Damage formation and annealing studies of low energy ion implants ...

enhanced diffusion of the implanted dopant ions, many orders of magnitude higher than
standard Fickian diffusion called transient enhanced diffusion (TED). Diffusion can
limit the shallowness of the transistor junction produced and consequently has important
implications for device production.
Pre-amorphisation is also carried out to minimise channelling of implanted
dopant ions (26). Traditionally amorphisation has been carried out using Ge implants
but in the studies in this thesis Xe has been predominantly used. Using a deeper preamorphising
implant (PAI) can spatially separate the end of range damage from the
junction depth.
1.5 Objective, preparation, analysis techniques and equipment
The objective of the studies reported in this thesis was to investigate near surface
damage formation and regrowth processes as well as the behaviour of dopant ions
implanted into silicon during ultra low energy ion implantation and annealing. The
focus was to study conditions typical for forming ultra shallow junctions (USJ’s), for
source / drains and extensions. Implant and annealing conditions are similar to those
used in actual device production (i.e. 3keV BF2 and As). However a particular interest
was to gain a better understanding of the mechanisms involved using detailed structural
characterisation of the as-implanted and annealed Si. For this reason there is special
emphasis on using lower annealing temperatures to capture the various stages of
regrowth which cannot be identified under production annealing conditions. The work
formed part of a European project, IMPULSE (27), the project aims of which were to
get a complete physical and electrical characterisation of implants and to identify the
optimum implantation and anneal process conditions for the latest generation transistors.
The work was performed in close collaboration with Advanced Micro Devices (AMD)
in Dresden, Germany.
Additional work has been carried out in close collaboration with Applied
Materials Implant Division, part of one of the largest equipment manufacturers in the
semiconductor industry.
Implanted and annealed samples used in this project have been produced at The
University of Salford using the Ultra Low Energy Implanter (28), by AMD, in Dresden
as part of the IMPULSE project (27), and by Applied Materials Ltd. Both AMD and
Applied Materials used Applied Materials Quantum LEAP implanters (29).
The main analysis technique used for the characterisation of the samples was
medium energy ions scattering (MEIS). In essence a high resolution variation of the
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