Characterization of Nano-Scale Protective Oxide Films: Application on Metal Chemical Mechanical Planarization

Abstract

This study focuses on the characterization of nano-scale metal oxide films for chemical mechanical planarization (CMP) applications. The protective nature of the self-grown metal oxide layers in the CMP slurry environment enable topographic selectivity required for metallization of interconnects. Tungsten was selected as the model metal film to study the formation and characteristics of the metal oxide nano-layers since tungsten CMP is very well-established in conventional semiconductor manufacturing. The tungsten oxide nano-films were characterized for thickness, density and surface topography in addition to evaluation of their protective nature by calculation of the Pilling-Bedworth (P-B) ratios. It was observed that in addition to controlling the self-protective characteristics, the oxidizer concentration also affects the surface structure of the metal oxide films resulting in significant changes in the CMP process performance in terms of material removal rates and surface finish with a sweet-spot detected at 0. Nano-scale protective metal oxides are foreseen to have wide applications in advanced materials science and technology including microelectronics and biomaterials applications in addition to their conventional utilizations in corrosion prevention and coatings. Particularly in semiconductor manufacturing, controlled growth of thin films and inherent stress development within the film and film/substrate interface are very critical to enable the future material demands. Metal oxide thin films can be used as an interfacial layer to improve the adhesion of polymeric substances in chip packaging, as nano-films with inherent self-growth limiting capability for bottom-up microelectronics manufacturing or as a subtractive layer to achieve controlled material removal rates and minimum defectivity in chemical mechanical planarization (CMP) applications. CMP is the process of choice for planarization of metal and dielectric surfaces to enable precise photolithography and multilevel metallization in microelectronics manufacturing.1 Introduction of new automotive, medical and implantable devices challenge the needs to improve microelectronic device performances to meet aggressive targets on cost reduction, zero defectivity and enhanced reliability, which consecutively impact CMP process performance requirements.2 Although mainstream semiconductor engineering could involve tradeoffs between performance and reliability, these new applications enforce the assessment of new materials while dealing with limited margins requiring advances in processing, materials science and chemistry.3 The main objective of this paper is to characterize the self-protective oxide films grown on the metal surfaces in the presence of an oxidizing environment to be able to utilize them in advanced microelectronics manufacturing applications, predominantly focusing on CMP.When characterizing the durability of thin film interfaces, a critical thickness is defined above which it is thermodynamically favorable for the film to partially or fully...

A Fundamental Approach to Electrochemical Analyses on Chemically Modified Thin Films for Barrier CMP Optimization

“…20 Furthermore, the surface oxide structures and the roughness correlate to the CMP removal rate and defectivity performance. 17 The passive film formation was confirmed by the X-Ray Reflectivity measurements and the Pilling-Bedworth ratio calculations. The AFM images taken on the passivated W surfaces align with the proposed nucleation and growth mechanisms as it is further discussed in the next section.…”

“…In earlier studies, we have demonstrated the formation of tungsten oxide and titanium oxide passive films and their effects on surface energy and topography for the CMP applications. 17,18 Here, we extend these analyses to W, Ti and TiN layers to investigate their corrosion behavior and passivation characteristics as a function of H 2 O 2 (oxidizer) concentration. Electrochemical analyses indicate that the higher is the oxidizer concentration, the faster is the rate of passivation, which is further related to the increase in the material removal rates (MRR).…”

Surface morphology analysis of oxide layers formed on 10CrMo9-10 steel used in the power industry

“…It was found that stresses depend both on the metal and oxide volume, on their crystalline structures, as well as on the mechanism of oxide growth. When the oxide forms on the metal/oxide joint, the volume change due to the oxide formation can be expressed by means of Pilling-Bedworth (PBR) relationship (1) [3][4][5][6].…”

“…The obtained results of studies show that the fractal analysis results are affected by operational parameters and by the type of formed oxide layers. Kargoz et al [5] concentrated on studying nanoscale metal oxide films used for chemical mechanical planarization (CMP) applications. The studies were carried out on thin metal oxide layers formed chemically from tungsten in the environment of a CMP suspension.…”

“…Tungsten oxides were characterised in terms of thickness, density and surface topography. It was found that the topography of tungsten wafers' surface tends to change depending on the oxidising agent concentration and it was also found to affect the wettability, total surface energy and consequently the material removal rate and the surface quality responses [5]. The examination of materials' surface topography is one of main tests used to study the surface layers.…”