阅读说明：本技术 带有闪烁体的辐射检测器 (Radiation detector with scintillator ) 是由 曹培炎 刘雨润 于 2019-03-29 设计创作，主要内容包括：本文公开了一种辐射检测器(300,500),其包括第一像素(150)；第一反射器(314)；第一闪烁体(316),其中所述第一反射器(314)被配置为将由所述第一闪烁体(316)发射的基本上所有的光子引导到所述第一像素(150)中。所述第一反射器(314)被配置为将由所述第一闪烁体(316)发射的光子朝向所述第一反射器(314)反射。所述第一闪烁体(316)基本上完全地被所述第一反射器(314)和所述第一像素(150)包围。(Disclosed herein is a radiation detector (300, 500) comprising a first pixel (150); a first reflector (314); a first scintillator (316), wherein the first reflector (314) is configured to direct substantially all photons emitted by the first scintillator (316) into the first pixel (150). The first reflector (314) is configured to reflect photons emitted by the first scintillator (316) toward the first reflector (314). The first scintillator (316) is substantially completely surrounded by the first reflector (314) and the first pixel (150).)

1. A radiation detector, comprising

A first pixel;

a first reflector; and

the first scintillator is a first scintillator having a first refractive index,

wherein the first reflector is configured to direct substantially all photons emitted by the first scintillator into the first pixel.

2. The radiation detector of claim 1, wherein the first reflector is in direct physical contact with the first scintillator.

3. The radiation detector of claim 1, wherein the first scintillator is in direct physical contact with the first pixel.

4. The radiation detector of claim 1, further comprising:

a second pixel adjacent to the first pixel;

a second reflector; and

a second scintillator having a second conductivity type and a second conductivity type,

wherein the second reflector is configured to direct substantially all photons emitted by the second scintillator into the second pixel.

5. The radiation detector of claim 4, wherein the first reflector is in direct physical contact with the second reflector.

6. The radiation detector of claim 4, further comprising:

a third pixel adjacent to the first pixel;

a third reflector; and

a third scintillator which is a second scintillator having a second refractive index,

wherein the third reflector is configured to direct substantially all photons emitted by the third scintillator into the third pixel.

7. The radiation detector of claim 1, wherein the first reflector is configured to reflect photons emitted by the first scintillator toward the first reflector.

8. The radiation detector of claim 1, wherein the first reflector is not opaque to radiation particles capable of causing the first scintillator to emit photons when the radiation particles are incident on the first scintillator.

9. The radiation detector of claim 1, wherein the first scintillator is substantially completely surrounded by the first reflector and the first pixel.

10. The radiation detector of claim 1, further comprising:

a fourth reflector; and

a fourth scintillator having a second conductivity type different from the first conductivity type,

wherein the fourth reflector is configured to direct substantially all photons emitted by the fourth scintillator into the first pixel.

11. The radiation detector of claim 1, wherein the first reflector comprises a material selected from the group consisting of aluminum, silver, gold, copper, and any combination thereof.

12. The radiation detector of claim 1, wherein the first scintillator comprises sodium iodide.

13. The radiation detector of claim 1, wherein the first scintillator comprises quantum dots.

14. The radiation detector of claim 1, further comprising a first substrate, wherein the first scintillator is in a recess of a surface of the first substrate.

15. The radiation detector of claim 14, wherein a portion of the first reflector is disposed on a sidewall of the recess.

16. A radiation detector according to claim 14, wherein a portion of the first reflector is disposed on an end wall of the recess.

17. The radiation detector of claim 14, wherein the recess has a truncated conical shape.

18. The radiation detector of claim 14, wherein the first substrate comprises silicon or silicon dioxide.

19. The radiation detector of claim 14, further comprising a second substrate, wherein the first pixel is in the second substrate.

20. The radiation detector of claim 19, further comprising a sealing layer disposed between the first substrate and the second substrate, wherein the sealing layer is not opaque to photons emitted by the first scintillator.

21. A method of operating a radiation detector, comprising:

exposing a first scintillator of the radiation detector to first radiation particles, thereby causing emission of first photons from the first scintillator; and

substantially all photons emitted by the first scintillator are directed into a first pixel of the radiation detector using a first reflector of the radiation detector.

