Table-top infrared focal plane array and table-top electrode preparation method

Abstract

The invention relates to the technical field of infrared focal plane detectors, and provides a mesa type infrared focal plane array and a mesa electrode preparation method. The array comprises a pixel electrode area which is provided with a plurality of pixel table tops serving as pixel electrodes, and the pixel table tops are separated by first isolation grooves with the width smaller than the preset width and the depth larger than the preset depth; the public electrode area is provided with a plurality of public electrode table boards separated by first isolation grooves or second isolation grooves, at least one second isolation groove is formed around each public electrode table board, the width and the depth of the second isolation groove are both larger than those of the first isolation groove, the first isolation groove and the second isolation groove are synchronously obtained through one-time etching, and the bottom of the first isolation groove of the public electrode area is provided with a plurality of second isolation grooves. Conductive metal is deposited on the bottom and the side wall of the second isolation groove and the table surface of the common electrode, so that the common electrode is led to the table surface from the bottom of the epitaxial material. The objective of the invention is to solve the problem that an infrared focal plane array in the prior art is difficult to give consideration to large tabletop duty ratio, small transverse diffusion current and stable conductive path.

Description

Technical Field

[0001] The invention relates to the technical field of infrared focal plane detectors, in particular to a table-type infrared focal plane array and a table electrode preparation method. Background Art

[0002] Infrared focal plane detectors are widely used in military and civilian fields. Their components are mainly composed of infrared focal plane arrays and readout circuits, which are connected by metal electrodes. As infrared focal plane detectors develop towards ultra-large arrays and ultra-small pixels, it is necessary to separate the pixels in the table-type infrared focal plane array through isolation grooves, and minimize the width of the isolation grooves to increase the table duty cycle, so as to obtain better detector response performance.

[0003] The table units in the infrared focal plane array can be divided into pixel table and common electrode table. The pixel table is the basic unit in the infrared focal plane array responsible for detecting infrared radiation and converting it into electrical signals. The common electrode table is the output port connected to the common end electrode, which can provide a common potential reference or signal transmission path for the pixel table.

[0004] In the existing actual product structure, the width of the isolation groove between the pixel mesas, the width of the isolation groove between the pixel mesas and the common electrode mesas, and the width of the isolation groove between the common electrode mesas are all the same. Therefore, when the width of the above-mentioned isolation groove is reduced to increase the mesa duty cycle, on the one hand, the etching difficulty of the infrared focal plane array will increase with the increase of the aspect ratio of the isolation groove. On the other hand, the metal electrode located on the side wall of the above-mentioned isolation groove is difficult to prepare, and the prepared metal electrode has the problem of difficulty in climbing and easy breakage of the conductive path resulting in poor electrical connection, which will affect the output of the photocurrent signal in the infrared focal plane detector and thus reduce the detector performance.

[0005] With regard to the problem that infrared focal plane arrays in related technologies have difficulty in taking into account the large table space occupancy, small lateral diffusion current, and relatively stable conductivity of metal electrodes, no effective solution has been proposed so far. Summary of the invention

[0006] The present invention provides a table-type infrared focal plane array and a table electrode preparation method, which at least solves the problem in the related art that the infrared focal plane array is difficult to take into account the large table space ratio, small lateral diffusion current, and stable metal electrode conductivity.

