## 1 Introduction
For example, only one large vortex formed in the cavity when L/D = 1, which was very close to the condition of the FOUP, without loading any wafer during the door opening in the mini-environment. When the FOUP was loaded with several wafers, several vortices could be generated near the front regions of the FOUP. Those vortices would transport the moisture and contamination from the surroundings into the FOUP. In addition, the Reynolds number of the air flow is another important parameter that affects the characteristics of the induced vortex [13; 14]. Therefore, when a FOUP door is opened, additional methods are generally used to prevent outside contamination (such as moisture, oxygen, and particles) from entering the FOUP, for example, [PERSON] et al. [15] employed an air curtain to meet this goal. However, few studies in the available literature have considered the condition where the FOUP door was opened. In one example, [PERSON] et al. [16], explored the humidity evolution in the FOUP during a door-closed process, with an equipment-front-end-module (EFEM) load port unit. They found that the outside airflow would cause a vortex near the lower regions of the FOUP, which made it difficult to decrease the RH to a very-low level. To solve this problem, they further developed flow distributors (i.e., diffusers) for the FOUP, and the results demonstrated that the RH could be reduced to less than 10%. [PERSON] and [PERSON] [17] reported that the air flow pattern from the EFEM affected the performance of the diffuser-purge process, especially for a condition where the EFEM's air flow was much stronger than the purging flow. They further developed and installed an EFEM flow converter above the FOUP opening, which could turn the air flow into a uniform-downward laminar flow, and therefore improve the purge performance. Recently, [PERSON] et al. [18] employed two different approaches to study the moisture prevention performance while opening the FOUP door in a mini-environment. The results showed that better moisture prevention was obtained near the FOUP's lower regions when using a diffuser purge, whereas better prevention was obtained near the FOUP'supper regions when using the air curtain. They further suggested that the diffuser purge integrated with air curtain is an appropriate way to prevent moisture in a practical application. Although the use of diffusers in a FOUP while purging can efficiently prevent or remove the contamination from the FOUP when its door is opened or closed, a higher purging flow rate would induce particle contamination and vibration problems. In addition, it should be mentioned that, if the vibration of the FOUP or wafers is too strong, wafer breakage could occur, especially for a wafer with already fabricated patterns. During the practical manufacturing processes, the purging flow rate is generally limited to 130 L/min (or even lower), in order to avoid the previously mentioned problems. The present study investigates the effect of the CDA flow rate, supplied to the purge system and air curtain, on the moisture prevention performance while opening the FOUP door. To reduce any possible vibration, we further developed and tested a prototype for a new panel-purge device in the FOUP, instead of the diffuser or conventional purge, during the FOUP purging with the door opened and the air curtain in use.