418 Madsen, Weaver, Ljungcrantz, and Clark 418 Regular Issue Paper Journal of Electronic Materials, Vol. 27, No. 5, 1998 INTRODUCTION During the last decade, the use of ferroelectric (FE) material for random access memory elements has reached commercial applications in the semiconduc- tor industry. 1 This nonvolatile technology has the potential to replace any or all memory cells with one standard cell. Both nonvolatile and dynamic random access memories (NV-RAM and DRAM) are under development. It is sufficient to say that the former relies on the material’s ferroelectric properties, while the latter utilizes the high dielectric property. (Received April 1, 1997; accepted December 22, 1997) Analysis of the Stress and Interfacial Reactions in Pt/Ti/SiO 2 /Si for Use with Ferroelectric Thin Films LYNNETTE D. MADSEN, 1,2 LOUISE WEAVER, 3 HENRIK LJUNGCRANTZ, 1,4 and ALISON J. CLARK 5,6 1.—Thin Film Physics, Linköping University, S-581 83 Linköping, Sweden. 2.—Materials Science and Engineering, McMaster University, Hamilton, Ontario, Canada, L8S 4M1. 3.—Materials and Metallurgical Engineering, Kingston, Ontario, Canada, K7L 3N6. 4.—Present address: TIXON AB, Svedeng. 2, S58273 Linköping, Sweden. 5.—Northem Telecom Electronics Limited, P.O. Box 3511, Station C, Ottawa, Ontario, Canada, K1Y 4H7. 6.—Present address: Physics, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1 The microstructure of the Pt/Ti/SiO 2 /Si structure has been investigated by scanning and transmission electron microscopy. Pt films of 100 nm thickness deposited by sputtering or evaporation onto unheated substrates gave complete coverage of the underlying Ti layer and showed a granular and faceted structure with grains ~20 nm in diameter. They did not exhibit hillocks or surface TiO x formation. X-ray diffraction was used to examine the film stress through use of the sin 2 ψ method with bulk values for the elastic constants (ν = 0.39, E = 162 GPa). The as-deposited sputtered film had a compressive stress of ~540 MPa, while the evaporated films had tensile stresses of ~630 MPa. The films then received a 400°C rapid thermal anneal (RTA) for 90 s and a subsequent RTA of 650°C for 30 s. Further investigation of the film stresses and microstructure were made after each annealing step. After the low temperature anneal, the film stress for the sputtered film became tensile. Plan-view sections examined by transmis- sion electron microscopy (TEM) showed that the as-deposited sputtered films were dense but became porous after annealing. Initially, the evaporated films had a less dense microstructure, but were more stable with annealing. Little change in the stress for the evaporated film was observed after this initial low temperature annealing step. Additional annealing of the evaporated and sput- tered samples caused complete consumption of the Ti layer including some TiO x formation from the underlying SiO 2 layer and marked interaction with the Pt; however, little change in the stress was found. The surface of the Pt film revealed larger grains, but otherwise remained unaffected. The underlying phase changes were minimized once the Ti layer had reacted with the Pt. Due to the ratio of the layers, Pt:Ti of 2:1, the surface of the Pt was unaffected. Key words: Barrier, electrode, PZT, scanning electron microscopy (SEM), stress, XRD Pb(Zr,Ti)O 3 (PZT) is one of the favored FE materials for memory applications in the semiconductor field. Deposition of PZT thin films has been achieved by electron or ion beam deposition, 2,3 sputtering tech- niques, 4–7 sol-gel methods, 8,9 laser ablation 10–12 and chemical vapor deposition (CVD). 13–15 To form a nonvolatile memory cell, a capacitor structure using FE material as the dielectric, is formed over the semiconductor layers normally used for a metal-oxide-semiconductor field-effect transistor (MOSFET). 16 The deposition process and associated annealing (typically ranging from 500–750°C) along with the oxygen content of the PZT, places restric- tions on the electrode materials which can be used. To