A method for preparing a metal electrode array of a perovskite x-ray photon counting detector

Abstract

The application provides a preparation method of a perovskite X-ray photon counting detector metal electrode array, comprising the following steps: S1, establishing evaporation diffusion compensation parameters according to the size of a target metal electrode array; S2, preparing a metal mask plate with a pre-subtracted opening size according to the evaporation diffusion compensation parameters; S3, closely attaching and aligning the metal mask plate to one side of a perovskite to be prepared; and the gap between the metal mask plate and the perovskite is 0-50 microns; S4, forming a metal electrode array by evaporation in a vacuum environment: under vacuum conditions, the metal material passes through the metal mask plate opening and is deposited on the surface of the perovskite by evaporation, the metal mask plate is removed, and the required perovskite metal electrode array is obtained. By the combination of "close attachment + size pre-subtraction", the target metal electrode array can be obtained without using a photolithography process.

Description

Technical Field

[0001] This invention belongs to the field of perovskite semiconductor device fabrication technology, and particularly relates to a method for fabricating a metal electrode array for a perovskite X-ray photon counting detector. Background Technology

[0002] Single-crystal perovskite materials possess characteristics such as high atomic number elemental composition, high carrier mobility-lifetime product, high X-ray absorption capacity, and low-temperature machinability, making them suitable for direct-conversion X-ray photon counting detectors. For area-array X-ray photon counting detectors, a regular array of metal electrodes needs to be fabricated on one or both sides of the single-crystal perovskite to form pixelated collection electrodes, common electrodes, or interconnect electrodes that match the readout backplane of thin-film transistors (TFTs). The size, edge morphology, spacing consistency, and surface damage of the metal electrode array directly affect the device's dark current, crosstalk, noise, spatial resolution, and subsequent flip-chip interconnect yield.

[0003] Currently, commonly used methods for fabricating metal electrode arrays include photolithography, lift-off, wet etching, dry etching, and conventional metal mask evaporation. While photolithography can achieve high pattern resolution, it typically requires spin-coating photoresist, pre-baking, exposure, development, metal deposition, lift-off, and resist removal on the perovskite sample surface. Perovskite materials are generally sensitive to polar solvents, moisture, thermal stress, and chemical reagents. Developer, resist remover, stripping solution, and photoresist residues can lead to perovskite surface swelling, ion migration, increased surface defects, increased roughness, or deterioration of electrical properties. For single-crystal perovskite samples, prolonged immersion and repeated washing can easily cause edge chipping, surface contamination, and crystal damage.

[0004] Therefore, metal mask evaporation, which avoids coating photoresist on the perovskite surface, has become the mainstream method for fabricating perovskite metal electrode arrays. However, gaps are always unavoidable when the metal mask is bonded to the perovskite. During metal evaporation, metal ions will produce a shadowing effect and lateral diffusion at the edges of the opening in the metal mask, causing the actual electrode size to be larger than the mask opening size. As the electrode spacing in the metal electrode array decreases, edge diffusion will cause problems such as oversized electrodes, insufficient spacing, short circuits between adjacent electrodes, and inconsistent array sizes. Especially in the case of large-area single-crystal perovskite samples or surfaces with slight warping, local suspension of the metal mask will further amplify the size diffusion. Summary of the Invention

[0005] In view of this, the present invention provides a method for fabricating a metal electrode array for a perovskite X-ray photon counting detector, which achieves the fabrication of metal electrodes with controllable size and good array consistency through a metal mask template.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: A method for fabricating a metal electrode array for a perovskite X-ray photon counting detector, comprising: S1: Establish vapor deposition diffusion compensation parameters based on the size of the target metal electrode array: pre-calibrate the lateral diffusion size of the metal vapor deposition electrode relative to the opening of the metal mask based on the metal vapor deposition conditions and the actual state of the perovskite surface. S2: Prepare a metal mask with pre-subtracted opening size based on evaporation diffusion compensation parameters: Prepare a metal mask with pre-subtracted opening size by subtracting the lateral diffusion size on one side based on the size of the target metal electrode array; S3: The metal mask is tightly attached to one side of the perovskite electrode to be prepared and aligned, and the gap between the metal mask and the perovskite is 0-50 μm, preferably 0-10 μm; S5: Forming a metal electrode array in a vacuum environment by vapor deposition: Under vacuum conditions, metal material is deposited on the perovskite surface by vapor deposition through the opening of a metal mask. The metal mask is then removed to obtain the desired perovskite metal electrode array.

