Electroless copper employing hypophosphite as a reducing agent

摘要

Method and baths for electroless depositing Cu on a semiconductor chip using four preferred Cu electroless baths. All four preferred electroless baths use hypophosphite as a reducing agent. The 4 baths use the following mediators (1) Nickel sulfate, (2) Pd Sulfate (3) Co Sulfate (4) Fe Sulfite, and complexing agents (Na Citrite, Boric Acid, Ammonium Sulfite). The baths can operate at a pH between 8 and 10. The invention forms high purity Cu interconnects having adequate step coverage to form in a hole having an aspect ratio greater than 2.7 to 1.