Indirect detector with improved coupling structure and manufacturing method thereof

Abstract

The invention discloses an indirect detector with an improved coupling structure and a manufacturing method thereof, and the indirect detector comprises an image sensor chip, a pixel unit of the image sensor chip is provided with a photosensitive area and a non-photosensitive area, the upper end of the non-photosensitive area is provided with an isolation dielectric layer, the upper end of the photosensitive area is coupled with a scintillation crystal, and the upper end of the scintillation crystal is provided with an isolation dielectric layer. The upper end face of the scintillation crystal pixel structure is flush with the upper end face of the isolation dielectric layer, and the upper end of the scintillation crystal pixel structure and the upper end of the isolation dielectric layer are covered with a top reflection layer. According to the invention, a traditional intermediate coupling layer is canceled, a direct coupling structure of the scintillation crystal material and the image sensor chip is realized, the integration level and the spatial resolution of the indirect detector are greatly improved, the coupling efficiency of the indirect detector is further improved, and the light energy loss and the image distortion are reduced.

Description

Technical Field

[0001] The present invention belongs to the field of indirect detectors, and particularly relates to an indirect detector with an improved coupling structure and a manufacturing method thereof. Background Art

[0002] An indirect detector generally refers to a radiation detector that can efficiently detect radiation and convert it into an electrical signal, and is one of the commonly used devices in radioactive measurements. For example, X-rays are increasingly widely used in the fields of medical diagnosis and industrial non-destructive testing, and high-energy electron beam radiation is also widely used in devices such as transmission electron microscopes. Therefore, the demand for corresponding indirect detectors is also increasing continuously. The working principle of an X-ray detector is as follows: the scintillator material in the detector absorbs the X-ray energy in the corresponding energy range and emits light, and the generated excitation photons are converted into electrical signals by a photoelectric conversion device with a specific spectrum, thereby completing the indirect detection of the X-ray signal. The working principle of a transmission electron microscope is as follows: a high-voltage electric field accelerates the electrons generated by an electron gun to sub-light speed, and then the electrons are focused into a high-energy electron beam by a series of electromagnetic lenses. After the electron beam penetrates the sample, a specific electron beam image is formed. The electron beam image is converted into a visible light image by a scintillation crystal in the indirect detector, and then a fine structure image of the observed sample is formed. However, traditional indirect detectors usually use optical fiber coupling or optical coupling methods to connect the scintillation screen and the image sensor. Therefore, the traditional coupling methods have problems such as complex system structure, low coupling efficiency, limited spatial resolution, and light diffusion between adjacent pixels. With the development trend of indirect detectors towards high resolution, integration, and miniaturization, how to achieve high resolution and miniaturization of indirect detectors has gradually become an important problem that urgently needs to be solved in the development of highly integrated indirect detectors. It is necessary to design the structure and process integration method of indirect detectors more reasonably. Summary of the Invention

[0003] Aiming at the deficiencies of the above-mentioned prior art, the technical problem to be solved by the present invention is: to provide an indirect detector with an improved coupling structure and a manufacturing method thereof.

[0004] To solve the above technical problem, the present invention provides the following technical solutions:

[0005] An indirect detector with an improved coupling structure includes an image sensor chip. The pixel unit of the image sensor chip is provided with a photosensitive area and a non-photosensitive area. An isolation dielectric layer is provided at the upper end of the non-photosensitive area. A scintillation crystal is coupled to the upper end of the photosensitive area, thereby forming a scintillation crystal pixel structure. The upper end surface of the scintillation crystal pixel structure is flush with the upper end surface of the isolation dielectric layer. A top reflection layer is covered on the upper ends of the scintillation crystal pixel structure and the isolation dielectric layer.

[0006] Further, the scintillation crystal is made of a material that can absorb the energy of incident X-rays or electron beams and be excited to release photons in the visible spectral range; the isolation dielectric layer and the top reflective layer are made of non-transparent materials to facilitate the reflection of the excited photons.

[0007] Further, the image sensor chip is a radiation-resistant visible light image sensor.

[0008] Further, the scintillation crystal is a cerium-ion doped yttrium aluminum garnet crystal.

