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This article reports Si-passivated Ge nFinFETs with significantly improved GmSAT/SSSAT and positive bias temperature instability (PBTI) reliability enabled by an improved replacement metal gate (RMG) high- ${k}$ last process. SiO2 dummy gate oxide (DGO) deposition on Ge fin is shown to form (Si x )Ge1- x O y , which is, compared to a pure SiO2, more difficult to remove completely during the dry clean prior to the gate-stack formation. By extending the DGO removal clean, improved PBTI reliability, reduced ${D}_{{\text {IT}}}$ , and increased electron mobility are demonstrated. Moreover, by suppressing the Ge channel oxidation through the choice of less-oxidizing DGO or inserting an Si-cap layer prior to the DGO deposition, a greatly improved long-channel electron mobility is obtained at a scaled fin width. Finally, together with the PBTI maximum ${V}_{{\text {OV}}}$ of 0.13 V, the best GmSAT/SSSAT of 5.4 is achieved, which is today’s record value among the sub-100-nm- ${L}_{g}$ n-channel Ge Fin and gate-all-around nanowire FETs. These results clearly show the importance of the pre-gate-stack channel surface preparation on the scaled Ge FinFETs to benefit from a previously optimized Si-passivated Ge gate-stack.

Alkyl-terminated surfaces have received significant interest as growth-blocking surfaces in area-selective deposition (ASD). Gas-phase chemical functionalization is attractive in this context due to its short process times, potentially wide applicability, and ease of integration in industrial process flows. However, the relation between the surface chemistry, the passivating agent, and the growth-blocking efficacy of such treatments is not well understood which can lead to suboptimal passivation performance. This work investigates the reaction between dimethylamino-trimethylsilane (DMA-TMS) and SiO2 surfaces with varying composition, and identifies the impact of surface composition on passivation efficacy and selectivity. DMA-TMS reacts rapidly with Si–OH groups on SiO2 in a self-limiting surface reaction, resulting in an –O–Si(CH3)3 covered surface. In contrast, Si–O–Si groups are either unreactive or significantly less reactive towards DMA-TMS. Increasing the number of Si–OH versus Si–O–Si groups on the initial SiO2 surface therefore results in a higher –O–Si(CH3)3 density after DMA-TMS treatment. As a consequence, the selectivity of an ASD process towards SiO2 improves, as demonstrated for ruthenium atomic layer deposition from 1-ethylbenzyl-1,4-cyclohexadienyl-ruthenium and oxygen. This work illustrates the impact of tuning surface composition on passivation and selectivity for ASD.

Research on carbon nanotube (CNT) films for the EUV pellicle application was initiated at imec in 2015 triggered by the remarkable optical, mechanical, and thermal properties of the CNT material. Today the advancement of the CNT material synthesis together with matured methods to fabricate thin CNT membranes make free-standing CNT films a very promising EUV pellicle candidate for high volume EUV lithography. Balancing the CNT material properties for the optimal pellicle performance in EUV scanners remains the ongoing research focus. Depending on the density and morphology of the CNTs within the film and individual CNT parameters, like number of walls, bundle size, metal catalyst content, purity etc., the optical and thermal properties of the CNT pellicle can be tuned. It is critical for the pellicle to be stable in the EUV lithography scanner environment which includes hydrogen plasma and heat loads associated with high powers beyond 250 W. Different types of CNTs, i.e. single-, double-, multi-walled CNTs and their combinations, are explored as building blocks of an optimized pellicle membrane. Optical properties of different pellicles and their ability to withstand high EUV powers in the hydrogen-based environment were tested. Transmission, spectroscopic and chemical composition mapping of the exposed free-standing CNT films are used to study the material changes that occur in the scanner-like environment. A solution is needed to extend the CNT pellicle lifetime and coating is discussed as a potential approach to protect the CNT material from hydrogen plasma damage.

© 2018 Elsevier B.V. Retrieving molecular information by sputtering of organic systems has been concretized in the last years due to the introduction of sputtering by large gas clusters which drastically eliminated the compound degradation during the analysis and has led to strong improvements in depth resolution. Rapidly however, a limitation was observed for heterogeneous systems where inorganic layers or structures needed to be profiled concurrently. As opposed to organic material, erosion of the inorganic layer appears very difficult and prone to many artefacts. To shed some light on these problems we investigated a simple system consisting of aluminum delta layer(s) buried in a silicon matrix in order to define the most favorable beam conditions for practical analysis. We show that counterintuitive to the small energy/atom used and unlike monoatomic ion sputtering, the information depth obtained with large cluster ions is typically very large (∼10 nm) and that this can be caused both by a large roughness development at early stages of the sputtering process and by a large mixing zone. As a consequence, a large deformation of the Al intensity profile is observed. Using sample rotation during profiling significantly improves the depth resolution while sample temperature has no significant effect. The determining parameter for high depth resolution still remains the total energy of the cluster instead of the energy per atom in the cluster. ispartof: Applied Surface Science vol:444 pages:633-641 status: published

Layers composed of binary blends of a polymer and a fullerene derivative are at the heart of bulk heterojunction organic photovoltaic cells. The efficiency and stability of these devices critically depend on the distribution of the polymer and fullerene materials within the blend layer. Whereas time-of-flight secondary ion mass spectrometry, particularly in combination with cluster ion beams, has frequently been used to probe similar organic materials, the quantification of the results is often missing due to a lack of understanding of all the parameters influencing the measurement results. This study contributes to improved quantification by exploring the role of the bulk composition and interfacial material on parameters such as sputtering yield, mass fragmentation, and ionization. We show that the argon cluster sputtering yields of these materials may be described by two widely acknowledged sputtering yield relationships. Their fitting parameters depend on the layer composition in a manner that is consistent with a lower energy required for sputtering of layers with higher fullerene derivative content. Similarly, we show that changes in composition impact the ion yields nonlinearly, which is an important source of quantification uncertainty. We provide evidence that, for the case of the fullerene derivative mixed with different donor materials, the matrix effect (i.e., the deviation from a linear response) correlates linearly with the electronegativity of the species in the donor material. Finally, with respect to the quantification of the composition at the interface with the substrate, we present a charge transfer mechanism that describes observed enhancements of the secondary ion intensities. ispartof: Journal of Physical Chemistry C vol:120 issue:49 pages:28074-28082 status: published

