S.J. Krause

Arizona State University, Phoenix, Arizona, United States

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Publications (51)33.74 Total impact

  • S.J. Krause · S.R. Wilson · W.M. Paulson · R.B. Gregory

    No preview · Article · Jan 2011 · MRS Online Proceeding Library

  • No preview · Article · Jan 2011 · MRS Online Proceeding Library
  • W. J. Varhue · S. Krause · J. Dea · C. O. Jung

    No preview · Article · Jan 2011 · MRS Online Proceeding Library

  • No preview · Article · Jan 2011 · MRS Online Proceeding Library
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    ABSTRACT: Oxygen has been implanted into Si wafers at high doses and elevated temperatures to form a buried SiO2 layer for use in silicon-on-insulator (SOI) structures. Substrate heater temperatures have been varied (300, 400, 450 and 500°C) to determine the effect on the structure of the superficial Si layer through a processing cycle of implantation, annealing, and epitaxial growth. Transmission electron microscopy was used to characterize the structure of the superficial layer. The structure of the samples was examined after implantation, after annealing at 1150°C for 3 hours, and after growth of the epitaxial Si layer. There was a marked effect on the structure of the superficial Si layer due to varying substrate heater temperature during implantation. The single crystal structure of the superficial Si layer was preserved at all implantation temperatures from 300 to 500°C. At the highest heater temperature the superficial Si layer contained larger precipitates and fewer defects than did wafers implanted at lower temperatures. Annealing of the as-implanted wafers significantly reduced structural differences. All wafers had a region of large, amorphous 10 to 50 nm precipitates in the lower two-thirds of the superficial Si layer while in the upper third of the layer there were a few threading dislocations. In wafers implanted at lower temperatures the buried oxide grew at the top surface only. During epitaxial Si growth the buried oxide layer thinned and the precipitate region above and below the oxide layer thickened for all wafers. There were no significant structural differences of the epitaxial Si layer for wafers with different implantation temperatures. The epitaxial layer was high quality single crystal Si and contained a few threading dislocations. Overall, structural differences in the epitaxial Si layer due to differences in implantation temperature were minimal.
    No preview · Article · Jan 2011 · MRS Online Proceeding Library
  • J. D. Lee · J. C. Park · S. J. Krause · P. Roitman · M. K. El-Ghor
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    ABSTRACT: The microstructural changes in oxygen implanted silicon-on-insulator material (SIMOX) at intermediate annealing steps and the changes by rapid thermal annealing (RTA) were studied with transmission electron microscopy. Defects found in as-implanted SIMOX, including multiply faulted defects, short stacking faults, and {113} defects, were all removed in anneals from 900°C to 1100°C. The threading dislocations in annealed material form at these temperatures during thermal ramping. RTA shows that the microstructure is significantly influenced by the ramp rate. The very high ramp rate in RTA results in very flat interfaces and a buried oxide layer with no Si islands, but significantly increases the defect density. Overall, the results show that intermediate thermal processing steps strongly affect the final microstructure of SIMOX material.
    No preview · Article · Jan 2011 · MRS Online Proceeding Library
  • J. C. Park · J. D. Lee · D. Venables · S. Krause · P. Roitman

