Bulletin of the American Physical Society
2005 APS March Meeting
Monday–Friday, March 21–25, 2005; Los Angeles, CA
Session A18: Focus Session: Semiconductor Characterization |
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Sponsoring Units: FIAP GIMS Chair: David Seiler, NIST Room: LACC 406A |
Monday, March 21, 2005 8:00AM - 8:36AM |
A18.00001: Interface Sensitive Measurement of High k - silicon dioxide – silicon system using Optical Second Harmonic Generation Invited Speaker: The properties of the interface layer play a key role in the properties of transistor gate dielectric stacks. This has resulted in a renewed emphasis being placed on physical interfacial characterization. Electrical measurements such as capacitance -- voltage have always been sensitive to the number of interface trapping states. The sub 5 nm thickness of high $\kappa $ - silicon dioxide films on silicon challenges all characterization methods. Traditional characterization methods such as scanning transmission electron microscopy have seen rapid advances in capability as the first aberration corrected microscopes become available. Pennycook recently observed single Hf atoms in the silicon dioxide interfacial layer.(1) Less widely used methods also show considerable promise. Optical second harmonic generation has been used to measure interfacial states in the silicon dioxide -- silicon interface.(2) In this paper, we discuss our first SHG measurements of the High $\kappa $ - silicon dioxide -- silicon system. Comparisons between the responses of Hf O$_{2}$ and HfO$_{x}$Si$_{y }$before and after annealing show the effect of silicate decomposition after annealing. Time dependent optical SHG is believed to be sensitive to trap density, and we again show our first results. When possible, we compare SHG to electrical measurements. [Preview Abstract] |
Monday, March 21, 2005 8:36AM - 8:48AM |
A18.00002: Measurement of the Full State of Stress of Silicon with Micro-Raman Spectroscopy Stephen Harris, Ann O'Neill, Wen Yang, Peter Gustafson, James Boileau, W.H. Weber, Bhaskar Majumdar, Somnath Ghosh Micro-Raman spectroscopy has been widely used to measure local stresses in silicon and other cubic materials. However, a single (scalar) line position measurement cannot determine the complete stress state unless it is has a very simple form, such as uniaxial. Previously published micro-Raman strategies designed to determine additional elements of the stress tensor take advantage of the polarization and intensity of the Raman scattered light, but these strategies have not been validated experimentally. In this work we test one such stategy [S. Narayanan, S. Kalidindi, and L. Schadler, \textit{JAP}. \textbf{82}, 2595 (1997)] for rectangular (110)- and (111)-orientated silicon wafers. The wafers are subjected to a bending stress, and the state of (plane) stress is modeled with ABAQUS. The Raman shifts, intensities, and polarizations are calculated using previously published values for silicon phonon deformation potentials. The experimentally measured values for $\sigma _{xx}$, $\sigma _{yy}$, and $\tau _{xy}$ at the silicon surface are in good agreement with those calculated with the ABAQUS model. [Preview Abstract] |
Monday, March 21, 2005 8:48AM - 9:00AM |
A18.00003: UV-Raman deformation coefficients in Si and SiGe alloys Michael Canonico, Ran Liu As Si CMOS device scaling issues become increasingly challenging a number of alternatives arise including Si-On-Insulator (SOI) substrates, high-k gate dielectrics, and Strained Si Channel (SSC) devices.~ In the case of SSC structures, the enhancement in electron mobility depends directly on the stress magnitude.~ Raman scattering, particularly in the UV due to short penetration depth, has proven well suited for measuring thin SSC layer stress.~ The technique depends critically on the value taken for the strain shift coefficient ($b)$, which correlates the shift in the phonon frequency with the strain.~ A number of values have been reported in the literature to date using NIR and visible excitation; however, the authors are unaware of previous work performed specifically in the UV. In this work, we have used a combination of HRXRD reciprocal space mapping (RSM) to measure the in-plane strain of high quality Si/SiGe heterostructures and UV-Raman with the 325nm He-Cd line to determine the Si LO phonon deformation coefficient in Si and SiGe alloys with compositions ranging from 10-40{\%} Ge. [Preview Abstract] |
Monday, March 21, 2005 9:00AM - 9:12AM |
A18.00004: In-situ photovoltage shift measurements of hafnium oxides and silicates grown on Si(100) using femtosecond photoelectron spectroscopy Daeyoung Lim, Richard Haight Femtosecond laser based photoelectron spectroscopy was used as an in-situ monitor of band bending in Si (100) substrates during various stages of hafnium oxide growth and post-deposition anneal. A fraction of the 800 nm laser pulse is directed onto the sample as a pump pulse, which flattens the existing band bending in the Si substrate. The remaining 800 nm light is focused into bursts of Ar gas to generate high order, odd multiple harmonics used as an in-situ probe of band bending. Photovoltage measurements reveal an abrupt onset of charging during the annealing of hafnium oxides and silicates, deposited on thin SiON interlayer oxides grown on lightly doped Si (100) substrates. Core level photoemission and transmission electron microscopy were used to correlate the observed charge injection at elevated temperatures with structural and chemical changes in the SiON and HfO$_{2 }$dielectric layers. [Preview Abstract] |
Monday, March 21, 2005 9:12AM - 9:24AM |
