How Megasonic Cleaners Improve Silicon Wafer Manufacturing

The cleaning of silicon wafers is one of the key process steps needed in semiconductor manufacturing. This as become even more critical as micro circuit geometrics continue to shrink on 300 mm silicon wafers. Sub micron particles must be removed from the wafer substrate without damaging the delicate microcircuit structures from previous process steps. Particles that remain may result in defective semiconductor components that don’t work or low quality devices that have sub-par performance.

Incorporating Megasonic cleaning technology in the wafer cleaning process effectively removes sub-micron particles and contaminants without damaging or altering the wafer surface. In order to clean effectively selecting the appropriate frequency and power level is important. Modutek has partnered with Kaijo Shibuya Corporation to incorporate their high frequency Megasonic cleaning systems directly into Modutek’s wet bench process equipment. The wet bench stations combine chemical cleaning processes such as RCA or SC1 with Megasonic cleaning in the megahertz range to remove particles and contaminants down to 0.1 microns. Depending on the cleaning temperature and duration, cleaning efficiencies of over 99 percent can be achieved.

How Megasonic Cleaning Technology Works

Megasonic cleaning systems use a high frequency generator to create high frequency sound waves through the use of a transducer that is immersed in a liquid filled cleaning tank. The compression waves that are generated from the sound create high pressure at their peaks and low pressure at their troughs. Small cavitation bubbles appear in the low-pressure troughs and collapse in the high-pressure peaks. The action of the bubbles in the liquid effectively removes contaminants and particles from the exposed surfaces.

Lower ultrasonic frequencies in the 20-100 kHz range produce relatively large energetic cavitation bubbles which can cause damage to delicate part surfaces. For applications associated with semiconductor cleaning, megasonic cleaning in the megahertz range is required since it generates much smaller energetic cavitation bubbles. The gentle cleaning action from bubbles at the megasonic frequency range will effectively clean without damaging the wafer surface.

The action of cavitation bubbles in the cleaning tank will also agitate the cleaning solution which reduces boundary layers and allows the cleaning solution access very small surface areas such as crevices and complex shapes. The use of megasonic cleaning in silicon wafer manufacturing improves the overall effectiveness of the chemical cleaning solution by removing small sub-micron particles through the action of energetic bubbles.

Modutek’s Use of Megasonic Cleaning

Modutek has used their partnership with Kaijo Corporation to continually improve the cleaning performance of their wet benches by using Kaijo’s Megasonic Cleaning technology. Kaijo is a world leader in megasonic and ultrasonic cleaning systems and Modutek incorporates the Quava megasonic cleaning system generator into their wet bench stations for this application.

The Megasonic cleaning system incorporated within Modutek’s wet bench station utilizes Kaijo’s standard megasonic generator which operates at 950 kHz. Frequency ranges of 200 kHz, 430 kHz, 750 kHz as well as 2 MHz are also available for cleaning applications that require a more or less robust cleaning action. There are three versions of Megasonic cleaning systems available which provide power levels of 600, 900 or 1200 Watts.

Modutek incorporates the use of Megasonic cleaning into their wet benches using either indirect or direct bath designs. Indirect Megasonic cleaning can operate at temperatures of up to 140 degrees centigrade while the direct design places a Teflon-coated transducer directly into the tank and can operate at temperatures up to 70 degrees centigrade. Both design options provide optimal sub micron particle removal without causing cavitation damage to the silicon wafers at the standard 950 kHz frequency.

Process engineers at semiconductor manufacturing fabs have effectively used Modutek’s wet benches stations that incorporate the use of megasonic cleaning to improve semiconductor device yields. The time needed for cleaning wafers is reduced while cleaning effectiveness is higher with less chemical consumption. The use of Megasonic technology has improved the removal of small sub-micron contaminants and has reduced wafer defects to produce better quality semiconductor devices. If you need to improve wafer manufacturing processes and device yields call Modutek for a free consultation or quote at 866-803-1533 or email [email protected].

How Megasonic Cleaning Improves the Silicon Wafer Cleaning Process

How Megasonic Cleaning Improves the Silicon Wafer Cleaning ProcessAs silicon microscopic circuits and structures shrink in size, the elimination of contaminants from becomes increasingly important. When silicon wafer cleaning is effective, it removes particles as small as 0.1 µm to prevent them from affecting the silicon fabrication process. Traditional wafer cleaning with chemicals may leave some of the smallest particles in place and production line output quality can suffer. The semiconductor components produced may be of inferior quality or fail completely. Megasonic cleaning with sound waves in the MHz range generated in a water cleaning solution can remove particles down to 0.1 µm in size and improve cleaning performance.

How the Megasonic Process Cleans

The Megasonic Cleaning System consists of a high-frequency generator, transducers that convert the electric signal from the generator to sound waves in the water, and a cleaning tank to hold the cleaning solution and the silicon wafers. Sound waves in the MHz frequency range travel through the cleaning liquid and generate microscopic cavitation bubbles in the low-pressure wave troughs. When the bubbles collapse in the high-pressure wave peaks, they produce tiny jets of water.

When the bubbles collapse near a wafer, the resulting jets hit the silicon and dislodge any particles adhering to the surface. The particles are carried away by the water currents and the microscopic bubbles are so numerous that all surfaces are cleaned. The bubbles and the cleaning effect are present throughout the liquid and they penetrate into holes, crevices and microscopic structures, cleaning completely.

Megasonic Cleaning Benefits

In addition to cleaning silicon wafers and removing microscopic particles more effectively than traditional cleaning methods, Megasonic Cleaning provides several other benefits over the use of chemicals. The rise in output quality is accompanied by lower costs, a safer process environment and shorter process times.

