Preparation method of gadolinium oxysulfide x-ray scintillation screen based on silicon microchannel array, x-ray scintillation screen and application thereof

Abstract

This invention relates to a method for fabricating a gadolinium oxysulfate X-ray scintillation screen based on a silicon microchannel array, as well as the X-ray scintillation screen and its applications, belonging to the field of X-ray imaging technology. It primarily addresses the technical problem of low resolution in existing X-ray scintillation screens. This invention fabricates a tetragonal silicon microchannel structure through photolithography, photoelectrochemical etching, and back-side thinning processes, fundamentally avoiding the problem of microchannel misalignment. The use of ALD tungsten film deposition and pulse electroplating for silver film deposition effectively reduces X-ray crosstalk. Furthermore, the good chemical compatibility between tungsten and silver ensures uniform silver film deposition without microchannel blockage, and the silver film possesses high reflectivity. Vacuum infusion is used to completely fill the microchannels with fluorescent material, avoiding the presence of air or other substances with significantly different refractive indices from the fluorescent material within the channels, and also solving the scattering and reflection problems caused by gaps between particles, effectively improving detection efficiency.

Description

Technical Field

[0001] This invention relates to the field of X-ray imaging technology, specifically to a method for fabricating a gadolinium oxysulfate X-ray scintillation screen based on a silicon microchannel array, as well as the X-ray scintillation screen and its applications. Background Technology

[0002] An X-ray imaging system typically consists of a radiation source, the object under test, a scintillator, a CCD camera, and a computer. It is widely used in medical imaging, non-destructive testing, and security inspection. The X-ray scintillator converts X-rays into visible light and is the core component of the X-ray imaging system. Its most important performance indicators are resolution and luminous efficiency, which determine the quality of the X-ray imaging.

[0003] Currently, cesium iodide (CsI:Tl) and gadolinium oxysulfide (GOS) are both common scintillation materials on the market. CsI:Tl scintillation screens have good response performance to low-energy X-rays and are therefore widely used in medical X-ray detection. GOS scintillation screens, on the other hand, respond well to high-energy X-rays and are therefore widely used in security inspection and industrial non-destructive testing.

[0004] The most important performance parameter of a scintillator is resolution. Sheet-like scintillators lack effective optical isolation, easily generating lateral crosstalk, which leads to a decrease in imaging resolution. To address this issue with CsI:TI scintillators, researchers used thermal evaporation to fabricate columnar structures, improving resolution. However, GOS scintillators cannot be fabricated into columnar structures, and because GOS has a melting point greater than 2000℃, it cannot be fabricated into pixelated scintillators by vacuum melting into silicon microchannel arrays like CsI:TI. Therefore, commercially available GOS scintillators are typically still block-like structures, and their resolution is generally low.

[0005] Patent No. 202411173670.3 discloses a method for fabricating an X-ray fluorescent screen and the screen itself. The microchannel structure used in this patent is a glass microchannel plate, fabricated using lead-silicate glass multifiber drawing technology. This technology involves processes such as drawing single filaments, arranging single filaments, drawing multifilaments, secondary filament arrangement, slicing, polishing, and etching to create the glass microchannel structure. During the single filament arrangement, multifilament drawing, and secondary filament arrangement processes, defects easily occur at the glass fiber interfaces, leading to misalignment of the microchannels. Furthermore, the microchannels in this patent employ a hexagonal close-packed arrangement, while CCD camera pixels are tetragonal. This mismatch in arrangement easily produces moiré patterns, obscuring true image details and causing a decrease in resolution. The patent proposes using vapor deposition, sputtering, or atomic layer deposition to deposit aluminum or silver films within the microchannels. However, due to the poor conformability of vapor deposition and sputtering, uniform film formation is not possible within channels with high aspect ratios. While atomic layer deposition can deposit aluminum or silver films, a single metal film only improves light reflectivity and cannot solve the optical crosstalk problem caused by the Compton scattering effect. This patented microchannel filling method involves preparing a suspension and covering the surface of the microchannel, followed by allowing it to stand or applying external force to deposit fluorescent material inside the microchannel. This method results in the presence of fluorescent material, air, and other substances simultaneously inside the channel of the obtained scintillation screen. The fluorescent material exists in the form of discrete fluorescent particles with gaps between the particles. According to the Fresnel equation, the greater the difference in refractive index between the two media, the higher the reflectivity. When the fluorescent material absorbs X-rays and emits light, the light will be scattered or reflected at the interface of different media, ultimately preventing the light from effectively passing through the microchannel and reducing its detection efficiency. Summary of the Invention

[0006] In view of this, the present invention mainly solves the technical problem of low resolution of X-ray scintillation screens in the prior art, and provides a method for preparing a gadolinium oxysulfate X-ray scintillation screen based on a silicon microchannel array, as well as the X-ray scintillation screen and its application.

