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Fabrication of HfO2 patterns by laser interference nanolithography and selective dry etching for III-V CMOS application.

Benedicto M, Galiana B, Molina-Aldareguia JM, Monaghan S, Hurley PK, Cherkaoui K, Vazquez L, Tejedor P - Nanoscale Res Lett (2011)

Bottom Line: Pattern transfer to the HfO2 film was carried out by reactive ion beam etching using CF4 and O2 plasmas.A combination of atomic force microscopy, high-resolution scanning electron microscopy, high-resolution transmission electron microscopy, and energy-dispersive X-ray spectroscopy microanalysis was used to characterise the various etching steps of the process and the resulting HfO2/GaAs pattern morphology, structure, and chemical composition.We show that the patterning process can be applied to fabricate uniform arrays of HfO2 mesa stripes with tapered sidewalls and linewidths of 100 nm.

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Affiliation: Instituto de Ciencia de Materiales de Madrid, CSIC, C/Sor Juana Inés de la Cruz 3, 28049 Madrid, Spain. ptejedor@icmm.csic.es.

ABSTRACT
Nanostructuring of ultrathin HfO2 films deposited on GaAs (001) substrates by high-resolution Lloyd's mirror laser interference nanolithography is described. Pattern transfer to the HfO2 film was carried out by reactive ion beam etching using CF4 and O2 plasmas. A combination of atomic force microscopy, high-resolution scanning electron microscopy, high-resolution transmission electron microscopy, and energy-dispersive X-ray spectroscopy microanalysis was used to characterise the various etching steps of the process and the resulting HfO2/GaAs pattern morphology, structure, and chemical composition. We show that the patterning process can be applied to fabricate uniform arrays of HfO2 mesa stripes with tapered sidewalls and linewidths of 100 nm. The exposed GaAs trenches were found to be residue-free and atomically smooth with a root-mean-square line roughness of 0.18 nm after plasma etching.PACS: Dielectric oxides 77.84.Bw, Nanoscale pattern formation 81.16.Rf, Plasma etching 52.77.Bn, Fabrication of III-V semiconductors 81.05.Ea.

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TEM-EDS analysis of the HfO2/GaAs pattern. (a) Cross-section TEM image of a 100nm-wide HfO2 mesa stripe and a GaAs trench after nanostructuring. (b) Corresponding EDS elemental maps for O (K), Hf (M), Ga (L), and As (L). The amorphous layer located at the trench bottom surface is constructed of gallium oxide. Hf is concentrated in the mesa stripe and side feet.
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Figure 6: TEM-EDS analysis of the HfO2/GaAs pattern. (a) Cross-section TEM image of a 100nm-wide HfO2 mesa stripe and a GaAs trench after nanostructuring. (b) Corresponding EDS elemental maps for O (K), Hf (M), Ga (L), and As (L). The amorphous layer located at the trench bottom surface is constructed of gallium oxide. Hf is concentrated in the mesa stripe and side feet.

Mentions: The structure of the nanopatterned HfO2/GaAs samples was investigated by HR-TEM. Figure 5a, b, c depicts a series of cross-section HR-TEM images showing the periodic HfO2 nanopattern fabricated on the GaAs epilayer as well as details of an etched trench and a typical HfO2 mesa stripe. The anisotropic nature of the etch profile and the existence of slight variations in sidewall inclination are observable in these images. The HfO2 sidewall angle measured from Figure 5b, i.e. 47°, contrasts with that measured after CF4 etching, i.e. 70°. The HCl/H2O wet etch step thus appears to alter both the HfO2 linewidth and the mesa profile. In addition, Figure 5c clearly shows the formation of a approximately 10-nm-long foot at either side of the HfO2 stripe, due to the progressive erosion of the ARC and SiO2 layers during CF4 etching mentioned above. Note that the total HfO2 width, including the feet at both sides of the mesa, corresponds roughly to the resist linewidth in the original pattern, as indicated in the figure. The HfO2/GaAs interface appears quite abrupt and the underlying GaAs substrate shows no evidence of lattice damage. Nevertheless, an approximately 5-nm-thick amorphous layer is observed in the exposed GaAs regions (Figure 5b), which is likely to have formed as a result of ion damage or oxidation during exposure to the CF4 and O2 plasmas. Further investigation of the chemical composition of the HfO2/GaAs samples was performed by TEM/EDS analysis. The cross-sectional elemental maps corresponding to O (K), Hf (M), Ga (L), and As (K), gathered in Figure 6, indicate that the sub-surface layer is mainly constructed of gallium oxide, the less volatile of the oxidation products of GaAs, which is formed during the final exposure to the O2 plasma. This oxide layer can be removed prior to epitaxy by standard thermal desorption at 600°C. Finally, the composition map corresponding to Hf (M) shows that Hf is concentrated in the mesa stripes, although traces of this element were also detected in the mesa foot.


Fabrication of HfO2 patterns by laser interference nanolithography and selective dry etching for III-V CMOS application.