The epitaxial growth of Si layers on Si substrates in the presence of O atoms is generally considered a challenge, as O atoms degrade the epitaxial quality by generating defects. Here, we investigate the growth mechanisms for Si epitaxy on O atomic layers (ALs) with different O-contents and structures. O ALs are deposited by ozone (O3) or oxygen (O2) exposure on H-terminated Si at 50 °C and 300 °C respectively. Epitaxial Si is deposited by chemical vapor deposition using silane (SiH4) at 500 °C. After O3 exposure, the O atoms are uniformly distributed in Si-Si dimer/back bonds. This O layer still allows epitaxial seeding of Si. The epitaxial quality is enhanced by lowering the surface distortions due to O atoms and by decreasing the arrival rate of SiH4 reactants, allowing more time for surface diffusion. After O2 exposure, the O atoms are present in the form of SiOx clusters. Regions of hydrogen-terminated Si remain present between the SiOx clusters. The epitaxial seeding of Si in these structures is realized on H-Si regions, and an epitaxial layer grows by a lateral overgrowth mechanism. A breakdown in the epitaxial ordering occurs at a critical Si thickness, presumably by accumulation of surface roughness.

For patterned TiN/silicon oxide/low-k dielectric stack, fluorinated etch residues were detected on the TiN surface, the dielectric sidewall and bottom, regardless of the low-k material used in the stack. XPS results showed that they consisted of polymer-based (CFx) residues deposited on trench sidewall and bottom, and metal-based (TiFx) residues mainly deposited on top surface. In terms of post-etch residue removal, the efficiency of various wet clean solutions can be clearly distinguished for CFx, and TiFx using the same patterned porous low-k stack. These results also demonstrate that the removal of both TiFx and CFx residues generated during the plasma is possible in one step with optimized chemical and process.

The deposition of ultra-thin tungsten films and their related 2D chalcogen compounds on large area dielectric substrates by gas phase reactions is challenging. The lack of nucleation sites complicates the adsorption of W-related precursors and subsequent sulfurization usually requires high temperatures. We propose here a technique in which a thin solid amorphous silicon film is used as reductant for the gas phase precursor WF6 leading to the conversion to metallic W. The selectivity of the W conversion towards the underlying dielectric surfaces is demonstrated. The role of the Si surface preparation, the conversion temperature, and Si thickness on the formation process is investigated. Further, the in situ conversion of the metallic tungsten into thin stoichiometric WS2 is achieved by a cyclic approach based on WF6 and H2S pulses at the moderate temperature of 450 °C, which is much lower than usual oxide sulfurization processes. ispartof: Journal of Materials Chemistry C vol:6 issue:15 pages:4122-4130 status: published

© 2015 Elsevier B.V. All rights reserved. The impact of different Ru precursors and/or deposition methods on the electrical characteristics of Ru/SrTiOx/Ru capacitors has been investigated. The observed increase of the leakage current density (Jg) and the equivalent oxide thickness (EOT) for ALD (atomic layer deposition) deposited Ru layers compared to PVD (physical vapor deposition) deposited ones was found to be caused by a SrRuTiOx layer formation at the SrTiOx/Ru interface aided by the presence of the oxygen co-reactant used during the ALD, regardless of the precursor used. publisher: Elsevier articletitle: Understanding the EOT–Jg degradation in Ru/SrTiOx/Ru metal–insulator–metal capacitors formed with Ru atomic layer deposition journaltitle: Microelectronic Engineering articlelink: http://dx.doi.org/10.1016/j.mee.2015.04.076 content_type: article copyright: Copyright © 2015 Elsevier B.V. All rights reserved. ispartof: Microelectronic Engineering vol:147 pages:108-112 ispartof: location:ITALY, Udine status: published

Epitaxial Si-O superlattices consist of alternating periods of crystalline Si layers and atomic layers of oxygen (O) with interesting electronic and optical properties. To understand the fundamentals of Si epitaxy on O atomic layers, we investigate the O surface species that can allow epitaxial Si chemical vapor deposition using silane. The surface reaction of ozone on H-terminated Si(100) is used for the O deposition. The oxygen content is controlled precisely at and near the atomic layer level and has a critical impact on the subsequent Si deposition. There exists only a small window of O-contents, i.e. 0.7–0.9 atomic layers, for which the epitaxial deposition of Si can be realized. At these low O-contents, the O atoms are incorporated in the Si-Si dimers or back bonds (-OSiH), with the surface Si atoms mainly in the 1+ oxidation state, as indicated by infrared spectroscopy. This surface enables epitaxial seeding of Si. For O-contents higher than one atomic layer, the additional O atoms are incorporated in the Si-Si back bonds as well as in the Si-H bonds, where hydroxyl groups (-Si-OH) are created. In this case, the Si deposition thereon becomes completely amorphous.