22. The method of claim 21, wherein the first reflector is in direct physical contact with the first scintillator.

23. The method of claim 21, wherein the first scintillator is in direct physical contact with the first pixel.

24. The method of claim 21, further comprising determining a characteristic of the first radiation particle based on the first photon.

25. The method of claim 24, wherein the characteristic is an energy of the first radiation particle or a radiation flux of the first radiation particle.

26. The method of claim 21, further comprising:

exposing a second scintillator of the radiation detector to a second radiation particle, thereby causing emission of a second photon from the second scintillator; and

directing substantially all photons emitted by the second scintillator into a second pixel of the radiation detector using a second reflector of the radiation detector, wherein the second pixel is adjacent to the first pixel.

27. The method of claim 26, wherein the first reflector is in direct physical contact with the second reflector.

28. The method of claim 26, further comprising:

exposing a third scintillator of the radiation detector to a third radiation particle, thereby causing emission of a third photon from the third scintillator; and

directing substantially all photons emitted by the third scintillator into a third pixel of the radiation detector using a third reflector of the radiation detector, wherein the third pixel is adjacent to the first pixel.

29. The method of claim 21, wherein the directing comprises reflecting photons emitted by the first scintillator toward the first reflector using the first reflector.

30. The method of claim 21, wherein the first reflector is not opaque to the first radiation particles.

31. The method of claim 21, wherein the first scintillator is substantially completely surrounded by the first reflector and the first pixel.

32. The method of claim 21, further comprising:

exposing a fourth scintillator of the radiation detector to fourth radiation particles, thereby causing emission of fourth photons from the fourth scintillator; and

directing substantially all photons emitted by the fourth scintillator into a fourth pixel of the radiation detector using a fourth reflector of the radiation detector.

33. The method of claim 21, wherein the first reflector comprises a material selected from the group consisting of aluminum, silver, gold, copper, and any combination thereof.

34. The method of claim 21, wherein the first scintillator comprises quantum dots.

35. The method of claim 21, wherein the step of,

wherein the radiation detector comprises a first substrate, an

Wherein the first scintillator is in a recess of a surface of the first substrate.

36. The method of claim 35, wherein a portion of the first reflector is disposed on a sidewall of the recess.

37. The method of claim 35, wherein a portion of the first reflector is disposed on an end wall of the recess.

38. The method of claim 35, wherein the recess has a truncated conical shape.

39. The method of claim 35, wherein the first substrate comprises silicon or silicon dioxide.

40. The method of claim 35, wherein the step of,

wherein the radiation detector further comprises a second substrate, and

wherein the first pixel is in the second substrate.

41. The method of claim 40, wherein said step of selecting said target,

wherein the radiation detector further comprises a sealing layer disposed between the first substrate and the second substrate, and

wherein the sealing layer is not opaque to photons emitted by the first scintillator.

42. A method, comprising:

forming a first recess on a surface of a first substrate;

forming a first reflector on a wall of the first recess;

forming a first scintillator in the first recess; and

bonding a second substrate having pixels to the first substrate, wherein the first reflector is configured to direct substantially all photons emitted by the first scintillator into the pixels.

43. The method of claim 42, wherein the first reflector is in direct physical contact with the first scintillator.

44. The method of claim 42, wherein the first scintillator is in direct physical contact with the pixel.

45. The method of claim 42, wherein the first reflector is configured to reflect photons emitted by the first scintillator toward the first reflector.

46. The method of claim 42, wherein the first scintillator is substantially completely surrounded by the first reflector and the pixel.

47. The method of claim 42, further comprising:

forming a second recess on a surface of the first substrate;

forming a second reflector on a wall of the second recess; and

forming a second scintillator in the second recess,

wherein the second reflector is configured to direct substantially all photons emitted by the second scintillator into the pixel.

[ technical field ] A method for producing a semiconductor device

The disclosure herein relates to radiation detectors.

[ background of the invention ]

A radiation detector is a device that measures a characteristic of radiation. Examples of the characteristics may include the spatial distribution of intensity, phase and polarization of the radiation. The radiation may be radiation that interacts with the object. For example, the radiation measured by the radiation detector may be radiation that has been transmitted through or reflected from the object. The radiation may be electromagnetic radiation such as infrared light, visible light, ultraviolet light, X-rays or gamma rays. The radiation may be of other types, such as alpha rays and beta rays. The radiation may include radiation particles, such as photons (electromagnetic waves) and sub-atomic particles.

