This paper describes an acid-based electroless Cu deposition system employing CuCl2-HNO3 chemistry in a HF-NH4F buffer solution. With the help of nitric acid, Cu can be deposited on SiO2/Ta/TaN substrate without the insertion of a Cu seed layer. The deposition rate is found to decrease with increasing [HNO3] in the solution. The roles of [NO3-], [F-], [Cl-], [NH4-], Si, and TaN in the system are identified based on split experiments. Si acts as the reducing agent while [F-] and [Cl-] ions form complexions with and transmit electrons to Cu2+. Overall, a deposition rate of 2700 Angstrom /min with a Cu resistivity of 2.35 mu Omega cm can be achieved.