On the nanoindentation characterization of Al2O3 thin films grown on Si-wafer by atomic layer deposition

Xuwen Liu (Corresponding author), Eero Haimi, Simo-Pekka Hannula, Riikka L. Puurunen, Oili Ylivaara

Research output: Chapter in Book/Report/Conference proceedingConference abstract in proceedingsScientific

Abstract

Atomic layer deposition (ALD) is one of the most promising technologies in producing highly conformal coatings with a strict tolerance in thickness. In the study, ALD Al2O3 coatings of thickness varying from 10 to 600 nm are produced on single-side polished silicon (SSP-Si) wafer at the deposition temperature of 300 °C. This study aims in developing a convenient, efficient and inexpensive method of obtaining reliable coating properties via instrumented nanoindentation to meet the demand of silicon-based microelectronics industry. Hardness and elastic modulus are the most common mechanical properties that are directly derived from nanoindentation data. From Oliver and Pharr's analysis, the unloading data can be well described by a power-law relation: P = a(h-hf)m, where P is the indent load, hf is the residual depth after complete unloading and a and m are material constants. The power-law exponent, m, is found only slightly material dependent for a variety of materials, its value falling between 1.2 and 1.6. However, large m values up to 4 are obtained in certain materials in a consistent basis so that instrument/environment origin can be ruled out. According to the elastic assumption and the extended Hertzian treatment on unloading, m>2 has no physical meaning. The large m is often ascribed to inelastic or reverse plasticity in unloading. Silicon is one of the materials that can demonstrate reverse plasticity through phase transformation during unloading. A careful investigation of the unloading phenomena of the silicon wafer established that reverse plasticity occurred when contact depth was larger than about 8 nm, indicated by large m values at about 3.5. Meanwhile, the characteristics of the loading curve indicate that this depth marked the moment at which transition from elastic to elastic-plastic deformation on loading occurred. When the ALD Al2O3 coatings on the Si-wafer were indented, m dropped and varied narrowly around 1.5 over a large range of indent depths. A conclusion was then reached that the plot of m vs. hC (indent depth) could be used to monitor whether the Si substrate was in elastic or elastic-plastic state when the whole system was under external loading. This provided a guideline for picking up correct values of coating property under the conditions that the substrate only provided elastic support of a small fraction of the indenting load. As a result, it was found that the 10% rule commonly used in extracting coating property from a layered structure could be relaxed and the subtle property differences between the Al2O3 coatings and the Si substrate were revealed with good confidence.
Original languageEnglish
Title of host publicationTechnical Program & Abstracts
PublisherAmerican Vacuum Society AVS
Publication statusPublished - 2012
Event12th International Conference on Atomic Layer Deposition, ALD 2012 - Dresden, Germany
Duration: 17 Jun 201220 Jun 2012
Conference number: 12

Conference

Conference12th International Conference on Atomic Layer Deposition, ALD 2012
Abbreviated titleALD 2012
CountryGermany
CityDresden
Period17/06/1220/06/12

Fingerprint

unloading
atomic layer epitaxy
nanoindentation
wafers
coatings
thin films
plastic properties
silicon
elastic deformation
falling
microelectronics
plastic deformation
phase transformations
coating
confidence
modulus of elasticity
hardness
plastics
plots
industries

