B. Hollander

Forschungszentrum Jülich, Jülich, North Rhine-Westphalia, Germany

Are you B. Hollander?

Claim your profile

Publications (24)29.29 Total impact

  • Source
    11/2014;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Compressively strained SiGe has been used in nanometer devices, for example, as high mobility channel [1] in MOSFET and low-bandgap source in tunnel field effect transistor to increase the tunneling probability [2] . For nanometer devices, source/drain contact resistance is becoming comparable or larger than intrinsic channel resistance [3] . Ni germanosilicide is one promising option for SiGe contacts. However, synthesis of homogeneous germanosilicide is challenging due to agglomeration and Ge segregation. Ni(Al)SiGe epitaxy growth by incorporation of Al mediation layer on a relaxed SiGe substrate has been reported [4] . In this paper we present results on the formation of very homogeneous Ni(Al)SiGe with sharp germanosilicide/SiGe interfaces on strained SiGe, which has potential for various device applications. 3 cycles of {Ni/Al} layers with different Al concentration were deposited on strained SiGe substrate and rapid thermal processing was followed to form germanosilicides. Transmission electron microscopy(TEM) results shown in Figures 1 and 2 indicate that the most uniform germanosilicide layer with a sharp interface to the SiGe layer was formed with 20% Al at 400°C. Corresponding RBS/channeling results presented in Figure 3 further confirm that the layer formed at 400°C with 20% Al shows better crystalline quality indicated by the lower channeling yields. The Al content modulates the Ni diffusion, thus resulting in different germanosilicide morphology.The Al mediation effect is temperature dependent, as shown in TEM results (Figure 2) for samples with 20% Al. Higher Ni diffusivity at higher temperature is attributed to be the main reason. The competition between Ni diffusivity and Al barrier effect leads to different stoichiometry (Figure 4). Al mediation effect can also be seen intuitively in secondary ion mass spectrometry (SIMS) results of samples formed with 10% and 20% Al at 400 ºC (Figure 4): Ni and Al distribute homogeneously in germanosilicide layer while it is different for the sample with 10% Al. With high resolution TEM and the electron diffraction pattern (Figure 5) the germanosilicide phase formed at 400°C with 20% Al is identified as B8 type Ni 5 (SiGe) 3 . References: [1]
    Materials for Advanced Metallization, Chemnitz; 03/2014
  • [Show abstract] [Hide abstract]
    ABSTRACT: Within the last years, III-nitride-based devices have been demonstrated with exceptional performance. There is, however, a severe lack of knowledge when it comes fabrication of p-channel devices. p-Channel heterostructure field-effect transistors (HFETs) could open the way for nitride-based complementary logic. Here, a comprehensive study of enhancement and depletion mode p-channel GaN/AlInGaN HFETs is performed. The influence of a highly p-doped GaN cap layer on device performance is investigated. Gate recessing and changes in composition of the backbarrier are analyzed. ON/OFF ratios of up to 108 and subthreshold swings of about 75 mV/decade are achieved.
    IEEE Transactions on Electron Devices 01/2013; 60(10):3005-3011. · 2.06 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A new approach for the heterostructure design following the idea to reduce the interface charge itself by applying a quaternary barrier layer with rather low polarization is demonstrated. The enhancement mode (e-mode) heterostructure field effect transistors (HFET) is consist of a GaN buffer and a quarternary barrier layers, whose composition and thickness are chosen carefully to result in an e-mode device. The devices is passivated with 120 nm SiN by plasma enhanced CVD. An increase in gate and drain leakage can be observed and finds its origin in surface or interface conductivity of the not fully optimized SiN. Nevertheless, for all devices the extrinsic transconductance has increased due to further carrier concentration enhancement in the access region by the passivation, and the best performance is achieved with maximum extrinsic transconductance of 260 mS/mm, which is among the highest reported for a 1 11m gate length e-mode HFET.