[0007] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0008] This invention provides a method for fabricating a gadolinium oxysulfate X-ray scintillation screen based on a silicon microchannel array, comprising the following steps:

[0009] S1. Pretreatment: Selecting the crystal orientation as... <100> N-type silicon wafers with resistivity of 10~10000 The silicon wafer is then subjected to surface cleaning treatment to obtain a clean silicon wafer.

[0010] S2. Doping: Phosphorus doping is performed on the silicon wafer through a diffusion process. After doping, a phosphorus diffusion ohmic contact layer is formed on the back of the silicon wafer.

[0011] S3, Oxidation: Dry oxygen oxidation is performed on the silicon wafer to form a SiO2 masking layer on the surface of the silicon wafer;

[0012] S4. Photolithography: A photoresist film is formed on the front side of the silicon wafer by coating with a photoresist film. Then, the photoresist masking layer is obtained by pre-baking, exposure, and development. Finally, hardening, plasma etching, and photoresist removal are performed to form a SiO2 masking layer pattern on the front side of the silicon wafer.

[0013] S5. Wet etching: Using the SiO2 masking layer pattern formed by photolithography as a masking film, the silicon wafer is placed in potassium hydroxide (KOH) etching solution to prepare an inverted square pyramid structure of induced pits;

[0014] S6. Photoelectrochemical etching: A three-electrode system is selected. The etching electrolyte is a mixture of deionized water, hydrofluoric acid, isopropanol and X100 surfactant. Photoelectrochemical etching is performed on a silicon wafer with an induced pit structure as the substrate to form a square array of silicon microchannels.

[0015] S7. Backside thinning: The silicon microchannel array is oxidized and then placed in a polytetrafluoroethylene fixture. The exposed part of the backside of the silicon wafer is immersed in hydrofluoric acid to remove the oxide layer, and then immersed in KOH solution for etching, thereby preparing a through-type microchannel array structure.

[0016] S8. Shaping: The silicon microchannel array is shaped using tetramethylammonium hydroxide solution (TMAH) to prepare a microchannel array structure with a higher opening area ratio than the through-type microchannel array structure and a smooth microchannel inner wall.

[0017] S9. Atomic layer deposition tungsten film: A tungsten film is deposited on the inner wall of the microchannel array structure of a silicon microchannel array using an atomic layer deposition thin film process.

[0018] S10, Pulse electroplating silver film: The silicon microchannel array is placed in a cyanide-free silver plating solution, and a silver film is deposited on the tungsten film by pulse electroplating.

[0019] S11. Filling scintillator: Gadolinium oxysulfide (GOS) fluorescent material particles and UV adhesive are mixed in a certain proportion and uniformly coated on the surface of silicon microchannel array. The silicon microchannel array is then placed in a tube furnace and heated to the temperature where the UV adhesive has the best fluidity under vacuum. Then, atmospheric pressure is restored and atmospheric pressure is used to fill the channels of the silicon microchannel array with GOS / UV composite scintillator adhesive. Finally, after curing, a gadolinium oxysulfide X-ray scintillator screen based on silicon microchannel array is obtained.

[0020] S12. Packaging: The surface of the gadolinium oxysulfate X-ray scintillation screen based on silicon microchannel array is cleaned. Using thin film preparation technology, aluminum film is deposited on the front side and aluminum oxide film (Al2O3) is deposited on the back side of the gadolinium oxysulfate X-ray scintillation screen based on silicon microchannel array to achieve double-sided packaging.

[0021] Preferably, in step S3, the temperature for dry oxidation of the silicon wafer is 1000°C and the oxidation time is 30 min.

[0022] Preferably, in step S4, photolithography uses a mask with a period of 5μm~50μm and arranged in a square for exposure.

[0023] Preferably, in step S6, the volume ratio of deionized water, hydrofluoric acid, isopropanol, and X100 surfactant is 1800mL:180mL:180mL:2mL, the photoelectrochemical etching temperature is 23℃, and the etching time is 13h.

[0024] Preferably, in step S8, the silicon microchannel array is shaped using a 1wt% TMAH solution to prepare a microchannel array structure with an opening area ratio greater than 70% and smooth inner walls.

[0025] Preferably, in step S9, the thickness of the tungsten film is 50~300nm.

[0026] Preferably, in step S10, the thickness of the silver film is 50~200nm.

[0027] Preferably, in step S11, the UV adhesive is a UV adhesive with a refractive index between 2.0 and 2.4 after curing, and the gadolinium oxysulfate phosphor is composed of Gd2O2S:Tb with a refractive index of 2.2; the UV adhesive is heated to the temperature of 70°C in a vacuum environment where it has the best fluidity.

