Breakthrough in current-in-plane tunneling measurement precision by application of multi-variable fitting algorithm.

Alberto Cagliani,Lior Shiv,Peter F Nielsen,Dirch H Petersen,Ole Hansen,Frederik W Østerberg

doi:10.1063/1.4989994

Alberto Cagliani, Lior Shiv + Show 4 more

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https://doi.org/10.1063/1.4989994

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Abstract

We present a breakthrough in micro-four-point probe (M4PP) metrology to substantially improve precision of transmission line (transfer length) type measurements by application of advanced electrode position correction. In particular, we demonstrate this methodology for the M4PP current-in-plane tunneling (CIPT) technique. The CIPT method has been a crucial tool in the development of magnetic tunnel junction (MTJ) stacks suitable for magnetic random-access memories for more than a decade. On two MTJ stacks, the measurement precision of resistance-area product and tunneling magnetoresistance was improved by up to a factor of 3.5 and the measurement reproducibility by up to a factor of 17, thanks to our improved position correction technique.

Highlights

M4PP has proven useful for characterization of layered structures where the characteristic length scale that describes the current flow is comparable to the inter-probe distances, such as the current-in-plane tunneling (CIPT) method for magnetic tunnel junction (MTJ) stacks7 and junction leakage measurements,8 both relying on the principles first described by Severin9 and Vu
For a single conductive sheet, this dominant source of geometrical measurement error can be eliminated by van der Pauw type position correction,3,11 where the four-point resistance is measured in two electrode configurations and the sheet resistance is found independent of the electrode positions assuming the electrodes are placed on a straight line, i.e., correcting for in-line position errors
In the 100 yr history of four-point probe measurements, all the proposed methods for electrode position correction have been based on different van der Pauw type corrections, but in this work we present a novel concept that solves the problem for length scale dependent samples that are not a single conductive sheet

Summary

INTRODUCTION

Four-point probe (4PP) electrical characterization of thin films has been used for decades in industry and research. The introduction of micro-four-point probe’s (M4PP’s) opened the possibility of characterizing thin films with submm lateral dimensions and performing resistance mapping with high spatial resolution. The miniaturization of 4PP’s has enabled development of new metrology methods such as the micro-Hall effect for characterization of carrier density and mobility without lithographically defined Hall structures. In addition, M4PP has proven useful for characterization of layered structures where the characteristic length scale that describes the current flow is comparable to the inter-probe distances, such as the current-in-plane tunneling (CIPT) method for magnetic tunnel junction (MTJ) stacks and junction leakage measurements, both relying on the principles first described by Severin and Vu.. In the 100 yr history of four-point probe measurements, all the proposed methods for electrode position correction have been based on different van der Pauw type corrections, but in this work we present a novel concept that solves the problem for length scale dependent samples that are not a single conductive sheet. We apply our correction scheme to the CIPT technique and demonstrate highly improved measurement precision (up to 3.5 times better on the precision and 17 times on the reproducibility) on RA and MR compared to the current state of the art This improvement is achieved by a proper correction for in-line position errors, while off-line errors, which are of second order, remain uncorrected

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