[0009] Further, the material of the isolation dielectric layer is TiO 2 ; the material of the top reflective layer is TiO 2 .

[0010] A method for manufacturing an indirect detector with an improved coupling structure includes the following steps:

[0011] S100. Take an image sensor chip wafer on which a plurality of image sensor chips are formed;

[0012] S200. Deposit an isolation dielectric layer with a predetermined thickness on the upper end of the non-photosensitive area of the pixel unit of the image sensor chip, thereby forming a photosensitive through-hole structure above the photosensitive area of the pixel unit;

[0013] S300. Deposit a scintillation crystal on the upper end of the photosensitive area of the pixel unit of the image sensor chip until the photosensitive through-hole structure is filled, thereby forming a scintillation crystal pixel structure in the photosensitive through-hole;

[0014] S400. Polish the scintillation crystal pixel structure and the isolation dielectric layer so that the upper end surface of the scintillation crystal pixel structure is flush with the upper end surface of the isolation dielectric layer;

[0015] S500. Deposit a top reflective layer on the upper ends of the scintillation crystal pixel structure and the isolation dielectric layer.

[0016] Further, in the step S200, the isolation dielectric layer is deposited and grown by chemical vapor deposition; in the step S300, the scintillation crystal is deposited by physical vapor deposition; in the step S500, the top reflective layer is deposited and grown by chemical vapor deposition.

[0017] Further, the image sensor chip is a radiation-resistant visible light image sensor.

[0018] Further, the scintillation crystal is a cerium-ion doped yttrium aluminum garnet crystal.

[0019] Further, the material of the isolation dielectric layer is TiO2 ; The material of the top reflective layer is TiO 2 .

[0020] In the present invention, the structure of the indirect detector is mainly improved. The traditional intermediate coupling layer of the indirect detector is cancelled, and a structure in which the scintillating crystal material is directly coupled to the image sensor chip is realized, greatly improving the integration and spatial resolution of the indirect detector, thereby improving the coupling efficiency of the indirect detector, reducing light energy loss and image distortion. At the same time, the system structure is simplified and the detector volume is reduced; compared with the traditional optical lens coupling structure, the device thickness can be reduced from about 20 mm to less than about 0.5 mm, greatly improving the system integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings described herein are used to provide a further understanding of the present application and form a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation of the present application. In the drawings:

[0022] Figure 1 is a schematic structural diagram of an embodiment of an indirect detector with an improved coupling structure according to the present invention.

[0023] Figure 2 is a flowchart of an embodiment of a manufacturing method of an indirect detector with an improved coupling structure according to the present invention.

[0024] Figure 3 is a schematic structural diagram of an image sensor chip.

[0025] Figure 4 is a schematic structural diagram after forming an isolation dielectric layer on the image sensor chip.

[0026] Figure 5 is a schematic structural diagram after depositing a scintillating crystal and performing a polishing process.

[0027] Figure 6 is a schematic structural diagram after forming a top reflective layer.

[0028] The reference numerals in the specification drawings are as follows:

[0029] Image sensor chip - 100; Pixel unit - 110; Non-photosensitive area - 111; Photosensitive area - 112; Isolation dielectric layer - 210; Photosensitive via structure - 211; Scintillating crystal pixel structure - 220; Photon - 221; Photon movement path - 222; Top reflective layer - 230. DETAILED DESCRIPTION OF THE INVENTION

[0030] The following specific examples illustrate the implementation manners of the present invention. The diagrams provided in the following embodiments only schematically illustrate the basic concept of the present invention. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0031] Please refer to Figure 1 , Figure 1 , which is a schematic structural diagram of an embodiment of an indirect detector with an improved coupling structure according to the present invention. An indirect detector with an improved coupling structure in this embodiment includes an image sensor chip 100, and the image sensor chip 100 is usually a radiation-resistant visible light image sensor; the purpose of the radiation-resistant design is mainly to avoid radiation damage to the image sensor caused by X-rays / electron beams that penetrate a small amount of the scintillating crystal pixel structure 220.

