## 2 Experiment and Apparatus  
The experiments were carried out in a clean room with ISO Class-6 level (Figure 1a), where a mini-environment with ISO Class-2 level was established (Figure 1b). The temperature and RH values in the clean room were maintained at 22 \(\pm\) 0.5 \({}^{\circ}\)C and 42 \(\pm\) 2\(\%\), respectively. In this clean room, twelve FFUs and three fan dry coil units (FDCUs) were mounted on the ceiling, and four dry cooling coil (DCC) units were installed on the ceiling near two side-walls (in the pathways for the return air). In order to establish a higher cleanliness level, three FFUs were also installed on the top of the mini-environment. In addition, to ensure improve the uniformity for the air flow provided by the FFUs in the mini-environment, a perforated plate with an opening ratio of 46.5\(\%\) was used at a location 5 cm below the FFUs, and three perforated plates with an opening ratio of 30\(\%\) were installed on the ground level of the mini-environment. The velocities of airflow from the FFUs in the clean room and mini-environment were 0.45 m/s and 0.4 m/s, respectively. An LPU module (model: KWF-12F-M, Hirata, Japan) combined with the purging system (Brillian Network & Automation Integrated System, Miaoli, Taiwan) was employed. It was mounted on the interface of the mini-environment, as shown in Figure 1b. Figure 2 further illustrates the procedures for the LPU when mounting the FOUP on the interface of the mini-environment. This figure shows that the FOUP door was opened by the front-opening interface mechanism of the LPU (steps II to IV), after the FOUP was located on the LPU (step I). Step IV illustrates the situation of air flowing downward and over an open cavity (if the FOUP does not store any wafer), as previously mentioned. Figure 1: Testing environment of the present study: (**a**) ISO Class-6 clean room and (**b**) ISO Class-2 mini-environment. FFU—fan filter units; DCC—dry cooling coil; FOUP—front opening unified pod; LPU—load port unit. This study employed three different purge types for the FOUP, as shown in Figure 3, in order to investigate the moisture prevention performance. Figure 3a illustrates the FOUP using the conventional purge, which has two inlets (near the back-bottom region, which cannot be observed in the figure) and two outlets (near the front-bottom region of the FOUP) for the purge gas. Figure 3b depicts the FOUP-purge inlets mounted with two diffusers, which are porous tubes with a diameter of 1.3 cm and length of 23.6 cm. These porous tubes were made of ultra-high molecular weight polyethylene (UPE). The FOUP, which can store 25,300 mm wafers and is used for both the conventional-purge and diffuser-purge experiments, was provided by Entegris (model: A300, Hsinchu, Taiwan). Figure 3c shows the appearance of the FOUP used for the panel-purge experiments, which was developed by the present research team and fabricated using three-dimensional (3D) printing with polylactic acid polymer materials. As shown in Figure 3c, three UPE porous boards with a pore size of 0.1 \(\upmu\)m were installed in the back region of this homemade FOUP. These UPE boards could serve as ventilation plates (and panel-purge inlets), which improved the flow uniformity while purging with CDA. Figure 4 provides a detailed schematic of the developed FOUP with the panel-purge device. Three back-side covers were further mounted on the exterior of these boards, and each cover had two inlet holes for the purging process. In addition, the small regions between the UPE boards and the outer covers could serve as buffer regions while purging. Figure 3: Different types of FOUPs employed for (**a**) conventional-purge, (**b**) diffuser-purge, and (**c**) panel-purge processes. Figure 2: Procedures for LPU with FOUP mounted on the interface of a mini-environment. We used aluminum alloy #6061 to prepare a dummy wafer that was 1 mm thick (i.e., a supporting base for mounting the RH sensors) and had a diameter of 302 mm.