Gettering in Silicon

McHugo, Scott A.; Hieslmair, H.

doi:10.1002/047134608x.w3209

Cited by 3 publications

(3 citation statements)

References 190 publications

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“…In addition, the transport of ionized Li Zn acceptors towards the O-face may be promoted by an enhanced concentration of zinc vacancies (V Zn ) during the heat treatments (in air) because of a low Zn partial pressure at the sample surfaces (compared with that of oxygen) [13]. Another interesting approach of controlling the Li behaviour in ZnO was explored by Børseth et al [14,15] and resembles extrinsic gettering of fast diffusing metal impurities in silicon by defect engineering [16]. The host of the experimental data in [14,15], including SIMS profiling, scanning spreading resistance measurements and positron annihilation spectroscopy (PAS), were interpreted in terms of Li impurities being electrically passivated through trapping by vacancy clusters, generated by ion implantation and subsequent flash annealing.…”

Section: Mastering Of Li; Concentration and Electrical Propertiesmentioning

confidence: 99%

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Zinc oxide: bulk growth, role of hydrogen and Schottky diodes

Monakhov¹,

Kuznetsov²,

Svensson³

2009

J. Phys. D: Appl. Phys.

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Zinc oxide (ZnO) is a wide band gap semiconductor material with attractive features for light emitting devices, photovoltaics, chemical sensors and spintronics. In the past 10 yr ZnO has attracted tremendous interest from the materials science and semiconductor physics research communities, and in this review recent progress in (i) bulk growth, (ii) understanding of the role of hydrogen and (iii) formation of high-quality Schottky barrier (SB) diodes, are discussed for single crystalline ZnO. In (i), the emphasis is put on hydrothermally grown material and how the concentration of intentional and unintentional impurities, such as In and Li, can be controlled and modified by high temperature treatment and defect engineering involving vacancy clusters. In (ii), different possible configurations of hydrogen as a shallow donor are evaluated based on results from calculations employing the density-functional-theory as well as from experimental studies of local vibrational modes using Fourier transform infrared spectroscopy. Further, hydrogen is demonstrated to be very reactive and the interaction with zinc vacancies, group I and group V elements, and transition metals are elucidated. Moreover, the diffusion of hydrogen is found to be rapid and limited by the concentration of traps in hydrothermal samples, and it is argued that isolated (free) hydrogen is not very likely to exist in ZnO at room temperature. In (iii), a compilation of the literature data illustrates that the SB heights for metals deposited on n-type samples have no correlation with the metal work function, violating the fundamental Schottky–Mott model. The role of surface preparation cannot be overestimated and in several cases an oxidation of the surface prior to metal deposition is shown to be beneficial for the formation of high barrier SB diodes. The effects of near-surface defects, such as oxygen vacancies, and contact inhomogeneity are also addressed. However, in spite of the significant progress made in the past 5–7 years, a thorough understanding of the SB formation to ZnO is still lacking. Finally, results from characterization of electrically active point defects employing the SB contacts and junction spectroscopic techniques are reviewed and the identification of some prominent bandgap states is critically evaluated.

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Section: Mastering Of Li; Concentration and Electrical Propertiesmentioning

confidence: 99%

“…Figure16. Apparent built-in voltage deduced from the C-V characteristics of an ideal two-phase parallel SB contact as a function the relative contact area occupied by the phase with low barrier height.…”

mentioning

confidence: 99%

Zinc oxide: bulk growth, role of hydrogen and Schottky diodes

Monakhov¹,

Kuznetsov²,

Svensson³

2009

J. Phys. D: Appl. Phys.

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“…Segregation gettering is driven by a gradient or a discontinuity in the impurity solubility. According to McHugo and Hieslmair [21], the segregation effect can result from: (a) a difference in phase, for example between crystalline and liquid silicon during crystal growth, (b) a difference in material, for example aluminum, which has a greater solubility for metal impurities than silicon, (c) the Fermi level effect, (d) ionpairing and (e) strain, which may increase or decrease the solubility of metal impurities. The region of higher solubility acts as a sink for metals from the lower-solubility region.…”

Section: Gettering Mechanismsmentioning

confidence: 99%

Gettering simulator: physical basis and algorithm

Hieslmair¹,

Balasubramanian²,

Istratov³

et al. 2001

Semicond. Sci. Technol.

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The basic physical principles and mechanisms of gettering of metal impurities in silicon are well established. However, a predictive model of gettering that would enable one to determine what fraction of contaminants will be gettered in a particular process and how the existing process should be modified to optimize gettering is lacking. Predictive gettering of transition metals in silicon requires development of a robust algorithm to model diffusion and precipitation of transition metals in silicon, and material parameters to describe the kinetics of defect reactions and the stable equilibrium state of the formed complexes. This paper describes the algorithm of a gettering simulator, capable of modelling relaxation and segregation gettering of interstitially diffusing transition metal impurities in silicon wafers. The basic physical equations used to model gettering are differential equations for diffusion, precipitation and segregation. These equations are solved using the implicit finite-difference algorithm, based on the underlying physics of the problem. The material parameters required as input for the gettering simulator such as segregation coefficient, precipitation site density and precipitation radius, which need to be obtained experimentally, are briefly discussed.

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