[0032] The pixel unit 110 of the image sensor chip 100 is provided with a photosensitive area 112 and a non-photosensitive area 111. An isolation dielectric layer 210 is provided at the upper end of the non-photosensitive area 111. Of course, an isolation dielectric layer 210 is generally also provided above the area outside the pixel unit 110 of the image sensor chip 100. The isolation dielectric layer 210 is mainly used for optical isolation between adjacent pixel units 110 to reduce optical crosstalk. The material selection of the isolation dielectric layer 210 mainly considers materials that are compatible with integrated circuit processes and have non-transparency. In this embodiment, the material of the isolation dielectric layer 210 is TiO 2 .

[0033] A scintillating crystal is coupled to the upper end of the photosensitive area 112, thereby forming a scintillating crystal pixel structure 220. The scintillating crystal uses a material that can absorb the energy of incident X-rays or electron beams and be excited to release photons 221 in the visible spectral band, and is used to absorb the energy of X-rays or electron beams and then excite visible light that can be detected by the image sensor chip 100. The selection requirements for the scintillating crystal material consider a suitable X-ray / electron beam activation energy range, a suitable output visible light band range, adjustable conversion efficiency, and a signal-to-noise ratio that meets the signal-to-noise ratio requirements of the detector system; in this embodiment, the scintillating crystal is a cerium ion-doped yttrium aluminum garnet crystal.

[0034] The upper end surface of the scintillating crystal pixel structure 220 is flush with the upper end surface of the isolation dielectric layer 210. A top reflection layer 230 is covered on the upper ends of the scintillating crystal pixel structure 220 and the isolation dielectric layer 210. The top reflection layer 230 serves as a protective layer of the detector on the one hand and as a reflection layer to reflect the excited photons 221 to improve the photon 221 collection efficiency on the other hand. The material selection of the top reflection layer 230 mainly considers materials that are compatible with integrated circuit processes and have non-transparency. In this embodiment, the material of the top reflection layer 230 is TiO 2 .

[0035] With the structure of this embodiment, the scintillating crystal pixel structure 220 of the pixel unit 110 of the image sensor chip 100 absorbs the incident X-ray / electron beam energy and is excited, releasing photons 221 in the visible spectral range. After the excited photons 221 are reflected and collected by the isolation dielectric layer 210 and / or the top reflective layer 230, they are converted into electrical signals through "photoelectric" conversion at the photosensitive area 112 of the pixel unit 110. Therefore, the image output by the image sensor chip 100 is the detection image corresponding to the X-ray / electron beam. Please continue to refer to Figure 1 The photon movement path 222 is one of the paths formed by the excited photons 221 being reflected by the isolation dielectric layer 210 and the top reflective layer 230 respectively.

[0036] During operation, the X-ray or high-energy electron beam carrying image information passes through the top reflective layer 230 of the indirect detector and reaches the scintillating crystal pixel structure 220. Inside the scintillating crystal pixel structure 220, the scintillating crystal is excited by the X-ray or high-energy electron beam and releases photons 221. Pixels at different positions also generate different numbers of photons 221 due to the different brightness levels of the X-ray or high-energy electron beam. After a series of reflections and collections of the photons 221, the photons 221 in each pixel area are converted into visible light image signals by the image sensor and output, thus realizing the conversion of the X-ray or high-energy electron beam image into a visible light image.

[0037] Compared with traditional indirect detectors, the indirect detector with an improved coupling structure provided in this embodiment cancels the traditional intermediate coupling layer, realizes the direct coupling structure between the scintillating crystal material and the image sensor chip 100, greatly improves the integration and spatial resolution of the indirect detector, further improves the coupling efficiency of the indirect detector, reduces light energy loss and image distortion, simplifies the system structure, and reduces the detector volume at the same time. Compared with the traditional optical lens coupling structure, the device thickness can be reduced from about 20 mm to less than about 0.5 mm.

[0038] Please refer to Figure 2 , Figure 2 FIG. is a flowchart of an embodiment of a manufacturing method of an indirect detector with an improved coupling structure according to the present invention. The manufacturing method of the indirect detector with an improved coupling structure in this embodiment includes the following steps:

[0039] S100. Take a wafer of an image sensor chip 100. The wafer of the image sensor chip 100 is generally fabricated based on standard integrated circuit manufacturing processes. Multiple image sensor chips 100 are formed on the wafer of the image sensor chip 100. The image sensor chips 100 are usually radiation-resistant visible light image sensors. The purpose of the radiation-resistant design is mainly to avoid radiation damage to the image sensor from X-rays / electron beams that penetrate a small number of scintillating crystal pixel structures 220. Please refer to Figure 3 , the image sensor chip 100 has multiple pixel units, and each pixel unit is provided with a photosensitive area 112 and a non-photosensitive area 111.

