How can wafer handling stations reduce dust during exposure?

The wafer loading station is the transition area where wafers are transferred from the controlled container to the interior of the equipment. At this stage, the wafer is removed from the FOUP or other container, clamped and transferred, and entered inside the equipment. Although the exposure time is short, if protection is not in place, particles may settle on the wafer surface.

Reducing exposure to falling dust requires covering openings, clamping and transfer areas with clean air while controlling personnel, material and institutional sources. Protection should continue until the wafer is in a controlled position and cannot focus on a static point on the loading dock.

First clearly define the exposure period

The exposure period of wafers at the loading and unloading station usually includes:

• The moment the container opens the door;

• Robotic arm picking and clamping;

• Transfer of wafers from container to inside the equipment;

• Waiting and handover.

Exposure conditions and risks vary for each period. The exposure period should be calibrated first, and then the protection scope should be determined. 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? , learn about local protection methods for openings.

The opening position is the main path for particles to enter

When the container is opened, the opening is connected to the external environment, and particles may enter through the opening. The protective airflow should cover the opening to reduce the entry of outside air.

Need to confirm:

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

• Whether there is local protective airflow at the opening;

• Is the direction of the opening facing the source of pollution?

• Is there any accumulation of particles around the opening?

For the airflow organization at the opening boundary, please refer to How to plan clean air supply for closed equipment cavities? , understand airflow management in the open state.

Air flow coverage of clamping and transfer areas

When a robot grips a wafer, the clamps and arms change local airflow. During the transfer process, the wafer passes through different positions, and whether the protective air flow continues to cover it is key.

Need to confirm:

• Whether the clamping position is within the air supply range;

• Whether the movement of the manipulator blocks the air supply;

• Whether the path the wafer passes through is protected throughout;

• Is the airflow at the handover location stable?

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.

Exposure time control

The longer the exposure, the greater the chance of particle settling. Reducing exposure time reduces the risk of dust fallout.

Consider:

• Optimize the manipulator movement speed;

• Reduce waiting and dwell times;

• Avoid unnecessary repetitive actions;

• Shorten the wafer's dwell time in the open position.

Exposure time control and airflow protection should be performed simultaneously. If the protective airflow is insufficient, shortening the time can only reduce the risk, not eliminate it.

Control of personnel and institutional sources

Particles may be generated by human activities and mechanism movements near loading and unloading stations. These sources should be controlled:

• Reduce people walking around openings;

• Check the lubrication and wear status of the mechanism;

• Avoid performing maintenance or cleaning near sensitive locations;

• Control the placement of materials and tools.

For the impact of personnel activities on airflow, please refer to How will operating the arm interfere with the air supply to the workbench? , learn how to troubleshoot motion interference.

Protection should extend to the end of transfer

Protection should not cover only one stationary point of the loading dock. After the wafer is removed from the container and enters the equipment through the transfer path, protection should continue until the wafer enters a controlled position.

Need to confirm:

• Whether the middle position of the transfer path is protected;

• Whether the handover point is within the airflow coverage area;

• Whether the internal entrance of the equipment is partially protected;

• Whether there is an interruption in protection.

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

Air supply configuration and filtration level

The local protection of loading and unloading stations can be configured with equipment-side EFU, and the structure can be selected according to space and air supply requirements. The level of filtration should be determined based on wafer sensitivity.

Please refer to the equipment side supporting EFU equipment end fan filter unit , the filtration level 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.

Dynamic validation of coverage loading and unloading cycles

The verification of loading and unloading stations should be carried out during the actual loading and unloading cycle, rather than just static testing. Verification content should include:

• airflow and particles when opening doors;

• Airflow during film removal and clamping;

• The particle state at each position on the transfer path;

• Protection effect of handover position;

• 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. Related methods can be found in Why can’t the sampling point be located just below the air supply outlet? and How does a change in working height affect the detection position?。

Project judgment example

Dust occasionally falls on wafers at a certain loading and unloading station. The investigation found that the air supply was blocked when the robot was picking up the wafers, and the wafers were in a weak protection zone at the clamping position. Adjustment method: Adjust the air supply direction so that the clamping position is within the air flow coverage range. After adjustment, the dust is reduced.

Another project showed particles on the wafer surface when opening the door. The investigation revealed that the air flow was flowing backwards at the opening and outside air was entering. Adjustment method: increase the local protective airflow at the opening and optimize the door opening sequence. After adjustment, particles decrease when opening the door.

These two situations illustrate that: to reduce dust in the wafer loading and unloading station, openings, clamping and transfer areas need to be covered, and protection should continue until the wafer enters a controlled position.

Key points for selection and acceptance inspection

Aili industrial equipment supporting support

Dust control at wafer loading and unloading stations needs to cover openings, clamping and transfer areas. 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 protection range based on the wafer loading and unloading path, robot movement and equipment space, helping to extend local protection to key positions in the transfer process, rather than just focusing on a static point on the loading and unloading platform. 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。