[0028] The present invention also provides a gadolinium oxysulfate X-ray scintillation screen based on a silicon microchannel array prepared by the above preparation method.

[0029] The present invention also provides an application of the above-mentioned gadolinium oxysulfate X-ray scintillation screen based on silicon microchannel array in medical diagnosis, industrial non-destructive testing, security inspection or academic research.

[0030] The beneficial effects of this invention are:

[0031] This invention provides a method for fabricating a gadolinium oxysulfate X-ray scintillation screen based on a silicon microchannel array. Through photolithography, photoelectrochemical etching, and back-side thinning processes, a tetragonal silicon microchannel structure is fabricated, fundamentally avoiding the problem of microchannel misalignment. Furthermore, the microchannel arrangement is consistent with the pixels of a CCD camera, eliminating moiré patterns simply by adhering to the Nyquist limit, resulting in clearer and higher resolution imaging. A double-layer film is deposited within the silicon microchannels using ALD tungsten film deposition and pulse electroplating for silver film deposition. The tungsten precursor exhibits high reactivity with silicon surface groups, forming strong W-Si bonds to ensure film adhesion, ultimately achieving uniform, continuous, and highly adherent tungsten film deposition. The tungsten film also possesses excellent X-ray blocking capabilities, effectively reducing X-ray crosstalk. Furthermore, tungsten and silver have good chemical compatibility, with no significant chemical reaction between them, and silver exhibits excellent adhesion to the tungsten surface. During electroplating, silver atoms can... Stable growth directly on the tungsten film surface ensures uniform silver film deposition without microchannel blockage. The high reflectivity of the silver film reflects visible light emitted after X-ray absorption by the fluorescent material back to the detector, reducing light scattering and escape losses within the channel. A UV adhesive with a refractive index similar to gadolinium oxide is selected and mixed in a specific ratio. Vacuum infusion is used to completely fill the microchannel, avoiding the presence of air or other substances with significantly different refractive indices from the fluorescent material. This also solves the scattering and reflection problems caused by gaps between particles, effectively improving detection efficiency. Thin-film fabrication technology is used for double-sided encapsulation of the scintillator. An aluminum film is deposited on the front side to enhance light output efficiency due to its high reflectivity. An aluminum oxide film is deposited on the back side, utilizing its excellent chemical stability, high hardness, and high light transmittance to effectively protect the scintillator layer, optimize optical performance, and improve structural stability. Attached Figure Description

[0032] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0033] Figure 1 This is a schematic diagram of the fabrication process of the gadolinium oxysulfate X-ray scintillation screen based on silicon microchannel array of the present invention.

[0034] Figure 2 This is a schematic diagram of the gadolinium oxysulfate X-ray scintillation screen structure of the present invention; wherein, (a) is a schematic diagram of the end face structure, (b) is a schematic diagram of the cross-sectional structure, and (c) is a schematic diagram of the three-dimensional local structure.

[0035] Figure 3 This is a scanning electron microscope image of the silicon microchannel array with a four-way channel arrangement according to Embodiment 1 of the present invention.

[0036] Figure 4 This is a photograph of the front metallographic microscope of the gadolinium oxysulfate X-ray scintillation screen of Embodiment 1 of the present invention.

[0037] Figure 5The image is obtained by X-ray imaging of the resolution panel using the gadolinium oxysulfate X-ray scintillation screen of Example 1.

[0038] Wherein, 1-silicon wafer; 1a-through-microchannel array structure; 1b-microchannel array structure; 2-phosphorus diffusion ohmic contact layer; 3-SiO2 masking layer; 3a-SiO2 masking layer pattern; 4-photoresist film; 4a-photoresist masking layer; 5-induced pit; 6-silicon microchannel array; 7-tungsten film; 8-silver film; 9-GOS / UV composite scintillation adhesive; 10-aluminum film; 11-alumina film; 12-microchannel of silicon microchannel array; 13-microchannel wall of silicon microchannel array. Detailed Implementation

[0039] like Figure 1 and 2 As shown, the present invention provides a method for fabricating a gadolinium oxysulfate X-ray scintillation screen based on a silicon microchannel array, which is described in detail by way of example and includes the following steps:

[0040] S1. Pretreatment: Selecting the crystal orientation as... <100> The N-type silicon wafer 1 has a resistivity of 10~10000 Ω·cm. The silicon wafer 1 was then surface-cleaned according to the standard RCA cleaning process to obtain a clean silicon wafer 1.

[0041] The standard RCA cleaning process consists of four steps: pre-cleaning, SC-1 cleaning, HF rinsing, and SC-2 cleaning, to remove organic matter, particulate impurities, metallic contaminants, and the natural oxide layer from the surface of silicon wafer 1, resulting in silicon wafer 1 with ≤5 particles larger than 0.1μm per cm² on its surface. 2 Metal impurity content ≤5×10 9 atoms / cm 2 This meets the requirements of subsequent phosphorus diffusion processes.

