N19-2

2008 IEEE Nuclear Science Symposium Conference Record

Characteristics of the Irradiated Hamamatsu
p-Bulk Silicon Microstrip Sensors
K. Hara, H. Hatano, T. Meguro, S. Mitsui, T. Okuyama, M. Yamada, Y. Ikegami, T. Kohriki,
S. Terada, Y. Unno, K. Yamamura, and S. Kamada(float zone) wafers. We have fabricated p-bulk microstrip
sensors adopting technologies such as p-stop and p-spray for
strip isolation. Since the strip isolation concerns surface
conditions, the evaluation should be made on the sensors
fabricated from commercially available wafers and by one of
the companies capable of mass production, e.g., Hamamatsu
Photonics.
Our R&D fabrication has been made in three periods,
referred to ATLAS05, 06 and 07. The first ATLAS05 wasprocessed with a Hamamatsu 4" technology and using FZ and
MCl wafers. ATLAS06 was completed with a Hamamatsu 6"
I. INTRODUCTION
using FZ and MCl wafers, including Flp wafers where the
EVELOPMENT of radiation hard silicon microstrip sensors
defects are fewer than in normal Fl. A series of generalis essential for the future high luminosity experiments characterization measurements of these samples, both nonsuch as at the Super LHC where the radiation environment
irradiated and irradiated, is reported elsewhere [2]. ATLAS07
will be ten-fold increased compared to the LHC, the total
process is currently carried out in a wider collaboration [5]215
fluence reaching 1 x 10 I-MeV neqlcm [1]. High resistive nwhere Flp wafer is selected. In this paper, we report new
type Fl silicon is known to invert after receiving a fluence ofmeasurements on the annealing property of ATLAS06 samples,13
2
a few x 10 nlcm . The lifetime of the present LHC ATLAS
and punch-through (PT) evaluated on ATLAS06 test
microstrip sensors, p+-on-n sensors, is determined by the fullstructures. The PT property of PT implemented ATLAS07 is
depletion voltage increase when it exceeds the voltage limit ofalso described. These samples were irradiated with 70-MeV
the system. As a candidate of radiation hard microstrip sensors
protons up to a fluence of 5 x 10 15 I-MeV neqlcm2. The strip
for the Super LHC, we are investigating p-type bulk sensors,
isolation and PT properties are also evaluated while irradiatedn+-on-p sensors [2]. In such devices, the junctions stay at thewith 60Co y's at a similar rate foreseen at the Super LHC.
strip side throughout the lifetime, allowing the signals to beread out even at reduced bias once the full depletion voltage
II. SAMPLES AND IRRADIATION
reached the applicable limit. Sufficient charge collection is
The sample sensors are 1 cm x 1cm in area and 300 J.lm in
possible [2], [3] even after irradiation owing to the highelectron mobility that helps reduce the probability of carries thickness. The strip pitch is 80 J.lm for ATLAS05 and 06, andbeing trapped.
74.5 J.lm for ATLAS07. The wafer types, and p-stop and pThe microstrip sensors constructed at large scale have spray concentrations are summarized in Table I. The crystal
employed so far n-type wafers [4]. In p-type wafers, positive orientation is <111> only for 4" Fl; others are <100>. Various
charges inherently trapped in the oxide layer accumulate a strip isolation structures have been examined including AC
layer of mobile electrons in the silicon surface between the and DC field plates [2], but it turned out that they are notreadout strips, which may prevent their independent operation.
TABLE I
Availability of high quality p-bulk wafers has been also an
THE SAMPLES FOR THE THREE PROCESSES. FZ IS FLOAT ZONE (FZP HAS
FEWER DEFECTS) AND MCZ IS MAGNETIC CZOCHRALSKI. LISTED AREissue. High resistive p-bulk MCl (magnetic Czochralski)
CRYSTAL ORIENTATION, P-STOP AND P-SPRAY CONCENTRATIONS IN /cm2 .
wafers became available recently and are less costly than Fl

Abstract-Microstrip silicon sensors with p-bulk and n-readout
are investigated as a radiation hard device for the Super LHC
experiment. We evaluated the radiation hardness of the sensors
fabricated by Hamamatsu Photonics through irradiation with 70MeV protons up to the tluence of 5 x 1015 I-MeV neq/cm 2 and with
6OCO 15 at a rate foreseen at the Super LHC. The strip isolationand punch-through properties are characterized in detail.
Various strip isolation structures, p-stop, p-spray and both
combined, are examined. The results are compared amongcommercially available MCZ and two types of FZ wafers.

