Titanium Oxide Adhesion Layer for High Temperature Annealed Si/Si3N4/TiOx/Pt/LiCoO2 Battery Structures

• Published in: Journal of electronic materials Vol. 45; no. 2; pp. 910 - 916
• Main Authors: Vieira, E. M. F., Ribeiro, J. F., Sousa, R., Silva, M. M., Dupont, L., Gonçalves, L. M.
• Format: Journal Article
• Language: English
• Published: New York Springer US 2016; Institute of Electrical and Electronics Engineers
• Subjects: Characterization and Evaluation of Materials; Chemical Sciences; Chemistry and Materials Science; Electronics and Microelectronics; Instrumentation; Material chemistry; Materials Science; Optical and Electronic Materials; Solid State Physics; adhesion layer; platinum; ToF-SIMS; titanium oxide; high temperature; Li-microbatteries
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-015-4223-5

This work describes the influence of a high annealing temperature of about 700°C on the Si(substrate)/Si 3 N 4 /TiO x /Pt/LiCoO 2 multilayer system for the fabrication of all-solid-state lithium ion thin film microbatteries. Such micro-batteries typically utilize lithium cobalt oxide (LiCoO 2 ) as cathode material with a platinum (Pt) current collector. Silicon nitride (Si 3 N 4 ) is used to act as a barrier against Li diffusion into the substrate. For a good adherence between Si 3 N 4 and Pt, commonly titanium (Ti) is used as intermediate layer. However, to achieve crystalline LiCoO 2 the multilayer system has to be annealed at high temperature. This post-treatment initiates Ti diffusion into the Pt-collector and an oxidation to TiO x , leading to volume expansion and adhesion failures. To solve this adhesion problem, we introduce titanium oxide (TiO x ) as an adhesion layer, avoiding the diffusion during the annealing process. LiCoO 2 , Pt and Si 3 N 4 layers were deposited by magnetron sputtering and the TiO x layer by thermal oxidation of Ti layers deposited by e-beam technique. As-deposited and annealed multilayer systems using various TiO x layer thicknesses were studied by scanning electron microscopy (SEM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) and x-ray photoelectron spectroscopy (XPS). The results revealed that an annealing process at temperature of 700°C leads to different interactions of Ti atoms between the layers, for various TiO x layer thicknesses (25–45 nm).