Process technology developments for GaAs ferroelectric nonvolatile memory

Abstract

Fabrication of nonvolatile memories utilizing ferroelectric polarization charge of lead zirconate-titanate (PZT) thin film capacitors requires the integration of the PZT capacitor process with the semiconductor device processes. This paper discusses the development of enabling process technology for integration of PZT capacitors with GaAs junction field-effect transistors (JFET) on a GaAs wafer for the fabrication of a GaAs ferroelectric random access memory (FERRAM). Individual processes for PZT capacitors and GaAs JFETs are described briefly first. The PZT capacitor process utilizes sol-gel deposition of PZT thin films, while the GaAs JFET process is based on selective ion implantations of silicon and magnesium directly into the GaAs wafer. The integration of these two chemically different processes has been accomplished through process innovations in the areas of sintering of PZT film, ion implantation in GaAs, interconnect metallization and patterning of this metallization. Successful operation of the nonvolatile memory cell has been demonstrated in a memory test circuit fabricated using this integrated process technology.