For almost sixty years, solar energy for space applications has relied on inorganic photovoltaics, evolving from solar cells made of single crystalline silicon to triple junctions based on germanium and III-V alloys. The class of organic-based photovoltaics, which ranges from all-organic to hybrid perovskites, has the potential of becoming a disruptive technology in space applications, thanks to the unique combination of appealing intrinsic properties (e.g. record high specific power, tunable absorption window) and processing possibilities. Here, we report on the launch of the stratospheric mission OSCAR, which demonstrated for the first time organic-based solar cell operation in extra-terrestrial conditions. This successful maiden flight for organic-based photovoltaics opens a new paradigm for solar electricity in space, from satellites to orbital and planetary space stations. The OSCAR project was developed in the framework of the REXUS/BEXUS program, supported by the Swedish National Space Board (SNSB), the Deutsches Zentrum fur Luft- und Raumfahrt (DLR), the European Space Agency (ESA), and the Swedish Space Corporation. The authors deeply thank M. De Roeve, R. Lempens, J. Soogen, K. Daniels and J. Mertens for the technical help, and K. Wouters and M.A. Beynaerts for their support during testing. IMEC vzw is acknowledged for their availability with sample supplies and encapsulation. For the small molecule based devices thanks are due to TU/Dresden. The authors would like to thank UHasselt for additional financial support. The HERCULES Foundation financially supported the TOF-SIMS analysis. Thanks are also due to singer/song writer/astronomer Stijn Meuris for the support and for the partial use of the "Satelliet S.U.Z.Y." lyrics during pre-launch divulgation.

Medium energy ion scattering (MEIS) using, typically, 100–200 keV H+ or He+ ions derives it ability to characterise nanolayers from the fact that the energy after backscattering depends (i) on the elastic energy loss suffered in a single collision with a target atom and (ii) on the inelastic energy losses on its incoming and outgoing trajectories. From the former the mass of the atom can be determined and from the latter its depth. Thus MEIS yields depth dependent compositional and structural information, with high depth resolution (sub-nm near the surface) and good sensitivity for all but the lighter masses. It is particularly well suited for the depth analysis of high-k multilayers of nanometer thickness. Accurate quantification of the depth distributions of atomic species can be obtained using suitable spectrum simulation.\ud \ud In the present paper, important aspects of MEIS including quantification, depth resolution and spectrum simulation are briefly discussed. The capabilities of the technique in terms of the high depth resolution layer compositional and structural information it yields, is illustrated with reference to the detailed characterisation of a range of high-k nanolayer and multilayer structures for current microelectronic devices or those still under development: (i) HfO2 and HfSiOx for gate dielectric applications, including a TiN/Al2O3/HfO2/SiO2/Si structure, (ii) TiN/SrTiO3/TiN and (iii) TiO2/Ru/TiN multilayer structures for metal–insulator–metal capacitors (MIMcaps) in DRAM applications.\ud \ud The unique information provided by the technique is highlighted by its clear capability to accurately quantify the composition profiles and thickness of nanolayers and complex multilayers as grown, and to identify the nature and extent of atom redistribution (e.g. intermixing, segregation) during layer deposition, annealing and plasma processing. The ability makes it a valuable tool in the development of the nanostructures that will become increasingly important as device dimensions continue to be scaled down.

The initial growth stages of boron-doped diamond, deposited by hot-filament chemical vapour deposition (HFCVD), are crucial for the conductivity of moulded tips used in scanning spreading resistance microscopy (SSRM) where the first grown layer is the active layer of the tip. In this paper, we investigate therefore the beginning of the growth by interrupting the HFCVD process for nano-crystalline (NCD) and microcrystalline diamond (MCD) films at various moments during the filament carburisation. The characterisation of these initial stages is done by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). A slow growth start after the first ∼20 min of carburisation is revealed by the change of C-bindings at the seed surface towards pure CC indicated by XPS. AFM measurements show that the actual growth starts after ∼40 min. Our work shows that boron tends to form BO clusters at the beginning of the growth (∼50 min) which can affect the conductivity of the first layers of our tips. By using carburised filaments the diamond seeds form earlier more pronounced crystal shapes which are related to a higher sp3/sp2 ratio. This is advantageous for moulded diamond tips used in electrical probing.

The surface chemistry and the interface formation during the initial stages of the atomic layer deposition (ALD) of Al2O3 from trimethylaluminum (TMA) and H2O on InP(100) were studied by synchrotron radiation photoemission spectroscopy and scanning tunneling microscopy. The effect of the ex situ surface cleaning by either H2SO4 or (NH4)2S was examined. It is shown that the native oxide on the InP surface consisted mainly of indium hydrogen phosphates with a P enrichment at the interface with InP. After a (NH4)2S treatment, S was present on the surface as a sulfide in both surface and subsurface sites. Exposure to TMA led to the formation of a thin AlPO4 layer, irrespective of the surface cleaning. The surface Fermi level of p-type InP was found to be pinned close to midgap after H2SO4 cleaning and moved only slightly further toward the conduction band edge upon TMA exposure, indicating that the AlPO4/InP interface was rather defective. (NH4)2S passivation led to a Fermi level position of p-type InP close ...

A fluorocarbon polymer generated by plasma polymerization of CF4/CH2F2 used as a model polymer for sidewall residues was subjectedtoultraviolet(UV)irradiation(λ =254nm).FouriertransforminfraredspectroscopyandX-rayphotoelectronspectroscopy indicated that the as-deposited fluorocarbon polymer mainly contains CF, CF2, and a small concentration of unsaturated, fluorinated C=C bonds, and carbonyl functionalities. A partial removal of the polymer occurred during UV irradiation in oxygen. Experimental results showed that UV irradiation resulted in a slight decrease influorine content concomitant with the formation of carbonyl groups. The presence of reactive species such as oxygen during UV treatment (by production of singlet oxygen and radicals) was necessary to allow bond cleavage and an increase of hydrophilicity of the polymer fragments thus making the removal of the polymer possible in a subsequent wet clean. In terms of polymer bonding structure, the presence of C=C bonds and oxygen in the polymer backbone, in particular of C-O bonds, was crucial for light absorption at the wavelength used and played a key role in the bond scissioning process. Quantum chemical calculation was also performed to support the experimental results.

