Cross-contamination during ferroelectric nonvolatile memory fabrication

New metal contaminants, such as Pb, Zr, and Lr, introduced during ferroelec tric nonvolatile memory (FeRAM) fabrication are of great concern because of their potentially adverse effects on complementary metal oxide semiconduct or device characteristics. Numerous routes for cross-contamination exist in a Si wafer fab. In this study, we focus on the transfer of elements betwee n the contaminated wafer handling system of a typical shared tool and the b ack side of clean wafers. Specifically, the potential for transferring Pb, Zr, Ti, and Ir from a contaminated surface to clean wafers was investigated . It was found that, after exposing a robotic handler and chuck directly to the surface of Pb(Zr,Ti)O-3 films, clean wafers that were subsequently run through the tool acquired a maximum of 1.1 X 10(11). 9.0 x 10(10), and 5.1 X 10(10) atoms/cm(2) of Pb, Zr, and Ti, respectively. After exposing the t ool to Ir films, significantly less Ir transferal was observed (1.0 X 10(9) atoms/cm(2)). In all cases, cycling a series of clean wafers through the t ool led to a rapid decrease in the quantity of transferred contaminants, an d was the most effective method for eliminating these elements altogether. Moreover, the Pb, Zr, Ti, or Ir contaminants transferred in this way were e asily removed using a traditional pregate surface cleaning process. (C) 200 1 The Electrochemical Society.