CHARACTERIZATION OF HIGHLY ORIENTED (110) TIN FILMS GROWN ON EPITAXIAL GE SI(001) HETEROSTRUCTURES/

The characteristics of epitaxial growth of titanium nitride films on G e/Si(001) have been studied. The growth of titanium nitride and german ium films on (001)Si was carried out in situ in a high vacuum chamber (<10(-7) Torr) using a multitarget stage in a pulsed laser deposition system. Electrical resistivity, stoichiometry, crystallinity, and epit axial relationships as a function of deposition temperature have been studied. Electrical resistivity of the titanium nitride films grown at deposition temperatures in the range of 450 degrees C-750 degrees C w as measured using a four-point probe. The stoichiometry of these films was investigated using Auger electron spectroscopy and Raman spectros copy. The crystalline quality and epitaxial nature of TiN films grown at different substrate temperatures were characterized using x-ray dif fraction and transmission electron microscopy. Highly oriented titaniu m nitride films with (110) orientation were obtained on Ge(001) film w hen the substrate temperature was maintained between 550 degrees C and 650 degrees C. The epitaxial growth of the titanium nitride films was found to be a function of two-dimensional or three-dimensional growth mode of germanium film on silicon (001) substrate. Titanium nitride f ilms grown at a substrate temperature of 650 degrees C exhibited the l owest room temperature resistivity (26 mu Omega-cm), highest nitrogen content (close to stoichiometry), and the best epitaxiality with the G e(001) films on Si(001). The epitaxial relationships for the TiN/Ge/Si (001) heterostructure are found to be [001]TiN \\ [110]Ge \\ [110]Si a nd [<(1)over bar 10>]TiN \\ [1(1) over bar0$]Ge \\ [1(1) over bar0$]Si . To explain the epitaxial growth in a large mismatch system (similar to 28%) such as TiN/Ge(001), the domain matching mechanism is proposed . Domains of size four (001)TiN by seventeen (<(2)over bar 20>)TiN in the titanium nitride film match closely with domains of size three (22 0)Ge by sixteen (<(2)over bar 20>)Ge in the germanium film, respective ly. The lattice matching epitaxy involving a 4% mismatch between Ge an d Si provides a mechanism for epitaxial growth of Ge on Si(001).