Fabricaiton and Testing of Micron Size (Pb,La)(Zr,Ti)O[sub(3)] Thin Film Capacitors

Recently, research and development of ferroelectric thin film materials and devices have had a strong resurgence, primarily because of their potential use as non-volatile random access memories 1 "4. In non-volatile memory applications, ferroelectric thin films are being considered for incorporation onto the complementary metal-oxide semiconductor (CMOS) architecture in a 1 capacitor/ 1 transistor structure. Conventionally, ferroelectric thin films are deposited on Pt coated Si wafers with Pt top contact electrodes to form the capacitor structure. Such non-volatile memories have a destructive readout mode in order to retrieve stored data. This consideration led to extensive work on reliability issues of ferroelectric, mostly lead zirconate titanate (PZT), thin film capacitors such as fatigue, aging and retention relevant to integration onto CMOS drive circuitry^-10

Recent studies have shown that metal oxide electrodes yield better fatigue characteristics than conventional Pt electrodes for PZT thin film capacitors11-14 Those conducting metal-oxides include YBa2 Cu3 0 x, (La,Sr)Co03 (LSCO) and Ru02. Among the oxides, the cubic perovskite (La,Sr)Co03 has been shown to have desirable metallic properties^ and more importantly, capacitors with LSCO top and bottom electrodes exhibited excellent ferroelectric p er fo rm a n ces'll. in our earlier report, we addressed the issue of growth and reliability testing of high quality LSCO/PLZT/LSCO ferroelectric

capacitors on LaAlC>3 , yttria stabilized zirconia (YSZ) buffered Si and SiO^Si1 .^ Ferroelectric testing in these experiments was typically carried out by depositing 50-100 pm diameter Au/Pt dots to delineate the capacitors. However, for the integration of the capacitors into high density memories, the ferroelectric capacitors are required to have a lateral dimension commensurate with the scale of the high density memories. For example, for architectures similar to planar dynamic random access memories, a 1 Mbit memory would require a ferroelectric capacitor size in the range of 2x2 - 4x4 pm 17.