[0007] The present invention provides a table-type infrared focal plane array according to an embodiment of the invention, including a pixel electrode area and a common electrode area, wherein the pixel electrode area includes a plurality of pixel table surfaces, and the common electrode area includes a plurality of common electrode table surfaces; each pixel table surface is separated by a first isolation groove, wherein a conductive metal is deposited on the surface of the pixel table surface as a pixel electrode of the infrared focal plane array, and the first isolation groove is an isolation groove with a width less than a preset width and a depth greater than a preset depth; each common electrode table surface is separated by a first isolation groove or a second isolation groove, and at least one second isolation groove is etched around each common electrode table surface, wherein the second isolation groove is an isolation groove with a width greater than the width of the first isolation groove and a depth greater than the depth of the first isolation groove, and the first isolation groove and the second isolation groove are obtained synchronously by one etching; in the common electrode area, the bottom of the first isolation groove, the bottom and sidewalls of the second isolation groove, and the surface of the common electrode table surface are all deposited with conductive metal, which is used to lead the common electrode of the above-mentioned infrared focal plane array from the bottom of the epitaxial material of the above-mentioned infrared focal plane array to the surface of the common electrode table surface. It can be understood that the width of the first isolation groove is smaller than the preset width, that is, the first isolation groove is narrower, which can increase the table duty cycle; the depth of the first isolation groove is greater than the preset depth, that is, the first isolation groove is etched deeper, which can reduce the lateral diffusion current; the table structure of the above-mentioned common electrode area can provide a stable conductive path.

[0008] The table-type infrared focal plane array provided by the embodiment of the present invention has the first isolation groove being an equal-width isolation groove; the second isolation groove being an equal-width isolation groove whose width is greater than that of the first isolation groove, or an unequal-width isolation groove whose minimum width is greater than that of the first isolation groove; the width of the unequal-width isolation groove gradually increases in the length direction of the isolation groove, and the depth of the unequal-width isolation groove increases as the width increases.

[0009] According to the table-type infrared focal plane array provided by the embodiment of the present invention, second isolation grooves are etched on opposite sides of the common electrode table, and when the second isolation grooves are non-equal width isolation grooves, the ends with the smallest widths of the two non-equal width isolation grooves are respectively close to different sides of the common electrode table; two adjacent common electrode tables on the same side share a second isolation groove.

[0010] In the table-type infrared focal plane array provided by the embodiment of the present invention, second isolation grooves are etched on both adjacent sides of the common electrode table, and when the second isolation grooves are non-equal width isolation grooves, the ends with the smallest widths of the two non-equal width isolation grooves are adjacent, or the ends with the largest widths of the two non-equal width isolation grooves are adjacent.

[0011] The table-type infrared focal plane array provided by the embodiment of the present invention has three second isolation grooves etched around the common electrode table, and in the case where the second isolation grooves are non-equal width isolation grooves, the end with the smallest width of the middle isolation groove is adjacent to the end with the smallest width of a non-equal width isolation groove, and the end with the largest width of the middle isolation groove is adjacent to the end with the largest width of another non-equal width isolation groove, wherein the middle isolation groove is a non-equal width isolation groove located in the middle of the three non-equal width isolation grooves.

[0012] The table-type infrared focal plane array provided by the embodiment of the present invention has a plurality of pixel table tops arranged in a matrix form in a pixel electrode area, and the pixel electrode area is rectangular; a plurality of common electrode table tops are arranged in a matrix form in the common electrode area; the common electrode area is linear, L-shaped, concave, or loop-shaped; wherein the linear shape is a shape area in contact with one side of the rectangular pixel electrode area; the L-shaped shape is a shape area in contact with two adjacent sides of the rectangular pixel electrode area; the concave shape is a shape area in contact with three sides of the rectangular pixel electrode area; and the loop shape is a shape area in contact with four sides of the rectangular pixel electrode area.

[0013] The table-type infrared focal plane array provided by the embodiment of the invention has the following characteristics: when the common electrode area is linear, on one side adjacent to the common electrode area and the pixel electrode area, a first isolation groove or a second isolation groove is etched between adjacent common electrode table tops and the pixel table tops; when the common electrode area is L-shaped, on two sides adjacent to the common electrode area and the pixel electrode area, a first isolation groove or a second isolation groove is etched between adjacent common electrode table tops and the pixel table tops; when the common electrode area is concave, on three sides adjacent to the common electrode area and the pixel electrode area, a first isolation groove or a second isolation groove is etched between adjacent common electrode table tops and the pixel table tops; when the common electrode area is round, the common electrode area surrounds the pixel electrode area, and on four sides adjacent to the common electrode area and the pixel electrode area, a first isolation groove or a second isolation groove is etched between adjacent common electrode table tops and the pixel table tops. On the basis of satisfying the corresponding readout circuit structure, those skilled in the art can design different structures in combination with the specific shapes, quantities and arrangement of the pixel table tops and the common electrode table tops.

