Island growth as a growth mode in atomic layer deposition

A phenomenological model

Riikka Puurunen (Corresponding Author), Wilfried Vandervorst

Research output: Contribution to journalArticleScientificpeer-review

193 Citations (Scopus)

Abstract

Atomic layer deposition (ALD) has recently gained world-wide attention because of its suitability for the fabrication of conformal material layers with thickness in the nanometer range. Although the principles of ALD were realized about 40 years ago, the description of many physicochemical processes that occur during ALD growth is still under development. A constant amount of material deposited in an ALD reaction cycle, that is, growth-per-cycle (GPC), has been a paradigm in ALD through decades. The GPC may vary, however, especially in the beginning of the ALD growth. In this work, a division of ALD processes to four classes is proposed, on the basis of how the GPC varies with the number of ALD reaction cycles: linear growth, substrate-enhanced growth, and substrate-inhibited growth of type 1 and type 2. Island growth is identified as a likely origin for type 2 substrate-inhibited growth, where the GPC increases and goes through a maximum before it settles to a constant value characteristic of a steady growth. A simple phenomenological model is developed to describe island growth in ALD. The model assumes that the substrate is unreactive with the ALD reactants, except for reactive defects. ALD growth is assumed to proceed symmetrically from the defects, resulting islands of a conical shape. Random deposition is the growth mode on the islands. The model allows the simulation of GPC curves, surface fraction curves, and surface roughness, with physically significant parameters. When the model is applied to the zirconium tetrachloride/water and the trimethylaluminum/water ALD processes on hydrogen-terminated silicon, the calculated GPC curves and surface fractions agree with the experiments. The island growth model can be used to assess the occurrence of island growth, the size of islands formed, and point of formation of a continuous ALD-grown film. The benefits and limitations of the model and the general characteristics of type 2 substrate-inhibited ALD are discussed.
Original languageEnglish
Pages (from-to)7686 - 7695
Number of pages10
JournalJournal of Applied Physics
Volume96
Issue number12
DOIs
Publication statusPublished - 2004
MoE publication typeA1 Journal article-refereed

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atomic layer epitaxy
cycles
curves
tetrachlorides
defects

Keywords

  • zirconium compounds
  • alumina
  • thin films
  • atomic layer deposition
  • reaction rate constants
  • surface composition
  • surface roughness

Cite this

Puurunen, Riikka ; Vandervorst, Wilfried. / Island growth as a growth mode in atomic layer deposition : A phenomenological model. In: Journal of Applied Physics. 2004 ; Vol. 96, No. 12. pp. 7686 - 7695.
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Island growth as a growth mode in atomic layer deposition : A phenomenological model. / Puurunen, Riikka (Corresponding Author); Vandervorst, Wilfried.

In: Journal of Applied Physics, Vol. 96, No. 12, 2004, p. 7686 - 7695.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Island growth as a growth mode in atomic layer deposition

T2 - A phenomenological model

AU - Puurunen, Riikka

AU - Vandervorst, Wilfried

PY - 2004

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AB - Atomic layer deposition (ALD) has recently gained world-wide attention because of its suitability for the fabrication of conformal material layers with thickness in the nanometer range. Although the principles of ALD were realized about 40 years ago, the description of many physicochemical processes that occur during ALD growth is still under development. A constant amount of material deposited in an ALD reaction cycle, that is, growth-per-cycle (GPC), has been a paradigm in ALD through decades. The GPC may vary, however, especially in the beginning of the ALD growth. In this work, a division of ALD processes to four classes is proposed, on the basis of how the GPC varies with the number of ALD reaction cycles: linear growth, substrate-enhanced growth, and substrate-inhibited growth of type 1 and type 2. Island growth is identified as a likely origin for type 2 substrate-inhibited growth, where the GPC increases and goes through a maximum before it settles to a constant value characteristic of a steady growth. A simple phenomenological model is developed to describe island growth in ALD. The model assumes that the substrate is unreactive with the ALD reactants, except for reactive defects. ALD growth is assumed to proceed symmetrically from the defects, resulting islands of a conical shape. Random deposition is the growth mode on the islands. The model allows the simulation of GPC curves, surface fraction curves, and surface roughness, with physically significant parameters. When the model is applied to the zirconium tetrachloride/water and the trimethylaluminum/water ALD processes on hydrogen-terminated silicon, the calculated GPC curves and surface fractions agree with the experiments. The island growth model can be used to assess the occurrence of island growth, the size of islands formed, and point of formation of a continuous ALD-grown film. The benefits and limitations of the model and the general characteristics of type 2 substrate-inhibited ALD are discussed.

KW - zirconium compounds

KW - alumina

KW - thin films

KW - atomic layer deposition

KW - reaction rate constants

KW - surface composition

KW - surface roughness

U2 - 10.1063/1.1810193

DO - 10.1063/1.1810193

M3 - Article

VL - 96

SP - 7686

EP - 7695

JO - Journal of Applied Physics

JF - Journal of Applied Physics

SN - 0021-8979

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ER -