| AVS 54th International Symposium | |
| Plasma Science and Technology | Tuesday Sessions |
| Session PS2-TuM |
| Session: | Advanced Gate Etch |
| Presenter: | R.M. Martin, University of California at Los Angeles |
| Authors: | R.M. Martin, University of California at Los Angeles H.-O. Blom, Uppsala University, Sweden J.P. Chang, University of California at Los Angeles |
| Correspondent: | Click to Email |
The development of plasma etching chemistries is necessary to pattern new gate dielectric materials, such as hafnium-based oxides, for sub-45nm CMOS devices. Hafnium aluminates (Hf1-xAlxOy) have arisen as a promising material for gate oxide replacement due to their high dielectric constant, bandgap, and recrystallization temperature. Hafnium aluminates with the Al2O3 content varying from 0 to 100% were synthesized to study the effect of alumina addition to hafnia. An electron cyclotron resonance high density plasma reactor was used in this work to study the etching of hafnium aluminates in chlorine-based chemistries. The plasma density, electron temperature, and gas phase reactive species were characterized by a Langmuir probe, optical emission spectroscopy, and quadrupole mass spectrometry (QMS). Hf1-xAlxOy films were etched in Cl2 and BCl3 plasmas and the etch rate scaled linearly with the square root of ion energy at high ion energies (> 50 eV), however the etch rate in BCl3 was 1.5 to 2 times that in Cl2. The faster etch rate in BCl3 was attributed to a change in the dominant ion from Cl2+ to BCl2+ as determined by QMS. At low ion energies, (< 50 eV), a physical-sputtering-like process was observed in Cl2 while deposition was observed in BCl3. The dominant metal-containing etch products were HfClx and AlClx in Cl2 plasma and HfClx, HfBOCl4, AlClx, and Al2Clx in BCl3 plasmas, and increased with ion energy. Oxygen was detected removed in the form of ClO in Cl2 and (BOCl)3 in BCl3 plasmas. The etching threshold energy can be tuned by about 2 eV by changing the film composition, making it possible to design a composiiton near the interface to maximize the etching selectivity with respect to silicon. Chlorine was measured on the surface of all etched films (0-3 at. %) as well as boron (~7 at. %) for the BCl3-etched films. The surface chlorination was enhanced with increasing ion energy, demonstrating that the etching reaction is limited by the momentum transfer from the ions to the film surface. Finally, a generalized phenomenological model will be presented to elucidate the effect of Al2O3 addition on modifying the etching characteristics of HfO2.