[0042] S2, Doping: The silicon wafer 1 is doped by diffusion process, and after doping, a phosphorus diffusion ohmic contact layer 2 is formed on the back side of the silicon wafer 1.

[0043] The element used for doping on silicon wafer 1 is phosphorus (P), which oriented the crystal to... <100> An N-type silicon wafer 1 is prepared with an N-type heavily doped layer through a diffusion process, and a phosphorus diffused ohmic contact layer 2 is formed on the back side of the silicon wafer 1 (where the back side of the silicon wafer 1 refers to...). Figure 1 (Bottom surface of silicon wafer 1).

[0044] S3, Oxidation: Dry oxygen oxidation is performed on silicon wafer 1 using an oxidation furnace to form a SiO2 masking layer 3 on the surface of silicon wafer 1;

[0045] Specifically, the silicon wafer 1 is subjected to dry oxidation at a temperature of 1000℃ for 30 minutes to form a SiO2 masking layer 3 on the surface of the silicon wafer 1.

[0046] S4. Photolithography: A photoresist film 4 is formed on the front side of silicon wafer 1 through a coating process. Then, pre-baking, exposure, and development are performed to obtain a tetragonal photoresist masking layer 4a. Finally, hardening, plasma etching, and photoresist removal are performed to form a tetragonal SiO2 masking layer pattern 3a on the front side of silicon wafer 1 (where the front side of silicon wafer 1 refers to the side away from the back side).

[0047] Specifically, a photoresist film 4 is coated on the surface of silicon wafer 1 by spin coating, pre-baked for 10 minutes, and then a photomask with a period of 5μm~50μm and a tetragonal arrangement is selected for exposure. It is developed using 0.7wt% KOH developer to obtain a tetragonal arrangement photoresist masking layer 4a. Then, it is hardened for 20 minutes, and the silicon wafer 1 is plasma etched for 60 seconds using sulfur hexafluoride (SF6) as the etching gas. Finally, the photoresist is removed, that is, a tetragonal arrangement SiO2 masking layer pattern 3a is formed on the front side of silicon wafer 1.

[0048] S5. Wet etching: Using the SiO2 masking layer pattern 3a formed by photolithography as a masking film, according to the anisotropic etching properties of silicon, the silicon wafer 1 is placed in KOH etching solution to prepare the inverted square pyramid structure induced pit 5.

[0049] Specifically, a 30wt% KOH solution is prepared and placed in an 80℃ water bath. The silicon wafer 1 is then immersed in the KOH solution for etching. The etching time depends on the pore size of the microchannels. For example, if the microchannel diameter is 10μm, the etching time is 10 minutes; if the microchannel diameter is 25μm, the etching time is 15-20 minutes.

[0050] S6. Photoelectrochemical etching: A three-electrode system was used to conduct the experiment in a polytetrafluoroethylene bath. A PARSTAT2273 potentiostat was selected for control. The etching electrolyte was a mixture of deionized water, hydrofluoric acid, isopropanol and X100 surfactant in a certain proportion. A silicon wafer 1 with an induced pit 5 structure was used as the substrate for photoelectrochemical etching to form a square array of silicon microchannels 6.

[0051] Specifically, a photoelectrochemical etching solution was prepared by mixing 1800 mL of deionized water, 180 mL of hydrofluoric acid, 180 mL of isopropanol and 2 mL of X100 surfactant. Using a photoelectrochemical etching device, the front side of silicon wafer 1 was placed on the etching port, the etching solution temperature was maintained at 23°C, and the etching was carried out for 13 hours. After etching was completed, silicon wafer 1 was removed to form a square array of silicon microchannels 6.

[0052] S7. Backside thinning: The silicon microchannel array 6 is placed in an oxidation furnace for oxidation. After oxidation, it is placed in a polytetrafluoroethylene fixture so that the exposed part of the backside of the silicon wafer 1 is immersed in hydrofluoric acid to remove the oxide layer. Then it is immersed in KOH solution for etching, thereby preparing the through-type microchannel array structure 1a.

[0053] Specifically, after cleaning and drying the photoelectrochemically etched silicon wafer 1, it is placed in an oxidation furnace for dry oxygen oxidation for 2 hours. After oxidation, it is placed in a polytetrafluoroethylene fixture, exposing only the back side of the silicon wafer 1 to contact with hydrofluoric acid to remove the back oxide layer. Subsequently, the silicon wafer 1 is immersed in a 30wt% KOH solution at 80℃ for etching, thereby preparing a through-type microchannel array structure 1a.

