Copper dual damascene interconnects with low-K (K/sub eff/<3.0) dielectrics using FLARE/sup TM/ and an organo-silicate hard mask

Reliable Cu dual damascene (D.D.) interconnects with low-K (K/sub eff/<3.0) that use organic material (FLARE/sup TM/; K=2.8) and methyl-silsesquioxane (MSQ; K=2.7) film have been developed. We successfully substituted the MSQ for the SiO/sub 2/ as inorganic dielectrics. The MSQ acts as a hard mask for etching the FLARE/sup TM/, an etch stop layer for forming a trench and a Cu CMP buffer layer. The substitution does not cause any damage or degradation to the interconnect system. The effect of reducing the effective dielectric constant is demonstrated by using a ring oscillator to measure stage delay time. It is improved by 33% in comparison with the Al/SiO/sub 2/ system.