    Device Research Conference (DRC), 2012 70th Annual; 01/2012
  • [Show abstract] [Hide abstract]
    ABSTRACT: A lattice-matched InAlGaN/GaN heterostructure with a barrier-layer thickness of 4 nm has been grown and passivated in situ with a 63-nm SiN by metal–organic chemical vapor deposition. Enhancement-mode heterostructure field-effect transistors have been realized by a fluorine-based surface treatment after the local removal of the SiN. The threshold voltage and transconductance were 0.65 V and 250 mS/mm, respectively, for a 1-$\mu\hbox{m}$ gate-length device. The benefits of an in situ SiN passivation are demonstrated: first, the stabilization of the barrier material and prevention from oxidation and second, the improvement of the device characteristics by reduced source resistance and reduced trapping effects.
    IEEE Electron Device Letters 01/2012; 33(4):519-521. · 2.79 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Epitaxial growth of Ni germanosilicide on relaxed SiGe (30% Ge content) substrate has been achieved by using 3 nm Al interlayer. This epitaxial layer shows a very good uniformity and smooth interface and surface. The epitaxial layer and the SiGe substrate match very well and no misfit dislocation is found at the interface.
    01/2012;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this study, the authors present results on the structural, chemical, and electrical characterization of HfO2 thin layers on 300 mm Si wafers. The layers were prepared by atomic layer deposition using a liquid delivery system technology for metal organic precursors, which allows an accurate control of the Hf precursor. After optimization of the deposition process with an alkylamide precursor for Hf and ozone chemistry, the growth of the SiOx interfacial layer between the HfO2 layer and the Si substrate could be minimized using TiN as metal gate. In addition, the authors studied the effect of Al2O3 interfacial layers on the properties of metal-oxide-semiconductor capacitor resulting in a positive flat band voltage shift of up to ∼300 mV according to the layer thickness. Gate stacks with equivalent oxide thicknesses around 1.1 nm showed leakage current densities as low as 1.1×10-2 A/cm2 at VFB of 1 V. In addition, the capacitance-voltage curves for thin HfO2 layers indicated a negligible hysteresis, below 10 mV, after a forming gas anneal when TiN was used as metal gate.
    Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 01/2011; 29(1):01A301-01A301-4. · 1.36 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this work, we address the effect of C+ ion implantation on the formation of nickel-germanosilicide NiSi0.8Ge0.2 on relaxed Si0.8Ge0.2 layers. The layer morphology and sheet resistance are investigated as a function of the C+ implantation dose and annealing temperature. The presence of C atoms increases the NiSiGe thermal stability by about 200°C. We demonstrate that the carbon atoms retard the growth of germanosilicide layers, stabilize the NiSiGe phase and, due to C segregation at grain boundaries and interface during annealing, smooth the Ni Si0.8Ge0.2/Si0.8Ge0.2 interface.
    Interconnect Technology Conference and 2011 Materials for Advanced Metallization (IITC/MAM), 2011 IEEE International; 01/2011
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A powerful method for analyzing general strain states in layer systems is the measurement of changes in the ion channeling directions. We present a systematic derivation and compilation of the required relations between the strain induced angle changes and the components of the strain tensor for general crystalline layer systems of reduced symmetry compared to the basic (cubic) crystal. It is shown that, for the evaluation of channeling measurements, virtually all layers of interest may be described as being “pseudo-orthorhombic.” The commonly assumed boundary conditions and the effects of surface misorientations on them are discussed. Asymmetric strain relaxation in layers of reduced symmetry is attributed to a restriction in the slip system of the dislocations inducing it. The results are applied to {110}SiGe/Si layer systems.
    Journal of Applied Physics 07/2010; 107(12):124906. · 2.21 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A mechanism of strain relief of pseudomorphic Si <sub>1-x</sub> Ge <sub>x</sub>/ Si (100) heterostructures by Si <sup>+</sup> ion implantation and annealing is proposed and analytically modeled. The degree of strain relaxation is presented as a function of Ge content and implantation and annealing parameters. Rutherford backscattering spectrometry/channeling, Raman spectroscopy, and transmission electron microscopy are employed to quantify the efficiency of the relaxation process and to examine the quality of the samples, respectively. The mechanism and the conditions for strain relaxation are discussed in terms of dislocation loop formation in the implanted range with emphasis on loop formation in the compressively strained SiGe layer. The detrimental effect of local amorphization of the SiGe layer on its relaxation and on strain transfer to the Si-cap layer is also addressed.
