## 3 Results and Discussion  
Figure 7 shows an example of the RH evolutions in the FOUP for different purge processes, that is, cases A-1 (conventional-purge), A-2 (diffuser-purge), and A-3 (panel-purge), with CDA flow rates of 120 L/min and 80 L/min for the air curtain and the FOUP-purge system, respectively. The air change rate per hour in the FOUP is around 100 for the case with the CDA flow rate of 80 L/min to the purge system. During the pre-purged period, Figure 7 demonstrates that the RHs decreased rapidly from the initial value of approximately 43% to the lower level of less than 10%, within 5 min. It then gradually approached the zero level at the end of the pre-purged process. Such RH evolutions when the door was closed approximately followed the exponential decay, as generally reported in the literature, such as [PERSON] et al. [11]. In addition, the RH decreasing characteristics of case A-3 were somewhat different from those of cases A-1 and A-2 during the pre-purged period. More specifically, the RH of case A-3 decreased much more slowly than those of cases A-1 and A-2. This was because the FOUP that was used in case A-3 was our homemade prototype with the panel-purge device, whereas the FOUP that was employed in cases A-1 and A-2 was one that is available commercially. Here, we want to emphasize that the main focus of this study was to investigate the RH evolution after opening the FOUP door in the mini-environment. The purpose of the pre-purged process in the FOUP was to ensure the same initial RH value, which was approximately 0% before opening the door, as shown in Figure 7. Therefore, the difference between our prototype and the commercial FOUP while purging with the door closed is not within the scope of the present study, but it might be interesting and needs to be further studied. After the pre-purged process and opening the FOUP door, the RH values for the three studied cases, as shown in Figure 7, increased rapidly and reached the maximum value within 4 min (both the purge system and air curtain were not used for 3 min in the beginning of this period, as previously mentioned). The maximum RH was between 40% and 42%, which was very close to the RH in the mini-environment. This result indicated that the moisture in the surroundings rapidly entered the FOUP when the door was opened in the mini-environment, without using either the purge system or the air curtain. In addition, it should be mentioned that even for the condition with the door closed, the moisture would slowly diffuse or penetrate into the purged FOUP, because of the nature of the mass transfer or leakage of the FOUP. For example, [PERSON] and [PERSON] [20] reported that the estimated RH in a purged FOUP (made of polycarbonate) could increase to more than 20% within 2 h  
Figure 7: RH evolutions for different purge processes with CDA flow rates of 120 L/min to air curtain and 80 L/min to FOUP-purge system. after purging. After the previously mentioned procedure, the CDA was supplied to both the purge system and air curtain at a given flow rate for the present experiments. Therefore, the RH values in the FOUP decreased again within the following 2 min. In addition, the results showed that the drop slope of the RH for the diffuser- and panel-purge processes was much larger than that of the conventional-purge process, indicating that the conventional purge inefficiently removed or prevented the moisture from entering the FOUP. In the final stage, the RH gradually approached steady values for the different purge processes. Figure 7 shows that the final RH values for cases A-1, A-2, and A-3 were approximately 34%, 20%, and 26%, respectively. Here, the final RH level could be used to evaluate the overall moisture prevention ability of the purge process, where a lower RH value represents a better moisture prevention ability when opening the door of the pre-purged FOUP in the mini-environment. Accordingly, the diffuser purge might be the best approach among these three studied cases.