A18.00005: An infrared probe of tunable dielectrics in metal-oxide-semiconductor structures Kevin Mikolaitis, Zhiqiang Li, Guangming Wang, Alan Heeger, Dimitri Basov We present a novel approach to investigate electric-field- induced changes of the dielectric function of the gate insulator in metal-oxide- semiconductor (MOS) structures using infrared spectroscopy. This approach is enabled by an innovative design of the electrodes. We investigated structures based on TiO$_{2}$ dielectric insulator on doped silicon commonly used in (organic) FET devices. We show that the voltage-induced changes of dielectric constant of TiO$_{2}$ originate from a radical modification of lattice vibration modes of this compound induced by applied electric field. Novel characterization capabilities demonstrated in our work uncover the unique potential of infrared spectroscopy for the analysis of tunable insulators and also for the examination of charge injection phenomena in semiconductors. [Preview Abstract] |
Monday, March 21, 2005 9:24AM - 9:36AM |
A18.00006: High Resolution 2D Dopant Profiling of FinFET Structures using Scanning Probe Microscopy Alexander Khajetoorians, Jianlong Li, Li Shi, Xiang-Dong Wang, Chih-Kang Shih The ability to perform dopant/junction profiling with high spatial resolution is critical for development of future generation devices such as FinFET structures. Among various forms of scanning probe microscopy, scanning tunneling microscopy (STM) has demonstrated direct atomic imaging of dopant atoms on GaAs (110) surfaces. More recently, scanning thermoelectric microscopy (SThEM) (H.K. Lyeo, et al \textit{Science }v.303 p816 (2004)) has been applied to profile GaAs $p-n$ junction with unprecedented spatial resolution. The key challenge to successfully apply these techniques to silicon based devices is to prepare a surface that is both chemically and electronically passivated. Here we present our progress toward this goal. In particular we will report STM and SThEM studies on silicon based electronic devices including FinFET structures. Moreover, we will present comparative studies of dopant/junction profiling using STM, SThEM, and scanning capacitance microscopy (SCM). [Preview Abstract] |
Monday, March 21, 2005 9:36AM - 9:48AM |
A18.00007: High-Resolution Microcalorimeters for X-ray Microanalysis B.L. Zink, G.C. Hilton, J.N. Ullom, K.D. Irwin Microcalorimeters represent the current state-of-the-art in x- ray detection for high-resolution microanalysis. In this device the energy of x-rays emitted from regions of a sample or circuit excited by an electron beam is determined by measuring the increase in temperature caused by the absorption of an x-ray in the microcalorimeter, normally held at temperatures well below $1$ $K$ by a compact adiabatic demagnetization refrigerator. The performance of these detectors is ultimately determined by the sensitivity and noise characteristics of the thermometer. The best performance is currently achieved using superconducting transition-edge sensors which can resolve energy differences of better than 1 part in 2000. In this talk I will briefly summarize the current state of x-ray microcalorimetry and discuss recent efforts at NIST to develop next-generation microcalorimeters using SQUID-based magnetization thermometry. [Preview Abstract] |
Monday, March 21, 2005 9:48AM - 10:00AM |
A18.00008: High-resolution characterization of advanced interconnect and packaging architectures Shriram Ramanathan, Evan Pickett, Patrick Morrow, Yongmei Liu, Rajen Dias Characterization of buried interfaces in advanced interconnect and packaging structures is a critical challenge as CMOS devices are scaled and as novel packaging concepts such as through-silicon vias are developed. It is important to be able to image chip-to-package attach bumps with high resolution as well as individual interconnect layers in a processed device. Critical information that needs to be obtained from such inspection includes detection of un-bonded bumps, missing interconnections in stacked die and delaminations in underlying layers. In this paper, we discuss and benchmark different characterization techniques to analyze and quantify the quality of buried interfaces with detailed experimental and theoretical analyses. Acoustic microscopy is used to investigate interfaces between stacked die at high resolution. We present theoretical analysis which shows the effect of aberrations on image formation and the corresponding resolution degradation. Infra-red imaging through the substrate and pulsed thermal microscopy in transient mode were also used to investigate the quality of stacked die interfaces. We critically review these different techniques for inspection of buried interfaces and discuss roadmap for metrology needs. [Preview Abstract] |
Monday, March 21, 2005 10:00AM - 10:12AM |
A18.00009: Direct Imaging of Minority Carrier Drift in Luminescent Materials David Luber, Nancy Haegel A technique is presented to directly image charge carrier drift and diffusion in semiconductor samples over a temperature range from 300 to 10 K. A scanning electron microscope produces electron-hole pairs at a point and an applied voltage bias causes the charge carriers to drift. Upon radiative recombination, a photon is emitted at the point of generation, which is then collected and imaged by a cooled CCD camera via an optical microscope. This technique allows for the preservation of spatial information from the carrier recombination. Current resolution is $\sim $ 0.4 $\mu $m per pixel. Results will be presented from the imaging of drift behavior in high purity epitaxial GaAs as a function of temperature. Minority carrier drift over distances in excess of 100 $\mu $m at a field of $\sim $ 80 V/mm has been directly imaged using this technique for high purity room temperature n-type GaAs samples with net doping of $\sim $ 5 x 10$^{13}$ cm$^{-3} $. The characterization of the drift tails as a function of temperature will be presented and the measured spatial homogeneity of the sample depicted. The effect of near-contact electric fields due to space charge on charge carrier injection and collection at low temperature will be presented. [Preview Abstract] |
