AVS 49th International Symposium
    Dielectrics Thursday Sessions
       Session DI+EL-ThM

Paper DI+EL-ThM10
XPS Study of Chemical Phase Separation in Amorphous Zr Silicate High-k Dielectrics

Thursday, November 7, 2002, 11:20 am, Room C-107

Session: Issues for Gate Dielectrics
Presenter: G.B. Rayner, North Carolina State University
Authors: G.B. Rayner, North Carolina State University
D.H. Kang, North Carolina State University
G. Lucovsky, North Carolina State University
Correspondent: Click to Email
X-ray photoelectron spectroscopy (XPS) was used to investigate chemical phase separation in pseudo-binary Zr silicate alloys, (ZrO@sub 2@)@sub x@(SiO@sub 2@)@sub 1-x@, deposited at 300C on Si substrates as a function of alloy composition, film thickness and subsequent annealing temperature. Based on previous infrared (IR) and x-ray diffraction (XRD) studies, it been shown that a chemical phase separation in (a) ZrO@sub 2@ and (b) SiO@sub 2@ with up to about 5 atomic percent ZrO@sub 2@ occurs in Zr silicate alloys when annealed at 900C in a non-oxidizing ambient such as Ar.. This separation is not accompanied by crystallization for silicate alloys with x~ 0.25, but crystallization of the ZrO@sub 2@ phase occurs for x> ~ 0.5. For Zr silicate films ~30 nm thick and x < ~0.6 the XPS O1s core level peak shapes are essentially unchanged for annealing temperatures to 500C. However, for annealing at 900C, the O1s core level peak splits into a distinct doublet with binding energies independent of alloy composition for 0.35 < x < 0.6. The peak at low binding energy, assigned to O@super 2-@ ions in the ZrO@sub 2@ phase, scales approximately linearly with composition. These results indicate a transition from silicate bonding, characterized by Si-O-Zr alloy bonds, into bonding characteristic of the end-member oxide phases, SiO@sub 2@ and ZrO@sub 2@. The XPS results presented here provide additional insights into local bonding that are complementary to what has been revealed previously in IR studies, as well as confirming the chemical phase separation that occurs for annealing temperatures > 900C in inert ambients. Included also are the results of a parallel study on the effect of chemical phase separation on the electrical performance of metal oxide semiconductor capacitors.