Publications (5)1.21 Total impact
-
Conference Proceeding: Boron pile-up phenomena during ultra shallow junction formation
[show abstract] [hide abstract]
ABSTRACT: The redistribution during annealing of low-energy B implants in SOI structures and in bulk Si have been investigated by comparing Secondary Ion Mass Spectrometry (SIMS) and simulated profiles. Samples preamorphised with Ge at different implantation energies have been prepared in order to investigate the effects of the damage position on B diffusion. The specimens have been subsequently B implanted at 500 eV with doses 2times10<sup>13</sup> and 2times10<sup>14</sup> cm<sup>-2</sup> and annealed between 700 and 1100degC. SIMS profiles show a B pile-up in the first few nanometres of the Si matrix on the Si surface. Simulations of diffused profiles indicate that the B redistribution upon annealing can be explained by assuming that the mobility of the dopant which arrives in proximity of the surface is practically annulled. The amount of B trapped at the surface is maximum at the temperatures around 800degC, when more than 80% of the implanted dopant is made immobile and electrically inactive. The trapped B increases with reducing the depth of the amorphous layer and it is higher in the bulk Si than in SOI. By comparing Hall measurements and the amount of B not trapped at the surface, we also estimate the amount of B that aggregates inside the Si lattice in form of clusters (BICs). For the B dose of 2times10<sup>14</sup> cm<sup>-3</sup>, after isochronal annealing of 60 s, the amount of BICs is about 3-4times10<sup>13</sup> cm<sup>-2</sup> at the lowest temperatures and tends to vanish at high temperatures.Advanced Thermal Processing of Semiconductors, 2007. RTP 2007. 15th International Conference on; 11/2007 -
Article: Electrical activation of solid-phase epitaxially regrown ultra-low energy boron implants in Ge preamorphised silicon and SOI
[show abstract] [hide abstract]
ABSTRACT: The formation of highly activated ultra-shallow junctions (USJ) is one of the key requirements for the next generation of CMOS devices. One promising method for achieving this is the use of Ge preamorphising implants (PAI) prior to ultra-low energy B implantation. In future technology nodes, bulk silicon wafers may be supplanted by Silicon-on-Insulator (SOI), and an understanding of the Solid Phase Epitaxial (SPE) regrowth process and its correlation to dopant electrical activation in both bulk silicon and SOI is essential in order to understand the impact of this potential technology change. This kind of understanding will also enable tests of fundamental models for defect evolution and point-defect reactions at silicon/oxide interfaces. In the present work, B is implanted into Ge PAI silicon and SOI wafers with different PAI conditions and B doses, and resulting samples are annealed at various temperatures and times. Glancing-exit Rutherford Backscattering Spectrometry (RBS) is used to monitor the regrowth of the amorphous silicon, and the resulting redistribution and electrical activity of B are monitored by SIMS and Hall measurements. The results confirm the expected enhancement of regrowth velocity by B doping, and show that this velocity is otherwise independent of the substrate type and the Ge implant distribution within the amorphised layer. Hall measurements on isochronally annealed samples show that B deactivates less in SOI material than in bulk silicon, in cases where the Ge PAI end-of-range defects are close to the SOI back interface.Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 237:107-112. · 1.21 Impact Factor -
Article: Boron Deactivation in Preamorphized Silicon on Insulator: Efficiency of the Buried Oxide as an Interstitial Sink
[show abstract] [hide abstract]
ABSTRACT: Preamorphization of ultrashallow implanted boron in silicon on insulator is optimized to produce an abrupt boxlike doping profile with negligible electrical deactivation and significantly reduced transient enhanced diffusion. The effect is achieved by positioning the as-implanted amorphous/crystalline interface close to the buried oxide interface to minimize interstitials while leaving a single-crystal seed to support solid-phase epitaxy. Results support the idea that the interface between the Si overlayer and the buried oxide is an efficient interstitial sink.Nuclear Physics Group. -
Article: Diffusion and Activation of Ultrashallow B Implants in Silicon on Insulator: End-of-Range Defect Dissolution and the Buried Si/SiO2 Interface
[show abstract] [hide abstract]
ABSTRACT: The fabrication of preamorphized p-type ultrashallow junctions in silicon-on-insulator (SOI) has been investigated. Electrical and structural measurements after annealing show that boron deactivation and transient enhanced diffusion are reduced in SOI compared to bulk wafers. The reduction is strongest when the end-of-range defects of the preamorphizing implant are located deep within the silicon overlayer of the SOI silicon substrate. Results reveal a very substantial increase in the dissolution rate of the end-of-range defect band. A key player in this effect is the buried Si/SiO2 interface, which acts as an efficient sink for interstitials competing with the silicon surface.Papers from the Department of Physics. -
Article: Uphill Diffusion of Ultralow-Energy Boron Implants in Preamorphized Silicon and Silicon-on-Insulator
[show abstract] [hide abstract]
ABSTRACT: Redistribution during annealing of low-energy boron (B) implants in silicon on insulator (SOI) structures and in bulk Si has been investigated by comparing secondary ion mass spectrometry (SIMS) and simulated profiles. All the samples have been preamorphized with Ge at different implantation energies in order to investigate the effects of the position of the damage on B diffusion. Different B doses in the range between 2x10(13) and 2x10(15) cm(-2) and annealing temperatures between 700 and 1100 degrees C have been investigated. All SIMS profiles show a B pileup in the first few nanometers of the Si matrix in proximity of the Si surface. The results of our simulations, performed on samples implanted at different doses (below and above the solid solubility), indicate that the B redistribution upon annealing can be explained with a simple model which considers the presence of traps in the surface region, without considering any asymmetric behavior of the dopant diffusion. The sink region is a few monolayers (1-2 nm) for doses of 2x10(13) and 2x10(14) cm(-2), and it extends to about 7 nm for the highest dose of 2x10(15) cm(-3), in the region of very high B concentration where precipitates and clusters shrink the incoming B atoms. For the two lowest B doses, the amount of B trapped at the surface is maximum at temperatures around 800 degrees C, when more than 80% of the implanted dopant is made immobile and electrically inactive. In our experimental conditions, i.e., preamorphization performed with constant dose and different implantation energies, the amount of trapped B increases with reducing the depth of the amorphous layer and it is higher in the bulk Si than in SOI.Nuclear Physics Group.