Benedicto M, Galiana B, Molina-Aldareguia JM, Monaghan S, Hurley PK, Cherkaoui K, Vazquez L, Tejedor P - Nanoscale Res Lett (2011)

TEM-EDS analysis of the HfO2/GaAs pattern. (a) Cross-section TEM image of a 100nm-wide HfO2 mesa stripe and a GaAs trench after nanostructuring. (b) Corresponding EDS elemental maps for O (K), Hf (M), Ga (L), and As (L). The amorphous layer located at the trench bottom surface is constructed of gallium oxide. Hf is concentrated in the mesa stripe and side feet.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3211495&req=5

Figure 6: TEM-EDS analysis of the HfO2/GaAs pattern. (a) Cross-section TEM image of a 100nm-wide HfO2 mesa stripe and a GaAs trench after nanostructuring. (b) Corresponding EDS elemental maps for O (K), Hf (M), Ga (L), and As (L). The amorphous layer located at the trench bottom surface is constructed of gallium oxide. Hf is concentrated in the mesa stripe and side feet.
Mentions: The structure of the nanopatterned HfO2/GaAs samples was investigated by HR-TEM. Figure 5a, b, c depicts a series of cross-section HR-TEM images showing the periodic HfO2 nanopattern fabricated on the GaAs epilayer as well as details of an etched trench and a typical HfO2 mesa stripe. The anisotropic nature of the etch profile and the existence of slight variations in sidewall inclination are observable in these images. The HfO2 sidewall angle measured from Figure 5b, i.e. 47°, contrasts with that measured after CF4 etching, i.e. 70°. The HCl/H2O wet etch step thus appears to alter both the HfO2 linewidth and the mesa profile. In addition, Figure 5c clearly shows the formation of a approximately 10-nm-long foot at either side of the HfO2 stripe, due to the progressive erosion of the ARC and SiO2 layers during CF4 etching mentioned above. Note that the total HfO2 width, including the feet at both sides of the mesa, corresponds roughly to the resist linewidth in the original pattern, as indicated in the figure. The HfO2/GaAs interface appears quite abrupt and the underlying GaAs substrate shows no evidence of lattice damage. Nevertheless, an approximately 5-nm-thick amorphous layer is observed in the exposed GaAs regions (Figure 5b), which is likely to have formed as a result of ion damage or oxidation during exposure to the CF4 and O2 plasmas. Further investigation of the chemical composition of the HfO2/GaAs samples was performed by TEM/EDS analysis. The cross-sectional elemental maps corresponding to O (K), Hf (M), Ga (L), and As (K), gathered in Figure 6, indicate that the sub-surface layer is mainly constructed of gallium oxide, the less volatile of the oxidation products of GaAs, which is formed during the final exposure to the O2 plasma. This oxide layer can be removed prior to epitaxy by standard thermal desorption at 600°C. Finally, the composition map corresponding to Hf (M) shows that Hf is concentrated in the mesa stripes, although traces of this element were also detected in the mesa foot.

Bottom Line: Pattern transfer to the HfO2 film was carried out by reactive ion beam etching using CF4 and O2 plasmas.A combination of atomic force microscopy, high-resolution scanning electron microscopy, high-resolution transmission electron microscopy, and energy-dispersive X-ray spectroscopy microanalysis was used to characterise the various etching steps of the process and the resulting HfO2/GaAs pattern morphology, structure, and chemical composition.We show that the patterning process can be applied to fabricate uniform arrays of HfO2 mesa stripes with tapered sidewalls and linewidths of 100 nm.

View Article: PubMed Central - HTML - PubMed

Affiliation: Instituto de Ciencia de Materiales de Madrid, CSIC, C/Sor Juana Inés de la Cruz 3, 28049 Madrid, Spain. ptejedor@icmm.csic.es.

ABSTRACT
Nanostructuring of ultrathin HfO2 films deposited on GaAs (001) substrates by high-resolution Lloyd's mirror laser interference nanolithography is described. Pattern transfer to the HfO2 film was carried out by reactive ion beam etching using CF4 and O2 plasmas. A combination of atomic force microscopy, high-resolution scanning electron microscopy, high-resolution transmission electron microscopy, and energy-dispersive X-ray spectroscopy microanalysis was used to characterise the various etching steps of the process and the resulting HfO2/GaAs pattern morphology, structure, and chemical composition. We show that the patterning process can be applied to fabricate uniform arrays of HfO2 mesa stripes with tapered sidewalls and linewidths of 100 nm. The exposed GaAs trenches were found to be residue-free and atomically smooth with a root-mean-square line roughness of 0.18 nm after plasma etching.PACS: Dielectric oxides 77.84.Bw, Nanoscale pattern formation 81.16.Rf, Plasma etching 52.77.Bn, Fabrication of III-V semiconductors 81.05.Ea.

No MeSH data available.


Related in: MedlinePlus