    No preview · Article · Jan 2011 · MRS Online Proceeding Library
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    ABSTRACT: High resolution electron microscopy (HREM) has been used to study the atomic arrangement of defects formed during high-dose oxygen implantation of silicon-on-insulator material. The effect of implantation parameters of wafer temperature, dose, and current density were investigated. Wafer temperature had the largest effect on the type and character of the defects. Above the buried oxide layer in the top silicon layer, HREM revealed that microtwins and stacking faults were created during implantation from 350–450°C. From 450–550°C, stacking faults were longer and microtwinning was reduced. From 550–700°C, a new type of defect was observed which had lengths of 40 to 140 nm and consisted of several discontinuous stacking faults which were randomly spaced and separated by two to eight atomic layers. We have referred to them as “multiply faulted defects” (MFDs). Beneath the buried oxide layer in the substrate region, the defects observed included stacking faults and ( 113 ) defects. The results indicated that some parts of the ( 1131 defects can assume a cubic diamond structure created through a twin operation across (115) planes. Details of the structure and formation mechanisms of MFDs and other defects will be discussed.
    No preview · Article · Jan 2011 · MRS Online Proceeding Library
  • S. J. Krause · S. Seraphin · B. L. Chen · B. Cordts · P. Roitman
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    ABSTRACT: The formation of bubbles during high dose implantation of oxygen into silicon, and the subsequent transformation of the bubbles during annealing, were studied with transmission electron microscopy (TEM). There was a threshold for bubble formation at a minimum dose of 0.3 × 1018 oxygen/cm2 and a lower temperature of 550°C. As dose increased the bubbles grew larger and the bubble trails lengthened. However, increasing beam current by a factor of 10 or increasing temperature to 700°C did not affect bubble formation. Bubble evolution during intermediate temperature annealing was also studied using TEM techniques. For 2 hour anneals between 1000 and 1100°C the oxygen bubbles transform into SiO2 particles by first forming a “shell” of SiO2, which then facets, grows inward, and finally completely transforms the bubble into an oxide particle. At temperatures greater than 1100°C the oxide particles dissolve by outdiffusion of the oxygen to the wafer surface.
    No preview · Article · Jan 2011 · MRS Online Proceeding Library
  • L. Chen · S. Bagchi · S.J. Krause · P.R. Roitman
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    ABSTRACT: Fabrication of high-dose SIMOX (typically 1.8×10<sup>18</sup> cm<sup>2</sup> at 200 keV) is a maturing materials technology with increasing commercial usage. However, lower-dose SIMOX (2 to 4×10<sup>17</sup> cm<sup>2</sup>) has the potential to be more economical, as well as allow device designers a choice of oxide thickness, but film uniformity and quality must be as good or better than standard high-dose material. A variety of approaches to produce low-dose SIMOX have been used which include: low dose implant plus ITOX (internal thermal oxidation), which uses a second high temperature anneal with high oxygen concentration (Nakashima et al. 1996; Mrstik et al. 1995); multiple energy implants (Alles, 1997); lower energy implantation (Anc et al. 1998); rapid ramping to the high temperature anneal range (Ogura, 1998); N pre-implantation (Meyappan et al. 1995); and very-low dose, post-implant amorphization prior to high temperature annealing (Holland et al. 1996; Bagchi et al. 1997). For the last technique, it was reported there were changes in the precipitation mechanisms that control BOX development. The first was elimination of multiply-faulted defects as sites for preferred nucleation and growth of oxides which form a discontinuous upper layer of precipitates in untreated material. The second was enhanced diffusion of oxygen along defects and phase boundaries in the amorphized region to the single BOX layer that was developing. In this research, we extend the work on post-implant-amorphized low-dose SIMOX by reporting effects of a single-step high oxygen concentration anneal on its BOX microstructure
    No preview · Conference Paper · Feb 1999
  • P. Roitman · M. Edelstein · S.J. Krause
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    ABSTRACT: Summary form only given. Two defect types have been identified in the buried oxide of low dose SIMOX: conductive silicon paths through the buried oxide (pipes) and silicon precipitates in the buried oxide. Both types are caused by the same general mechanism: the tendency of the Si-SiO<sub>2</sub> system at high temperature to separate into regions of Si and SiO<sub>2</sub>, rather than forming SiO<sub>x</sub>. Below an oxygen dose of ~4×10<sup>17</sup> cm<sup>-2</sup>, the buried oxide is not continuous, and as the dose is lowered, the implanted region becomes a layer of SiO<sub>2</sub> precipitates. Above the dose of ~4×10<sup>17</sup> cm<sup>-2</sup>, the buried oxide is continuous, but Si precipitates ~50 nm thick are present in the oxide. This paper demonstrates techniques for the electrical detection of precipitates and pipes in low dose SIMOX buried oxides
    No preview · Conference Paper · Nov 1998
  • S. Bagchi · S.J. Krause · P.R. Roitman · D.K. Sadana
