How the Silicon Nitride Wet Etching Process Is Improved by Modutek

Silicon nitride is used as a mask when etching silicon wafers as part of the semiconductor manufacturing process. Before the silicon wafer goes to the next fabrication steps, the silicon nitride needs to be removed from the wafer surface using a solution of DI water and phosphoric acid.

To optimize the silicon nitride wet etching process, the phosphoric acid solution is kept at a high temperature. This means some of the DI water boils off as steam and must be replaced. Adding water to the phosphoric acid is extremely dangerous as it can explode. Keeping the solution at a constant temperature is essential for accurate control of the stripping process.

Modutek has made significant improvements to both the safety and the control of the nitride wet etching process with its Nb series silicon nitride wet etching baths. Here, the heater that boils the solution is always switched on, which leads to the solution being heated up to the boiling point and further heating will not increase the temperature, just the boiling rate.

Just in case the temperature increases, a thermocouple in Modutek's bath gives the signal that the DI water should be added. Then, the DI water is added slowly to the boiling solution (since the acid boils rapidly) to make sure that it's mixed in immediately and doesn't form a water film on the solution's surface. If the water is added to the solution too quickly, the water film will form and mix itself with the acid, which leads to a very strong reaction and an explosion is possible.

This control strategy employed in Modutek’s system ensures the temperature of the solution is always maintained at its boiling point.Modutek’s silicon nitride wet etching baths also have additional safety features which ensure that no water is added if the solution is not boiling. Using its advanced control system with additional safety interlocks, Modutek has improved the accuracy, control and safety of the silicon nitride wet etching process.

For more details read the complete article titled “How the Silicon Nitride Wet Etching Process Is Improved by Modutek”. If you have questions or would like further information, please call Modutek at 866-803-1533 or email to modutek@modutek.com. 

How the KOH Etching Process is Improved Using Modutek's Teflon Tanks

Among the various approaches that foundries use to manufacture semiconductors chips, the use of the KOH (potassium hydroxide) etching process is frequently preferred due to the error-free mass production capability it provides. Etching with potassium chloride (KOH) provides more precision and results to better quality control compared to dry semiconductor etching processes that present challenges in process control.

The fluids employed in the KOH etching process are stored in Teflon tanks built within the equipment – these tanks can make KOH etching more cost-effective, more practical and safer than other alternatives available. It’s also possible to structure the KOH etching process in a manner that will create an easily repeatable manufacturing process. When projects come in from different clients, fabrication plants can focus on setting up the equipment and process lines and worry less about safety and reliability issues.

One of the most significant improvements that Modutek brings to the KOH etching process is customized control. Modutek’s tanks have highly customizable temperature settings – temperature control can be achieved either through in-line heating and cooling equipment installed, or through immersion in liquid tanks. Temperature can be adjusted between 30°C to 100°C and changes can be adjusted at a rate of 2°C per minute on average depending on tank size.

Modutek designs Teflon tanks according to the specifications of each client’s installation. Whether a manufacturing facility needs recirculating baths for KOH etching processes or temperature controlled static baths, Modutek's Teflon tanks provide optimum control to reduce water loss and concentration deficiency.

For more details read the complete article titled How the KOH Etching Process is Improved Using Modutek’s Teflon Tanks. Call Modutek at 866-803-1533 if you have questions or would like a quote or email to Modutek@modutek.com.