A novel multi work function process is used to demonstrate up to 250 mV effective work function shifts of nMOS devices. The process use SiH 4 -soak of ALD TiN to change its barrier properties with ALD TiAl. FinFET devices are demonstrated with ∼100 mV V T -shift for 24-nm-L G devices resulting in 20× reduction in off-state leakage at unaffected sub threshold slope and improved mismatch behavior. A patterning scheme using an nMOS first RMG process is proposed and demonstrated.

The atomic layer deposition of titanium oxide TiO2 on ruthenium and oxidized ruthenium with titanium methoxide as metal precursor and H2O and O3 as oxidant was investigated by Rutherford backscattering (RBS) and time of flight secondary ion mass spectrometry (TOFSIMS). An ultra-thin layer of TiO2 deposited a priori with H2O plays the role of protection of Ru(Ox) substrates against etching by O3. Information about thin films (~3 nm) interfacial reactions, thickness and structure was brought by Medium Energy Ion Scattering Spectroscopy (MEIS) and X-ray absorption spectroscopy (XAS) measurements. The growth enhancements observed in the first stages of the deposition depends on the pre-treatment (pre-oxidation, H2O based interlayer thickness) of the Ru substrate. Thick films (~14 nm) were analyzed by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The as deposited TiO2 films are crystalline with rutile structure, as resulted from structural analyzes. However, the presence of small amounts of anatase was detected by soft X-ray absorption spectroscopy (XAS) and is strongly influenced by the surface pre-treatment of the Ru substrate. The electrical properties (equivalent oxide thickness and leakage current density) correlate with a different rutile/anatase ratio present in the films.

The atomic layer deposition (ALD) of Ta2O5 and TaSiOx from TaCl5, SiCl4, and H2O is reported. Both processes are influenced by the concomitant etching of Ta2O5 and TaSiOx by TaCl5. The optimum deposition temperature is found to be 250 °C for both Ta2O5 and TaSiOx. For lower deposition temperatures, the large Cl contamination leads to poor dielectric properties of the films, whereas higher temperatures lead to poor within-wafer (WiW) thickness non-uniformity due to etching. Si incorporation is limited to Si/(Si + Ta) ∼ 0.65 because of the slow adsorption kinetics of SiCl4 on SiOH-terminated surfaces. Under optimum conditions, amorphous films with good dielectric quality are obtained.

Since silicon will ultimately face physical limitations, germanium and III-V materials, such as Ga, GaAs, InGaAs, are being extensively investigated for their high electron and hole mobility advantages. Prior to implementing germanium or III-V materials, it is believed that SiGe with high Ge concentration will be applied for channel materials in pMOS devices with high-k and metal gates in order to simultaneously adjust the work function and to increase the hole mobility. However, introduction of new channel materials leads to new challenges and substantial changes in the FEOL process flow.

Thin LuxAl2−xO3 films were deposited by atomic-layer deposition using Lu(thd)3, and TMA in combination with O3 as oxidizer. High-quality dielectric films were obtained with good process con-trol. The full range of the Lu/(Lu+Al) composition was found to be accessible. The films showed bulk density and low roughness. As a result, this process enables the study of LuxAl2−xO3 as dielectric in advanced non-volatile memory devices.

For future generations of non-volatile memory applications, the replacement of the interpoly dielectric by a suitable high-k material is required. Rare-earth aluminates are potential candidates because they are predicted to combine a high dielectric permittivity with a large band gap. We demonstrate the atomic layer deposition (ALD) of GdxAl2-xO3 layers using Gd( i PrCp)3, trimethyl-aluminum (TMA), and H2 Oo r O3. Process windows for both H2O and O3 as oxidants are explored. H2O is shown to lead to better GdxAl2-xO3 film properties than O3, although the accessible composition range is limited because of the hygroscopic nature of Gd2O3.

Nitrogen depth profiling in a high-k gate stack structure, SiON/HfO2/SiON/Si(0 0 1) was performed by high-resolution Rutherford backscattering spectroscopy (HRBS) in combination with angle-resolved X-ray photoelectron spectroscopy (AR-XPS). The nitrogen depth profile is determined so that both the HRBS spectrum and the angular dependence of the XPS yield are reproduced. The obtained nitrogen profile is compared with the result of high-resolution elastic recoil detection (ERD) which is the most reliable technique for depth profiling of light elements. The agreement between the result of the present combination analysis and that of high-resolution ERD is fairly good, showing that the present combination analysis is a promising method for the analysis of light elements.

Using reference-free X-ray fluorescence analysis (XRF) in different geometries carried out in the laboratory of the Physikalisch-Technische Bundesanstalt at the electron storage ring BESSY II in Berlin various nanolayered systems have been investigated. As an example the investigation of Hf containing thin oxide layers is shown. For comparison reasons these samples have been also measured by X-ray reflectometry (XRR) in the PTB laboratory and by other partners within the ANNA project, which confirmed the thickness of the Hf containing top layers determined by XRF within their respective uncertainties. The XRF spectra were deconvolved employing the detector response functions to deduce the intensity of the corresponding Hf L3 fluorescence lines. The investigation of nanolayered systems especially in the lower energy range shows advantages, like different absorption conditions which allow for better dynamics and the suppression of the silicon fluorescence signal from the substrate, but needs more effort in determining the respective fundamental parameters.

