## 3 Results and Discussion
Figure 8 depicts the RH evolutions in the FOUP as a function of the CDA flow rate to the air curtain, with a given CDA flow rate of 80 L/min to the diffuser-purge system. Again, this figure demonstrates that the RH decreased rapidly and approached approximately 0% within 5 min, which was maintained until the door was opened. When the FOUP door was opened, the RH increased dramatically from 0% to approximately 40% within 4 min and, then, decreased rapidly again from its maximal value to a lower steady RH condition, because of the use of the air curtain and diffuser purge with CDA. Figure 8 also demonstrates that a higher CDA flow rate (supplied to the air curtain) yielded a lower RH at the end of the process. Specifically, the final RH values for cases A-2, B-2, and C-2, as shown in Figure 8, were approximately 20%, 13%, and 7%, respectively. Correspondingly, increasing the CDA flow rate by 42% (i.e., from 120 to 170 L/min) and 83% (i.e., from 120 to 220 L/min) resulted in decreases in the final RH of 35% (i.e., RH = 20% to 13%) and 65% (i.e., RH = 20% to 7%), respectively. The results indicated that the use of the air curtain with the CDA flow rate of 220 L/min, at a given CDA flow rate of 80 L/min, to the diffuser purge could successfully maintain the mean RH in the FOUP at less than 10% during the FOUP door opening in the mini-environment, which might be a suitable condition for practical application. Consequently, we can conclude that when a small RH in the FOUP is needed under the condition of an open door, supplying a higher CDA flow rate to the air curtain would be better than increasing the CDA flow rate supplied to the purge system, which might cause wafer vibration or induce particle contamination in the FOUP, as previously mentioned. Figure 8: RH evolutions as function of CDA flow rate to air curtain at given CDA flow rate of 80 L/min to the diffuser-purge system. Figure 9 further shows the RH evolutions in the FOUP as a function of the CDA flow rate to the air curtain at a given CDA flow rate of 80 L/min to the panel-purge system. Overall, it is clear that the RH evolution in the FOUP for the cases in Figure 9 is similar to that depicted in Figure 8. The main difference in the RH characteristics among the results presented in Figures 8 and 9 is that the final RH levels were maintained for the diffuser- and panel-purge approaches. For example, the final RH values for cases A-3, B-3, and C-3, as shown in Figure 9, were approximately 26%, 18%, and 13%, respectively. Correspondingly, increasing the CDA flow rate (supplied to the air curtain) by 42% (i.e., from 120 to 170 L/min) and 83% (i.e., from 120 to 220 L/min), resulted in decreases in the final RH in the FOUP of 31% (i.e., RH = 26% to 18%) and 50% (i.e., RH = 26% to 13%), respectively. The present results indicated that the moisture prevention performance when the panel-purge system was used was slightly lower than that when using the diffuser-purge system. However, it should be mentioned that the use of the panel-purge method could sufficiently suppress the vibration problem, especially under the condition of a higher purging flow rate. Therefore, we further studied the effects of the flow rates supplied to the air curtain and panel-purge system on the moisture prevention performance, under the condition of an open door. The total CDA flow rates supplied to the air curtain and the panel-purge system were controlled at 400 L/min for this studied case (i.e., case D). Here, cases D-1 and D-9 represent the condition where only the air curtain or panel-purge system was used, respectively. Table 2 summarizes the RH results of case D. The mean RH ranged from 1.3% to 9.8%, which indicated that all of the studied conditions of case D could maintain the mean RH in the FOUP as low as 10% or lower during the FOUP door opening. As previously mentioned, the mean RH value was calculated using 25 RH sensors in the FOUP.