3-1 Introduction
For evaluating mechanical, electronic, chemical and physical properties of the a-C:F films, seventeen metrology tools were used to analyze them. The OES was used to detect the radicals of deposition plasma. The TDS was used to test the thermal stability of a-C:F films from 25℃ to 1050℃. The AFM and nano-indentor were used to detect the morphology and hardness of a-C:F films, respectively. The field emission scanning electron microscope (FESEM) was used to measure the thickness of a-C:F films. The composition and chemical states of the a-C:F films were analyzed by Glow Discharge Spectrometer (GDS), Fourier-Transform infrared (FTIR) Spectrometer and X-ray photoelectron spectroscopy (XPS).
The microstructure was evaluated by High-Resolution Transmission Electron Microscope (HRTEM). The sp2/sp3 bond ratio was obtained through high-resolution electron energy-loss spectroscopy (HREELS, Gatan, GIF 2000). The Electron Paramagnetic resonance (EPR) equipment was used to observe the dangling bound density in a-C:F films.
Current-voltage (I-V) measurements were obtained by the HP4156, and the capacitance (C-V) characteristic was measured at a frequency of 1MHz using the HP4280. The n&k Analyzer, UV-Visible Spectrophotometer
(UV/VI), Photoluminescence (PL), Photoluminescence (PL), and Pulse Laser were used to evaluate the optic properties of a-C:F films.
3-2 Analyses and Measurements Techniques
3-2-1 Optical Emission Spectroscope (OES)
The OES was applied to characterize the composition of the plasma.
The plasma precursor is diagnosed by using OES in the visible light range (200 ~ 800 nm) and Princetron Instrument Inc. Model ST121. Optical emission in the vicinity of sample surface in the microwave discharge was collected by an optical fiber and guided into the slit (10 µm) of a 0.5-m monochrometer (Acton Research Corporation Model Spectropro-500).
Spectral scans from 200 to 800 nm were recorded as synthesis conditions varied. The OES is compatibly linked to a computer, programmed to obtain qualitative information on the radicals present and their dependence on the experimental conditions.
3-2-2 Thermal Desorption Analyze (TDA)
The TDA apparatus was employed to analyze the released gas from the sample during the thermal heating. Thermal stability was tested by TDA gas analysis system (MTM Engineering, WT268) with a quadrupole mass spectrometer which characterized the released gas of fluorinated carbon bonds from 25℃ to 1050 , and the maxima ℃ measurement range of quadrupole mass were 200 amu..
3-2-3 Atomic Force Microscope (AFM)
AFM uses the interaction force between the probe and surface structure feature to measure the surface topography. The AFM tip diameter of Si3N4 cantilever (Microprobes, from Digital Instruments) was measured in a scanning electron microscope around 30-40 nm. To minimize any tip-induced damages, a contact force as small as possible, a set point of -20 (ca. 25-50 nN), was employed. The scan rate was 1.5 Hz. Calibration for the in-plane length measurements was carried out with a diffraction grating whereas the height was calibrated using a series of VLSI standards. The surface topography and roughness of a-C:F films were examined by atomic force microscope (Digital instrument NS3a controller with D3100 stage).
3-2-4 Nano-Indentor
The nano-indentor (Hysitron, Hysitron 35) was used to measure hardness of the fluorinated amorphous carbon films. The Berkovich diamond tip was used to test a-C:F films’ hardness. In order to avoid the substrate effect, the thickness of a-C:F films were deposited as thick as 1.5 µm.
3-2-5 Field-Emission Scanning Electron Microscope (FESEM)
The thickness of the a-C:F films were measured by field-emission scanning electron microscope (FESEM, Hitachi S-5000, Japan) with a resolution 2nm. Comparing FESEM with α-step and n&k , the FESEM thickness data of a-C:F films are more accurate.
3-2-6 Glow Discharge Spectrometer (GDS)
The GDS apparatus has ppm level resolution. GDS (GDS750A, ECO,
U.S.A.) was used to characterize whether the hydrogen element exists in a-C:F films or not.
