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Fracture of nanoporous organosilicat...

Gage, David Maxwell.

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Fracture of nanoporous organosilicate thin films.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Fracture of nanoporous organosilicate thin films./
Author:	Gage, David Maxwell.
Description:	157 p.
Notes:	Adviser: Reinhold H. Dauskardt.
Contained By:	Dissertation Abstracts International69-05B.
Subject:	Applied Mechanics. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3313571
ISBN:	9780549624325

Fracture of nanoporous organosilicate thin films.
Gage, David Maxwell.

Fracture of nanoporous organosilicate thin films. - 157 p.

Adviser: Reinhold H. Dauskardt.

Thesis (Ph.D.)--Stanford University, 2008.

Nanoporous organosilicate thin films are attractive candidates for a number of emerging technologies, ranging from biotechnology to optics and microelectronics. However, integration of these materials is challenged by their fragile nature and susceptibility to mechanical failure. Debonding and cohesive cracking of the organosilicate film are principal concerns that threaten the reliability and yield of device structures. Despite the intense interest in these materials, there is currently a need for greater understanding of the relationship between glass structure and thermomechanical integrity. The objective of this research was to investigate strategies for improving mechanical performance through variations in film chemistry, process conditions, and pore morphology. Several approaches to effecting improvements in elastic and fracture properties were examined in depth, including post-deposition curing, molecular reinforcement using hydrocarbon network groups, and manipulation of pore size and architecture. Detailed structural characterization was employed along with quantitative fracture mechanics based testing methods.

ISBN: 9780549624325Subjects--Topical Terms:

1018410
Applied Mechanics.

Fracture of nanoporous organosilicate thin films.
LDR:05809nam 2200313 a 45 001 947461
005 20110524
008 110524s2008 eng d
020 $a 9780549624325
035 $a (UMI)AAI3313571
035 $a AAI3313571
040 $a UMI $c UMI
100 1 $a Gage, David Maxwell. $3 1270930
245 1 0 $a Fracture of nanoporous organosilicate thin films.
300 $a 157 p.
500 $a Adviser: Reinhold H. Dauskardt.
500 $a Source: Dissertation Abstracts International, Volume: 69-05, Section: B, page: 3215.
502 $a Thesis (Ph.D.)--Stanford University, 2008.
520 $a Nanoporous organosilicate thin films are attractive candidates for a number of emerging technologies, ranging from biotechnology to optics and microelectronics. However, integration of these materials is challenged by their fragile nature and susceptibility to mechanical failure. Debonding and cohesive cracking of the organosilicate film are principal concerns that threaten the reliability and yield of device structures. Despite the intense interest in these materials, there is currently a need for greater understanding of the relationship between glass structure and thermomechanical integrity. The objective of this research was to investigate strategies for improving mechanical performance through variations in film chemistry, process conditions, and pore morphology. Several approaches to effecting improvements in elastic and fracture properties were examined in depth, including post-deposition curing, molecular reinforcement using hydrocarbon network groups, and manipulation of pore size and architecture. Detailed structural characterization was employed along with quantitative fracture mechanics based testing methods.
520 $a It was shown that ultra-violet irradiation and electron bombardment post-deposition treatments can significantly impact glass structure in ways that cannot be achieved through thermal activation alone. Both techniques demonstrated high porogen removal efficiency and enhanced the glass matrix through increased network connectivity and local bond rearrangements. The increases in network connectivity were achieved predominantly through the replacement of terminal groups, particularly methyl and silanol groups, with Si-O network bonds. Nuclear magnetic resonance spectroscopy was shown to be a powerful and quantitative method for gaining new insight into the underlying cure reactions and mechanisms. It was demonstrated that curing leads to significant progressive enhancement of elastic modulus and adhesive fracture energies due to increased network bond density that results from higher network connectivity along with slight densification of the film. At the same time, the curing produced only a modest progressive increase in dielectric constant, indicating that ultra-violet and electron beam curing show great promise for the processing of low-k and ultra low-k organosilicate films. However, some general limitations of the curing processes were also discovered. In particular, the cohesive fracture energies of organosilicate films were found to be largely insensitive to curing. This was shown to be due to a crack meandering phenomenon in which the crack undergoes small-scale deflections toward local regions of free volume and reduced network bond density, thereby mitigating the effects of curing. Additionally, neither ultra-violet nor electron-beam curing were successful at improving adhesion at the lower film to barrier interface, suggesting little or no curing effects at the bottom portion of the dielectric layer.
520 $a Sol-gel condensation of carbon-bridged organosilanes was used to prepare low-k films that feature hydrocarbon network bonds in lieu of terminal organic substituents. The hydrocarbon ligaments served to preserve connectivity and reinforce the glass network, resulting in remarkable improvements in elastic modulus and fracture resistance relative to competing carbon-doped oxides or SSQ derived materials of the same dielectric constant. The improvements in fracture resistance were rationalized in terms of a bridging contribution during stretching and rupture of the hydrocarbon chains that was found to scale with the length of the bridging hydrocarbon group. Additionally, the Si-C bonds in the bridged organosilicates made these films less prone to moisture assisted cracking than their silica-based and SSQ counterparts. The bridged organosilicate films demonstrated outstanding mechanical properties even at high porosity, making them excellent candidates for ultra low-k porous applications.
520 $a The impact of pore morphology on the fracture of nanoporous films was also examined. For a given pore generating scheme, increasing porous volume was found to have a considerable deleterious effect on elastic modulus and adhesive and cohesive fracture resistance. However, it was demonstrated that, for a given porous volume, alterations in pore size distribution can significantly affect fracture properties. Different pore generating molecules were used to achieve a range of pore sizes for a given porous volume. It was found that decreasing pore size produced a more fracture resistant film, which was rationalized in terms of the capacity for larger pores to act as flaws that reduce film strength. Although it was shown that the effects of pore size were likely convoluted to a certain extent with considerations of pore organization and porosity grading, the work underscores the importance of porogen selection.
590 $a School code: 0212.
650 4 $a Applied Mechanics. $3 1018410
650 4 $a Engineering, Materials Science. $3 1017759
690 $a 0346
690 $a 0794
710 2 0 $a Stanford University. $3 754827
773 0 $t Dissertation Abstracts International $g 69-05B.
790 $a 0212
790 1 0 $a Dauskardt, Reinhold H., $e advisor
791 $a Ph.D.
792 $a 2008
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3313571