[ summary of the invention ]

Disclosed herein is a radiation detector comprising a first pixel; a first reflector; and a first scintillator, wherein the first reflector is configured to direct substantially all photons emitted by the first scintillator into the first pixel.

According to an embodiment, the first reflector is in direct physical contact with the first scintillator.

According to an embodiment, the first scintillator is in direct physical contact with the first pixel.

According to an embodiment, the radiation detector further comprises a second pixel adjacent to the first pixel; a second reflector; and a second scintillator, wherein the second reflector is configured to direct substantially all photons emitted by the second scintillator into the second pixel.

According to an embodiment, the first reflector is in direct physical contact with the second reflector.

According to an embodiment, the radiation detector further comprises a third pixel adjacent to the first pixel; a third reflector; and a third scintillator, wherein the third reflector is configured to direct substantially all photons emitted by the third scintillator into the third pixel.

According to an embodiment, the first reflector is configured to reflect photons emitted by the first scintillator towards the first reflector.

According to an embodiment, the first reflector is not opaque to radiation particles, which are capable of causing the first scintillator to emit photons when the radiation particles are incident on the first scintillator.

According to an embodiment, the first scintillator is substantially completely surrounded by the first reflector and the first pixel.

According to an embodiment, the radiation detector further comprises a fourth reflector; and a fourth scintillator, wherein the fourth reflector is configured to direct substantially all photons emitted by the fourth scintillator into the first pixel.

According to an embodiment, the first reflector comprises a material selected from the group consisting of aluminum, silver, gold, copper, and any combination thereof.

According to an embodiment, the first scintillator comprises sodium iodide.

According to an embodiment, the first scintillator comprises quantum dots.

According to an embodiment, the radiation detector further comprises a first substrate, wherein the first scintillator is in a recess of a surface of the first substrate.

According to an embodiment, a portion of the first reflector is arranged on a side wall of the recess.

According to an embodiment, a portion of the first reflector is arranged on an end wall of the recess.

According to an embodiment, the recess has a truncated cone shape.

According to an embodiment, the first substrate comprises silicon or silicon dioxide.

According to an embodiment, the radiation detector further comprises a second substrate, wherein the first pixels are in the second substrate.

According to an embodiment, the radiation detector further comprises a sealing layer disposed between the first substrate and the second substrate, wherein the sealing layer is not opaque for photons emitted by the first scintillator.

Disclosed herein is a method of operating a radiation detector, comprising exposing a first scintillator of the radiation detector to first radiation particles, thereby causing emission of first photons from the first scintillator; and directing substantially all photons emitted by the first scintillator into a first pixel of the radiation detector using a first reflector of the radiation detector.

According to an embodiment, the first reflector is in direct physical contact with the first scintillator.

According to an embodiment, the first scintillator is in direct physical contact with the first pixel.

According to an embodiment, the method further comprises determining a characteristic of the first radiation particle based on the first photon.

According to an embodiment, the characteristic is an energy of the first radiation particle or a radiation flux of the first radiation particle.

According to an embodiment, the method further comprises exposing a second scintillator of the radiation detector to a second radiation particle, thereby causing emission of a second photon from the second scintillator; and directing substantially all photons emitted by the second scintillator into a second pixel of the radiation detector using a second reflector of the radiation detector, wherein the second pixel is adjacent to the first pixel.

According to an embodiment, the first reflector is in direct physical contact with the second reflector.

According to an embodiment, the method further comprises exposing a third scintillator of the radiation detector to a third radiation particle, thereby causing emission of a third photon from the third scintillator; and directing substantially all photons emitted by the third scintillator into a third pixel of the radiation detector using a third reflector of the radiation detector, wherein the third pixel is adjacent to the first pixel.

According to an embodiment, the directing comprises reflecting photons emitted by the first scintillator towards the first reflector using the first reflector.

According to an embodiment, the first reflector is not opaque to the first radiation particles.

According to an embodiment, the first scintillator is substantially completely surrounded by the first reflector and the first pixel.

