Nanoelectronics laboratory: Molecular Beam Epitaxy Facility
As part of Prof. Yang's Nanoelectronics Laboratory,
this facility is located in the Laboratory for Physical Sciences.
the instrument is a UHV (Ultra-High Vacuum) crystal growth system, for
the growth of device-quality, epitaxial silicides on silicon. The system
has a single-source, load-lock UHV chamber, and the following important
features: two effusion cells for co-depositing silicon and metals, one
e-beam source for evaporating refractory metals, one temperature-controlled
substrate holder, and optical access to the substrate for pyrometry and
ellipsometry. The in situ analysis tools that will go with the system include:
RHEED gun/screen for surface structure identification and ellipsometer
for measurement of film thickness and index of refraction. Ex situ analysis
include STM, BEEM, TEM, PEEM, SEM, EBIC, CL, and EDS (Energy Dispersive
Spectroscopy) X-ray system for composition analysis. The silicides have
been widely applied in the fabrication of advanced, deep sub-micron silicon-based
integrated circuits for their low resistivity and full compatibility with
the silicon-based material system. Yet, there are many unanswered questions
in terms of their properties and reliability, especially at the silicide
interface with silicon and interconnect metals. Further improvement of
epitaxial silicide is therefore vital for scaling MOSFETs. In addition
to developing the growth techniques and investigating their fundamental
properties, such as their effective mass, transport physics, conductivity,
reliability, size-quantization effects, etc., we will specifically apply
the epitaxial silicides in the fabrication of ultrasmall MOSFETs.
This patent-pending new MOSFET structure uses the silicide/silicon heterojunction
to totally remove the infamous Short-Channel Effect, and, as a result,
the effective channel length can be down scaled to about 10 nanometers.
Compared with today's perceived MOSFET scaling limit (About 100 nm, according
to The National Technology Roadmap For Semiconductors, Semiconductor Industry
Association, 1994.), such a scalability represents a factor of 100 further
increase in packing density. Recent computer simulation has provided promising
results, including the transistor characteristics, transient performance
in logic circuits, and optimized structural parameters. Our immediate goal
is to experimentally realize the World's Smallest MOSFETs using our silicide/silicon
heterojunctions. Successful results will for sure bring a significant impact
to the highly competitive IC industry.