S.J. Krause

Arizona State University, Mesa, AZ, United States

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Publications (27)14.39 Total impact

  • 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
    SOI Conference, 1999. Proceedings. 1999 IEEE International; 02/1999
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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
    SOI Conference, 1998. Proceedings., 1998 IEEE International; 11/1998
  • 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
    SOI Conference, 1998. Proceedings., 1998 IEEE International; 11/1998
  • 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
    SOI Conference, 1997. Proceedings., 1997 IEEE International; 11/1997
  • 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.
    Applied Physics Letters 10/1997; 71(15):2136-2138. · 3.52 Impact Factor
  • 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
    SOI Conference, 1996. Proceedings., 1996 IEEE International; 01/1996
  • 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.
    Journal of Electronic Materials 12/1995; 25(1):7-12. · 1.64 Impact Factor
  • 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
    SOI Conference, 1995. Proceedings., 1995 IEEE International; 11/1995
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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
    SOI Conference, 1994 Proceedings., 1994 IEEE International; 11/1994
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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.
    Applied Physics Letters 01/1994; · 3.52 Impact Factor
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    ABSTRACT: In this paper we describe the origin and characteristics of the defect structures in contemporary SIMOX and show how their densities are controlled by the processing method and conditions
    SOI Conference, 1993. Proceedings., 1993 IEEE International; 11/1993
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    ABSTRACT: Defect microstructure and the near-surface strain of high-dose oxygen implanted silicon-on-insulator material (SIMOX) were investigated as a function of dose, implant temperature, and annealing temperature by transmission electron microscopy and high resolution x-ray diffraction. Dislocation half loops (DHLs) begin to form by stress assisted climb at a critical stress level due to implantation-induced damage. DHLs evolve into through-thickness defect (TTD) pairs by expansion during annealing. Both DHL and TTD-pair density increase with higher implant dose and lower implant temperature. Possible methods for defect density reduction are suggested based on the results of this study.
    MRS Proceedings. 12/1992; 316.
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    ABSTRACT: Not Available
    SOI Conference, 1992. IEEE International; 11/1992
  • S.J. Krause, B.L. Chen, M.K. El-Ghor
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    ABSTRACT: Rapid thermal annealing (RTA) plus conventional annealing has been used to examine heating rate effects on microstructure for higher temperature implanted SIMOX (separation by implanted oxygen). Material used for this study was a (100) wafer of SIMOX material that was implanted at 200 keV to a dose of 1.8×10<sup>18</sup> at 620°C. It was rapidly thermal annealed in a lamp annealer for 1 min at 1320°C. The heating rate was about 100°C s<sup>-1</sup>. A portion of this sample was then conventionally annealed in a tube furnace for 5 h at 1320°C in an atmosphere of argon plus 1/2% oxygen. The heating rate was 1°C s<sup>-1</sup>. A TEM (transmission electron microscope) image of the RTA+CA sample is shown. There is a dramatic difference in this sample compared to one which has only been conventionally annealed. Defects are seen in the top Si layer and plan view images give a density of 10<sup>9</sup> cm<sup>-2</sup>. This is three orders of magnitude greater than a typical CA sample. These defects were first formed during the RTA and were retained during the CA step. This indicates that the high rate of heating in the RTA step can increase the defect density
    SOI Conference, 1991. Proceedings, 1991., IEEE International; 11/1991
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    ABSTRACT: The authors report on an extensive study of a Secco etch process for determining dislocation densities that was performed by three different groups using nine SIMOX (separation by implanted oxygen) wafers from the same lot. The average dislocation density across the entire current data set (except transmission electron microscopy, TEM) is 2.2×10<sup>6</sup>/cm<sup>2</sup> with a standard deviation of 1.0×10<sup>6</sup>/cm<sup>2</sup>. Most of the data points are in the low 10<sup>6</sup> dislocations/cm<sup>2</sup> range, in agreement with the TEM results, and indicate good consistency of results from facility to facility
    SOI Conference, 1991. Proceedings, 1991., IEEE International; 11/1991
  • J.C. Park, S.J. Krause, P. Roitman
