New precursors for CVD copper metallization

A novel CVD copper process is described using two new copper CVD precursors, KI3 and KI5, for the fabrication of IC or TSV (Through Silicon Via) copper interconnects. The highly conformal CVD copper can provide seed layers for subsequent copper electroplating or can be used to directly fabricate the interconnect in one step. These new precursors are thermally stable yet chemically reactive under CVD conditions, growing copper films of exceptionally high purity at high growth rates. Their thermal stability can allow for elevated evaporation temperatures to generate the high precursor vapor pressures needed for deep penetration into high aspect ratio TSV vias. Using formic acid vapor as a reducing gas with KI5, copper films of >99.99 atomic % purity were grown at 250 degrees C on titanium nitride at a growth rate of > 1500 angstrom/min. Using tantalum nitride coated TSV type wafers, similar to 1700 angstrom of highly conformal copper was grown at 225 degrees C into 32 mu m x 5 mu m trenches with good adhesion. With ruthenium barriers we were able to grow copper at 125 degrees C at a rate of 20 angstrom/min to give a continuous similar to 300 angstrom copper film. In this respect, rapid low temperature CVD copper growth offers an alternative to the long cycle times associated with copper ALD which can contribute to copper agglomeration occurring. (C) 2008 Published by Elsevier B.V.