Research Update: Atmospheric pressure spatial atomic layer deposition of ZnO thin films: Reactors, doping, and devices

Hoye, Robert L. Z.; Muñoz‐Rojas, David; Nelson, Shelby F.; Illiberi, A.; Poodt, Paul; Roozeboom, F.; MacManus‐Driscoll, Judith L.

doi:10.1063/1.4916525

Cited by 76 publications

(96 citation statements)

References 64 publications

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“…This atmospheric pressure chemical vapor deposition (AP-CVD) generally results in accelerated film deposition rates, while still producing conformal, pinhole-free films [2]. Growing interest in spatial ALD has led to several review papers in recent years [3][4][5][6], and companies such as Levitech, Beneq, and SoLayTec have commercialized spatial ALD systems. Both metal oxides and metals have been deposited [4,5,7], and AP-SALD and AP-CVD films have been utilized in thin film transistors [8,9], metal-insulator-metal diodes [10], photovoltaic devices [2,[11][12][13][14][15][16][17], and LEDs [18][19][20].…”

Section: Introductionmentioning

confidence: 99%

In-situ observation of nucleation and property evolution in films grown with an atmospheric pressure spatial atomic layer deposition system

et al. 2020

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Atmospheric pressure-spatial atomic layer deposition (AP-SALD) is a promising open-air deposition technique for high-throughput manufacturing of nanoscale films, yet the nucleation and property evolution in these films has not been studied in detail. In this work, in situ reflectance spectroscopy was implemented in an AP-SALD system to measure the properties of Zinc oxide (ZnO) and Aluminum oxide (Al 2 O 3 ) films during their deposition. For the first time, this revealed a substrate nucleation period for this technique, where the length of the nucleation time was sensitive to the deposition parameters. The in situ characterization of thickness showed that varying the deposition parameters can achieve a wide range of growth rates (0.1-3 nm/cycle), and the evolution of optical properties throughout film growth was observed. For ZnO, the initial bandgap increased when deposited at lower temperatures and subsequently decreased as the film thickness increased. Similarly, for Al 2 O 3 the refractive index was lower for films deposited at a lower temperature and subsequently increased as the film thickness increased. Notably, where other implementations of reflectance spectroscopy require previous knowledge of the film's optical properties to fit the spectra to optical dispersion models, the approach developed here utilizes a large range of initial guesses that are inputted into a Levenberg-Marquardt fitting algorithm in parallel to accurately determine both the film thickness and complex refractive index.

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Section: Introductionmentioning

confidence: 99%

In-situ observation of nucleation and property evolution in films grown with an atmospheric pressure spatial atomic layer deposition system

et al. 2020

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“…A detailed description of AP-SALD reactor design and operation can be found elsewhere. 11,12 This approach allows the deposition to occur one to two orders of magnitude faster than conventional ALD and outside vacuum, which is compatible with roll-to-roll processing. High quality conformal oxide films produced by AP-SALD can be deposited at low temperatures (<150 °C) on a variety of substrates including plastics, which enables AP-SALD films to be applied to low-cost functional devices such as solar cells 13 , light emitting diodes 14 and thin-film transistors 15 .…”

Section: Introductionmentioning

confidence: 82%

“…13 In this work, a custom-made AP-SALD reactor was used, adapted from the original design developed by Kodak. 11,12 Details of the reactor customization are given in Ref. 12.…”

Section: Depositing Zn 1-x Mg X O Using Ap-sald Reactormentioning

confidence: 99%

“…12 Herein, we still refer to the reactor as an AP-SALD reactor because it has the same fundamental design principles as other AP-SALD reactors. 11 We used our reactor to deposit the n-type layer for our solar cells, in particular zinc oxide and zinc magnesium oxide (Zn 1-x Mg x O 16,17 ). Incorporating Mg into ZnO allows the conduction band to be tuned, which is important for reducing losses due to band-tail thermalization 13 and interfacial recombination.…”

Section: Introductionmentioning

confidence: 99%

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Improved Heterojunction Quality in Cu2O-based Solar Cells Through the Optimization of Atmospheric Pressure Spatial Atomic Layer Deposited Zn1-xMgxO

Ievskaya

Hoye

Sadhanala

et al. 2016

JoVE

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Atmospheric pressure spatial atomic layer deposition (AP-SALD) was used to deposit n-type ZnO and Zn 1-x Mg x O thin films onto p-type thermally oxidized Cu 2 O substrates outside vacuum at low temperature. The performance of photovoltaic devices featuring atmospherically fabricated ZnO/Cu 2 O heterojunction was dependent on the conditions of AP-SALD film deposition, namely, the substrate temperature and deposition time, as well as on the Cu 2 O substrate exposure to oxidizing agents prior to and during the ZnO deposition. Superficial Cu 2 O to CuO oxidation was identified as a limiting factor to heterojunction quality due to recombination at the ZnO/Cu 2 O interface. Optimization of AP-SALD conditions as well as keeping Cu 2 O away from air and moisture in order to minimize Cu 2 O surface oxidation led to improved device performance. A three-fold increase in the open-circuit voltage (up to 0.65 V) and a two-fold increase in the short-circuit current density produced solar cells with a record 2.2% power conversion efficiency (PCE). This PCE is the highest reported for a Zn 1-x Mg x O/Cu 2 O heterojunction formed outside vacuum, which highlights atmospheric pressure spatial ALD as a promising technique for inexpensive and scalable fabrication of Cu 2 O-based photovoltaics.