Keywords

  • atomic layer deposition
  • ALD
  • aluminum oxide
  • nanoindentation

Cite this

Liu, X., Haimi, E., Hannula, S-P., Puurunen, R. L., & Ylivaara, O. (2012). On the nanoindentation characterization of Al2O3 thin films grown on Si-wafer by atomic layer deposition. In Technical Program & Abstracts American Vacuum Society AVS.
Liu, Xuwen ; Haimi, Eero ; Hannula, Simo-Pekka ; Puurunen, Riikka L. ; Ylivaara, Oili. / On the nanoindentation characterization of Al2O3 thin films grown on Si-wafer by atomic layer deposition. Technical Program & Abstracts. American Vacuum Society AVS, 2012.
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title = "On the nanoindentation characterization of Al2O3 thin films grown on Si-wafer by atomic layer deposition",
abstract = "Atomic layer deposition (ALD) is one of the most promising technologies in producing highly conformal coatings with a strict tolerance in thickness. In the study, ALD Al2O3 coatings of thickness varying from 10 to 600 nm are produced on single-side polished silicon (SSP-Si) wafer at the deposition temperature of 300 °C. This study aims in developing a convenient, efficient and inexpensive method of obtaining reliable coating properties via instrumented nanoindentation to meet the demand of silicon-based microelectronics industry. Hardness and elastic modulus are the most common mechanical properties that are directly derived from nanoindentation data. From Oliver and Pharr's analysis, the unloading data can be well described by a power-law relation: P = a(h-hf)m, where P is the indent load, hf is the residual depth after complete unloading and a and m are material constants. The power-law exponent, m, is found only slightly material dependent for a variety of materials, its value falling between 1.2 and 1.6. However, large m values up to 4 are obtained in certain materials in a consistent basis so that instrument/environment origin can be ruled out. According to the elastic assumption and the extended Hertzian treatment on unloading, m>2 has no physical meaning. The large m is often ascribed to inelastic or reverse plasticity in unloading. Silicon is one of the materials that can demonstrate reverse plasticity through phase transformation during unloading. A careful investigation of the unloading phenomena of the silicon wafer established that reverse plasticity occurred when contact depth was larger than about 8 nm, indicated by large m values at about 3.5. Meanwhile, the characteristics of the loading curve indicate that this depth marked the moment at which transition from elastic to elastic-plastic deformation on loading occurred. When the ALD Al2O3 coatings on the Si-wafer were indented, m dropped and varied narrowly around 1.5 over a large range of indent depths. A conclusion was then reached that the plot of m vs. hC (indent depth) could be used to monitor whether the Si substrate was in elastic or elastic-plastic state when the whole system was under external loading. This provided a guideline for picking up correct values of coating property under the conditions that the substrate only provided elastic support of a small fraction of the indenting load. As a result, it was found that the 10{\%} rule commonly used in extracting coating property from a layered structure could be relaxed and the subtle property differences between the Al2O3 coatings and the Si substrate were revealed with good confidence.",
keywords = "atomic layer deposition, ALD, aluminum oxide, nanoindentation",
author = "Xuwen Liu and Eero Haimi and Simo-Pekka Hannula and Puurunen, {Riikka L.} and Oili Ylivaara",
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booktitle = "Technical Program & Abstracts",
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Liu, X, Haimi, E, Hannula, S-P, Puurunen, RL & Ylivaara, O 2012, On the nanoindentation characterization of Al2O3 thin films grown on Si-wafer by atomic layer deposition. in Technical Program & Abstracts. American Vacuum Society AVS, 12th International Conference on Atomic Layer Deposition, ALD 2012, Dresden, Germany, 17/06/12.

On the nanoindentation characterization of Al2O3 thin films grown on Si-wafer by atomic layer deposition. / Liu, Xuwen (Corresponding author); Haimi, Eero; Hannula, Simo-Pekka; Puurunen, Riikka L.; Ylivaara, Oili.

Technical Program & Abstracts. American Vacuum Society AVS, 2012.

Research output: Chapter in Book/Report/Conference proceedingConference abstract in proceedingsScientific

TY - CHAP

T1 - On the nanoindentation characterization of Al2O3 thin films grown on Si-wafer by atomic layer deposition

AU - Liu, Xuwen

AU - Haimi, Eero

AU - Hannula, Simo-Pekka

AU - Puurunen, Riikka L.

