Large-area pulsed-laser deposition of dielectric and ferroelectric thin films

The authors have developed a large-area pulsed-laser deposition (PLD) technique, suited in particular for depositing high-k dielectric and ferroelectric thin films of high quality on Si wafers of 8in. diameter. By using this technique, 42- and 6-nm-thick HfO2 films were deposited on 8 and 6in. Si wafers at room temperature, respectively. The standard deviations of thickness were 1.3% and 1.6% of their respective means. Cross-sectional transmission-electron microscopy pictures of the 6-nm-thick HfO2 film on Si showed that an interfacial layer between HfO2 and Si was thinner than 1nm. In order to measure the electrical properties, Pt top electrodes were deposited on the HfO2 film and the Al bottom electrode was deposited on the Si. Capacitance-voltage measurements of the Pt∕HfO2∕Si showed that the standard deviation of capacitances was as small as 1.9%. A ferroelectric SrBi2Ta2O9 (SBT) film was also deposited on a 4in. Si wafer at 400°C using the large-area PLD technique. The standard deviation of the SBT film thickness was 1.2% of 94nm, the average thickness. The large-area PLD technique the authors developed can meet the industrial needs for high and uniform quality over large-area high-k dielectric and/or ferroelectric thin films for large-scale integrated circuits.