Silicon 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 Modutek@modutek.com.