| 학회 | 한국재료학회 |
| 학술대회 | 2015년 가을 (11/25 ~ 11/27, 부산 해운대그랜드호텔) |
| 권호 | 21권 2호 |
| 발표분야 | A. 전자/반도체 재료 |
| 제목 | Effect of Bias Frequency on the Etching of Magnetic Tunnel junction Materials |
| 초록 | Spin Torque Transfer Magnetic Random Access Memory (STT-MRAM) offers non-volatility of information, high density of memory cells, and high read/write cycle endurance for flash memory device. However, there are some problems in the etching of STT-MRAM materials.1 One of the most serious problems is the re-deposition on the sidewall of the sputtered atom and non-volatile byproduct formed during the etching such as Ion Beam Etching (IBE), Reactive Ion Etching (RIE), etc.2 Also, to remove the possibility of corrosion on the magnetic materials during the etching using halogen gases, noncorrosive gas mixtures such as CO/NH3 gas mixture have been investigated. In this study, to improve the etch profiles by decreasing the re-deposition of etch products, bias pulsing frequency has been varied (13.56 MHz to 400 kHz) during the bias pulsing (duty ratio 50% and pulse frequency 50 kHz) and the effect bias pulsing on the etch characteristics has been investigated. High selectivity and anisotropic etch profile can be obtained appropriate ion energy and proper ion distribution. A sputtering yield is mainly determined by ion bombardment energy distribution. To get higher sputtering yield, bias frequency was decreased from 13.56 MHz to 400 kHz while keeping the substrate average bias voltage at the same voltage. Three kinds of samples composed of CoPt(10 nm)/MgO(1 nm)/CoFeB(10 nm) = MTJ, CoPt(20 nm) and CoFeB(20nm) on silicon wafer/SiO2(25 nm)/Ta(5 nm) and with a hardmask composed of W(100 nm)/Ti(20 nm)/Ru(5 nm) was used to investigate etch profile. The etch profiles each samples analyzed with field emission scanning electron microscopy (FE-SEM). Blanket unit thin films samples such as CoPt, MgO, CoFeB and W with photoresist were prepared to calculate the etch rate and etch selectivity calculated by surface profilometer. 1) Dmytro Apalkov et al., "Spin-transfer torque magnetic random access memory (STT-MRAM)," ACM Journal on Emerging Technologies in Computing Systems (JETC) 9 (2), 13 (2013). 2) Xilin Peng et al., "Towards the sub-50nm magnetic device definition: Ion beam etching (IBE) vs plasma-based etching," Vacuum 83 (6), 1007-1013 (2009). |
| 저자 | Geun Young Yeom1, Kyong Nam Kim2, Kyung Chae Yang3, Sung Woo Park4 |
| 소속 | 1School of Advanced Materials Science and Engineering, 2Sungkyunkwan Univ. (SKKU), 3Suwon, 4Gyeonggi-do 440-746 |
| 키워드 | <P>STT-MRAM; pulse plasma; side wall re-deposition; frequency variation</P> |
