How a Megasonic Cleaning System Removes Submicron Particles from Delicate Components
February 27, 2017
Megasonic cleaning systems use high frequency generators and transducers operating in the MHz range to clean delicate parts such as silicon wafers, and related microelectronic devices. Semiconductor manufacturing processes rely on repeated cleaning operations, and megasonic systems clean more rapidly and more completely than other cleaning methods in many applications. Megasonic cleaning systems are especially effective in the removal of submicron particles during the manufacturing process of semiconductors, MEMs, LCD screens and solar panels.
How Megasonic Cleaning Systems Work
All ultrasonic and megasonic cleaning systems work by generating cavitation bubbles in a cleaning solution. As a megasonic wave propagates through the fluid, wave troughs produce areas of low pressure where microscopic bubbles form. When the high pressure wave peak arrives, the bubbles collapse and release a substantial amount of energy. The energy from many small bubbles collapsing at the same time acts on surface contaminants of the devices being cleaned, breaking up, dissolving and removing the contamination.
As the system frequency rises, the waves are closer together and there is less time for bubbles to form. As a result, higher frequencies produce smaller bubbles and gentler cleaning action as the collapsing bubbles produce less energy. For MHz frequencies, the bubble size approaches the size of the submicron particles, but the energy released by the collapsing bubbles is small enough that it doesn’t damage the semiconductor wafer surface. It is however strong enough to dislodge the particles.
Submicron particles are hard to remove because they are small enough to be embedded in the boundary layer between the solid wafer and the free-flowing cleaning solution. Even when the cleaning solution moves quickly under pressure, the boundary layer remains static and holds the tiny particles in place. During megasonic cleaning microscopic bubbles move right up to the particles and, when a bubble collapses, the resulting energy burst dislodges the particle. The megasonic cleaning system produces a current that takes the particle away from the wafer surface and prevents it from becoming attached again.
This process effectively removes almost all particles from the surface of the semiconductor parts and results in fewer defects in the final product. Semiconductor manufacturing facilities can improve product quality and produce fewer defective products.
Megasonic Cleaning System Characteristics and Features
A megasonic cleaning system consists of a high frequency generator capable of producing MHz frequencies, a corresponding transducer and a tank to hold the cleaning solution and the parts to be cleaned. Ideally the unit can operate over a range of frequencies to let operators adjust the system to meet the cleaning performance they need. Adequate cleaning power is required and the system should not need extensive set-up and calibration.
Kaijo has extensive expertise and broad experience with ultrasonic and megasonic cleaning systems. The company can advise customers on the best cleaning methods and can help customers select the system, equipment and features best suited for their process. The Quava megasonic cleaning system is a cost-effective solution that can operate at lower ultrasonic frequencies of 26 kHz to 200 kHz as well as higher megasonic frequencies of 430 kHz, 750 kHz and 950 kHz with up to 1200 watts per generator. The company also offers the desktop compact Quava Mini system, the US Shower, the Mega Tube and the Spot Shower for additional megasonic cleaning applications. These components complement Kaijo’s range of products, allowing the company to support customers in all their megasonic cleaning applications.