Monthly Archives: March 2020

Why You Need a Wet Bench Manufacturer with In-House Expertise

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As semiconductor manufacturing becomes more complex, there is an increasing demand for custom solutions to special applications. Standard systems often can’t take into account the combination of multiple steps required to produce an etched silicon wafer. Instead they end up creating inefficiencies with poor quality output. Custom solutions can consider each separate requirement and can assemble a production line in which each step is optimized for peak performance. Wet bench manufacturers best situated to satisfy the need for customization are those with in house expertise and those that manufacture the bulk of their equipment themselves.

In House Expertise Leads to Optimized Custom Designs

When a company has extensive experience as a wet bench manufacturer, it can evaluate special application requirements, identify key features that will be needed and use its expertise to design the corresponding equipment. The etching and cleaning processes to be used, the concentrations of chemicals, the timing of steps and the use of automation all impact the design of individual elements and of the complete production line. Companies that have designed many such systems will immediately know what design parameters are appropriate and proceed to the details of the customization.

A company has typically acquired its in house expertise by designing many different systems and gaining experience with the features included in each one. The design experience and data gained from testing and from customer feedback allow the company to design an optimized system without going through a trial and error phase. The result is a design based on real wet process results and one that can be built and put into operation without extensive corrections and modifications.

Custom Manufacturing Requires In-House Capabilities

Once a custom design is in place, the corresponding equipment has to be built. The complete customization process is extremely efficient when design and manufacturing take place within the same company. The supplier with in-house expertise in both design and manufacturing of wet bench equipment can use manufacturing experience to produce a low cost and easily constructed design. The company can then build the equipment to perform exactly as needed.

In house manufacturing means the company has experience with materials, knows the limitations of manufacturing processes and is aware of the capabilities of tools and equipment. Based on experience with equipment that has gone into production, a company with in house design and manufacturing expertise can offer custom solutions that really work.

In House Design and Manufacturing Leads to Effective Customer Support

Wet bench manufacturers that design and build their own equipment can provide customer support and service that quickly answers questions and solves problems. Engineers and technicians that have worked on the equipment and are familiar with it won’t have to check with third party suppliers and will be able to propose effective solutions. Companies with such in-house expertise can not only prioritize excellent customer support but can also deliver concrete results.

Modutek Has In House Design and Production Expertise

Modutek’s personnel design and build all their own equipment including design and programming of automation software. The company’s in house expertise and production know-how includes design, assembly and testing of all wet bench equipment supporting both acid and solvent applications. While the company has a complete line of standard equipment and systems, it’s in house capabilities allow it to offer customized solutions for any special applications.

Modutek has technicians and engineers familiar with electrical schematics, plumbing diagrams and software documentation. Company programmers write the automation software for semi-automatic and fully automated wet bench stations. Modutek’s in house expertise allows the company to provide the best possible designs, equipment and customer support.

Improving the KOH Etching Process Using Teflon Tanks

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Etching with potassium hydroxide (KOH) is commonly used for general purpose etching of silicon wafers because the process can be tightly controlled and because it is relatively safe. During the process, the etch rate is controlled through the temperature. When KOH etching is done using Modutek’s Teflon tanks, performance can be improved through tank features such as tight temperature control and high control accuracy.

Controlling the KOH Etching Process

The KOH etch rate is affected by solution concentration, lattice orientation, doping and solution temperature. The silicon wafer is masked with a substance such as silicon nitride, which is impervious to KOH. The solution etches the parts of the silicon wafer that is not masked and a combination of the measures that affect the etch rate allows operators to etch complex shapes that are used in electronic circuits and microstructures.

A higher concentration results in an increased etch rate. The KOH concentration can range from about 10 percent to 50 percent but is usually around 30 percent by weight. KOH etching is designed to work with a fixed concentration that is determined at the start of the process and is not changed once etching is under way.

The silicon wafer crystal lattice has different atom densities in different directions, with atoms closer together in some directions than in others. As a result, KOH etches at different speeds in the different directions or lattice orientations. When designing the shapes to be etched, the silicon crystal can be placed in an orientation that produces deeper or longer etching in certain directions, giving designers control of the etched shapes.

Designers can also stop KOH etching in specific directions by doping the silicon crystal with boron. Used with the other measures influencing KOH etching, boron doping completes the initial conditions used to create shapes in the silicon wafers. Masking, concentration, lattice orientation and doping are set up to produce the desired shapes before the process begins.

Temperature Control is Key to KOH Etching

Once KOH etching is under way, temperature control lets operators affect the etch rate during the process. KOH etching is sensitive to temperature changes and the solution temperature can be used to control etching and influence the dimensions of the etched shapes. Keeping the temperature constant keeps the different etch rates in different directions constant as well. Changing the temperature changes the different etch rates and can influence etched shapes. For example, if an etching direction has been blocked by boron doping, different etch rates in the remaining directions will result in different etched shapes.

As a result, temperature control becomes critically important for precise KOH etching. Ideally, the solution heats up quickly to a set temperature and stays exactly at that temperature until the set point is changed. The solution then quickly heats up to the new temperature and again maintains it accurately. A rapid and precise temperature control system can improve KOH etching performance.

How Modutek’s Teflon Tanks Improve KOH Etching

Modutek’s Teflon tanks are designed to eliminate contamination by using an all-Teflon liquid path design. The heated tanks are available in a circulating design or with an immersion heater in the overflow weir. Standard sizes are available but Modutek can build custom sizes for special applications as required and can fit new tanks into existing wet bench equipment.

Modutek’s tanks feature an advanced temperature control system ideal for improved KOH etching. The tank heating system has a 30 to 100 degree centigrade operating range and the heating rate is 2 to 3 degrees centigrade per minute, depending on the size of the tank. Process temperature control is accurate within plus/minus 0.5 degrees centigrade and the temperature controls are accurate from batch to batch. With Modutek’s Teflon tanks, silicon wafers etched with the KOH process are uniform, resulting in high output quality. Overall facility performance can be improved and component defects reduced. Contact Modutek for a free consultation or quote on Teflon tanks or other equipment designed to meet specialized manufacturing requirements.