Successful semiconductor manufacturing relies on the effective cleaning of silicon wafers at several stages of the manufacturing process. Impurities, contaminants and residues from process steps have to be completely removed to ensure that the manufactured components have the required functionality and the desired quality. Silicon wafer cleaning equipment such as those offered by Modutek helps increase yields and improves the cleaning process to deliver high quality results.
Standard RCA cleaning, named after the RCA Corporation where it was developed, involves immersion of the silicon wafers in hot acidic and alkaline solutions. The first bath usually contains hydrogen peroxide and ammonium hydroxide while the second bath has hydrogen peroxide with hydrochloric acid. The first solution removes organic contaminants from the surface of the silicon wafers by dissolving the bonds binding the contaminant particles to the silicon and by the oxidizing action of the chemicals. The second solution dissolves and removes alkaline residues and metallic particles.
RCA cleaning is the most common cleaning method used in the semiconductor manufacturing industry. It is especially effective in removing particles responsible for defects in semiconductors. When detected, such defects reduce the semiconductor yields of the manufacturing process and, if not detected, they reduce the quality of the resulting components.
Cavitation bubbles created by the use of megasonic cleaning systems complement the chemical cleaning action of RCA cleaning. As semiconductor geometries become smaller and smaller in size, microscopic particles become more important in the creation of defects. Particles that might be too small to impact the function of large components become critical defect-producing factors for the smallest semiconductor structures.
The bubbles of megasonic cleaning systems add a mechanical component to the overall cleaning action. When the cavitation bubbles burst, they release energy that helps dislodge contaminant particles from the silicon substrate. This mechanical cleaning action can speed up the overall cleaning process and make it more effective in removing even the smallest particles.
SPM Clean – Piranha Etch
When silicon wafers are heavily contaminated, for example when contaminants are clearly visible or for the removal of photo resist after wafer processing, piranha etches provide a powerful cleaning method. The cleaning solution is made up of a mixture of hydrogen peroxide and sulphuric acid. The solution is highly corrosive and yields aggressive cleaning to remove large amounts of material. Sometimes wafers can be run through a piranha etch treatment before further cleaning with the RCA method.
FEOL and BEOL Processing
Front End of Line (FEOL) processing is the part of semiconductor manufacturing in which the components, such as transistors, are created in the semiconductor wafer, while Back End of Line (BEOL) processing involves depositing the metallic interconnections. Cleaning may be required after etching, after ion implantation or after metal deposition to remove process residue.
Water-based cleaning removes some of the impurities and RCA cleaning or piranha cleaning may be used to remove masks, photo resist or chemical residue. Ultrasonic cleaning is effective in helping remove particulate contaminants and ozonated deionized water may be used as well. At the end of each cleaning process, the wafers may be dried with isopropyl alcohol (IPA) in preparation for further processing steps.
Modutek has specialized in silicon wafer cleaning equipment for the semiconductor manufacturing industry and can deliver a complete spectrum of semiconductor cleaning solutions. In addition to chemical cleaning stations, Modutek incorporates the use of Megasonic cleaning equipment and IPA dryers.
Modutek silicon wafer cleaning solutions are based on the company’s thirty years of experience in providing semiconductor manufacturing equipment to the semiconductor industry. Modutek’s team of engineers can advise customers on the choice of equipment and design custom cleaning solutions for a wide variety of applications. If you need reliable and effective silicon wafer cleaning equipment in your manufacturing process, contact Modutek at 866-803-1533 or email [email protected].