D

THE CONCENTRATION VALUES ARE INDICATIVE ONLY.

Manuscript received November 14, 2008. This research was partially
supported by the Ministry of Education, Science, Sports and Culture, Grant-inAid for Scientific Research A20244038, 2008 and C20540291, 2008
K Hara (e-mail: hara@)lep.px.tsukuba.ac.jp), H. Hatano, T. Meguro, S.
Mitsui, T. Okuyama (now at University of Tokyo), M. Yamada are with theInstitute of Pure and Applied Sciences, University of Tsukuba, Tsukuba,
Ibaraki 305-8571, Japan.
K Ikegami, T. Kohriki, S. Terada and Y. Unno are with the lPNS, HighEnergy Accelerator Research Organization, KEK, Tsukuba, Ibaraki 305-0801,
Japan.
K Yamamura, and S. Kamada are with Solid State Division, Hamamatsu
Photonics KK, Hamamatsu, Shizuoka 435-8558, Japan.

978-1-4244-2715-4/08/$25.00 ©2008 IEEE

Process

wafersP-stopID

P-stop LO/Mid[/cm2]ATLAS05
FZJMCZ
HPK4"<111>1<100>

20X 1012[lcm2]
5X 1012ATLAS06 FZplFZ/MCZ
HPK6"
<100>

12

12

ATLAS07
HPK6"

FZp
<100>

P-spray(P-stop)
2X 1012(2 X1012 )20X 10nla

lOX 1010x10 12

2X 10 12
(8 X 1012 )2X 1012(8 X 1012 )1686

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effective and only conventional p-stop structures, common andindividual, survived in ATLAS07. A common p-stop (calledZ3) is the isolation structure mainly discussed in this paper.
No structure (ZI) is also examined. P-spray at a fIXed
concentration of 2 x 10 12 / cm2 is added to some of ZI and Z3
samples. Hence, Z I with p-spray represents the performanceof the p-spray only. As shown in the table, the p-stop
concentration of p-spray samples is a half of HI p-stop
concentration.
The PT characteristics is first studied with test structures of
ATLAS06, and implemented in ATLAS07 where the distance
between the implant end to the bias-ring is set to 12 Jlm. In
ATLAS07, Z3 with a distance of 70 Jlffi is also fabricated forcomparison. They are referred to ATLAS07-ZI(PT), Z3(PT)and Z3, respectively. I
The proton irradiation was carried out using 70-MeV
protons of CYRIC, Tohoku University. The details of theirradiation and fluence calibration are described elsewhere [2].
During the irradiation the samples were biased at 100 V andcooled to -10°C. The irradiation took typically a few 10 min toa few hours, depending on the total fluence. The irradiatedsensors were kept refrigerated throughout except that they
were placed at 60°C for 80 min to complete the initial
annealing. Some samples were characterized during thisprocess and in extended period to study the annealing property.
The cobalt irradiation was made at Takasaki Laboratory of
JAEA. The isolation and PT properties are primarily
concerned to the surface conditions, e.g., the charge
accumulation in the oxide. Such an effect can be evaluated byionization radiation by 60Co y's as well. The dose rate wastargeted to exceed the expected maximum fluence at the Super
LHC. The ATLAS values [6] multiplied by 10 are 7.59 kGy
2annually (10 7 s) and 1.5 x 10 7 charged particles/cm s at theradius of 30 cm. If the charged particles are treated asminimum ionizing, this results in 15 Gy/h or 3 Gy/h for the
average. Taking a safety factor into account for the soft
particle contribution and the fact that we evaluate on 1 cm
square samples with respect to 10 cm square real sensors
where the surface charge may harder to move in the direction
along the strips, we set the initial dose rate to 100 Gy/h. The
irradiation at 100 Gy/h continued for 22 h. After a break for
0.5 h, the test was extended at 1 kGy/h for 5 h.
In total 16 samples were irradiated together with 60Co, see
Table II. For three types of ATLAS06 wafers, FZp, FZ and
MCZ, we tested ZI with and without p-spray, and Z3 (with HI
p-stop) with and without additional p-spray. For ATLAS07(FZp), Z3 and Z3(PT) with and without p-spray were
irradiated. The characterization was repeated every hour,
starting with I-V and isolation measurements up to 450 V bias,
and then PT measurement at a fIXed bias of 300 V. The 6OCosource was in place during the characterization. The bias
voltage between characterization measurements was kept at
300 V, except for the last one hour at 1 kGy/h where the bias
was raised to 450 V. The biases were provided by a single
source meter with 100 kO resistors inserted to individual

