Analyse de la formation des phases du systeme cuivre-germanium par diffraction des rayons X sur des echantillons d'epaisseur nanoscopique

With the miniaturization of electronic devices, driven by cost reduction and performance increase, new materials have to be introduced in their fabrication process to solve many emerging problems. These challenges are brought forth by the ITRS (International Technology Roadmap for Semiconductors), a comity in charge of listing the technological needs for the upcoming generations of integrated circuits. Many fields of interest require new technological developments, from global to local interconnections, the transistor gate, the gate insulator thickness, etc.;One of the major challenges mentioned in the ITRS roadmap is the need for a new interconnection material. Indeed, the need for a diffusion barrier for the copper lines in local and global interconnections of integrated circuits, the main technology in today's devices, is becoming more hindering with the decrease of the metallization lines. cross-section. In the 90's, a binary compound of copper and germanium, known as the epsilon1-Cu3Ge phase, was investigated as a replacement for aluminum because of its low resistivity, that can reach as low as 5.5muO·cm [1], its stability in contact with both silicon and silicon oxide [2] as well as its thermal stability during anneals [3]. However, copper proved to be a better choice at the time because of its low bulk resistivity of 1.68muO·cm at room temperature[4].;The objective of this master thesis is to re-examine the copper-germanium system, and more specifically the epsilon1-Cu3Ge, for future applications in the microelectronics industry. Different X ray diffraction techniques were used to obtain more information on the system, including in situ X ray diffraction during 3°C/s anneals in an inert helium atmosphere with simultaneous resistance measurement, theta-2theta scans to detect diffraction peaks of the present phases after sample quenching as well as partial acquisition of the reciprocal space of quenched samples which allowed to obtain pole figures for d-spacings of interest.;Results obtained on germanium and copper bilayers of total thicknesses between 20nm and 89nm deposited on an inert silicon nitride layer using magnetron sputtering in an MRC-673 show that with an atomic copper concentration between 72 and 87%, the epsilon1-Cu3Ge phase starts to form between 180°C and 210°C during a 3°C/s ramp anneal. At 72% at. copper (50nm thickness) and 75% at. copper (20nm thickness), the epsilon1-Cu3Ge phase is stable above 500°C. However, the measured resistance of the 50nm sample is low between 220°C and 500°C while measured resistance for the 20nm sample it decreases by 45% between 205 and 540°C. At a temperature of 540°C, measured resistance is 10% smaller than on the initial bilayer at room temperature. This value of measured resistance is the same at the end of the measurement during the cooling of the sample at 230°C., which implies that the low resistance is kept after the phase formation. Smaller technology nodes may then require higher formation temperatures to completely form the epsilon1-Cu3Ge phase. Further challenges thus exist to make epsilon1-Cu3Ge interconnections in modern microelectronics devices. Tests with deposition techniques like co-deposition and multilayer stacks of germanium and copper must be made to determine if they can help resolve this problem. Another field of interest for further tests are isothermal anneals, which would allow the formation of the epsilon1-Cu3Ge phase during longer anneals at lower temperatures.;This thesis also allowed the acquisition of the phase formation sequence of different samples thicknesses between 20 and 89nm and copper concentrations between 72 and 87% atomic copper during 3°C/s anneals up to 850°C using in situ X ray diffraction. Brand new information was acquired on the metastable phases of the copper-germanium system. Observed diffraction peaks allowed to confirm the crystalline structures observed by Schubert and Brandauer in the 50's [5] as well as estimate the cell parameter of the body centered cubic epsilon2- Cu3Ge, which is approximately 5.03 A. Simultaneous formation of zeta-Cu5Ge and epsilon1-Cu 3Ge was also observed in a 82 % at. copper sample, which had not previously been reported in the literature.