Transcript GiulioNDImeeting Dec10

N D I meeting
G.Villani
December,2010
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Outline
 Dosimetry
 New low power solutions for RO based upon LU effect
…
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In Vivo Dosimeter
current availability
20mm
2.1mm
 IVD from Sicel: FDA clearance in 09 for use in breast and prostate radio treatment (clinical studies available)
 0.4μm TOX MOSFET(RADFET)
 Hybrid design: separate RADFET ,readout and RF
 Power delivered via an external RF field, 15cm range
 Daily readings, unique 32bits tag
 20 to 50mV/Gy sensitivity up to 80Gy ( non linear, individual device calibration, in the MeV range)
 Thermal sensor for calibration only; angular dependence up to 6% @ 270° (ideally <30° off axes)
 Fade effect due to thermal detrapping of charge approx 2%/20mins
1cGy LSB, Total device errors ~ 5%, 2σ
 Operating frequency 133kHz, operating voltage of the implant 5V, backscattering technique (RFID tags)
An Implantable MOSFET Dosimeter for the Measurement of Radiation Dose in Tissue During Cancer Therapy , IEEE Sensor Journal, Vol. 8,
No.1, Jan 08
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Proposed Monolithic In Vivo Dosimeter
Radiation
SENSING
UNIT
RF
UNIT
ELECTRONIC UNIT
(VCO,TEMP
COMP)
POWER
UNIT
RF
receiver
 Proposed monolithic implantable In vivo dosimeter fabricated on the same silicon substrate
 Smaller
 Reliable
 Cheaper
 Fully integrated micro system < 1mm3 includes radiation sensor, readout, power unit and RF unit to transmit data
in the approved Medical Implant Communication Service band (MICS 402 – 405 MHz)
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 Standard communication band for future implantable devices
Proposed Monolithic In Vivo Dosimeter
Radiation Sensor
Antenna
Silicon chip
Low power electronic
Thin film battery
on the back side
1000μm
Layout Example of the proposed monolithic In vivo dosimeter
 CMOS technology 0.18μm allows integration of radiation sensors and RF, including antenna
 Power options include thin film battery on the back side or RF powering
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Proposed Monolithic In Vivo Dosimeter
.22 Long Rifle bullet
V ~ 69.2mm3
Sicel IVD
V ~ 2.8mm3
STFC IVD
Size comparison of the IVD
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In vivo Dosimeter
summary
Feasibility study of monolithic in vivo dosimeter: technologically possible
Current activities:
 Studies and characterization of on chip micro antenna for wireless
transmission in MICS band (PoC funding from Innovations Ltd.)
 CLASP proposal (Oct. 10) ~ 480K: report says ‘recommended for further
CLASP support’ need to understand what it means
Planned activities:
 subject to positive CLASP outcome:
• fabrication of monolithic test microdosimeter: radiation testing
• interaction with commercial partners
Potential NDI activities:
 development of [FG] MOS dosimetry for radiation monitoring
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Low power readout
X
K(X+Y)
Y
G
Block diagram of a typical readout cell with typical power
consumption per block.
Y  X K 
G
1 G
 Typical blocks found in a readout cell :
Voltage follower, Charge amplifier, Shaper,
Variable threshold comparator
 All these functional blocks could be
implemented using a Latch up based readout
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Low power readout
Y
X
 G  RP RN gmvgs  N gmvsg  P
Vth1
Vth2 Vth3 Vth4
Vth5
Variation of the S-curve for the circuit of
figure .. with change in floating gate NMOS
threshold voltage.
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Low power readout - summary
 Initial studies: some interesting results, a couple of papers
 No current activities: but probably justified in the context of generic
R&D for new detector development
Tools and facilities required from NDI group:
study and design efforts
Equipment and tools already available
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Backup - IVD C- Flash process
Floating Gate
10x10μm2
D
S
NW 5.3x5μm2
TG
SiO2
Tunneling/Control Gate
0.3x0.2μm2
PW 3.3x3μm2
NMOS
W=4;L=0.18
TG
Radiation sensor from a standard single poly
CMOS process used for NVM memory
Poly FG
5e19
Substrate GND
FG
P++
P++
N++
FOX SiO2
1μm
W contact
Thin SiO2
P Substrate
2e16
7nm
IPW 2e17
DNW 2e17
Radiation sensitivity:~ 20mV/rad
@ Vds = 2V, Qfg = -3fC
DR ~ 1Gy (10x10μm2 FG size)
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Backup - IVD On chip ANT evaluation
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5
0
9
5
0
1
2
1
5
0
W
9
=
5
05
3
B
0
RF studies and on chip antenna fabrication
A set of antennas on chip are fabricated at MNTC (RAL) (PoC funding from Innovations, 2010) to evaluate
achievable RF range
The on chip antennas are then tested at RAL and UniBo
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