The present invention relates to compositions and a method for electroless formation
of alkaline-metal-free coatings on the basis of cobalt and composition of cobalt
with tungsten and phosphorus, which have high resistance to oxidation and stability
of electrical characteristics, when the CoCu system layer is used in IC
chips. The composition of the electroless solution contains more than one reducing
agents, one of which can catalyze the initial electroless deposition layer of cobalt
on copper (called initiator), while the other maintains deposition of cobalt on
the aforementioned initial layer as the process is continued. Small amount (100-5000
ppm) of elements from the initiator also builds into the electroless film, which
is expected to further improve the barrier properties of the resultant film compared
to the deposition bath without initiator. Such coating may find application in
semiconductor manufacturing where properties of deposited films and controllability
of the composition and physical and chemical characteristics of the deposited films
may be critically important.
