An ultra-thinning down to 2.6-μm using 300-mm 2Gb DRAM wafer has been developed. Effects of Si thickness andCu contamination at wafer backside in terms of DRAM yield and retention characteristics are described. Total thickness variation (TTV) after thinning was below 1.9-μm within 300-mm wafer. A degradation of retention characteristics occurred after thinning down to 2.6-μm while no degradationafter thinning down to 5.6-μm for both wafer and package level test were found. In-depth analysis such as stressvariations and distributions, and behavior of Cu diffusion from the back side of ultra-thinned DRAM wafer areevaluated using by TEM, EDX, TOF-SIMS, Positron annihilation spectroscopy (PAS), and μ-Raman spectroscopy.
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