Effect Of The Base Pressure And Residual Gases On The Properties Of The Metal Film Deposition

Metal film deposition is an important step in the IC manufacturing process. With the scale-down of integrated circuit feature size and the requirements of specific process such as power device, metal film deposition becomes more and more sensitive to base pressure and impurities incorporated from residual gases, especially, for sputtering process of high temperature thick aluminum. The tiny variation of process chamber microenvironment can lead device failure.The tiny variation of vacuum microenvironment cannot be detected timely in practical mass production. The base pressure, leak rate and other process parameters are within baseline and specification. There are difficulties in tracing the machine condition then when the abnormal product occured accidentally. This paper analyzes the effect of chamber light leakage and residual gases on the properties of the metal film by sputtering and W-CVD tools, another object is to find improvement methods in order to improve yield and productivity.Through case studies, the leakage and light impurities in vacuum chamber have a signilcant impact on the properties of metal film, include:(a)In Endura? SIP(Self Ionized Plasma) Ti/TiN sputtering system ,the presence of residual gases after preventive maintenance can alter the properties of sputtered film and cause the tungsten etch back EPD(End Point Detection) curve abnormal. Optimization target burn in recipe and baking shutter disk in oven prior to installation can reduce the effect on etch EPD;(b)In high temperature thick aluminum sputtering process, chamber light leakage can cause the Volcano and whisker like defect; (c)The light impurities or residual gases can cause threshold voltage shift of some power MOSFET device. Optimization baking procedure of process kits can alleviate the the effect of residual gas; (d)The light leakage of W-CVD vacuum chamber was identified as the residue particle source after subsequent tungsten etch-backIt is important to lower base pressure as well as limiting the residual gases .Furthermore, the paper proposed some solutions to improve the vacuum and reduce residual gases from the point of view of hardware. These solutions have been evaluated and successfully applied in mass production, these solutions can also obviously reduce the tool downtime, reduce product defects and improve chip yield.