Tips on Selecting Wafer Processing Equipment for Your Application

The semiconductor manufacturing and research industries use wet benches to produce silicon wafers that need to undergo cleaning and etching.

The wet bench equipment needs to be flexible configured to meet certain manufacturing processes. Ideally, it should be designed for both acid and solvent cleaning applications.

Usual processes used for wafer processing equipment include KOH Etching, Buffer Oxide Etching (BOE), RCA Clean, plating and Megasonic cleaning. The equipment can also be tailored to meet the customer's specific process requirements. Customers can choose three different types of wet benches according to the budget framework and the process:

·         Fully automated stations – This offers excellent consistency of process steps and improved output quality. It is designed to precisely control the use and chemicals and process times. This leads to minimized wastes which in means in saving money as well as easier compliance with environmental regulations. Automated stations also help to reduce operator errors.

·         Semi-automated stations – This offers some features of the fully automated stations, at a much lower cost. It has servo-controlled robots which allow operators to precisely control chemical use and process times. It also has user-friendly controls.

·         Manual stations - This offers no robotics but has the same high quality process equipment as the fully and semi-automated stations.

All of Modutek’s wafer processing equipment stations are built with white propylene construction with wiring to NFPA 70 and 79, and have safety features. They can be ordered as standard units or can be customized to meet certain processing, etching or cleaning applications.

Our full article “Tips on Selecting Wafer Processing Equipment for Your Application” goes into more detail. If you have questions after reading this, please contact Modutek at Modutek@Modutek.com. 

How Marangoni Drying Produces Superior Surface Conditioning for Wafer Processing

In the final step of silicon wafer processing, wafers often have to be cleaned, rinsed, and dried. They must be free of any contamination or water marks. Contamination in silicon wafers leads to defects in the next processing steps or to high failure as the impurities negatively impacts their quality. IPA drying using the Marangoni drying effect results to dry silicon wafer surfaces without leaving any residues or water marks.

Modutek's standalone IPA vapor dryer is ideal for this drying procedure. There, the IPA vapor is introduced at the top of the drying tank. The Marangoni drying effect takes place -- since the IPA has a lower tension surface than water, it introduces a surface tension gradient where it interfaces with the water on the wafer surface. As a result, the water flows away from the surface of the wafer, leaving it completely clean and dry, with no watermarks whatsoever. The departing water, meanwhile, carries the impurities or particles that are suspended within it.

Modutek's IPA vapor dryer consists of a wide cabinet built of polypropylene construction which is fitted with Teflon (including its valves and tubes). Operation can be controlled by the menu on the touch screen. The dryer options include PVC construction, a manual lid, and a quick dump feature. Modutek can also customize the dryer to meet customer specifications.

Modutek's IPA vapor dryer is cost-effective and can be incorporated in a wet bench process without the need to add drying transfer steps. Read our complete article “How Marangoni Drying Produces Superior Surface Conditioning for Wafer Processing” to learn more about Modutek’s Marangoni drying. You may also contact us at Modutek@Modutek.com if you would like additional information.

Why Pre-Diffusion Cleans Are Critical in Wafer Cleaning Processing

Before silicon wafers are placed in a diffusion furnace, they should be cleaned first to remove impurities and particles from their surfaces. This is known as "pre-diffusion cleaning."

Pre-diffusion cleaning can be done using various methods:

1. RCA wafer cleaning process - It consists of two steps:

·         Standard cleaning 1 (SC1) - The silicon wafers are cleaned with a solution containing ammonium hydroxide and hydrogen peroxide, which helps in removing organic particles. However, the metallic ions are still present in the wafers' surfaces.

·         Standard cleaning 2 (SC2) - After undergoing the SC1, the silicon wafers are cleaned in a bath containing hydrochloric acid and hydrogen peroxide. This solution removes leftover metallic traces from the wafers' surfaces.

2. Piranha etch clean - This method uses a solution of sulfuric acid and hydrogen peroxide, which dissolves larger and more stubborn amounts of organic residue from the wafers.

3. Megasonic cleaning - Uses cavitation bubbles produced by megasonic waves in a bath to remove impurities from the wafers. Unlike other methods, megasonic cleaning doesn't use harsh chemical baths.

4. Ozone cleaning - Uses deionized (DI) water to rinse the inorganic contaminants away from the wafers. Then the wafers are placed inside the ozone chamber. The ozone's powerful oxidizing action converts the organic particles to carbon, leaving the wafers clean and free from impurities.

Wafers that are not thoroughly cleaned may affect subsequent diffusion steps and negatively impacts the final product. That's why pre-diffusion cleaning is important. Modutek offers a complete line of chemical baths and wet processing equipment that supports the wafer cleaning processes mentioned above. These are designed to provide effective cleaning that will leave silicon wafers particle-free and ready for diffusion.

Contact Modutek by email Modutek@modutek.com to learn more or read the complete article titled “Why Pre-Diffusion Cleans Are Critical in Wafer Cleaning Processing.”

How the Advanced Ozone Cleaning Process Improves Wafer Yields and Reduces Costs

Modutek's advanced ozone cleaning process is a better alternative to the traditional wafer cleaning methods and reduces chemical use.

The ozone cleaning process involves the use of ozone which converts organic residue on wafers into carbon dioxide through oxidation. This process effectively cleans wafers so they are free of contaminants. Modutek's advanced ozone cleaning process leads to improved silicon wafer cleaning and reduced use of harmful cleaning chemicals.

How does the ozone cleaning process work?

Modutek DryZone gradient dryer uses DI water to rinse away organic impurities from the wafer before the wafer is exposed to ozone. The Coldstrip ozone cleaning method cleans at sub ambient temperatures while the Organostrip cleans at room temperature.

The ozone has a powerful oxidizing action which converts carbon impurities of organic residue to carbon dioxide. This results into wafers that are clean and free of particles.

Modutek's advanced ozone cleaning process can be used with plain water or just a mild solvent. It doesn't rely on harsh cleaning solvents, unlike other traditional cleaning methods. The wastes resulting from the advanced ozone cleaning process are harmless to the environment, while it maintains its superior cleaning performance.

It is also cost-effective: the equipment, processing, shipping, handling and disposal costs are greatly reduced compared to those in other cleaning processes such as Piranha (which, for instance, requires several cleaning tanks, some of which use cleaning solvents). Modutek's advanced ozone cleaning process doesn't require adherence to strict regulations since it uses very eco-friendly methods.

If you have questions, you may contact Modutek by email Modutek@modutek.com to learn more or read the complete article titled “How the Advanced Ozone Cleaning Process Improves Wafer Yields and Reduces Costs.”