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Plasma-assisted atomic layer deposition of nanolaminates for gate dielectric applications
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Image of FIG. 1.
FIG. 1.

(Color online) Index of refraction (left axis) and optical bandgap, E (right axis) vs the relative Ti thickness in the nine films presented in this study. Relative Ti thickness is defined as , where is estimated from the expected deposition rate of TiO alone. The values of amorphous AlO and TiO are in close agreement with those reported in the literature. From this figure, it is evident that by adjusting the amount of Ti (Al) in the NLs, one can modulate the index of refraction and bandgap of the material.

Image of FIG. 2.
FIG. 2.

(Color online) XPS of NLs [AlO + 4TiO] (I), [AlO + TiO] (II), and [4AlO + TiO] (III) after 10 s sputtering through the oxide layer. (a) Al 2 XPS results showing a nearly symmetric peak centered at ∼74.9 eV for all NLs. This peak can be fit with two lines at positions ∼75.1 and 74.6 eV, corresponding to fully oxidized AlO and Al-O-Ti bonding, respectively; (b) Ti 2  XPS results. This spectrum consists of three peaks at ∼457.8, ∼458.5, and ∼459.6 eV corresponding to TiO, Ti-O-Al, and fully oxidized TiO, respectively; (c) The O 1  peak is centered at ∼531.5 eV and can be fit with four distinct components. Two predominant peaks at ∼531.0 and ∼531.5 eV are associated with TiO and AlO, respectively, and two less intense peaks at ∼532.4 and ∼533.6 eV correspond to hydroxyl groups and HO.

Image of FIG. 3.
FIG. 3.

(Color online) (a) Results of the CV measurements at 1 MHz for forward and reverse voltage sweeps from −5 V to + 10 V at 0.1 V resolution on 100 m diameter capacitors. The arrows indicate the voltage sweep direction. The TiO film shows the largest value of accumulation capacitance ( ), while the pure AlO has the smallest. The rest of the NLs show capacitance values in between those of AlO and TiO; (b) Measured dielectric constants shown in the bottom data set “Experimental” correspond to that of the NLs and SiO capacitors in series. Subtracting the contribution from the 2.0 nm SiO layer yields an increase in the dielectric as shown in the top data set of (b); (c) Current–voltage (I–V) characteristics under positive and negative biases for the AlO, TiO, and NLs, on 100 m diameter capacitors. The TiO film exhibits the largest amount of leakage current ∼10 A/cm at 1 V in forward bias, whereas the pure AlO exhibits the lowest, ∼10 A/cm at 1 V. The NLs follow a trend of decreasing leakage current with increasing Al incorporation as indicated by the arrow.

Image of FIG. 4.
FIG. 4.

(Color online) Z-contrast micrographs from the cross-section Si/TiO/AlO nanolaminated layers: (a) low-resolution micrograph showing the total NL thickness. Note the darker band at the interface with Si; (b) High-resolution micrograph showing the Si dumbbells with the amorphous layers on top of the substrate. The darker contrast suggests the presence of lower atomic number (Z) elements; (c) the higher magnification from the outline area in (b) showing the presence of the amorphous phase.

Image of FIG. 5.
FIG. 5.

(Color online) (a) Cross-section micrograph using GIFF detector with indicated positions of the electron beam for the EELS studies; (b) EELS spectra showing the presence of O and Ti in position #1, (c) The same elements from position #2, and (d) from position #3. On the areas of the NL (like #3 and #4) the intensity of the Ti line is changing by about +/−10% counts from place to place; (e) higher energy spectra showing Si and Al presence in the black area #2; (f) The Al presence in area #3, #4. Similarly, as for Ti L, the intensity of the Al K is alternating by about 10–15% from one area to another.


Generic image for table

Parameters of the TiO, AlO, and NLs included in this study. Thickness and index of refraction were determined by spectroscopic ellipsometry using a Cauchy model to fit the data. The optical bandgap was experimentally determined by a reflectance measurement. The dielectric constant was calculated from C-V plots using the capacitance of the oxides measured in the accumulation region. Errors in the measurements are within 5%.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Plasma-assisted atomic layer deposition of nanolaminates for gate dielectric applications