Descumming after Lithography
This process removes a small amount of resist in a very uniform way to facilitate vertical resist profiles and clean substrate surfaces. It is mainly used as a pre-step prior to plating or in combination with lift-off processing. In both these processing techniques, perfect resist profiles are required, otherwise the subsequent metallization process will suffer from adhesion problems.
Smaller wafer sizes can be processed economically in batch systems, as they are commonly used in the manufacturing of opto-electronics and SAW filters.
Depending on the requirement of removal amount and uniformity, special processes have been designed and tested, from a simple pure oxygen process to a multi-step process with different combinations of process gas.
Larger wafer sizes or more stringent requirements should be processed using single wafer systems, for instance in the sequence of the wafer bumping process.
The application to the right shows the descum process on a BCB layer using fluorinated chemistry. The Analysis of the surface condition reveals the better condition of the surface after the descumming process represented by the lower concentration of Carbon with less residual fluorine.