Determining Contact Angle and Surface Energy of Co60Fe20B20Thin Films by Magnetron Sputtering

S K Wang,S R Jian,Yuan-Tsung Chen

doi:10.1155/2011/291935

Abstract

This study examined the deposition of CoFeB thin films on a glass substrate at room temperature (RT), as well as the effects of conducting postannealing at heat annealingTA=150°C for 1 h. The thickness (tf) of the CoFeB thin films ranged from 100 Å to 500 Å. The microstructure, average contact angle, and surface energy properties were also investigated. X-ray diffraction (XRD) revealed that CoFeB films are nanocrystalline at RT and that post-annealing treatment increases in conjunction with the crystallinity. The surface energy of the CoFeB thin films is related to adhesive strength. The CoFeB films form a contact angle of larger than90∘with water as a test liquid. This finding demonstrates that the CoFeB film is hydrophobic. Astfincreases from 100 Å to 500 Å, the surface energy at RT decreases from 40 mJ/mm2to 32 mJ/mm2. During post-annealing treatment, the surface energy increases from 32 mJ/mm2to 35 mJ/mm2, astfincreases from 100 Å to 300 Å; then it decreases to 31 mJ/mm2, astfincreases from 300 Å to 500 Å. The surface energy of the as-deposited CoFeB thin films exceeds that during post-annealing treatment at thicknesses of 100 Å and 200 Å, suggesting that as-deposited CoFeB thin film increases the adhesion.

Highlights

The performance of magnetic tunnel junctions (MTJs) is critical to nonvolatile magnetoresistive random access memory (MRAM), magnetic read heads, and sensor industries [1–5]
The magnetic CoFeB thin film is inserted into the MTJ junction, which is compatible with the semiconductor process
This study examined the contact angle, microstructure, and surface energy properties of typical CoFeB films using X-ray diffraction (XRD) and contact angle measurements

Summary

Introduction

The performance of magnetic tunnel junctions (MTJs) is critical to nonvolatile magnetoresistive random access memory (MRAM), magnetic read heads, and sensor industries [1–5]. Investigations of the adhesive properties of CoFeB thin films in memory devices have been few. The amorphous CoFeB free layer of MTJ can induce a high tunneling magnetoresistance (TMR) ratio at RT [6]. The amorphous CoFeB free layer of MTJ can enhance a significantly higher TMR ratio during postannealing TA = 150◦C treatment [7–9]. Few previous studies have focused on the contact angle, surface energy, or adhesion properties of CoFeB thin films at RT, and they have not examined postannealing treatments adequately. Investigating such properties of CoFeB thin films is worthwhile. The XRD results indicate that CoFeB thin films exhibit a body-centered cubic (BCC) structure

Experimental Details

Results and Discussion

Conclusions