[0014] The table-type infrared focal plane array provided by the invention embodiment is a multi-layer material structure, and the multi-layer material structure is separated into a pixel table and a common electrode table by a first isolation groove and a second isolation groove; the multi-layer material structure includes a substrate, and a buffer layer, a bottom electrode contact layer, a barrier layer, an absorption layer and a top electrode contact layer sequentially grown from the substrate to the table to realize the photoelectric characteristics of the photodiode. The bottom of the first isolation groove is etched to the inside of the bottom electrode contact layer, and the bottom of the second isolation groove is etched to the first area, which is any area between the inside of the bottom electrode contact layer and the inside of the substrate. Therefore, technicians only need to accurately control the etching depth of the first isolation groove during the preparation process.

[0015] The invention provides a method for preparing a mesa electrode of an infrared focal plane array, comprising: coating a photoresist on a top electrode contact layer of a superlattice epitaxial wafer; performing photolithography on the photoresist according to a mask plate to form a photoresist mask layer, wherein the mask plate is provided with a pattern of a first isolation groove and a second isolation groove, the width of the first isolation groove is less than a preset width, the width of the second isolation groove is greater than the width of the first isolation groove, and the photoresist mask layer is a photoresist mask layer after the photoresist corresponding to the pattern is removed; etching the superlattice epitaxial wafer having the photoresist mask layer by etching gas. The method comprises etching the mesa structure having a first isolation groove and a second isolation groove, wherein the first isolation groove and the second isolation groove are obtained simultaneously in one etching, the depth of the first isolation groove is greater than a preset depth, the depth of the second isolation groove is greater than the depth of the first isolation groove, each pixel mesa of the mesa structure is separated by the first isolation groove, each common electrode mesa of the mesa structure is separated by the first isolation groove or the second isolation groove, and at least one second isolation groove is etched around each common electrode mesa; metal electrode deposition is performed on the mesa structure to obtain a mesa electrode of the infrared focal plane array.

[0016] The method provided by the embodiment of the invention is to dry-etch a superlattice epitaxial wafer having a photoresist mask layer by means of an etching gas to obtain a mesa structure having a first isolation groove and a second isolation groove, comprising: determining the depth of the first isolation groove; determining the time for dry etching according to the depth of the first isolation groove; and dry-etching the superlattice epitaxial wafer having a photoresist mask layer by means of an etching gas according to the time to obtain a mesa structure having a first isolation groove and a second isolation groove.

[0017] The invention provides a table-type infrared focal plane array and table electrode preparation method, which designs two isolation grooves with different widths and depths that can be obtained by one etching, simplifying the etching process; the width of the first isolation groove is less than the preset width, which can improve the table duty cycle; the depth of the first isolation groove is greater than the preset depth, which can reduce the lateral diffusion current; in the common electrode area, after the conductive metal is deposited, a metal connection is formed between the bottom of the first isolation groove-the bottom of the second isolation groove and the sidewall-the common electrode table, so that the common electrode is led from the bottom of the epitaxial material of the infrared focal plane array to the surface of the common electrode table, improving the conductive stability. This solves the problem that the infrared focal plane array in the related art is difficult to take into account the large table duty cycle, the small lateral diffusion current, and the relatively stable conductivity of the metal electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other embodiments can be obtained based on these drawings without creative work.

[0019] Figure 1 It is a schematic diagram of the table top morphology of the pixel table in the embodiment of the invention.

[0020] Figure 2 It is a schematic diagram of the mesa morphology in which a first isolation groove and a second isolation groove of equal width are provided between common electrode mesas in an embodiment of the invention.

[0021] Figure 3 yes Figure 2 Front view of the common electrode table located in the upper left corner.