samples. The detector leakage current was evaluated in tum bymeasuring the voltage drop across the resistor with Keithley
2400. Two DC pads at neighbor were wire-bonded per sample
and the contacts were extracted outside the irradiation caveusing 12 m long twisted pair cables. One pair selected withrelays at a time were measured on the isolation between andone of the two against the ground (bias-ring) for PT
measurement. We relied on the dose rate based on thecalibration provided by the irradiation facility (15 and 55 cm
from the source for I kGy/h and 100 Gy/h exposures,
respectively). The induced current seen by the sensors under
test was checked to be consistent with the value expected fromthe nominal irradiation rate. The irradiation was made at room
temperature.
TABLE II
16 SAMPLES IRRADIATED WITH 60Co ys .ATLAS06 P-STOP ONLY SAMPLES
ARE HI DENSITYPROCESS

WAFER

NONE

P-STOPONLYATLAS06

FZ

Zl

Z3(HI)

Zl,Z3

MCZ

Zl

Z3(HI)

Zl,Z3

FZp

Zl

ATLAS07

FZp

III.

+SPRAY

Z3(HI)

Zl,Z3

Z3,Z3(PT)Z3,Z3(PT)RESULTS

A. Isolation: proton irradiated samples
The strips are electrically isolated at bias voltages
sufficiently high to remove the electron accumulation between
the strips. We characterized the isolation by applying fixedvoltages (+5V and -5V) between a pair of the DC pads andmeasuring the induced current, while changing the bias
voltage. The induced current is determined by the total
resistance, sum of two bias resistors in series and interstrip
resistance parallel to them. Fig. 1 summarizes the isolation of
proton irradiated ATLAS06 samples for various isolation
structures, ZI to Z4 [2]. The isolation voltage is defined by
the bias voltage where the measured current reaches theasymptotic value within 10% deviation. The nine graphs
correspond to the three wafer types, and two p-stop
concentrations (H and M) and p-spray in addition (P).
In each group, the curves are notably different for no p-stop
structure (Z 1) and others (Z2 to Z4). The isolation voltage of
ZI samples is low for small fluences below.....,5 x 10 14 n/cm2 for
FZp wafers and samples with p-spray. FZp wafers which havefewer defects behave better in isolation property than theothers at low fluence, but addition of p-spray to the otherwafers improves to a similar level. For a fluence exceeding. . ., 1 x 10 15 n/cm2, only the p-stop samples with highconcentration (HI) exhibit small isolation voltages. In general,
however, the isolation is achievable below the operation
voltage, typically 300 V, for all the samples.

I The zone structures are detailed in [2] for ATLAS05 and 06. For
ATLAS07 process, Z3 and Z3(PT) here are named Z4 and Z3, respectively.

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6 FzpP

300

.. ..

~

•. -+

100

o

6FzP

6FzH

200

....

-~,

.----....

,K"""""''O==~~::..L-...~........J: r'~,H . .-.

otl-.~~
1

10

10

100 I

100 I

10

Fluence (n/cm 2 )

100

Xl0

14

Fig. I, Strip isolation voltages [V] as a function of fluence, shown for 6" Fzwith fewer defects (FZp, upper), standard FZ (FZ, middle) and MCZ (Mc,lower). Results for four p-stop structures are shown, where Z 1 has no structure(H and M), or has p-spray only (P).

B. Isolation under continuous 60Co irradiation
The isolation described above was evaluated after theannealing was completed. The annealing time, however,concerns the recovery of the bulk damages and may not beappropriate for the surface damages. The isolation and PT
properties are primarily related to the latter.
We carried out in-situ evaluation of the isolation and PT
under 60Co irradiation. The characterization of isolation is thesame as described before, measure the induced current
applying +5 V and -5 V to one of the DC pads while the otherDC pad at neighbor at ground. Two voltage results werecompared to cross check the measurements: We obtained
consistent results from the two. The resistance corresponds tothe two bias resistors in series of about 2.5 MQ if nosignificant contribution of the interstrip resistance is present.
Fig. 2 shows a typical set of data, taken after 15 h irradiation at
100 Gy/h. Out of 16 samples, MCl II sample with p-spray
was disconnected from the system, since it showed a large
leakage current shortly after the irradiation started.

