bluuebunny/crossref_metadata_2025_split huggingface dataset:
Selective Removal of Native SiO2 Using XeF2
Authors: Hinckley Adam , Mancheno-Posso Pablo , Lai C. Steven , Muscat Anthony J. 
Published: February 2020

Selective removal of native silicon dioxide (NOx) relative to the underlying Si substrate and to other films present in a device structure is important in forming low resistance electrical contacts. Xenon difluoride (XeF2) was chosen as the F-source because of the weak molecular bonds and the absence of precursors that could promote the uncontrolled formation of water on the surface. Etching of SiO2 with XeF2 has been shown to require the etching byproducts of elemental Si in close proximity.1 Both NOx and thermal SiO2 (TOx) films were etched with XeF2, titanium tetrachloride (TiCl4), and water vapor at different temperatures, pressures and process sequences. Samples were analyzed in situ with x-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD). The O 1s XPS spectrum in Fig. 1 after static XeF2 exposure at room temperature and 1 Torr showed a decrease in the O coverage to near the detection limit. The surface was visibly roughened by this process because the Si substrate was etched spontaneously by F atoms produced by the reaction of XeF2. Flowing XeF2 at a pressure below 10 mTorr, NOx was fluorinated without removing it and without roughening the underlying substrate. The fluorinated NOx was desorbed by heating above 677 °C. The TPD spectra in Fig. 2 show that F disrupted the oxide causing it to desorb beginning at about 190 °C. Si desorbed at this temperature likely as SiF4 based on the SiF3 daughter species observed. Control experiments showed that the onset of native oxide desorption was about 770 °C without XeF2. Atomic force microscopy (AFM) images showed that the surface roughness was unchanged by low pressure XeF2 and heating to high temperature.
In order to understand the reaction kinetics and reduce the high temperature anneal required for NOx removal, XeF2 was dosed at 120 °C and TiCl4 was used as a co-reactant because of the facile reaction that it undergoes with silanol groups. Three treatments of XeF2 at 120 °C removed all oxide as shown by the O 1s XPS spectra in Fig. 3. More controlled NOx removal was achieved via the introduction of TiCl4 prior to XeF2. The Ti 2p XPS spectra in Fig. 4 shows that TiO2 was formed after TiCl4 pulses at 250 °C, and the TiO2 was removed by XeF2 under continuous flow conditions. In addition, peak area ratios between O 1s and Si 2p states decreased by 20% after XeF2 exposure. Based on an initial thickness measured via ellipsometry of 15.8±0.2 Å, the amount of NOx etched was about 3 Å or approximately one monolayer. The surface was fluorinated after XeF2 exposure and unreactive to further TiCl4 pulses. Two process sequences were demonstrated for the controlled removal of NOx, one involving XeF2 and high temperature annealing and the other involving sequential doses of TiCl4 and XeF2.
1. Veyan, J.F.; Halls, M.D.; Rangan, S.; Aureau, D.; Yan, X.M.; Chabal, Y.J. J. Appl. Phys.
108, 114914 (2010).

Figure 1
(Invited) Divide Et Impera: Towards New Frontiers with Atomic Layer Etching
Authors: Lill Thorsten , Kanarik Keren J. , Tan Samantha S.H. , Shen Meihua , Pan Yang , Marks Jeffrey , Vahedi Vahid , Gottscho Richard A. 
Published: February 2020

Atomic layer etching (ALE) is rapidly emerging as a solution for advanced etch applications which require atomic scale fidelity /1/. In analogy to Atomic Layer Deposition (ALD), the ALE process is separated into two individual steps, one for surface modification and one for removal /2,3,4/. When these steps are saturated in time, intrinsic uniformity across the wafer and feature-to-feature as well as atomic level surface smoothness can be obtained. Separation of these steps also allows to reduce the ion energies in directional ALE which provides surface damage and selectivity benefits /4/.
Separation of complex continuous reactive ion etch (RIE) processes into simple, individual steps has profound implications. It is interesting to note the parallels to advanced mathematical algorithm development where so called “Divide and Conquer” algorithms break a complex problem into two or more sub-problems, until they can be solved and combined to give a solution to the original problem. In this talk we will discuss ALE in the context of the fundamentals of RIE, show the common roots and where ALE goes beyond RIE to allow new levels of performance and reduced complexity. The latter drives the need and opens the opportunity for better understanding of the surface reactions such as adsorption and sputtering. Latest experimental results will be shown for how dividing RIE processes into individual steps allows to conquer new heights of etch performance.

