Impact of the Volatile Acid Contaminants on Copper Interconnects Electrical Performances

Abstract

The volatile acids impact on the via resistance of a Cu interconnect base structure was investigated by the intentional Cu-surfaces contamination with HF or HCl at a sensitive process step. The wafers acid contamination was performed from polluted FOUPs outgassing during a queue time step with or without an additional direct contamination in gas phase. Electrical results clearly shows that HF and HCl contamination on Cu surfaces at a sensitive step in the interconnects processing can lead to significant degradation of via resistances. The impact intensity appears to be dependent on the contaminant level and nature but also for HCl of the contamination moment (just after process or during q-time). Finally, from the data obtained, specifications of F or Cl threshold levels are proposed to control contamination both on Cu-surfaces and in FOUPs in order to avoid detrimental impacts in fab.

HF Transport Coefficients in Polymers Used for Microelectronic Applications

“…The HF cross contamination was clearly identified as one major root cause of Cu, Al or poly-Si corrosion or TiFx crystal growth on TiN layers [2,3,4]. To reduce wafer losses resulting from airborne contamination, the yield enhancement committee of the International Technology Roadmap for Semiconductors (ITRS) annually publishes a guideline to detail the tolerable concentrations for various airborne contaminants, including HF, in each technology node [4,5].…”