Kyung Chae Yang

A study on the etching characteristics of magnetic tunneling junction materials using DC pulse-biased inductively coupled plasmas

The etching properties of magnetic materials composing the magnetic tunnel junction (MTJ) such as CoPt, MgO, CoFeB, and CoPt/MgO/CoFeB were investigated in DC pulse biased CO/NH3 inductively coupled plasmas (ICPs) and their etch characteristics were compared with those etched by RF CW biased ICPs. The use of DC pulse biased ICPs instead of RF CW biased ICPs improved the etch selectivity of the MTJ materials over W and also decreased the residue on the surface of the etched materials possibly due to the more stable and volatile etch product formation during the DC pulse off time and the enhanced removal of the etch products by mono-energetic ions during the DC pulse on time. When MTJ materials masked with W were etched, more anisotropic etch profile could be also observed when the MTJ materials were etched with the DC pulse biasing of 60% duty percentage compared with those etched with RF CW biasing due to the decreased redeposition of etch products on the sidewall of the etched feature in addition to the enhanced etch selectivity over W.

Etch characteristics of magnetic tunnel junction materials using substrate heating in the pulse-biased inductively coupled plasma

Magnetic tunnel junction (MTJ)-related materials such as CoFeB, MgO, and W were etched in a pulse-biased inductively coupled plasma etch system using a CO/NH3 gas combination, and the effects of substrate temperature (room temperature ∼200 °C) in the pulse-biased condition on the etch characteristics of the MTJ-related material were investigated. The etch selectivity of MTJ materials over W was improved by substrate heating possibly due to the easy removal of the compounds from the etched CoFeB surface during the pulse-on time at the elevated substrate temperature. At high substrate temperature, decreased thickness of etch residue was observed not only on the bottom surface but also on the sidewall surface during the etching, which indirectly indicated the increased volatility of the etch compounds at higher substrate temperature. The etching of CoFeB features masked with W also showed a more anisotropic etch profile by heating the substrate up to 200 °C possibly due to the increased the etch selectivity ...

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

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/NH3 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/NH3 RIBE exceeds 140 eV, again similar sputter yields are found for both CoFeB side wall residues and the W hard mask.

Application of Pulsed Plasmas for Nanoscale Etching of Semiconductor Devices : A Review

As the size of the semiconductor devices shrinks to nanometer scale, the importance of plasma etching process to the fabrication of nanometer scale semiconductor devices is increasing further and further. But for the nanoscale devices, conventional plasma etching technique is extremely difficult to meet the requirement of the device fabrication, therefore, other etching techniques such as use of multi frequency plasma, source/bias/gas pulsing, etc. are investigated to meet the etching target. Until today, various pulsing techniques including pulsed plasma source and/or pulse-biased plasma etching have been tested on various materials. In this review, the experimental/theoretical studies of pulsed plasmas during the nanoscale plasma etching on etch profile, etch selectivity, uniformity, etc. have been summarized. Especially, the researches of pulsed plasma on the etching of silicon, , and magnetic materials in the semiconductor industry for further device scaling have been discussed. Those results demonstrated the importance of pulse plasma on the pattern control for achieving the best performance. Although some of the pulsing mechanism is not well established, it is believed that this review will give a certain understanding on the pulsed plasma techniques.