[0007] The perovskite can be a single-crystal perovskite wafer, a single-crystal perovskite sheet, a perovskite thick film, or a perovskite epitaxial layer, preferably a single-crystal perovskite sample for direct X-ray detection. Before vacuum evaporation, the perovskite surface undergoes mechanical thinning and surface cleaning. The target metal electrode array can be a pixel electrode, a readout electrode, a common electrode, a strip electrode, an interdigitated electrode, or a combination thereof. The dimensions of the target metal electrode array include, but are not limited to, electrode width Wt, electrode length Lt, electrode diameter Dt, electrode spacing Pt, and pixel array arrangement, which is typically a regular arrangement.

[0008] Preferably, the vapor deposition diffusion compensation parameters in step S1 are calibrated through testing, specifically as follows: A perovskite test sample and a test metal mask with a known opening size are provided. The perovskite test sample has the same perovskite material and thickness as the metal electrode array to be prepared. The thickness, material, and opening process of the test metal mask are exactly the same as those of the metal mask to be prepared. Using the test metal mask, the test metal electrode array is prepared on the perovskite test sample by vacuum evaporation. The vacuum degree, evaporation source distance, evaporation angle, deposition rate, metal material, and deposition thickness are completely consistent with those used in the subsequent evaporation of the target metal electrode array. Then, the size of the metal electrodes in the test metal electrode array is measured, and the difference between the size of the test metal electrodes and the opening size of the test metal mask is calculated to obtain the unilateral lateral diffusion size δ.

[0009] Preferably, when the opening shape of the test metal mask is rectangular, the length of the opening is L. 开口Width is W 开口 The metal electrodes in the prepared test metal electrode array are also rectangular in shape, and the length of the metal electrodes is L. 电极 Width is W 电极 ; if the lateral diffusion dimensions δ on one side are δx and δy respectively, then δx = (W 电极 -W 开口 ) / 2, δy=(L 电极 -L 开口 ) / 2; If the opening shape of the test metal mask is circular, the diameter of the opening is D. 开口 The metal electrodes in the prepared test metal electrode array are also circular in shape, with a diameter of D. 电极 Then the lateral diffusion dimension on one side is δ=D 电极 -D 开口 .

[0010] Preferably, when the target metal electrode array is rectangular, the dimensions of the target metal electrode array include the width Wt and the target length Lt. Then, the opening width Wm of the metal mask is Wt-2δx, and the opening length Lm of the metal mask is Lt-2δy. If the target metal electrode array is circular, and the size of the target metal electrode array includes the diameter Dt, then the opening diameter of the metal mask Dm = Dt - 2δ.

[0011] Preferably, the close bonding between the metal mask and the perovskite can be achieved through methods such as vacuum adsorption stage or magnetic clamping. The side of the metal mask facing the perovskite is polished or planarized to reduce warping and local gaps in the metal mask.

[0012] Preferably, the metal mask is made of any one of stainless steel, molybdenum, nickel, nickel-cobalt alloy, copper, titanium, or composite metal materials; the opening of the metal mask can be prepared by laser cutting, precision etching, electroforming, micro-milling, or a combination thereof.

[0013] The thickness of the metal mask is 20-500 μm, preferably 30-150 μm.

[0014] Preferably, the target metal electrode array is made of any one or a combination of Au, Ag, Al, Cu, Cr, Ti, Ni or Pt. The dimensions of the target metal electrode array include its thickness, which is 5-500 nm, preferably 20-200 nm.

[0015] Preferably, the metal evaporation in step S5 is any one of thermal evaporation, electron beam evaporation, or resistance evaporation; during the metal evaporation, the perovskite temperature does not exceed 80°C, and more preferably does not exceed 60°C, in order to reduce thermal stress and the risk of thermal damage to the perovskite material.

