Stresses in ALD films

Aiming for zero stress thin films

Riina Ritasalo, Oili Ylivaara, Tero Pilvi, Tommi Suni

Research output: Contribution to conferenceConference AbstractScientificpeer-review

Abstract

When grown films by atomic layer deposition (ALD) both intrinsic and thermal stresses are formed into the film; latter due to the mismatch in the thermal expansion coefficient of the substrate and the grown film. Films under high residual stress may cause problems for further processing, and for device performance and reliability. High residual stress can induce film delamination or buckling; bend released structures or the materials where the films are attached. Especially in microelectromechanical system (MEMS) manufacturing, zero or well-controlled residual stress is desired, as the stress effect is more prominent on released structures. Here, the residual stress measured from most common metal oxides deposited by thermal ALD processes on silicon substrates are presented. The thermal processes have an advantage that those can be scaled up to batch processing to achieve through-put and cost efficiency required for volume production. By varying the process parameters (e.g. temperature, chemicals) we aim for zero stress films or film stacks as well as for comprehensive stress data set to help for example MEMS designers and process integrators choosing proper thin film material, and ALD process chemistry and process conditions.
All films were grown in Picosun™ R-200 advanced reactors using thermal ALD processes. Deposited materials were HfO2, TiO2, SiO2, Al2O3 and Ta2O5 and combinations of these. The ALD temperature was varied between 150°C and 300°C. The substrates used were 150 mm diameter double side polished silicon wafers, which have been pre-measured for stresses before the ALD. For stress measurement we used TOHO FLX-2320-S wafer curvature measurement tool and the measurements were carried out at room temperature. Deposited film thicknesses were measured with Semilab SE-2000 ellipsometer.
Residual stress data from most common metal oxides are presented. For some of the films there is also comparison for the same film material made with different precursors. In Figure 1 the residual stress data for the HfO2 film grown at varying temperature is presented. The stress changes from compressive to tensile as the ALD temperature was increased from 150°C to 200°C.
Original languageEnglish
Pages49
Publication statusPublished - 29 Jul 2018
MoE publication typeNot Eligible
Event18th International Conference on Atomic Layer Deposition, ALD/ALE 2018: Featuring the 5th International Atomic Layer Etching Workshop - Songdo Convensia in Incheon, Incheon, Korea, Republic of
Duration: 29 Jul 20181 Aug 2018
https://ald2018.avs.org/

Conference

Conference18th International Conference on Atomic Layer Deposition, ALD/ALE 2018
Abbreviated titleALD/ALE 2018
CountryKorea, Republic of
CityIncheon
Period29/07/181/08/18
Internet address

Fingerprint

atomic layer epitaxy
thin films
residual stress
microelectromechanical systems
metal oxides
thermal reactors
batch processing
wafers
ellipsometers
temperature
stress measurement
integrators
silicon
buckling
thermal stresses
thermal expansion
film thickness
manufacturing
curvature
chemistry

Keywords

  • ALD
  • Atomic Layer Deposition
  • residual stress

Cite this

Ritasalo, R., Ylivaara, O., Pilvi, T., & Suni, T. (2018). Stresses in ALD films: Aiming for zero stress thin films. 49. Abstract from 18th International Conference on Atomic Layer Deposition, ALD/ALE 2018, Incheon, Korea, Republic of.
Ritasalo, Riina ; Ylivaara, Oili ; Pilvi, Tero ; Suni, Tommi. / Stresses in ALD films : Aiming for zero stress thin films. Abstract from 18th International Conference on Atomic Layer Deposition, ALD/ALE 2018, Incheon, Korea, Republic of.
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Ritasalo, R, Ylivaara, O, Pilvi, T & Suni, T 2018, 'Stresses in ALD films: Aiming for zero stress thin films' 18th International Conference on Atomic Layer Deposition, ALD/ALE 2018, Incheon, Korea, Republic of, 29/07/18 - 1/08/18, pp. 49.

Stresses in ALD films : Aiming for zero stress thin films. / Ritasalo, Riina; Ylivaara, Oili; Pilvi, Tero; Suni, Tommi.

2018. 49 Abstract from 18th International Conference on Atomic Layer Deposition, ALD/ALE 2018, Incheon, Korea, Republic of.

