The effect of implant angle and resist shadowing in submicron implant technology
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Date
2006
Authors
Lee, Kang Hai
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Abstract
As the integrated circuit (IC) fabrication industry gears up to volume
manufacturing of 90nm technology node and beyond, there are issues still need
to be addressed at the lower technology nodes such as 0.13μm and 0.22μm. The
lateral scaling has faces limitation in dealing with the profiles encroachment due
to resist shadowing for well implant process. Driving the ion implant angle to near
normal regime is a potential solution for the above concern. Nevertheless, this
approach will lead to severe dopant channeling. Thus, there is an interest to
study the impact of implant angle and resist shadowing on sub-micron
technology. The goal for this work was to determine the feasibility of a novel
approach to forming a well with near 0 tilt implantation. To achieve this, there is
a requirement to find a compromise between dopant channeling and resist
shadowing for the high-energy implantation in low tilt angle regime. This study
will focus on low tilt angle high-energy implantation since this implant regime has
more severe issues on the resist shadowing and dopant channeling. All implant
processes in the experiments were performed by spin disk endstation GSD batch
implanter system. There are two experiments to evaluate the impact of implant
angle. The first experiment is to evaluate the uniformity of the dopant profile
across the wafer (implant uniformity) with the intention to find the optimum
implant tilt angle with acceptable implant uniformity. In this work, all sample
wafers have been prepared by performing single and quad implantations with
implant angle 0 to 7. The characterization of implant uniformity has been done
by thermal wave measurement on the sample. For low tilt high-energy
implantation, the implant uniformity is dominated by the implant beam angle
error. In terms of the dopant profile uniformity across the wafer, tilt 2 or higher tilt
angle implant has been proposed for single implant process. Meanwhile, quad 4
and quad 5 have been proposed for quad implant. The second experiment in this
work involves fabrication of the novel well structures with tilt 2 implant to create
channeled well doping profile. The device performance is compared with the
conventional well structures with dechanneled doping profiles, which were
fabricated by quad 5 implant. Based on the analysis on the transistor electrical
data, a novel implant angle scheme with improved cycle time has been
proposed. The proposed scheme improves the N+ to Nwell isolation performance
without deteriorating Id/Ioff and Vtlin/Id characteristics of MOSFET. This can be
achieved by performing high tilt quad 5 at the deep well region and low tilt 2-
degree implant at the field oxide region. The work indicates the potential of
implementing the well with channeled profiles for the improvement of isolation
performance with further optimization of the dose and energy.
Description
Master
Keywords
Mathematical science , Implant angle , Submicron