[0040] S200. Please refer to Figure 4 , deposit an isolation dielectric layer 210 with a predetermined thickness on the upper end of the non-photosensitive area 111 of the pixel unit 110 of the image sensor chip 100, so as to form a photosensitive via structure 211 above the photosensitive area 112 of the pixel unit 110. Of course, an isolation dielectric layer 210 is generally also deposited above the area outside the pixel unit 110 of the image sensor chip 100. The isolation dielectric layer 210 is generally deposited by chemical vapor deposition; in this embodiment, the material of the isolation dielectric layer 210 is TiO 2 .

[0041] S300. Please refer to Figure 5 , deposit a scintillating crystal on the upper end of the photosensitive area 112 of the pixel unit 110 of the image sensor chip 100 until the photosensitive via structure 211 is filled, so as to form a scintillating crystal pixel structure 220 in the photosensitive via. The scintillating crystal is generally deposited by physical vapor deposition; in this embodiment, the scintillating crystal is a cerium ion-doped yttrium aluminum garnet crystal.

[0042] S400. Please continue to refer to Figure 5 , polish the scintillating crystal pixel structure 220 and the isolation dielectric layer 210 so that the upper end surface of the scintillating crystal pixel structure 220 is flush with the upper end surface of the isolation dielectric layer 210.

[0043] S500. Please refer to Figure 6 , deposit a top reflective layer 230 on the upper ends of the scintillating crystal pixel structure 220 and the isolation dielectric layer 210, thereby realizing the process integration of the scintillating crystal and the image sensor chip 100. The top reflective layer 230 is generally deposited by chemical vapor deposition; in this embodiment, the material of the top reflective layer 230 is TiO 2 .

[0044] The manufacturing method of this embodiment will be described below by taking a highly integrated indirect detector applied to a 120 kV transmission electron microscope as an example.

[0045] First, an image sensor chip 100 wafer is fabricated based on the standard integrated circuit manufacturing process. The type of the image sensor chip 100 on the image sensor chip 100 wafer is selected as a radiation-resistant visible light image sensor with a response band range of 400 nm to 750 nm.

[0046] Second, according to the design indexes such as the signal-to-noise ratio of the high-integration indirect detector, a TiO with a required thickness is deposited on the upper end of the non-photosensitive area 111 of the pixel unit 110 of the image sensor chip 100 by methods such as chemical vapor deposition. 2 to form an isolation dielectric layer 210.

[0047] Then, a CeYAG scintillation crystal (i.e., cerium ion-doped yttrium aluminum garnet crystal) is deposited and filled on the upper end of the photosensitive area 112 of the pixel unit 110 of the image sensor chip 100 by physical vapor deposition to form a scintillation crystal pixel structure 220.

[0048] After that, the scintillation crystal pixel structure 220 and the isolation dielectric layer 210 are polished so that the upper end surface of the scintillation crystal pixel structure 220 is flush with the upper end surface of the isolation dielectric layer 210.

[0049] Finally, TiO is deposited and grown on the upper surface of the image sensor chip 100 wafer by chemical vapor deposition. 2 to form a top reflection layer 230.

[0050] The high-integration indirect detector fabricated by the above process integration method can be applied to a 120 kV transmission electron microscope. When a high-energy electron beam of 120 keV in the transmission electron microscope passes through the object to be observed, a specific electron beam image is formed. The electron beam image reaches the high-integration indirect detector after a series of reflections, and enters the scintillation crystal pixel structure 220 of each pixel unit 110 through the top reflection layer of the detector. The CeYAG scintillation crystal in each corresponding pixel unit 110 absorbs the energy of the 120 keV electron beam and excites visible light with a wavelength of about 550 nm. The photons 221 in the structure of each pixel unit 110 are "photoelectrically" converted into corresponding electrical signals after being reflected by the isolation dielectric layer 210 and the reflection layer. Finally, the image output by the image sensor is the image of the object to be observed detected by the transmission electron microscope.