Research output: Contribution to conferenceConference AbstractScientificpeer-review

TY - CONF

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T2 - Aiming for zero stress thin films

AU - Ritasalo, Riina

AU - Ylivaara, Oili

AU - Pilvi, Tero

AU - Suni, Tommi

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N2 - When grown films by atomic layer deposition (ALD) both intrinsic and thermal stresses are formed into the film; latter due to the mismatch in the thermal expansion coefficient of the substrate and the grown film. Films under high residual stress may cause problems for further processing, and for device performance and reliability. High residual stress can induce film delamination or buckling; bend released structures or the materials where the films are attached. Especially in microelectromechanical system (MEMS) manufacturing, zero or well-controlled residual stress is desired, as the stress effect is more prominent on released structures. Here, the residual stress measured from most common metal oxides deposited by thermal ALD processes on silicon substrates are presented. The thermal processes have an advantage that those can be scaled up to batch processing to achieve through-put and cost efficiency required for volume production. By varying the process parameters (e.g. temperature, chemicals) we aim for zero stress films or film stacks as well as for comprehensive stress data set to help for example MEMS designers and process integrators choosing proper thin film material, and ALD process chemistry and process conditions.All films were grown in Picosun™ R-200 advanced reactors using thermal ALD processes. Deposited materials were HfO2, TiO2, SiO2, Al2O3 and Ta2O5 and combinations of these. The ALD temperature was varied between 150°C and 300°C. The substrates used were 150 mm diameter double side polished silicon wafers, which have been pre-measured for stresses before the ALD. For stress measurement we used TOHO FLX-2320-S wafer curvature measurement tool and the measurements were carried out at room temperature. Deposited film thicknesses were measured with Semilab SE-2000 ellipsometer.Residual stress data from most common metal oxides are presented. For some of the films there is also comparison for the same film material made with different precursors. In Figure 1 the residual stress data for the HfO2 film grown at varying temperature is presented. The stress changes from compressive to tensile as the ALD temperature was increased from 150°C to 200°C.

AB - When grown films by atomic layer deposition (ALD) both intrinsic and thermal stresses are formed into the film; latter due to the mismatch in the thermal expansion coefficient of the substrate and the grown film. Films under high residual stress may cause problems for further processing, and for device performance and reliability. High residual stress can induce film delamination or buckling; bend released structures or the materials where the films are attached. Especially in microelectromechanical system (MEMS) manufacturing, zero or well-controlled residual stress is desired, as the stress effect is more prominent on released structures. Here, the residual stress measured from most common metal oxides deposited by thermal ALD processes on silicon substrates are presented. The thermal processes have an advantage that those can be scaled up to batch processing to achieve through-put and cost efficiency required for volume production. By varying the process parameters (e.g. temperature, chemicals) we aim for zero stress films or film stacks as well as for comprehensive stress data set to help for example MEMS designers and process integrators choosing proper thin film material, and ALD process chemistry and process conditions.All films were grown in Picosun™ R-200 advanced reactors using thermal ALD processes. Deposited materials were HfO2, TiO2, SiO2, Al2O3 and Ta2O5 and combinations of these. The ALD temperature was varied between 150°C and 300°C. The substrates used were 150 mm diameter double side polished silicon wafers, which have been pre-measured for stresses before the ALD. For stress measurement we used TOHO FLX-2320-S wafer curvature measurement tool and the measurements were carried out at room temperature. Deposited film thicknesses were measured with Semilab SE-2000 ellipsometer.Residual stress data from most common metal oxides are presented. For some of the films there is also comparison for the same film material made with different precursors. In Figure 1 the residual stress data for the HfO2 film grown at varying temperature is presented. The stress changes from compressive to tensile as the ALD temperature was increased from 150°C to 200°C.

KW - ALD

KW - Atomic Layer Deposition

KW - residual stress

M3 - Conference Abstract

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ER -

Ritasalo R, Ylivaara O, Pilvi T, Suni T. Stresses in ALD films: Aiming for zero stress thin films. 2018. Abstract from 18th International Conference on Atomic Layer Deposition, ALD/ALE 2018, Incheon, Korea, Republic of.