According to an embodiment, the method further comprises exposing a fourth scintillator of the radiation detector to fourth radiation particles, thereby causing emission of fourth photons from the fourth scintillator; and directing substantially all photons emitted by the fourth scintillator into a fourth pixel of the radiation detector using a fourth reflector of the radiation detector.

According to an embodiment, the first reflector comprises a material selected from the group consisting of aluminum, silver, gold, copper, and any combination thereof.

According to an embodiment, the first scintillator comprises quantum dots.

According to an embodiment, the radiation detector comprises a first substrate, and wherein the first scintillator is in a recess of a surface of the first substrate.

According to an embodiment, a portion of the first reflector is arranged on a side wall of the recess.

According to an embodiment, a portion of the first reflector is arranged on an end wall of the recess.

According to an embodiment, the recess has a truncated cone shape.

According to an embodiment, the first substrate comprises silicon or silicon dioxide.

According to an embodiment, the radiation detector further comprises a second substrate, and the first pixels are in the second substrate.

According to an embodiment, the radiation detector further comprises a sealing layer disposed between the first substrate and the second substrate, and wherein the sealing layer is not opaque to photons emitted by the first scintillator.

Disclosed herein is a method comprising forming a first recess on a surface of a first substrate; forming a first reflector on a wall of the first recess; forming a first scintillator in the first recess; and bonding a second substrate having pixels to the first substrate, wherein the first reflector is configured to direct substantially all photons emitted by the first scintillator into the pixels.

According to an embodiment, the first reflector is in direct physical contact with the first scintillator.

According to an embodiment, the first scintillator is in direct physical contact with the pixel.

According to an embodiment, the first reflector is configured to reflect photons emitted by the first scintillator towards the first reflector.

According to an embodiment, the first scintillator is substantially completely surrounded by the first reflector and the pixel.

According to an embodiment, the method further comprises forming a second recess on the surface of the first substrate; forming a second reflector on a wall of the second recess; and forming a second scintillator in the second recess, wherein the second reflector is configured to direct substantially all photons emitted by the second scintillator into the pixel.

[ description of the drawings ]

Fig. 1 schematically illustrates an image sensor according to an embodiment.

Fig. 2A schematically shows a simplified cross-sectional view of the image sensor according to an embodiment.

Fig. 2B schematically shows a detailed cross-sectional view of the image sensor according to an embodiment.

Fig. 2C schematically shows an alternative detailed cross-sectional view of the image sensor according to an embodiment.

Fig. 3A schematically illustrates a radiation detector including the image sensor of fig. 2B according to an embodiment.

Fig. 3B schematically illustrates a perspective view of a portion of the radiation detector of fig. 3A, in accordance with an embodiment.

Fig. 3C shows how a reflector according to an embodiment directs photons emitted by an associated scintillator.

Fig. 4A-4H schematically illustrate formation of the radiation detector of fig. 3A, according to an embodiment.

Fig. 5A, 5B, and 5C schematically illustrate the formation of an alternative radiation detector according to an embodiment.

[ detailed description ] embodiments

Fig. 1 schematically shows an image sensor 100 as an example. The image sensor 100 may have an array of the pixels 150. The pixel array may be a rectangular array (as shown in fig. 1), a honeycomb array, a hexagonal array, or any other suitable array. In the example of fig. 1, the array of pixels 150 has 4 rows and 7 columns; in general, however, the array of pixels 150 may have any number of rows and any number of columns.

Each of the pixels 150 may be configured to detect radiation from a radiation source incident thereon and may be configured to measure a characteristic of the radiation (e.g., energy, wavelength, and frequency of radiation particles). For example, each pixel 150 may be configured to count the number of radiation particles incident thereon over a period of time whose energy falls in a plurality of energy bins. All of the pixels 150 may be configured to count the number of radiation particles in a plurality of energy bins incident thereon over the same time period. When the incident radiation particles have similar energies, the pixel 150 may simply be configured to count the number of radiation particles incident thereon over a period of time without measuring the energy of the individual radiation particles.