[0022] Figure 4 It is a schematic diagram of the mesa morphology in which a first isolation groove and a second isolation groove of unequal width are provided between common electrode mesas in an embodiment of the invention.

[0023] Figure 5 yes Figure 4 Front view of the common electrode table located in the upper left corner.

[0024] Figure 6 It is a schematic diagram of the mesa morphology of the second isolation grooves in which the isolation grooves between the common electrode mesas in the embodiment of the present invention are all of unequal width.

[0025] Figure 7 yes Figure 6 Front view of the common electrode table located in the upper left corner.

[0026] Figure 8It is a schematic diagram of a common electrode area in a linear shape in an embodiment of the present invention.

[0027] Fig. 9 It is a schematic diagram of an L-shaped common electrode area in an embodiment of the invention.

[0028] Fig.10 It is a flow chart of the steps of a method for preparing a mesa electrode of an infrared focal plane array in an embodiment of the invention. DETAILED DESCRIPTION

[0029] The embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as being limited to the embodiments described herein, which are instead provided to provide a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments of the present invention are only for exemplary purposes and are not intended to limit the scope of protection of the present invention.

[0030] As infrared focal plane detectors develop towards ultra-large arrays and ultra-small pixels, it is necessary to separate the table units in the table-type infrared focal plane array through isolation grooves, and minimize the width of the isolation grooves to increase the table duty cycle in order to obtain better detector response performance. However, as the depth-to-width ratio of the isolation grooves increases, the difficulty of preparing the metal electrodes on the side walls of the isolation grooves increases, and the prepared metal electrodes have problems such as difficulty in climbing and easy breakage of the conductive paths, resulting in poor electrical connections, which in turn reduces the performance of the detector.

[0031] See also Figures 1 to 9 As shown, an embodiment of the present invention provides a table-type infrared focal plane array to solve the above problems. The infrared focal plane array includes a pixel electrode area and a common electrode area. The pixel electrode area includes a plurality of pixel table tops, and the common electrode area includes a plurality of common electrode table tops.

[0032] Each pixel table is separated by a first isolation groove, wherein a conductive metal is deposited on the surface of the pixel table as a pixel electrode of the infrared focal plane array, and the first isolation groove is an isolation groove with a width less than a preset width and a depth greater than a preset depth.

[0033] Each common electrode mesa is separated by a first isolation groove or a second isolation groove, and at least one second isolation groove is etched around each common electrode mesa, wherein the second isolation groove is an isolation groove with a width greater than the width of the first isolation groove and a depth greater than the depth of the first isolation groove, and the first isolation groove and the second isolation groove are obtained synchronously by one etching.

[0034] In the common electrode area, conductive metal is deposited on the bottom of the first isolation groove, the bottom and sidewalls of the second isolation groove, and the surface of the common electrode table, which is used to lead the common electrode of the above-mentioned infrared focal plane array from the bottom of the epitaxial material of the above-mentioned infrared focal plane array to the surface of the common electrode table.

[0035] In the infrared focal plane array, both the pixel table and the common electrode table can have a variety of shapes, such as quadrilateral, rhombus, peak nest or circle. In order to make full use of the space of the infrared focal plane array and meet the practical requirements of simple manufacturing process and easy large-scale integration, the present invention creates an embodiment with the shape of the pixel table and the common electrode table as quadrilateral as the preferred embodiment for description.

[0036] In the above preferred case, depending on the different positions, no matter it is a pixel table or a common electrode table, there will be one, two, three or four isolation grooves around it. In the case where each table is arranged in a matrix form on the infrared focal plane array, there will be two, three or four isolation grooves around each table.

[0037] Affected by the arrangement and shape of the mesas, the shape of the connecting portion between the first isolation trench and the second isolation trench, or the connecting portion between the second isolation trench and the second isolation trench may be in various shapes, for example, rectangular, trapezoidal or irregular polygonal in a top view.

[0038] In the case where the width of the connection portion is greater than that of the first isolation trench and less than or equal to that of the second isolation trench, the connection portion may be understood as a portion of the adjacent second isolation trench.

