Research Areas

- Semiconductor manufacture

In semiconductor manufacturing, wafers are repeatedly transferred between process equipment using a front opening unified pod (FOUP). During this process, moisture entering the equipment front end module (EFEM) can react with airborne molecular contamination generated by wafer outgassing, leading to residual particle formation on the wafer surface (Fig. 1). These particles may cause defects and reduce process yield. Therefore, load port purge using N₂ is applied, and optimizing its flow conditions is essential for effective wafer protection.

Fig. 1. Schematic of the EFEM–FOUP system and residual particle formation caused by moisture ingress.

- Experiment model

To reproduce the flow inside an EFEM and FOUP system, an experimental facility scaled to one third of the actual system was constructed, as shown in Fig. 2. The inlet flow passes through a flow conditioner to obtain a uniform velocity distribution and then enters the EFEM through the fan filter unit. After passing through the EFEM and FOUP, the flow is discharged through the downstream outlet. The FOUP contains three load port purge inlets, with one located at the front and two located at the rear, along with one outlet. Three wafer loading configurations were considered inside the FOUP, namely top loading (TL), bottom loading (BL), and odd layer loading (OLL). The internal flow field was measured using magnetic resonance velocimetry to obtain three dimensional and three component velocity data.

Fig. 2. Schematic of the one third scale EFEM and FOUP experimental facility and load port purge system.

- Results

Figure 3 presents the flow distributions in horizontal planes passing through selected wafer gaps, with the gap number increasing from the bottom to the top of the FOUP. Red indicates flow directed out of the FOUP, whereas blue indicates flow entering the FOUP. Under the OLL and TL conditions, the strong outflow near the top of the FOUP extends into the wafer gaps and produces outward flow between the wafers. This behavior is most pronounced under the TL condition, where outward flow is observed across a larger number of gaps. In contrast, inward flow is dominant throughout most of the wafer gaps under the BL condition.

Fig. 3. Flow distributions in selected wafer gaps for different wafer loading conditions.