Each pixel 150 may have its own analog-to-digital converter (ADC) configured to digitize an analog signal representing the energy of an incident radiation particle into a digital signal, or an analog signal representing the total energy of a plurality of incident radiation particles into a digital signal. The pixels 150 may be configured to operate in parallel. For example, while one pixel 150 measures one incident radiation particle, another pixel 150 may be waiting for another radiation particle to arrive. The pixels 150 may not necessarily be individually addressable.

The image sensor 100 described herein may have applications such as X-ray telescopes, mammography, industrial X-ray defect detection, X-ray microscopy or X-ray microscopy, X-ray casting inspection, X-ray non-destructive inspection, X-ray weld inspection, X-ray digital subtraction angiography, and the like. It is also suitable that the image sensor 100 is used in place of a photographic plate, photographic film, PSP plate, X-ray image intensifier, scintillator, or other semiconductor X-ray detector. The image sensor 100 may also be used as an image sensor that detects visible light photons containing an image of an object.

FIG. 2A schematically illustrates a simplified cross-sectional view of the image sensor 100 along line 2A-2A in FIG. 1, in accordance with an embodiment. More specifically, the image sensor 100 may include a radiation absorbing layer 110 and an electronics layer 120 (e.g., ASIC) for processing or analyzing electrical signals of incident radiation generated in the radiation absorbing layer 110. The image sensor 100 may or may not include a scintillator (not shown). The radiation absorbing layer 110 may comprise a semiconductor material such as silicon, germanium, GaAs, CdTe, CdZnTe, or combinations thereof. The semiconductor material may have a high mass attenuation coefficient for the radiation of interest.

Fig. 2B schematically shows a detailed cross-sectional view of the image sensor 100 along line 2A-2A in fig. 1 as an example. More specifically, the radiation absorbing layer 110 may include one or more diodes (e.g., p-i-n or p-n) comprised of one or more discrete regions 114 of first and second doped regions 111, 113. The second doped region 113 may be separated from the first doped region 111 by an optional intrinsic region 112. The discrete regions 114 are separated from each other by the first doped region 111 or the intrinsic region 112. The first and second doped regions 111, 113 have opposite type doping (e.g., region 111 is p-type and region 113 is n-type, or region 111 is n-type and region 113 is p-type). In the example of fig. 2B, each discrete region 114 of the second doped region 113 constitutes a diode together with the first doped region 111 and the optional intrinsic region 112. That is, in the example of fig. 2B, the radiation absorbing layer 110 includes a plurality of diodes (more specifically, 7 diodes correspond to 7 pixels 150 of a row in the array of fig. 1, with only two pixels 150 labeled in fig. 2B for simplicity). The plurality of diodes have electrical contact 119A as a shared (common) electrode. The first doped region 111 may also have discrete portions.

The electronics layer 120 may comprise electronics systems 121 adapted to process or interpret signals generated by radiation incident on the radiation absorbing layer 110. The electronic system 121 may include analog circuits such as filter networks, amplifiers, integrators, comparators, or digital circuits such as microprocessors and memory. The electronic system 121 may include one or more ADCs. The electronic system 121 may include components that are common to the pixels 150 or components that are dedicated to a single pixel 150. For example, the electronic system 121 may include an amplifier dedicated to each pixel 150 and a microprocessor shared among all pixels 150. The electronic system 121 may be electrically connected to the pixels 150 through vias 131. The space between the vias may be filled with a filler material 130, which may increase the mechanical stability of the connection of the electron layer 120 to the radiation absorbing layer 110. Other bonding techniques are possible to connect the electronic system 121 to the pixel 150 without using the via 131.

When radiation from the radiation source (not shown) strikes the radiation absorbing layer 110, which includes a diode, the radiation particles may be absorbed and generate one or more carriers (e.g., electrons and holes) by several mechanisms. The carriers may drift under an electric field towards an electrode of one of the diodes. The electric field may be an external electric field. The electrical contacts 119B may comprise discrete portions, each of which is in electrical contact with the discrete region 114. The term "electrical contact" may be used interchangeably with the word "electrode". In an embodiment, the carriers may drift in different directions such that the carriers generated by a single radiating particle are not substantially shared by two different discrete regions 114 ("substantially not shared" here means that less than 2%, less than 0.5%, less than 0.1%, or less than 0.01% of these carriers flow to one of the discrete regions 114 that is different from the rest of the carriers). The carriers generated by the radiation particles incident around the footprint of one of the discrete regions 114 are substantially not shared by the other of the discrete regions 114. One pixel 150 associated with one discrete region 114 may be the region around the discrete region 114 into which substantially all (more than 98%, more than 99.5%, more than 99.9%, or more than 99.99%) of the carriers generated by one of the radiation particles incident thereon flow. That is, less than 2%, less than 1%, less than 0.1%, or less than 0.01% of the carriers flow out of the pixel 150.

