The auto mode is decomposed into five DPs as shown in Table 4. The auto mode overhead organizes the whole auto mode structure and coordinates four other DPs. The recipe link loads and unloads the recipe, edited and saved by the recipe editor. The user interface handles the interaction between the user and the auto mode. The machine-level interface provides the communication channel between the auto mode and the machine. These three DPs function as the I/O stream of the auto mode. The process steps are the preprogrammed autonomous stages to support the recipe based automatic wafer processing. In conjunction with the process parameters downloaded from a recipe file, the sequential execution of the steps induces the intended physical change of the wafers.