The etching operation is needed to obtain a surface finish free from any impurity.

Some characteristics of the installation

• mixture of phosphoric, nitric and hydrofluoric acids
  
• average etching rate : 0.5 µm/minute
  
• typical etching depth : from 10 to 250 µm
  
• evacuation and recycling unit of the toxic gase emissions and liquid effluents
  

Surface observation capabilities

• ultrasonic probe (local depth measurement)
  
• roughness meter
  
• optical microscope (×1000)