FIG. 2C schematically illustrates an alternative detailed cross-sectional view of the image sensor 100 of FIG. 1 along line 2A-2A, in accordance with embodiments. More specifically, the radiation absorbing layer 110 may include a resistor of a semiconductor material, such as silicon, germanium, GaAs, CdTe, CdZnTe, or a combination thereof, but does not include a diode. The semiconductor material may have a high mass attenuation coefficient for the radiation of interest. In an embodiment, the electronics layer 120 in fig. 2C is similar in structure and function to the electronics layer 120 in fig. 2B.

When the radiation strikes the radiation absorbing layer 110, which includes the resistor but not the diode, the radiation may be absorbed and generate one or more carriers by several mechanisms. One radiation particle can generate 10 to 100000 carriers. The carriers may drift under the electric field toward electrical contact 119A and electrical contact 119B. The electric field may be an external electric field. The electrical contacts 119B include discrete portions. In an embodiment, the carriers may drift in different directions, such that the carriers generated by a single radiating particle are substantially not shared by two different discrete portions of the electrical contact 119B ("substantially not shared" here means that less than 2%, less than 0.5%, less than 0.1%, or less than 0.01% of these carriers flow to discrete portions of a different group than the rest of the carriers). The carriers generated by the radiation particles incident around the footprint of one of the discrete portions of electrical contact 119B are substantially not shared by the other discrete portion of electrical contact 119B. One pixel 150 associated with one of the discrete portions of electrical contact 119B may be a region around the discrete portion into which substantially all (more than 98%, more than 99.5%, more than 99.9%, or more than 99.99%) of the carriers generated by the radiation particles incident therein flow. That is, less than 2%, less than 0.5%, less than 0.1%, or less than 0.01% of the carriers flow out of the pixel associated with one of the discrete portions of electrical contact 119B.

Fig. 3A schematically shows a cross-sectional view of a radiation detector 300 according to an embodiment. In particular, the radiation detector 300 includes a scintillation and reflective layer 310 and the image sensor 100 of fig. 2B or 2C. For simplicity, only the pixels 150, the radiation absorbing layer 110, and the electronics layer 120 of the image sensor 100 are shown hereafter, while other components of the image sensor 100 (e.g., electrical contacts 119A, 119B, vias 131) are not shown.

In an embodiment, the scintillation and reflective layer 310 includes a substrate 312, a reflector 314, and a scintillator 316. The substrate 312 may not be opaque to the radiation of interest 320 (e.g., the radiation 320 may penetrate the substrate 312 with partial attenuation or substantially no attenuation). For example, the substrate 312 may include silicon.

In an embodiment, each scintillator 316 may be completely or nearly completely surrounded (i.e., substantially completely surrounded) by the pixel 150 and the reflector 314. When the scintillator 316 is exposed to the radiation 320, the scintillator 316 can emit photons. The photons may be emitted in multiple directions (e.g., all directions). In an embodiment, the scintillator 316 may include a material such as sodium iodide (NaI). In an embodiment, the scintillator 316 may include quantum dots. The material of the quantum dots may be cadmium selenide (CdSe), cadmium telluride (CdTe), zinc oxide (ZnO), or any combination of these.

In one embodiment, the material and thickness 314' of each reflector 314 is such that each reflector 314 is not opaque to the radiation 320, but reflects substantially all photons emitted by the scintillator 316 enclosed therein toward it. For example, each reflector 314 may comprise aluminum, silver, gold, copper, and any combination thereof; each reflector 314 may have the material and thickness 314' of about 10 micrometers (μm).

Fig. 3B schematically illustrates a perspective view of a pixel 150 and its associated reflector 314 and scintillator 316, in accordance with an embodiment. As shown in fig. 3B, the scintillator 316 is completely surrounded by the pixels 150 and the associated reflector 314.