We present a detailed characterization of thin high-k Hf-based dielectric/SiO2 stacks on Si by electrical measurements (capacitance - voltage (C-V) and current-voltage (I-V)), structural analysis using transmission electron microscopy (TEM) and compositional analysis using medium energy ion scattering (MEIS). We show that the electrical results are consistent with and can be explained by the structural and compositional results. Specifically, the structural results show that the effect of nitridation of the films using a decoupled plasma nitridation method is an increase in SiO2 thickness, which results in a capacitance and leakage current decrease, revealed by the electrical measurements. Nitridation also reduces the density of interface traps for these samples. The reduction is more effective in the case of nonstoichiometric hafnium silicate films (HfSiOx) than in the case of HfO2.

Reducing the energy of the primary ions will improve the depth resolution in SIMS depth profiling. At ultra low energies ( + ions, which are commonly used for their enhancement of negative secondary ion formation, and discuss the impact of these extreme conditions on the steady state surface concentration of cesium. In contrary to what is found from sputtering-based retention models, the steady state surface concentration of (retained) cesium on silicon reaches a maximum value in the order of 15 at%.

The Physikalisch-Technische Bundesanstalt (PTB), Germany's national metrology institute, developed an alignment strategy to specify elemental depth profiling in vertical sidewall layers on structured wafers. For this purpose, PTB's irradiation chamber for 200 mm and 300 mm silicon wafers was used to combine total-reflection X-ray fluorescence (TXRF) and grazing incidence XRF (GIXRF) techniques by employing monochromatized undulator radiation of the BESSY II electron storage ring. 3-D test structures were fabricated to develop an optimal alignment strategy allowing for depth profiling in such nanolayers. The test structures consisted of silicon bars with widths/spacings either in the μm or in the nm range. In order to be able to differentiate the sidewalls more easily from the remainder of the structures, they were provided with an additional silicon nitride layer. Four structure types of different bar width and density parameters on two 200 mm silicon wafers were investigated. The alignment procedure developed in the present work consists of three main steps and allows for distinct excitation of multiple sidewalls of one kind. Information about depth-dependent sidewall contamination, layer thickness and composition can be obtained by this approach. First results obtained on these test structures demonstrate the application potential of this new technique. In principle, depth-dependent chemical speciation should also be possible using GIXRF in combination with near edge absorption X-ray fine structure (NEXAFS).

The replacement of poly-silicon by metallic compounds in the gate stack leads to the search of metals with suitable work function. However, it is observed that thermal budget has a large influence on the effective work functions of several metals. In this paper, we investigated the possible modification of the chemical states by physical analysis techniques (XPS, XRR, MEIS, TOF-SIMS) by studying the chemistry of the high-k oxide/metal interface. We show that in the case of the TiN/TaN/HfO2/SiO2/Si stack, several modifications occur upon 1000oC N2 annealing: Increase of the nitrogen content of the TaN, interdiffusion of the Ti and TaN, and formation of Ta2O5 at the TaN/HfO2 interface.

Atomic layer doping of phosphorus (P) and arsenic (As) into Si was performed using the vapor phase doping (VPD) technique. For increasing deposition time and precursor gas flow rate, the P and As doses tend to saturate at about 0.8 and 1.0 monolayer of Si, respectively. Therefore, these processes are self-limited in both cases. When a Si cap layer is grown on the P-covered Si(001), high P concentration of 3.7 × 1020 cm-3 at the heterointerface in the Si-cap/P/Si-substrate layer stacks is achieved. Due to As desorption and segregation toward the Si surface during the temperature ramp up and during the Si-cap growth, the As concentration at the heterointerface in the Si-cap/As/Si-substrate layer stacks was lower compared to the P case. These results allowed us to evaluate the feasibility of the VPD process to fabricate precisely controlled doping profiles.

A ternary WN"xC"y system was deposited in a thermal ALD (atomic layer deposition) reactor from ASM at 300^oC in a process sequence using tungsten hexafluoride (WF"6), triethyl borane (TEB) and ammonia (NH"3) as precursors. The WC"x layers were deposited by a novel ALD process at a process temperature of 250^oC. The WN"x layers were deposited at 375^oC using bis(tert-butylimido)-bis-(dimethylamido)tungsten (^tBuN)"2(Me"2N)"2W (imido-amido) and NH"3 as precursors. WN"x grows faster on plasma enhanced chemical vapor deposition (PECVD) oxide than WC"x does on chemical oxide. WN"xC"y grows better on PECVD oxide than on thermal oxide, which is opposite of what is seen for WN"x. In the case of the ternary WN"xC"y system, the scalability towards thinner layers and galvanic corrosion behavior are disadvantages for the incorporation of the layer into Cu interconnects. ALD WC"x based barriers have a low resistivity, but galvanic corrosion in a model slurry solution of 15% peroxide (H"2O"2) is a potential problem. Higher resistivity values are determined for the binary WN"x layers. WN"x shows a constant composition and density throughout the layer.

A pFET threshold-voltage (Vt) reduction of about 200 mV is demonstrated by inserting a thin Al2O3 layer between the high-k dielectric and the TiN gate without noticeable degradation of other electrical properties. HfSiOpropcapped with 9 Aring of thin Al2O3obtains a low long-channel Vt of -0.37 V (the lowest among those with TiN gate), a high mobility of 59 cm2 /V ldr s at 0.8 MV/cm (92% of universal value), a negligible equivalent- oxide-thickness (EOT) increase of 0.1 Aring (compared to the uncapped reference), and a low Vt instability of 4.8 mV at 7 MV/cm. It also passes the ten-year negative-bias-temperature-instability (NBTI) lifetime specification with a gate overdrive of -0.7 V. This indicates that thin Al2O3obtains caps are beneficial to the pFET applications. In contrast, nitrogen incorporation in the Al2O3-capped HfSiOprop is not favorable because it increases the Vt by 50-140 mV, degrades the mobility by 10%-22%, increases the EOT by 0.5-0.8 Aring and the Vt instability by 5-13 mV, and reduces the NBTI lifetime by four to five orders of magnitude. Compared to postcap nitridation, high-k nitridation results in more severe degradation of these properties by incorporating nitrogen closer to the Si/SiO2 interface.