K.J. Kanarik, T. Lill, E. Hudson, S. Tan, S. Sriraman, J. Marks, V. Vahedi, R.A. Gottscho; J. Vac. Sci. Technol. A 33, 020802 (2015)

G.S. Oehrlein, D. Metzler, C. Li; ESC J. Solid State Technol. 4, N5041 (2015)

T. Faraz, F. Roozeboom, H.C.M. Knoops, W.M.M. Kessels; ESC J. Solid State Technol. 4, N5032 (2015)

S. Tan, W. Yang, K.J. Kanarik, T. Lill, V. Vahedi, J. Marks, R.A. Gottscho; ESC J. Solid State Technol. 4, N5010 (2015)
Spatial Atmospheric ALD of Functional Layers for CIGS Solar Cells
Authors: Illiberi A. , Frijters Corne , Balder Ellis , Poodt Paul , Roozeboom Fred 
Published: February 2020

Copper Indium Gallium di-Selenide (CIGS) solar cells are a promising approach in photovoltaic technology, having low production costs, high conversion efficiencies (> 20 %), as well as the possibility to manufacture them on flexible substrates. State-of-the-art in CIGS solar cells manufacturing is to use a stack of CdS, intrinsic ZnO (i-ZnO) and an Al-doped ZnO TCO on top of the CIGS film. Replacement of CdS by a non-toxic Cd-free layer with wider band gap (> 2.4 eV) would a) decrease the production cost by avoiding the expensive treatment of toxic wastes and b) increase the overall cell efficiency by enhancing the quantum efficiency in the blue range. Moreover, the use of a “soft” and highly conformal deposition technique is preferred to improve the electrical properties of the buffer layer/CIGS interface.
In this paper we present spatial atmospheric atomic layer deposition of a Zn(O,S) buffer layer as CdS replacement for CIGS solar cells. Spatial ALD is emerging as an industrially scalable deposition technique at atmospheric pressure which combines the advantages of temporal ALD, i.e. excellent control of film composition and uniformity on large area substrates, with high growth rates (up to nm/s). Films are grown by sequentially exposing the substrate to oxygen and sulfur precursors (H2O, H2S) and the zinc metal precursor (i.e., DEZn). By controlling the kinetics of surface reactions between evaporated precursors and reactive sites at the film surface, the composition of Zn(O,S) can be precisely tuned. The incorporation of S into ZnO results in a bowing of the band gap in the range from 3.3 eV (ZnO) to 2.7 (S/O+S ~ 0.5) and 3.4 eV (ZnS), as measured by spectrophotometry. The morphology of the Zn(Ox-1,Sx) films varies from polycrystalline (for 0<x<30 and 70<x<100) to amorphous (30<x<70), as measured by X-ray diffraction. CIGS solar cells with a Zn(O,S) buffer layer show an increased spectral response around 400 nm compared to solar cells with a CdS buffer layer. The solar cells with the Zn(O,S) buffer layer had an efficiency of 15.9 %, compared to 15.5 % for the reference solar cells with a CdS buffer layer.
(Invited) Engineered Combinations of Inorganic ALD/CVD Layers and Monomolecular Organic Films
Authors: Armini Silvia 
Published: February 2020

