Electron spin resonance centers associated with oxygen precipitates
in Czochralski silicon crystals
M. Koizuka
ULSI Development Division, Fujitsu Ltd., 1500 Mizono, Tado-cho, Kuwana-gun,
Mie Prefecture 511-0192, Japan
H. Yamada-Kaneta
Integrated Materials Laboratory, Fujitsu Laboratories Ltd., 10-1 Morinosato-Wakamiya,
Atsugi 243-0197, Japan
͑Received 25 February 2000; accepted for publication 28 April 2000͒
We have previously concluded that the oxygen-precipitate-associated defects that we identified by
the deep levels at E
v
ϩ0.30 eV and E
c
Ϫ0.25 eV were the P
b
centers generated in the interface
between the oxygen precipitates and the surrounding silicon crystal lattice ͓M. Koizuka and H.
Yamada-Kaneta, J. Appl. Phys. 84, 4255 ͑1998͔͒. In order to confirm this conclusion, we have made
electron spin resonance ͑ESR͒ measurements on the Czochralski-grown silicon crystals containing
the oxygen precipitates generated by the two-step anneals of 500 °C, 20 hϩ700 °C, 60 h. We have
found the ESR lines whose g values well coincide with those of the P
b
0
and P
b
1
centers. Thus it has
been clarified that the P
b
0
and P
b
1
centers are generated by the oxygen precipitation as well as by
the thermal oxidation. The present successful application of the ESR method to the annealed silicon
crystals suggests that it can be a useful tool to characterize the precipitation state of the oxygen in
silicon. © 2000 American Institute of Physics. ͓S0021-8979͑00͒06215-0͔
I. INTRODUCTION
In the device fabrication processes, we often control the
oxygen precipitation in the silicon wafers so as to obtain the
internal gettering power due to the oxygen precipitation and
the device-active region free from the defects. However,
once the oxygen precipitates are formed in the near-surface
region of the wafer, i.e., the device-active region, they can
generally cause fatal harm to the devices due to the deep
levels associated with them. In particular, the defects in the
interface region between the oxygen precipitates and the sur-
rounding silicon crystal lattice, if any, would be an origin of
such harmful deep levels. However, little has been known so
far regarding the existence and nature of the deep levels re-
lated to the interface between the oxygen precipitates and the
surrounding silicon lattice.
This work demonstrates that some types of defects asso-
ciated with the oxygen precipitates can be detected by means
of the electron spin resonance ͑ESR͒. From the g values of
the observed ESR lines, we show that these defects are iden-
tical to the so-called P
b0
and P
b1
centers
1,2
which are known
to be generated in the interface region between the silicon
substrate and thermally grown silicon dioxide film. The P
b
0
and P
b
1
centers are considered to be the dangling bond cen-
ters of the structures •SiϵSi
3
and •SiϵSi
2
O, respect-
ively.
2–4
Our previous study
5
using the deep-level transient spec-
troscopy ͑DLTS͒ revealed that the oxygen precipitates cause
the peaks ͑maxima͒ of the state-density distribution at E
v
ϩ0.30 eV and E
c
Ϫ0.25 eV which are very similar to those
6
of the P
b
centers. The defects causing these state-density
peaks exhibited further similarities to the P
b
centers:
5,7
͑1͒
Occurrence of the hydrogen passivation; ͑2͒ dependence of
the hydrogen passivation efficiency on the temperature of the
hydrogen incorporation anneal. The hydrogen anneals at the
higher temperature followed by fast cooling ͑quench͒ gives
the higher efficiency in passivation; ͑3͒ dependence of the
defect-generation efficiency on the temperature of oxygen
precipitation ͑or oxidation͒ anneal. The lower annealing tem-
perature gives the higher defect concentration. From these
similarities, we concluded
5
that the oxygen-precipitate-
associated defects we identified by the state-density peaks at
E
v
ϩ0.30 eV and E
c
Ϫ0.25 eV are the P
b
centers generated
in the interface region between the oxygen precipitates and
the surrounding silicon crystal lattice. However, confirma-
tion of our conclusion should be made by using the ESR by
which the P
b
centers have been identified. If our previous
conclusion is correct, it can be expected that we observe, for
the oxygen precipitates as well, the similar ESR lines char-
acteristic of the P
b
centers. This study aims to examine this
expectation.
II. EXPERIMENT
The samples were cut from a boron-doped p-type
Czochralski-grown silicon crystal with specific resistivity of
about 10 ⍀ cm. The interstitial oxygen concentrations (O
i
)
of the samples were determined by means of the Fourier
transform infrared absorption, according to the American
Standard for Testing and Materials F121-79 procedure. The
measured (O
i
) of the samples before the oxygen-
precipitation anneal was 1.57ϫ10
18
atoms/cm
3
. To generate
oxygen precipitates, the samples were subjected to the two-
step anneals consisting of the first step at 500 °C for 20 h and
the second step at 700 °C for 60 h. The reduction in (O
i
)
caused by this anneal was 0.70ϫ10
18
atoms/cm
3
in average.
JOURNAL OF APPLIED PHYSICS VOLUME 88, NUMBER 4 15 AUGUST 2000
17840021-8979/2000/88(4)/1784/4/$17.00 © 2000 American Institute of Physics