[0016] Because of the above technical solutions, this invention has the following advantages and positive effects compared with the prior art: The first invention uses a metal mask to deposit metal electrodes on perovskite to prepare an X-ray photon counting detector metal electrode array. This eliminates the need for photoresist coating, development, photoresist removal and stripping on the perovskite surface, thus avoiding prolonged contact between chemical liquids and the perovskite surface. Second, the close bonding between the metal mask and the perovskite can significantly reduce the shading effect during vapor deposition. Third, by pre-subtracting the diffusion size, a metal electrode array size closer to the design value can be obtained; Fourth, the process is simple, low-temperature, and low-damage, making it suitable for the fabrication of pixel electrodes before interconnection between single-crystal perovskite X-ray photon counting detectors and TFT readout backplanes. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the fabrication process of the metal electrode array for the perovskite X-ray photon counting detector of the present invention. Figure 2 Image of the metal electrode array prepared in Example 1 of this invention; Figure 3 This is an image of the metal electrode array prepared in Comparative Example 2 of the present invention.

[0018] 1-Metal mask; 2-Opening; 3-Perovskite; 4-Base; 5-Metal electrode array. Detailed Implementation

[0019] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a method for fabricating a perovskite X-ray photon counting detector metal electrode array according to the present invention. The advantages and features of the present invention will become clearer from the following description.

[0020] A metal electrode array refers to a structure in which each electrode pattern is arranged in regular rows and columns. A metal mask template is required to match the metal electrode array, i.e., ... Figure 1As shown, the metal mask 1 has the same array of openings 2. The perovskite 3 is fixed on the base 4. The metal mask 1 covers one side of the perovskite 3 where the metal electrode array 5 is to be prepared. Then, a thin film is deposited on the upper side of the metal mask 1. After deposition, the metal mask 1 is removed. The part covered by the metal mask 1 leaves no film on the perovskite 3, while the opening 2 of the metal mask 1 leaves a film on the surface of the perovskite 3, forming the metal electrode array 5. Because there is a gap between the metal mask 1 and the perovskite 3 when they are attached, a shadow effect and lateral diffusion are generated at the edge of the opening 2, making the actual electrode size larger than the mask opening size.

[0021] In this invention, the metal mask does not function as a simple shield, but rather forms the smallest possible gap with the perovskite surface and compensates for unavoidable lateral diffusion at the edges during the patterning stage. By combining "tight bonding + size pre-subtraction," the target metal electrode array can be obtained without photolithography. Therefore, the core idea of ​​this invention is twofold: firstly, by tightly bonding a high-flatness metal mask to the perovskite surface, the gap between the metal mask and the perovskite is reduced, thereby suppressing lateral diffusion at the metal electrode edges during evaporation; secondly, during the metal mask design stage, the opening of the metal mask is pre-subtracted based on the calibrated lateral diffusion size to prepare an array opening that matches the target metal electrode array, ensuring that the final evaporated metal electrode array size matches the target electrode size. This method enables the creation of metal electrodes with controllable dimensions and excellent array consistency.

[0022] Example 1

[0023] A single-crystal perovskite sample for direct X-ray detection was selected. The surface of the sample to be used for electrode fabrication had undergone mechanical thinning and surface cleaning. The goal was to fabricate a metal electrode array on this surface, with a target individual electrode size of 200 μm × 200 μm, a target electrode center-to-center spacing of 300 μm, and an array arrangement of regular squares.

[0024] First, diffusion calibration was performed using a test metal mask and a test perovskite sample. Under the same evaporation conditions, the opening size of the test metal mask was 190 μm × 190 μm, and the size of the test metal electrode after evaporation was measured to be 200 μm × 200 μm. Thus, under the same metal mask thickness, sample bonding method, and evaporation conditions, the lateral diffusion size on one side was determined to be δx = 5 μm and δy = 5 μm.

