General trends in integrated circuit technology toward smaller device dimensions, lower thermal budgets, and simplified processing steps present severe physical and engineering challenges to ion implantation. These challenges, together with the need for physically based models at exceedingly small dimensions, are leading to a new level of understanding of fundamental defect science in Si. In this article, we review the current status and future trends in ion implantation of Si at low and high energies with particular emphasis on areas where recent advances have been made and where further understanding is needed. Particularly interesting are the emerging approaches to defect and dopant distribution modeling, transient enhanced diffusion, high energy implantation and defect accumulation, and metal impurity gettering. Developments in the use of ion beams for analysis indicate much progress has been made in one-dimensional analysis, but that severe challenges for two-dimensional characterization remain. The ...

Ion beams in silicon processing and characterization

The properties of buried layers produced by the implantation of high doses of energetic light ions O+ and N+ are reviewed. Similarities and differences in the as implanted and annealed structures are discussed as are the effects of variations in the anneal temperature, time and ramp-rate. To assess the factors governing the interfacial displacements of the growing buried layer with respect to the silicon, experiments utilising buried marker layers and involving sequential implants of O+ or N+ ions were undertaken. These confirmed the results of 18O+ and 15N+ tracer experiments by showing that during implantation the back interface of the buried layer remains effectively fixed while the front interface is displaced towards the silicon surface. During the subsequent anneal redistribution of the implanted species occurs but again this effect is most marked at the front interface.

Fabrication of buried layers of SiO2 and Si3N4 a using ion beam synthesis

The synthesis of buried layers of SiO2 and Si3N4 by ion implantation is reviewed. This process, which may be used to form device worthy silicon-on-insulator (SOI) structures, involves (i) implantation of O+ or N+ ions and (ii) high temperature processing to achieve defect annealing and chemical segregation of the implanted species.

Silicon on Insulator Formed by O+ or N+ Ion Implantation

The formation of buried layers of silicon nitride by nitrogen‐ion implantation in single‐crystal silicon is studied. He+ backscattering, x‐ray diffraction, scanning and transmission electron microscopies, and infrared absorption measurements were used for the physico‐chemical characterization; sheet resistivity determination, spreading‐resistance profile, and current‐voltage characteristics for the electrical characterization. It is shown that, for 180‐keV nitrogen ions, a fluence about 1018 N/cm2 must be implanted in order to obtain a continuous layer of silicon nitride and that annealing must be performed at 1200 °C to make it homogeneous and electrically insulating. The Si3N4 layer obtained crystallizes in the α phase and presents properties nearly similar to those of deposited layers. It is demonstrated that the conditions of implantation (energy, substrate temperature, beam intensity) play a fundamental role in the structure of the superficial silicon layer: the substrate must not be amorphized up to...

Study of buried silicon nitride layers synthesized by ion implantation

The crucial roles of high‐temperature annealing (1300–1340 °C) and ambient gas are emphasized by the electrical properties of structure fabricated on silicon‐on‐insulator by deep oxygen implantation. Hall‐effect measurements down to 77 K, as well as the characteristics of front channel and back channel transistors, show that the silicon overlay is quasihomogeneous, as a consequence of drastic improvement of the buried interface region. This is illustrated by the high carrier mobilities (1250 cm2 V−1 s−1 for electrons at 300 K), the dominance of acoustic phonon scattering, and the interface parameters that are more favorable than after low‐temperature anneals and similar to those of bulk Si. The properties and the temperature behavior of oxygen‐related donors are also investigated via the Hall effect. About 1015 cm−3 thermal donors are generated around 450–550 °C, while 1017 cm−3 new donors are formed at 750 °C. New donors presumably originate from the interface states of SiOx precipitates.

Silicon‐on‐insulator material formed by oxygen implantation and high‐temperature annealing: Carrier transport, oxygen activity, and interface properties

Buried layers of silicon nitride approximately 4000 A in width have been formed by ion implantation while retaining a relatively undamaged silicon surface region. Epitaxial silicon of 2‐μm thickness grown on these surfaces exhibits significantly lower defect concentrations than do silicon layers on spinel, as determined by optical microscopy and by proton channeling measurements. The breakdown voltage of the silicon nitride layers is approximately 7 × 105 V/cm, and the refractive index is 2.05 at 6328 A.

R. J. Dexter

Papers

Epitaxial silicon layers grown on ion‐implanted silicon nitride layers