| AVS 60th International Symposium and Exhibition | |
| Plasma Science and Technology | Monday Sessions |
| Session PS-MoM |
| Session: | Innovative Chemistries for Advanced Etch Processes |
| Presenter: | T. Kim, University of California at Los Angeles |
| Authors: | T. Kim, University of California at Los Angeles K. Chen, University of California at Los Angeles J.P. Chang, University of California at Los Angeles |
| Correspondent: | Click to Email |
Magnetic tunnel junctions (MTJ) which are based on magnetic hysteresis for data storage are an important part of spin-electronics. An MTJ-based magnetoresisitive random-access memory (MRAM) has several advantages, such as nonvolatility, fast writing speeds (2-4 ns). Thus MRAM has the potential to be a universal memory solution. In past few years, some important progress has been reported to fabricate durable, high-yield MTJ arrays, using the advances in materials.
Among the challenges of fabrication, MTJ etching processes is one of the most critical. Ion beam etching was a general etching technique at the beginning of MTJ fabrication, however the etched material tends to re-deposit on the sidewalls and form fences. The approach using a reactive ion etch (RIE) has been recognized as an important strategy for integrating MRAM because it can potentially generate volatile etch products to avoid sidewall re-deposition. Halogen-gas-based RIE processes have been used to etch ferromagnetic layers. Some chemical enhancement induced by RIE has been reported for NiFe and NiFeCo using Cl2 gases,[1] however the low etch rate requires high-density plasma conditions.
In this work, a thermodynamic approach is used to assess the feasibility of various etch chemistries, beginning with the consideration of reactions between the dominant vapor phase/condensed species and the surface at various temperatures and reactant partial pressures. The volatility of etch product was determined to aid the selection of viable etch chemistry leading to improved etch rate of RIE process.[2] In this report, a few magnetic metals are considered (Co, Fe, and Ni) along with various halogen and organometallic based chemistries. The thermodynamically favorable reaction has been investigated and the vapor pressure of its product has been calculated. In addition, the vapor pressure enhancement induced by adding secondary gas such as hydrogen has also been studied. Experimental validation is an important part to prove the prediction.
[1] K.B. Jung et al., J. Electron. Matet., 27, 972 (1998)
[2] N.S. Kulkarni et al., J. Electro. Soc., 149 , G620 (2002)