As the core equipment in semiconductor manufacturing, the components of a lithography machine have nanometer - level precision. Any slight contamination can lead to lithography pattern distortion, exposure energy deviation, and even equipment failure. Therefore, component cleaning is a crucial step in ensuring the performance of the lithography machine, and refined solutions need to be developed according to the characteristics of different components.

### I. Core Contamination Risks and Challenges of Lithography Machines

#### 1. Types and Hazards of Contaminants

 - **Particle Contaminants**: These come from air dust and mechanical wear (such as guide rail lubricant particles). They may block the light path or get stuck in the gaps of precision moving parts, resulting in focusing errors.

 - **Organic Residues**: These include photoresist volatiles, vacuum pump oil vapors, and fingerprint grease from operators. They can contaminate the surfaces of optical elements, causing laser scattering or chemical reaction corrosion.

 - **Metal Ions**: Al³⁺ generated from the oxidation of cavity materials (such as aluminum alloy), or Fe²⁺ introduced by cleaning tools may adsorb on the surface of the optical coating, affecting the reflectivity.

 - **Chemical Residues**: Acid/alkali solutions that are not completely removed after cleaning may corrode components (such as stainless - steel vacuum chambers) over time.

#### 2. Cleaning Difficulties

 - **Sensitivity of Optical Elements**: The surface roughness of the reflectors in extreme ultraviolet (EUV) lithography machines needs to be controlled below 0.1nm. Traditional cleaning methods may cause scratches or damage to the coating.

 - **Complexity of Moving Parts**: Micro - mechanical structures such as nanometer - scale guide rails and bearings are prone to dirt accumulation, and conventional methods are difficult to clean thoroughly.

 - **Material Compatibility Limitations**: Special materials such as silicon carbide ceramics and ultra - low expansion glass (ULE) need to avoid chemical corrosion.

### II. Cleaning Technologies and Solutions for Key Components

#### 1. Optical System Cleaning

 - **(1) Reflectors and Lenses**

    - **Dry Cleaning - dominated**:

        - **Ultra - pure Nitrogen Blowing**: Use high - purity nitrogen (99.999%) with a filtration accuracy of 0.003μm to blow the surface to remove visible particles.

        - **Ionized Air Cleaning**: Generate positive and negative ions through corona discharge to neutralize the static electricity of particles, making them detach from the surface. This is suitable for non - conductive coatings (such as Mo/Si multi - layer films).

    - **Wet Cleaning - assisted**:

        - **Megasonic Mist Cleaning**: Atomize deionized water and excite it with megasonic waves (1 - 3MHz) to form nanometer - sized droplets that wrap particles, gently removing stubborn contaminants and avoiding direct liquid impact damage to the mirror surface.

        - **Supercritical CO₂ Cleaning**: Use the supercritical fluid of CO₂ to dissolve organic substances (such as photoresist volatiles), leaving no residue and not damaging the optical coating.

 - **(2) Exposure Lens Group**

    - **Cleaning in a Vacuum Environment**: In a class - 100 clean room, use customized carbon - fiber tweezers to hold dust - free cotton swabs (dipped in anhydrous ethanol or ultra - pure isopropyl alcohol) and gently wipe the surface in a single direction to avoid circular wiping that may cause scratches.

    - **Laser - induced Desorption (LID)**: For nanometer - scale organic residues, irradiate the contaminated area with a pulsed laser (such as a 266nm wavelength), causing the contaminants to instantly vaporize and detach without contacting the optical surface.

#### 2. Cleaning of Mechanical Moving Parts

 - **(1) Nanometer - scale Guide Rails and Lead Screws**

    - **Combination of Ultrasonic and Vapor - phase Cleaning**:

        - **Ultrasonic Pre - cleaning**: Immerse the components in a mixture of deionized water and a neutral surfactant, and use 40kHz ultrasonic waves to oscillate for 10 - 15 minutes to remove grease and particles.

        - **Vapor - phase Drying**: Rinse with isopropyl alcohol (IPA) vapor condensation to remove the remaining liquid and avoid water marks that may affect the flatness of the guide rail.

    - **Magnetorheological Fluid Cleaning**: Use magnetic particles to bind with contaminants, and then drive the fluid to move directionally through a magnetic field to accurately remove micro - particles in the gaps (such as impurities in the guide rail grooves).

 - **(2) Vacuum Chambers and Valves**

    - **Plasma Cleaning**: Introduce a mixture of O₂ and CF₄ gases, generate plasma in a vacuum environment, etch the polymer residues (such as the carbonized layer of photoresist) on the chamber wall, and activate the surface to remove organic substances.

    - **Electrolytic Cleaning**: For stainless - steel chambers, use a dilute sulfuric acid electrolyte for electrification treatment, and remove metal oxides and ion contamination through an anodic oxidation reaction.

#### 3. Cleaning of Electrical and Sensor Components

 - **(1) Laser Interferometer Components**

    - **Electrostatic Adsorption Cleaning**: Use a polytetrafluoroethylene (PTFE) film with static electricity to gently touch the sensor surface to adsorb tiny particles (such as metal dust), avoiding physical contact damage to the optical path components.

    - **Ultra - pure Water Spray Cleaning**: Spray micron - sized water droplets through a nozzle with a pore size of 0.2μm, use the surface tension of water to carry away dust, and then quickly dry it with nitrogen.

 - **(2) Circuit Boards and Wiring Harnesses**

    - **Freeze Cleaning**: Use liquid nitrogen spray to embrittle contaminants (such as solder residues), and then gently brush them off with a soft brush to avoid traditional solvents seeping into the circuit gaps and causing short - circuits.

### III. Key Control Elements of the Cleaning Process

 - **Clean Environment Requirements**: All cleaning operations need to be carried out in an ISO 1 - class (Class 1) clean room. Personnel should wear full - body dust - proof suits and conductive rubber gloves (static electricity < 100V) before touching components.

 - **Purity Standards of Consumables**:

    - **Deionized Water**: The resistivity should be ≥ 18.2MΩ·cm, and the total organic carbon (TOC) should be < 5ppb.

    - **Chemical Reagents**: They should meet the semiconductor - grade (SEMI C8 standard), with a particle size < 0.1μm and a metal ion content < 1ppb.

 - **Inspection and Verification**:

    - **Laser Particle Counter**: Detect the number of particles on the component surface after cleaning (for example, the number of particles with φ≥0.1μm ≤ 5 particles/cm²).

    - **Spectroscopic Ellipsometer**: Measure the thickness of organic residues on the surface of optical elements (for example, carbon contamination < 0.3nm).

    - **Contact Angle Measurement**: Verify the surface hydrophilicity to ensure that there is no residue of grease - like contaminants (contact angle < 5°).

### IV. Future Technological Trends

 - **Atomic - level Cleaning Technology**:

    - **Atomic Layer Cleaning (ALE)**: By alternately introducing reaction gases (such as HF/O₃ on the Al₂O₃ surface), single - atomic - layer contaminants can be removed, which is suitable for the daily maintenance of EUV optical elements.

 - **Intelligent Cleaning System**: Integrate AI vision detection to real - time identify the type of contamination and automatically match cleaning parameters (such as laser power, ultrasonic frequency), reducing human - intervention errors.

 - **Green Cleaning Process**: Develop biodegradable cleaning solutions (such as bio - based surfactants) to replace traditional fluorides and reduce the environmental burden.