Improving the KOH Etching Using Teflon Tanks

Etching with potassium hydroxide (KOH) is commonly used for general purpose etching of silicon wafers. It’s because the process can be tightly controlled, and it is also relatively safe. KOH etching, when done using Modutek’s Teflon tanks, improves the performance through high control accuracy and tight temperature control features on the tank.

The KOH rate is affected by many factors: 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 unmasked parts of the silicon wafer. 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 leads to an increased etch rate. The KOH concentration can range from about 10% to 50% but is typically around 30% by weight. KOH etching is designed to work with a fixed concentration that is determined at the start of the process and remains in that condition once etching begins.

During the process, the etch rate is controlled through temperature by operators. KOH etching reacts quickly to the temperature changes and the solution temperature can be used to control etching and influence the dimensions of the etched shapes.

Keeping the temperature constant maintains the different etch rates in different directions constant. Changing the temperature also changes the different etch rates and can influence etched shapes. This is why temperature control is crucial in precise KOH etching. A rapid and precise temperature control system can improve KOH etching performance.

Modutek’s Teflon tanks improve KOH etching through tank features such as tight temperature control and high control accuracy. Teflon tanks are designed to eliminate contamination and heated tanks are also available in a circulating design or with an immersion heater in the overflow weir. The tanks are available in standard sizes, but Modutek can manufacture custom sizes as well.

For more details read the complete article, “Improving the KOH Etching Process Using Teflon Tanks.” Contact Modutek to get a quote or consultation on using Teflon tanks as well as other equipment for your manufacturing requirements.

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