Electroless copper seed layer

Electroless copper seed layer on TaN surfaces for Cu metallization in the back-end-of-line semiconductor fabrication was also investigated.38 After etching in diluted HF solution and activation with PdCb, the electroless deposition of copper (to be used as a seed layer) was carried out from CuSCVEDTA solution containing Triton X-100, tetramethyl ammonium hydroxide (TMAH), and formaldehyde as a reducing agent of Cu(II) ions. 

The damascene copper interconnects are produced by electrodeposition of copper onto PVD Cu seed layer. The electrodeposition of copper layer is carried out to fill in vias and trenches and consequently to form the metal interconnects. The bottom-up fill of copper in fine via holes as schematically presented in Fig. 4 has successfully been demonstrated by Wang et al.37 using the electroless deposition process. 

A method used to ensure the complete filling of vias is electroless plating of nickel. Electroless plating is a process to plate metal without electrical current involved. As a result, it eliminates the seed layer needed in electroplating. To plate nickel on copper, the copper surface must first be activated in a palladium chloride solution. This activation treatment allows palladium to bond to copper at certain sites so that the subsequent nickel plating can nucleate. 

---