| AVS 58th Annual International Symposium and Exhibition | |
| Electronic Materials and Processing Division | Tuesday Sessions |
| Session EM+TF-TuM |
| Session: | High-k Dielectrics for MOSFETs Part 1 |
| Presenter: | Eric Bersch, University at Albany |
| Authors: | E.J. Bersch, University at Albany J.D. LaRose, University at Albany I.B. Wells, University at Albany S.P. Consiglio, TEL Technology Center, America, LLC R.D. Clark, TEL Technology Center, America, LLC K.N. Tapily, TEL Technology Center, America, LLC G.J. Leusink, TEL Technology Center, America, LLC A.C. Diebold, University at Albany |
| Correspondent: | Click to Email |
High-k HfO2-based gate oxides have recently been put into production in CMOS-based integrated circuits, and their future use in this capacity depends on how well they can continue to be downscaled. To this end, efforts to increase the dielectric constant (k) of HfO2-based gate oxides are ongoing. Recent work has shown that by tailoring annealing procedures, k values for HfO2 films of greater than 30 have been obtained.1 These higher k values for HfO2 occur for the metastable tetragonal and cubic crystalline phases, while the thermodynamically preferred monoclinic phase has a lower k value (~20). To evaluate the crystalline structure of ultra-thin (< 100 Å) HfO2 films which have undergone various annealing treatments, we used several techniques, including grazing incidence in-plnae X-ray diffraction (GIIXRD), X-ray and UV photoemission spectroscopy (XPS and UPS, respectively) and spectroscopic ellipsometry (SE). GIIXRD measurements showed that ~60 Å HfO2 films grown with a sequence of depositions and anneals (so-called DADA process2) were monoclinic, while those which were post deposition annealed (PDA) were in a mixture of monoclinic and either tetragonal or orthorhombic phases. Pole figure measurements of these films showed that the DADA film had a monoclinic (-111) fiber texture, while the PDA film was randomly oriented. For HfO2 films with thicknesses of ~25 Å, GIIXRD measurements showed that DADA films were tetragonal or orthorhombic, while PDA films were also tetragonal or orthorhombic, but also possibly with a monoclinic component. XPS and UPS measurements of the valence bands of HfO2 films were found to be useful in distinguishing between crystalline and non-crystalline films, but were not useful in distinguishing between crystalline phases.3 SE has been shown to be useful in indentifying crystallinity in HfO2 through a feature that appears in the HfO2 extinction coefficient curve at the absorption edge. We have observed this absorption edge feature for films that were crystalline and strongly monoclinic, but not for films that were only weakly crystalline or mostly non-monoclinic, in keeping with previous work.4
References:
[1] S. Migita, et al., 2008 Symposium on VLSI Technology, 152-153(2008).
[2] R.D. Clark, et al., ECS Trans., 35(4), 815-834 (2011).
[3] S. Toyoda, et al., J. Appl. Phys., 97, 104507 (2005).
[4] J. Schaeffer, et al., J. Electrochem. Soc., 150 (4), F67 (2003).