[0054] S8. Shaping: The silicon microchannel array 6 is shaped using TMAH solution to prepare a microchannel array structure 1b with a higher opening area ratio and smooth microchannel inner wall;

[0055] Specifically, before shaping, the silicon microchannel array 6 was first soaked in hydrofluoric acid and isopropanol for 5 minutes to remove the natural oxide layer. Then, the silicon microchannel array 6 was shaped using a 1wt% TMAH solution while maintaining the solution temperature at 40°C to prepare a microchannel array structure 1b with an opening area ratio greater than 70% and smooth inner walls of the microchannels.

[0056] The tetragonal silicon microchannel array 6 substrate was shaped using a 1wt% TMAH solution, which improved the opening area ratio, resulting in an opening area greater than 70%, and also improved the smoothness of the microchannel inner wall.

[0057] S9. Atomic Layer Deposition (ALD) Tungsten Film: Using the LabNano™ 9100 atomic layer deposition system from Innolux, a tungsten film 7 is deposited on the inner wall of the microchannel array structure 1b of the silicon microchannel array 6 through atomic layer deposition thin film technology.

[0058] Specifically, the silicon microchannel array 6 was ultrasonically cleaned with deionized water for 15 min, then mixed with 70 mL of concentrated sulfuric acid (98 wt%) and 30 mL of hydrogen peroxide solution (30 wt%) under cooling to prepare a piranha solution. The silicon microchannel array 6 substrate was placed in this solution and allowed to stand for 20 min, followed by ultrasonic cleaning to remove the piranha solution from the surface. The substrate was then removed and dried with nitrogen. Further, a tungsten film 7 was prepared using an ALD process at a pressure of 40 Pa, using Si₂H₆ (disilane) and WF₆ (tungsten hexafluoride) as precursors; the thickness of the tungsten film 7 was 50–300 nm.

[0059] S10, Pulse electroplating silver: Using a pulse electrodeposition device, the silicon microchannel array 6 is placed in a cyanide-free silver plating solution, and a silver film 8 is deposited on the tungsten film 7 by pulse electroplating.

[0060] Specifically, 20g of 5,5-dimethylhydantoin (DMH), 16g of potassium carbonate, and 8g of potassium pyrophosphate were dissolved in 160mL of deionized water and stirred until dissolved. Then, 6g of silver nitrate was dissolved in 40mL of deionized water and added to the above solution. The pH was adjusted to 11 with potassium hydroxide to complete the preparation of the DMH cyanide-free silver plating solution. Then, using a pulsed electrodeposition device, the silicon microchannel array 6 was placed in the cyanide-free silver plating solution, with a current of 10mA and a temperature of 35℃. A silver film 8 was deposited on the tungsten film 7 using pulsed electroplating; the thickness of the silver film 8 was 50~200nm.

[0061] S11. Filling the scintillator: GOS fluorescent material particles and UV adhesive are mixed in a specific ratio and then uniformly coated on the surface of silicon microchannel array 6. The silicon microchannel array 6 is then placed in a tube furnace and heated in a vacuum environment to the temperature at which the UV adhesive has the best fluidity. After that, atmospheric pressure is restored and the mixture is allowed to stand. Atmospheric pressure is used to fully fill the channels of silicon microchannel array 6 with GOS / UV composite scintillator adhesive 9. Finally, the mixture is cured with a UV lamp to obtain a gadolinium oxide X-ray scintillator screen based on a silicon microchannel array.

[0062] Specifically, UV adhesive and GOS phosphor particles are mixed in a certain proportion and placed on the surface of silicon microchannel array 6. The silicon microchannel array 6 is then placed in a tube furnace, and under vacuum conditions, the tube furnace is heated to 70°C. Afterward, atmospheric pressure is restored, allowing the GOS / UV composite scintillation adhesive 9 to fully fill the channels of the silicon microchannel array 6. Finally, it is cured by irradiation with a UV lamp. The UV adhesive selected has a refractive index between 2.0 and 2.4 after curing, making its refractive index close to that of the gadolinium oxysulfate phosphor used. The gadolinium oxysulfate phosphor is composed of Gd₂O₂S:Tb and has a refractive index of 2.2.

[0063] S12. Packaging: The surface of the gadolinium oxysulfate X-ray scintillator (GOS scintillator) based on silicon microchannel array is cleaned. Using thin film preparation technology, an aluminum film 10 is deposited on the front side and an aluminum oxide film 11 is deposited on the back side of the GOS scintillator to achieve double-sided packaging.