[0025] Subsequently, based on the target electrode dimensions Wt=200μm, Lt=200μm and the calibrated diffusion dimensions δx=5μm, δy=5μm, the aperture dimensions of the formal metal mask were designed to be Wm=190μm, Lm=190μm, with the center-to-center spacing of the apertures maintained at 500μm. The metal mask was made of a 100μm thick stainless steel sheet, with an array of apertures formed by laser cutting, and the side facing the perovskite sample was planarized.

[0026] Then, the single-crystal perovskite sample was fixed on a high-flatness vacuum adsorption stage, and the metal mask with the prepared array openings was placed on the side of the sample where the electrode was to be prepared. The array pattern was aligned using positioning pins and alignment marks. The metal mask was then pressed tightly using an elastic frame and low-stress counterweight to ensure a close fit between the metal mask and the sample surface, with the gap G controlled within the range of 0-10 μm.

[0027] Finally, the assembled sample and metal mask are placed in a vacuum evaporation apparatus. A Cr / Au composite metal layer is deposited at a temperature not exceeding 60°C, with the Cr layer having a thickness of 2-10 nm and the Au layer a thickness of 30-150 nm. After evaporation, the sample is allowed to cool, the pressure frame is released, and the metal mask is removed, thus obtaining a metal electrode array of the target size on the surface of the single-crystal perovskite sample.

[0028] The metal electrode array prepared by the above method is as follows: Figure 2 As shown, its size is close to the target of 200μm×200μm, the electrode edges are clear, the array spacing is consistent, and it has not been immersed in developer, resist remover and stripping solution. The risk of sample surface contamination and chemical damage is significantly reduced, making it suitable for subsequent flip-chip interconnect or packaging testing with TFT readout substrate.

[0029] Example 2

[0030] The difference between Example 2 and Example 1 is that the target metal electrode array is a rectangular electrode array with a target electrode width of Wt = 100 μm, a target electrode length of Lt = 200 μm, and a target electrode spacing of 100 μm. Through testing and calibration, the lateral diffusion dimensions on one side were found to be δx = 4 μm and δy = 5 μm. Therefore, the width of the strip opening in the metal mask was designed to be 92 μm, and the length to be 190 μm. The center position of the strip opening was set according to the center position of the target electrode. Then, the array opening was formed by precision etching, and the side facing the perovskite was planarized.

[0031] By using the same tight bonding method as in Example 1, the metal mask with the prepared array openings is tightly bonded to the perovskite, and then metal evaporation is performed. The final strip metal electrode has a linewidth of nearly 100 μm and the line spacing remains stable, avoiding the problems of excessive linewidth and insufficient line spacing caused by edge diffusion in ordinary mask evaporation.

[0032] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the target metal electrode array of Example 1 was prepared on the surface of a single-crystal perovskite sample using a conventional photoresist stripping process. Specifically, this includes steps such as spin-coating photoresist onto the sample surface, pre-baking, exposure, development, metal evaporation, stripping, and photoresist removal.

[0033] Comparative analysis revealed that while conventional photolithography can achieve high pattern precision, perovskite samples require contact with developing solutions, stripping solutions, and resist removers, and undergo baking and multiple cleaning steps. This can easily lead to swelling, corrosion, residual resist, ion migration, and increased surface defects on the single-crystal perovskite surface. For X-ray photon counting detector array samples, these damages can cause increased dark current, decreased pixel uniformity, and reduced device yield.

[0034] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that a common metal mask was used for vapor deposition, and the square array opening size of the metal mask was 200 μm, to prepare the same target metal electrode array as in Example 1.

[0035] The metal mask is closely bonded to the perovskite sample, and the target metal electrode array is prepared by direct metal evaporation using the metal mask. The metal evaporation conditions are exactly the same as in Example 1.

[0036] The prepared metal electrode is as follows Figure 3 As shown, although the metal mask and the sample are tightly fitted, the mechanical gap between them causes significant shadowing and lateral diffusion at the opening edges during the evaporation process. This results in the actual metal electrode size being larger than the mask opening size, reduced spacing between adjacent electrodes, blurred electrode edges, and even short circuits between adjacent electrodes in some cases. For metal electrode arrays with small pixel pitch, these problems of reduced spacing between adjacent electrodes, blurred edges, and even short circuits are prone to occur, making it difficult to meet the requirements for fabricating high-density perovskite X-ray photon counting detector arrays.

