Cleaning, an essential step when operating on the micro and nanoscale, is used to remove contaminants from the surface of the substrate before it is used in another fabrication process. This can be achieved through various methods, including the use of an ultrasonic bath or an asher. Ultrasonic baths use high-frequency sound waves to agitate a cleaning solution, effectively removing contaminants from the substrate surface. Ashers, on the other hand, use heat to remove unwanted material, such as photoresist. Both methods are often used to clean wafers, although ashers can also be used to selectively etch away material.