Radiation dosimeter

• US 5,949,075 A
• Filed: 08/26/1997
• Issued: 09/07/1999
• Est. Priority Date: 08/26/1997
• Status: Expired due to Term

• Current Assignee: Citizen Holdings Co., Ltd.
• Original Assignee: Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Inventors: Kishi, Toshiyuki
• Primary Examiner(s): Hannaher, Constantine
• Assistant Examiner(s): Israel, Andrew
• Application Number:
  US08/917,705
• Time in Patent Office: 742 Days
• Field of Search: 250/370.07, 250/370.05
• US Class Current: 250/370.07
• CPC Class Codes: G01T 1/026 Semiconductor dose-rate meters

Abstract

A radiation dosimeter including a series circuit of an MONOS semiconductor and a resistor or an MOS or MONOS semiconductor device whose channel conductivity type is opposite from that of the first said MONOS semiconductor device. The MONOS semiconductor device is an electrically rewritable non-volatile memory cell having a gate insulating film consisting of a tunnel oxide film, a silicon nitride film and a top oxide film. The resistor is made of polycrystalline silicon which is little affected by exposure to radiation. The series circuit is connected between a source voltage and ground (GND) and a detection signal is obtained from the connection point between the members of the series circuits.

Claims

1. A radiation dosimeter comprising an MONOS semiconductor and a resistor connected in series between a source voltage and ground (GND), said MONOS semiconductor device being an electrically rewritable non-volatile memory cell having a gate insulating film consisting of a tunnel oxide film, a silicon nitride film and a top oxide film, and a detection signal being obtainable from a connection point between the MONOS semiconductor device and the resistor.

2. A radiation dosimeter according to claim 1, wherein the resistor is constituted of polycrystalline silicon whose resistance value is little changed by exposure to radiation.

3. A radiation dosimeter according to claim 1, further comprising a pulse generator and a NAND circuit, the NAND circuit receiving a pulse signal generated by the pulse generator and the detection signal as input and outputting a detection signal from an output terminal thereof.

4. A radiation dosimeter according to claim 1, further comprising an inverter which inverts and outputs the detection signal.

5. A radiation dosimeter according to claim 1, further comprising:

a control circuit including a power circuit for supplying the source voltage, a circuit for effecting rewrite of the MONOS semiconductor device and a circuit for detecting change in the detection signal, and

a shielding wall for shielding the control circuit from radiation.

6. A radiation dosimeter according to claim 5, wherein the control circuit further comprises an arithmetic circuit which calculates radiation dose from the detection signal, causes the circuit for effecting rewrite of the MONOS semiconductor device to effect rewrite of the MONOS semiconductor device when the calculated dose reaches a preset value and calculates total radiation dose from the number of rewrites.

7. A radiation dosimeter comprising an MONOS semiconductor and an MOS semiconductor device whose channel conductivity type is opposite from that of the MONOS semiconductor device connected in series between a source voltage and ground (GND), said MONOS semiconductor device being an electrically rewritable non-volatile memory cell having a gate insulating film consisting of a tunnel oxide film, a silicon nitride film and a top oxide film, and a detection signal being obtainable from a connection point between the MONOS semiconductor device and the MOS semiconductor device.

8. A radiation dosimeter according to claim 7, further comprising a pulse generator and a NAND circuit, the NAND circuit receiving a pulse signal generated by the pulse generator and the detection signal as input and outputting a detection signal from an output terminal thereof.

9. A radiation dosimeter according to claim 7, further comprising an inverter which inverts and outputs the detection signal.

10. A radiation dosimeter according to claim 7, further comprising:

a control circuit including a power circuit for supplying the source voltage, a circuit for effecting rewrite of the MONOS semiconductor device and a circuit for detecting change in the detection signal, and

a shielding wall for shielding the control circuit from radiation.

11. A radiation dosimeter according to claim 10, wherein the control circuit further comprises an arithmetic circuit which calculates radiation dose from the detection signal, causes the circuit for effecting rewrite of the MONOS semiconductor device to effect rewrite of the MONOS semiconductor device when the calculated dose reaches a preset value and calculates total radiation dose from the number of rewrites.

12. A radiation dosimeter comprising a first MONOS semiconductor and a second MONOS semiconductor device whose channel conductivity type is opposite from that of the first MONOS semiconductor device connected in series between a source voltage and ground (GND), the MONOS semiconductor devices being electrically rewritable non-volatile memory cells each having a gate insulating film consisting of a tunnel oxide film, a silicon nitride film and a top oxide film, and a detection signal being obtainable from a connection point between the first and second MONOS semiconductor devices.

13. A radiation dosimeter according to claim 12, further comprising a pulse generator and a NAND circuit, the NAND circuit receiving a pulse signal generated by the pulse generator and the detection signal as input and outputting a detection signal from an output terminal thereof.

14. A radiation dosimeter according to claim 12, further comprising an inverter which inverts and outputs the detection signal.

15. A radiation dosimeter according to claim 12, further comprising:

a control circuit including a power circuit for supplying the source voltage, a circuit for effecting rewrite of the MONOS semiconductor devices and a circuit for detecting change in the detection signal, and

a shielding wall for shielding the control circuit from radiation.

16. A radiation dosimeter according to claim 15, wherein the control circuit further comprises an arithmetic circuit which calculates radiation dose from the detection signal, causes the circuit for effecting rewrite of the MONOS semiconductor devices to effect rewrite of the MONOS semiconductor devices when the calculated dose reaches a preset value and calculates total radiation dose from the number of rewrites.