Capacitance scaling in damascene interconnects is achieved by introducing ultra-porous low dielectric constant materials. Nevertheless, one of the key issues in the integration of such porous materials is their inability to prevent gaseous penetration, e.g. during the metallization.
Several strategies are being followed to minimize the processing damage to the porous films during etching and ashing. The subsequent important step is to seal the pores at the surface, especially at the sidewalls after the trench and via etching. This is to prevent metal or precursor penetration during the metallization process, especially by advanced conformal deposition techniques such as chemical vapor deposition (CVD) and atomic layer deposition (ALD).
There are several routes to sealing: i) by thin film deposition; ii) by plasma-surface interaction; iii) by surface cross-linking/reconstruction. In this contribution, we report about the achievement of a complete pore sealing by combining a surface treatment of the low-k material together with self-assembled monolayers (SAMs) deposition and a low temperature ALD and CVD processes. In particular, CVD-based MnSixOy films are serious candidates for sub-25 nm-wide trench and via metallization technology because of their conformal nature and their ability to act as effective Cu diffusion barriers in the range of 1-2 nm thickness.
Self-assembled molecular nanolayers composed of sub-1 nm organic chains and terminated with desired functional groups are attractive for modifying surface properties for a variety of applications, such as lubricants, in nanolithography, corrosion protection and in the crystallization of biominerals. Monolayers can help engineering thin-film interfaces, both as active components in molecular devices, and as passive layers, inhibiting interfacial diffusion, promoting adhesion and toughening brittle nanoporous structures.
In this contribution, we report about the interaction between CVD and ALD films and organic thin films. Special attention is paid to selective ALD/CVD growth on functionalized surfaces having modulated surface energies.
Synthesis of Transition Metal Dichalcogenide WSe2thin Films By Atomic Layer Deposition
Authors: Zhang Kai , Chen Xin , Lin Pengtao , Rice Quinton , Abdel-Fattah Mahmoud , Seo Felix J. , Li Qiliang , Baumgart Helmut 
Published: February 2020

Two-dimensional layered transition metal dichalcogenides, such as MoS2, WSe2 and MoSe2 have received a lot of attention recently due to their promising unique thermal, mechanical, electrical, optical properties. Tungsten Diselenide (WSe2), one of the transition metal dichalcogenides of interest for 2-D electronic systems, exhibits not only good thermal stability and high melting point, but also excellent optical and electrical properties. WSe2 is a semiconductor with a bandgap which could be used for the fabrication of solar cells and LEDs of various colors [1, 2].
Many techniques have been developed for synthesis of WSe2 films on different substrates in recent years, such as sold state reaction, elctrodepositon, RF-magnetron sputtering, electrodepostion, pulsed laser depostion, chemical vapor depositon. However, there are very few references that report atomic layer deposition (ALD) results of WSe2 films. This technique exhibits self-limiting surface reactions, which means accidental overdosing of precursors does not result in increased film deposition on the substrate surface. This self-terminating character is able to accurately control thickness and composition of ultra thin films and achieves uniformity, conformality and even monolayers of transition metal dichalcogenides.
Here we report on a large-area synthesis of WSe2 films on native oxide covered and hydroxyl terminated Si substrates by using the Savannah 100 ALD system from Ultratech/Cambridge Nanotech. Tungsten hexacarbonyl (W(CO)6) and (trimethylsilyl) selenide ((Me3Si)2Se) are employed as the chemical ALD precursors for Tungsten and selenium, respectively. Generally 20 sccm N2 was used as a carrier gas for the precursors. The growth temperature was set at 275, 300 and 325oC. The crystal structure and chemical composition of WSe2 films were identified by using X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS). The film morphology was characterized by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The optical property was analyzed by Raman spectroscopy and photoluminescence (PL) spectroscopy. The strong Raman scattering of in-plane E1
2g and out-of-plane A1g vibration modes, and the dominant PL of direct transition from Kc to Kv and indirect transition from Λc to Γv with absence of Kc to Γv are typical optical spectra of layered WSe2. The reduction of out-of-plane vibration mode and the absence of PL from indirect transition provide the evidence of fewer layer WSe2.
References:

H. Wang, D. Kong, P. Johanes, J. J. Cha, G. Zheng, K. Yan, N. Liu, and Y. Cui, Nano Lett. 13, 3426 (2013).

C. Huang, S. Wu, A. M. Sanchez, J. J. P. Peters, R. Beanland, J. S. Ross, P. Rivera, W. Yao, D. H. Cobden and X. Xu, Nature materials 13, 1096 (2014).

