Highlights

PLZT Thin Films on Base Metallic Substrates

Scientific Achievement

High quality PLZT thin film capacitors were deposited on base metal substrates such as Copper and Nickel. These films exhibit comparable dielectric properties to films deposited on expensive Platinum-Silicon (Pt/Si) substrates. This was achieved by identifying the major factors that affect the dielectric properties and studying them by utilizing the SEM at EMC. The major factors that contribute to the superior properties observed in PLZT films deposited on Pt-Si substrates are the small grain size, absence of surface pyrochlore phases, lack of diffusion from electrode (Pt), and columnar growth of PLZT. All these factors are in fact directly related to the type of substrate used and are completely different for different substrates. In addition, for base metals, diffusion and oxidation of the substrates should also be considered. To mimic the conditions involved in the growth of high quality PLZT films on Pt-Si, thin films, electron microscopy was routinely carried out on films made on Ni and Cu to monitor the major factors. This helped us in altering the solution chemistry (excess lead content, chelating agent and ratio etc) and processing conditions (pyrolysis and crystallization temperature, time etc), to attain microscopically similar films on metallic substrates. An electrically conductive buffer layer (LNO) was used in case of Nickel to avoid diffusion and a reducing atmosphere was used in case of copper substrates to avoid oxidation. The experiments conducted with the SEM at EMC provided us with answers on how to vary the processing conditions to grow high quality PLZT thin films on Nickel and Copper.

Significance

The major achievement from this work was the development of a cheap and viable process to deposit high quality PLZT materials on base metallic electrodes for embedded capacitor applications. This work leads to a significant reduction in the costs involved to manufacture high quality capacitor materials by replacing the expensive Pt electrodes with cheaper nickel and copper electrodes, which are the common metals used in the Printed Circuit Board (PCB) industry. This process also has the added advantage of being easily integrated into any PCB manufacturing line without much modification to the existing processes as the electrode materials used are the same. Similar obstacles have to be overcome with the use of SEM when the scale of the capacitors is increased to levels that match the various applications.

This work resulted in the publication of six journal papers and four conference proceedings.

Performers

M. Narayanan, B. Ma, U. Balachandran (Argonne-ES); R. Koritala (Argonne-MSD)