How New Equipment Has Improved the Silicon Nitride Wet Etching Process

The silicon nitride wet etching process uses phosphoric acid to remove silicon nitride masks from silicon wafers to allow clean wafers to undergo the next fabrication steps. This process is difficult to control because the hot phosphoric acid and water mixture is unstable and that requires the periodic addition of small quantities of water in order to achieve optimum etching performance. However, adding water to phosphoric acid may result in a reactive bump. Modutek has developed a new approach that controls the nitride etching process more accurately and safely while at the same time achieving high etching rates.

Since Silicon nitride is a key component to semiconductor wafer manufacturing, Modutek has developed the new Nb series Silicon Nitride Wet Etching Bath. It provides a tighter control of the bath temperature while guaranteeing safe operations and superior etching of the silicon nitride masks.

Modutek’s silicon nitride wet etching process uses the acid mixture concentration as a reference value for adding small amounts of DI water. The boiling point of the mixture depends on the concentration, but in a normal operation, the typical mixture point is 160 degrees centigrade. When water is lost, the mixture concentration starts to rise above 160 degrees centigrade. DI water is added into the boiling acid, and the concentration of the acid is reduced bringing the temperature back to 160 degrees centigrade.

Modutek's Silicon Nitride Wet Etching Bath has the thermocouple sensor which detects the presence of steam. It closes the water valve when there's no longer steam to prevent the further addition of water to the boiling acid. This additional safety feature is designed to prevent dangerous situations as a result of mixing large amounts of water and the hot phosphoric acid.

For more details about Modutek’s silicon nitride wet etching baths and the results customers have achieved in using them read the complete article “How New Equipment Has Improved the Silicon Nitride Wet Etching Process”. If you would like to learn how Modutek’s silicon nitride wet etching bath can be used for your application, call Modutek at 866-803-1533 or email Modutek@Modutek.com.