Developing Ni–Al and Ru–Al intermetallic films for use in microelectromechanical systems
(Color online) Cross-sectional TEM images of films formed from annealed multilayers and cosputtering. (a) Ni/Al 30 nm modulation wavelength multilayer deposited by sputtering and annealed at for 4 h. (b) Ru/Al 25 nm modulation wavelength multilayer deposited by sputtering and annealed at for 193 h. (c) As-deposited NiAl cosputtered at 1.5 mTorr . Indexed diffraction patterns are shown in (d)–(f), which correspond to images (a)–(c), respectively. The diffraction patterns in (d) and (f) only have diffraction rings corresponding to NiAl (white), whereas many of the rings in (e) can be indexed as either RuAl (first number-blue) or Ru (second number-yellow). Rings that can be clearly identified as RuAl are the (100), (111), (200), and (310) planes, whereas there is only 1 ring that can be clearly identified as belonging solely to Ru, i.e., the (105) plane.
(Color online) Light microscope image of a NiAl film immersed in HF for 10 min. The film was deposited as a Ni/Al multilayer with a 25 nm modulation wavelength using e-beam evaporation. After deposition the film was annealed in a RTA for 10 min at , cooled to and held for 2 min, cooled to and held for 2 min, and then cooled to .
(Color online) NiAl film cosputtered at 1.5 mTorr Ar pressure and then exposed to HF for 10 min. The images represent different sections of the same sample: (a) as-deposited material, (b) higher magnification of the as-deposited NiAl, (c) annealed at for 10 min, and (d) annealed at for 1 min. In (c) and (d), the lighter gray represents areas of exposed substrate.
(Color online) (a) Ru/Al multilayer film annealed at and then immersed in HF for 10 min. The film is a 6.7 nm modulation wavelength multilayer annealed for 29 h. RuAl films cosputtered at 1.5 mTorr Ar pressure and then exposed to HF for 10 min: (b) as-deposited film, (c) film annealed at for 30 min, and (d) high magnification image of the film annealed at for 1min.
Patterned cosputtered NiAl and RuAl films on silicon after exposure to . The SEM images are for (a) 1.5 mTorr NiAl as-deposited, (b) 7.0 mTorr NiAl as deposited, (c) as-deposited RuAl cosputtered at 1.5 mTorr Ar pressure, and (d) RuAl deposited at 1.5 mTorr and annealed for 4 h at .
Annealed Ru/Al multilayer films deposited by sputtering and then exposed to . Both samples were annealed for 11 h at . The images shown are for (a) a 9.6 nm modulation wavelength film and (b) a 25 nm modulation wavelength film.
(Color online) Surface profile obtained from optical interferometry of an as-deposited RuAl film cosputtered at 1.5 mTorr and then etched with . The stress in the film is calculated as compressive.
(Color online) Representative light microscope images of cosputtered NiAl [(a)–(d)] and 30 nm modulation wavelength Ni/Al multilayer [(e)–(g)] resonators in the as-deposited condition (a) and after annealing for 4 h at [(b) and (e)], [(c) and (f)], and [(d) and (g)]. The cosputtered resonators annealed at were not etched as the resonators cracked and peeled after annealing. The scale bar in (a) applies to all of the images.
(Color online) Nomarski optical images of NiAl resonators from two different depositions conducted at 1.5 mTorr . Both samples are as deposited, but the film in (a) was deposited from two sequential depositions totaling 34 min and (b) was deposited from three sequential depositions for a total of 33.5 min. The samples were kept in vacuum for in between each sequential deposition.
(Color online) Representative images of resonators fabricated from cosputtered RuAl [(a)–(c)] and 25 nm modulation wavelength Ru/Al multilayers [(d)–(f)]. The resonators are shown in the as-deposited condition (a), after annealing for 4 h at (d) and [(b) and (e)], and after annealing for 1 min at [(c) and (f)]. The scale bar in (a) applies to all of the images.
(Color online) Light microscope images showing the range of motion of a thermal actuator as the current is ramped down from 70 to 0 mA. The actuator was fabricated from an as-deposited NiAl film that was cosputtered with an Ar pressure of 1.5 mTorr .
Resistivity and phases present for Ni–Al and Ru–Al films after annealing at . Numbers in parentheses are the standard deviation of 9 measurements. The phases present after annealing if known are indicated under the resistivity.
Summary of the results from the ruthenium and nickel aluminide resonator fabrication. All of the annealing were for 4 h except the annealing, which was for 1 min prior to annealing, the Ni/Al multilayers had a modulation wavelength of 30 nm and the Ru/Al multilayers had a modulation wavelength of 25 nm.
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