Thin dysprosium-, scandium-, and hafnium-based oxide dielectric films are deposited by atomic vapor deposition (AVD) using tris(6-ethyl-2,2-dimethyl-3,5-decanedionato) dysprosium [Dy(EDMDD)3], tris(6-ethyl-2,2-dimethyl-3,5-decanedionato) scandium [Sc(EDMDD)3], and bis(tert-butoxide) bis(methoxymethyl propanoxide) hafnium [Hf(OtBu)2(mmp)2] as precursors. Spectroscopic ellipsometry (SE), Rutherford backscattering (RBS) spectrometry, and X-ray photoemission spectroscopy (XPS) demonstrate good control of the thickness and composition of the films. In particular, ternary and quaternary oxide alloys of any desired composition are grown. X-ray diffraction (XRD) shows that the (Dy0.5Sc0.5)2O3 films are amorphous as grown, whereas the (Dy0.5Hf0.5)4O7 and (Sc0.5Hf0.5)4O7 films are crystalline. The crystal structures of DyxHf1–xOy and ScxHf1–xOy change from monoclinic to cubic around x∼0.1.

To increase CMOS device performance, new materials are introduced in the gate stack (high-k dielectrics, metal gates) and the transistor channel (Ge, III-V). In this work, we study the Atomic Layer Deposition (ALD) of hafnium based gate dielectric oxides. Depositing by means of surface controlled reactions implies that the chemical sites at the surface can determine the growth behavior. First, the starting surface effect is analyzed for HfO 2 ALD on Ge and GaAs substrates. Either substrate inhibition or enhancement occurs, both associated with an initial regime of island growth The presence of oxygen enhances the GPC in the first reaction cycle. Second, the steady ALD of ternary oxides (hafnium silicate, aluminate, zirconate) is discussed HfCl4 (and ZrCl4) chemisorption are much less affected by the composition of ternary oxides than by the starting surface. On the other hand, the SiCl4 chemisorption rate is significantly affected by the Hf-content of hafnium silicates. © The Electrochemical Society.

The effect of postdeposition anneals in various ambients on negative bias temperature instability (NBTI) in metal-organic chemical-vapor-deposited HfSiO(N) stacks is investigated. The nitrided stacks, either by anneal or decoupled plasma nitridation (DPN) followed by a postnitridation anneal in O2 or N2 (DPN + O2 and DPN + N2 ), are more degraded by NBTI than the nonnitrided ones (O2, N2 anneal, and as deposited stacks). Moreover, none of the nitrided stacks reaches the 10-year NBTI lifetime, while the lifetime for the nonnitrided ones is larger than 10 years. Nitrogen profiles measured by X-ray photoelectrons spectroscopy and charge-pumping-current data show a relation between nitrogen location and positively charged defects in the gate stack. The additional NBT degradation in nitrided stacks is due to filling or generation of nitrogen-related defects by holes that are injected from the channel.

Monolayer-Si-passivated Ge nFETs with high electron mobility (175 cm2/Vs at Ns=5×1012 cm−2) and superior PBTI reliability (max. Vov = |Vg-Vth| of 0.28V at 125°C) at 0.95-nm-EOT are demonstrated on a 300 mm Si wafer platform. The electron mobility is increased by optimizing the Si thickness while significant improvement in PBTI reliability is realized by band engineering using La-induced interface dipole and defect passivation using laser annealing. This is a significant step forward for the introduction of Ge nFET as high mobility device in advanced technology nodes.

The replacement of poly-silicon by metallic compounds in the gate stack leads to the search of metals with suitable work function. However, it is observed that thermal budget has a large influence on the effective work functions of several metals. In this paper, we investigated the possible modification of the chemical states by physical analysis techniques (XPS, ERD, SIMS) by studying investigating the chemistry of the high-k oxide/metal interface. We show that in the case of the TiN/TaN/HfO2/SiO2/Si stack, several modifications occur upon 1000{degree sign}C N2 annealing: Increase of the nitrogen content of the TaN, interdiffusion of the Ti and TaN, and formation of Ta2O5 at the TaN/HfO2 interface.

Angle resolved XPS (ARXPS) is a powerful tool for the determination of the thickness of ultra-thin films. In the case of high-k dielectric layers, the technique is capable of measuring the thickness of both the high-k layer and intermediate layers of silicon dioxide or metal silicate. The values for layer thickness are in close agreement with those generated by a variety of other techniques. As well as knowing the thickness of these layers, it is important to determine whether the layers are continuous or whether the coverage of the high-k layer is only partial. Using ARXPS, a method has been developed to determine whether the coverage of the high-k material is continuous and, if not, to calculate the fraction of the surface that is covered. The method is described with reference to the layers of Al2O3 grown on SiO2 using atomic layer deposition (ALD). The method is then applied to HfO2 layers produced using ALD on silicon wafers whose surfaces had received three different types of surface treatment. The way in which the layers grow and the nature of the resulting layer were found to depend upon the pre-treatment method. For example, growth on a thermal silicon dioxide surface resulted in complete coverage of HfO2 after fewer ALD cycles than layers grown on an H-terminated surface. The results from ARXPS are compared with those obtained from ToF SIMS that have been shown earlier to be a valuable alternative to the LEIS analysis [1] .