3-2-7 Fourier-Transform Infrared Spectrometer (FTIR)
FTIR is the most widely used analytic method for the molecular structure characterization of organic and inorganic compounds. The types of fluorinated carbon bonds were measured by FTIR. All samples were qualitatively analyzed by FTIR (BOMEN Model DA8.3 SNV), and the scan ranged from 500 to 4000 cm-1 with a 2cm-1 resolution. The infrared light transmitted through the sample at normal incidence and then through a KBr grating into the MCT detector. The absorption spectrums of a blanket Si is used as the background signals.
3-2-8 X-ray Photoelectron Spectroscope (XPS)
Of all the contemporary surface characterization methods, XPS is most widely used. XPS is also called electron spectroscopy for chemical analysis (ESCA). Surface analysis by XPS is accomplished by irradiating a sample with monoenergetic soft X-ray and analyzing the energy of the detected electrons. The XPS measurements were carried on Perkin Elmer model PHI 1600 by using a single Mg Kα X-ray operating at 250 W. The X-ray source is at an angle of 54.7o with respect to the analyzer. Peak energy positions were corrected by using Pt peak. Based on the result from the high-resolution spherical capacitor analyzer (SCA), the energy resolution is 1.0 eV as survey scan spectrum and 0.1 eV as core-level spectrum, respectively. We used XPS chemical shift to make the C-C, CF, CF2, and CF3 bonds certain quantities.
3-2-9 High-Resolution Transmission Electron Microscope (HRTEM) HRTEM is the most powerful equipment for material microstructure analysis. The nanostructures were investigated by high-resolution transmission electron microscopy (HRTEM, JEOL, JEM-2010F and ).
3-2-10 High-Resolution Electron Energy Loss Spectroscope (HREELS) The electronic structures of fluorinated amorphous carbon film were investigated by high-resolution energy loss spectroscope. HREELS (Gatan, GIF 2000, U.S.A.) was used to characterize sp2% in the a-C:F films. The energy resolution is 0.1 eV to characterize 1s Æ π* transition in a-C:F films.
3-2-11 Electron Paramagnetic resonance (EPR)
The dangling bonds of a-C:F films were measured by EPR. We used EPR (Bruker, EMX-10, Germany) to observe the dangling bond density from 4K to 423K. The central magnetic field is ~3400 Gauss, and the microwave is ~9.5 GHz.
3-2-12 Capacitance-Voltage (C-V) Curve
The dielectric constants of all the films were estimated according to the capacitance-voltage (C-V). The capacitance (C-V) of a-C:F films was measured at 1 MHz by HP4280 apparatus. The mask with a diameter of 250 µm was covered on a-C:F films. For the C-V measuring, the top and bottom electrodes of Pt layer were coated with the mask by the MIM structure (Pt/a-C:F/Pt).
3-2-13 Current-Voltage (I-V) Curve
The current-voltage characteristic of a-C:F films was observed by HP4156 at a voltage from 0 to 100V. The sample structure is MIM structure, too.
3-2-14 n&k Analyzer
The refractive index of a-C:F films were measured by n&k analyzer (n&k Technology, n&k analyzer 1200, U.S.A.), with the wavelength ranging from 190 to 1000 nm.
3-2-15 UV-Visible Spectrophotometer (UV/VI)
The optical transparence of a-C:F films was examined by HP8453 UV/VI (U.S.A.) spectrophotometer, with the wavelength ranging from 190 to 1100 nm.
3-2-16 Photoluminescence (PL)
The fluorescence was observed by a fluorescence photoluminescence (PL) apparatus with helium-cadmium (He-Cd) laser (λ= 325 nm) as an excitation source.
3-2-17 Pulse Laser
Excimer pulse laser (Lamda Physik, Mode LPX 150P,λ=193 nm) was applied to measure photoluminescence lifetime of a-C:F films. The record time unit is 10-8 second.