Ferroelectric (FE) materials exhibit spontaneous polarization making them particularly attractive for non-volatile memory and logic applications. Recently, doped hafnium oxide has shown to be ferroelectric in nature expanding its applications to these areas of interest. Ferroelectricity has been reported in atomic layer deposition (ALD) of HfO2 with Al, Y, or Si dopants. Previous work at RIT demonstrated functional ferroelectric field effect transistors (FeFETs) using silicon doped HfO2 (Si:HfO2) as the gate dielectric.
The new addition of a Savannah ALD system at RIT has made deposition of doped HfO2 films possible. Recipes have been developed for deposition of aluminum doped HfO2 using the hafnium precursor TDMAHf, tetrakis(dimethylamido)hafnium(IV), and the aluminum precursor TMA, trimethyl aluminum. Transmission electron microscopy (TEM) imaging and electron energy loss spectroscopy (EELS) were performed on the deposited Al:HfO2 films. TEM images verified that the target of a 10nm film was achieved. The separate Al layers could faintly be seen in TEM images of unannealed samples. Capacitors with the deposited Al:HfO2 were fabricated and tested. A small amount of ferroelectric behavior has been observed however with low breakdown voltage as well as high leakage current.
Gonta, Casey J.
"Atomic Layer of Deposition of Ferroelectric HfO2,"
Journal of the Microelectronic Engineering Conference: Vol. 22
, Article 14.
Available at: http://scholarworks.rit.edu/ritamec/vol22/iss1/14