Jeff Bielefeld

Valence band offset at the amorphous hydrogenated boron nitride-silicon (100) interface

In order to understand the fundamental behavior of various boron nitride heterostructure devices, we have utilized x-ray photoelectron spectroscopy to determine the valence band offset (VBO) present at interfaces formed by plasma enhanced chemical vapor deposition of hexagonal amorphous hydrogenated boron nitride (a-BN:H) on Si (100) substrates. For an a-BN:H/Si interface with some interfacial SiNx and SiBx bonding, we determined the valence band offset to be 1.9 ± 0.15 eV. The conduction band offset was likewise determined to be 2.2 ± 0.2 eV with a type I alignment.

Toughening Thin‐Film Structures with Ceramic‐Like Amorphous Silicon Carbide Films

A significant improvement of adhesion in thin-film structures is demonstrated using embedded ceramic-like amorphous silicon carbide films (a-SiC:H films). a-SiC:H films exhibit plasticity at the nanoscale and outstanding chemical and thermal stability unlike most materials. The multi-functionality and the ease of processing of the films have potential to offer a new toughening strategy for reliability of nanoscale device structures.

Nondestructive in Situ Characterization of Molecular Structures at the Surface and Buried Interface of Silicon-Supported Low-k Dielectric Films

As low-k dielectric/copper interconnects continue to scale down in size, the interfaces of low-k dielectric materials will increasingly determine the structure and properties of the materials. We report an in situ nondestructive characterization method to characterize the molecular structure at the surface and buried interface of silicon-supported low-k dielectric thin films using interface sensitive infrared-visible sum frequency generation vibrational spectroscopy (SFG). Film thickness-dependent reflected SFG signals were observed, which were explained by multiple reflections of the input and SFG beams within the low-k film. The effect of multiple reflections on the SFG signal was determined by incorporating thin-film interference into the local field factors at the low-k/air and Si/low-k interfaces. Simulated thickness-dependent SFG spectra were then used to deduce the relative contributions of the low-k/air and low-k/Si interfaces to the detected SFG signal. The nonlinear susceptibilities at each interface, which are directly related to the interfacial molecular structure, were then deduced from the isolated interfacial contributions to the detected SFG signal. The method developed here is general and demonstrates that SFG measurements can be integrated into other modern analytical and microfabrication methods that utilize silicon-based substrates. Therefore, the molecular structure at the surface and buried interface of thin polymer or organic films deposited on silicon substrates can be measured in the same experimental geometry used to measure many optical, electrical, and mechanical properties.

Valence and conduction band offsets at amorphous hexagonal boron nitride interfaces with silicon network dielectrics

To facilitate the design of heterostructure devices employing hexagonal/sp2 boron nitride, x-ray photoelectron spectroscopy has been utilized in conjunction with prior reflection electron energy loss spectroscopy measurements to determine the valence and conduction band offsets (VBOs and CBOs) present at interfaces formed between amorphous hydrogenated sp2 boron nitride (a-BN:H) and various low- and high-dielectric-constant (k) amorphous hydrogenated silicon network dielectric materials (a-SiX:H, X = O, N, C). For a-BN:H interfaces formed with wide-band-gap a-SiO2 and low-k a-SiOC:H materials (Eg ≅ 8.2−8.8 eV), a type I band alignment was observed where the a-BN:H band gap (Eg = 5.5 ± 0.2 eV) was bracketed by a relatively large VBO and CBO of ∼1.9 and 1.2 eV, respectively. Similarly, a type I alignment was observed between a-BN:H and high-k a-SiC:H where the a-SiC:H band gap (Eg = 2.6 ± 0.2 eV) was bracketed by a-BN:H with VBO and CBO of 1.0 ± 0.1 and 1.9 ± 0.2 eV, respectively. The addition of O or N to ...

Mechanical property changes in porous low-k dielectric thin films during processing

The design of future generations of Cu-low-k dielectric interconnects with reduced electronic crosstalk often requires engineering materials with an optimal trade off between their dielectric constant and elastic modulus. This is because the benefits associated with the reduction of the dielectric constant by increasing the porosity of materials, for example, can adversely affect their mechanical integrity during processing. By using load-dependent contact-resonance atomic force microscopy, the changes in the elastic modulus of low-k dielectric materials due to processing were accurately measured. These changes were linked to alterations sustained by the structure of low-k dielectric films during processing. A two-phase model was used for quantitative assessments of the elastic modulus changes undergone by the organosilicate skeleton of the structure of porous and pore-filled dielectrics.

Mechanical properties of hydrogenated amorphous silicon carbide thin films

The reliable fabrication of interconnects containing ultra low-k organosilicate dielectrics (ULK) has been a significant technological challenge. ULKs are inherently fragile with reduced elastic constants. In addition, their Si-O backbone makes organosilicate films prone to moisture-assisted cracking leading to serious reliability concerns. In this study, we investigated the mechanical properties of hydrogenated amorphous silicon carbide films (a-SiC:H) that do not contain Si-O bonds. The mechanical properties of a-SiC:H films are considered together with their enhanced fracture resistance and remarkable insensitivity to moisture assisted cracking.

Ordered porosity for interconnect applications

To lower interconnect signal delay, the industry continues to work on the integration of low-k interlayer dielectrics (ILD). Porosity is often added to further reduce dielectric constant and significantly impact capacitance. These porous dielectric films are most commonly deposited via Chemical Vapor Deposition (CVD), delivering a random order to the pore structure. Disordered films suffer from a reduction in mechanical properties, which ultimately limits the maximum porosity obtained due to film collapse. Control of porosity, pore size distribution and pore geometry is needed to extend the porosity beyond conventional percolation thresholds. Here we present the case study of a periodic mesoporous organosilica (PMO) film. We optimize solution processing to obtain an ordered film and characterize the film porosity, pore size distribution, geometry and mechanical properties. The PMO film is tested in both a dual damascene and replacement back end integration flow.