The following are the core principles and features for selecting and using cleaning equipment for high-cleanliness requirements: Core Principle: From "Cleaning" to "Cleanliness Assurance System" The goal of high-cleanliness cleaning is not only to remove visible stains but also to control micro-particles, organic residues, ionic contamination, microorganisms, moisture, etc., and even to prevent secondary contamination caused by the cleaning process itself (such as particle scratching, metal ion migration, electrostatic attraction).   Key Features of Equipment and Process   1. Process Combination, Not Single Technology    · There is no "universal" equipment. High-cleanliness cleaning lines are usually a precise combination of multiple technologies, forming a multi-step process flow.    · Typical Combined Process:      · Pre-cleaning: Use high-pressure spraying or coarse ultrasonics to quickly remove most macro contaminants. Main Cleaning (Core): Use high-frequency/multi-frequency ultrasonics, vacuum ultrasonics, or megasonics, combined with dedicated high-purity cleaning agents, to remove sub-micron particles and molecular organic matter.      · Multi-stage Rinsing: Use **2-3 or more stages of countercurrent rinsing.** Each stage uses a cleaner medium than the previous one (e.g., ultrapure water) to sequentially dilute and remove residual cleaning agents and contaminants, preventing **"cross-contamination."**      · Final Treatment: May include **IPA (Isopropanol) vapor drying, vacuum drying, centrifugal drying, hot nitrogen drying**, etc., to ensure the workpiece is absolutely free of water marks, residues, and oxidation. 2. Extreme Control over Cleaning Media    · Water: Must use **DI water (deionized water)** or **UPW (ultrapure water)**, with strict standards for resistivity, particulate matter, microorganisms, and total organic carbon content.    · Cleaning Agents: Select specialized formulations that are low-foam, high-purity, easy-to-rinse, and residue-free, sometimes even required for use in an oxygen-free environment.    · Media Filtration: All liquid circulation systems must be equipped with high-precision filtration systems (such as $0.1\text{ micron}$ or even lower absolute filters) and online monitoring of particulate matter to remove particles stripped during cleaning and prevent their re-adhesion. 3. Equipment Material and Structure Designed for "Cleanliness"    · Material: All parts that contact the media and workpiece, such as tanks, pipes, and nozzles, must use high-grade materials like stainless steel (e.g., 316L), PTFE (Teflon), PFA, which are corrosion-resistant, low-leaching, and non-adsorbing, preventing the equipment itself from becoming a source of contamination.    · Sealing and Environmental Control: The entire system (especially the rinsing and drying zones) must have high sealing integrity and may be purged with inert gas like nitrogen to prevent particles and oxygen from entering the air. The working environment often requires **"Cleanroom"** level standards. 4. High Controllability and Repeatability of the Process    · Precise Parameter Control: All parameters such as temperature, pressure (vacuum level), ultrasonic power/frequency, concentration, flow rate, and time must be precisely set, monitored, and recorded to ensure complete consistency of the process across every batch.    · Automation and Error Prevention: The entire process should run fully automatically to reduce contamination and errors caused by manual intervention. Must have recipe management functionality for one-click calling of cleaning programs for different products. 5. Application of Advanced Cleaning and Drying Technologies    · Vacuum Ultrasonic Cleaning: As previously discussed, it is a cutting-edge technology for handling deep/blind holes and achieving perfect drying, almost standard in the semiconductor and optics fields.    · Megasonic Cleaning: Frequency above $700\text{kHz}$, utilizing the acoustic streaming effect of sound waves rather than violent cavitation, can more gently and effectively remove nanoscale particles without damaging extremely delicate surfaces (such as chip pattern structures).    · Supercritical $\text{CO}_2$ Cleaning: Uses liquid/supercritical carbon dioxide as a solvent; is residue-free, requires no drying, and is environmentally friendly, particularly suitable for microelectronics and precision devices. 6. Stringent Cleanliness Verification and Monitoring    · Online Monitoring: Integration of **particle counters, TOC (Total Organic Carbon) analyzers, resistivity meters**, etc., to monitor the cleanliness of the cleaning liquid and rinse water in real-time.    · Offline Inspection: Cleaned products must be inspected in a cleanroom using specialized equipment, such as particle laser scanning, ion chromatography analysis (to measure ionic residue), surface tension testing (to measure organic residue), and microscopic observation.   Examples of Typical High-Cleanliness Applications   · Semiconductor Chip Manufacturing:   · Process: RCA standard cleaning ($\text{SC}_1/\text{SC}_2$ chemical solutions) combined with megasonics or vacuum ultrasonics.   · Requirement: Removal of nanoscale particles, metal ions, and organic matter, achieving "atomic-level cleanliness" on the surface.   · Equipment: Fully automatic wet bench or single-wafer cleaning machine, operating in an ultra-high cleanliness environment (Class 1 or better). · Medical Devices and Implants:   · Process: Multi-tank ultrasonic cleaning (including enzymatic agents) $\to$ Multi-stage pure water rinsing $\to$ Pure steam or superheated water sterilization $\to$ Vacuum drying.   · Requirement: Bio-level cleanliness, sterile, pyrogen-free, and free of any chemical residue.   · Equipment: Uses hygienic design, features cleaning parameter recording and traceability, compliant with GMP (Good Manufacturing Practice) requirements.   Summary   For products with high-cleanliness requirements, cleaning equipment has evolved from a "machine" into a **"controllable clean manufacturing environment."** Its core features are:   1. Systemic: It is an integrated system of multiple technologies: physics, chemistry, fluid dynamics, and control. 2. Customization: The process chain must be tailor-designed based on specific contaminants, cleanliness metrics (such as particle size, residue type), and workpiece characteristics. 3. Traceability and Verifiability: Every process parameter is monitored and recorded, and the final cleanliness is validated by scientific methods. 4. Contamination Prevention: One of the core goals of equipment design and operation is to prevent the introduction of new contaminants during the cleaning process.   The key to selecting and using this type of equipment is: first, clearly define the specific quantified standard for "cleanliness," then reverse-engineer a controllable, repeatable process flow that can achieve that standard, and finally select or customize the equipment units and control systems capable of realizing the technical requirements of every step in that process flow.