    Journal of Applied Physics 06/2009; 105(11):114905 - 114905-10. · 2.21 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Samarium scandate thin films deposited on (100) Si have been investigated structurally and electrically. Rutherford backscattering spectrometry and transmission electron microscopy results show that the films are stoichiometric, amorphous, and smooth. X-ray diffraction analysis indicates that SmScO <sub>3</sub> starts to crystallize at 900 ° C . Capacitance and leakage current measurements reveal C-V curves with negligible hysteresis, a dielectric constant around 29 for 6 nm thick films, low leakage current densities in the range of 10<sup>-7</sup> A / cm <sup>2</sup> , an effective oxide charge density of ∼5×10<sup>11</sup> cm <sup>-2</sup> , and an interface trap density of 4.5×10<sup>11</sup> ( eV   cm <sup>2</sup>)<sup>-1</sup> .
    Applied Physics Letters 09/2008; · 3.52 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: As scaling of the critical transistor dimensions below 65 nm has been slowed down, the implementation of novel materials, especially high mobility channel materials is most attractive to boost the transistor performance. Applying strain to silicon has become a successful route. The electron mobility can be enhanced by biaxial strain introduced into Si by epitaxial growth of Si on a strain relaxed SiGe layer or by so called process induced methods applied directly on transistor level. The combination of strained Si and SOI is particularly promising due to the combination of the enhanced mobilities and the inherent advantages of SOI. First long channel n-MOSFETs with gate lengths of 5 to 50 mum and a 6.6 nm thick SiO<sub>2</sub> gate dielectric were fabricated. For comparison, devices on unstrained SOI were made. The transfer characteristics of a fully depleted sSOI-MOSFET with a gate length of 5 mum and a gate width of 20 mum indicating an inverse sub-threshold slope of 75mV/dec.
    Semiconductor Device Research Symposium, 2007 International; 01/2008
  • [Show abstract] [Hide abstract]
    ABSTRACT: We present an investigation of a series of samples with strained stripe-patterned SiGe layers grown on a Si substrate. The strain in the SiGe striped epilayers was calculated after measuring the lattice constants of the layers using an x-ray diffraction technique. It was found that the stripes showed an anisotropic strain in the two in-plane directions resulting from the lattice mismatch and the difference in the dimensions of the stripes. The idea is based on the concept of enhancing the hole mobility in subsequent Si cap layers due to anisotropy of the stain in the patterned SiGe layers.
    Semiconductor Science and Technology 03/2007; 22:S212–S215. · 1.92 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Strain relaxation in patterned Si <sub>0.77</sub> Ge <sub>0.23</sub> stripes grown on Si(001) by chemical vapour deposition was investigated after He <sup>+</sup> ion implantation and annealing. Ion channeling measurements indicate asymmetric strain relaxation with a significantly higher residual strain parallel to the stripes than perpendicular to the stripes. These results are confirmed by plan view transmission electron microscopy showing a much higher density of misfit dislocations running along the stripes than across the stripes. Estimates based on a piezoresistivity model indicate significant enhancements of electron and hole mobilities for asymmetrically strained Si cap layers on such SiGe stripes.
