Different industries should select appropriate cleanliness levels based on their process requirements. For example:
• Semiconductor/Microelectronics Cleanrooms: ISO 4-6.
• Electronics and Lithium Battery Production: ISO 7-8.
• Pharmaceutical Industry: Commonly requires ISO 5-8.
• Food Industry: ISO 6-8.
• Biomedical: ISO 7-8.
• Hospitaloperating theaters: ISO 5-8.
• Biological Laboratories: ISO 7-8.
Semiconductor manufacturing requires highly controlled clean environments. Cleanliness levels vary depending on the specific semiconductor process requirements:
• Cutting, Grinding, and Polishing Processes: ISO 5-7.
• Lithography Area: ISO 4-5.
• Deposition/Echning and Cleaning Rooms: ISO 5-6.
• Packaging Area: ISO 6-7.
• Testing Workshop: ISO 7-8.
Semiconductor cleanrooms mainly include unidirectional flow and non-unidirectional flow. Unidirectional flow is used in areas requiring ISO 5 and above, such as critical processes like cutting, grinding, lithography, and deposition/etching, whereas non-unidirectional flow is used in areas with ISO 6 and below, such as packaging and testing workshops.
Particle control is critical in semiconductor cleanrooms as airborne particles can directlyaffect product quality and yield. During manufacturing, particles in the air can cause significant defects in semiconductor products. For instance, the defect density in chips is closely tied to the number of particles in the air, as particles can lead to errors during lithography and ultimately cause circuit short-circuits or open circuits. Therefore, particle control is essential for maintaining chip yield and quality.
FFUis essential in semiconductor cleanrooms due tosemiconductor’s high cleanliness requirements, especially for areas requiring strict airborne particle control. With modular designs and flexible installation, FFU can be configured with HEPA or ULPA filters to meet strict cleanliness standards in semiconductor production.In addition,FFU can be arranged above clean zones or integrated with equipment to supply clean air evenly across the operation area, ensuring product quality and production efficiency.
Static electricity has a significant impact on semiconductor chip production and quality. To control static in clean areas:
• Set corresponding humidity levels in diffferent areas and keep them stable (as humidity significantly affects static build-up).
• Use anti-static materials in room finishes (especially floors with anti-static properties, as floors are the main source of static electricity accumulation)
• Establish grounding systems for personnel, equipment, and floors, and employ ionization devices in specific work areas. Staff should also wear anti-static clothing and shoes to further minimize static pollution.
Temperature and humidity in semiconductor workshops directly affect product stability and reliability. Generally, the temperature in semiconductor cleanrooms should be strictly controlled within 20-24℃, with relative humidity maintained between 40-60%, with fluctuations not exceeding±1℃ for temperature and±5% RH for humidity. Some special processes, such as lithography exposure, may require tighter control, with temperature fluctuations within±0.5℃ and humidity fluctuations within±3% RH.
In semiconductor cleanrooms, non-dust-generating, easy-to-clean materials are normally selected to reduce particle contamination.
Walls and Ceilings: Sandwich Panel (with good dust-proof, moisture-proof, and anti-static performance), stainless steel plates, and tempered/organic glass.
Flooring: anti-static PVC flooring (easy to clean and maintain) and epoxy resin floors (seamless, dust-resistant, aesthetically pleasing, and easy to clean).
Structural Gaps are sealed with silicone or rubber gaskets to ensure air-tightness within the cleanroom, preventing the entry of external contaminants.
Chemical pollution in semiconductor cleanrooms mainly comes from organic solvents, specialized gases, photoresists, and cleaning solvents. Common treatment methods include:
• Adsorption: Using porous solid adsorbents like activated carbon to capture harmful substances.
• Condensation: Lowering waste gas temperatures to condense harmful substances into liquid or solid form for separation.
• Plasma Technology: Using high-energy plasma to oxidize gaseous pollutants into harmless substances.
• Catalytic Combustion: Oxidizing organic compounds at lower temperatures with a catalyst to produce CO2 and water. HEPA filters can also be installed in the exhaust system to remove particles and harmful gases from the air effectively.
The semiconductor cleanroom certification process includes several steps:
Preparation: Define the testing objectives, scope, and standards; Prepare the necessary testing equipment and consumables.
Site Inspection: Conduct a comprehensive survey of the cleanroom’s layout, and understand the airflow organization, filtration system, etc.
Environmental Parameter Measurement: Use particle counters, anemometers, temperature and humidity meters, and other equipment to measure dust particle concentration, air velocity, temperature, humidity, differential pressure, lighting, and noise in the cleanroom.
Data Analysis and Evaluation: Compare the collected data with the target cleanliness level and standards to assess the cleanroom’s overall performance and make a testing report.
Rectification and Reinspection: Address any issues identified during testing, provide improvement recommendations, and oversee implementation, then conduct a reinspection to ensure the cleanroom meets standards.
Regular maintenance for semiconductor cleanrooms involves:
• Filter Inspection and Replacement: Routine cleaning and replacement of filters vary based on the environment. It is suggested that pre-filters are cleaned monthly, medium filters replaced every three months, and HEPA filters replaced annually (or when filter resistance reaches twice its initial value).
• HVAC Equipment Maintenance: Periodic inspections and maintenance of HVAC components like fans, heat exchangers, humidifiers, and motors to ensure proper function, conducted at least twice a year.
• Calibration of Monitoring Equipment: Routine calibration of sensors for temperature, humidity, and pressure, with calibration records kept.
• General Cleaning and Supervision: Regular cleaning and maintenance of walls, ceilings, and floors, ensuring compliance with cleanliness standards.
To manage the pressure differential in semiconductor cleanroom, determining the pressure differential requirements for each area based on design specifications and production process requirements, and calculating the air volume required to control the pressure differential is the prerequisite. Constant Air Volume (CAV) or Variable Air Volume (VAV) systems adjust the supply and exhaust air volumes to maintain desired pressure levels. Differential pressure sensors monitor real-time pressure changes, and signals are sent to control systems to adjust and stabilize pressure. Airlocks or buffer rooms with interlocking doors at cleanroom entrances or between rooms of different cleanliness levels further help maintain cleanliness and pressure stability. Regular checks and record-keeping are essential to identify and resolve any issues promptly.