Figure 1
On the Growth of Silver Thin Films By Atmospheric-Plasma Spatial ALD
Authors: Mameli Alfredo , van den Bruele Fieke , Kessels W.M.M. , Roozeboom Fred 
Published: February 2020

Silver nanoparticles and thin-films are gaining attention for plasmonics applications in photovoltaics[1] and optical lithography[2], amongst others. However, the growth of ultra-thin noble metals films is generally challenging due to their high surface energy that hinders the wetting on the substrate. In this work we investigated the influence of substrates with different surface energy on the nucleation and growth evolution of silver thin films deposited by atmospheric-pressure plasma enhanced spatial Atomic Layer Deposition (ALD) in a rotary reactor(Fig.1)[3].
The ultra-thin Ag films were deposited using Ag(fod)(PEt3), triethylphosphine (6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate silver(I), as the precursor and an H2/N2 plasma generated by a surface dielectric barrier discharge (SDBD) source as the co-reactant. Silver thin films were deposited at 120 °C with a rotation speed of 40 rpm. Ag(fod)(PEt3) was evaporated into the deposition chamber using Ar as carrier gas flowing at 100 sccm, at the same temperature as that of the reactor. The H2/N2 co-reactant gas mixture was composed from 800 sccm H2 and 600 sccm N2. Two substrates were used: crystalline Si (100) and borosilicate glass, with and without sputter-deposited molybdenum as a wetting layer.
Molybdenum films are known to have high surface energy (3 Jm-2)[4]. Thus Ag is expected to wet a Mo film better than a bare Si surface. To verify this, the differences in the growth mode of Ag Mo wetting layers were investigated on the basis of electrical, optical and morphological properties as analyzed by four-point probe (4PP), spectroscopic ellipsometry (SE) and SEM imaging (Fig. 2), respectively. Preliminary results show that the coalescence of the Ag film is more facile on 80 nm Mo/Si than on bare Si. In the case of Ag thin film growth on an 80 nm Mo wetting layer on top of Si, the Ag sheet resistance derived from 4PP measurements shows that percolation is readily achieved. Going from bare Si substrate to Mo thin film substrate, the sheet resistance drops from ~10 Ω/□ to ~3.5 Ω/□. In the case of a bare Si surface for different exposure times the measured sheet resistance, the increasing contribution of the Drude tail in the SE analysis and the SEM inspection all indicate that bare Si delays the onset of layer-by-layer growth of closed Ag thin films, leading to a Volmer-Weber island growth mode. Furthermore, the effect of the wetting layer has been investigated in greater detail, by varying its thickness from a 10 nm non-coalesced Mo film to an 80 nm closed one.

Figure 1
Contamination Specifications, an Overall Perspective
Authors: Mertens Paul W 
Published: February 2020

Specifications on residual contamination have played a determining role in the development of cleaning processes. The intention of this contribution is to reflect on contamination specifications and show a potential route of how to proceed. One major platform for specifications is the ITRS [1], where a set of different contamination specifications are posted.
Currently, particle specifications are as follows. For 20 nm half pitch technology nodes the critical particle diameter is 10 nm. It should be noticed that a Si sphere with a diameter of 10 nm consist of only 25000 Si atoms.
The maximum surface concentration , is derived from the assumption that it should correspond to a yield number of 99.9 for an active area of 0.1 cm2. If one assumes that each particle with a size equal or larger than the critical value leads to one defect. This should leads to the following specification: particle density < 0.01/cm2. This specification is represented in Fig. 1 (as the a corner of the red-area). It should be noted that both specifications for diameter and particle density are (orthogonal in the sense) obtained in totally independent ways.
When specifying particles, one should realise that a particular size (and concentration) may only be a temporary embodiment of an amount of contamination.. Small particles can agglomerate to larger ones or alternatively large particles (e.g. flakes) can fragment into many smaller pieces. Through various processes.
If one assumes the total volume is maintained, it implies that contamination could evolve along the slanted lines (isochores) as indicated in the diagram of Fig. 1 This would mean that contamination situations that are within specification (green) could evolve to out-of specification conditions (red)even when the total amount (volume) of contamination remains constant.
Another specification that is used is the surface concentration of molecular dispersed O and C on the surface of 1e12/cm2. This specification has been added to the diagram, by using the Van der Waals diameter of the atoms for the horizontal coordinate.
One can see that the total contamination volume represented by the O- and C-specification is several orders of magnitude higher than that for the small particles. In other terms the amount of contamination allowed in particles is much smaller than the amount that can be tolerated as molecular contaminant on the surface.
Finally, fig 2 shows a possible alternative specification of the total amount of impurities on the surface (irrespective of its morphology).
References:
[1] ITRS 2013 edition, http://www.itrs.net/.

