Variable metal multi-gate metal oxide semiconductor capacitor radiation sensor for improved gain and tissue equivalence

Patent metadata

Field	Value
Publication number	US-9927531-B2
Application number	US-201514870298-A
Country	US
Kind code	B2
Filing date	Sep 30, 2015
Priority date	Oct 17, 2014
Publication date	Mar 27, 2018
Grant date	Mar 27, 2018

Abstract

A method and apparatus is disclosed for differentially altering the radiation response across multiple MOSCAP sensors by placing different thin gate materials with different atomic numbers on a series of MOS-based radiation sensors. The secondary electrons created in high-atomic weight materials (such as gold) at lower incident photon energy levels enable a tissue equivalent radiation response and radiations source identification/differentiation. This is a desirable alternative to using filters with different coefficients across a series of MOSCAP radiation sensor which will attenuate the signal and degrade the device form factor. The method and apparatus disclosed achieves the same functionality but with inherent gain instead of attenuation, thus increasing sensitivity. This will improve the minimum resolvable dose for x-rays and low-energy gammas (high-energy gammas will remain the same), and produces a response that can distinguish the energy level of incident radiation photon.

First claim

What is claimed is:

1. A method of determining the energy of incident radiation, the method comprising:
comparing a plurality of signals induced by the incident ionizing radiation from two or more metal oxide semiconductor capacitors (MOSCAPs) having radiation-sensitive gate terminals with different radiation sensitivities dependant upon the material composition of the gate terminal and the energy of the incident radiation, to determine the energy of the incident radiation.

2. The method of claim 1 , wherein the radiation sensitivity of a gate terminal is based on additional secondary electrons produced by radiation passing through the gate composition material.

3. The method of claim 1 , wherein the gate terminals of at least two MOSCAPs comprise materials of different compositions having different atomic numbers.

4. The method of claim 3 , wherein there are at least three MOSCAPs, of which at least one MOSCAP having a gate terminal comprising a low atomic number composition material, at least one MOSCAP having a gate terminal comprising a medium atomic number composition material, and at least one MOSCAP having a gate terminal comprising a high atomic number composition material.

5. The method of claim 4 , wherein the gate terminal of at least one of the MOSCAPs comprises aluminum, wherein the gate terminal of at least one of the MOSCAPs comprises molybdenum, and wherein the gate terminal of at least one of the MOSCAPs comprises gold.

6. The method of claim 4 , wherein the gate terminal of at least one of the MOSCAPs terminals comprises poly-silicon, wherein the gate terminal of at least one of the MOSCAPs comprises copper, and wherein the gate terminal of at least one of the MOSCAPs comprises tungsten.

7. The method of claim 1 , wherein the plurality of radiation-induced signals comprises at least two radiation-induced signals.

8. The method of claim 1 , wherein the at least two metal oxide semiconductor capacitors (MOSCAPs) comprise at least three MOSCAPs with different gate materials that give their respective MOSCAP a different radiation sensitivity.

9. An apparatus for determining the energy of incident radiation comprising:
at least two metal oxide semiconductor capacitors (MOSCAPs) each having a gate terminal disposed over a radiation-sensitive layer, the gate terminals of at least two of the MOSCAPs being comprised of a respective different respective gate composition material, wherein each respective different gate composition material has a different respective level of radiation sensitivity which depends on the respective atomic number for the gate composition material and the energy level of an incident radiation, to provide different signals when exposed to incident radiation, so that the energy level of the radiation can be determined.

10. The apparatus of claim 9 , wherein there are at least two MOSCAPs, each having a gate terminal of a different material than the gate terminals of the other MOSCAPs.

11. The apparatus of claim 10 , wherein the gate terminal of one of the at least three MOSCAPs comprises a low atomic number composition material, wherein the gate terminal of one of the at least three MOSCAPs comprises a medium atomic number composition material, and wherein the gate terminal of one of the at least three MOSCAPs comprises a high atomic number composition material, respectively.

12. The apparatus of claim 11 , wherein one gate terminal of the at least three MOSCAPs comprises aluminum, wherein one gate terminal of the at least three MOSCAPs comprises molybdenum, and wherein one gate terminal of the at least three MOSCAPs comprises gold.

13. The apparatus of claim 11 , wherein one gate terminal of the at least three MOSCAPs comprises poly-silicon, wherein one gate terminal of the at least three MOSCAPs comprises copper, and wherein one gate terminal of the at least three MOSCAPs comprises tungsten.

14. The apparatus of claim 9 , wherein the radiation sensitivity of each respective different gate composition material is based on additional secondary electrons produced by radiation passing through the gate composition material.

15. The apparatus of claim 9 , wherein each of the respective different gate composition materials has a different atomic number.

16. A method of determining the energy of incident radiation, comprising:
measuring the radiation-induced signals from the gate terminals in at least three metal oxide semiconductor capacitor (MOSCAP) sensors each having a different gate composition material having a different radiation sensitivity; and determining a tissue equivalent radiation response based on the differences among the radiation induced signals from the one or more MOSCAP sensors.

17. The method of claim 16 , wherein the radiation sensitivity of each respective gate terminal is based on additional secondary electrons produced by radiation passing through the respective different gate composition material of the gate terminal.

18. The method of claim 16 , wherein each of the respective different gate composition materials has a different atomic number.

19. The method of claim 18 , wherein at least one gate terminal of the at least three MOSCAPs comprises a low atomic number composition material, wherein at least one gate terminal of the at least three MOSCAPs comprises a medium atomic number composition material, and wherein at least one gate terminal of the at least three MOSCAPs comprises a high atomic number composition material, respectively.

20. The method of claim 19 , wherein one gate terminal of the at least three MOSCAPs comprises aluminum, wherein one gate terminal of the at least three MOSCAPs comprises molybdenum, and wherein one gate terminal of the at least three MOSCAPs comprises gold.

21. The method of claim 19 , wherein one gate terminal of the at least three MOSCAPs comprises poly-silicon, wherein one gate terminal of the at least three MOSCAPs comprises copper, and wherein one gate terminal of the at least three MOSCAPs comprises tungsten.

Assignees

• Landauer Inc
• Purdue Research Foundation

Inventors

• Salasky Mark Raymond
• Scott Sean M
• Walerow P Alexander
• Valentino Daniel John
• Peroulis Dimitrios

Classifications

• H01L31/119

  Electricity · mapped topic

• H01L31/1804

  Electricity · mapped topic

• G01T7/00

  Details of radiation-measuring instruments · CPC title

• G01T7/005

  calibration techniques (stabilization of spectrometer G01T1/40) · CPC title

• G01T1/026 Primary

  Semiconductor dose-rate meters · CPC title