulsion nozzle array on air levitation system

A transportation system of single wafer has been developed to be applied to semiconductor manufacturing process of the next generation. In this study, the experimental apparatus consists of two kinds of track, one is for propelling a wafer, so called control track, the other is for generating an air film to transfer a wafer, so called transfer track. The wafer transportation speed has been evaluated by the numerical and the experimental methods for three types of nozzle position array (i.e., the front-, face- and rear-array) in an air levitation system. Test facility for 300 mm wafer has been equipped with two control tracks and one transfer track of 1500 mm length from the starting point to the stopping point. From the present results, it is found that the experimental values of the wafer transportation speed are well in agreement with the computed ones. Namely, the computed values of the maximum wafer transportation speed Vmax are slightly higher than the experimental ones by about 15–20%. The disparities in Vmax between the numerical and the experimental results become smaller as the air velocity increases. Also, at the same air flow rate, the order of wafer transportation speeds is: V_max for the front-array > V_max for the face-array > V_max for the rear-array. However, the face-array is rather more stable than any other type of nozzle array to ensure safe transportation of a wafer.