[0064] Specifically, firstly, the UV adhesive and GOS fluorescent particles remaining on the surface of the GOS flickering screen are removed. Then, a high-purity aluminum target with a purity of 99.99% is selected, and a magnetron sputtering process is initiated in a vacuum chamber environment. After aluminum atoms are bombarded and sputtered by high-energy particles, they are uniformly deposited on the front side of the GOS flickering screen. After the aluminum film 10 is deposited, the screen is removed and flipped over. Then, an aluminum oxide ceramic target with the same purity (99.99%) is selected, and aluminum oxide particles are sputtered and deposited on the back side of the GOS flickering screen using the same magnetron sputtering technology to form an aluminum oxide film 11. After the deposition process is completed, the screen is removed, completing the double-sided encapsulation of the GOS flickering screen.

[0065] A specific embodiment of the present invention is given below with reference to the accompanying drawings:

[0066] Example 1

[0067] like Figure 1 and 2 As shown, the method for fabricating a gadolinium oxysulfate X-ray scintillation screen based on a silicon microchannel array according to the present invention includes the following steps:

[0068] Silicon substrate pretreatment - corresponding step S1:

[0069] Using a thickness of 500μm, with crystal orientation of <100> The N-type silicon wafer 1 has a resistivity of 10~10000 Ω·cm. Subsequently, the silicon wafer 1 was subjected to a standard RCA cleaning process consisting of four steps: pre-cleaning, SC-1 cleaning, HF rinsing, and SC-2 cleaning. This process aimed to remove organic matter, particulate impurities, metallic contaminants, and the natural oxide layer from the surface of the silicon wafer 1, resulting in silicon wafer 1 with a surface particle count of ≤5 particles larger than 0.1μm / cm. 2 Metal impurity content ≤5×10 9 atoms / cm 2 This meets the requirements of subsequent phosphorus diffusion processes. See the process diagram below. Figure 1 (a).

[0070] Fabrication of tetragonal silicon microchannels - corresponding steps S2-S8:

[0071] (1) Phosphorus (P) doping is performed on silicon wafer 1 by diffusion process. After doping, a phosphorus diffusion ohmic contact layer 2 is formed on the back side of silicon wafer 1. See the schematic diagram of the process. Figure 1 (b);

[0072] (2) Dry oxidation of silicon wafer 1 is performed in an oxidation furnace at a temperature of 1000℃ for 30 minutes to form a SiO2 masking layer 3 on the surface of silicon wafer 1. See the schematic diagram of the process. Figure 1 (c);

[0073] (3) A photoresist film 4 was spin-coated onto the front surface of silicon wafer 1, pre-baked for 10 min, and then exposed to a photomask with a period of 25 μm and a tetragonal arrangement. Developed with 0.7 wt% KOH developer, a photoresist masking layer 4a with a period of 25 μm and a tetragonal arrangement was obtained. After hardening for 20 min, the silicon wafer 1 was plasma etched with sulfur hexafluoride (SF6) as the etching gas for 60 s. Finally, the photoresist was removed to obtain a tetragonal SiO2 masking layer pattern 3a on the front surface of silicon wafer 1. See the schematic diagram of the process. Figure 1 (df);

[0074] (4) Using the SiO2 masking layer pattern 3a formed by photolithography as a masking film, based on the anisotropic etching properties of silicon, a 30wt% KOH solution was heated in an 80℃ water bath, and the silicon wafer 1 was immersed in the 30wt% KOH etching solution for 15 minutes to prepare the inverted quadrangular pyramidal structure induced pit 5. See the schematic diagram of the process. Figure 1 (g);

[0075] (5) A three-electrode system was selected and the experiment was conducted in a polytetrafluoroethylene bath. A PARSTAT2273 potentiostat was used for control. The electrolyte for etching was prepared by mixing 1800 mL of deionized water, 180 mL of hydrofluoric acid, 180 mL of isopropanol and 2 mL of X100 surfactant. Using a photoelectrochemical etching device, the silicon wafer 1 with the induced pit 5 structure was used as the substrate for photoelectrochemical etching. The front of the silicon wafer 1 was placed on the etching pit. The temperature of the etching solution was maintained at 23℃ and the etching was carried out for 13 hours. After etching, the silicon wafer 1 was removed, forming a square array of silicon microchannels 6. See the schematic diagram of the process. Figure 1 (h);

[0076] (6) After cleaning and drying the photoelectrochemically etched silicon wafer 1, it is placed in an oxidation furnace for dry oxygen oxidation for 2 hours. After oxidation, it is placed in a polytetrafluoroethylene fixture, and the exposed part of the back of the silicon wafer 1 is immersed in hydrofluoric acid to remove the oxide layer. Then it is immersed in a 30wt% KOH solution at 80℃ for etching, thereby preparing the through-type microchannel array structure 1a. See the schematic diagram of the process. Figure 1 (i);

[0077] (7) First, soak the silicon microchannel array 6 in hydrofluoric acid and isopropanol for 5 min to remove the natural oxide layer. Then, use a 1 wt% TMAH solution to shape the silicon microchannel array 6 for 20 min while maintaining the solution temperature at 40°C. This will prepare a microchannel array structure 1b with an opening area ratio greater than 70% and smooth inner walls. See the schematic diagram of the process. Figure 1 (j); Figure 3 This is a scanning electron microscope image of a silicon microchannel array with a four-way channel arrangement, showing the microchannel 12 and the microchannel wall 13 of the silicon microchannel array.

