Accelerated particle and high energy radiation sensor

• US 20060278943A1
• Filed: 05/07/2004
• Published: 12/14/2006
• Est. Priority Date: 05/08/2003
• Status: Active Grant

• Current Assignee: UK Research and Innovation
• Original Assignee: Science and Technology Facilities Council
• Inventors: Prydderch, Mark Lyndon, Turchetta, Renato Andrea Danilo, Villani, Giulio Enrico
• Granted Patent: US 7,944,012 B2
• Time in Patent Office: Days
• US Class Current: 257/431
• CPC Class Codes: H01J 2237/2446 Position sensitive detectors
• CPC Class Codes: H01L 27/14601 Structural or functional details thereof
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers
• CPC Class Codes: H01L 27/14659 Direct radiation imagers structures

Abstract

An accelerated electron detector comprises an array of monolithic sensors in a CMOS structure, each sensor comprising a substrate (10), an epi layer (11), a p+ well (12) and n+ wells (13) which are separated from the p+ well (12) by the epi layer (11). Integrated in the p+ well are a plurality of NMOS transistors. The sensor also includes a deep n region (15) beneath the p+ well (12) which establishes within the epi layer a depletion layer so that on application of a biasing voltage charge carriers generated in the epi layer are caused to drift to the n+ well (13). The detector has improved radiation hardness and it therefore suitable for the detection and imaging of accelerated electrons such as in electron microscopes.

Claims

1. A monolithic sensor adapted for use in the detection of accelerated particles or high energy radiation, the sensor comprising a charge carrier transport layer, the charge carrier transport layer having dopants of a first conductivity type;

at least one first well having dopants of the first conductivity type at a higher concentration than the charge carrier transport layer and having integrated therein readout circuitry;

at least one second well having dopants of a second conductivity type forming a first junction with the charge carrier transport layer whereby when charge carriers are generated in the charge carrier transport layer, the charge carriers move towards and are collected at the junction between the charge carrier transport layer and the second well to generate a signal and wherein the sensor is capable of withstanding bombardment by accelerated particles or high energy radiation.

2. A monolithic sensor as claimed in claim 1, wherein the charge, carrier transport layer and the first and second wells are formed in a complementary metal oxide semiconductor structure.

3. A monolithic sensor as claimed in claim 1, further comprising biasing means for applying a biasing voltage across the sensor.

4. A monolithic sensor as claimed in claim 3, wherein the charge carrier transport layer includes a drift field when the biasing voltage is applied.

5. A monolithic sensor as claimed in claim 4, wherein the charge carrier transport layer is substantially fully depleted when the biasing voltage is applied.

6. A monolithic sensor as claimed in claim 5, wherein the sensor is adapted to withstand a radiation dose of 15 kRads or more.

7. A monolithic sensor as claimed in claim 1, further comprising a third well having dopants of the second conductivity type.

8. A monolithic sensor as claimed in claim 7, wherein the third well is located beneath the first well.

9. A monolithic sensor as claimed in claim 1, wherein the readout circuitry for the sensor comprises one of the following:

1) at least one n MOS transistor located in the first well;

or

2) at least one p MOS transistor located in the second well;

or

3) at least one n MOS transistor and at least one p MOS transistor located respectively in the first well and the second well.

10. A monolithic sensor as claimed in claim 1, further comprising a semiconductor substrate and wherein the charge carrier transport layer has a lower concentration of dopants than the semiconductor substrate.

11. A monolithic sensor as claimed in claim 7, wherein the third well is located adjacent the first well and wherein an isolation layer is provided between the third well and the charge carrier transport layer and wherein the second well extends through the isolation layer to the charge carrier layer.

12. A monolithic sensor as claimed in claim 11, wherein the isolation layer comprises a semiconductor layer containing dopants of the first conductivity type at a concentration greater than the charge carrier transport layer.

13. A monolithic sensor as claimed in claim 11, wherein the isolation layer comprises an insulating dielectric.

14. A monolithic sensor as claimed in claim 1, wherein the junction between the first well and a region having dopants of the second conductivity type forms a second collection junction for generating a signal as a result of a second type of incident accelerated particles or high ionising radiation, different to the first type of accelerated particles or ionising radiation.

15. A monolithic sensor as claimed in claim 14, wherein the junction between the first and second wells forms the second junction.

16. A monolithic sensor as claimed in claim 14, wherein the first and second junctions selectively generate signals indicative of different energies of accelerated particles.

17. A monolithic sensor as claimed in claim 1, wherein the first and second wells are formed in the charge carrier transport layer and the second well is isolated from the first well.

18. A monolithic sensor as claimed in claim 1, further comprising a semiconductor substrate having a thickness of 100 microns or less.

19. A monolithic sensor as claimed in claim 18, wherein said semiconductor substrate includes dopants of the first conductivity type.

20. A monolithic sensor as claimed in claim 1, wherein the rear or the front surface of the sensor array includes a layer of mercuric iodide.

21. A monolithic sensor as claimed in claim 1, wherein the rear or the front surface of the sensor array includes a layer of caesium iodide.

22. A detector comprising an integrated array of monolithic sensors as claimed in claim 1 having integrated therein readout circuitry including complementary metal oxide semiconductor devices for generating spatially resolved signals in response to bombardment by accelerated particles or high energy ionising radiation.

23. An electron microscope comprising an evacuated housing containing an electron source, electron beam acceleration and confinement means, at least one electron beam focusing system and a detector having first and second opposed surfaces, the detector comprising an integrated array of monolithic sensors as claimed in claim 1.