Materials Processing
Grain refining of Al-Si based alloys was studied from the thermodynamics point of view, providing a comprehensive picture for the joint additions of Ti and B or Ce [05Gro1, 04Gro].
The processing of a wide range of metal contacts to compound semiconductors, such as GaN, SiC, ZnSe, CdTe or GaAs was investigated2a). In an integrated approach the ternary phase diagrams, the interface reactions in thin film and bulk diffusion cou-ples and the electrical properties of such contacts in structured thin film patterns were studied [01Wen, 96Goe, 96Bha]. A working diode could be produced from Ti and SiC by exploiting the knowledge about new phases formed at the metal/semiconductor inter-face and their impact on electrical properties [96Goe].
In the Czochralski process for production of semiconductor Si the interactions between liquid silicon and the silica crucible become detrimental during the long growth time required for 300 mm diameter single crystal rods. The thermodynamic driving forces for the pertinent processes in the Si-O system and the nature and morpology of the detrimental reaction products could be revealed, thus forming the basis for an ap-propriate process optimization2b) [04Sch, 03Sch].
Diffusion soldering can be used to produce joints at a low temperature that are subsequently stable at higher temperatures by applying the process of isothermal solidi-fication2c). In a study of reaction kinetics and phase formation it was shown that, when aiming at very high temperature stable bonds, only the material combinations Pt/In, Pd/In and Zr/Sn prove useful [03Stu]. Currently research is ongoing to optimize the dif-fusion soldering process for optoelectronic applications involving multicomponent systems2d).
- [05Gro1] J. Gröbner, D. Mirkovic, R. Schmid-Fetzer: Thermodynamic aspects of grain refinement of Al-Si alloys using Ti and B. Materials Science and Engineering A, 395, 10-21 (2005)
- [04Sch] S.M. Schnurre, J. Gröbner, R. Schmid-Fetzer: Thermodynamics and phase stability in the Si-O system. J. Non-Cryst. Solids, 336, 1-25 (2004)
- [04Gro] J. Gröbner, D. Mirkovic, R. Schmid-Fetzer: Thermodynamic Aspects of Consti-tution, Grain Refining and Solidification Enthalpies of Al-Ce-Si Alloys. Metall. Ma-ter. Trans. A, 35A, 3349-3362 (2004)
- [03Stu] T. Studnitzky, R. Schmid-Fetzer: Phase formation and diffusion soldering in Pt/In, Pd/In and Zr/Sn thin film systems. J. Electronic Materials 32, 70-80 (2003)
- [03Sch] S.M. Schnurre, R. Schmid-Fetzer: Reactions at the liquid silicon / silica glass interface. J. Cryst. Growth 250, 370-381 (2003)
- [01Wen] R. Wenzel, G. G. Fischer, R. Schmid-Fetzer: Ohmic contacts on p-GaN (Part I): Investigation of different contact metals and their thermal treatment. Mater. Sci. Semicond. Proc., 4, 357-365 (2001)
- [96Goe] F. Goesmann and R. Schmid-Fetzer: Temperature dependent interface reac-tions and electrical contact properties of titanium on 6H-SiC. Semicond. Sci. Technol., 10, 1652-1658 (1995) and 11, 461 (1996)
- [96Bha] K. Bhanumurthy and R. Schmid-Fetzer: Experimental study of ternary Pd-Si-C phase equilibria and Pd/SiC interface reactions. Z. Metallkde., 87, 244-253 (1996)
Cooperations
2a) Siemens AG, München/ Erlangen.2b) Wacker Siltronic AG, Burghausen;Heraeus Quarzglas, Hanau/ Bitterfeld; INW, TU Clausthal.
2c) DaimlerChrysler Corporate Research, Microelectronics and Microsystems, Frankfurt.
2d) Osram Optoelectronics, Regensburg