[0078] Preparation of microchannel composite membranes - corresponding steps S9-S10:

[0079] (1) The microchannel array structure 1b was ultrasonically cleaned with deionized water for 15 min, and then mixed with 70 mL of concentrated sulfuric acid (98 wt%) and 30 mL of hydrogen peroxide solution (30 wt%) under cooling to prepare the piranha solution. The silicon microchannel array 6 substrate was placed in the solution and left to stand for 20 min. Then, it was ultrasonically cleaned to remove the piranha solution from the surface. After removing the substrate and drying it with nitrogen, a tungsten film 7 with a thickness of 200 nm was prepared by using the LabNano™ 9100 atomic layer deposition system of Innolux, with Si2H6 (silane) and WF6 (tungsten hexafluoride) as precursors and a pressure of 40 Pa. See the schematic diagram of the process. Figure 1 (k);

[0080] (2) Dissolve 20g of 5,5-dimethylhydantoin (DMH), 16g of potassium carbonate, and 8g of potassium pyrophosphate in 160mL of deionized water and stir until dissolved. Then dissolve 6g of silver nitrate in 40mL of deionized water and add it to the above solution. Adjust the pH to 11 with potassium hydroxide to complete the preparation of the DMH cyanide-free silver plating solution. Then, using a pulse electrodeposition device, place the silicon microchannel array 6 in the cyanide-free silver plating solution and deposit a silver film 8 on the tungsten film 7 on the inner wall of the microchannel using pulse electroplating. The thickness of the silver film 8 is 100nm, the current is 10mA, and the temperature is 35℃. See the schematic diagram of the process. Figure 1 (l).

[0081] Fill the flickering screen - corresponding step S11:

[0082] A UV adhesive (with a refractive index between 2.0 and 2.4, making its refractive index close to that of the gadolinium oxysulfate phosphor used) and GOS phosphor particles (Gd₂O₂S:Tb, with a refractive index of 2.2) were mixed at a mass ratio of 2:3 and uniformly coated onto the surface of a silicon microchannel array 6. The silicon microchannel array 6 was then placed in a tube furnace, and the furnace was heated to 70°C under vacuum conditions. Subsequently, atmospheric pressure was restored, allowing the GOS / UV composite scintillation adhesive 9 to fully fill the channels of the silicon microchannel array 6. Finally, the mixture was cured using an ultraviolet lamp to obtain a gadolinium oxysulfate X-ray scintillation screen (GOS scintillation screen) based on a silicon microchannel array. See the schematic diagram for the process. Figure 1 (m).

[0083] Packaging - corresponding step S12:

[0084] First, remove the UV adhesive and GOS fluorescent particles remaining on the surface of the GOS flicker screen. Then, using a high-purity aluminum target with 99.99% purity, initiate a magnetron sputtering process in a vacuum chamber environment. This allows aluminum atoms to be bombarded and sputtered by high-energy particles, uniformly depositing onto the front side of the GOS flicker screen. After the aluminum layer deposition is complete, remove and flip the GOS flicker screen. Next, using an alumina ceramic target of the same purity (99.99%), use magnetron sputtering technology to sputter and deposit alumina particles onto the back side of the GOS flicker screen. After the deposition process is complete, remove the screen. Thus, an aluminum film 10 is deposited on the front side of the GOS flicker screen, and an aluminum oxide film 11 is deposited on the back side, completing the double-sided encapsulation of the GOS flicker screen. See the schematic diagram for the process. Figure 1 (n).

[0085] A photograph of the front metallographic microscope of the gadolinium oxysulfate X-ray scintillation screen of Embodiment 1 of the present invention is shown below. Figure 4 .

[0086] The gadolinium oxysulfide X-ray scintillation screen prepared in Example 1 was used for X-ray imaging of a resolution plate. See the image below. Figure 5 .

