Nanoindentation and Adhesion Properties of Ta Thin Films

Yuan-Tsung Chen

doi:10.1155/2013/154179

Abstract

Ta films were sputtered onto a glass substrate with thicknesses from 500 Å to 1500 Å under the following conditions: (a) as-deposited films were maintained at room temperature (RT), (b) films were postannealed atTA=150°C for 1 h, and (c) films were postannealed atTA=250°C for 1 h. X-ray diffraction (XRD) results revealed that the Ta films had a body-centered cubic (BCC) structure. Postannealing conditions and thicker Ta films exhibited a stronger Ta (110) crystallization than as-deposited and thinner films. The nanoindention results revealed that Ta thin films are sensitive to mean grain size, including a valuable hardness (H) and Young’s modulus (E). High nanomechanical properties of as-deposited and thinner films can be investigated by grain refinement, which is consistent with the Hall-Petch effect. The surface energy of as-deposited Ta films was higher than that in postannealing treatments. The adhesion of as-deposited Ta films was stronger than postannealing treatments because of crystalline degree effect. The maximalHandEand the optimal adhesion of an as-deposited 500-Å-thick Ta film were 15.6 GPa, 180 GPa, and 51.56 mJ/mm2, respectively, suggesting that a 500-Å-thick Ta thin film can be used in seed and protective layer applications.

Highlights

The study of Ta performance is noteworthy because it is a crucial material
The results indicate that the high nanomechanical properties of as-deposited and thinner films can be investigated by grain refinement, which is consistent with the Hall-Petch effect
The X-ray diffraction (XRD) structure and mean grain size show that strong crystallization and a large mean grain size occurred under the postannealing condition and thicker thickness

Summary

Introduction

Ta is generally inserted as a seed layer, buffer layer, capping layer, and protective layer in a multilayered structure, which can be used extensively in magnetoresistance random access memory (MRAM) and semiconductor applications [1,2,3,4,5] It is compatible with the semiconductor process and can be used as a predeposited layer on substrate or combined with other layers in the epitaxial system, such as Ta/CoCrPt, Ta/Co, and Ta/SiO2/Si systems [6,7,8]. Few studies have focused on the hardness, Young’s modulus, contact angle, surface energy, and adhesion properties of Ta thin films at room temperature (RT) and postannealing temperature conditions. These few studies only investigated about magnetic and electrical properties of Ta seed multilayered structure [2,3,4]. This indicates that adhesion of as-deposited Ta films was stronger than postannealing treatments because of crystalline degree effect

Experimental

Results and Discussion

Conclusion