1. Current status of the silicon strip sensor development in Korea
Introduction
Silicon Inner tracker configuration for ILC
Silicon strip sensors development
Beam test and radiation damage test
Prospect
H.J.Kim (KyungPook National U.)
For Korean silicon tracker collabortion
ACFA9, Feb. 6/2007

2. Silicon Tracker R&D (SiLC group)
SiD
GLD
LDC
VTX (FPCCD)
Barrel Inner tracker
Endcap Inner tracker
VTX
Intermediate tracker
Endcap tracker
VTX
Whole tracker

3. Inner Tracker in GLD
VTX IT
Beam Pipe IP
TPC
W-Si Cal

4. Concept of Silicon Strip Sensor
type
fabrication
readout DC
relatively simple
readout electronics is connected directly to the strips AC
relatively complicate
- coupling capacitors are made by separating strip implantation and metallization
- biasing resistors are made in poly-silicon
readout
fabrication
position
single-sided
relatively simple
1-dimensional
double-sided
complicate, low yield
2-dimensional
N-type silicon N+ P+
guard-ring
poly-silicon bias resistor
DC pad
AC pad
biasing-ring pad Al
SiO2
AC-type single-sided strip sensor
DC-type double-sided strip sensor

5. DC Double-sided Silicon Strip Sensor
guard-ring pad
N bulk pad
Readout pad
Dicing line
Hour-glass pattern on the p-side to reduce the capacitance in the double metal structure
~10nA/strip
<5μA/sensor
measured value
Vdep < 60V
expected value
~55V(~92V)
Id v.s. V
C v.s. V

6. Fabrication of AC/DC SSD
AC TRK1
P+width:200um
Al wdth:220um
AC TRK2
P+width:300um
Al wdth:320um
DC TRK1
P+width:400um
Al wdth:420um
DC TRK2
P+width:600um
Al wdth:620um
Poly-Si Resists
PIN diode
Test patterns
AC type
Pitch:500um
Channel:64
DC type
Pitch:1000um
Channel:32
AC1
AC2
DC2
DC1 AC
256ch
512ch DC
32ch
64ch
6-inch process
5-inch process
AC-coupled Single-sided Silicon Strip Detector
5-inch
6-inch
thckness(μm)
380
400
Area (μm2)
35000 × 35000
55610 x 29460
Effective area (μm2)
31970 × 31970
51264 x 25178
SiO2 layer thickness (nm)
1000
250
Polysilicon length (μm) 10 8
Polysilicon width (μm)
13500
480
sheet resistance(kΩ)
~25
~400
Type1
Type2
Number of strips 64
256
512
Strip pitch (μm)
500
100 50
Strip width (μm)
200
300
readout width (μm)
220
320 12

7. Electrical test of SSD Id v.s. V 1/C2 v.s. V
Electrical characteristic of each channel in one of the AC-SSD
~10nA/strip
<500nA/sensor
Id v.s. V
measured value
Vdep < 60V
1/C2 v.s. V

8. AC coupling capacitance
Coupling capacitance (Cc )
Target value : AC1 214pF / AC2 322pF
Measured value : AC1 177pF / AC2 257pF
Differences are due to different permittivity depending on SiO2 layer
And due to the limitation of SiO2 layer thickness in the our fabrication process.
AC2
AC1
Target value : 322pF
Target value : 214 pF
Probing for coupling capacitance measurement
Measured capacitances of the AC SSD

9. Biasing structure Result Test patterns Bias resistor structure
Purpose and advantage :
Isolation of each strip
Automatic biasing of total strip
total leakage current is measured easily with only one connection on each surface
Bias-ring Pad
DC Pad
Probing for Biasing resistance measurement
here, Rs=20 KΩ width=10 μm length=12700 μm
Result
Test patterns R1 R2 R3 R4
Target value : 25 MΩ
Resistances of various test patterns
The Bias resistance of the AC-coupled SSSD

10. Silicon Strip Sensor Summary
5-inch double-sided process
yields
type
DC-type
AC-type
single-sided
90%
80%
double-sided
< 30%
N/A
Type 1
Various patterns
Type 2
5-inch single-sided process
Al wdth:220um
P+width:200um
AC TRK1
Poly-Si Resists
Test patterns
Al wdth:420um
P+width:400um
DC TRK1
Al wdth:320um
P+width:300um
AC TRK2
Al wdth:620um
P+width:600um
DC TRK2
AC1
DC1
fabrication line
AC type
Channel:64
Pitch:500um
DC type
Channel:32
Pitch:1000um
line
DC-type
AC-type
5 inch
double/single-sided
single-sided
6 inch
single-sided (in progress)
8 inch
thickness ( 725 um, can be thinned ~500 um)
AC2
DC2
PIN diode
Test patterns
Test patterns
Test patterns
6-inch single-sided process AC
256ch AC
512ch AC
64ch DC
32ch AC
256ch DC
512ch

