Abstract: To remove a silicon nitride layer on a silicon wafer, phosphoric acid is applied onto the wafer in a sealed chamber. The phosphoric acid may be atomized and sprayed onto the wafer as a mist or aerosol. The wafer is heated to a processing temperature and then maintained at or near the processing temperature with a coating of phosphoric acid on the wafer. The heating and applying phosphoric acid are then stopped, the wafer is cooled, and then removed from the process chamber. An infrared radiating assembly above the processing chamber may project infrared radiation into the chamber to heat the wafer. The wafer may be cooled by optionally spraying de-ionized water and/or nitrogen gas onto the workpiece. A cooling assembly may be used to cool an infrared radiating assembly. Silicon nitride is rapidly removed using very small amounts of phosphoric acid, and without the risks and disadvantages of conventional hot phosphoric bath techniques.