Grazing-incidence small-angle X-ray scattering study of porous dielectrics used in advanced microelectronic interconnections

Abstract

The increase of the integration density and of the operation speed in ultra‐large‐scale integrated microelectronics requires a reduction in the dielectric constant for high‐frequency insulation between the copper connections of some tenth‐of‐micrometre thickness. Recently, the quality of the dielectric has been defined by its dielectric constant k (>1) relative to the unpolarized vacuum (k = 1). Bulk low k will never reach k lower than 3 and the only way to achieve a further decrease in k is to introduce nanoporous dielectric films compatible with the required mechanical behaviour. We compare the merits and the structure determined by grazing‐incidence small‐angle X‐ray scattering (GISAXS) of four different growth processes: plasma‐enhanced chemical vapour deposition or spin coating with three variants: dual‐phase blend, self‐assembled approach, nanoclustering precursor. All of them are baked in order to cure the amorphous SiwOxCyHz `skeleton' (SiOCH). Depending on the process used, the pore morphologies are very different. They range from well defined pores of 4–5 nm diameter to sub‐nanometric ill‐defined pores which may be described as density fluctuations. Finally, it appears that the curing process is a key problem, which up to now has been difficult to characterize by GISAXS.

Probing surface and interface morphology with Grazing Incidence Small Angle X-Ray Scattering

“…To complement GISAXS experiments, X-ray reflectivity measurements have been performed to characterize the surface morphology and the porous-Si/Si interface roughness generated by the pore front propagation. Simon et al [299] compared GISAXS measurements on nanoporous low-k materials obtained by different routes. They showed that the pore morphology was drastically affected by the process used, ranging from well-defined pore sizes and shapes to ill-defined pores.…”

“…Spin coating and PECVD techniques have been proposed to fabricate pores of nanometric size compatible with the Cu interconnections [299]. In all cases, the SiOCH matrix is mixed with a porogen (organic molecule) removed by a thermal treatment.…”

Enhanced Mechanical and Electrochemical Performances of Silica-Based Coatings Obtained by Electrophoretic Deposition

“…7,8 The compact films adhere tightly to various substrates with low porosity; nevertheless, it is unsuitable for low dielectric or thermal insulation materials. 9 Electrochemical corrosion-thermal oxidation is a common method for preparing porous SiO 2 insulating films. 10 Kan et al 11 fabricated a thick SiO 2 coating with a porosity of 55−75% from macroporous Si (macro-PS) by electrochemical etching from p-type Si, followed by wet oxidation at 1050 °C; however, the temperature was too high and the fabrication process was relatively complex to be controlled effectively.…”

Anomalous grazing incidence small-angle X-ray scattering of carbon-encapsulated Au and Cu clusters

“…However, for many applications in the field of nanotechnology, conventional SAXS performed in transmission geometry suffers from a lack of surface sensitivity. Therefore, grazing incidence SAXS (GISAXS) is in rapid expansion for the characterization of, for example, semiconductor dots (Schmidbauer et al, 1998;Rauscher et al, 1999), metallic islands (Levine et al, 1989;Renaud et al, 2003), implanted materials (Cattaruzza et al, 2000;Babonneau et al, 2006Babonneau et al, , 2007, nanoporous dielectrics (Lee, Park et al, 2005;Simon et al, 2007) and nanocomposite films (Gibaud et al, 2001;Babonneau et al, 2005). GISAXS also generally needs SR since both a small beam size and a high flux are required and, in principle, it can be used in combination with the anomalous technique (AGISAXS).…”