Stability of thin film transistors incorporating a zinc oxide or indium zinc oxide channel deposited by a high rate sputtering process

Flewitt, Andrew J.; Dutson, J. D.; Beecher, Paul; Paul, Douglas J.; Wakeham, Steve; Vickers, M. E.; Ducati, Caterina; Speakman, S.P.; Milne, W. I.; Thwaites, M.J.

doi:10.1088/0268-1242/24/8/085002

Cited by 61 publications

(36 citation statements)

References 26 publications

(35 reference statements)

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“…This yields high rate, uniform erosion of the target surface. HiTUS has been used to deposit low temperature metal oxides for transparent conducting electrodes [19], light emitting devices [20], surface acoustic wave devices [21] and thin film transistors [22][23][24].…”

Section: Depositionmentioning

confidence: 99%

Intrinsic photoluminescence from low temperature deposited zinc oxide thin films as a function of laser and thermal annealing

Tsakonas¹,

Cranton²,

Li³

et al. 2013

J. Phys. D: Appl. Phys.

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Abstract. An investigation into the modification of low temperature deposited ZnO thin films by different annealing processes has been undertaken using laser, thermal and rapid thermal annealing of 60nm ZnO films deposited by Hi-Target-Utilization-Sputtering. Single pulse laser annealing using a KrF excimer laser ( A = 248nm) over a range of fluences up to 315 mJ/cm 2 demonstrates controlled indepth modification of internal film microstructure and luminescence properties without the film degradation produced by high temperature thermal and RTA processes. Photoluminescence properties show that the ratio of defect related deep level emission (DLE, 450nm -750nm, 2.76eV-1.65eV) to excitonic near band-edge emission (NBE at 381nm, 3.26eV) is directly correlated to processing parameters. Thermal and rapid thermal processing results in the evolution of a strong visible orange/red DLE photoluminescence (with peaks at 590nm, 2.10eV and 670nm, 1.85eV) dominated by defects related to excess oxygen. At higher temperatures, the appearance of a green/yellow emission (530nm, 2.34eV) indicates a transition of the dominant radiative transfer mechanism. In contrast, laser processing removes defect related DLE and produces films with intense NBE luminescence, correlated to the observed formation of large grains (25-40nm IntroductionThin films of ZnO are of interest across a range of optoelectronic and sensor device applications due to ZnO being a wide gap (>3 eV) n-type semiconductor with a high exciton binding energy [1] and a piezoelectric response [2]. Poly crystalline thin films of ZnO are deposited by a variety of physical and chemical vapour methods, with sputtering [1] being a preferred choice for low cost and scalability. However, to achieve the desired thin film properties, particularly for low temperature deposited films, it is critical to control grain microstructure, surface morphology, and internal defects [3]. Techniques that have been previously reported to improve these properties of ZnO thin films include post deposition thermal annealing [4,5], rapid thermal annealing [6,7], and laser annealing [8,9,10]. In this paper we present the results from a comparative study of the effect of all three of these annealing processes on the microstructure, crystallinity and associated intrinsic photoluminescence properties of low temperature sputter deposited ZnO thin films. The results demonstrate that pulsed laser annealing is a powerful tool for the controlled modification of low temperature deposited thin films. In particular, the work presented here explores the effect of a more comprehensive range of laser processing parameters on low temperature ZnO thin films than previously reported. The results

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Section: Depositionmentioning

confidence: 99%

Intrinsic photoluminescence from low temperature deposited zinc oxide thin films as a function of laser and thermal annealing

Tsakonas¹,

Cranton²,

Li³

et al. 2013

J. Phys. D: Appl. Phys.

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“…A schematic diagram of the HiTUS deposition system is illustrated in an earlier publication [39]. The HiTUS deposition system generates a remote, high-density rf argon plasma in the sidearm, which is then amplified and directed onto the target using two electromagnets.…”