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    ABSTRACT: Summary form only given. In processing of SIMOX material, understanding the formation of the buried-oxide (BOX) layer and the effect of processing parameters is critical to production of high quality material. Most studies have focused on higher dose SIMOX material, typically 1.8×10<sup>18</sup> cm<sup>-2</sup>, but since the BOX is relatively thick (~400 nm), the defects, such as Si islands, have a small effect on electrical characteristics while the density of Si pipes, which short the top Si layer and the substrate, is very low. As dose is decreased, however, the pipe density can increase with a lower dose limit at which a continuous BOX can form. Recently, Holland et al. (1996) reported that pre-amorphization of the as-implanted region prior to annealing can extend the lower limit. It was proposed that rapid diffusion of oxygen along grain boundaries in the recrystallized layer promoted formation of a continuous BOX during annealing. To examine this phenomenon, we report a comparison of microstructural development during annealing of the BOX for untreated and post-amorphized implant low-dose SIMOX
    No preview · Conference Paper · Nov 1998
  • S. Bagchi · S.J. Krause · P. Roitman
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    ABSTRACT: There is increasing interest in low-dose SIMOX as a substrate material. Circuits fabricated on such wafers need to have a high-quality buried-oxide (BOX) with flat, uniform interfaces and density of pipes and of Si islands as low as possible. Si islands have been reported to be responsible for increased electrical leakage current through the BOX, or in extreme cases, its dielectric breakdown. While the thickness of such Si islands in high-dose SIMOX spans only 3-5% of the BOX thickness, in low-dose material they may span 50%, or more, of the total BOX thickness. As a result, the reduction of the effective thickness of BOX could lead to degradation of dielectric properties. Thus, the understanding of BOX microstructural development is an important issue for low-dose SIMOX. Here we are reporting the mechanism of the development of BOX microstructure for annealed SIMOX as a function of implantation dose
    No preview · Conference Paper · Nov 1997
  • S. Bagchi · S. J. Krause · P. Roitman
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    ABSTRACT: The effect of implantation dose on microstructural development of the buried oxide (BOX) of 200 keV oxygen implanted Si was studied by electron microscopy. A continuous BOX layer with a low density of Si islands was obtained for a dose of 0.45×1018 cm−2, following high temperature annealing. At a lower dose of 0.225×1018 cm−2 a layer did not form, but only disjointed, isolated, oxide precipitates developed. At a higher dose, 0.675×1018 cm−2, a continuous BOX layer with a high density of Si islands formed. Microstructures of intermediate-temperature annealed samples showed the formation of oxide precipitates at preferred depths, the morphology being dose dependent. The final microstructure of the BOX is strongly influenced by the evolution of the oxide precipitates during annealing. A qualitative mechanism is proposed for the dose-dependent behavior of BOX formation during the annealing process. © 1997 American Institute of Physics.
    No preview · Article · Oct 1997 · Applied Physics Letters
  • S. Bagchi · J.D. Lee · S.J. Krause · P. Roitman
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    ABSTRACT: Silicon-on-insulator material synthesized by oxygen implantation (SIMOX) offers the advantages of thickness uniformity and moderate defect density. This makes it a leading candidate for integrated circuit fabrication in the deep submicron (0.25 μm) regime. Low-dose SIMOX has high densities of crystalline and BOX defects. While the parameters for reduction of these defects have not been realized fully, it can be reasonably stated that the as-implanted oxygen profile has a crucial role in the subsequent development of microstructure. Implantation at lower doses (<200 keV) is potentially attractive from the perspective of reduced implant damage and a tighter oxygen profile. Possible additional benefits are in terms of reduced equipment cost and the ability to realize SIMOX with ultra-thin (&les;200 Å) top-silicon layer. We have compared the effect of two implant energies, namely 200 keV and 120 keV, on the defect formation
    No preview · Conference Paper · Jan 1996
  • S. Bagchi · J. D. Lee · S. J. Krause · P. Roitman
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    ABSTRACT: The defects and microstructure of low-dose (<0.7 × 1018 cm−2), oxygen-implanted silicon-on-insulator (SIMOX) material were investigated as a function of implant dose and annealing temperature by plan-view and cross-sectional transmission electron microscopy. The threading-dislocations in low-dose (0.2∼0.3×1018 cm−2), annealed SIMOX originate from unfaulting of long (∼10 μm), shallow (0.3 μm), extrinsic stacking faults generated during the ramping stage of annealing. As dose increases, the defect density is reduced and the structure of the buried oxide layer evolves dramatically. It was found that there is a dose window which gives a lower defect density and a continuous buried oxide with a reduced density of Si islands in the buried oxide.
    No preview · Article · Dec 1995 · Journal of Electronic Materials
  • S. Bagchi · J.D. Lee · S.J. Krause · P. Roitman
