Does the wafer buffer area need continuous clean air supply?

The wafer buffer is the location where wafers wait and are temporarily stored within the equipment. When the equipment is running, the wafer may stay here for a period of time before entering the next process. Wafers may also remain in the buffer while the equipment is down or in standby.

Whether the buffer area needs continuous clean air supply cannot be generalized. Judgment should be based on wafer exposure status, dwell time, enclosure boundaries, and recovery requirements. The temporary inactivity of the equipment does not mean that the air protection can be stopped.

First confirm the exposure status of the wafer

To determine whether continuous air supply is required, first check whether the wafer is exposed in the buffer area:

• Whether the wafer is placed in a closed container;

• Whether the container has a filter or sealing structure;

• Whether the wafer surface is directly exposed to the internal environment of the device;

• Exposure area and exposure time.

If the wafer is placed in a closed container, and the container seal is effective, the need for continuous air supply may be lower. If the wafer is directly exposed to the internal environment of the equipment, continuous protection is usually required. For protection requirements in wafer loading, unloading and pick-and-place processes, please refer to How can wafer handling stations reduce dust during exposure? , understand the protection considerations for exposed links.

Residence time affects protection needs

The residence time of the wafer in the buffer area directly affects the chance of particle settling. The longer the stay, the greater the need for continued protection.

When judging, you should confirm:

• How long the wafer stays in the buffer during normal operation;

• Whether the wafer remains in the buffer area during standby and shutdown;

• What is the maximum length of stay;

• Whether the environment is stable during the stay.

If the residence time is long, even if the air supply is stopped for a short time, the particles may settle. For relevant considerations, please refer to Does the wafer buffer area need continuous clean air supply? In the analysis of exposure conditions, the residence time is included in the judgment.

There may still be contamination input in the standby state

When the equipment is on standby, the mechanism does not move, but the pollution input does not necessarily disappear:

• Background particles may enter through gaps;

• Particles may be introduced by adjacent equipment or personnel activities;

• Residual particles inside the equipment may be resuspended;

• Changes in temperature and humidity may affect surface condition.

If the air supply is stopped, the airflow boundaries of the buffer area will change and the original protection range may no longer be effective. For protection requirements in standby state, please refer to How to plan clean air supply for closed equipment cavities? , understand the impact openings and gaps have on airflow.

Load reduction is subject to status verification

If the project wants to reduce the air supply volume or stop the air supply during standby, it should go through status verification instead of shutting down directly.

Verification content should include:

• The granular changes in the buffer area during standby state;

• The particle recovery trend after the wind stops;

• Grain changes on restart;

• Whether the wafer surface state is affected.

Only when it is confirmed that the wind stoppage does not affect the wafer state can the load-reducing operating mode be adopted. For recovery verification and status confirmation, please refer to Which equipment should be in operation during acceptance? , understand the verification requirements under different operating states.

Recovery and restart handling

When returning from standby mode to active mode, the cache area may undergo an airflow re-establishment process. Should confirm:

• Check whether the air flow is stable after the air supply is restored;

• Whether the recovery time meets the process requirements;

• Whether there is a need to delay wafer removal;

• Processing procedures after abnormal shutdown.

There should be clear requirements for post-outage processing, rather than replacing verification with fixed waiting times.

Coordination of local air supply and overall machine airflow

The local air supply in the buffer area is part of the overall air flow of the equipment. Continuous air supply needs to be coordinated with the air flow of the whole machine:

• Whether the air supply in the buffer area affects adjacent areas;

• How the airflow of the whole machine operates when in standby;

• Whether local air supply needs to be independently controlled;

• How to link with the start and stop of equipment.

Partial protection on the equipment side can be combined with The structure of the EFU equipment-end fan filter unit is selected based on the buffer area 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.

Project judgment example

The wafers in the buffer area of ​​a certain project were exposed and the air supply was suspended during standby. After resuming production, it was discovered that there were particles on the wafer surface. The investigation confirmed that the particles settled during standby. Adjustment method: Maintain low-speed air supply during standby, and confirm the particle status before resuming. After adjustment, the wafer surface condition is stable.

Another project cache wafer is placed in a closed container, which is effectively sealed. After evaluation, it was confirmed that the air supply volume can be reduced during standby. Adjustment method: Set standby mode and verify wafer status based on container sealing and dwell time. After adjustment, the energy consumption is reduced and the wafer status is not affected.

These two situations illustrate that whether the buffer area requires continuous air supply depends on the exposure status, residence time and enclosure boundaries, and should be verified before deciding.

Key points for selection and acceptance inspection

Aili industrial equipment supporting support

Whether the wafer buffer area requires continuous air supply depends on the wafer exposure status, dwell time and enclosure boundaries. Aili Industrial has collaborative capabilities in fans, motors, filters, control systems and complete machine assembly links. It can check the air supply configuration, standby mode and linkage logic based on the exposure conditions of the cache area, equipment operation mode and recovery requirements, and help determine whether continuous air supply, low-speed operation or zone control is more suitable for the actual process, rather than cutting off the air supply across the board or running at full load all day.