INTRODUCTION
This work incorporates the results of 41 years experience in ion implantation
(1964-2004) and 36 years in secondary ion mass spectrometry (SIMS) (1969-2004).
These two technologies became intertwined when the need became apparent for the
measurement of depth profiles of elements implanted into many materials under many
conditions during and after implantation, for which SIMS was ideally suited, and the
realization that while SIMS was a powerful tool for this, SIMS required accurate calibration
for the many elements in the many materials, for which ion implantation offered a versatile
solution. During 1968, Charles A. Evans, Jr. and I set out to meet these reciprocal needs,
and in April of 1959, I began a long series of trips between Malibu CA (then Hughes
Research Laboratories) and the San Francisco Bay area where Charles Evans and
Associates had several laborator locations during the next 35 years.
Some years later, Fred A. Stevie joined this collaboration and between us implants
of 83 elements into Si were studied, and 76 elements were implanted into other materials,
especially GaAs. About 60 materials were implanted and studied using SIMS during these
years.
In 1974, George brewer and I published a book (John Wiley) on ion beams and ion
implantation, and in 1989, Fred Stevie, Charles Magee, and I published a book on SIMS
(Wiley Interscience). The latter book deals primarily with SIMS of semiconductors.
This present work adds metals, insulators, (conductors), insulators (dielectrics), wide
bandgap materials, and polymers, to this list of substrate materials. These additions
broaden substantially the materials list for which the techniques described in Wilson,
Stevie, and Magee (WSM) have been applied. Si and the other semiconductor materials
studied in WSM are included here for comparison and completeness; some new data,
especially actual figures are included here. The total list now includes:
Metals (conductors): Be, Al, Ti, TiN, TiSi2, Ni, Cu, W, Au
Insulators (dielectrics): SiO2, Si3N4, Al2O3, LiNbO3, UO2
Semiconductors: SI, Ge, GaP, GaAs, GaSb, InP, InAs, InSb, HgCdTe
Wide Bandgap materials: diamond (C), SiC, GaN, ZnSe, ZnS
Polymers: epoxy, polymethylmethacralate/PMMA/Lucite/AZ111,
polypromellitimide/polyimide/Kapton
ACKNOWLEDGMENTS – PEOPLE, ORGANIZATIONS, SUPPORT
Throughout these 41 years, various people and organizations have helped or supported
this work in various ways.
Significant financial support via Independent Research and Development funds (IRD)
within
Hughes Aircraft Company at Hughes Research Laboratories. The associated amount of
money can only be roughly estimated, but if we assume about 100K$ per year for 25
years, the amount is of the order of 2.5M$.
Significant financial support was provides via IRD and internal funding within Charles
Evans
and Associates during the years 1969-1998. If we assume 30K$ per year for 20 years, the
amount is about 600K$.
Significant financial support was provided via the federal government, especially the DoD
and the Army Research Office in particular. See the list of government contracts given at
the end of this section.
Persons who have contributed to or supported in some way this work include:
George R. Brewer HRL, my close associate and supporter at HRL, without whom this
would not have happened. Thanks, George
Robert Bower HAC
James Comas NRL
Harry Dietrich NRL
John Davies Chalk River Nuclear Laboratories
Vaughn Deline CEA
Fred Eisen Rockwell Science center
James Ehrstein NBS -> NIST
Charles A. Evans, Jr. CEA, my friend and supporter, without whom this would not have
happened. Thanks, Drew
James Gibbons Stanford University
Ken Galloway NBS -> NIST
Charles Hitzman CEA
Harold Hughes NRL
Douglas Jamba HRL, my associate in the lab in Malibu for 25 years, without whom this
would not have happened. Thanks, Doug
Ogden Marsh HRL
James Mayer HRL -> ASU
Steven Novak CEA
Douglas Phinney Lawrence Livermore Laboratory. Thanks, Doug for your support
Steven J, Pearton Univ. Florida Thanks, Steve for your support
Devendra Sadana UC Berkeley
Steve Smith CEA
Fred A. Stevie BTL -> Lucent -> NCSU, without whom much of this would not have
happened. Thanks, Fred
Edward Wolf HRL -> Cornell U.
Max Yoder NRL
John Zavada ARO, without whom this would not have happened. Thanks, John for
your support in many ways for so long a time.
My wife, Billie, without whom this would not have happened.
Financial support was provided via various government contracts, as follows:
Gov’t
Contract No.
Program Title
Dates
Agency
NASA
NAS-3-5249
Electrode surface physics research
1963-Jun1965
NASA
NAS 3-5278
Ion thruster surface physic studies/
Jun1965Jun1967
Work function & adsorption energy calcs.