11. Radioactive source test block diagram
Photodiode sensor of HPK
Pre-amp.
Amp.
Discriminator
Trigger Sensor Pb Pb
Sensor
Pre-amp.
Amp.
DSO
90Sr source
Light-tight box
In this slide I will talk about the radioactive source test.
This is a block diagram of the experimental setup for a radioactive source test with the prototype Double-sided silicon strip sensor.
As you see, 90Sr, beta source is placed just below the silicon sensor
and lead collimator is placed between the silicon sensor.
A Hamamatsu photodiode sensor is used for trigger.
Instead of the front-end electronics, we used the pre-amp. and amplifier NIM modules for the source test.
Analog signal from the amplifier was connected into the analog input of the FADC board
and digital oscilloscope.
Trigger signal which go through the pre-amp, amp., and discriminator
is transmitted to the trigger input of the Flash ADC board (as you can see from the drawing).
We could also check the coincidence signals on the oscilloscope.
Trigger
512ch Double-sided Silicon Strip Sensor
FADC4VA
Xilinx PC
ADC

12. Source Test Measurement Result
This is a measurement result of the beta source test with the prototype double-sided silicon sensor.
Signal-to-noise ratio was measured to be about 25 which tells the quality of the sensor itself is good.
(At that time, we are not ready the front-end electronics.)
Signal-to-noise ratio is measured to be 25.0

13. Beamtest & Radiation damage test
Korea Institute of Radiological And Medical Science
Beam energy from 35 ~ 45MeV
Beam current from 0.2nA ~ few micro A

14. Front-end electronics for SSD (DC type)
VA interface
VA chip
SSD
hybrid
OpAmp.
VA Hybrid board
FADC4VA
This VA1 chip has 128 channels, and a low noise charge sensitive preamp, a shaper, and a sample and hold for each channel.
Analog signals are serially clocked out by control via a shift register.
VA Interface board
FADC4VA board
Xilinx chip on Flash ADC4VA board makes a control logic and distributes it to VA and ADC chip converts analog signal to digital signal.
Digital signal from ADC is sent to PC through USB2 bus for data analysis
Power supply to VA and silicon strip sensor
Logic converter for interfacing between VA and Xilinx

15. Block Diagram of Experimental Set-up for Beam Test
Collimator (Al)
Collimator (Pb)
Liquid Scintillator
Proton Beam Pipe
VA Hybrid
PMT HV
VA Interface
thin Cu windows
Amplifier
DSO
FADC4VA
Discriminator
Light-tight box
Gate & Delay generator
Trigger
Control PC (To outside)
Ethernet Hub PC

16. Liquid Scintillator and PMT for trigger
Experimental Set-up
collimator
Silicon strip sensor
Al light-tight box
Liquid Scintillator and PMT for trigger
USB2
VA1_prime2.3

17. Test results Simulated absorbed energy spectrum
of 37.5 MeV proton impinging onto
380 um silicon sensor
This problem is well understood : random trigger due to misalignment

18. Results of beam test : S/N
The SNR is defined as the ratio of the most probable energy deposit in the sensor to the noise RMS.
The estimated SNRs of channels 0 ~ 22 have large errors because of only few properly triggered events. Channels 23 ~ 31 show good SNRs of 164 ~ 67 for as 37.5 MeV proton, which corresponds to be 16.4 ~ 6.7 for a Minimum Ionizing Particle.

19. κ is “hardness factor” = D(E)/Dneutron(1MeV)
Radiation damage test
Irradiation
45 MeV proton beam from MC-50 cyclotron at KIRAMS fluence normalization based on NIEL scaling hypothesis
for different particles
for different energy ranges
Energy dependence on NIEL in silicon for different particle types and energies
The standard for particle fluence is to normalize all damage to the equivalent damage caused by 1 MeV neutron.
κ is “hardness factor” = D(E)/Dneutron(1MeV)

20. Radiation damage test results
Increase in leakage currents
Φeq=3.0×108
Φeq=1.6×109
Φeq=1.6×1010
Φeq=1.6×1011
Leakage currents as a function of bias voltage

21. Radiation damage effects
Fluence dependence of leakage current
Fluence independence of damage parameter
ROSE data
current related damage rate α is expected to be independent of irradiation
α can be used to monitor the particle fluence
current increase is strictly proportional to fluence
Damage induced bulk

22. More Beam Test at KIRAMS on 2007 :analysis ongoing

23. Beam Test at CERN on 2006 : analysis on going
150 GeV
electron beam

24. Summary and Prospect
Double sided silicon sensor, DC-type single sided silicon sensor and AC-type single sided silicon sensor was successfully produced and tested.
Beam test and radiation damage shows that developed sensor can be used for the ILC environment.
Radioactive source test and beam test showed that S/N ratio is good enough for the ILC environment.
Electronics R&D is under progress.