Papers by Author: Maria Luisa Polignano

Abstract: The recovery of the boron implantation damage can be very difficult. Depending on the energy and the dose many dislocations are generated at the projected range of the boron implantation. The morphology of these dislocations depends on the silicon substrate. In this work we demonstrate that the interstitial oxygen concentration ([Oi]) is related with the dislocation dimension, density end morphology. Particularly long dislocation dipoles were generated by the boron implantation in substrate with interstitial oxygen, and their density is connected with the [Oi] concentration.

Abstract: In this paper, a case of molybdenum contamination from wet cleaning is discussed, and various techniques are compared for their ability to detect molybdenum. In addition, the impact of this sort of contamination on the electrical results of a bipolar device is studied.

Abstract: As the detection of inorganic contaminants is of steadily increasing importance for the improvement of yields in microelectronic applications, the aim of one of the joint research activity within the European Integrated Activity of Excellence and Networking for Nano- and Micro-Electronics Analysis (ANNA, site: www.ANNA-i3.org) is the development and assessment of new methodolo¬gies and metrologies for the detection of low concentration inorganic contaminants in silicon and in novel materials. A main objective consist in the benchmarking of various analytical techniques avail¬able in the laboratories of the participating ANNA partners, including the improvement of the res¬pective detection limits as well as the quantitation reliablity of selected analytical techniques such as total-reflection x-ray fluorescence (TXRF) analysis.

Abstract: In this work we discuss an original analysis about a method to reduce the dislocation density in the devices that use the Shallow Trench Isolation (STI). It is well known that a high mechanical stress in silicon combined with an amorphizing implantation damage can generate many dislocations. So we propose to release the mechanical stress in silicon before implanting. A high temperature treatment indeed can trigger the viscous behaviour of the filling oxide inducing the relaxation of the stress field in silicon. For the first time a systematic study of the effect of different furnace and RTP annealings in the stress relaxation was done by Raman measurements. Different temperatures (from 3000C to 11000C) and different durations (from few seconds to one hour) were explored and the experimental results were compared with the numerical simulation with a good agreement. Finally we study the effect of the most promising annealings selected by Raman in a complete process flow.

Abstract: The properties of cobalt as a contaminant in p-type silicon are studied by using cobaltimplanted wafers annealed by RTP or by RTP plus a low temperature furnace annealing. It is shown that after RTP most cobalt is under the form of CoB pairs. A quantification of cobalt contamination is provided based upon SPV measurements and optical pair dissociation. However, this quantification fails in furnace-annealed wafers because of the formation of a different level. It is shown that the CoB level is located near the band edges, whereas the level formed upon a low temperature furnace annealing is located near midgap. Besides, when the cobalt concentration is high enough a small fraction of cobalt is in a level different from the CoB pair even in RTP samples. This level can probably be identified with a previously observed midgap level. It is suggested that the same level is formed in RTP plus low temperature furnace annealed samples and in high concentration RTP annealed samples, and that this level may consist in some cobalt agglomerate.