Wet-chemical etching of (11 $$\bar 2$$ 0) ZnO films0) ZnO films

SiCl 4 -based reactive ion etching (RIE) is used to etch Mg x Zn 1ÿ x O (0 x 0.3) films grown on r-plane sapphire substrates. The RIE etch rates are investigated as a function of Mg composition, RIE power, and chamber pressure. SiO 2 is used as the etching mask to achieve a good etching profile. In comparison with wet chemical etching, the in-plane etching anisotropy of Mg x Zn 1ÿ x O (0 x 0.3) films is reduced in RIE. X-ray photoelectron spectroscopy measurements show that there is no Si and Cl contamination detected at the etched surface under the current RIE conditions. The influence of the RIE to the optical properties has been investigated.

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“…100 direction is observed for wet chemical etching. 13 This in-plan etching anisotropy is found to be reduced in the SiCl 4 -based RIE.…”

Section: Etching Ratementioning

confidence: 94%

SiCl4-based reactive ion etching of ZnO and MgxZn1−xO films on r-sapphire substrates

Zhu

Saraf

Zhong

et al. 2006

Journal of Elec Materi

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“…The channel mesa was formed by the wet chemical etching by using HCl:H 2 O solution. 13 A SiO 2 layer ($120 nm) deposited by plasma enhanced chemical vapor deposition (PECVD) was used as the gate dielectric. The source and drain windows were opened on SiO 2 using buffered oxide etch (BOE).…”

Section: Methodsmentioning

confidence: 99%

ZnO TFT Devices Built on Glass Substrates

Zhu

Chen

Saraf

et al. 2008

Journal of Elec Materi

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ZnO thin-film transistors (TFTs) were built on glass substrates. The device with a top gate configuration operates in the depletion mode. The ZnO channel was grown by metalorganic chemical vapor deposition (MOCVD) on glass at low temperature. SiO 2 was used as the gate dielectric. The TFT has an on/off ratio of $4.0 · 10 4 and a channel field-effect mobility of $4.0 cm 2 /V s. The average transmittance of the ZnO film in the visible wavelength is $80%. To compare the characteristics of the TFTs prepared by using a poly-ZnO and epitaxial-ZnO channel, an epi-ZnO TFT with the same configuration and dimensions was made on an r-Al 2 O 3 substrate. The epi-ZnO TFT shows higher field-effect mobility of $35 cm 2 /V s and on/off ratio of $10 8 .

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“…For example, nanosized structures on silicon crystals such as pyramidal tips having only one atom at the apex can be fabricated using chemical etching. 13,14 In spite of many reports available on etching of the polycrystalline ZnO thin films using various etchants, such as HCl, H 2 SO 4 , H 3 PO 4 , HCl/H 3 PO 4 /H 2 O, HNO 3 , and a buffered oxide etch solution, [15][16][17][18][19][20] only few reports exist on wet chemical etching studies of bulk ZnO single crystal. 10,[21][22][23] However, the etching behavior of the polycrystalline films is considerably different from that of the ZnO single crystals.…”

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confidence: 99%

Controlled Etching Behavior of O-Polar and Zn-Polar ZnO Single Crystals

Mehta

Meier

2011

J. Electrochem. Soc.

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We report on optimized wet chemical processes for both the O-polar and Zn-polar faces of wurtzite bulk ZnO single crystals. Different solutions were tested to achieve controllable etching. For the O-polar ZnO surface, a controlled etch rate of 3.8 m/min was observed using an acid mixture of H 3 PO 4 /CH 3 COOH/H 2 O as an etchant. Fine-patterning of the O-polar surface with moderate etch rates and high reproducibility can be obtained using an aqueous 5% NH 4 Cl solution. In comparison, the Zn-polar ZnO surface etches significantly slower in HCl solution and exhibits strong pH dependence. Nevertheless, pH control enables reproducible etching even of the Zn-polar surface.Zinc oxide ͑ZnO͒, one of the most widely investigated wurtzite semiconductors, has attracted significant attention in the past, 1-4 not only as a single crystal but also in the form of polycrystalline thin films. Its remarkable properties, such as its wide direct bandgap ͑3.37 eV͒, large bonding strength ͑cohesive energy of 1.89 eV and melting point of 2248 K͒, and high excitonic binding energy ͑60 meV͒ leading to efficient excitonic optical transitions even at elevated temperatures, make it attractive for electronic and optoelectronic applications such as piezoelectric transducers, transparent thin film electronics, light emitting, and light detecting devices operated in the blue and the ultraviolet spectral range. 5-8 Additionally, ZnO has also found promising applications for nanostructured gas and in chemical and biological sensors. 9 The fabrication of such devices demands the development of etching processes with a controlled degree of anisotropy, with either high or moderate etch rates, and controlled surface morphology for mass production and device reliability. However, wurtzite-type ZnO single crystals exhibit two polar surfaces that are terminated by Znions on the ͑0001͒ plane and O-ions on the ͑0001͒ plane with different chemical and physical properties. 10,11 Therefore, a clear understanding of the chemical reactions during the etch process on each polar face is essential for device patterning. In principle, two methods for planar device patterning have been reported: one method is dry etching such as reactive ion etching using radio frequency or an inductively coupled plasma to remove material from the surface. 12 This method has the benefit of exhibiting the same reaction rates regardless of the crystal orientation. However, it requires expensive investments in equipment. Another method is to use wet chemical etching ͑WCE͒ using liquids, such as the aqueous solutions of acids or mixed acids as etching agents. Compared with dry etch processes, wet etch techniques possess the advantages of simplicity and low equipment cost. Moreover, during dry etching, a hard mask layer such as a metal, SiO 2 , or Si 3 N 4 must often be used as an etch mask because photoresist ͑PR͒ is decomposed under the influence of the plasma, producing carbon residues. This hard mask layer, however, is difficult to remove without attacking the ZnO, depending on it...

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Wet-chemical etching of (11 $$\bar 2$$ 0) ZnO films0) ZnO films

Cited by 34 publications

References 12 publications

SiCl4-based reactive ion etching of ZnO and MgxZn1−xO films on r-sapphire substrates

SiCl4-based reactive ion etching of ZnO and MgxZn1−xO films on r-sapphire substrates

ZnO TFT Devices Built on Glass Substrates

Controlled Etching Behavior of O-Polar and Zn-Polar ZnO Single Crystals

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