Wet processes

Classical cleaning agents are liquid solvents or corrosive leaches and acids. Cleaning is usually done in immersion tanks, frequently supported by mechanical processes. Surface etching is done in the same way. The advantage of the wet process is the relatively fast cleaning and the high etching rate. However, all the cleaning and etching fluids without any exception are polluting and noxious. Expensive and labour-intensive processes are mandatory for storage, handling and disposal. Furthermore, the wet chemical processes require rework for chemicals removal as well as drying. Dry-chemical plasma processes exhibit none of these setbacks. Other huge benefits: In the low-pressure plasma, complete cleaning and etching even in the smallest cracks and undercuts can be achieved, accuracy practically to the atomic layer is ensured, and even ultra-fine residues are removed completely. However, the etching rates in dry-chemical processes are generally lower than in wet processes. For this reason, they must often by supplemented by wet processes for removal of thick layers.