In an embodiment, referring to fig. 3A and 3B, the operation of the radiation detector 300 may be as follows. In particular, the radiation detector 300 is exposed to the radiation 320 (such as X-rays, gamma rays, etc.) from an object 330 (e.g., a human body part). The radiation 320 may have previously penetrated or scattered from the object 330 and thus carry information about the object 330.

Because the substrate 312 and the reflector 314 are not opaque to the radiation 320, each scintillator 316 is exposed to the radiation 320 and, therefore, emits photons. The photons may be emitted in multiple directions (e.g., all directions).

Each reflector 314 reflects photons incident thereon. Because each scintillator 316 is substantially completely surrounded by the associated reflector 314 and the associated pixel 150, as described above, each photon emitted by a scintillator 316 may enter the pixel 150 without interacting with the reflector 314, or may be reflected one or more times by the reflector 314 before it enters the pixel 150. In other words, the reflector 314 prevents substantially all (i.e., all or substantially all) of the photons emitted by the scintillator 316 from entering the pixel 150. That is, the reflector 314 directs substantially all (i.e., all or substantially all) of the photons emitted by the scintillator 316 into the pixel 150.

Fig. 3C shows how a reflector 314 according to an embodiment directs photons emitted by the associated scintillator 316 into the associated pixel 150. In particular, in a first example, the first radiation particle may follow a path d1 towards said pixel 150. At point a, without any reflection by the mirror 314, the first radiation particle may interact with the scintillator 316 and cause the emission of a first photon, which may enter the pixel 150 along path d 1'. In a second example, the second radiation particle may follow a path d2 towards said pixel 150. At point B, the second radiation particle may interact with the scintillator 316 and cause emission of a second photon, which may be reflected by the reflector 314 at point B1 along path B-B1 and then enter the pixel 150 along path d 2'. In a third example, the third radiation particle may follow a path d3 towards said pixel 150. At point C, the third radiation particle may interact with the scintillator 316 and cause emission of a third photon, which may be reflected by the reflector 314 along path C1-C2 at point C1, then reflected again by the reflector 314 at point C2, and then enter the pixel 150 along path d 3'. Other paths are also possible.

The operation of the radiation detector 300 can be re-described as follows. The radiation 320, which may have been penetrated or scattered from the object 330, now penetrates the substrate 312 and the reflector 314 and is converted into photons by the scintillator 316. Substantially all of the photons are directed by the reflector 314 into the pixel 150 associated with the scintillator 316. In this way, the image of the object 330 captured by the image sensor 100 has negligible cross-talk between the pixels 150 and less photon loss. Pixel crosstalk occurs when photons emitted due to a single particle of the radiation 320 enter more than one pixel 150.

Fig. 4A-4H schematically illustrate a fabrication process of the radiation detector 300 of fig. 3A, according to an embodiment. Specifically, referring to fig. 4A, the fabrication process begins with the substrate 312 having a top surface 312 s. Next, a stencil 410 having apertures 410a is positioned over the top surface 312s of the substrate 312. In an embodiment, the stencil 410 may be made of metal. The stencil 410 may instead be a pattern formed with resist

Fig. 4B illustrates a top view of the structure of fig. 4A, and fig. 4A illustrates a cross-sectional view of the structure of fig. 4B along line 4A-4A, in accordance with an embodiment. In fig. 4B, a portion of the top surface 312s of the substrate 312 is exposed through the holes 410a in the stencil 410.

Next, referring to fig. 4C, the stencil 410 may be used as a mask to etch the substrate 312, thereby forming a recess 420 in the top surface 312s of the substrate 312. In an embodiment, the etching of the substrate 312 may be an anisotropic wet etching using potassium hydroxide (KOH) as an etchant. If the substrate 312 is a silicon substrate and the top surface 312s is a (100) silicon crystal plane, the resulting recess 420, as shown in FIG. 4C, may have a truncated pyramid shape with flat and angled etched walls.

Next, the stencil 410 may be removed, resulting in the structure of fig. 4D. Next, referring to fig. 4E, the reflector 314 (also shown in fig. 3A) is formed on the walls (e.g., side and bottom walls) of the recess 420. In an embodiment, the reflector 314 may be formed by (a) depositing (e.g., by thermal evaporation, sputtering, or other suitable technique) a layer of aluminum onto the structure of fig. 4D, and then (b) polishing back until the top surface 312s of the substrate 312 is exposed to the ambient environment.

