Miniaturized, low power FGMOSFET radiation sensor and wireless dosimeter system
First Claim
1. A radiation sensor comprising:
- a substrate comprising a device well;
a first source and a first 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 defined in the substrate, underlying a portion of the floating gate, and separated from the floating gate by the gate dielectric layer, a charge injector source and a charge injector drain being coupled together; and
a shield 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.
17 Citations
21 Claims
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1. A radiation sensor comprising:
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a substrate comprising a device well; a first source and a first 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 defined in the substrate, underlying a portion of the floating gate, and separated from the floating gate by the gate dielectric layer, a charge injector source and a charge injector drain being coupled together; and a shield dielectric layer and an electrostatic shielding layer extending over the floating gate. - View Dependent Claims (2, 3)
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4. A radiation sensor comprising:
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a matched field effect transistor pair comprising a sensor transistor and a reference transistor on a common substrate, each of the sensor and reference transistors 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 transistor further comprising an extension of the floating gate extending over an adjacent field dielectric region; a respective charge injector associated with each floating gate and separated therefrom by a gate dielectric layer, a source and a drain of each charge injector being coupled together; and a shield dielectric layer and a shielding layer overlying the floating gates. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A radiation sensor comprising
a matched field effect transistor pair comprising a sensor transistor and a reference transistor on a common substrate, each of the sensor and reference transistors 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 transistor further comprising an extension of the floating gate extending over an adjacent field dielectric region; -
a respective charge injector associated with each floating gate and separated therefrom by a gate dielectric layer; a shield dielectric layer and a shielding layer overlying the floating gates; and signal processing circuitry that detects a change in an operating parameter indicative of radiation dose, wherein the signal processing circuitry comprises circuitry that applies a bias to and monitors a differential drain current of the sensor and reference transistors. - View Dependent Claims (16, 17, 18, 19, 20, 21)
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Specification