MINIATURIZED, LOW POWER FGMOSFET RADIATION SENSOR AND WIRELESS DOSIMETER SYSTEM
First Claim
1. A FGMOSFET radiation sensor comprising:
- a substrate comprising a device well;
a source and a drain, separated by a channel region, defined in the device well;
a floating gate extending over the channel region and separated therefrom by a gate dielectric layer, and an extension of the floating gate extending over a field dielectric layer adjacent the device well;
a charge injector means defined in the substrate underlying another part of the floating gate and separated from the floating gate by a gate dielectric layer; and
another dielectric layer and an electrostatic shielding layer extending over the floating gate.
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Abstract
A miniaturized floating gate (FG) MOSFET radiation sensor system is disclosed, The sensor preferably comprises a matched pair of sensor and reference FGMOSFETs wherein the sensor FGMOSFET has a larger area floating gate with an extension over a field oxide layer, for accumulation of charge and increased sensitivity. Elimination of a conventional control gate and injector gate reduces capacitance, and increases sensitivity, and allows for fabrication using standard low cost CMOS technology. A sensor system may be provided with integrated signal processing electronics, for monitoring a change in differential channel current ID, indicative of radiation dose, and an integrated negative bias generator for automatic pre-charging from a low voltage power source. Optionally, the system may be coupled to a wireless transmitter. A compact wireless sensor System on Package solution is presented, suitable for dosimetry for radiotherapy or other biomedical applications.
34 Citations
21 Claims
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1. A FGMOSFET radiation sensor comprising:
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a substrate comprising a device well; a source and a drain, separated by a channel region, defined in the device well; a floating gate extending over the channel region and separated therefrom by a gate dielectric layer, and an extension of the floating gate extending over a field dielectric layer adjacent the device well; a charge injector means defined in the substrate underlying another part of the floating gate and separated from the floating gate by a gate dielectric layer; and another dielectric layer and an electrostatic shielding layer extending over the floating gate.
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2. A radiation sensor comprising:
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a matched FGMOSFET pair comprising a sensor FGMOSFET and a reference FGMOSFET on a common substrate, each FGMOSFET comprising a device well region of the substrate having defined therein a source and a drain separated by a channel region, a gate oxide overlying the channel region and a floating gate formed thereon, and the sensor FGMOSFET further comprising an extension of the floating gate extending over an adjacent field dielectric region; and a respective charge injector means associated with each floating gate and separated therefrom by a gate dielectric layer; and another dielectric layer and a shielding layer overlying the floating gates. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A method of measuring a radiation dose using a radiation sensor comprising a matched pair of FGMOSFETs, the pair comprising a sensor FGMOSFET and a reference FGMOSFET each having similar channel widths and channel lengths, and the sensor FGMOSFET having a larger area floating gate comprising an extension of the floating gate overlying a field dielectric layer, and comprising the steps of:
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pre-charging floating gates of each of the sensor and reference FGMOSFETs to a predetermined value Vp; exposing the FGMOSFETs to radiation, and monitoring a change in differential channel current of the sensor and reference MOSFETS. - View Dependent Claims (20)
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21. A method according to 20 further comprising coupling said output voltage indicative of radiation dose to an input of an RF oscillator transmitter for encoding and real-time wireless transmission of a signal indicative of radiation dose.
Specification