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    ABSTRACT: There are still important issues that remain on the microstructure of low-dose SIMOX that may affect its quality and performance as an SOI material. These issues include the presence of crystalline defects in the top Si layer and the presence of Si islands in the buried oxide (BOX) which can severely degrade dielectric properties. While the reasons for crystalline defect formation have been recently determined, the mechanism(s) of Si island formation in the BOX are still unclear. Such understanding could assist in improved processing for fabricating high quality BOX layers in low-dose SIMOX. In this paper we report on the effect of implant dose on the microstructural changes found during Si island formation
    No preview · Conference Paper · Nov 1995
  • J.H. Butler · D.C. Joy · G.F. Bradley · S.J. Krause
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    ABSTRACT: Micromorphological and microstructural characterizations of the type and degree of crystallinity and the relative dispersion of phases within polymers, as well as in the study of their surfaces and associated interfaces, offer a number of challenges in the field of materials science of polymers. Microscopy is a natural methodology for the acquisition of microstructural information, but for polymers there are few straightforward techniques. Conventional electron microscopy methods are limited in their ability to address fine surface details or to determine the bulk microstructure of multicomponent polymeric materials. Sometimes these problems can be overcome, but only within the practical restrictions associated with meticulous sample preparation.An extremely promising and efficient alternative to conventional approaches is the state-of-the-art, low-voltage scanning electron microscope (LVSEM). It is demonstrated here that straightforward operation of an LVSEM equipped with a field emission gun (FEG) source can produce topographical contrast secondary electron images of polymers at substantially higher magnifications than a conventional SEM, and with a resolution that rivals TEM. An added advantage is the capability of being able to produce contrast based on differences in chemical composition within the sample. The ability to produce quality images at low accelerating beam voltages minimizes beam damage to the sample, and affords an operating window (e.g. E2) where the sample does not build up negative charge. This obviates the normal requirement to coat samples with a conductive layer.We also describe experimental and theoretical developments that can help us to understand the physics of interaction between low-voltage electron beams and polymer samples. This knowledge base, along with further theoretical and instrumental development and the subsequent applications to polymers, promises a whole new field of electron microscope methodology based on the LVSEM.
    No preview · Article · Apr 1995 · Polymer
  • J.D. Lee · J.C. Park · S. Krause · P. Roitman
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    ABSTRACT: Silicon-on-insulator material synthesized by oxygen implantation (SIMOX) is a leading candidate for advanced large scale integrated circuit applications due to thickness uniformity and moderate defect density. In the past few years, there has been a significant reduction of the defect density by optimizing processing conditions. Studies on defect formation mechanisms may suggest further modification of the processing conditions for both production cost and material quality. Recently, it was shown that through-thickness defects (TTDs) in high-dose SIMOX originated from as-implanted defects, dislocation half-loops (DHLs). On the other hand, a high density (~10<sup>8</sup> cm <sup>-2</sup>) of defects in very low dose (0.25×10<sup>18</sup> cm<sup>-2</sup>) SIMOX has been observed by Nakashirna et al. (1993), but the origin of these defects has not been understood. In this paper we report on the effect of implant dose on defect formation mechanisms, and propose a defect formation mechanism in the very low-dose regime for the first time. It was found that the stacking faults generated during the initial stage of annealing are the origin of TTDs in the low-dose (<0.5×10<sup>18</sup> cm<sup>-2</sup>) regime, while as-implanted defects (DHL) are the origin of TTDs in the high-dose regime (>1.3×10<sup>18</sup> cm<sup>-2</sup>). Several approaches of process modification have been suggested for economical production of low-defect-density SIMOX
    No preview · Conference Paper · Nov 1994
  • J. D. Lee · J. C. Park · D. Venables · S. J. Krause · P. Roitman
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    ABSTRACT: The defect microstructure of silicon‐on‐insulator wafers produced by multiple cycles of oxygen implantation and annealing was studied with transmission electron microscopy. The dominant defects are stacking fault pyramids (SFPs), 30–100 nm wide, located at the upper buried oxide interface at a density of ∼10<sup>6</sup> cm<sup>-2</sup>. The defects are produced by the expansion and interaction of narrow stacking fault (NSF) ribbons pinned to residual precipitates in the top silicon layer. Consideration of the energetics of the transformation from a collection of four NSF ribbons to a single SFP indicates that the reaction is energetically favorable below a critical NSF length. Thus small defects are stable as SFPs while large defects are stable as NSF ribbons.
    No preview · Article · Jan 1994 · Applied Physics Letters

Publication Stats

198 Citations
33.74 Total Impact Points

Institutions

  • 1984-1997
    • Arizona State University
      • • Department of Chemical Engineering
      • • Department of Chemistry and Biochemistry
      • • Department of Materials Science and Engineering
      • • Department of Mechanical Engineering
      Phoenix, Arizona, United States
  • 1991
    • Spire Corporation
      Bedford, Massachusetts, United States