[0051] This embodiment innovatively proposes a manufacturing method for an indirect detector with an improved coupling structure. On the one hand, by adopting a structure in which a scintillation crystal material is directly coupled with an image sensor chip 100, full-process integration of the indirect detector is achieved, which can improve the coupling efficiency of the indirect detector, reduce light energy loss and image distortion, simplify the system structure, and reduce the volume of the indirect detector. Compared with the traditional optical lens coupling structure, the device thickness can be reduced from about 20 mm to less than about 0.5 mm, greatly improving the system integration. On the other hand, the process integration method using integrated circuit process technology greatly improves the integration and spatial resolution of the indirect detector, which is of great significance for the research of high-integration indirect detectors.

[0052] The above embodiments only represent the preferred embodiments of the present invention, and the description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. An indirect detector with an improved coupling structure, characterized in that: The invention comprises an image sensor chip, wherein a pixel unit of the image sensor chip is provided with a photosensitive area and a non-photosensitive area, an isolation medium layer is provided at the upper end of the non-photosensitive area, a scintillation crystal is coupled to the upper end of the photosensitive area, thereby forming a scintillation crystal pixel structure, the upper end surface of the scintillation crystal pixel structure is flush with the upper end surface of the isolation medium layer, and a top reflection layer is covered on the upper ends of the scintillation crystal pixel structure and the isolation medium layer.

2. An indirect detector with an improved coupling structure as claimed in claim 1, characterized in that: The scintillation crystal is made of a material that can absorb incident X-ray or electron beam energy and be excited to release photons in the visible spectrum; the isolation medium layer and the top reflection layer are made of a non-light-transmitting material to facilitate reflection of the excited photons.

3. An indirect detector with an improved coupling structure as claimed in claim 1, characterized in that: The image sensor chip is a radiation-resistant visible light image sensor.

4. An indirect detector with an improved coupling structure as claimed in claim 1, characterized in that: The scintillation crystal is a cerium ion doped yttrium aluminate garnet crystal.

5. An indirect detector with an improved coupling structure as claimed in claim 1, characterized in that: The material of the isolation dielectric layer is TiO2; the material of the top reflection layer is TiO2.

6. A method for manufacturing an indirect detector with an improved coupling structure, characterized in that: The following steps are involved: S100, taking an image sensor chip wafer, wherein the image sensor chip wafer is formed with a plurality of image sensor chips; S200, depositing an isolation dielectric layer of a predetermined thickness on the upper end of the non-photosensitive area of ​​the pixel unit of the image sensor chip, thereby forming a photosensitive through-hole structure above the photosensitive area of ​​the pixel unit; S300, depositing scintillation crystals on the upper end of the photosensitive area of ​​the pixel unit of the image sensor chip until the photosensitive through-hole structure is filled, thereby forming a scintillation crystal pixel structure in the photosensitive through-hole; S400, polishing the scintillation crystal pixel structure and the isolation medium layer so that the upper end surface of the scintillation crystal pixel structure is flush with the upper end surface of the isolation medium layer; S500, depositing a top reflection layer on the upper ends of the scintillation crystal pixel structure and the isolation dielectric layer.

7. The method for manufacturing an indirect detector with an improved coupling structure as claimed in claim 6, characterized in that: In the step S200, the isolation dielectric layer is deposited and grown by chemical vapor deposition; in the step S300, the scintillation crystal is deposited by physical vapor deposition; in the step S500, the top reflection layer is deposited and grown by chemical vapor deposition.

8. The method for manufacturing an indirect detector with an improved coupling structure as claimed in claim 6, characterized in that: The image sensor chip is a radiation-resistant visible light image sensor.

9. The method for manufacturing an indirect detector with an improved coupling structure as claimed in claim 6, characterized in that: The scintillation crystal is a cerium ion doped yttrium aluminate garnet crystal.

10. The method for manufacturing an indirect detector with an improved coupling structure according to claim 6, characterized in that: The material of the isolation dielectric layer is TiO2; the material of the top reflection layer is TiO2.

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