Monday, March 21, 2005 10:12AM - 10:24AM |
A18.00010: Contact-free approach for the determination of minority carrier diffusion length F.M. Bradley, Will Freeman, Nancy M. Haegel Direct imaging of electron/hole recombination via an optical microscope and a high sensitivity charge coupled device coupled to a scanning electron microscope captures spatial information about the transport behavior in luminescent solid state materials. Carriers are generated by the electron beam, and an image of the recombination provides highly localized information on carrier diffusion and/or drift. Unlike conventional cathodoluminesence, the e-beam is not scanned. Recent work has demonstrated the feasibility and limitations of the technique. Comparisons will be made of luminescent images in 3D (bulk) and 2D (quantum well) limits. In the 3D case, the excitation volume plays a key role, while in 2D, beam size and carrier diffusion determine the luminescent spot size. The technique provides the potential for extraction of minority carrier diffusion length without the use of contacts. It allows for easy localization of the measurement site, broad application to a range of materials and potential industrial automation. This technique is of special interest for devices such as solar cells, where minority carrier lifetime is a key performance parameter. [Preview Abstract] |
Monday, March 21, 2005 10:24AM - 10:36AM |
A18.00011: Structural and morphological characterization of GaN(0001) layers grown on SiC by maskless pendeo-epitaxy via X-ray Microdiffraction R.I. Barabash, G.E. Ice, S. Einfeldt, D. Hommel, A.M. Roskovski, R.F. Davis Novel white beam X-ray microdiffraction (WBD) together with high resolution monochromatic X-ray diffraction (HRXRD) and finite element simulations have been used to determine the distribution of strain, dislocations, sub-boundaries and crystallographic wing tilt in uncoalesced and coalesced GaN layers grown by maskless pendeo-epitaxy. In traditional HRXRD the spot size of the X-ray beam is large ($\sim $0.5 mm), i.e. it gives information averaged over 40-50 of stripes. In contrast, advanced WBD provides very local information and enables us to follow the local orientation at different locations across the stripe. Stress relaxation in the GaN layers occurs in conventional and in pendeo-epitaxial films via the formation of additional misfit dislocations, domain boundaries, elastic strain and wing tilt. An important parameter was the width-to-height ratio of the etched columns of GaN from which the lateral growth of the wings occurred. The strain and tilt across the stripes increased with the width-to-height ratio. Sharp tilt boundaries were observed at the interfaces formed by the coalescence of two laterally growing wings. The wings tilted upward during cooling to room temperature for both the uncoalesced and the coalesced GaN layers [Preview Abstract] |
Monday, March 21, 2005 10:36AM - 10:48AM |
A18.00012: UHV Nanoworkbench and the `Roaming' Field Effect Transistor Olivier Guise, John T. Yates, Jr., Joachim Ahner, Jeremy Levy A multiple-tip ultra-high vacuum (UHV) scanning tunneling microscope combined with a scanning electron microscope (SEM) and molecular-beam epitaxy growth capabilities has been developed. This instrument (Nanoworkbench - NWB) is used to perform four-point probe conductivity measurements at sub-micrometer spatial dimension. The system is composed of four chambers, the multiple-tip STM/SEM chamber, a surface analysis and preparation chamber equipped with standard surface science tools, a molecular-beam epitaxy chamber and a load-lock chamber. The four chambers are interconnected by a unique transfer system based on a sample box with integrated heating and temperature-measuring capabilities. We demonstrate the operation and the performance of the NWB with four-point- probe conductivity measurements on a silicon-on-insulator (SOI) crystal. The creation of a `roaming' Field-Effect Transistor, whose dimension and localization are respectively determined by the spacing between the four probes and their position on the SOI surface, is demonstrated. The NWB has a potential to look at nanostructures developed in situ using the MBE chamber, such as Ge quantum dots for example. This work was supported by DARPA QuIST through ARO contract number DAAD-19-01-1-0650. [Preview Abstract] |
Monday, March 21, 2005 10:48AM - 11:00AM |
A18.00013: An investigation of dopping profile for a one dimensional heterostructure ZhaoHui Huang, Dragan Stojkovic, Paul Lammert, Vincent Crespi A one-dimensional junction is formed by joining two silicon nanowires whose surfaces are terminated with capping groups of different electronegativity and polarizability. If this heterostructure is doped (with e.g. phosphorous) on the side with the higher bandgap, the system becomes a modulation doped heterostructure with novel one-dimensional electrostatics. We use density functional theory calculations in the pseudopotential approximation, plus empirical model calculations, to investigate doping profiles in this new class of nanostructures. [Preview Abstract] |
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