Paper AS-ThA4
Combined XPS/ISS/UPS Study of Ultra-thin HfO₂ films on SiO₂/Si Substrateso

Thursday, November 10, 2016, 3:20 pm, Room 101B

Hafnium oxide (HfO₂) films are often found in microelectronic devices, where they are used as gate dielectrics, for example. As device dimensions become smaller and smaller, it becomes necessary to make thinner HfO₂ films, which may only be a few nanometers thick. X-ray Photoelectron Spectroscopy (XPS) is an analysis technique which non-destructively provides chemical bonding information from the top few nanometres of a surface. It is the ideal technique to analyse the hafnium or silicon chemical bonding environment or to measure the thickness of these ultra-thin films. XPS cannot easily measure the coverage of ultra-thin films, however, but the complementary technique of Ion Scattering Spectroscopy (ISS) can be used for this purpose.

There is also a requirement for understanding the electronic structure of ultra-thin HfO₂ films. Ultraviolet Photoelectron Spectroscopy (UPS), using a helium discharge lamp for generate He(I) or He(II) photons (with energies of 21.2eV and 40.8eV, respectively), can be used to measure the work function of conductive films and to investigate valence electronic structure.

This talk will present data from XPS/ISS/UPS studies of a series of ultra-thin HfO₂ film films on SiO₂/Si substrates. The samples were created with varying numbers of ALD cycles, to generate HfO₂ films of different thickness and coverage. The results will demonstrate that using a complementary analytical approach, with all three techniques available on a single tool, provides a much more comprehensive analysis of the HfO₂ films than would be possible with only one analytical technique.