How to arrange local protective airflow in the FOUP door opening area?

The FOUP door opening area is the key interface for wafers to enter the equipment from the closed container. When the door is opened, the inside of the container is connected to the equipment environment, and external air, particles on the outer surface of the container, and door movements may affect the wafer. Local protective airflow needs to cover openings, wafer pick-up and placement, and adjacent transfer locations to prevent background air from directly entering sensitive paths.

Protection methods cannot rely solely on the grade label of a certain outlet surface. The opening structure, door movement, wafer path and adjacent positions all need to be checked together.

Opening the door changes the airflow boundary

When FOUP opens the door, the door body movement, interface gaps and internal mechanism actions will change the local airflow boundary. After the originally closed container is opened, the internal environment is connected with the equipment environment, and airflow may enter or exit through the opening.

Need to confirm:

• Is the airflow direction stable when opening the door?

• Whether there is backflow at the interface;

• Whether the movement of the door disturbs the protective airflow;

• Is there any accumulation of particles around the opening?

For changes in airflow in the open state, please refer to How to plan clean air supply for closed equipment cavities? , to understand the impact of openings on airflow paths. For the exposure process of wafers from container to equipment, please refer to How can wafer handling stations reduce dust during exposure? , first calibrate the exposure period.

Protective airflow should cover openings and access paths

The goal of local protection is to allow clean air to cover openings, wafer removal locations, and transfer starting points. If the protection range is insufficient, the wafer may pass through a weak protection zone after leaving the container.

Need to confirm:

• Whether the opening is within the air supply coverage area;

• Whether there is protective airflow at the location where the film is taken;

• Whether the first path of the wafer from the container to the interior of the device is covered;

• Whether there is an interruption in protection.

For the coverage method of EFEM internal transmission path, please refer to How does EFEM internal clean protection cover the wafer transfer path? , understand the idea of ​​path protection.

Prevent background air from entering through side seams

There are usually side seams and connection parts between the FOUP and the equipment interface. These gaps may serve as pathways for background air to enter.

During inspection you should pay attention to:

• Sealing status around the interface;

• Whether there is airflow entering through the side seams;

• Is the pressure difference at the interface stable?

• Does the gap expand when the door is opened?

If background air enters through side seams, local protective airflow may be diluted or deflected. For inspection methods of interface sealing, please refer to What should be checked when cleaning equipment is accepted? , to understand the installation status verification ideas.

The relationship between door body movement and air flow direction

The door opening direction and speed will affect local airflow. Rapid movement of the door may cause instantaneous airflow disturbances, bringing particles into the wafer path.

Need to consider:

• Whether the door opening direction is toward the wafer path;

• Whether the door opening speed causes airflow fluctuations;

• Whether the door blocks the air supply;

• Whether the door opening timing is coordinated with the wafer removal action.

For coordination of door body movement and air flow, please refer to How can wafer handling robots be incorporated into airflow verification? , understand the verification method under motion.

Confirm the protection method based on the actual structure of FOUP

Different FOUP structures and interface forms are different, and the protection method needs to be confirmed based on the actual situation. Designed only according to standard interface dimensions, differences in door structure, sealing methods and connection locations may be ignored.

Confirmation content should include:

• FOUP model and interface size;

• Door structure and opening method;

• Interface sealing and connection form;

• The arrangement position of the wafers in the container;

• The cooperation between the film taking mechanism and the interface.

The relationship between local air supply and overall machine airflow

The local protection of the FOUP door opening area is part of the overall air flow of the equipment. The local air supply cannot conflict with the internal air flow of the EFEM, nor can it affect the pressure difference relationship of the loading interface.

Need to confirm:

• Is the local air supply direction coordinated with the EFEM internal air supply direction?

• Whether local protection affects the interface pressure difference;

• Whether the return air path supports local airflow discharge;

• Whether independent control or linkage is required.

EFU is commonly used for partial protection at the equipment end, and the structure can be selected based on the loading end space and air supply requirements. When it comes to the overall airflow inside the equipment, please refer to How do the equipment-side EFU and room-side FFU divide their labor ? Understand the control division of labor between the equipment side and the room side.

Dynamic verification covers the door opening and pick-and-place processes

The verification of the FOUP door opening area should be carried out during the actual door opening and pick-up and placement processes, rather than just static testing. Verification content should include:

• Changes in airflow and particles at the moment of opening the door;

• Airflow coverage at the film removal location;

• The path grain state of the wafer after it leaves the container;

• The recovery situation after the door body is closed;

• Repeatability under dynamic conditions.

The location of the sampling point should cover the actual location where the wafer passes, rather than just under the air supply port. Sampling methods can be referred to Why can’t the sampling point be located just below the air supply outlet? , please refer to the height selection How does a change in working height affect the detection position?。

Project judgment example

Occasional particles appeared on the surface of the wafer when the FOUP was opened in a certain project. The investigation found that background air entered the side seam of the interface, and particles were brought into the film taking path when the door was opened. Adjustment method: Improve the interface seal, adjust the local protective air flow direction, cover the opening and the film removal position. After adjustment, particles decrease when opening the door.

In another project, the airflow fluctuated significantly when the door body moved. Adjustment method: Adjust the door opening speed and timing to coordinate the door movement with wafer removal, and check the local air supply direction. Airflow stability is improved after adjustment.

These two situations illustrate that the partial protection of the FOUP door opening area needs to cover the opening, pick-and-place path and interface gap, and combine the door movement and wafer path confirmation.

Key points for selection and acceptance inspection

Aili industrial equipment supporting support

The local protection of the FOUP door opening area involves the coordination of the opening structure, door body movement, wafer path and overall machine airflow. Aili Industrial has collaborative capabilities in fans, motors, filters, control systems and complete machine assembly links. It can check the local air supply direction, filtering configuration and control method based on the loading end structure, wafer pick-and-place path and equipment space, helping to cover the protective airflow to the key positions of opening the door and picking up wafers, instead of just judging by the level of the air outlet surface. Device side supporting can be viewed EFU equipment end fan filter unit , please refer to the filter package. HEPA and ULPA filters , please refer to room air supply FFU clean air supply products。