A highly effective moisture removal technique for front opening unified pods (FOUPs) can significantly improve the production yield of semiconductor manufacturing industries by minimizing the number of faulty dies rejected due to humidity related defects in silicon wafers. In this study, FOUP purging using clean dry air (CDA) was applied using conventional and diffuser purge method. An innovative laminar air curtain was also used to increase the performance of the FOUP purging techniques. These moisture removal techniques were applied in an open FOUP connected to a mini-environment in which a local exhaust ventilation (LEV) was installed. A novel smoke flow visualization technique and particle image velocimetry (PIV) were employed to visualize the flow pattern inside the FOUP and to generate a velocity vector field from the flow field. In addition, digital humidity sensors were installed inside the FOUP to evaluate the performance of the techniques. The flow analysis and humidity data show that the air curtain can significantly improve the performance of the purge methods. The observations demonstrate that the application of the air curtain, in combination with diffuser purge, can significantly improve the FOUP cleanliness. The LEV system was not found to have influence on the flow field inside the FOUP.

Moisture removal techniques such as purge have been developed for the front opening unified pod (FOUP) in the semiconductor industry. The FOUP purge can significantly increase the quality of integrated circuit (IC) products. An experimental model of a simulated clean room, was designed at Taipei Tech. A mini environment (ME) and a FOUP were installed inside the model. Smoke flow visualization technique was performed with the assistance of an innovative laser light sheet generation system. A homemade smoke generator simulates the moist air flow pattern into the FOUP. The FOUP top view flow pattern was recorded by a Hamamatsu digital camera. The particle image velocimetry (PIV) in the FOUP horizontal plane was analyzed. Moreover, the relative humidity (RH) was monitored inside the FOUP. The results show that a purge flow rate of 200 LPM is the optimum purge flow rate for moisture removal performance inside the FOUP. The findings of the present study could significantly increase the quality of chip products in semiconductor manufacturing, decreasing product defect rates and significantly reducing energy consumption.

Minimizing airborne molecular contamination (AMC) and moisture significantly decreases the defect rate of semiconductor products during manufacturing. Humid air originating from the fan filter unit (FFU) that is located at the top of a mini-environment (ME) might be transferred into a front opening unified pod (FOUP). Different moisture removal techniques such as diffuser purge and air curtain were applied to minimize the humidity level inside the FOUP. This computational fluid dynamics (CFD) numerical study evaluates the relative humidity (RH) level inside the FOUP subjected to different moisture removal techniques when the door is open. Different practical purge and air curtain flow rates were simulated. The large eddy simulation (LES) model was performed to simulate eddies inside the FOUP and ME. The relative humidity contours were also simulated inside the FOUP and ME. The results of the simulations were verified by experimental RH measurements. The findings show that combining the methods of diffuser purge and air curtain with flow rates of 130 and 360 LPM respectively has the highest moisture removal efficiency. This method can significantly decrease the humidity level inside the FOUP, resulting in a decrease in the defect rate on silicon wafers during manufacturing and storage.

In recent years, the semiconductor industry has continued to advance production techniques and reduce chip feature size. The presence of unwanted moisture during the construction of these features increases the risk of chip defects and reduced yield. During production, smaller integrated circuit (IC) products are more sensitive to the presence of moisture. Therefore, increasing the efficiency of moisture control techniques is very important to decrease the product defect rate. Front opening unified pods (FOUPs) are the plastic enclosure boxes that are designed to provide a cleaner environment for semiconductor wafers during manufacturing and storage. Clean dry air (CDA) or nitrogen (N2) can purge moist air out from the FOUP. For the first time, in this study the effect of purge flow rate on the moisture removal efficiency of a loaded FOUP was examined accurately via smoke flow visualization, particle image velocimetry (PIV) and relative humidity (RH) measurement. Moreover, two different wafer arrangements of top-empty and bottom-empty FOUP were investigated. The findings show the bottom-empty FOUP arrangement results in higher purge performance compared to the top-empty FOUP arrangement. Four purge flow rates of 130, 200, 300 and 400 LPM were examined. The findings also show that when the purge flow rate was set to 200 LPM, the lowest level of relative humidity was measured inside the FOUP. Therefore, the purge flow rate of 200 LPM and the bottom-empty FOUP arrangement can minimize the humidity invasion into a loaded FOUP. The findings from this study can be beneficial to the industry to optimize the purge flow rate and to define the most efficient arrangement of the wafers inside the FOUP during manufacturing and storage. This can increase the product quality and reduce energy consumption by decreasing product defects and increasing yield.

Microchip features continue to reduce in size year after year. Oxygen (O ₂ ) and moisture present in ambient air can cause product defects and therefore lower production yield. Smaller feature sizes are more sensitive to humidity and oxygen, resulting in a greater potential for defects to arise during wafer processing. Therefore, the level of oxygen and moisture needs to be minimized during integrated circuit (IC) manufacturing. Purge gases like clean dry air (CDA) or nitrogen (N ₂ ) are commonly used to reduce the level of oxygen and moisture inside a front opening unified pod (FOUP). In this study, purge cleaning performance was experimentally assessed by streamlines flow analysis, particle image velocimetry (PIV), relative humidity (RH) measurement, and oxygen concentration measurements during purging with practical flow rates of 130, 200 and 300 LPM. The experiments show 200 LPM can be the optimum purge flow rate for a high level of cleaning efficiency and a low level of vibration and instabilities. This purge flow rate can be used to increase product quality through a reduction in defect frequency, while reducing annual energy consumption by the semiconductor manufacturing industry.

Contamination control and mitigation is a vital function in the semiconductor manufacturing process, especially with the ever-decreasing feature size of wafers making them more prone and sensitive to contamination. If not properly handled, it could lead to the formation of wafer defects extending to yield reduction and device performance deterioration. Purging the front opening unified pods (FOUP) that carry semiconductor wafers between process steps by the use of diffuser purge and air curtain technology are just two examples of approaches by which contamination could be controlled. With the optimization objective of minimizing both the relative humidity (RH) and total clean dry air (CDA) that would be used by both diffuser-purge and laminar air curtain supply, in this study, the optimum values predicted for the input parameters using the response surface optimization (RSO) tool by Ansys DesignXplorer are as follows: 30 mm air curtain width, 0.3 m/s FFU velocity, 0.3 m/s air curtain velocity and 130.01 l/min flow rate total for the two diffuser-purge. These optimum values of the aforementioned parameters are predicted to maintain the allowable amount of moisture inside the FOUP as specified by the semiconductor industry, while using the least amount of clean dry air.