AFAL
AF33(616)=3821 Ion implantation doping techniques
Oct1966Oct1968
ONR /N00014-69-C-0171
Selective doping of piezoelectric
NASC
crystals by ion implantation
AFML
F33615-70-C-1238 Manufacturing methods for ion implanted Sep1970Sep1972
MOSFET devices and circuits
NARAIR N00019-69-C-0691 Beam techniques for the fabrication of
Sep1969Sep1970
Microwave integrated circuits
N00019-72-C-0364
with R.L. Seliger
Jan1972-Jan1973
N00019-73-C-0261
Jan1973-Mar1974
NESC
N00039-73-C-0059 Integrated Circuit and Manufacturing
May1973Nov1973
Science and Technology (ICRMS)
NOSC N00123-73-C-1081 Fabrication techniques for integrated
Sep1972Feb1973
Optical circuitry
NOSC/ N00123-75-C-0080 SOS isolation techniques
Oct1974Aug1975
NRL
DARPA/DoC 5-35891 Critical implantation parameters
Apr1975-Jun1980
DARPA/ N00014-81-C-0286 Implantation damage and regrowth
Feb1981Feb1982
ONR
DARPA/ MDA-903-83-C-0108 Channeling in IR detector materials Jun1982-Mar1986
SBRC Part of HgCdTe surface and defect study program SBRC
ARO
DAAL03-86-C-0010 Secondary ion mass spectrometry
Apr1986Dec1989
C. Evans and Assoc. char. Of implants into GaAs and
InP for waveguides and integrated optics
NRL/
N0014-87-C-2389
Materials improvement techniques and
Sep1987Nov1989
DNA
diagnostics of SIMOX structures
NOSC N6601-89-M BH18 Implantation of diamond substrates
May1989Oct1990
anneals, SIMS, metallizations
ARO
DAAL03-91-C-0001 Modification and characterization of
Apr1991Apr1994
II-VI and III-V materials using ion beams
Martin Marietta
Device Implantation
1993-1996
ATM
contract
Diamond implantation
1994
ARO
DAAH04-95-C-0043 Electro-optics based on novel materials
Jun1995Jun1998
modification
DARPA ??
Diamond thermal management HSC/RSC Oct1997Oct1999
ARO
DAAG55-98-C-0045 Electro-optics based on novel materials
Jul1998Jun2001
Modification
ARO
DAA??
???
Univ. Florida
Sep2002Aug2005
WHAT INFORMATION IS IN THIS WORK
Resources for SIMS and Ion Implantation Technologies
New SIMS RSF data and ion implantation ranges and depth profiles for most
elements in metals (Be, Al, Ti, Ni, Cu, W, and Au)
New SIMS RSF data and ion implantation ranges and depth profiles for most
elements in insulators (dielectrics) (SiO2, Si3N4, Al2O3, LiNbO3, UO2)
New SIMS RSF data and ion implantation ranges and depth profiles for most
elements in wide bandgap materials (diamond (C), SiC, GaN, ZnSe,SnS)
New SIMS RSF dat and ion implantation ranges and depth profiles for most
lements in polymers (epoxy, PMMA, polyimide)
Measurement of electronic stopping powers for most elements in Si via
measurement of the maximum channeling range in the <110> direction of Si
and some GaAs
Measurement of the solid state and stoichiometric electron affinities of most of the
elements in Si and some GaAs via SIMS measurements
Some special features of this work include the results of studies or techniques
described below:
References to early work and early papers – 1963 to ~1988
Correlation between implantation damage/depth distributions and mobile impurity
depth distributions measured using SIMS and TEM for implanted Cr, Cu, Ag
SIMS mass spectra for many different kinds of materials
Shapes of deep <110> channeling profiles for nearly all elements channeled in Si
FIB (focused ion beam) depth profiles compared with random and channeled
Implantation profiles
Shallow vs deep implantation profiles and effect on SIMS RSFs for B, Ga, and As
A history of early ion implantation, including conferences, patents, news releases
ook, reviews, and papers
A history of early implanters
C-V and Pearson IV profile techniques
Ion beam mass analysis for implanter ion beams
SIMS for molecular ions
SIMS for multiple implants
MeV implantation and channeling
Amorphous vs crystalline implanted depth distributions
Experimentally measured moments of implanted depth distributions determined using a
Pearson IV fitting routine
Comparison of experimental ranges with calculated ranges uding TRIM and ISPC
Extended studies of implantation of Si and As including MeV energies
SIMS quantification
Cs molecular SIMS
DEFINITIONS
WSM represents Wilson, Stevie, and Magee, Secondary Ion Mass Spectrometry
[Wiley, New York, 1989]
E
is often used to represent element, O to represent oxygen, and M to represent
matrix, etc. when secondary ions are discussed
SIMS represents secondary ion mass spectrometry
RSF represents (SIMS) relative sensitivity factor, the calibration factor to convert
secondary ion signal (counts/sec) to atom density (cm-3), via the matrix signal
measured under identical instrument conditions
wrt
represents with respect to
Ion Implantation
Ion implantation is a versatile process that can introduce any element into any solid
material to any density under nonequilibrium conditions, irrespective of solid solubility, at
any temperature compatible with the material, and at depths that depend on the energy
capability of the equipment. The resulting damage to crystals is an issue and annealing is
used to remove as much of that damage as is compatible with the temperatre limitations of
that material.
