How to configure EFU of lithography equipment? Key points of local cleaning, air flow stabilization and space interface

Direct answer: Lithography equipment EFUs should be configured around the areas inside the equipment that really need protection. First confirm the transmission path of the wafer from entering the equipment to leaving the equipment, then identify possible particle risks caused by door opening, mechanical movement, personnel maintenance and equipment exhaust, and finally determine the location of the EFU, effective air supply range, air volume, static pressure, filtration efficiency and control method.

Lithography equipment usually has high requirements on particle control, air flow stability and internal space of the equipment. EFU configuration cannot only depend on how many units can be installed on the top of the equipment, nor can it be applied only according to a fixed wind speed. A suitable solution should allow clean air to cover sensitive areas while avoiding high-velocity airflow, localized vortices or equipment pressure changes that interfere with normal operation.

What problems should the lithography equipment EFU solve first?

Lithography equipment uses EFU, usually not to obtain the exact same cleanliness level inside the entire equipment, but to continuously protect specific areas.

These areas may include:

• The temporary storage location after the wafer enters the equipment;

• Wafer transfer and robot activity areas;

• Locate, align or detect areas of interest;

• Where wafers are handed off between different modules;

• Areas near external openings that are easily affected by ambient air;

• Spaces that need to be quickly restored to a clean state after maintenance.

Therefore, the most important task before configuring EFU is not to select a model, but to answer three questions:

1. Which areas require direct coverage of clean air?

2. Where might particles enter or originate?

3. Where should the air enter and where should it leave?

These three issues determine the installation location, air supply direction and actual air volume of the EFU.

Design from the wafer path, not the device shape

If the EFUs are arranged evenly only based on the top area of ​​the equipment, there may be a situation where there are a large number of EFUs, but there are still low-speed areas or reflow areas at key locations.

A more reasonable approach is to check along the wafer path:

Loading position → Transfer area → Positioning or detection area → Process interface → Return or unloading area

The pollution risks that need to be paid attention to in each link are different. For example, the opening position of the equipment may be disturbed by external air, periodic air flow changes may occur in the robot movement area, and the equipment frame and cables may block the vertical air supply.

The EFU layout should try to allow the filtered air to reach the sensitive area first, and then enter the return air outlet or exhaust area along the predetermined path to avoid contaminated air passing through key locations first.

How should local clean areas be divided?

The interior of the lithography equipment can be divided into three areas according to the importance of airflow protection:

core protected areas

Areas directly involved in wafer exposure, transport, positioning, or inspection. Here you need to focus on checking the air supply coverage, wind speed stability and particle status.

transition zone

The area connecting the core protection zone to equipment openings, mechanical structures or other functional modules. Its function is to reduce the impact of external air and internal equipment pollution on the core area.

indirect protected areas

Electrical, drive or auxiliary spaces with relatively low requirements for local particle control. Such areas do not necessarily need to use the same air supply volume as the core area, but air must be prevented from entering the critical area in the opposite direction.

This zoning method can avoid using the same wind speed in all locations and also facilitates the determination of the number of EFUs and different operating gears.

EFU air volume cannot be calculated only based on the volume of the equipment

Ordinary ventilation projects often estimate air volume based on the number of air changes, but local clean air supply for lithography equipment pays more attention to the airflow coverage, direction and stability of sensitive areas. Calculation based only on the internal volume of the equipment may not reflect mechanical structure obstruction and local pollution sources.

The preliminary design can start from the effective air supply area and target average wind speed:

Target air volume = effective air supply area × target average wind speed

Among them, the effective air supply area should be deducted from filter frames, equipment beams, guards and other obstructions.

After completing the preliminary estimate, it needs to be revised based on the following factors:

• Whether there is enough clearance on the air inlet side of the EFU;

• The resistance of the filter at the target air volume;

• Local resistance caused by the internal structure of the equipment;

• Whether the movement of the manipulator changes the airflow;

• The location of return air vents and exhaust vents;

• Whether there is overlapping airflow between multiple EFUs;

• Pressure changes under different operating conditions of the equipment.

The final air volume should be confirmed by testing a prototype or first equipment close to the real structure.

Why lithography equipment pays more attention to air flow stability

The airflow in lithography equipment must not only be clean, but also need to be as stable as possible. If the wind speed changes significantly over time, or there is significant local backflow, particles that have settled or adhered inside the equipment may re-enter the air.