Alternatively, the reflector 314 may be formed by depositing a layer of aluminum over the structure of FIG. 4C and then removing the stencil 410.

Next, referring to fig. 4F, a scintillator layer 316t is formed on top of the top surface 312s and the reflector 314. In an embodiment, the scintillator layer 316t may be formed by depositing a composite comprising NaI on top of the top surface 312s and the reflector 314.

Next, the top surface 316s of the scintillator layer 316t may be polished until the top surface 312s of the substrate 312 is exposed to the surrounding environment, thereby producing the scintillator 316, as shown in fig. 4G. Also as a result, the scintillation and reflective layer 310 is formed.

Next, as shown in fig. 4H, the scintillator and reflective layer 310 is bonded to the image sensor 100, thereby obtaining the radiation detector 300 of fig. 3A. In an embodiment, the bonding may be a direct bonding, which is a wafer bonding process without any additional intermediate layers (e.g., solder bumps). The bonding process is based on a chemical bond between two surfaces. Direct bonding can be performed at elevated temperatures, but need not be.

In the above embodiments, referring to fig. 3A, the substrate 312 may comprise silicon or other suitable material.

In the above embodiment, the reflector 314 comprises aluminum. In an alternative embodiment, the reflector 314 may comprise another metal, such as silver, gold, copper, and any combination thereof.

In the above embodiment, referring to fig. 3A and 3B, each pixel 150 has an associated pair of reflector 314 and scintillator 316. In general, each pixel 150 may have N associated pairs (N being a positive integer) of reflectors 314 and scintillators 316, located within the coverage of the pixel 150. Generally, for each pixel 150, all or nearly all (i.e., substantially all) of the photons emitted by the N associated scintillators 316 are directed by the N associated reflectors 314 into that pixel 150.

In the above embodiment, referring to fig. 4E, the reflector 314 is formed by (a) depositing a layer of aluminum on top of the structure of fig. 4D, and then (b) polishing back until the top surface 312s of the substrate 312 is exposed to the ambient environment. In an alternative embodiment, performing only step (a) above (i.e., not performing step (b)) results in the reflectors 314 being engaged with one another as shown in fig. 5A.

Next, the scintillator 316 is formed in the recess 420, resulting in the scintillation and reflective layer 310' of fig. 5B. The formation of the scintillator 316 of fig. 5B is similar to the formation of the scintillator 316 of fig. 4G. Finally, as shown in fig. 5C, the scintillation and reflective layer 310' of fig. 5B is bonded to the image sensor 100, resulting in a radiation detector 500.

Referring to fig. 5C, each scintillator 316 is completely enclosed (or nearly completely enclosed) by the associated pixel 150 and the reflector 314.

Like the radiation detector 300 of fig. 3A, the radiation detector 500 of fig. 5C is also sensitive to the incident radiation 320. During operation of the radiation detector 500, all or substantially all photons emitted by the scintillator 316 are directed by the reflector 314 into the pixel 150.

In the above-described embodiments, referring to fig. 3A and 5C, in the radiation detector 300 and the radiation detector 500, the scintillation and reflective layer 310/310' may be in direct physical contact with the pixels 150 of the image sensor 100. In an alternative embodiment, there may be a sealing layer (not shown) sandwiched between and in direct physical contact with the scintillation and reflective layer 310/310' and the image sensor 100. In this alternative embodiment, the sealing layer may comprise a material, such as a polymer or silicon dioxide, that is transparent or not opaque to the radiation 320. The sealing layer helps to bond the scintillation and reflective layer 310/310' to the image sensor 100. However, due to the presence of the sealing layer, each scintillator 316 is no longer completely surrounded (or almost completely surrounded) by the associated pixel 150 and the associated reflector 314. In an embodiment, the sealing layer should be thin, since the thicker the sealing layer, the more photons emitted by the scintillator 316 can escape the associated pixel 150, thereby increasing pixel crosstalk.

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and not limitation, and their true scope and spirit should be determined by the claims herein.