Rapid isothermal annealing of As-, P-, and B-implanted silicon Page: 4,162
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Rapid isothermal annealing of As-, P-, and B-implanted silicon
S. R. Wilson, W. M. Paulson, and R. B. Gregory
Semiconductor Research and Development Laboratories, Motorola, Incorporated, Phoenix, Arizona 85008
A. H. Hamdia) and F. D. McDaniel
Department of Physics, North Texas State University, Denton, Texas 76203
(Received 18 November 1983; accepted for publication 21 February 1984)
Single-crystal silicon wafers have been implanted with As, P, and B to doses of 1 X 1013-1 X 10'6/
cm2 and given a transient anneal using a Varian IA-200 Rapid Isothermal Annealer. The system
uses infrared radiation to heat the wafers to temperatures in excess of 1000 C for times on the
order of 10 sec. Sheet resistance and Hall measurements have been used to determine the effect of
the anneal on the electrical properties of the wafers. Rutherford backscattering and secondary ion
mass spectroscopy have been used to measure lattice damage and dopant profiles before and after
annealing. As and P are lost during the anneal unless the wafer is capped. Complete activation can
be achieved with very little dopant diffusion. Residual damage is minimal in (100) oriented wafers
that had been implanted with As. However, for (111) wafers damage is less in (111) wafers
implanted to doses >5.0X 10'S/cm2, than in (111) wafers implanted to doses c5.0X 10'5/cm2.
The diffusion of As during this transient anneal has been modeled using a concentration enhanced
diffusion coefficient and the wafer temperature profile obtained from an optical pyrometer.
PACS numbers: 61.70.Tm, 81.40.Ef, 61.70.Wp, 61.80.Jh
As integrated circuits increase in complexity, it be-
comes extremely important to reduce device dimensions in
order to increase circuit speed. However, as device dimen-
sions shrink it becomes necessary to precisely control dopant
profiles. The initial profiles can be generated fairly precisely
by ion implantation. However, each high temperature pro-
cess step [implant activation and anneal, silicide formation,
phosphosilicate glass (PSG) reflow, etc.] which occurs subse-
quent to the implant step can possibly cause dopant diffu-
sion. This can increase short-channel effects in metal-oxide-
semiconductor (MOS) circuits and cause emitter-collector
shorts in bipolar circuits if the total diffusion length becomes
comparable to the device dimensions. The desire to accura-
tely control dopant diffusion during high-temperature pro-
cess steps has led to considerable research activity in high-
temperature transient annealing techniques. Several
researchers have used both pulsed and cw lasers and electron
beams to anneal ion implanted dopants, react silicides, and
produce PSG reflow.-4 For both the laser and electron beam
sources, all of the energy is absorbed in the near surface re-
gion, producing a surface temperature of 900 C or greater
for times of a few milliseconds in the cw case. This is suffi-
cient for recrystallization of implanted amorphous silicon to
occur, but dopant diffusion is insignificant. The pulsed beam
annealing will cause the surface layer to melt if the energy
density is large enough. Any impurities in the molten layer
will be redistributed by liquid phase diffusion and liquid-
solid segregation effects will occur as the molten layer solidi-
fies.5 These beam annealing techniques have encountered
severe problems such as optical coupling with oxide layers
and stresses due to thermal gradients when applied to actual
devices and circuits. To overcome some of the effects of thin-
a) Present address: Applied Physics Dept., California Institute of Technolo-
gy, Pasadena, CA.
film interferences and temperature gradients, researchers
have developed large area incoherent energy sources to per-
form rapid isothermal annealing. In this technique the entire
wafer is heated to 900 *C or greater for times on the order of
10 sec.6 High intensity arc lamps,7-9 raster scanned electron
beams, 'o and graphite strip heaters" have been used as ener-
gy sources. Varian has developed a system for performing
rapid isothermal annealing using infrared radiation from a
resistively heated sheet of graphite. The anneal occurs in
vacuum so that essentially all of the energy transfer is by
radiation. Since infrared radiation is weakly absorbed in Si,
the temperature rise is essentially uniform throughout the
bulk of the wafer and thermal gradients are minimal. Due to
the fact that the radiation is incoherent, the application of
this technique to annealing circuits and devices is not limited
by thin-film interference effects as is the case with lasers.
Preliminary results using this technique to anneal ion im-
plants and to perform other high temperature processing
steps have been reported by Wilson et al.,12-14 Fulks et al.,'5
and Downey et al.'6 In this paper we will present additional
data obtained by rapid isothermal annealing of B, As-, and
P-ion implanted wafers. For completeness some results
which have been presented previously2-14 will be repeated
in this paper.
II. SAMPLE PREPARATION
Three-in. Czochralski (CZ) silicon wafers were used as
substrates throughout these experiments. To evaluate isoth-
ermal annealing of ion implanted material, both (100) and
(111) wafers were implanted with 75As, 31P, or "B to doses
ranging from 1.0 X 10"3 to 1.0 X 10'6/cm2. The n-type wafers
had resistivities of 1-512 cm and thep-type wafers had resis-
tivities of 7-17 12 cm.
The annealer has been described previously.'6 The wa-
fers in these experiments were annealed for exposure times
@ 1984 American Institute of Physics 4162
4162 J. Appl. Phys. 55 (12), 15 June 1984
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Wilson, Scott R.; Paulson, W. M.; Gregory, R. B.; Hamdi, A. H. & McDaniel, Floyd Del. (Floyd Delbert), 1942-. Rapid isothermal annealing of As-, P-, and B-implanted silicon, article, June 15, 1984; [College Park, Maryland]. (digital.library.unt.edu/ark:/67531/metadc139472/m1/1/: accessed December 16, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT College of Arts and Sciences.