Common factors that affect airflow stability include:

• Fan speed fluctuation;

• The resistance at different positions of the filter is inconsistent;

• The distance between the fan and filter is too small;

• The equipment beam blocks the air outlet surface;

• The speed settings of multiple EFUs are inconsistent;

• The manipulator moves at high speed;

• Opening and closing of equipment doors or maintenance covers;

• Changes in air volume in the exhaust system;

• Start and stop adjacent function modules.

Therefore, EFU debugging of lithography equipment cannot only measure the average wind speed once, but also needs to observe changes in different equipment states.

Where should wind speed uniformity be measured?

The uniform air outlet surface of the EFU does not mean that the air flow at the location of the wafer must be uniform. Equipment structures may create obstructions, shunts, or vortices beneath the filter.

It is recommended to set up two levels of measurement:

EFU air outlet measurement

Used to determine the wind speed distribution of the EFU itself. The measuring points should be arranged according to the grid agreed by both parties, and the average, maximum and minimum values ​​should be recorded.

Measurement of critical process areas

Set measuring points near the wafer transfer, positioning or inspection positions to confirm the actual air flow status after the equipment is assembled.

If the air outlet data is normal, but low-speed or reverse airflow exists in key areas, priority should be given to checking the internal occlusion, return air position and exhaust impact of the equipment instead of directly increasing the speed of all EFUs.

How to avoid 'The air volume is enough but the effect is not good'

In lithography equipment EFU projects, the following problems are more common than simply insufficient air volume:

When solving this type of problem, you should first locate the location of abnormal air flow and the corresponding working conditions, and then adjust the structure or control parameters. Directly increasing the speed of all EFUs may increase energy consumption and noise, but it cannot eliminate local eddy currents.

How to configure when there is insufficient installation space

Lithography-related equipment often requires EFUs to be arranged within a limited height while avoiding mechanical structures, electrical modules and pipelines. At this time, you can't just check whether the EFU can be put in, but also check the air inlet and maintenance space.

The space interface includes at least:

• EFU can use length, width and height;

• Air inlet conditions from the top or sides of the equipment;

• The distance between the fan suction inlet and the equipment guard;

• Installation hole locations and support structures;

• Filter replacement direction;

• Fan, motor and controller maintenance directions;

• Location of power supply and communication interface;

• Fixing requirements for equipment hoisting and transportation.

When the installation height is limited, it can be evaluatedAili Industrial 70mm ultra-thin EFU . 70mm is the overall height of the corresponding product, but whether it can be used ultimately depends on the target air volume, system static pressure, filter size, air inlet clearance and maintenance conditions.

If the equipment opening has a long and narrow shape or the installation interface is special, it is necessary to design a small size, narrow body or non-standard EFU according to the drawings instead of scaling down the conventional product.

How to choose filter efficiency

The lithography equipment EFU can be configured with corresponding levels of high-efficiency or ultra-high-efficiency filters according to the project particle control objectives. The filter grade should be determined by equipment process requirements, customer specifications and acceptance methods, and cannot be directly specified based on industry name alone.

Filtering configuration requires synchronization confirmation:

• Target particle control requirements;

• Filter efficiency rating;

• Rated air volume and initial resistance;

• Effective filter area;

• The sealing method between the box and the filter;

• Whether on-site leak detection is required;

• Leak detection location and operating space;

• Allowable running resistance;

• Filter replacement directions.

As the efficiency level increases, the filter resistance, fan operating point and effective air volume may change. Therefore, the filter and fan must be matched as a complete system.

Will ultra-thin structure affect EFU performance?

Ultra-thin EFU can reduce the installation height of the equipment, but the internal space is more compact, and the matching requirements for fans, motors, filters and air flow channels are also higher.

Ultra-thin solutions require key verification:

• Whether the required static pressure can be provided under the target air volume;

• Whether the fan suction inlet is restricted;

• Whether the wind speed on the air outlet surface is uniform;

• The temperature rise of the motor and controller during continuous operation;

• Noise and vibration at target speed;

• Adjustment margin after filter resistance changes;

• Whether parts can be disassembled and assembled from the intended direction.

Ultra-thin does not mean low air volume, nor does it mean that the air inlet space can be ignored. The final performance should be based on the test results of the complete EFU under the agreed working conditions.

How to avoid mutual interference between multiple EFUs

When one device is configured with multiple EFUs, the position, spacing, rotation speed and control logic should be uniformly considered.

Multiple EFUs can use the following configuration ideas:

• Divide control zones according to clean areas;

• The same functional area uses the same basic rotation speed;

• Make local corrections to locations where structure occlusion is obvious;

• The operating gears are set respectively for production, standby and maintenance states;

• Record the address, location and setting value of each EFU;

• Preset safe operating status when communication is abnormal;

• Series equipment follows proven parameters.

