[KoMiCo Lab] Fundamentals of Semiconductor Component Cleaning: Ultrasonic Cleaning Technology

In semiconductor manufacturing, even the slightest contamination can directly lead to product defects or yield loss. One of the key cleaning processes applied to address this challenge is Ultrasonic Cleaning, which demonstrates exceptional effectiveness in removing surface and internal contaminants, particularly from components with complex structures.

■ Definition and Principle of Ultrasonic Cleaning

Ultrasonic Cleaning is a cleaning process that utilizes the Negative Pressure effect of ultrasonic waves and the phenomenon of Cavitation to remove particles from surfaces, using a solvent as the cleaning medium.

▲ Ultrasonic Frequency Spectrum Comparison

Ultrasonic waves transmit high-frequency vibrational energy into a liquid, creating an environment where pressure periodically fluctuates.

During this process, the acoustic wave alternates between compression and rarefaction phases. In the rarefaction phase, the local pressure within the liquid drops sharply. When this pressure falls below the vapor pressure of the liquid, vaporization occurs and microscopic bubbles are formed. This phenomenon is known as the Negative Pressure Effect.

▲ Cavitation Effect

A multitude of microbubbles generated by ultrasound undergo repeated cycles of contraction and expansion at a rate of approximately 25,000 to 30,000 oscillations per second, and once they reach a critical threshold, they collapse abruptly.

This collapse produces localized high temperature and high pressure shock waves that propagate strong physical energy throughout the liquid. The resulting micro-impacts effectively detach contaminants adhered to the surface of semiconductor components. This entire phenomenon is known as cavitation, and it represents the fundamental physical principle by which ultrasonic cleaning operates.

■ Key Factors Affecting Ultrasonic Cleaning

Ultrasonic cleaning is influenced by several physical factors that significantly affect the intensity of cavitation and the overall cleaning efficiency.

The first factor is temperature. As the liquid temperature increases, molecular kinetic energy rises, making cavitation easier to occur. At an optimal range, bubble formation and collapse become more active, thereby improving cleaning efficiency. However, if the temperature approaches the boiling point, excessive vaporization can weaken cavitation, which is why selecting the right temperature for each cleaning purpose is critical.

The second factor is dissolved gas. Air or impurities dissolved in the cleaning liquid can absorb and disperse the shock energy inside the bubbles, thereby weakening cavitation intensity. For effective cleaning, it is important to minimize dissolved gas in the solution, which can be achieved through intermittent ultrasonication or heating.

Next is surface tension. Higher surface tension allows bubbles to accumulate more energy, which leads to stronger cavitation upon collapse. However, when contaminants include viscous materials such as organic oils, bubble formation becomes more difficult, reducing cleaning efficiency. This makes surface tension and chemical composition of the cleaning liquid important design variables.

Additionally, ultrasonic frequency is a key factor that determines bubble size, collapse intensity, and energy delivery.

Category	28kHz	40KHz	Ultra-sonic
Cleaning Principle	Cavitation	Cavitation	Molecular acceleration
Particle Acceleration	~1500 G	~2500 G	≥10,000 G
Characteristics	High energy	High energy	High directivity
Removable Particle Size	≥3 μm	≥2 μm	≥1 μm
Application	General cleaning	General cleaning	Precision cleaning

Lower frequencies (e.g., 28–40 kHz) generate stronger cavitation, making them effective for removing large or strongly adhered particles. Higher frequencies (100 kHz and above), on the other hand, produce finer bubbles that enable precision cleaning of delicate structures.

Ultrasonic cleaning remains a core process in semiconductor manufacturing, but as device geometries continue to shrink and structures become increasingly complex, more precise and efficient cleaning approaches are required.

To address these challenges, KoMiCo has advanced ultrasonic cleaning technologies into specialized solutions tailored to specific process requirements.

In the next article, we will introduce CO₂ Blasting, a dry cleaning method that leverages the unique properties of dry ice — low hardness and sublimation at room temperature — to achieve effective surface cleaning. Please stay tuned for more.

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<About KoMiCo>

KoMiCo, established in 1996, was the first company in Korea to commercialize cleaning and coating services for semiconductor equipment components. With global operations spanning the United States, China, Taiwan, and Singapore, KoMiCo has earned quality certifications from some of the world’s leading semiconductor manufacturers, solidifying its position as a Global No.1 in the industry.

Building on its advanced cleaning and coating technologies, KoMiCo continues to enhance its core business while expanding into the development and supply of key OEM components for semiconductor equipment. Moving forward, the company remains committed to improving customers’ productivity and yield, and aims to become a global leader in the semiconductor component cleaning, coating, and manufacturing industry.