The technical applications of FFU Fan Filter Units in the semiconductor industry are extreme and indispensable. Semiconductor manufacturing represents the pinnacle of industrial cleanliness, with environmental requirements stringent at the atomic level, and FFUs are the core infrastructure that enables such an environment. Below is a detailed analysis of the in-depth and specific technical applications of FFUs in the semiconductor industry:
I. Environmental Requirements of Semiconductor Manufacturing: Why FFU is a Must-Have?
The production of semiconductor chips (especially those with nanoscale processes) has extremely demanding environmental requirements, where even the slightest deviation can lead to substantial losses.
1. Ultra-Fine Particle Control: A particle smaller than a virus (e.g., 0.05μm) landing on a wafer can cause short circuits or open circuits in dozens of chips, directly leading to a drastic drop in yield.
2. Molecular-Level Contamination (AMC) Control: Trace amounts of metal ions such as boron, phosphorus, sodium, and organic compounds (AMC) in the air can contaminate the silicon wafer, altering its electrical properties and causing inconsistent or failed product performance.
3. Electrostatic Discharge (ESD) Control: Static electricity can attract particles, and discharges can damage circuits with nanoscale linewidths.
4. Ultra-Stable Environment: Processes such as photolithography are extremely sensitive to fluctuations in temperature, humidity, and airflow. Even minor changes can affect overlay (alignment precision) and CD (critical dimension).
5. Continuous Large-Scale Production: Semiconductor fabs operate 24/7, requiring absolute reliability from environmental control systems, with maintenance not affecting production.
II. Core Technical Roles of FFU in Semiconductor Factories
In response to the above requirements, FFUs play the following key roles in semiconductor factories:
1. Creating and Maintaining Ultra-High Cleanliness Vertical Unidirectional Flow
- Application: In the core areas of the entire chip factory (especially where wafers are exposed), FFUs are installed at a high coverage rate (usually ≥80%) on the ceiling, forming a "piston-like" laminar flow from top to bottom.
- Technical Value: This uniform and stable airflow continuously and quickly "presses" down particles generated by personnel and equipment towards the floor return air vents, significantly reducing the particles' dwell time in the air and preventing their lateral diffusion and deposition on the wafer surface. This is the most effective means of controlling particulate contamination.
2. Achieving ISO 1-5 Cleanliness Levels
- Application: Key process areas such as lithography, etching, and thin-film zones for advanced processes (e.g., 5nm, 3nm).
- Technical Realization: ULPA (Ultra-Low Particulate Air) filters (with an efficiency of ≥99.9995% for 0.12μm particles) are used instead of ordinary HEPA filters. FFUs themselves adopt a zero-leakage sealing design (such as liquid gasket sealing, high-quality gel sealing) to ensure that unfiltered air cannot bypass the filters.
3. Serving as a Platform for Chemical Filtration
- Application: Chemical filters are installed before the ULPA filters, forming a combination of "chemical + physical filtration."
- Technical Value: Chemical filters (usually impregnated activated carbon or high surface area adsorbent materials) are specifically designed to adsorb and remove specific airborne molecular contaminants (AMC), such as acidic gases (SOx, NOx), alkaline gases (NH₃), dopants (B, P), and condensable organics, protecting wafers from chemical contamination.
4. First Line of Defense Against Electrostatic Discharge (ESD)
- Application: The diffuser plates and casing structures of FFUs are made of or treated with anti-static materials.
- Technical Value: Preventing the generation of static electricity due to airflow friction with the casing during FFU operation, thus avoiding it from becoming a source of particle attraction or ESD events.
5. Providing Stable and Reliable Environmental Assurance
- Application: Thousands of FFUs work in coordination through an intelligent group control system.
- Technical Value:
- High-Precision Speed Control: EC motors ensure highly stable airflow from each FFU, maintaining uniform and stable airflow organization across the entire area.
- Modular Design: The failure of one or several FFUs does not affect the overall system, ensuring high reliability.
- Predictive Maintenance: The intelligent system can monitor the operating status, airflow speed, and pressure difference (indicating filter blockage) of each FFU in real-time, enabling predictive maintenance and avoiding unplanned downtime.
III. Special Technical Considerations for FFU Selection in the Semiconductor Industry
When selecting FFUs for the semiconductor industry, more stringent requirements must be proposed on top of general standards:
1. Filter Efficiency: ULPA level (U15 and above) is a must, and even higher efficiency for 0.05μm particles may be required.
2. External Static Pressure: Extremely high (usually ≥150 Pa) to overcome the additional resistance of chemical filters and ensure stable airflow throughout the lifecycle.
3. Airflow Uniformity: Extremely strict (within ±5%). Any airflow non-uniformity can create vortices, leading to particle retention.
4. Motor and Vibration: Low-vibration EC motors must be used to prevent micro-vibrations from affecting the alignment and imaging accuracy of lithography machines.
5. Material and Structure: Casings are typically made of stainless steel (SUS304) or high-quality galvanized steel, with anti-static coating on the surface. All structures must be robust, with no risk of particle shedding.
6. Sealing: Zero leakage, with each unit undergoing strict PAO/DOP scan leak testing at the factory.
7. Control and Integration: Must support high-precision group control (e.g., via RS-485) and seamless integration into the Fab's facility monitoring system (FMCS) for data acquisition and remote control.
8. Optional Configuration: Space and interfaces for chemical filter installation should be reserved.
IV. Typical Application Scenarios
1. Lithography Bay:
- Requirements: Highest cleanliness level in the factory (ISO 1-3), ultra-stable temperature and humidity, ultra-low vibration.
- Role of FFU: Provide the purest and most stable unidirectional flow to protect the multi-million-dollar lithography machine lenses and exposed photoresist wafers from any contamination.
2. Etch & Implant Bay:
- Requirements: High cleanliness and control of specific AMC.
- Role of FFU: While providing ULPA filtration, it may also carry specific types of chemical filters to remove acidic or dopant gas molecules generated during the process.
3. Diffusion Bay:
- Requirements: Many high-temperature devices, need to control thermal convection and particles.
- Role of FFU: The powerful unidirectional flow can effectively suppress the thermal plume from the equipment, preventing hot air from carrying particles upward and contaminating other areas.
Summary:
In the semiconductor industry, FFUs have far exceeded the scope of a simple "ventilation device." They are:
1. The Guardian of Yield: Directly determining the yield of chip manufacturing.
2. Enabling Technology for Advanced Processes: Without the ultra-clean environment created by FFUs, nanoscale processes would not be possible.
3. The Nerve Endings of a Smart Factory: Tens of thousands of FFUs, as distributed nodes interconnected through an intelligent network, form the solid foundation of environmental control in a semiconductor fab.
The core of their technical application lies in meeting the highest standards of human cutting-edge manufacturing with extreme performance, impeccable reliability, and high intelligence. Therefore, FFUs in the semiconductor industry represent the highest and strictest technical specifications in this field.
