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N D I meetingG.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 Dosimetercurrent availability
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%/20mins1cGy 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
2.1mm
20mm
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RF UNIT
POWERUNIT
SENSINGUNIT
ELECTRONIC UNIT
(VCO,TEMP COMP)
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)
Standard communication band for future implantable devices
Radiation
RF receiver
Proposed Monolithic In Vivo Dosimeter
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Proposed Monolithic In Vivo Dosimeter
Low power electronic
Radiation Sensor Antenna
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
1000μm
Thin film battery on the back side
Silicon chip
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V ~ 2.8mm3
V ~ 69.2mm3
Size comparison of the IVD
.22 Long Rifle bullet
Sicel IVD
STFC IVD
Proposed Monolithic In Vivo Dosimeter
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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
Feasibility study of monolithic in vivo dosimeter: technologically possible
Current activities:
Planned activities:
subject to positive CLASP outcome:• fabrication of monolithic test microdosimeter: radiation testing• interaction with commercial partners
In vivo Dosimetersummary
Feasibility study of monolithic in vivo dosimeter: technologically possible
Potential NDI activities:
development of [FG] MOS dosimetry for radiation monitoring
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Block diagram of a typical readout cell with typical power consumption per block.
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
GK(X+Y)X
G
GKXY
1
Y
Low power readout
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PvsgNvgsNP gmgmRRG
X
Y
Variation of the S-curve for the circuit of figure .. with change in floating gate NMOS threshold voltage.
Vth1 Vth2 Vth3 Vth4 Vth5
Low power readout
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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
Low power readout - summary
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NMOS
W=4;L=0.18
Floating Gate 10x10μm2
SiO2
Substrate GND
D
S TG
Radiation sensor from a standard single poly CMOS process used for NVM memory
P Substrate 2e16
P++
FG P++
N++
TG
NW 5.3x5μm2
Tunneling/Control Gate
0.3x0.2μm2
PW 3.3x3μm2
W contact
FOX SiO2
1μm
Poly FG 5e19
DNW 2e17
IPW 2e17
Thin SiO2
7nm
Backup - IVD C- Flash process
Radiation sensitivity:~ 20mV/rad@ Vds = 2V, Qfg = -3fCDR ~ 1Gy (10x10μm2 FG size)
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Backup - IVD On chip ANT evaluation
RF studies and on chip antenna fabrication
950
950
11W = 50
150
950
22 B
A set of antennas on chip are fabricated at MNTC (RAL) (PoC funding from Innovations, 2010) to evaluate A set of antennas on chip are fabricated at MNTC (RAL) (PoC funding from Innovations, 2010) to evaluate achievable RF range achievable RF range
The on chip antennas are then tested at RAL and UniBoThe on chip antennas are then tested at RAL and UniBo
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