A comprehensive study on interface perpendicular MTJ variability

Won Ho Choi, Jongyeon Kim, Ibrahim Ahmed, Chris H. Kim

Research output: Chapter in Book/Report/Conference proceedingConference contribution

2 Scopus citations


Spin transfer torque MRAM (STT-MRAM) is one of the promising candidates as a scalable nonvolatile memory with high density, and CMOS compatibility [1], [2]. Interface perpendicular magnetic tunnel junction (PMTJ) shown in Fig. 1 has been demonstrated with the goal of reducing the switching current while maintaining sufficient nonvolatility [3]. However, previous studies report that PMTJ suffers from process-dependent dimensional variations, thus it remains one of the major constrains in achieving high performance STT-MRAM [4, 5]. As shown in the equations of Fig. 1, the anisotropy field (HK) and free layer volume (V) are functions of PMTJ dimensions, hence their variations result in variation of STT switching characteristics such as thermal stability factor (Δ) and switching current (IC). The HK of PMTJ has a strong dependency on relative ratio between the free layer thickness (tF) and the critical thickness (tC) [3]. The equations of Fig. 1 suggest that the tF variation differently affects the PMTJ dimension-dependent parameters (gray circles), resulting in either increasing or decreasing Δ and/or IC. This paper presents a comprehensive study on process-dependent dimensional variability of PMTJ, especially focusing on estimating the impact of tF variation on Δ and IC variability. For a practical analysis, our physics-based macrospin SPICE model [7] captures the key physics of STT switching in PMTJ by incorporating all of the above mentioned PMTJ dimension-dependent parameters into the Landau-Lifshitz-Gilbert (LLG) equation.

Original languageEnglish (US)
Title of host publication73rd Annual Device Research Conference, DRC 2015
PublisherInstitute of Electrical and Electronics Engineers Inc.
Number of pages2
ISBN (Electronic)9781467381345
StatePublished - Aug 3 2015
Event73rd Annual Device Research Conference, DRC 2015 - Columbus, United States
Duration: Jun 21 2015Jun 24 2015

Publication series

NameDevice Research Conference - Conference Digest, DRC
ISSN (Print)1548-3770


Conference73rd Annual Device Research Conference, DRC 2015
Country/TerritoryUnited States

Bibliographical note

Publisher Copyright:
© 2015 IEEE.


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