[en] The analysis of the etch-stop properties of layers obtained by substoichiometric nitrogen-ion implantation and annealing in silicon has been performed as a function of the implantation conditions. The analysis of the etching efficiency has been tested in TMAH-IPA systems. The results obtained show the need to implant at doses higher than 2 x 10¹⁷ cm^-2 to obtain etch-stop layers stable under high-temperature annealing. So, for implantation doses of 5 x 10¹⁷ cm^-2, layers stand unetched for times longer than 2 h. The preliminary structural analysis of the samples suggests the presence of an amorphous silicon nitride layer for higher implantation doses. (author)

[en] In this work the etch-stop behavior of buried layers formed by substoichiometric nitrogen ion implantation into silicon is studied as a function of the processing parameters, the implantation dose and temperature, and the presence of capping layers during implantation. Etching characteristics have been probed using tetramethylammonium hydroxide or KOH solutions for different times up to 6 h. Results show that, after annealing, the minimum dose required for the formation of an efficient etch-stop layer is about 4 x 10¹⁷ cm^-2, for an implantation energy of 75 keV. This is defined as a layer with an efficient etch selectivity in relation to Si of s ≥ 100. For larger implantation doses efficient etch selectivities larger than 100 are obtained. However, for these doses a considerable density of pits is observed in the etch-stop layer. These are related to the presence of nitrogen poor Si regions in the buried layer after annealing, due to a partial separation of silicon and silicon nitride phases during the annealing process. The influence of this separation of phases as well as nitrogen gettering in the buried layer on the etch-stop behavior is discussed as a function of the processing parameters

[en] The use of high dose carbon ion implantation in Si for the production of membranes and microstructures is investigated. Si wafers were implanted with carbon doses of 10¹⁷ and 5 x 10¹⁷ cm^-2, at an energy of 300 keV and a temperature of 500 C. The structural analysis of these samples revealed the formation of a highly stable buried layer of crystalline β-SiC precipitates aligned with the Si matrix. The etch-stop properties of this layer have been investigated using tetramethyl-ammonium hydroxide as etchant solution. Secondary ion mass spectrometry measurements performed on the etched samples have allowed an estimate of the minimum dose needed for obtaining an etch-stop layer to a value in the range 2 to 3 x 10¹⁷ ions/cm². This behavior has been explained assuming the existence of a percolation process in a SiC/Si binary system. Finally, very thin crystalline membranes and self-standing structures with average surface roughness in the range 6 to 7 nm have been obtained