Oxygen plasma processing uses O2 gas excited into a plasma state to react with and remove organic materials from wafer surfaces in semiconductor manufacturing. The primary application is photoresist stripping (ashing), where oxygen radicals (O) and ions react with the carbon and hydrogen in organic resist films to form volatile CO, CO2, and H2O that are pumped away. Oxygen plasma ashing is performed after pattern transfer etching is complete and the resist mask is no longer needed. Ashing can be conducted in dedicated strip chambers using downstream microwave or RF plasma sources that generate abundant O radicals with minimal ion bombardment (to avoid substrate damage), or in-situ within the etch chamber using higher-pressure, lower-bias conditions. Typical ash rates for organic photoresist range from 1-5 Ξm/min depending on power, pressure, temperature, and resist composition. Ion-implanted resist forms a hardened carbonized crust that is more resistant to ashing and may require multi-step strip processes with temperature ramping or wet chemical supplements. Beyond stripping, oxygen plasma serves other important functions: surface cleaning to remove organic contaminants before critical depositions, surface activation to improve wettability and adhesion, and descum processes to remove thin residual resist from pattern features after development. In etch applications, small amounts of O2 are added to fluorocarbon or HBr plasmas to control the etch-passivation balance â oxygen reacts with carbon-containing polymer deposits to modulate sidewall passivation thickness and influences etch selectivity. Oxygen plasma treatment can also modify surface energy, improve bonding in wafer-to-wafer bonding processes, and functionalize surfaces for subsequent chemical treatments. Care must be taken to avoid excessive oxygen plasma exposure on sensitive materials such as low-k dielectrics, which can undergo carbon depletion and dielectric constant degradation.