[0087] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for fabricating a gadolinium oxysulfate X-ray scintillation screen based on a silicon microchannel array, characterized in that, Includes the following steps: S1. Pretreatment: Selecting the crystal orientation as... <100> N-type silicon wafer (1) with a resistivity of 10~10000 Then, the silicon wafer (1) was subjected to surface cleaning treatment to obtain a clean silicon wafer (1); S2, Doping: Phosphorus doping is performed on the silicon wafer (1) by diffusion process. After doping, a phosphorus diffusion ohmic contact layer (2) is formed on the back side of the silicon wafer (1). S3, Oxidation: Dry oxygen oxidation is performed on the silicon wafer (1) to form a SiO2 masking layer (3) on the surface of the silicon wafer (1); S4, Photolithography: A photoresist film (4) is formed on the front side of the silicon wafer (1) by coating, and then pre-baking, exposure and development are performed to obtain a photoresist masking layer (4a) arranged in a square. Finally, hard film, plasma etching and photoresist removal are performed to form a SiO2 masking layer pattern (3a) arranged in a square on the front side of the silicon wafer (1). S5. Wet etching: Using the SiO2 masking layer pattern (3a) formed by photolithography as a masking film, the silicon wafer (1) is placed in potassium hydroxide (KOH) etching solution to prepare an inverted quadrangular pyramid structure induced pit (5). S6. Photoelectrochemical etching: A three-electrode system is selected. The etching electrolyte is a mixture of deionized water, hydrofluoric acid, isopropanol and X100 surfactant. A silicon wafer (1) with an induced pit (5) structure is used as the substrate for photoelectrochemical etching to form a square array of silicon microchannels (6). S7. Back thinning: The silicon microchannel array (6) is oxidized and then placed in a polytetrafluoroethylene fixture. The exposed part of the back of the silicon wafer (1) is immersed in hydrofluoric acid to remove the oxide layer, and then immersed in KOH solution for etching, thereby preparing a through-type microchannel array structure (1a). S8. Shaping: The silicon microchannel array (6) is shaped using tetramethylammonium hydroxide solution (TMAH) to prepare a microchannel array structure (1b) with a higher opening area ratio than the through-type microchannel array structure (1a) and a smooth microchannel inner wall. S9, Atomic layer deposition of tungsten film: A tungsten film (7) is deposited on the inner wall of the microchannel array structure (1b) of the silicon microchannel array (6) by atomic layer deposition thin film process; S10, Pulse electroplating silver film (8): The silicon microchannel array (6) is placed in a cyanide-free silver plating solution, and a silver film (8) is deposited on the tungsten film (7) by pulse electroplating. S11, Filling the scintillator: After mixing gadolinium oxysulfate (GOS) fluorescent material particles and UV adhesive in a certain proportion, the mixture is uniformly coated on the surface of the silicon microchannel array (6). The silicon microchannel array (6) is then placed in a tube furnace and heated to the temperature at which the UV adhesive has the best fluidity under vacuum. Then, atmospheric pressure is restored, and the GOS / UV composite scintillator adhesive (9) is filled into the channels of the silicon microchannel array (6) using atmospheric pressure. Finally, after curing, a gadolinium oxysulfate X-ray scintillator screen based on the silicon microchannel array is obtained. S12. Packaging: The surface of the gadolinium oxysulfate X-ray scintillation screen based on silicon microchannel array is cleaned. Using thin film preparation technology, an aluminum film (10) is deposited on the front side and an aluminum oxide film (11) is deposited on the back side of the gadolinium oxysulfate X-ray scintillation screen based on silicon microchannel array to achieve double-sided packaging.

2. The preparation method according to claim 1, characterized in that, In step S3, the temperature for dry oxidation of the silicon wafer (1) is 1000℃ and the oxidation time is 30min.

3. The preparation method according to claim 1, characterized in that, In step S4, photolithography uses a mask with a period of 5μm~50μm and arranged in a square for exposure.

4. The preparation method according to claim 1, characterized in that, In step S6, the volume ratio of deionized water, hydrofluoric acid, isopropanol, and X100 surfactant is 1800mL:180mL:180mL:2mL, the photoelectrochemical etching temperature is 23℃, and the etching time is 13h.

5. The preparation method according to claim 1, characterized in that, In step S8, the silicon microchannel array (6) is shaped using a 1wt% TMAH solution to prepare a microchannel array structure (1b) with an opening area ratio greater than 70% and smooth inner walls of the microchannels.

6. The preparation method according to claim 1, characterized in that, In step S9, the thickness of the tungsten film (7) is 50~300nm.

7. The preparation method according to claim 1, characterized in that, In step S10, the thickness of the silver film (8) is 50~200nm.

8. The preparation method according to claim 1, characterized in that, In step S11, the UV adhesive is a UV adhesive with a refractive index between 2.0 and 2.4 after curing, and the gadolinium oxysulfate phosphor is composed of Gd2O2S:Tb with a refractive index of 2.2; the UV adhesive is heated to the temperature of 70°C in a vacuum environment where it has the best fluidity.

9. A gadolinium oxysulfate X-ray scintillation screen based on a silicon microchannel array, prepared by the preparation method according to any one of claims 1-8.

10. The application of the gadolinium oxysulfate X-ray scintillation screen based on silicon microchannel array as described in claim 9 in medical diagnosis, industrial non-destructive testing, security inspection or academic research.

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