A method of forming a copper thin film by chemical vapor deposition, includes introducing a wafer into a chemical vapor deposition chamber; humidifying helium gas with water to form a wet helium gas for use as the atmosphere in the chemical vapor deposition chamber; depositing a copper seed layer at a wet helium flow rate of between about 5.0 sccm and 20.0 sccm during a wafer temperature rise from ambient temperature to between about 150° C. to 230° C.; and depositing a copper thin film layer at a wet helium flow rate of between about 0.2 sccm to 1.0 sccm and at a temperature of between about 150° C. to 230° C.