PB-DIFFUSION BARRIER LAYERS FOR PBTIO3 THIN-FILMS DEPOSITED ON SI SUBSTRATES BY METAL-ORGANIC CHEMICAL-VAPOR-DEPOSITION

The interfaces between metal organic chemical vapor deposited PbTiO3 thin films and various diffusion barrier layers deposited on Si substrates were investigated by transmission electron microscopy. Several diffusion barrier thin films such as polycrystalline TiO2, amorphous TiO2, ZrO2, and TiN were deposited between the PbTiO3 thin film and Si substrate, because the deposition of PbTiO3 thin films on bare Si substrates produced Pb silicate layers at the interface irrespective of the deposition conditions. The TiO2 films were converted to PbTiO3 by their reaction with diffused Pb and O ions during PbTiO3 deposition at a substrate temperature of 410 degrees C. Further diffusion of Pb and O induces formation of a Pb silicate layer at the interface. ZrO2 did not seem to react with Pb and O during PbTiO3 deposition at the same temperature, but the Pb and O ions that diffused through the ZrO2 layer formed a Pb silicate layer between the ZrO2 and Si substrate. The TIN films did not seem to react with Pb and O ions during the deposition of PbTiO3 at 410 degrees C, but reacted with PbTiO3 to form a lead-deficient pyrochlore during postdeposition rapid thermal annealing at 700 degrees C. However, TIN could effectively block the diffusion of Pb and O ions into the Si substrate and the formation of Pb silicate at the interface.