Section: High Target Utilization Sputtering (Hitus)mentioning

confidence: 99%

High‐density remote plasma sputtering of high‐dielectric‐constant amorphous hafnium oxide films

Bayer

Hofmann

et al. 2013

Physica Status Solidi (b)

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Hafnium oxide (HfO x ) is a high dielectric constant (k) oxide which has been identified as being suitable for use as the gate dielectric in thin film transistors (TFTs). Amorphous materials are preferred for a gate dielectric, but it has been an ongoing challenge to produce amorphous HfO x while maintaining a high dielectric constant. A technique called high target utilization sputtering (HiTUS) is demonstrated to be capable of depositing high-k amorphous HfO x thin films at room temperature. The plasma is generated in a remote chamber, allowing higher rate deposition of films with minimal ion damage. Compared to a conventional sputtering system, the HiTUS technique allows finer control of the thin film microstructure. Using a conventional reactive rf magnetron sputtering technique, monoclinic nanocrystalline HfO x thin films have been deposited at a rate of $1.6 nm min À1 at room temperature, with a resistivity of 10 13 V cm, a breakdown strength of 3.5 MV cm À1 and a dielectric constant of $18.2. By comparison, using the HiTUS process, amorphous HfO x (x ¼ 2.1) thin films which appear to have a cubic-like short-range order have been deposited at a high deposition rate of $25 nm min À1 with a high resistivity of 10 14 V cm, a breakdown strength of 3 MV cm À1 and a high dielectric constant of $30. Two key conditions must be satisfied in the HiTUS system for high-k HfO x to be produced. Firstly, the correct oxygen flow rate is required for a given sputtering rate from the metallic target. Secondly, there must be an absence of energetic oxygen ion bombardment to maintain an amorphous microstructure and a high flux of medium energy species emitted from the metallic sputtering target to induce a cubiclike short range order. This HfO x is very attractive as a dielectric material for large-area electronic applications on flexible substrates.

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“…These five patterns were replicated in batches at seven locations on each wafer (Supplementary Figure S1 is a location map of these batches). Subsequently, the zinc tin oxide was deposited into the pattern using a remote plasma deposition High Target Utilization System (HiTUS) [19][20][21], i.e. the metal oxide is only found bridging each of the pre-patterned pair of contacts.…”

Section: Sample Descriptionmentioning

confidence: 99%

High-resistivity metal-oxide films through an interlayer of graphene grown directly on copper electrodes

Pfaendler

Flewitt

2018

Graphene Technol

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Functional oxides are important materials for multiple applications in flexible and transparent electronics. Electrically contacting these oxides to form active channels is often challenging as they suffer significant alteration or instabilities when interfaced with metal electrodes. Here, we demonstrate a new scheme to electrically contact thin films of semiconducting zinc tin oxide (ZnSnO) that employs pre-patterned copper electrodes encapsulated by chemical-vapour-deposited graphene. Measurement of over more than 100 channels with varying geometry and nature of contact shows that the bulk resistivity of the ZnSnO channels with graphene/Cu composite is at least two orders of magnitude larger than the same films deposited directly on aluminium (Al) contacts. Moreover, the ZnSnO channels with Cu/graphene contacts showed nearly ohmic transport, in contrast to space-charge-limited conduction observed for other contacting schemes. Our results outline a new application of graphene in a step towards the development of alternative contacting strategies for oxide electronics.

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Stability of thin film transistors incorporating a zinc oxide or indium zinc oxide channel deposited by a high rate sputtering process

Cited by 61 publications

References 26 publications

Intrinsic photoluminescence from low temperature deposited zinc oxide thin films as a function of laser and thermal annealing

Intrinsic photoluminescence from low temperature deposited zinc oxide thin films as a function of laser and thermal annealing

High‐density remote plasma sputtering of high‐dielectric‐constant amorphous hafnium oxide films

High-resistivity metal-oxide films through an interlayer of graphene grown directly on copper electrodes

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