Thermal Desorption Spectrometry as a Method of Analysis for Advanced Interconnect Materials

Abstract

In semiconductor manufacturing, the increasing demand for smaller, faster, and more powerful devices requires the introduction of novel materials for the fabrication of interconnects. In particular, the thermal stability of such materials and their chemical interaction with various processing conditions must be well understood to achieve a successful integration scheme. Thermal desorption spectrometry (TDS) is a powerful technique that provides quantitative and qualitative information on composition, structure, stability with regard to processing, storage and postdeposition treatments such as annealing and plasma etching [1–3]. Carbon-based aromatic polymers are promising as low–k interlayer dielectrics (ILD) [4]. However, such materials have weak mechanical properties, which can give rise to delamination during the chemical mechanical polishing (CMP) step. Also, due to the porous structure of the material, chemical species such as cleaning agents and metal diffusion barrier precursors may penetrate into the material during processing [5]. One possible solution is the creation of a dense surface sealing layer to improve the adhesion properties of the film and prevent the penetration of contaminants and moisture into the film [5]. Self-assembled monolayers (SAMs) are nanometer-scale organic films that have potentially various applications in very advanced BEoL integration schemes. Thiolate SAMs can be used as effective corrosion inhibitors of copper surfaces for applications such as wafer level packaging and wire bonding [6]. Silane SAMs could be used either to promote adhesion of diffusion barriers onto ILD materials [7] or used as diffusion barriers themselves [8]. In this short review the use of TDS for the characterization of new semiconductor materials for advanced BEoL technologies will be illustrated. Important integration issues such as the hydrophobic/hydrophilic character and surface sealing of low-k ILD materials modified by plasma treatments, the thermal stability of thiolate SAMs on Cu surfaces used as corrosion inhibitors, and the chemical labeling of silane SAMs for process monitoring will be discussed in this paper.