To facilitate selective removal of the gate dielectric towards the gate electrode, wet etch characteristics of HfSiOx and HfSiOx(N) in acidified HF solutions were determined as function of several process parameters. Etch behavior of Hf- silicates was found to be little influenced by the various CVD deposition processes. The top part (0-2 nm) of thick Hf- silicate layers etched similar to as-deposited thin layers (< 2nm) while the bulk part was etching significantly slower. However, etch rates were strongly dependent on composition (lower for Hf-rich silicates). Also, the removal rate of HfSiOx (N) was mainly depending on the amount of incorporated nitrogen and crystallization temperature. Thermally nitrided layers were easier to remove compared to plasma nitrided layers. Post nitridation anneals at high temperature in nitrogen environment decreased the etch rate. After removal, Hf concentrations below 1e11 at/cm2 for most of the HfSiOx(N) layers under study were observed after a short (typically a few seconds) etch process in a single wafer spin cleaning tool.

on the germanium Wafer Surface B. Onsia 2, , T. Conard, S. De Gendt , M. Heyns, I. Hoflijk, P. Mertens, M. Meuris, G. Raskin, S. Sioncke, I. Teerlinck, A. Theuwis J. Van Steenbergen and C. Vinckier 1 Imec, kapeldreef 75, B-3001 Heverlee, Belgium 2 K.U.Leuven, Afd. Fysische en Anal. Chemie, Celestijnenlaan 200F, B-3001 Heverlee, Belgium 3 Umicore, Watertorenstraat 33, B-2250 Olen, Belgium a Bart.Onsia@imec.be

A comparison between atomic layer chemical vapor deposition (ALCVD) and metal organic chemical vapor deposition (MOCVD) HfO2 layers on Ge indicate that ALCVD layers have some improved capacitor characteristics. An NH3 pre-treatment was essential to obtain MOS C–V characteristics for the deposited HfO2 layer. We also report for the first time, deep sub-micron Ge pFETs made in a silicon-like process flow with a directly etched metal gate stack on a HfO2 dielectric. The results indicate that for improving Ge devices, more understanding on the dopant diffusion control and the reduction of interface state density will be necessary.

Crystalline superlattices consisting of alternating periods of Si layers and O-atomic layers are potential new channel materials for scaled CMOS devices. In this letter, we investigate Chemical Vapor Deposition (CVD) for the controlled deposition of O-atoms with O-3 as precursor on Si(100) substrates and Si epitaxy on the O-layer. The O-3 reaction at 50 degrees C on the H-terminated Si results in the formation of Si-OH and/or Si-O-Si-H surface species with monolayer O-content. Defect-free epitaxial growth of Si on an O-layer containing 6.4E+14 O-atoms/cm(2) is achieved from SiH4 at 500 degrees C. (C) 2013 The Electrochemical Society. All rights reserved.

Ultrathin (a few nm) mixed HfO2/Al2O3 oxides deposited by ALCVD on Si substrates were analyzed with low energy (250 eV) Cs- and Xe+ ions by ToF-SIMS in the dual beam mode. The analysis beam was 15 keV Ga+. Several layers were measured, with different metal ratios (Hf:Al) and different number of deposition cycles. We observed a significant enhancement of the Al (and AlOx clusters) signal at the surface along with a Hf (and HfOx clusters) depletion at the film surface. However, the thinnest films were found to contain much more Hf than the thickest ones. Several ion ratios were used (e.g. HfO+/AlO+ or HfO2-/AlO2-) in order to quantify the Hf:Al concentration ratio in the films. We found that these ratios correlate well with each other. with the metal deposition ratio, and with XPS ratios, enabling us to reconstruct the Al and Hf composition variation in the film. (C) 2004 Elsevier B.V. All rights reserved.

Due to its numerous advantages ToF-SIMS profiling has often been used in the analysis of high-k dielectrics. However, profiling high-k gate stacks induces a number of artifacts such as preferential sputtering, tailing of the metal peak in the substrate, interfacial peaks, etc. In this work, we investigated a number of sputtering conditions (Ar, Xe, Ga, energy ranging from 350 eV to 15 keV) in order to determine the most favorable sputtering condition which minimizes these artifacts. The results show that the tail of the Hf in the Si is only marginally dependent on the sputtering conditions suggesting another mechanism than collisional mixing. It also shows that even if the influence on the tail is limited, Xe profiling is far superior to Ar profiling in terms of depth resolution for the rest of the profile. Finally, this work also shows that partially oxidizing sputtering conditions lead to heavily distorted profiles.

In order to increase performance in advanced MOS devices, alternative gate insulators with high electrical permittivity are investigated to replace SiO2. Recent developments include the presence of nitrogen in or around the HfO2 stack. It is thus important to be able to acquire knowledge of the depth distribution of the nitrogen in the layers with enough accuracy. This remains a real challenge for SIMS due to varying matrices in which the nitrogen is distributed. We first present results obtained with Xe and Cs profiling. We determined the “best to use” clusters in order to retrieve the maximum information of the data. In the second part, we investigate some less standard operational mode of SIMS profiling. For instance, it has also long been considered that the detection of MCs+ clusters suffers from less matrix effect and could thus be advantageous for this kind of analysis, where the Cs surface concentration is reduced by the use of Xe–Cs co-sputtering. We also introduce a new method in order to increase the sensitivity to nitrogen by using a “carbon-based” flooding and using the CN− cluster detection.

Measuring HfO 2 /Si stacks by secondary ion mass spectroscopy (SIMS) has become a common task in the semiconductor industry. However, when analyzing these stacks with an oxygen beam, a strong impact of the experimental conditions on the Hf + signal as well on the Si signal can be observed. In order to understand these effects, we investigated the effect of oxygen on the depth profiling of these stacks using an Atomika 4500. In this paper, the ionization probability of Hf sputtered from a HfO 2 /Si stack as well a Hf implantation in Si is measured for different beam incidence angles and energies. It is shown that basically two physical mechanisms are responsible for the Hf signal intensities. The first part of the signal can be correlated with the impact of oxygen on the Hf ionization degree, in line with the classical bond-breaking theory. The second mechanism is more difficult to define, but appears linked to the emission of Hf into a different (neutral, molecules?) emission channel, thereby reducing the available Hf for detection as Hf + . Finally, a very strong influence of Hf on the Si and Si-cluster ions is reported.

