Diffusion phenomena in chemically stabilized multilayer structures

S. Bruijn

Research output: ThesisPhD Thesis - Research external, graduation UTAcademic

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Abstract

Multilayered thin film structures are widely applied as reflective coatings for optical elements in the extreme ultraviolet wavelength regime. In this thesis we investigate the structural and chemical changes that occur in Mo/Si based multilayers as a result of radiation induced thermal loads and other heating schemes. This thesis addresses thermally induced diffusion in such multilayers, focussing on reaction mechanisms at the interfaces and how these are modified in the presence of a diffusion barrier layer. To allow these studies, a new, in-situ X-ray diffraction method is introduced to analyse diffusion induced interface growth and measure diffusion speeds in Mo/Si multilayers during thermal annealing. This method can determine the change in the interface thickness at picometer accuracy. Because of this high accuracy it is possible to study diffusion at relatively low temperatures. A diffusion-reaction model was developed to describe the interface growth. The diffusion in multilayers is shown to be dependent on the structure of all the layers as well as on the chemical interactions with barrier layer materials. In particular, the crystallinity of the Mo layer (crystalline or quasi-amorphous) has a large influence on the diffusion speed. The structure and density of the B4C diffusion barrier layers have a large influence on the diffusion coefficient. Furthermore it is shown that B4C also forms molybdenum boride compounds during annealing, which reduce the diffusion rate. In conclusion, the diffusion properties of thin film multilayer structures are determined by both the structure and the chemical interactions of the individual (barrier-)layers. The damage mechanisms of these layered structures by intense femtosecond pulses are also investigated, to find a possible difference in damage mechanism between continuous heat loads and ultrafast pulsed heat loads. This investigation was performed on MoN/SiN multilayers. We find that the damage mechanisms for annealing and pulsed irradiation are fundamentally the same. In both cases, the MoN layer dissociates and N2 gas is released, which subsequently forms bubbles in the MoN layer which may lead to delamination.
Original languageEnglish
Awarding Institution
  • University of Twente
Supervisors/Advisors
  • Bijkerk, Fred, Supervisor
  • van de Kruijs, Robbert W.E., Supervisor
Award date27 Apr 2011
Place of PublicationEnschede
Publisher
Print ISBNs978-94-91211-22-5
Publication statusPublished - 27 Apr 2011

Fingerprint

laminates
barrier layers
theses
damage
annealing
heat
borides
thin films
molybdenum
crystallinity
bubbles
diffusion coefficient
interactions
coatings
irradiation
heating
radiation
pulses

Keywords

  • METIS-284438
  • IR-76952

Cite this

Bruijn, S. (2011). Diffusion phenomena in chemically stabilized multilayer structures. Enschede: University of Twente.
Bruijn, S.. / Diffusion phenomena in chemically stabilized multilayer structures. Enschede : University of Twente, 2011. 114 p.
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Bruijn, S 2011, 'Diffusion phenomena in chemically stabilized multilayer structures', University of Twente, Enschede.

Diffusion phenomena in chemically stabilized multilayer structures. / Bruijn, S.

Enschede : University of Twente, 2011. 114 p.

Research output: ThesisPhD Thesis - Research external, graduation UTAcademic

TY - THES

T1 - Diffusion phenomena in chemically stabilized multilayer structures

AU - Bruijn, S.

PY - 2011/4/27

Y1 - 2011/4/27

N2 - Multilayered thin film structures are widely applied as reflective coatings for optical elements in the extreme ultraviolet wavelength regime. In this thesis we investigate the structural and chemical changes that occur in Mo/Si based multilayers as a result of radiation induced thermal loads and other heating schemes. This thesis addresses thermally induced diffusion in such multilayers, focussing on reaction mechanisms at the interfaces and how these are modified in the presence of a diffusion barrier layer. To allow these studies, a new, in-situ X-ray diffraction method is introduced to analyse diffusion induced interface growth and measure diffusion speeds in Mo/Si multilayers during thermal annealing. This method can determine the change in the interface thickness at picometer accuracy. Because of this high accuracy it is possible to study diffusion at relatively low temperatures. A diffusion-reaction model was developed to describe the interface growth. The diffusion in multilayers is shown to be dependent on the structure of all the layers as well as on the chemical interactions with barrier layer materials. In particular, the crystallinity of the Mo layer (crystalline or quasi-amorphous) has a large influence on the diffusion speed. The structure and density of the B4C diffusion barrier layers have a large influence on the diffusion coefficient. Furthermore it is shown that B4C also forms molybdenum boride compounds during annealing, which reduce the diffusion rate. In conclusion, the diffusion properties of thin film multilayer structures are determined by both the structure and the chemical interactions of the individual (barrier-)layers. The damage mechanisms of these layered structures by intense femtosecond pulses are also investigated, to find a possible difference in damage mechanism between continuous heat loads and ultrafast pulsed heat loads. This investigation was performed on MoN/SiN multilayers. We find that the damage mechanisms for annealing and pulsed irradiation are fundamentally the same. In both cases, the MoN layer dissociates and N2 gas is released, which subsequently forms bubbles in the MoN layer which may lead to delamination.

AB - Multilayered thin film structures are widely applied as reflective coatings for optical elements in the extreme ultraviolet wavelength regime. In this thesis we investigate the structural and chemical changes that occur in Mo/Si based multilayers as a result of radiation induced thermal loads and other heating schemes. This thesis addresses thermally induced diffusion in such multilayers, focussing on reaction mechanisms at the interfaces and how these are modified in the presence of a diffusion barrier layer. To allow these studies, a new, in-situ X-ray diffraction method is introduced to analyse diffusion induced interface growth and measure diffusion speeds in Mo/Si multilayers during thermal annealing. This method can determine the change in the interface thickness at picometer accuracy. Because of this high accuracy it is possible to study diffusion at relatively low temperatures. A diffusion-reaction model was developed to describe the interface growth. The diffusion in multilayers is shown to be dependent on the structure of all the layers as well as on the chemical interactions with barrier layer materials. In particular, the crystallinity of the Mo layer (crystalline or quasi-amorphous) has a large influence on the diffusion speed. The structure and density of the B4C diffusion barrier layers have a large influence on the diffusion coefficient. Furthermore it is shown that B4C also forms molybdenum boride compounds during annealing, which reduce the diffusion rate. In conclusion, the diffusion properties of thin film multilayer structures are determined by both the structure and the chemical interactions of the individual (barrier-)layers. The damage mechanisms of these layered structures by intense femtosecond pulses are also investigated, to find a possible difference in damage mechanism between continuous heat loads and ultrafast pulsed heat loads. This investigation was performed on MoN/SiN multilayers. We find that the damage mechanisms for annealing and pulsed irradiation are fundamentally the same. In both cases, the MoN layer dissociates and N2 gas is released, which subsequently forms bubbles in the MoN layer which may lead to delamination.

KW - METIS-284438

KW - IR-76952

M3 - PhD Thesis - Research external, graduation UT

SN - 978-94-91211-22-5

PB - University of Twente

CY - Enschede

ER -

Bruijn S. Diffusion phenomena in chemically stabilized multilayer structures. Enschede: University of Twente, 2011. 114 p.