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“…Firstly proposed by Suntola et al, 15 sALD is receiving increasing attention within the industry because of its high throughput in terms of fast rate deposition of high-quality material for large-area applications. [16][17][18][19][20][21][22] Therefore, spatial atmospheric-pressure plasma-enhanced ALD uniquely combines the advantages of a fast ALD concept with the possibility of growing insulating and conducting materials at atmospheric conditions and at relatively low temperatures compatible with flexible and temperature sensitive substrates yet without the undesired size restrictions imposed by vacuum systems. Although the use of plasma on substrates with pronounced topographies remains challenging, the advantage of using atmospheric plasma resides in the low kinetic energy of the ionic species, which translates into low ion bombardment and, consequently, reduced ion damage.…”

mentioning

confidence: 99%

Atmospheric Pressure Plasma Enhanced Spatial ALD of ZrO₂for Low-Temperature, Large-Area Applications

Mione

Katsouras

Creyghton

et al. 2017

ECS J. Solid State Sci. Technol.

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High permittivity (high-k) materials have received considerable attention as alternatives to SiO 2 for CMOS and low-power flexible electronics applications. In this study, we have grown high-quality ZrO 2 by using atmospheric-pressure plasma-enhanced spatial ALD (PE-sALD), which, compared to temporal ALD, offers higher effective deposition rates and uses atmospheric-pressure plasma to activate surface reactions at lower temperatures. We used tetrakis(ethylmethylamino)zirconium (TEMAZ) as precursor and O 2 plasma as co-reactant at temperatures between 150 and 250 • C. Deposition rates as high as 0.17 nm/cycle were achieved with N-and C-contents as low as 0.4% and 1.5%, respectively. Growth rate, film crystallinity and impurity contents in the films were found to improve with increasing deposition temperature. The measured relative permittivity lying between 18 and 28 with leakage currents in the order of 5 × 10 −8 A/cm 2 demonstrates that atmospheric PE-sALD is a powerful technique to deposit ultrathin, high-quality dielectrics for low-temperature, large-scale microelectronic applications. The continuous improvement in performance of integrated circuits has been based on miniaturization of components. The effective gate length in field-effect transistors shrinks to smaller and smaller sizes and, consequently, the thickness of the gate oxide decreases.1 SiO 2 has been the most popular gate oxide material used in microelectronic manufacturing due to its thermal stability and ideal interface quality on Si. However, during the past fifty years the thickness of the SiO 2 gate oxide has already been reduced to its physical limit of 1.2 nm, below which a critical gate leakage of 1 A/cm 2 is exceeded. 2 To overcome this problem, dielectrics with a high permittivity (high-k materials) have been extensively investigated as promising substitutes of the conventional SiO 2 for CMOS and DRAM technology. The high permittivity (k > 10) ensures high capacitance for thicker gate oxide layers while greatly reducing tunneling and gate leakage currents. 3,4 Among high-k oxides, ZrO 2 is considered one of the most promising SiO 2 alternatives due to its high dielectric constant (k = 20-25), large bandgap (5.1-7.8 eV) and thermodynamical stability. 5,6 ZrO 2 proved to be a good dielectric in transistor applications with leakage current of the order of 10 −6 -10 −9 A/cm 2 and in DRAM capacitor applications especially when present in ZrO 2 /Al 2 O 3 /ZrO 2 nanolaminate structures.7 High-k materials are also relevant for low-power applications of flexible electronics. 5,8-11High-k materials are deposited in a variety of chemical and physical deposition techniques including metallorganic chemical vapor deposition (MOCVD), atomic layer deposition (ALD), sol-gel and sputtering. ALD has proven to be the most suitable technique for high-k deposition due to its unique nanoscale thickness and layer uniformity control. In its conventional time-sequenced mode, ALD is a gas phase deposition technique in which the substrate surface is exposed altern...

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Research Update: Atmospheric pressure spatial atomic layer deposition of ZnO thin films: Reactors, doping, and devices

Cited by 76 publications

References 64 publications

In-situ observation of nucleation and property evolution in films grown with an atmospheric pressure spatial atomic layer deposition system

In-situ observation of nucleation and property evolution in films grown with an atmospheric pressure spatial atomic layer deposition system

Improved Heterojunction Quality in Cu<sub>2</sub>O-based Solar Cells Through the Optimization of Atmospheric Pressure Spatial Atomic Layer Deposited <br />Zn<sub>1-x</sub>Mg<sub>x</sub>O

Atmospheric Pressure Plasma Enhanced Spatial ALD of ZrO₂for Low-Temperature, Large-Area Applications

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Research Update: Atmospheric pressure spatial atomic layer deposition of ZnO thin films: Reactors, doping, and devices

Cited by 76 publications

References 64 publications

In-situ observation of nucleation and property evolution in films grown with an atmospheric pressure spatial atomic layer deposition system

In-situ observation of nucleation and property evolution in films grown with an atmospheric pressure spatial atomic layer deposition system

Improved Heterojunction Quality in Cu<sub>2</sub>O-based Solar Cells Through the Optimization of Atmospheric Pressure Spatial Atomic Layer Deposited <br />Zn<sub>1-x</sub>Mg<sub>x</sub>O

Atmospheric Pressure Plasma Enhanced Spatial ALD of ZrO2for Low-Temperature, Large-Area Applications

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Atmospheric Pressure Plasma Enhanced Spatial ALD of ZrO₂for Low-Temperature, Large-Area Applications