Using Cs- in the TOF-SIMS dual beam mode offers a semi-quantitative solution to depth profiling. Specifically, the use of these alkali ions strongly increases negative ion yields, decreases the positive ones and allows the formation of MCs+ and MCs2+ clusters. Recently. Niehuis and Grehl [Proceedings SIMS XII (2000) 49] developed a new approach consisting of co-sputtering Xe and Cs in order to control the Cs surface concentration, thus allowing the optimization of elemental and cluster ion yields. We applied that technique on different well-defined samples (e.g. Si, SiO, and Al2O3) and we monitored positive ions (e.g. Si+, Al-, CsSi+, CsAl+, CsO+, Cs2O+, Cs2Si+, etc.) as a function of the sputtering beam Cs concentration. First, we observed the decrease of the elemental ions due to the work function lowering, as is predicted by the tunneling model. We then studied the behavior of the MCs+ and the MCs2+ clusters. The MCs+ yield exhibits a maximum at a given Cs/Xe beam concentration ratio, depending on the studied element M and also on its chemical environment (e.g. Si and SiO2), and on the energy of the Cs beam. In other words, it is hypothesized that this yield maximum is a consequence of the competition between the varying surface Cs coverage (direct concentration effect) and the decreasing ionization probability due to that varying Cs [Phys. Rev. Lett. 50 (1983) 127; Phys. Rev. B 29 (1984) 2311; K. Wittmaack, Proceedings SIMS VHI, (1992) 91]. Simple models based on the tunneling model were applied to interpret our results. The MCs2+ signal behaves in a very different way. As shown by Gao [Y. Gao, Y Marie, F. Saldi, H.N. Migeon, Proc. SIMS IX, (1994) 382], these clusters are predominant for electronegative elements and increase in a monotonous way with Cs beam concentration. (C) 2004, Elsevier B.V. All rights reserved.

The angular dependence of the Ge sputter yield is reported for primary beam energies between 270 and 3 keV. For energies above 1 keV no full oxidation occurs, whereas in the sub-keV energy range, full oxidation of the Ge is possible. The oxidation state and the ionization probability change very abruptly as function of the incidence angle. The length of the transient is angle independent at 3 keV, while there is a clear angular dependence of the transient for a primary beam of 500 eV O2.

Measuring HfO 2 /Si stacks-by secondary ion mass spectroscopy (SIMS) has become a common task in the semiconductor industry. Although the reliability of the SIMS-profiles from multilayer structures can be influenced by sputter yield and ionization yield variations in the interface region, the part of the dopant profile located beyond the interface can normally be obtained with excellent SIMS-characteristics. By comparing the SIMS-profiles from B-profiles in Si, measured with and without a HfO 2 -cap layer, it becomes clear that the high k film has a strong impact on the resulting dopant profiles. With the high k film present, a significant distortion of the depth and intensity scale can be observed and the B-profile (which is, in principle, fully contained in the Si) appears almost twice as deep when profiling through the HfO 2 -layer as compared to the uncapped sample. Normalizing the depth and concentration scale with the variations of the SiO-signals, seems to lead to an acceptable B-profile. The distortion results from a strong reduction in sputter yield due to the presence of (even small) amounts of Hf. Apparently, Hf segregates towards the surface forming a (fractional) layer, which shields the Si-atoms from sputtering. The sputter yield of this Hf-layer on the other hand is very low leading to a drastic reduction in average erosion rate. For conditions where normally no full oxidation is obtained (high energy, non-normal incidence beams on Si and Ge-substrates), this reduction leads to a temporary enhancement of the oxygen incorporation and the ionization probability.

As SiGe becomes a building block of advanced devices, depth profiling of SiGe gains in importance, requiring an understanding of its basic behavior under oxygen bombardment. In this study, the sputter yield and ionization probability of Si and Ge sputtered from SiGe-substrates are studied as a function of the incidence angle. The altered layer formation and the element redistribution are studied with in situ sputter/RBS and the oxidation of the bombarded SiGe surface is analyzed with XPS. The results show that the altered layer formation in the SiGe system is much more complex than in the Si case and strongly dependent of the incident angle/primary energy. In addition to sputter related effects, thermodynamics and volatility of the Ge-oxide are important mechanisms.

This study is dedicated to a better understanding of the processes occurring under ion bombardment of ultra-thin ZrO2/SiO2/Si gate dielectric stacks. Complex-shaped depth profiles were obtained by using TOF-SIMS with dual beam (500 eV for sputtering and 10 keV for analysis) Ar+ ions. The SIMS intensities of all the elements depend critically on the amount of oxygen at any moment of the sputtering process. Increased intensity is observed at the surface and at the ZrO2/SiO2 interface. A long tail of the Zr signal is present in the Si substrate, even after the second (SiO2/Si) interface, and a double bump structure in the Zr-90 and ZrO dimer is observed, which is more pronounced with increasing thickness of the interfacial SiO2 layer. Computer simulations using the dynamic Monte Carlo code (TRIDYN) are performed in order to distinguish the ion bombardment-induced effects from changes in the ionization degree. The original code is extended with simple models for the ionization mechanism and for the molecular yield during sputtering. Oxygen preferential sputtering at the surface and ballistic transport of Zr towards and through the interface are clearly demonstrated, but there is also evidence that due to recoil implantation oxygen gets piled-up near the ZrO2/SiO2 interface. (C) 2004 Elsevier B.V. All rights reserved.