J. J. Hamilton

Diffusion and activation of ultrashallow B implants in silicon on insulator: End-of-range defect dissolution and the buried Si∕SiO2 interface

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.

Boron deactivation in preamorphized silicon on insulator: Efficiency of the buried oxide as an interstitial sink

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.

Uphill diffusion of ultralow-energy boron implants in preamorphized silicon and silicon-on-insulator

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 2×1013 and 2×1015 cm−2 and annealing temperatures between 700 and 1100 °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 ...

Modeling and Simulation of the Influence of SOI Structure on Damage Evolution and Ultra-shallow Junction Formed by Ge Preamorphization Implants and Solid Phase Epitaxial Regrowth

Preamorphization implant (PAI) prior to dopant implantation, followed by solid phase epitaxial regrowth (SPER) is of great interest due to its ability to form highly-activated ultrashallow junctions. Coupled with growing interest in the use of silicon-on-insulator (SOI) wafers, modeling and simulating the influence of SOI structure on damage evolution and ultra-shallow junction formation is required. In this work, we use a kinetic Monte Carlo (kMC) simulator to model the different mechanisms involved in the process of ultra-shallow junction formation, including amorphization, recrystallization, defect interaction and evolution, as well as dopantdefect interaction in both bulk silicon and SOI. Simulation results of dopant concentration profiles and dopant activation are in good agreement with experimental data and can provide important insight for optimizing the process in bulk silicon and SOI.

Effect of buried Si/SiO2 interface on dopant and defect evolution in preamorphizing implant ultrashallow junction

P-type ultrashallow junctions are widely fabricated using Ge preamorphization prior to ultralow-energy boron implantation. However, for future technology nodes, issues arise when bulk silicon is supplanted by silicon-on-insulator (SOI). An understanding of the effect of the buried Si∕SiO2 interface on defect evolution, electrical activation, and diffusion is needed in order to optimize the preamorphization technique. In the present study, boron has been implanted in germanium preamorphized silicon and SOI wafers with different preamorphizing implant conditions. Subsequent to implantation an isothermal annealing study of the samples was carried out. Electrical and structural properties were measured by Hall-effect and secondary-ion-mass spectroscopy techniques. The results show a variety of interesting effects. For the case where the Ge preamorphization end-of-range defects are close to the buried oxide interface, there is less dopant deactivation and less transient-enhanced diffusion, due to a lower inter...

Interaction of the end of range defect band with the upper buried oxide interface for B and BF2 implants in Si and silicon on insulator with and without preamorphizing implant

The International Roadmap for Semiconductors requires ultrashallow, highly activated, abrupt dopant profiles in the source/drain extension regions, for technology nodes beyond 45nm. The authors contrast B and BF2 implants in Si and silicon on insulator (SOI) substrates with and without a preamorphizing implant (PAI). The objective of the study is to compare between Si and SOI substrates, PAI and non-PAI condition, and B and BF2 implants. The results show the absence of the “reverse annealing effect” in BF2 implants, which is observed in B implants. The presence of F appears to impede the formation of boron interstitial clusters, which is shown in the case of B implant. The BF2 implants follow a similar trend for SOI and Si with and without PAI.

Effect of B dose and Ge preamorphization energy on the electrical and structural properties of ultrashallow junctions in silicon-on-insulator

Formation of highly activated, ultra-shallow and abrupt profiles is a key requirement for the next generations of CMOS devices, particularly for source-drain extensions. For p-type dopant implants (boron), a promising method of increasing junction abruptness is to use Ge preamorphizing implants prior to ultra-low energy B implantation and solid-phase epitaxy regrowth to re-crystallize the amorphous Si. However, for future technology nodes, new issues arise when bulk silicon is supplanted by silicon-on-insulator (SOI). Previous results have shown that the buried Si/SiO2 interface can improve dopant activation, but the effect depends on the detailed preamorphization conditions and further optimization is required. In this paper a range of B doses and Ge energies have been chosen in order to situate the end-of-range (EOR) defect band at various distances from the back interface of the active silicon film (the interface with the buried oxide), in order to explore and optimize further the effect of the interface on dopant behavior. Electrical and structural properties were measured by Hall Effect and SIMS techniques. The results show that the boron deactivates less in SOI material than in bulk silicon, and crucially, that the effect increases as the distance from the EOR defect band to the back interface is decreased. For the closest distances, an increase injunction steepness is also observed, even though the B is located close to the top surface, and thus far from the back interface. The position of the EOR defect band shows the strongest influence for lower B doses.

A Comparative Study of Interaction of End of Range (EOR) Defect Band with Upper Buried Oxide (BOX) Interface for B and BF2 Implants in SOI and Bulk Silicon with Pre‐Amorphizing Implant.

Highly active, ultra‐shallow and abrupt dopant profiles are required for future generations of CMOS devices. A possible way to achieve this is to use pre‐amorphization implantation (PAI) and solid phase epitaxial re‐growth. B and BF2 implants were studied in bulk silicon and silicon‐on‐insulator with Ge PAI. Results show that buried oxide (BOX) in SOI can be used a sink for silicon interstitials contributing to boron Transient Enhanced Diffusion and Boron‐Interstitial Clustering. The BF2 implants show high mobility values and no deactivation.

Boron pile-up phenomena during ultra shallow junction formation

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 2times1013 and 2times1014 cm-2 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 2times1014 cm-3, after isochronal annealing of 60 s, the amount of BICs is about 3-4times1013 cm-2 at the lowest temperatures and tends to vanish at high temperatures.

Optimal preamorphization conditions for the formation of highly activated ultra shallow junctions in Silicon-on-insulator

Preamorphising implants (PAI) in Silicon‐on‐insulator (SOI) compared with bulk silicon substrates have been shown to improve junction properties. This paper studies the optimization of electrical behavior of this process in SOI. We will show that the deactivation caused by end‐of‐range (EOR) defects is vastly reduced in SOI by positioning the EOR band as close as possible to the buried oxide (BOX) interface while still allowing crystal regrowth to occur. Results show a 3% deactivation in SOI compared to 10% in bulk Si.