How to avoid process exhaust during purification around etching equipment?

Etching processes are often accompanied by process exhaust, which may contain particles, corrosive gases, or other substances that require controlled emissions. If there is clean air supply around the equipment at the same time, the two sets of air flows need to be coordinated: the clean air supply cannot interfere with the exhaust gas collection, and the exhaust gas cannot bring pollutants into the clean air supply inlet.

Properly handling the relationship between clean air supply and process exhaust is a prerequisite for purifying the surroundings of etching equipment. The following will start from the following aspects: regional demarcation, air inlet position, air supply and exhaust balance and linkage status.

Distinguish between clean protection area and exhaust area

There are usually two types of areas around etching equipment:

• Clean protection zone: locations that require local cleanliness such as wafer transfer, loading and maintenance;

• Exhaust area: Locations where process exhaust, vacuum pump exhaust and maintenance exhaust need to be captured and discharged.

The airflow targets for the two types of areas are different. Clean air supply should protect sensitive locations, and exhaust should capture pollutants and discharge them. When designing, the boundaries between the two types of areas should be clearly defined first to avoid the two sets of airflows from interfering with each other.

When hazardous materials are involved, clean air supply cannot replace dedicated exhaust, isolation or safety protection. Related airflow planning can be referred to How to plan clean air supply for closed equipment cavities? , to understand the airflow organization inside the cavity.

The EFU air inlet position should avoid the influence of exhaust gas

The air inlet position of the EFU on the device side determines what air it inhales. If the air inlet is close to the exhaust outlet or exhaust diffusion area, pollutants may be sucked in and then sent into the protected area.

When selecting the air inlet location, you should confirm:

• Whether the air inlet is far away from the exhaust outlet;

• Whether the air inlet is downstream of the exhaust diffusion path;

• Whether there are local pollution sources around the air inlet;

• Whether independent air intake or pretreatment is required.

Use independent air sources when necessary rather than defaulting to nearby ambient air as suitable for recirculation. EFU configuration can refer to The EFU equipment-side fan filter unit selects a structure based on space and air inlet conditions.

Clean air supply should not interfere with exhaust gas capture

If the clean air blows to the exhaust collection area, the direction of the air flow may be changed, causing pollutants to escape or the collection efficiency to decrease.

During inspection, you should confirm:

• Whether the air supply direction points to the exhaust port;

• Whether the supply air forms a cross-flow in the exhaust collection area;

• Whether the air supply volume is too large, disturbing the exhaust airflow;

• Does the position of the exhaust trap need to be adjusted?

For the relationship between exhaust gas collection and clean air supply, please refer to What should I do if the cleanliness of the process equipment drops after it is started? , to understand the impact of exhaust changes on airflow.

Investigation of contamination back suction

Pollution backdraft means that the airflow in the exhaust area is re-inhaled into the clean air supply or inside the equipment. The symptom is that after the exhaust is started, the particles inside the equipment or in the protected area increase.

When judging, you should check:

• Changes in particles in the protection area before and after exhaust start;

• Whether the position of the EFU air inlet is affected by the exhaust;

• Whether the pressure difference inside the equipment changes;

• Whether the exhaust and supplementary air are balanced.

For troubleshooting ideas for contamination back suction, please refer to How to distinguish external and internal contamination when particles exceed the standard? , learn about source differentiation methods.

Air supply and exhaust balance and equipment pressure difference

The air supply and exhaust of etching equipment need to be balanced. If the exhaust volume is greater than the supply air volume, negative pressure may form inside the equipment, sucking in surrounding air from the gaps. If the clean air supply volume is too large, it may interfere with exhaust gas collection.

Need to confirm:

• Direction of pressure difference inside the equipment;

• Whether the exhaust volume and supplementary air volume are balanced;

• Is the pressure difference stable when switching exhaust air?

• Whether the air flow is controllable when the maintenance door is open.

For calculation of air volume balance, please refer to How to convert the clean area area into air supply demand? , understand the matching method of air supply volume and exhaust air volume.

Air supply and exhaust linkage requires clear signals

Exhaust switching will change the internal pressure of the equipment, and the linkage logic should be confirmed:

• How does the clean air supply respond when exhaust is started?

• How to deal with the equipment when there is an exhaust failure;

• How to switch air supply and exhaust under maintenance status;

• Alarm and handling procedures in abnormal situations.

The linkage logic should be specified in the plan rather than being temporarily adjusted on site. For instructions on control methods, 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.

Verification should cover running, standby and maintenance states

The verification of purification around etching equipment should cover different operating states:

• Normal operation: process exhaust and clean air supply operate at the same time;

• Standby state: the exhaust part is running or stopped;

• Maintenance status: The device is on and maintenance operations are in progress.

The airflow conditions are different in different states, and the verification results should be recorded separately. To determine the operating status of the equipment during acceptance, please refer to Which equipment should be in operation during acceptance?。

Project judgment example

After the exhaust of a certain etching equipment was started, the internal particles increased. The investigation found that the EFU air inlet was located downstream of the exhaust diffusion path, and pollution was inhaled. Adjustment method: Adjust the EFU air inlet position to keep it away from the exhaust influence range. The particles dropped after adjustment.

In another project, the clean air supply blows to the exhaust collection port, and the exhaust efficiency decreases. Adjustment method: Adjust the air supply direction and air volume to reduce interference with the exhaust air flow. After adjustment, the exhaust air collection returned to normal.

These two situations illustrate that the purification around the etching equipment must consider both cleanliness protection and exhaust gas capture to avoid the two sets of airflows from interfering with each other.

Key points for selection and acceptance inspection

Aili industrial equipment supporting support

Purification around etching equipment requires simultaneous treatment of two types of airflow: clean air supply and process exhaust. Aili Industrial has collaborative capabilities in fans, motors, filters, control systems and complete machine assembly. It can check the EFU air inlet position, air supply direction, air volume balance and linkage logic based on the exhaust position of the equipment, clean protection requirements and space conditions to help reduce pollution back suction and air flow interference. 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。