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    ABSTRACT: The authors report on the microstructural changes in HT (high-temperature-implanted) SIMOX (separation by implanted oxygen) at various stages in the ramping process by simulating the thermal treatment with two-hour anneals at intermediate temperatures. The wafers studied were implanted to 1.8×10<sup>18</sup> cm<sup>-2</sup> at 200 keV at a temperature of 620°C. To simulate the effect of the thermal ramping cycle, wafers were annealed for 2 hours at 50°C intervals from 800°C to 1100°C. Cross section samples were studied with conventional transmission electron microscopy (TEM) techniques at 200 keV. Major microstructural changes are shown to occur in SIMOX during the thermal ramping cycle between temperatures of 900°C and 1100°C. These changes strongly affect, possibly even control, the final defect density and buried oxide microstructure, even prior to the final high temperature anneal. Dislocation formation in SIMOX occurs during thermal ramping, probably between 1000°C and 1100°C. This suggests that it may be possible to further reduce dislocation densities of 10<sup>6</sup> cm<sup>-2</sup>, as found in HT SIMOX, by altering the thermal ramping cycle
    SOI Conference, 1991. Proceedings, 1991., IEEE International; 11/1991
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    ABSTRACT: Conventional and high resolution electron microscopy (HREM) were used to study the structure of {113} defects in high-dose oxygen implanted silicon. The defects are created with a density of 1011 cm−2 below the buried oxide layer in the substrate region. The HREM images of the {113} defects are similar to the ribbon-like defects in bulk silicon. It is proposed that there is a third possible structure of the defects, in addition to coesite and/or hexagonal structures. Portions of some defects exhibit the original cubic diamond structure which is twinned across {115} planes. The atomic model shows that the {115} interface is a coherent interface with alternating five- and seven-membered rings and no dangling bonds.
    Journal of Materials Research. 03/1991; 6(04):792 - 795.
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    ABSTRACT: A multiply faulted defect (MFD), has been observed at a density of 10<sup>8</sup> cm<sup>-2</sup> in oxygen implanted silicon‐on‐insulator material at implantation temperatures of ≥600 °C over a dose range from 0.3 to 1.8×10<sup>18</sup> cm<sup>-2</sup>. The MFDs are 40–140 nm long and are created at the upper edge of the high‐dose implantation region. They consist of combinations of several discontinuous stacking faults within 2–8 atomic layers which generate an irregularity along the defect. The atomic arrangement of the MFDs indicates that they form by shearing of the lattice due to the volume change associated with oxide precipitation. The defects have a randomly faulted arrangement from cross slip and from the presence of several inhomogeneous nucleation sites along the edge of the same defect.
    Journal of Applied Physics 03/1991; · 2.21 Impact Factor
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    ABSTRACT: Conventional and high resolution electron microscopy were used to study the structure of silicon-on-insulator material synthesized at higher temperature and higher current density (1 mA cm-2) than are conventionally used. As dose increases from 0.3 to 1.8×1018 cm-2 the buried xide thickensto 0.3 microm and trails of bubbles from at the surface which increase in size to 14 nm and depth to 0.15 microm. The defect structure in the top Si layer, consisting of multiple stacking faults located only near the buried oxide interface, remains constant with dosage. During the early stages of annealing, the bubbles and the multiply faulted defects are eliminated and large (20–30 nm) precipitates with lateral dislocations form near the buried oxide interface. Increasing the temperature from 1250 to 1350°C, causes precipitates to grow and to incorporate into the oxide layer. The pinned dislocations are eliminated simultaneously with the incorporated precipitates. This results in a defect density of only 105 cm-2m which is three to four orders less than material implanted at lower temperatures and medium current density.
    Vacuum. 01/1991; 42:353-358.
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    ABSTRACT: The effect of annealing ambient on the precipitate removal processes in high‐dose oxygen implanted silicon [separation by implantation of oxygen (SIMOX)] has been studied with transmission electron microscopy, electron energy‐loss spectroscopy, and secondary ion mass spectroscopy. The rate of removal of oxide precipitates from the top silicon layer in SIMOX is higher during annealing in argon than in nitrogen. The removal is reduced in nitrogen due to the formation of an oxynitride complex at the precipitate surfaces which inhibits oxygen diffusion across the interfaces. Similar effects have been observed for oxide precipitation during nitrogen ambient annealing in bulk silicon.
    Applied Physics Letters 01/1991; 59:3003-3005. · 3.52 Impact Factor

Publication Stats

30 Citations
14.39 Total Impact Points

Institutions

  • 1988–1997
    • Arizona State University
      • • Department of Chemistry and Biochemistry
      • • Department of Chemical Engineering
      Mesa, AZ, United States
  • 1991
    • Spire Corporation
      Bedford, Massachusetts, United States
    • National Institute of Standards and Technology
      Maryland, United States