The curves can be grouped into three. All tested II (Flp andFl with and without p-spray, and MCl without p-spray)
samples showed most degraded characteristics among these.
The second group is Fl and MCl samples where the p-spray
is applied (the p-stop concentration is Mid); Fl and MCl
samples with HI p-stop and ATLAS07 are in the third groupwhich showed a most preferable characteristics. The sensors in
the first group should exhibit substantial cross talks since thebias was kept at 300 V. This needs to be verified with sensors
with readout connected.
The wafer difference is summarized in Fig. 3 where theisolation voltages are averaged over l3 samples. HereATLAS07 (Flp) data are shown separately. For all the wafers,
the isolation voltage starts increasing at around 1 kGy
accumulated dose. The break 0.5 h while switching to 1 kGy/hcontributed to lower the isolation voltage. The bias voltage
during the irradiation was 300 V except for the last one hour
where the bias was 450 V.
The curves for Flp wafer are shown individually in Fig. 4
including II samples. The HI p-stop and ATLAS07 Mid pstop behaved better in the 22 h exposure at 100 Gy/h. These
two samples also increased gradually at 1 kGy/h exposure. As
mentioned before, both II samples behaved worse than theothers.

o
Q)

tID

~
o

-100

>

c:

o

.~

]

-200
-300

-400
lkOy/h100 Gy/h

-500

o

6

8
Dose [kGy]Fig. 3. The isolation voltage averaged for Z3 samples as a function of
accumulated dose.

2::.

~ -100~c:8as -200

"0
.!
-100

-200

-300

-400

-300

-500

Bias [VJ-400

Fig. 2. Typical set of R-V curves for the isolation measurement, shown for
15 samples. This set is taken after 15 h at 100 Gy/h. PR refers to Z3 p-stop and
p-spray, Pstp to Z3 HI p-stop, Spray and NO refer to ZI with and without pspray, respectively.

The data at bias voltages below the full depletion show
additional components, but the data above 100 V areconsistent that the isolation is achieved as the voltage is raised.

-500

o

2

..

6

8
Dose [kGy]Fig. 4. The isolation voltages for FZp samples. The samples with p-spray
are shown in dotted curves with open marks. Two ATLAS07 Z3(PTP) samples,with Mid p-stop and p-spray, are overlapped each other, shown in crosses.

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Exposure at 1 kGy/h was made to evaluate if the isolation iscompletely lost at such a high rate or not. The both sets of data
indicate that the isolation degradation has a time constantprobably independent to the radiation rate. It is reported [7]that Hamamatsu n-bulk sensors for the ATLAS SCT show
degrade strip isolation when the bias voltage is lowered after a
substantial period of operation even if they are not exposed to
any radiation. The explanation is that holes created in a longtime operation are arranged such that the isolation is achievedat the voltage a few 10 V below the operation voltage. Oncethe voltage is lowered, holes start to re-arrange to fit in the
new field. The isolation turns to be degraded during thisrearrangement. Since the mobility of holes in the oxide issmall, the re-arrangement takes days to weeks especially at
low temperature. The present situation under 60Co irradiation
may be similar. Unless the isolation is completely lost by theradiation induced current, the isolation voltages may besustained to be slightly smaller than the operation voltage.
Examination using real size sensors with readout electronics
connected is required in order to discuss such an effectqualitatively in terms of noise and charge collection
performance.
C. Punch throughIn a rare case of accelerator beam loss spraying around thecore of the beam, the silicon detector may receive intensive
flux of protons. If the signal current boosts up the implantvoltage too large with respect to the oxide voltage rating, theoxide will be broken, resulting the particular channel and most
likely some neighbors to become noisy, or in worst case thewhole sensor will be permanently damaged. Such a large
voltage could present due to the finite resistance of the bias
resistor (about 1.5 MO) and also of the implant resistance [8].
The punch through (PT) between the n+ strip end to the biasring (n+) can lower the risk against such beam splash if it
occurs at a voltage smaller than the oxide rating 100 V.
We irradiated ATLAS06 test structures where the distance
between n+ implants was varied to 8, 12 and 20 J.1m.
Structures with a p+ implant interleaving between are also
examined, simulating the p-stop structure surrounding the strip.
The structures are named either nG or nCG, where n denotes
the distance in J.1rn, C is with a p-stop electrode between. The
PT characteristics is evaluated by changing the test voltage
applied to one of the electrodes, and measuring the induced
current across. The data were taken for a set of bias voltages.
The induced current increases linearly with the test voltage forsmall voltages, corresponding to the bias resistance, andbecomes larger at higher voltages when the PT is turned on.
The tum-on voltage is defined as the test voltage where themeasured resistance between the electrodes dropped to 500 kO.
A typical set of data are plotted in Fig. 5 for non-irradiated andtwo proton irradiated FZ samples. The 400 V data for MCZ
where the deviation was the largest are also plotted as acomparison. The difference is not large among different wafer
types and p-sprayed or not. A distance of 8 J.1rn is too close forsmall PT voltages at pre-irradiation and --6 x 10 14 n/cm2, while
12 IJm and 20 IJm seem to be appropriate. It is shown that theirradiation will reduce the PT voltages.

