Lift-off masking processes

With the application-specific arrangement of sensors in the backend area of wafer processing mask techniques are frequently required, which enable structuring of various layers without wet chemical or dry etching processes on the one hand as well as high selectivity and resolution on the other. Thin metallisation layers, metallic multiple layers (such as under bump metallisation of Ti-Ni-Au, Ti-Pd-Au etc.), precious metals or silicides often have to be structured. This functional structuring should take place in the batch process if at all possible.

  • For sophisticated lift-off techniques a two-layer resist system has been developed. The “undercut” of the enamel edges can be adapted to the structuring layout and material at the development stage.

 

 



  • The lift-off mask can be easily removed with acetone or a special remover without residue. Another process can take place if need be before lifting off such as a bump deposition.
    Depending on the undercut aimed for, structures with a resolution of approx. 3 … 10 µm can be achieved.
  • For other applications a simple and low cost manufacturing process for lift-off masks has been developed based on inlay lift-off systems.
    For different structuring tasks within the microsystem technology an inlay lift-off system with a minimal resolution of approx. 5 µm has been developed.

 

 

  • The lift-off process can be carried out with acetone at room temperature within a few seconds. Thin metal and precious metal layers with a thickness of less than 30 nm can be lifted within 20 seconds.

 

 

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