Nanoscale Spin-Transfer Torque MRAM Etching Using Various Gases

The spin-based memory, spin transfer torque-magnetic random access memory (STT-MRAM), has the potential to enhance the power efficiency of high density memory systems. Its desirable characteristics include nonvolatility, fast operation, and long endurance. However, dry etching of MRAM structures remains a challenge as the industry is ramping up its production. In this paper, we explore the etching strategies that have been used to etch the MRAM structures. Several etching techniques have been developed to attain optimal device performance. These are reactive ion etching, time modulated plasma etching, atomic layer etching, and ion beam etching. Sidewall profile, sidewall contamination or damage, redeposition, selectivity, and noncorrosiveness are the main factors to consider while selecting the best etching methods. This paper starts with the fundamentals of MRAM reading, writing, and storing principles and finishes with the current approaches to solve the etch challenges. For etching, the most commonly used magnetic materials such as CoFeB, CoFe, and NiFe are covered in this article.

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Dry etching strategy of spin-transfer-torque magnetic random access memory: A review

Islam

Cui

Miao

2020

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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Etching damage induced performance degradation in spin transfer torque magnetic random access memory fabrication

Wang

Zuo²,

Ji³

et al. 2021

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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Damage mechanisms and related performance degradations induced by ion beam etching (IBE) process in the fabrication of magnetic tunnel junctions (MTJs) were studied systematically. The loss in tunneling magnetoresistance (TMR) and coercive field (Hc) was investigated with different MTJ pillar sizes and IBE incident angles. It is found that IBE-induced damage is the formation of a surficial amorphous shell in the outer rim of an MTJ pillar. This amorphous shell is of low conductivity and TMR, mainly arising from the lattice damage of MgO barrier and partial oxidation of free/reference layers. Based on experimental and theoretical findings, we optimized the IBE process to reduce the damage as well as recover from degradation. As a result, the TMR loss ratio in comparison with a blanket film is reduced from about 18% to 7%, and Hc is increased from 1490 to 2280 Oe for the same stack.

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Prediction on MRAM Etching Endpoint by Response Surface Method

Ding

Jiang

2023

J. Mod. Mech. Eng. Technol.

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STT-MRAM (Spin-Transfer-Torque Magnetic Random Access Memory) with high-density is considered as one of the most promising storage candidates with potential applications. In the process of MRAM manufacturing, etching step should be stopped precisely at the specific material layer. The dielectric layer should be protected with certain coverage. Then the subsequent etching steps continue. It is crucial to detect the endpoint of the etching during the fabrication process. In the paper, the factors influencing the etching rate are analysed, including gas pressure, gas temperature, ion sheath thickness, self-biased DC voltage and RF power frequency, respectively. An approach based on Response Surface Method (RSM) is adopted to predict the endpoint of the etching process. The optimized interplay relationship is set up among the gas pressure, the gas temperature, the ion sheath thickness, the self-biased DC voltage and the RF power frequency, et al.. It shows that RSM approach is an effective statistical method for the optimization on the etching stop technology, especially when the complex etching condition options are involved. The simulation results demonstrate the MRAM sidewall smoothness can be improved under the optimized etching environment configuration.

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Nanoscale Spin-Transfer Torque MRAM Etching Using Various Gases

Cited by 3 publications

References 13 publications

Dry etching strategy of spin-transfer-torque magnetic random access memory: A review

Dry etching strategy of spin-transfer-torque magnetic random access memory: A review

Etching damage induced performance degradation in spin transfer torque magnetic random access memory fabrication

Prediction on MRAM Etching Endpoint by Response Surface Method

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