Etch residue removal of CoFeB using CO/NH3 reactive ion beam for spin transfer torque-magnetic random access memory device

Abstract

Using a reactive ion beam etching (RIBE) system, the possibility of removing the sidewall residues remaining on etched nanoscale CoFeB features and the W hard mask after using a conventional inductively coupled plasma etching system was investigated. Upon increasing the ion energy of the Ar beam, a similar sputter yield increase was found for both CoFeB side wall residues and the W hard mask. Hence, increasing the ion beam energy to improve etch residue removal efficiency at the same time induces a degradation of the CoFeB profile because of the W hard mask erosion. However, when CO/NH 3 was used as the RIBE gas mixture, at ion energy in the range of 90-110 eV, the effective residue removal from CoFeB etched features without etching the W hard mask. When the ion energy of the CO/NH 3 RIBE exceeds 140 eV, again similar sputter yields are found for both CoFeB side wall residues and the W hard mask. V

Etch characteristics of magnetic tunnel junction materials using H2/NH3 reactive ion beam

“…However, the tilting of the ion beam is limited to the etching of low density MRAM cells because the tilting of ion beam can induce a shadow effect caused by adjacent cells, especially, in the case of high density MRAM devices required for next generation STT-MRAM devices. Therefore, reactive ion beam etching (RIBE) processes using reactive gases such as CO/NH 3 instead of Ar have been investigated and, by using the RIBE without tilting the ion beam, anisotropic etch profiles of MTJ without sidewall residues could have been observed [13,14]. However, due to the use of the etch gas mixture containing oxygen, a possibility of chemical damages on the MTJ material surface during the etching and a thin oxide layer on the patterned sidewall of MTJ material still remains.…”

Improved Etch Characteristics of Magnetic Tunneling Junction Materials by Using Helium

“…has been investigated. 7,9,[19][20][21][22][23][24][25][26][27][28]31 These noncorrosive gases yield possibly noncorrosive metal volatile compounds with transition metals. 21,22 In addition, these gases give high etch selectivity due to oxidation, carbonization, and nitration of a hardmask surface.…”

“…7,9,[19][20][21][22][23][24][25][26][27][28]31 These noncorrosive gases yield possibly noncorrosive metal volatile compounds with transition metals. 21,22 In addition, these gases give high etch selectivity due to oxidation, carbonization, and nitration of a hardmask surface. 27 However, oxygen in the gas chemistry tends to induce chemical damage on the MTJ material surface during the etching and form a thin oxide layer on the patterned sidewall of MTJ materials, which reduces the performance of the device, even though the oxide layer can be partially removed using a H 2 plasma.…”