Thin Al2O3 films of different thicknesses (10–40nm) were deposited by plasma-assisted atomic layer deposition on substrates of poly(2,6-ethylenenaphthalate) (PEN), and the water vapor transmission rate (WVTR) values were measured by means of the calcium test. The permeation barrier properties improved with decreasing substrate temperature and a good WVTR of 5×10−3gm−2day−1 (WVTRPEN=0.5gm−2day−1) was measured for a 20nm thick Al2O3 film deposited at room temperature using short purging times. Such ultrathin, low-temperature deposited, high-quality moisture permeation barriers are an essential requirement for the implementation of polymeric substrates in flexible electronic and display applications.

Within the method of atomic layer deposition (ALD), additional reactivity can be delivered to the surface in the form of plasmaproduced species. The application of such a low-temperature plasma in the ALD cycle can therefore open up a processing parameter space that is unattainable by the strictly thermally driven process. In this contribution several possible benefits of plasmaassisted ALD will be reviewed showing bright prospect for plasma-assisted ALD for a large variety of applications, also far beyond the typical use in semiconductor devices. Atomic layer deposition for processing at the nanoscaleWithin the current trends of downscaling in the semiconductor industry and the boost in nanoscience and nanotechnology, atomic layer deposition (ALD) is the method of choice for depositing high quality films with ultimate growth control and with excellent step coverage on very demanding topologies [1, 2 , 3 ]. The virtue of this approach is that deposition is controlled at the atomic level by self-limiting surface reactions by alternate exposure of the substrate surface to different gas-phase precursors (see Fig. 1). Each surface reaction occurs between a gas phase reactant (precursor) and a surface functional group creating a volatile product molecule that desorbs from the surface, and a new surface functional group that is not reactive with the precursor. After pumping away the first precursor, a second precursor is introduced, which deposits a second element through reaction with the new surface functional group and then restores the initial surface functional group. This set of reactions form one ALD-cycle resulting basically in one (sub)monolayer of film growth per cycle. The ALD-cycle can be repeated until the desired film thickness is reached. Furthermore, unlike chemical vapor deposition (CVD), the deposition rate is not proportional to the flux on the surface. Therefore, the same amount of material is deposited everywhere on the surface even in high aspect ratio structures when there is sufficient flux. Other benefits of ALD are the good uniformity that can be achieved on large substrates, the relatively low substrate temperatures used in the process (temperature window typically 200-400 °C), and the fact that ALD can readily produce multilayer structures.

For the determination of specific contact resistance in semiconductor devices, it is usually assumed that the sheet resistance under the contact is identical to that between the contacts. This generally does not hold for contacts to AlGaN/GaN structures, where an effective doping under the contact is thought to come from reactions between the contact metals and the AlGaN/GaN. As a consequence, conventional extraction of the specific contact resistance and transfer length leads to erroneous results. In this Letter, the sheet resistance under gold-free Ti/Al-based Ohmic contacts to AlGaN/GaN heterostructures on Si substrates has been investigated by means of electrical measurements, transmission electron microscopy, and technology computer-aided design simulations. It was found to be significantly lower than that outside of the contact area; temperature-dependent electrical characterization showed that it exhibits semiconductor-like behavior. The increase in conduction is attributed to n-type activity of nitrogen vacancies in the AlGaN. They are thought to form during rapid thermal annealing of the metal stack when Ti extracts nitrogen from the underlying semiconductor. The high n-type doping in the region between the metal and the 2-dimensional electron gas pulls the conduction band towards the Fermi level and enhances horizontal electron transport in the AlGaN. Using this improved understanding of the properties of the material underneath the contact, accurate values of transfer length and specific contact resistance have been extracted.

Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publicationCitation for published version (APA): Roozeboom, F., Klootwijk, J. H., Verhoeven, J. F. C., Heuvel, van den, F. C., Dekkers, W., Heil, S. B. S., ... Blin, D. (2007). ALD options for Si-integrated ultrahigh-density decoupling capacitors in pore and trench designs. ECS Transactions, 3(15), 173-181. DOI: 10.1149/1.2721486 General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. This paper reviews the options of using Atomic Layer Deposition (ALD) in passive and heterogeneous integration. The miniaturization intended by both integration schemes aim at Si-based integration for the former and at die stacking in a compact System-in-Package for the latter.In future Si-based integrated passives a next miniaturization step in trench capacitors requires the use of multiple 'classical' MOS layer stacks and the use of so-called high-k dielectrics (based on HfO 2 , etc.) and novel conductive layers like TiN, etc. to compose MIS and MIM stacks in 'trench' and 'pore' capacitors with capacitance densities exceeding 200 nF/mm 2 . One of the major challenges in realizing ultrahigh-density trench capacitors is to find an attractive pore lining and filling fabrication technology at reasonable cost and reaction rate as well as low temperature (for back-end processing freedom). As the deposition for the dielectric and conductive layers should be highly uniform, step-conformal and lowtemperature (≤ 400 °C), ALD is an enabling technology here, by virtue of the self-limiting mechanism of this layer-by-layer deposition technique.This article discusses first a f...