    Applied Physics Letters 02/2007; 90(3):032108 - 032108-3. · 3.52 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We investigate the strain state in patterned SiGe lines of various widths after strain relaxation by He ion implantation and annealing (Hollander et al, 2001). We expected that the relaxation in such patterned virtual substrates must be more pronounced in one direction of the stripe than the other, thereby opening a possibility for further enhancement of hole mobility. We employed high-resolution X-ray diffraction to study the relaxation of strain and to assess the structural quality of a series of SiGe striped samples with varying stripe widths from 0.82 to 100 mum, patterned in [110] direction on a (100) substrate. We see that the strain in the stripes in the two orthogonal directions is different i.e. the crystal structure of the stripes is orthorhombic
    3rd International SiGe Technology and Device Meeting (ISTDM 2006); 05/2006
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The strain relaxation of pseudomorphic Si <sub>1-x</sub> Ge <sub>x</sub> layers (x=0.21,…,0.33) was investigated after low-dose Si <sup>+</sup> ion implantation and annealing. The layers were grown by molecular-beam epitaxy or chemical vapor deposition on Si (100) or silicon-on-insulator. Strain relaxation of up to 75% of the initial strain was observed at temperatures as low as 850 ° C after implantation of Si ions with doses below 2×10<sup>14</sup> cm <sup>-2</sup> . We suggest that the Si implantation generates primarily dislocation loops in the SiGe layer and in the underlying Si which convert to strain relaxing misfit segments. The obtained results are comparable to strain relaxation achieved after He <sup>+</sup> implantation with doses of 1–2×10<sup>16</sup> cm <sup>-2</sup> .
    Journal of Applied Physics 09/2004; 96(3):1745 - 1747. · 2.21 Impact Factor
  • Materials Research Society Symposium Proceedings; 04/2004
  • [Show abstract] [Hide abstract]
    ABSTRACT: We report an investigation on self heating effects on SiGe based HFET for the first time. Si/SiGe n-HFETs exhibit excellent high frequency performance with f<sub>T</sub> of 90 GHz (105 GHz), f<sub>MAX</sub> of 188 GHz (225 GHz) at 300 K (50 K), low noise figure NF<sub>MIN</sub> of 0.3 dB at 2.5GHz at 300 K. These figures of merit reflect the superior transport properties of the SiGe based heterosystem as compared with bulk Si devices. However some detrimental effects such as parasitic resistances or electrostatic parasitic capacitances as well as self heating effects can mask their strained enhanced intrinsic transport properties. In this communication the last point is addressed through experimental data and 2-D numeric simulations results. Self-heating influence on device performance is pointed out and alternatives to overwhelm them are presented in terms of a device performance comparison between SiGe HFETs prepared on thin and thick virtual substrates (VS).
    Semiconductor Device Research Symposium, 2003 International; 01/2004
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this work, MODFET layer stacks with a Ge fraction x=33% were grown by molecular beam epitaxy on thin virtual substrate (VS). A method has been developed to produce thin SRB (strain relieved buffer) SiGe layers (100-200 nm) using He implantation and subsequent annealing (750-900 °C) to relax the strain of a pseudomorphic SiGe layer. The degree of relaxation was measured by high resolution X-ray diffraction. To assess the impact of self-heating, the output characteristics were recorded with an ACCENT Diva D225 system in the static and in the pulsed mode with 200 ns pulses at a duty cycle of 1:1000. The difference in the I/V curve between the static and the pulsed mode is much larger for the thick VS indicating enhanced self-heating. Finally, RF measurements up to 50 GHz were carried out on the two VS versions.
    Semiconductor Device Research Symposium, 2003 International; 01/2004
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Si/SiGe n-type modulation-doped field-effect transistors grown on a very thin strain-relieved Si/sub 0.69/Ge/sub 0.31/ buffer on top of a Si(100) substrate were fabricated and characterized. This novel type of virtual substrate has been created by means of a high dose He ion implantation localized beneath a 95-nm-thick pseudomorphic SiGe layer on Si followed by a strain relaxing annealing step at 850/spl deg/C. The layers were grown by molecular beam epitaxy. Electron mobilities of 1415 cm/sup 2//Vs and 5270 cm/sup 2//Vs were measured at room temperature and 77 K, respectively, at a sheet carrier density of about 3/spl times/10/sup 12//cm/sup 2/. The fabricated transistors with Pt-Schottky gates showed good dc characteristics with a drain current of 330 mA/mm and a transconductance of 200 mS/mm. Cutoff frequencies of f/sub t/=49 GHz and f/sub max/=95 GHz at 100 nm gate length were obtained which are quite close to the figures of merit of a control sample grown on a conventional, thick Si/sub 0.7/Ge/sub 0.3/ buffer.
    IEEE Electron Device Letters 09/2002; · 2.79 Impact Factor