When a semiconductor fabrication facility uses fewer chemicals for cleaning wafers, costs decrease. The facility has to purchase smaller amounts of chemicals, storage costs are lower and costs for disposal are less. Depending on the process, Megasonic Cleaning may allow a facility to eliminate certain chemicals completely, resulting in even higher savings.

The Megasonic Cleaning process is safe and environmentally friendly. The megasonic waves and the cleaning solution do not present any danger to equipment or operators who can set a timer and come back when the cleaning process is finished. The water-based solution is not toxic and does not require special disposal. Compared to chemical cleaning, the storage and handling of Megasonic cleaning materials is safe and easy, power consumption is lower and less water is required.

Modutek’s Megasonic Cleaning System

The Modutek Megasonic Cleaning System was developed together with ultrasonic technology leader Kaijo Corporation to reflect the specific demands of silicon wafer cleaning. The high operating frequency in the MHz range ensures gentle but effective cleaning of delicate materials without pitting the silicon surface or damaging the silicon wafer structures.

Modutek’s partnership with Kaijo lets the company offer an integrated system that features the Quava Megasonic generator and transducer within Modutek’s cleaning baths. Megasonic’s baths are available in the indirect heating MSI series that can heat the cleaning solution up to 140 degrees centigrade while the direct heating MSD series can heat the cleaning solution up to 70 degrees centigrade. Both baths are ideal for submicron particle removal with a high power density and high efficiency.

The Megasonic System is available with 600 W, 900 W and 1200 W power ratings at the standard 950 kHz frequency. Frequencies of 200 kHz, 430 kHz, 750 kHz and 2 MHz are also available for applications that require the more robust cleaning action from the lower frequencies or for very delicate components at the higher frequency. In any case, Modutek can advise customers to make sure they select the ideal Megasonic Cleaning configuration for their specific silicon wafer cleaning applications.

How Megasonic Cleaning Technology Improves Silicon Wafer Yields

How Megasonic Cleaning Technology Improves Silicon Wafer YieldsSilicon wafer cleaning is a key process during semiconductor manufacturing that becomes especially critical for smaller microcircuit geometries on 300 mm (approx. 12 inch) silicon wafers. Sub micron particles must be removed from the wafer substrate during processing without damaging the delicate microcircuit structures. Any particles that remain may result in defective semiconductor components or output of low quality.

A process incorporating Megasonic Cleaning technology at higher megahertz frequencies can help remove tiny particles and contaminants without damaging or altering the surface of the wafer. The selection of appropriate frequencies and power levels is important for effective cleaning results. Modutek has partnered with leading ultrasonic cleaning system provider Kaijo Corporation to incorporate Kaijo’s high frequency Megasonic Cleaning technology into the Modutek wet bench process equipment. These wet benches can combine chemical cleaning processes such as SC1 with megasonic cleaning in the megahertz range to remove a high percentage of 0.1 to 0.4 micron particles. Depending on cleaning times and temperatures, cleaning efficiencies of over 99 percent can be achieved.

How Megasonic Cleaning Works

In megasonic cleaning systems, a megasonic frequency generator produces high-frequency sound waves in a liquid via a transducer immersed in a liquid bath. The sound waves are compression waves that generate high pressure at their peaks and low pressure in their troughs. Cavitation bubbles appear in the low-pressure troughs and collapse in the high-pressure peaks. This bubble action in the cleaning liquid removes contaminants from exposed surfaces.

Low ultrasonic frequencies in the range of 20 to 40 kHz produce comparatively large, very energetic bubbles whose collapse can cause cavitation damage to delicate surfaces. For semiconductor cleaning applications, megasonic frequencies in the MHz range generate much smaller, less energetic bubbles. Their gentle cleaning action does not damage the wafer surface while still cleaning effectively.

At the same time, the bubbles agitate the cleaning solution, reducing boundary layers and promoting cleaning solution access to small surface features such as crevices and complex shapes. Using megasonic cleaning in silicon wafer manufacturing improves the effectiveness of the chemical cleaning solution by removing small sub-micron particles through the action of energetic bubbles.

Modutek Megasonic Cleaning Systems

Modutek has been in partnership with Kaijo Corporation to improve the cleaning performance of their wet benches by incorporating the use Kaijo’s Megasonic Cleaning technology. Kaijo Corporation is a world leader in megasonic and ultrasonic cleaning systems and Modutek incorporates the Quava megasonic cleaning system generator into their wet bench equipment for this application.

Modutek’s Megasonic Cleaning System that utilizes Kaijo’s megasonic generator operates at 950 kHz in the standard version. Frequencies of 200 kHz, 430 kHz, 750 kHz and 2 MHz are also available for cleaning applications that require a more or less robust cleaning action. The Megasonic Cleaning System can operate at power levels of 600, 900 or 1200 W.

Modutek has incorporated Megasonic Cleaning into their wet benches in either indirect or direct bath designs. Indirect Megasonic Cleaning can operate at temperatures of up to 140 degrees centigrade while the direct design places a Teflon-coated transducer directly into the tank and can operate at up to 70 degrees centigrade. Both designs offer optimal sub micron particle removal without cavitation damage to the silicon wafers at the standard 950 kHz frequency.

Decision makers at semiconductor manufacturing facilities can use Modutek’s wet benches that incorporate the use of megasonic cleaning technology to improve yields. Cleaning times are reduced while cleaning effectiveness is higher and lower chemical consumption can contribute to better cost control. Improved removal of small sub-micron contaminants and particles can reduce wafer defects and produce better quality output. If you need to improve wafer processing quality and yields and want a free consultation or quote on using wet bench stations that incorporate megasonic cleaning technology, call Modutek or email [email protected].