AU - Ylivaara, Oili

N1 - Published abstract of a poster 74717 MECHALD

PY - 2012

Y1 - 2012

N2 - Atomic layer deposition (ALD) is one of the most promising technologies in producing highly conformal coatings with a strict tolerance in thickness. In the study, ALD Al2O3 coatings of thickness varying from 10 to 600 nm are produced on single-side polished silicon (SSP-Si) wafer at the deposition temperature of 300 °C. This study aims in developing a convenient, efficient and inexpensive method of obtaining reliable coating properties via instrumented nanoindentation to meet the demand of silicon-based microelectronics industry. Hardness and elastic modulus are the most common mechanical properties that are directly derived from nanoindentation data. From Oliver and Pharr's analysis, the unloading data can be well described by a power-law relation: P = a(h-hf)m, where P is the indent load, hf is the residual depth after complete unloading and a and m are material constants. The power-law exponent, m, is found only slightly material dependent for a variety of materials, its value falling between 1.2 and 1.6. However, large m values up to 4 are obtained in certain materials in a consistent basis so that instrument/environment origin can be ruled out. According to the elastic assumption and the extended Hertzian treatment on unloading, m>2 has no physical meaning. The large m is often ascribed to inelastic or reverse plasticity in unloading. Silicon is one of the materials that can demonstrate reverse plasticity through phase transformation during unloading. A careful investigation of the unloading phenomena of the silicon wafer established that reverse plasticity occurred when contact depth was larger than about 8 nm, indicated by large m values at about 3.5. Meanwhile, the characteristics of the loading curve indicate that this depth marked the moment at which transition from elastic to elastic-plastic deformation on loading occurred. When the ALD Al2O3 coatings on the Si-wafer were indented, m dropped and varied narrowly around 1.5 over a large range of indent depths. A conclusion was then reached that the plot of m vs. hC (indent depth) could be used to monitor whether the Si substrate was in elastic or elastic-plastic state when the whole system was under external loading. This provided a guideline for picking up correct values of coating property under the conditions that the substrate only provided elastic support of a small fraction of the indenting load. As a result, it was found that the 10% rule commonly used in extracting coating property from a layered structure could be relaxed and the subtle property differences between the Al2O3 coatings and the Si substrate were revealed with good confidence.

AB - Atomic layer deposition (ALD) is one of the most promising technologies in producing highly conformal coatings with a strict tolerance in thickness. In the study, ALD Al2O3 coatings of thickness varying from 10 to 600 nm are produced on single-side polished silicon (SSP-Si) wafer at the deposition temperature of 300 °C. This study aims in developing a convenient, efficient and inexpensive method of obtaining reliable coating properties via instrumented nanoindentation to meet the demand of silicon-based microelectronics industry. Hardness and elastic modulus are the most common mechanical properties that are directly derived from nanoindentation data. From Oliver and Pharr's analysis, the unloading data can be well described by a power-law relation: P = a(h-hf)m, where P is the indent load, hf is the residual depth after complete unloading and a and m are material constants. The power-law exponent, m, is found only slightly material dependent for a variety of materials, its value falling between 1.2 and 1.6. However, large m values up to 4 are obtained in certain materials in a consistent basis so that instrument/environment origin can be ruled out. According to the elastic assumption and the extended Hertzian treatment on unloading, m>2 has no physical meaning. The large m is often ascribed to inelastic or reverse plasticity in unloading. Silicon is one of the materials that can demonstrate reverse plasticity through phase transformation during unloading. A careful investigation of the unloading phenomena of the silicon wafer established that reverse plasticity occurred when contact depth was larger than about 8 nm, indicated by large m values at about 3.5. Meanwhile, the characteristics of the loading curve indicate that this depth marked the moment at which transition from elastic to elastic-plastic deformation on loading occurred. When the ALD Al2O3 coatings on the Si-wafer were indented, m dropped and varied narrowly around 1.5 over a large range of indent depths. A conclusion was then reached that the plot of m vs. hC (indent depth) could be used to monitor whether the Si substrate was in elastic or elastic-plastic state when the whole system was under external loading. This provided a guideline for picking up correct values of coating property under the conditions that the substrate only provided elastic support of a small fraction of the indenting load. As a result, it was found that the 10% rule commonly used in extracting coating property from a layered structure could be relaxed and the subtle property differences between the Al2O3 coatings and the Si substrate were revealed with good confidence.

KW - atomic layer deposition

KW - ALD

KW - aluminum oxide

KW - nanoindentation

M3 - Conference abstract in proceedings

BT - Technical Program & Abstracts

PB - American Vacuum Society AVS

ER -

Liu X, Haimi E, Hannula S-P, Puurunen RL, Ylivaara O. On the nanoindentation characterization of Al2O3 thin films grown on Si-wafer by atomic layer deposition. In Technical Program & Abstracts. American Vacuum Society AVS. 2012