Home » Semiconductor » Opinion: Exploring Automated Single-Wafer Ashing of Compound Semiconductors

Robotic handling protects wafers while superior temperature and process control provides complete, precision ashing.

Ashing, in which the light–sensitive coating known as photoresist is removed and cleaned from an etched wafer, is one of the most important and frequently performed steps in chip fabrication. In this step, photoresist organics are “burned off” using a processing tool in which monatomic plasma is created by exposing oxygen or fluorine gas at low pressure to high–power radio waves. Previously, wafer ashing was largely done using batch–processing techniques to achieve the required throughput.

However, unlike silicon semiconductors, in which wafers are mass–produced in a standard 300–mm size, compound semiconductors are made of silicon carbide, gallium nitride, gallium arsenide, and sapphire, which can vary from 100 to 200 mm. When this is the case, significantly better uniformity of photoresist removal is required, which means better temperature and process controls. As a result, most compound semiconductor wafer manufacturers require automated, single-wafer–processing tools capable of fast ashing rates and high production levels.

Today, semiconductor manufacturers are increasingly looking for a single-wafer–ashing solution for both high–temperature photoresist removal and precision descum.

10/17-19 EAC