ISO 14644 Cleanroom Standards Explained: Classification, Requirements, Guide

1. Purpose

To establish and unify the internal understanding of cleanrooms and related controlled environments within the factory, clarify the core requirements and management principles of the ISO 14644 series of international standards, ensure all relevant personnel have a clear and consistent grasp of cleanliness classes, test methods, and continuous monitoring requirements, and provide a fundamental basis for the planning, operation, maintenance, and management of cleanrooms.

2. Scope

This specification applies to all cleanrooms, clean zones, and associated controlled environments designed, constructed, operated, maintained, and monitored in accordance with ISO 14644 standards within semiconductor high-tech factories. It covers all relevant engineering, operation and maintenance, production, and quality assurance personnel.

3. Definition and Core Principles of Cleanrooms

A cleanroom is defined as a room where the concentration of airborne suspended particles is controlled, and appropriate control is exercised over temperature, humidity, pressure, and other parameters to minimize the introduction, generation, and retention of particles indoors. All other internal parameters, such as air velocity and flow pattern, vibration, noise, illumination, and static electricity, are controlled as required.

Core control principles:

Supplying filtered air: Continuously deliver clean air into the room through High-Efficiency Particulate Air (HEPA) filters or Ultra-Low Penetration Air (ULPA) filters to dilute and remove contaminants generated indoors.

Air distribution: Adopt specific air flow patterns (e.g., unidirectional flow/turbulent flow) to ensure effective removal of contaminants.

Pressure difference control: Maintain positive or negative pressure in the cleanroom relative to adjacent areas to prevent pollution from entering through doors, windows, or gaps.

Material and personnel control: Implement strict purification procedures for materials, equipment, and personnel entering the cleanroom to control pollution sources.

4. Cleanliness Class Standards

ISO 14644-1 classifies cleanliness levels based on the concentration of airborne suspended particles. Levels are denoted as "ISO Class N," where N is an integer from 1 to 9. ISO Class 1 represents the cleanest environment, while ISO Class 9 is the least clean.

Key concepts:

Particle size thresholds: e.g., 0.1μm, 0.3μm, 0.5μm, 1.0μm, 5.0μm. Class definitions are based on one or more selected particle sizes.

Maximum allowable concentration limits: Each class corresponds to maximum concentration limits for particles of different sizes (unit: particles/m³).

• 4.1 ISO 14644-1: Cleanliness Classification

Defines the classification standard for airborne particle concentrations, adopting a dual-system (imperial: particles ≥0.1μm per cubic foot; metric: particles ≥0.1μm per cubic meter).

Typical applications in the semiconductor industry:

Class 1: ISO Class 1 (≤35.2 particles/m³)

Class 10: ISO Class 2 (≤352 particles/m³)

Class 100: ISO Class 3 (≤3,520 particles/m³)

Class 1,000: ISO Class 4 (≤35,200 particles/m³)

Dynamic monitoring requirements: Real-time particle concentration monitoring in critical areas, with automatic alarms triggered when exceeding limits.

• 4.2 ISO 14644-2: Monitoring Specifications

Specifies cleanroom test methods, monitoring frequencies, data recording, and reporting requirements.

Key requirements:

Calculation of sampling points: N = A^0.5 (where A is the area)

Sampling volume: ≥1L per point, sampling time ≥1 minute

Monitoring frequency: Once per shift for production areas; once per week for non-production areas

• 4.3 ISO 14644-3: Design and Construction Specifications

Core requirements:

Air tightness: All gaps ≤0.5mm, sealed with specialized sealants

Material selection: Wall/ceiling color steel plate thickness ≥50mm; epoxy resin floor thickness ≥3mm

Pressure difference control: ≥10Pa between clean and non-clean areas; ≥5Pa between areas of different cleanliness classes

Air distribution: Unidirectional flow cleanrooms: air velocity 0.36-0.54m/s; non-unidirectional flow cleanrooms: air change rate ≥15 times/hour

• 4.4 ISO 14644-4: Equipment Specifications

Filtration system: HEPA filter efficiency ≥99.99% @0.3μm; ULPA filter efficiency ≥99.9995% @0.12μm

Temperature and humidity control: Temperature 22±1℃, humidity 45±5%RH (semiconductor lithography areas)

Vibration control: Vibration velocity ≤0.5mm/s in precision equipment areas

5. Key Test and Monitoring Methods

To verify and maintain cleanliness classes, the following critical tests must be performed:

Particle concentration testing: Measured at designated sampling points using a discrete particle counter (core method for verifying cleanliness classes).

Air flow testing: Includes air velocity testing (for unidirectional flow) and air volume testing (for non-unidirectional flow) to ensure sufficient air displacement capacity.

Pressure difference testing: Measures static pressure difference between the cleanroom and adjacent areas to ensure correct air flow direction.

Filter leak testing: Scans HEPA/ULPA filters and their frames to ensure no leakage.

Air flow pattern testing: Visualizes or measures air flow direction and uniformity to evaluate contaminant removal efficiency.

Temperature and humidity testing: Monitors and records environmental temperature and relative humidity to meet process requirements.

Recovery time testing: Evaluates the time required for the cleanroom to recover to the specified cleanliness level from a contaminated state.

6. Basic Operational and Maintenance Requirements

Personnel specifications: All personnel must undergo strict training and comply with cleanroom dress codes (cleanroom suits, gloves, masks, etc.) and behavioral norms.

Cleaning procedures: Establish a regular cleaning plan using specialized tools and reagents to clean surfaces and equipment.

Material access: All materials entering the cleanroom must go through cleaning and air lock transfer procedures.

Preventive maintenance: Perform regular preventive maintenance and replacement of HVAC and purification systems (MAU, FFU, DC, filters, etc.).

Continuous monitoring: Conduct real-time or frequent monitoring of key parameters (particle count, pressure difference, temperature and humidity) and set alarm limits.

Documentation and records: Maintain all test reports, monitoring data, maintenance records, and deviation handling reports to demonstrate continuous compliance.

7. Responsibilities

All personnel entering and working in the cleanroom are responsible for understanding and complying with the principles and regulations outlined in this basic understanding document. The facility management department is responsible for verifying facility compliance and conducting continuous monitoring, while the production department is responsible for maintaining cleanliness during daily operations.

8. Review and Update

This basic understanding document will be reviewed regularly or revised in response to updates to ISO standards and changes in factory process requirements to ensure its accuracy and applicability.

Suzhou Pharma Machinery Co.,Ltd.

2026/02/11

Gino