It is not necessarily reasonable for multiple EFUs to have exactly the same speed. If the internal resistance or occlusion of the equipment is different, it needs to be balanced based on the actual measurement results in the critical areas.

How EFU is linked with lithography equipment

Lithography equipment may have multiple states such as production, standby, door opening, maintenance, and abnormality. EFU can set the corresponding operating mode according to the project control logic.

For example:

• The equipment operates according to the proven working gear during production;

• Maintain a duty position that satisfies cleanliness conditions when on standby;

• Switch to the corresponding operating mode when opening the door or transferring materials;

• Use the clean recovery gear after equipment maintenance;

• Adjust the rotation speed after the filter resistance changes;

• When the EFU fails, it feeds back the status to the equipment control system;

• When communication is interrupted, the preset speed is maintained or the agreed logic is executed.

The control method can be selected according to the equipment requirements: multi-speed, 0-10V, PWM or RS485 communication. Before formal finalization, start and stop authority, speed range, status feedback and exception handling rules should be clarified.

How should EFU of lithography equipment be verified?

Instead of only conducting a factory air volume test once, a more suitable method for lithography equipment is to establish a verification matrix based on equipment status.

The specific test methods, measuring points and judgment standards should be jointly determined by the equipment party, process requirements and agreement between both parties.

How Aili Industry cooperates with the lithography equipment EFU project

The design focus of the lithography equipment EFU is 'whether critical areas can obtain stable and clean air', rather than pursuing a larger rated air volume alone. During project evaluation, Aili Industrial can assist in determining the EFU installation area, air volume and static pressure, filtration configuration and control method based on the wafer path, equipment openings, structural shielding and return air position.

Aili Industrial carries out supporting R&D and production around the motors, fans, control systems, sheet metal structures, air filters and complete machine assembly required for EFU. For ultra-thin, small size, narrow body or special interface requirements common in lithography equipment, structure, air performance and control parameters can be coordinated in the same project.

The prototype stage can verify the outlet wind speed, key area airflow, operating power, noise, vibration and continuous operating temperature rise based on actual equipment or simulated structures. After completing the first unit verification, the product drawings, filter specifications, control parameters and acceptance conditions will be solidified to help maintain consistent configurations of subsequent batches of equipment.

Available atView different device-side EFU structures in the Aili Industrial EFU product category catalog ; when the installation height is restricted, you can learn more70mm ultra-thin EFU ; special size, air inlet direction and equipment interface can be passedCustomized EFU for matching.

FAQ

Is the higher the wind speed of the EFU of the lithography equipment, the better?

no. Excessively high wind speeds may increase noise, energy consumption and local turbulence. It should be determined based on the airflow coverage, direction and stability of the sensitive area, rather than simply pursuing a higher value.

Does lithography equipment have to use ultra-thin EFU?

uncertain. Only when the equipment installation height is limited, the structural advantages of ultra-thin EFU are more obvious. When space is sufficient, conventional EFU can also be selected based on air volume, static pressure and maintenance conditions.

The wind speed on the air outlet surface is uniform, why is there still a low-speed zone inside the equipment?

It may be due to equipment beams, manipulators, shields or cable obstructions, or it may be related to the location of return air and exhaust air. Airflow should be retested in critical areas rather than just the EFU outlet surface.

Do multiple EFUs have to use the same speed?

uncertain. Unified basic parameters can be used in the same area and similar resistance conditions; if the occlusion and system resistance at different locations are different, balance should be based on actual measurement results.

Which filter efficiency should be chosen for lithography equipment EFU?

Should be determined based on equipment process, particle control objectives, customer specifications and acceptance methods. After the filtration efficiency is improved, the resistance, air volume and fan operating point must be rechecked.

Does EFU only need to be tested once after installation?

The first device should undergo detailed verification. When the equipment structure, filter specifications, control parameters or exhaust conditions change, the affected air volume and airflow status should be rechecked.

in conclusion

The core of the EFU configuration of lithography equipment is to identify the areas that need protection along the wafer path, and establish with a clear source of clean air, stable flow direction, measurable key positions, and linkable equipment status .a local airflow system

When selecting, priority should be given to confirming the pollution path, sensitive areas and equipment space, and then determining the number of EFUs, installation location, air volume and static pressure, filtration efficiency and control method. For ultra-thin, small-sized or complex shielding structures, closed-loop verification should be carried out through prototype and first equipment testing to avoid completing the configuration based only on the rated air volume or the top area of ​​the equipment.