New generation of reactive pre-clean prior to barrier–seed deposition to preserve ULK integrity

Advanced interconnects development requires introduction of porous ultra low k (ULK) dielectrics enhancing product performance through parasitic capacitance reduction. ULK layers are characterized by higher carbon content and lower mechanical properties due to porosity increase. Consequently, ULK dielectrics are more prone to be damaged during plasma treatment in interconnects build [1]. Pre-clean processes prior to barrier/seed deposition are a potential area of concern for ULK integrity.Reactive pre-clean processes based on He/H2 plasma are investigated in this paper through two types of hardware. The new pre-clean chamber is an upgrade of conventional pre-clean hardware and combines optimized H2 plasma and active wafer temperature control to ensure efficient copper oxide reduction [3] and via cleaning. The aim of the paper is to evaluate performance of the new generation of reactive pre-clean compared to conventional hardware.To overcome ULK dielectric integration challenge, pre-clean processes need to ensure efficient copper oxide reduction and via bottom cleaning with minimum impact on ULK material properties. The “new reactive pre-clean” addresses these requirements for k = 2.5 ULK materials. The new reactive pre-clean demonstrates a robust process window over a wide range of temperature and pressure settings for all characterized aspects. The “new reactive pre-clean” technology is seen to be a promising pre-clean candidate for next generation of porous ULK dielectric material (k ≤ 2.5) integration for 28 nm node and beyond.

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