Nancy Iwamoto

Understanding modulus trends in ultra low K dielectric materials through the use of molecular modeling

Molecular modeling has previously been used to study adhesion and surface energy effects of die attach, underfill and viafill formulations, and is currently being used to study the mechanical property trends of the new class of ultra low k nanoporous dielectric materials, NANOGLASS/spl reg/ porous spin-on-glass (SOG) and GX3-P/sup TM/ porous organic, being developed within Honeywell. The need to understand material performance from a molecular level is especially understandable when considering the target application in IC fabrication. With such small microstructures, the impact of the molecular mechanical properties imparted by the molecular structure and architecture become more and more important. In addition, we are finding that by understanding the effects of the formulation on the mechanical properties from the molecular level, formulation changes can be planned directly targeted at specific properties. Although we are using many aspects of molecular modeling to help us understand SOG and organic dielectric properties such as density, wetting, solubility and adhesion, for this paper we have concentrated on reporting our observations on modulus. Our studies have found that we can correlate the experimental modulus of these materials very simply with a molecularly derived modulus.

Organosiloxane based bottom antireflective coating for 193nm lithography

A spin-on sacrificial 193 nm UV absorbing organosiloxane film was developed to facilitate ArF photoresist (PR) patterning. To improve lithographic compatibility with acrylate based photoresists, different performance additives were evaluated as photoresist adhesion promoter. The results suggested that the type and loading of the photoresist adhesion promoter had a large impact on the profile and focus latitude of the patterned photoresist features. An efficient photoresist adhesion promoter candidate was identified, which has minimum impact on other solution and film properties. This work has led to the development of DUO 193 organosiloxane based bottom anti-reflective coating. Application of this film as a blanket level bottom anti-reflective coating or as a fill material for via first trench last (VFTL) dual damascene patterning is possible. The SiO structure intrinsic to this film provides a high degree of plasma etch selectivity to the thin ArF photoresists in use today. Furthermore, an equivalent plasma etch rate between DUO 193 and the low dielectric constant SiOCH films used as the dielectric layer in the backend Cu interconnect structure is possible without compromising the photoresist etch selectivity. Equivalent etch rate is necessary for complete elimination of the “fencing” or “shell” defects found at the base of the etched trench feature located at the perimeter of the top of the via. Advanced ArF PR features of 100 nm in width (and smaller) have been routinely patterned on DUO 193 film. Via fill, plasma etch rate, wet etch rate, ArF PR patterning and shelf life data will be discussed in this presentation.

Multiscale perspectives of interface delamination in microelectronic packaging applications

With the increasing complexity and ongoing miniaturisation of microelectronic systems, reliability issues and their associated structural dimensions cross over from the microscale to the nanoscale. From this perspective, fracture of materials and material interfaces for microelectronic components is essentially a multiscale process. In this paper, interface delamination at the individual scales (atomistic, meso and micro) is considered, and specific analysis methods are discussed in order to compile understanding of contributions from each scale towards the macroscale response of an epoxy moulding compound. As will be addressed, the contributions from each scale can be applied to the next scale, and so the multiscale impact is derived sequentially rather than simultaneously in a single model. First, results on each scale are presented, considering the multilevel impact.

Modeling mechanical properties of an epoxy using particle dynamics, as parameterized through molecular modeling

Abstract The current paper successively applies molecular modeling and mesoscale modeling to scale mechanical models from an atomistic angstrom level to a sub-micron level and determine modulus, stress/strain behavior and defect formation in an epoxy and epoxy–copper interface. The results will show that molecular modeling may be applied directly to parameterize the bead properties used in the mesoscale model, which scale to the physical properties so could provide a means to understand interface behavior linked directly back to molecular origins.