The PT structure is implemented in ATLAS07 where a
distance of 12 J.1m was chosen. They are named ZI(PT) andZ3(PT). Z3 with a distance of 70 J.1m is also included forcomparison.
(a) pre-irrad

2:.,50
0)

~40

=

4

~;~ b) 5.8x1a /cm 2 --Fl00--F200----..,-F300

:.,

~F400

-.-- F400

•

M400

F300

>

.c

i~-=-==-~

0) 30

:::I

2

·It

~ 20
.c

_.

u

-~..----.--.

.,___.>t::------i:; - t:

...

-L

---~~---~-..---...

IC: 10

:::I
Q.

OOG

12G

200

12CG 2CXXl

12G

200

1203

2003

OOG

12G

200

12CG

20CG

Fig. 5.

The punch-through voltages for non-irradiated and samples
i~adiated with protons to two fluence values. The horizontal is the gap
dIstance between the ends of two n+ strips with (C) or without a p+ electrodebetween. The data are at different bias voltages from 100 V (diamonds) to 400
V (circles) for standard FZ, and at 400 V for MCZ.

Fig. 6 shows the measured current in the PT evaluation forthe samples irradiated with protons to 2.1 x 10 14 and 2.3 x 10 15
n/cm2. The test voltage was applied to the DC pad while thebias-ring set at the ground, with the bias fixed at 300 V. The
data are compared between Z 1(PT), Z3(PT) and Z3 fromATLAS07, with and without p-spray. The Z 1 samples show asimple PT characteristics with PT taking place below 20 V in
the negative voltage range. The shape is slightly disturbed ifpspray is added. In the positive range, the PT voltage increases
with radiation and was not observed below 100 V for the
1.3 x 10 15 n/cm2 sample. The positively charged oxide layer
helps to lower the PT voltage in the negative region, as seen in
the test structure, which in tum prohibits the PT to occur in thepositive side. Since the beam splash produces negative current,
PT should tum on in such a case. The PT of Z3(PT) takes
place in two steps, first gradually with the test voltage andsuddenly at some voltage. Such a behavior was not seen in thetest structure. The PT occurrence is prohibited in the sample
most probably due to that the common p-stop is by far solid
due to a larger total area compared in the test structure.

'<E

i 0 0 I "'.liI:.iI;.lU--......

t-"-·-

J-02,,·;~:~i~(b)1.3X101~Cm2~ \o40

TestVoItap[V]

40

.

i~"

1:]'9.:

60\ tiJ.,i ..

""'d>

80

Test Voltage [V]Fig. 6. The induced current as a function of the test voltage (punch-throughmeasurement) after (a) 2.1 x 1014 nlcm 2 and (b) 1.3 x 1015 nlcm2 . The samples
are ATLAS07 (FZp) with (squares) ZI (PT), (circles) Z3(PT) and (triangles)
Z3. Samples with p-spray are shown in open marks and dotted curves. The bias
voltage is 300 V. The line labeled "infmite" in the negative side corresponds tothe case where no PT takes place.

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Fig. 7 is an evolution of R-V curves with time showing thedata before irradiation, after 1 h at 100 Gy/h, after 22 h at 100
Gy/h, and after additional irradiation of 5 h at 1 kGy/h. The
data were taken while irradiated and with a bias of 300 V. The
PT characteristics became similar for the two samples,
although they showed different initially.
ATLAS07 P-stop + Pspray(PTP)

ATLAS07 P-stop (PTP)

0.5
OL:=::::::::~~~--.Jl-----.J_-----i

o

20

40

60
80
100 0
Test Voltage [V)

20

40

60

80
100
Test Voltage M

Fig. 7. The strip to bias-ring resistance as a function of the test voltage forZ3(PT) samples (left) without and (right) with p-spray. The data are measured
while irradiated with 6OCO with the bias was kept at 300 V.

