How Piranha Etch is Used in Silicon Wafer Cleaning

How Piranha Etch is Used in Silicon Wafer CleaningThe fabrication of silicon wafers is carried out with repeated etching and cleaning steps to produce the micro-structures required for the final silicon semiconductor products. Piranha or SPM (sulfuric peroxide mix) solutions can clean organic material from wafers and oxidize most metals. The powerful chemical action that makes it a favorite for resist strip and for the cleaning of wafers with organic residue also makes it difficult to use. High quality silicon wafer cleaning equipment designed to handle the corrosive chemicals safely is required for carrying out piranha etch safely and effectively.

What is Piranha Etch and How is it Used

A piranha solution is made up of a mixture of sulfuric acid and hydrogen peroxide. The most common ratio is approximately three parts acid to one part peroxide but solutions of up to seven parts acid to one part peroxide are sometimes used. The solution is highly exothermic and is prepared by slowly adding the peroxide to the acid. The mixture heats up rapidly and is often used at temperatures of around 130 degrees C. Once operating temperature and the desired concentration are reached, the wet bench equipment has to heat the solution to maintain the temperature and keep the etch rate constant.

When a facility wants to re-use a piranha solution for an extended period of time, the solution must be spiked with extra hydrogen peroxide. Hydrogen peroxide is unstable in the solution and decomposes, reducing the etching power of the bath. Spiking with additional hydrogen peroxide lets a facility use a piranha solution for up to eight hours rather than having to replace it every two hours. Spiking saves money by conserving sulfuric acid but it requires wet bench equipment that can handle the process and the spiking.

Semiconductor fabrication facilities and research labs use piranha etching to clean residue from silicon wafers and glass. The solution removes trace organic contaminants and strip residue while oxidizing metals. The underlying surfaces are hydroxilated making them hydrophilic or attractive to water, a characteristic that can be used in subsequent silicon semiconductor manufacturing process steps.

Modutek’s Silicon Wafer Cleaning Solutions

Modutek specializes in semiconductor manufacturing equipment and wet bench technology that includes solutions for wafer cleaning. The company can supply standard equipment or can customize wet bench solutions to fit specific customer requirements. Priorities are high quality materials, excellent designs, low cost of ownership and high quality results. Piranha wafer cleaning is supported by Modutek’s QFa quartz recirculating tanks and the QA constant temperature baths. Both can be installed in a wet bench station and the process can be controlled automatically, semi-automatically or manually.

The QFa series high temperature re-circulating baths provide fast even heating over a temperature range of 30 to 180 degrees C. The heat up rate can be up to 2 degrees C. per minute and the temperature control is up to plus/minus 1 degree C. The quartz bath is made of flame-polished semiconductor-grade quartz insulated with silica fiber rated up to 1260 degrees C.

The QA series constant temperature quartz baths are made from the same materials with the same control characteristics as the QFa series but they feature a magnetic stirrer, an aspirator valve system, gravity drain and a quartz bubbler. Both baths are available in standard sizes or can be custom made to fit customer requirements.

Modutek can provide a complete range of wet bench and silicon wafer cleaning equipment that includes baths suitable for piranha cleaning applications. The equipment is designed with safe and reliable operation in mind and the cleaning equipment eliminates contaminants and impurities to the greatest extent possible. Modutek wet bench equipment allows operators to use piranha cleaning methods safely to increase facility throughput while maintaining or improving output quality. Call or email Modutek for a free quote or recommendations on using the right equipment for your wafer cleaning application.

Tips on Selecting Chemical Delivery Systems for Your Application

Tips on Selecting Chemical Delivery Systems for Your ApplicationChemical delivery systems handle the chemicals required to support various industrial processes. Chemicals that are often corrosive or hazardous are stored securely and delivered to the process in specified concentrations and mixtures. Once used in a particular process, the chemicals can be recovered and neutralized, disposed of or re-used.

Such chemical delivery systems, when integrated in processes such as semiconductor manufacturing using wet bench equipment, allow safe operation with accurate dosages and quick change from one chemical to another. The systems reduce spills and operator error and they can save money by using exactly the amounts of chemical needed. Depending on the process and the volume of chemicals, chemical delivery system design must take into account appropriate storage methods and customization to meet the requirements of the specific application.

Considerations Before Purchase

In addition to selecting a supplier that has an excellent reputation and extensive experience in the design and building of chemical delivery systems, there are specific factors that affect the type of system needed.

  • How much of a particular chemical is used in the process? Storage options from large volumes to small local storage must be available.
  • How does the system calculate the required chemicals and how is the software for calculations supported?
  • What are the control options and do they integrate easily and well with wet bench controls?
  • What safety, error and leak detection features are available?
  • Is the system flexible enough to adapt to specific process requirements and can the supplier undertake such customization?


Before making a purchasing decision, facility managers and staff responsible for the technical evaluation have to make sure the chosen chemical delivery system can meet their requirements on various factors such as the five listed above.

Chemical Delivery Systems by Modutek

Modutek has extensive experience in the design and construction of chemical delivery systems that meet the needs of their customers. The company’s systems feature a variety of storage options such as large volume storage, chemical tote or local drum, bottle or carboy. Storage includes level sensing from low/low through low and high to high/high and levels are displayed on a touch screen.

The SolidWorks Simulation Professional and SolidWorks Flow Simulation software calculates accurate chemical requirements. Because the software and the controls are designed and programmed in house, Modutek can customize them and can support the software with its own technicians. Based on the calculations, the controls provide precise mixing to minimize waste and lessen the overall operational costs.

Modutek’s chemical delivery systems integrate seamlessly with their wet bench technology, and can usually be used with wet benches from most other manufacturers. The company offers fully automated, semi-automated and manual wet processing equipment that can easily interface with its chemical delivery systems. These systems are flexible enough to also be used with existing wet bench equipment, whether made by Modutek or by other equipment manufacturers.

Modutek’s systems feature high safety and reliability with attention to excellent performance and quick changeovers. Cabinets are manufactured with double containment and double-walled plumbing is available along with leak detection and data logging. Modutek’s chemical delivery systems provide excellent repeatability and consistent results.

Modutek can easily customize its chemical delivery systems because all design and manufacturing work is done in house. The company has the expertise to evaluate customer requirements and make appropriate recommendations. Once the customer has decided on the system needed, Modutek’s engineers and technicians can make sure the equipment performs as expected and meets the specified operating parameters.

When customers ask Modutek to supply their chemical delivery system, the company can design and build exactly the customized system needed for the particular application. Facilities using chemicals can increase throughput while reducing chemical use. If you need an efficient and effective chemical delivery system to support your application contact Modutek for a free consultation or quote or email [email protected].