Comparison of thermal stability and chemical bonding configurations of plasma oxynitrided Hf and Zr thin films

In this work, we study the characteristics of plasma oxynitrided Hf and Zr thin films. A 5-nm-thick Hf or Zr metal film is deposited on the bare Si substrate, followed by plasma oxynitridation on these metal films in a N ₂O or NH₃ ambient. Incorporation of O and N leads to the formation of HfO_xN_y, and ZrO_xN_y films. The high nitrogen content in the HfO_xN_y films prepared by NH₃ plasma oxynitridation is found to increase the onset of the crystallization temperature, as compared to films prepared by N ₂O plasma oxynitridation. Nevertheless, the difference in crystallization temperature is not seen for ZrO_xN_y films. The interlayer (IL) between HfO_xN_y (or ZrO _xN_y) and Si is found to be thinner for the films with NH₃ plasma oxynitridation than those with N₂O plasma oxynitridation. However, the nitrogen incorporated by plasma oxynitridation appears to be depleted after rapid thermal oxidation annealing and is not effective to inhibit the growth of the IL. The activation energy of the IL growth for N₂O and NH₃ oxynitrided HfO_xN _y, is 0.23 and 0.13 eV, respectively. The activation energy of the IL growth for N₂O and NH₃ oxynitrided ZrO_xN _y is 0.19 and 0.14 eV, respectively.