The silicon wafers that are processed in research centers and semiconductor manufacturing facilities must be cleaned repeatedly in aggressive chemical baths that remove surface contaminants from the wafers. This is essential in removing surface impurities which would affect the diffusion of dopants in the diffusion ovens.
Wafers must be completely cleaned and free from impurities, and the wafer cleaning process may involve the following multiple cleaning methods to prepare the wafer for the diffusion stage:
Organic material and photoresist - Wafers may still have photoresist left on the surface, even after undergoing previous stages (such as masking). The photoresist and any related materials need to be removed since they will inhibit the doping process. These materials are removed by procedures that may include Piranha etch (a mixture of sulfuric acid and hydrogen peroxide).
General cleaning and metallic particles - The two-step RCA cleaning process is used to remove light organic contamination from the wafer's surface. The first step SC1, removes the organic contamination from the wafer's surface, while the second step SC2 removes the leftover metallic particles from the wafer's surface and creates a protective layer on the silicon surface.
Organic material and photoresist - Wafers may still have photoresist left on the surface, even after undergoing previous stages (such as masking). The photoresist and any related materials need to be removed since they will inhibit the doping process. These materials are removed by procedures that may include Piranha etch (a mixture of sulfuric acid and hydrogen peroxide).
General cleaning and metallic particles - The two-step RCA cleaning process is used to remove light organic contamination from the wafer's surface. The first step SC1, removes the organic contamination from the wafer's surface, while the second step SC2 removes the leftover metallic particles from the wafer's surface and creates a protective layer on the silicon surface.
Native oxide layer removal – The native silicon oxide layer must be removed for some semiconductor fabrication steps. Hydrofluoric acid is commonly used but it is extremely dangerous to handle so it requires a proper and safe set-up. The wafers are typically dipped into the acid (which reacts very quickly), rinsed with DI water and then dried to prepare them to the diffusion oven.
Other cleaning methods – Modutek has pioneered wafer cleaning process equipment and methods that do not use harsh cleaning chemicals. Instead, these methods include megasonic cleaning which uses megasonic sound waves in the cleaning solution to remove particles and impurities in cleaning wafers.
Other cleaning methods – Modutek has pioneered wafer cleaning process equipment and methods that do not use harsh cleaning chemicals. Instead, these methods include megasonic cleaning which uses megasonic sound waves in the cleaning solution to remove particles and impurities in cleaning wafers.
Read the complete article “How Pre-Diffusion CHow Pre-Diffusion Cleans Are Used in the Wafer Cleaning Processleans Are Used in the Wafer Cleaning Process” for further details. You may also contact Modutek at 866-803-1522 to discuss which wafer cleaning process is right for your application or to get a free quote.
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