Developing the stress–strain curve to failure using mesoscale models parameterized from molecular models

Abstract Developing the stress response using the molecular and mesoscale levels is fairly reliable during the initial strain. For instance, modulus is a property that can be established using these techniques and the continuity of scale between the molecular and mesoscale and agreement with experiment suggests that both may be used to establish modulus for parameterizing a macroscale model when measured properties are unavailable. However, the latter part of the stress–strain response that helps to establish ties to crack propagation still needs attention. One problem that was previously found in the mesoscale models was questionable lack of void formation in crosslinked systems due to superficially clean adhesive separation in the simulations. One way to overcome this lack of voiding was to determine how to develop bond breakage criterion that would allow surfaces to develop. This paper discusses development and application of bond breakage on a mesoscale level (which uses a bead-bond breakage criterion so does not explicitly define which bond is broken), and the impact on the simulated stress–strain curves using mesoscale models.

Advancing polymer process understanding in package and board applications through molecular modeling

In this paper we will discuss two molecular modeling methods which have been developed and applied at Honeywell to help predict material behavior from the process engineers standpoint. Both stress cycling and process analyses have been used to trend the probable behavior of material types in order to provide advanced intelligence on possible failure mechanisms. For instance, we have found that there are similarities in the response trends to strain and the number of cycles which suggests a link exists between the molecular-scale mechanism and engineering theories of reliability. That is, the cycling response on a molecular scale appears to be Coffin-Manson-like. On a similar scale, the molecular response of polymer chains to process stress induced either thermally or mechanically has shown to give insight to the response from actual processed parts.

Developing the mesoscale stress-strain curve to failure

Developing the stress response using the molecular and mesoscale levels is fairly reliable during the initial strain. For instance, modulus is a property that can be established using these techniques and the continuity of scale suggests that both may be used to establish modulus for parameterizing a macroscale model when measured properties are unavailable. However, the latter part of the stress/strain response that helps to establish ties to crack propagation still needs attention. One problem that was previously found was questionable lack of void formation in crosslinked systems due to superficially clean adhesive separation in the simulations. One way to overcome this lack of voiding was to determine how to develop bond breakage criterion that would allow surfaces to develop. This paper discusses development and application of bond breakage, and the impact on the simulated stress/strain curves using mesoscale models.

Mechanical properties of an epoxy modeled using particle dynamics, as parameterized through molecular modeling

The current paper applies both molecular modeling and mesoscale modeling to determine modulus and defect formation in epoxy and epoxy-copper interfaces. The results will show that molecular modeling may be applied directly to parameterize the bead properties used in the mesoscale model, which scale to the physical properties.

Performance properties in thick film silicate dielectric layers using molecular modeling

Molecular modeling was employed to understand various properties found in thick film dielectric layers derived from solution-based sol-gel formulation in order to aid their development. For instance, for formulations used as planarizing layers, it was discovered that during certain process steps ionic components could be introduced which greatly influences the extent of shrinkage by up to 50%, a phenomenon not normally seen in traditional spin-on glasses (SOG). Thermodynamic calculations showed that specific ionic contaminants contribute to the cure state of the material, potentially depolymerizing the material and promoting the formation of structures that are more easily deformed. Volumetric analysis and compaction modeling demonstrated that the high extent of shrinkage is expected, depending upon the final structure of the silicate. Calculation of the relative modulus of the different suspected structures also showed that depolymerized structures contribute to the ease of compaction.

Molecularly derived mesoscale modeling of an epoxy/Cu interface: Interface roughness

Abstract This paper addresses use of coarse-grained mesoscale model to look at angle dependencies in an epoxy–copper (I) oxide interface in order to understand roughness effects on adhesion. The parameterizations of the coarse-grained beads were previously calculated from the molecular level [1] , [2] , [3] for the same polymer and copper oxide interface. Roughness was investigated in two ways: applying a zigzag interface to the interface separation simulation, and separating the interface using differing angles. When compared, both methods reduce to the similar energy trends. In addition, the effect moisture on the interface was compared for the rough and smooth interfaces.