AVS 56th International Symposium & Exhibition
    Plasma Science and Technology Thursday Sessions
       Session PS1-ThM

Paper PS1-ThM10
Etching Mechanisms of FeCo Magnetic Films by Chemically Reactive Energetic Ion Injections

Thursday, November 12, 2009, 11:00 am, Room A1

Session: Applications of Plasma-Surface Interactions
Presenter: K. Karahashi, Osaka University, Japan
Authors: K. Karahashi, Osaka University, Japan
T. Ito, Osaka University, Japan
Y. Matsumoto, Osaka University, Japan
S. Hamaguchi, Osaka University, Japan
Correspondent: Click to Email
Reactive ion etching (RIE) has been widely used for semiconductor micro fabrication processes. Recently magnetic thin films have also become materials of choice for some specific microelectronics applications such as magnetic random access memory (MRAM) and read/write heads for magnetic data storage. For micro fabrication processes of magnetic films, Ar ion milling seems to be almost the only etching technique in the current manufacturing processes. However, capabilities of Ar ion milling for anisotropic and selective etching of magnetic films are severely limited and therefore new technologies of reactive ion etching for magnetic films are now seriously sought. In this study, we have focused on etching processes of FeCo alloy thin films and examined their surface reactions caused by energetic Cl+ ion beam injections. More specifically we have measured desorbed products and etching yields (i.e., sputtering yields) of the sample, using a mass-selected ion beam system. The ion beam system can inject mono-energetic single-species ions (i.e., Cl+ or Ar ions in this study) to the sample (i.e., FeCo, Fe, or Co thin film) surface in ultra-high vacuum conditions. The reaction chamber, where the sample is placed, is equipped with a quadrupole mass spectrometer (QMS), a temperature programmed desorption (TPD) system, and an X-ray photoelectron spectroscopy (XPS). The QMS is used for the detection of desorbed products during the ion beam injections and XPS is used for in-situ chemical analyses of irradiated surfaces. The Cl+ ion beams used in this study are in the range of 250-1000eV. The etching yields are determined from measured depth profiles of irradiated surfaces and ion fluxes. It has been found that the etching yields of FeCo and Fe films by Cl+ ion injections below 300 eV are smaller than those of Co films under the same conditions. It has been also found that iron chlorides (FeClx) are formed on Fe surfaces under Cl+ ion injections and their amounts increase with the increasing Cl+ ion dose. These results indicate that the reduction of etching rate of FeCo below 500eV is caused by the formation of FeClx on the surface. TPD of volatile materials from Cl+ injected Fe surfaces has shown that FeClx desorbs when the surface temperature is above 600K. This suggests that the control of substrate temperature is crucial for Cl-based reactive ion etching of FeCo. We have also compared these results with physical sputtering characteristics of FeCo films by energetic Ar injections.