Magnesium Oxide Tunneling Current and Ferromagnetic Film Characterization

Abstract

Magnetic Tunnel Junctions are a very promising technology with the potential to replace numerous forms of computer memory a well as a wide range of other applications. Three novel studies are done demonstrating various aspects of MTJ design and manufacturing showing their importance in understanding device performance. First, a Vibrating Sample Magnetometer (VSM) study comparing Co40Fe40B20 and Co20Fe60B20 films of varying thicknesses between 0.6 nm and 3.2 nm is reported. Greater iron content is shown to increase the overall magnetic moment of the samples. Second, a Current in Plane Tunneling (CIPT) study is done showing the dependence Magnetoresistance (MR) has on the thickness of the MTJ free layer and the crystallinity of the active region of devices. A full MTJ device stack is developed, with free layer thicknesses from 0.6-1.75 nm and 1.5-3.3 nm creating a wedge profile on each sample wafer. CIPT shows a significant increase to MR with anneal, verifying the presence of the [001] crystal structure in post anneal samples using TEM. Third, Ta/Co40Fe40B20/MgO/Co40Fe40B20/Ta thin film metal-insulator-metal capacitors were developed to measure the tunneling effect and how it changes as a result of MgO thickness and CoFeB crystallinity. Devices were designed with: varied MgO thickness from 0.5 nm to 2 nm thick, with pre and post anneal CoFeB. Current-Voltage data was collected and device resistance was found to have a linear dependence on MgO thickness in the post anneal CoFeB/MgO/CoFeB samples. The uniformity of the IV data indicates potential for use monitoring devices during MTJ manufacturing.