How Pre-Diffusion Cleans Are Used in the Wafer Cleaning Process

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.

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.

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.

How Wet Bench Stations Are Tailored for Specific Manufacturing Process Requirements

The fabrication of semiconductor wafers requires precise, closely controlled, and consistently-repeated procedures. These factors are critically important especially for industries that fabricate semiconductors, medical equipment, and photovoltaic cells. They require the use of custom-made wet benches designed to assist the safe and precise control of corrosive chemicals at high temperatures.

Modutek, with over 35 years of experience in wet bench stations, manufactures a full range of wet bench equipment to address the specific needs of semiconductor manufacturing facilities and research centers. Wet bench stations are tailor made based on the manufacturing requirements of each customer. Modutek’s wet bench equipment for the semiconductor industry meets all UL2360/FM4910 standards for fire and contamination safety.

Sulfuric acid-peroxide is a powerful chemical that is critical to the cleaning process applied to semiconductor wafers. Effective application of this chemical mixture is inherently unstable and therefore it needs to be constantly controlled and re-balanced to maintain efficiency.Modutek’s wet bench equipment ensures the precise chemical concentration levels are maintained and insures the most cost-effective use using an exclusive chemical re-use system.

The silicon nitride wet etching process is another semiconductor fabrication stage that is used to mask chemical etchings on silicon wafers. It also requires high precision and control. Once the etching is successfully done, the masking material should be removed. Precise control of certain chemical mixtures used in wet etching (such as phosphoric acid and DI water) will prevent the possibility of dangerous overheating and explosions. Modutek's wet bench stations are constructed with high-tech safety features and the use of precision software to address such challenges.

Read the complete article titled “How Wet Bench Stations Are Tailored for Specific Manufacturing Process Requirements” for additional information about Modutek’s wet bench stations and process control features. If you have questions or would like to discuss your wet bench requirements, please call Modutek at 408-362-2000 or email modutek@modutek.com.