Cross-Contamination during Ferroelectric Nonvolatile Memory Fabrication

Abstract

New metal contaminants, such as Pb, Zr, and Ir, introduced during ferroelectric nonvolatile memory (FeRAM) fabrication are of great concern because of their potentially adverse effects on complementary metal oxide semiconductor device characteristics. Numerous routes for cross-contamination exist in a Si wafer fab. In this study, we focus on the transfer of elements between the contaminated wafer handling system of a typical shared tool and the back 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 films, clean wafers that were subsequently run through the tool acquired a maximum of and of Pb, Zr, and Ti, respectively. After exposing the tool to Ir films, significantly less Ir transferal was observed In all cases, cycling a series of clean wafers through the tool led to a rapid decrease in the quantity of transferred contaminants, and was the most effective method for eliminating these elements altogether. Moreover, the Pb, Zr, Ti, or Ir contaminants transferred in this way were easily removed using a traditional pregate surface cleaning process. © 2001 The Electrochemical Society. All rights reserved.