Figure 1
Submicron Particle Removal during FPD Oxide TFT Process
Authors: Lee Jun , Kim Min-Su , Kim Hyun-Tae , Choi In-Chan , Kim Woo-Young , Lim Dae-Seung , Park Jin-Goo 
Published: February 2020

Recently, panel size has become increasingly large reaching the 8th generation (2200mm × 2500mm) and there is a trend that is changing from a-Si TFT (amorphous-Si Thin Film Transistor) to oxide TFT because of a demand for high resolution display and an expansion of OLED (Organic Light Emitting Diodes) industry. In previous panel manufacturing processes, cleaning process was not so important. However, nowadays pixel size is becoming smaller and the number of pixels per unit area is gradually increasing due to the high resolution. Consequently, an influence of submicron sized contaminated particles is increasing, so the importance of cleaning process has increased. In the oxide TFT, to achieve the high resolution, Cu based gate structure having a low resistance characteristic is necessary and in order to prevent a leakage current through the active layer, SiO2 deposition is needed on a gate insulator layer and ITO (Indium Tin Oxide) layer is used as a transparent electrode. For a large area and high resolution panel with a good production yield, a research on an effective cleaning process which can remove the submicron contaminated particles deposited on the Cu, SiO2and ITO surfaces during a TFT manufacturing process, is required. Generally, physical cleaning processes are used to remove the submicron particles in FPD (Flat Panel Display) process. Among them, a research on an eco-friendly physical cleaning processes such as DI water megasonic, mixing-jet, brush and electrolyzed ionized water (EIW) is actively being carried out.
In this study, we have optimized these cleaning processes to remove the submicron particles from the substrate surface. The primary objective is to establish an optimal cleaning process by applying above processes for the Cu, SiO2 and ITO substrates. And a mechanism of cleaning process and a theoretical understanding of interaction force such as van der Waals force, zeta potential and electrostatic force between the particle and substrate for the optimization of particle cleaning are studied. In the course of the experiment, the particles (glass and aluminum) which were produced in TFT manufacturing process were intentionally deposited on the Cu, SiO2 and ITO substrate surface. And then, the cleaning test using megasonic (1 MHz and 250 W), mixing-jet (570 lpm CDA and 4 lpm DI water), brush (diamond shape) and EIW (pH 10.2 and -790 mV ORP) processes was conducted. After that, we evaluated the cleaning efficiency by counting the number of particles on the surface before and after the cleaning test using an optical microscope. As a result, we achieved a high cleaning efficiency of above 95% in the electrolyzed ionized water cleaning process by applying the megasonic cleaning on all substrates.

Figure 1
Removing Organic Residues Using Backside Brush Scrubber Clean
Authors: Chauhan Kripa Nidhan , Sih Vincent , Bhat Talapady , Kang Min Hyo , Kabutoya Eiji , Cheng Gordon 
Published: February 2020

Cleaning is an important part of advanced semiconductor manufacturing process. As the technology node advances, it has become more and more challenging. In 2X nm devices, excursions of organic residues are detected on the product wafers. These clusters of organic residues are found to be die killers and hence, reduce the yield of the product.
In this work, we will focus on root cause finding for the organic residue clusters and the proposed solution. Defectivity, electrical, and yield data are presented to show the effectiveness of the proposed solution. Figure 1 shows defectivity improvement of 11X as compared to the current integration scheme. Figure 2 is typical example of organic residues and cluster on wafers. Figure 3 shows the comparison of chemistries applied. Figure 4 demonstrates the product yield improvement of 3.1% after the introduction of the proposed solution.

References

H.-S. Sohn et.al
Removal of Backside Particles by Single Wafer Magasonic Systems, ECS transactions, 11(2) 95-100 (2007)

Antoine Pacco et.al
Focus Spot Reduction by Brush Scrubber Cleaning, Solid State Pheonomena Vol 219, 276-279 (2015)

Figure 1