How does FEM internal clean protection cover the wafer transfer path?

EFEM (Equipment Front End Module) is the transition area where wafers pass from the loading interface into the process equipment. The wafers are unboxed, picked out, transported and handed over here. The exposure time is long and the path involves multiple locations. Internal clean protection should cover this actual transmission path, rather than just verifying a certain fixed point.

It only measures the static state of the cavity or the manipulator, and cannot indicate the clean state during movement. The following will start from the transmission path, robot shielding, loading interface, cache bit and verification method.

Divide protection areas according to actual transmission paths

Wafer paths within an EFEM typically include:

• Loading interface and box opening position;

• Robotic arm pick-up position;

• The intermediate location through which the transmission passes;

• Cache bit or temporary storage location;

• Interface location with process equipment.

Each location has different exposure times and surrounding institutions and different protection needs. Check whether the airflow covers the wafer surface step by step along the path, rather than focusing on just one spot.

Robot movement may block the air supply

When the manipulator extends, returns, and rotates, it will change the airflow path inside the EFEM. The arms may block the air supply surface, creating local wakes or shadow areas.

Verification should cover:

• The manipulator is in a static waiting position;

• Film pickup and release actions;

• intermediate position during transmission;

• Wake effects during rapid return.

For the impact of the manipulator on air flow, please refer to How can wafer handling robots be incorporated into airflow verification? , understand the verification method under motion. For the interference of the operating arm on the air supply of the workbench, please refer to How will operating the arm interfere with the air supply to the workbench? , although the objects are different, the mechanisms of airflow obstruction are similar.

The loading interface is the weak point of the boundary

The loading interface connects the EFEM to the external environment and is a weak point in the airflow boundary. When the FOUP opens the door, the airflow at the interface may change direction and outside air may enter.

Need to confirm:

• Whether the airflow flows back into the EFEM when the door is opened;

• Is there local protective airflow around the interface?

• Is the interface pressure difference stable?

• Whether the movement of the door body affects the internal airflow.

For the protection arrangement of the FOUP door opening area, please refer to How to arrange local protective airflow in the FOUP door opening area? , understand the local protection methods at the interface.

Protection of cache bits and staging locations

The wafer may remain in a cache or staging location for a period of time. Whether the airflow covers the wafer surface during the dwell period determines whether the particles are likely to settle.

Need to confirm:

• Whether the cache location is within the air supply coverage range;

• Is the airflow stable during the stay?

• Whether the stop position is close to the dust-generating mechanism;

• Whether local enhanced protection is needed.

For the continuous protection requirements of the wafer buffer area, please refer to Does the wafer buffer area need continuous clean air supply? , understand conservation considerations in the stay state.

Airflow organization at openings and boundaries

The interior and exterior of EFEM are connected through loading interfaces and other openings. The location and size of the openings will affect internal airflow organization.

Should check:

• Whether the opening position is downstream of the protective air flow;

• Whether there are baffles or air curtains at the opening;

• Whether the internal airflow is stable when the opening changes;

• Is the internal pressure difference maintained?

For the opening and airflow boundary treatment of closed equipment cavity, please refer to How to plan clean air supply for closed equipment cavities? , to understand the impact of openings on airflow.

Air supply configuration and filtration level

Equipment-side EFU is usually used inside EFEM for local air supply. Filtration level and air supply method should be determined based on wafer sensitivity and background conditions.

For local protection on the equipment side, please refer to The EFU equipment-side fan filter unit selects a structure based on equipment space and air supply requirements. Filter level selection can be understood HEPA vs ULPA filters , check efficiency, size and installation seal. Please refer to the room background air supply FFU clean air supply products , the logic of division of labor between the two is The division of labor between device-side EFU and room FFU is explained in detail.

Verification should cover the movement process

The verification of the internal protection effect of EFEM should be carried out during the actual transfer process of the wafer, rather than just static measurement. Verification content should include:

• The grain state of the wafer at each exposed location;

• Air flow changes during the movement of the manipulator;

• The boundary state when the loading interface opens the door;

• The protection effect during the cache bit stay;

• Recovery time 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. The sampling point selection principle 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

The internal cavity test of an EFEM passed the test, but particles occasionally occurred during the wafer transfer process. The investigation found that when the manipulator extended out, it blocked part of the air supply surface, and the wafer was in a weak protection zone in the middle. Adjustment method: Adjust the EFU position and air supply direction so that the wafer path is always within effective coverage. Adjusted dynamic grain reduction.

Another item loading port has internal particles rising when opening the door. The investigation revealed that airflow was flowing backwards at the interface. Adjustment method: increase the local protective airflow at the interface and optimize the door action sequence. After adjustment, the particle peak value decreases when the door is opened.

These two situations illustrate that EFEM internal protection must cover the actual transmission path of the wafer and cannot only verify the cavity or fixed points.

Key points for selection and acceptance inspection

Aili industrial equipment supporting support

The wafer transfer path within EFEM involves multiple locations of robot movements, opening boundaries, and buffer stops. Aili Industrial has collaborative capabilities in fans, motors, filters, control systems and complete machine assembly links. It can check the EFU configuration, air supply direction, filtration level and interface conditions based on the actual wafer transmission path and equipment space, helping to cover local protection to key positions during the movement, rather than just verifying the cavity status. You can view the equipment package 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。