Ion beam etching of 30nm scale spin transfer torque magnetic tunnel junction, Sungwoo Chun, Jihun Kwon, Seonjun Choi, Bongho Kim, Daehong Kim and Seung-Beck Lee, International Symposium on the Physics of Semiconductors and Applications(ISPSA) 2011. July 6, 2011, Ramada Plaza Jeju Hotel, Jeju, Korea