Elements can be introduced in to materials using ion implantation that may alter the
electrical, optical, mechanical, magnetic or other properties of the material. Implantation is
a major technique used in the Si device and circuit industry for doping and other
processing steps; it is used less in III-V materials and device technologies and very little in
narrow bandgap II-Vi technologies because it is difficult to remove the damage (point
defects and various extended defect complexes) created by the energetic energy loss
processes that occur as the ions come to rest in crystalline materials, because of
temperature limitations of those material. High temperature materials are better
candidates for implantation processing , materials that include GaN.
There are many previous s and books about ion implantation, damage, and annealing.
See the references in this work.
SIMS
Secondary ion mass spectrometry (SIMS) is a surface analytical technique that is ideally
suited to measuring depth profiles of implanted and annealed materials. Effects of
annealing on the depth distributions of implanted species, unintentional impurities, and the
elements of substrate (matrix) materials themselves can be measured using SIMS. SIMS
analyses can be quantified accurately by using implanted standards of accurately know
fluence. Figure 1 illustrates such a quantification standard for K implanted in Si. A
quantification measure for SIMS called the relative sensitivity factor (RSF) is established
by setting the integral under the measured depth distribution equal to the accurately
measured fluence of the implant [time integral of the current density (adjusted for the
charge on the ion)]. This RSF can then be used at any later time to quantify impurity
densities by measuring the ratio of the intensity of the secondary impurity ions to the
intensity of the same matrix ion for which the RSF was measured1 – for instruments that
have time consistent properties, the matrix being one of the elements in any selected
material
.
Annealing and associated terminology
Annealing is a process often used with ion implantation – to reduce or remove the
damage or effects of damage caused in implanted crystalline materials during the energy
loss of energetic ions. In amorphous materials, damage has little meaning because the
atoms or molecules have little or no organized physical relative location.
Our Webster’s dictionary give four sub-definitions for the word “anneal,” all four of which
use temperature (elevated) in the definition. Therefore “thermal anneal” is redundant; the
word thermal is totally unnecessary. “Anneal” or “annealing” requires elevated
temperature. Therefore, we use “rapid anneal” here to describe short-time annealing
rather than the redundant term, often seen in the literature, rapid thermal annealing or
RTA. The term RTP or rapid thermal processing does not suffer from this criticism, so it is
used here. The common alternative to rapid annealing is furnace annealing. Rapid
annealing is often done using flash lamps of a variety of types.
Range Parameters Terminology
A discrepancy has occurred historically in the literature in the use of symbols
regarding the range parameters used in ion implantation, as follows: Originally Rp was
used for the most probable range, and Rm was used for the mean (median?) range. Later
Rp was used for the projected range (from LSS), or the first moment, , and Rm was used
for the range mode, or most probable range, or the depth of the peak of the depth
distribution or profile. Rp was then used for the range straggle or second moment, . We
use these latter definitions in this work. The third central moment is then 1, and the fourth
central moment is 2.
Random Equivalent Terminology
We use the term random orientation or random equivalent orientation as we first heard it
used, namely as any one of several orientations that produce the average Rutherford
backscattering signal that occusr between channeling dips [excluding the higher signal
shoulders (quasichanneling) that occur just before the dips]. One early orientation that was
believed to fulfill thios criterion was 7 or 8 degrees tilt ans 18 degrees azimuthal rotation or
“twist.” That is, 8 degrees tilt from the condition where the beam direction is normal to the
surface target surface and 18 degrees rotation of a flat from the line through the target
(wafer) about which the 8 degree tilt was made. For a <100> Si wafer, there are four
<110> flats, for example. This is a historical definition; more recent experimental studies
may have improved upon the definition. Another random condition was the <763> used by
Hofker in 1975. When the ion velocity becomes small ( the ion energy is small and/or the
ion mass is large), the critical angle for channeling becomes large, to the order of 5
degrees, and the tilt angle may better be increased to 10 degrees (or even larger). There
is a publication that indicates that the practical tilt angle should be twice the classical
Lindhard critical angle for channeling, in order to minimize unintentional channeling during
implantation [NBS Special Publication 400-49, 197]. There is a body of literature in which
the issue of tilt angle and the need for an angle larger than 7 degrees is discussed for Si
implants into GaAs.