[0037] Through repeated verification, this embodiment demonstrates that by using a tightly fitted metal mask and pre-subtracting the diffusion size during the design of the metal mask, a perovskite metal electrode array with controllable dimensions can be fabricated without using photolithography. This avoids damage to the perovskite sample caused by development and resist removal, thereby improving the consistency of the metal electrode array and the device fabrication yield.

[0038] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they shall still fall within the protection scope of the present invention.

Claims

1. A method for fabricating a metal electrode array for a perovskite X-ray photon counting detector, characterized in that, include: S1: Establish vapor deposition diffusion compensation parameters based on the size of the target metal electrode array; S2: Prepare a metal mask template with pre-subtracted opening size based on the vapor deposition diffusion compensation parameters; S3: The metal mask is tightly attached to the perovskite and aligned, and the gap between the metal mask and the perovskite is 0-50μm; S4: Form a metal electrode array by vapor deposition in a vacuum environment, remove the metal mask, and obtain the desired perovskite metal electrode array.

2. The method for fabricating the metal electrode array of the perovskite X-ray photon counting detector according to claim 1, characterized in that, The specific steps for establishing the vapor deposition diffusion compensation parameters in step S1 are as follows: A perovskite test sample and a test metal mask with a known opening size are provided. Using the test metal mask, a test metal electrode array is prepared on the perovskite test sample. The size of the metal electrodes in the test metal electrode array is measured, and the difference between the size of the test metal electrodes and the opening size of the test metal mask is calculated to obtain the unilateral lateral diffusion size δ.

3. The method for fabricating the metal electrode array of the perovskite X-ray photon counting detector according to claim 2, characterized in that, When the opening shape of the test metal mask is rectangular, the length of the opening is L. 开口 Width is W 开口 The metal electrodes in the prepared test metal electrode array are also rectangular in shape, and the length of the metal electrodes is L. 电极 Width is W 电极 ; if the lateral diffusion dimensions δ on one side are δx and δy respectively, then δx = (W 电极 -W 开口 ) / 2, δy=(L 电极 -L 开口 ) / 2; If the opening shape of the test metal mask is circular, the diameter of the opening is D. 开口 The metal electrodes in the prepared test metal electrode array are also circular in shape, with a diameter of D. 电极 Then the lateral diffusion dimension on one side is δ=D 电极 -D 开口 .

4. The method for fabricating the metal electrode array of the perovskite X-ray photon counting detector according to claim 2 or 1, characterized in that, When the target metal electrode array is rectangular, the dimensions of the target metal electrode array include the width Wt and the target length Lt. Then, the opening width of the metal mask Wm = Wt - 2δx and the opening length of the metal mask Lm = Lt - 2δy. If the target metal electrode array is circular, and the size of the target metal electrode array includes the diameter Dt, then the opening diameter of the metal mask Dm = Dt - 2δ.

5. The method for fabricating the metal electrode array of the perovskite X-ray photon counting detector according to claim 1, characterized in that, The metal mask is polished or planed on the side facing the perovskite, and the gap between the metal mask and the perovskite is 0-10 μm.

6. The method for fabricating the metal electrode array of the perovskite X-ray photon counting detector according to claim 1, characterized in that, The material of the metal mask is any one of stainless steel, molybdenum, nickel, nickel-cobalt alloy, copper, titanium, or composite metal materials; The thickness of the metal mask is 20-500 μm.

7. The method for fabricating the metal electrode array of the perovskite X-ray photon counting detector according to claim 1, characterized in that, The target metal electrode array is made of any one or a combination of Au, Ag, Al, Cu, Cr, Ti, Ni or Pt. The dimensions of the target metal electrode array include its thickness, which is 5-500 nm.

8. The method for fabricating the metal electrode array of the perovskite X-ray photon counting detector according to claim 1, characterized in that, The vapor deposition method in step S5 is any one of thermal vapor deposition, electron beam vapor deposition, or resistance vapor deposition; during the vapor deposition, the temperature of the perovskite does not exceed 80°C.

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