How does a wafer inspection platform balance cleanliness and low vibration?

Wafer inspection platforms are sensitive to both particles and vibration. Particles can cause surface defects and vibrations can affect measurement accuracy. While clean air supply protects the wafer, it also causes air flow disturbance and fan vibration. Both types of impacts need to be checked at the same time. You cannot just look at cleanliness or just noise.

Balancing cleanliness with low vibration requires consideration of measurement limitations, airflow layout and fan installation.

First clarify the measurement limitations and sensitive conditions

Different detection equipment has different sensitivity to vibration and air flow. Before configuration, you should confirm:

• The sensitivity range of the instrument to vibration frequency and amplitude;

• The degree of influence of airflow on measurement results;

• Measure position and height;

• Exposure status of wafer and platform during inspection;

• Movements and heat sources in equipment operation.

Only by writing these conditions clearly can we judge whether the clean air supply solution will interfere with the detection. Exposure protection requirements for wafer inspection, please refer to How can wafer handling stations reduce dust during exposure? , understand the protection considerations for exposed links.

Airflow disturbances can affect measurement stability

The air flow generated by clean air supply may cause disturbance to the measurement:

• The air flow directly acts on the measurement area, causing slight displacement or vibration;

• Unstable airflow causing local temperature or refractive changes;

• Airflow brings particles close to the optical element;

• Air flow interacts with platform motion to affect measurement repeatability.

The airflow layout should avoid blowing directly into the measurement area while maintaining protection of the wafer surface. For local protection methods of the detection platform, please refer to How does EFEM internal clean protection cover the wafer transfer path? , understand the relationship between path protection and airflow organization.

Wind turbine vibrations may be transmitted through the structure

The vibration of the air supply equipment may be transmitted to the detection platform through the bracket, ceiling or connecting structure. The vibration transmission path is related to the installation method and is not necessarily limited to the vicinity of the equipment.

During inspection, you should confirm:

• Whether the fan is installed on an independent support;

• Whether the connecting structure transmits vibration;

• Whether ducts and connections introduce vibration;

• Whether the platform is isolated from the source of vibration.

For vibration transmission control ideas, please refer to Will stacking items on the workbench create a pollution dead zone? Although the objects are different, the structural factors need to be checked together.

Fan operating point and noise are not the only indicators

When selecting air supply equipment, don’t just rely on low noise or low speed to determine whether it is suitable for precision measurement. The fan may have lower noise at low speeds, but the vibration characteristics may not meet the requirements.

Should check:

• The vibration performance of the fan at the target operating point;

• The vibration reduction effect of the installation method;

• Matching of air supply volume and filter resistance;

• Stability under long-term operation.

For the selection of working points of air supply equipment, please refer to Why should we look at the complete performance curve when selecting FFU? , understand the method of determining the target operating point. For the influence of static pressure outside the machine, please refer to What does FFU external static pressure mean?。

The relationship between airflow layout and detection position

The airflow layout should be adjusted according to the detection location:

• The air supply direction should avoid facing the measurement area;

• The air supply distance and speed are controlled within an appropriate range;

• Add local diversion or shielding structures if necessary;

• The return air path avoids disturbances in the measurement area.

The influence of air supply distance on air flow can be referred to How will the airflow change when the air supply distance increases? , understand the relationship between distance, speed and direction. For the influence of supply air vortex, please refer to How does supply air vortex affect open workstations?。

Joint verification of cleanliness and detection stability

Validation should cover both cleanliness and detection stability:

• Measure particles while the purification equipment is in operation;

• Measure vibration and check repeatability under the same conditions;

• Compare results under different operating settings;

• Covers actual detection work speed.

Measuring only particles or only measuring vibration cannot indicate whether the solution is suitable for the detection platform. To determine the operating status of the equipment during acceptance, please refer to Which equipment should be in operation during acceptance?。

Air supply configuration and filtration level

The local protection of the detection platform 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. Aili Industrial has collaborative capabilities in the assembly of fans, motors, filters and complete machines. It can combine the space conditions, air supply requirements and vibration requirements of the detection platform to check the equipment working point, installation method and air supply direction, helping to consider cleanliness protection and detection stability together, rather than judging only by noise or speed.

→ Understand relevant product parameters → Confirm equipment supporting conditions

Project judgment example

The particles on a certain testing platform are qualified, but the measurement data drifts. The investigation found that the supply air flow directly affects the measurement area. Adjustment method: adjust the air supply direction, add a diversion structure, and avoid the measurement position. After adjustment, the measurement stability is improved and the particles still meet the requirements.

Another project involved fan vibrations being transmitted to the platform through the brackets. Adjustment method: Move the fan to an independent support, add vibration reduction measures, and check the air supply volume. After adjustment, the vibration decreased and the air supply coverage still met the requirements.

These two situations illustrate that the cleanliness protection of the detection platform needs to be checked together with vibration control and airflow layout, and selection cannot be based on a single indicator.

Key points for selection and acceptance inspection