D. Annealing
Studying the annealing of irradiated sensors is important for
detector operation and maintenance points of view. For n-bulk
sensors where the property is well studied, the effective
impurity concentration decreases at first, and then increases.
The time scale is dependent on the temperature. The minimum
is at approximately 80 min at 60°C temperature.
The study is carried out for the p-bulk sensors irradiated to
2 x 10 14 n/cm 2. The full depletion voltage was evaluated bothby C-V measurement and by charge collection measurement
using an infrared laser. The results of the full depletion voltage
evolution are summarized in Fig. 8. The p-bulk sensors arefound to exhibit similar annealing property to n-bulk sensors.
Among these, the MCZ shows a slightly quicker evolution
with time, after the minimum is experienced. The strip
isolation voltages were also measured, which showed todecrease monotonically with time.
1200

1.8E+13~ 10001.6E+13
1.4E+13

CD

C)

to

~
>

c:

.2

Q)
Q.
CD
'"0

"3

LL

800

1.2E+13
1.0E+13

600
400
200
0
10

100

1000

punch-through properties after proton irradiation and during a
low dose rate 60Co irradiation. The results are compared
between three types of wafers and p-stop and p-spray
configurations. FZp wafers which have fewer defects thanstandard FZ are selected for the current sensor process
ATLAS07.
The strip isolation is achieved reliably with p-stop of 2
x 10 13 /cm2 for proton irradiation exceeding 10 15 n/cm2 andduring 60Co irradiation at a level foreseen at the Super LHC.
The strip isolation voltage increases under irradiation,
reaching the value close to the operation voltage for the
samples with lower density p-stop with or without p-spray.
The influence of such increased isolation voltage to thedetector performance needs to be examined with readout
electronics connected through the achievable signal and noise
figures.
The punch through protection was implemented in the
ATLAS07 process. The punch through occurs at voltages
higher than expected from the test structure for the samples
where p-stop electrodes interleave between the n+ electrodes.
REFERENCES
[1]

[2]

[3]

G. Casse et aI., "Response to minimum ionising particles of ptype substrate silicon microstrip detectors irradiated withneutrons to LHC upgrade doses", Nucl. Instr. Methods A581
(2007) 318~ M. Minano et aI., "Characterization of irradiateddetectors fabricated on p-type silicon substrates for super-LHC",
Nucl. Instr. Methods A583 (2007) 33.

[4]

LHCb VELa replacement employs nf-on-p sensors in part, see A.
Affolder et al., "LHCb-VELO module production with n-side read-out
on n- and p-type silicon substrates", Nucl. Instr. Methods A583 (2007)
18.
See, for example, Y. Unno, ATLAS Tracker Upgrade Meeting, Nov 3-7,
2008, NIKHEF, The Netherlands.
The ATLAS Collaboration, G. Aad et al. "The ATLAS Experiment at the
CERN Large Hadron Collider", JINST 3 (2008 ) S08003.
Y. Nakamura et aI., "Anomolous IV behavior of ATLAS SCT microstrip
sensors", NucI. Instr. Methods A575 (2007) 353.
K. Hara et aI., "Beam splash effects on ATLAS silicon microstrip
detectors evaluated using l-W Nd:YAG laser", Nucl. Instr. Methods
A541 (2005) 15.

C")

[5]

~

[6]

E

~

'iii
c:

[7]

~

[8]

CD
'"0

8.0E+12 jQ.
6.0E+12 .!;Q)
4.0E+12 >:g
2.0E+12~
O.OE+OO w
10000 100000

I. Dawson, "Radiation background simulations and measurements for
ATLAS at the SLHC", talk given at ATLAS Upgrade Workshop,
Valencia, Dec 2007. The total dose is evaluated as 0.9 x 1015 n/cm 2 at theradius of 30 cm taking a safety factor of two for integrated luminosity of3000 fb·l.
K. Hara et al., "Development of Radiation Hard N-on-P Silicon
Microstrip Sensors for Super LHC", IEEE 2007 Nuclear Science
Symposium and Medical Imaging Conference, Conference Record N 15245, Oct. 27-Nov. 3,2007, Honolulu, Hawaii.

Elapsed time @60oC (min)Fig. 8. The evolution of full depletion voltage as a function of elapsed time
for the annealing temperature of 60°C The data are shown for the three wafer
types.

IV.

SUMMARY

We have evaluated characteristics of Hamamatsu p-bulk
microstrip sensors with emphasis on the strip isolation and1690

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