[0039] In the case where the width of the connection portion is equal to that of the first isolation trench, the connection portion may be understood as a portion of an adjacent first isolation trench or a separate first isolation trench.

[0040] The isolation groove between the pixel table and the common electrode table can be a first isolation groove or a second isolation groove, and these two situations can exist simultaneously in an infrared focal plane array. The isolation groove between common electrode tables is similar, but at least one second isolation groove needs to be etched around each common electrode table.

[0041] Etching includes dry etching and wet etching. The equipment cost of wet etching is low and the etching rate is high, but the etching accuracy is low and there are problems of photoresist swelling and drift. The equipment cost of dry etching is relatively high, but the etching accuracy is high. The present invention creates an embodiment with the first isolation groove and the second isolation groove obtained by dry etching as the preferred embodiment for description.

[0042] The width of the first isolation groove is smaller than the preset width, and the depth of the first isolation groove is greater than the preset depth. Those skilled in the art can determine the specific values ​​of the preset width and the preset depth based on a priori values ​​and actual conditions.

[0043] To improve the duty cycle of the infrared focal plane array, the width of the first isolation groove should be small, for example, 0.5-1 μm. To reduce the lateral diffusion current, the depth of the first isolation groove should be large, for example, the bottom of the first isolation groove is etched to the inside of the bottom electrode contact layer of the infrared focal plane array.

[0044] It is understandable that the width of the second isolation groove is greater than that of the first isolation groove, but it will be limited by the area of ​​the infrared focal plane array. At the same time, if the width of the second isolation groove is too large, the common electrode table area will be reduced. Therefore, those skilled in the art need to determine the reasonable width of the second isolation groove according to the prior value and the actual situation, for example, 1-5μm. In addition, the second isolation groove can be an equal-width isolation groove or a non-equal-width isolation groove, which will be described in detail in the subsequent description.

[0045] It can be understood that the first isolation groove in the pixel electrode area is used to separate the pixel mesas. The first isolation groove and the second isolation groove in the common electrode area are used to separate the common electrode mesas and deposit metal electrodes to achieve electrical connection between the infrared focal plane array and the readout circuit.

[0046] In the common electrode area, the width of the first isolation groove is relatively small, resulting in a large depth-to-width ratio, and it is difficult for the metal electrode to be deposited on the side wall near the bottom of the first isolation groove, resulting in difficulty for the metal electrode to climb along the path of the bottom of the first isolation groove-the side wall of the first isolation groove-the common electrode table. The width of the second isolation groove is greater than that of the first isolation groove, and the depth-to-width ratio is relatively small, so that the metal electrode deposited at the bottom of the first isolation groove can be electrically connected along the path of the bottom of the first isolation groove-the bottom of the second isolation groove-the side wall of the second isolation groove-the common electrode table, thereby improving the conductive stability.

[0047] In addition, in the specific structure of the above-mentioned infrared focal plane array, the depth and width of the second isolation groove are both greater than those of the first isolation groove, but in the preparation process, it is only necessary to consider that the width of the second isolation groove is greater than that of the first isolation groove. The reason is: the width of the second isolation groove is greater than that of the first isolation groove, so the etching area of ​​the second isolation groove is greater than that of the first isolation groove, so that the etching rate of the second isolation groove is greater than that of the first isolation groove. Therefore, under the same etching time, the etching depth of the second isolation groove will be greater than that of the first isolation groove.

[0048] Based on the above reasons, the first isolation trench and the second isolation trench provided by the embodiment of the present invention can be formed simultaneously in one etching, and the aspect ratio of the second isolation trench is smaller than that of the first isolation trench.

[0049] In order to obtain two isolation grooves of different depths, the related technology requires two or even multiple etchings, and each etching after the first etching will greatly increase the difficulty of preparation. Compared with multiple etchings, setting patterns with different line widths on the mask to correspond to the first isolation groove and the second isolation groove has little impact on the preparation process. Therefore, the above-mentioned infrared focal plane array provided by the invention embodiment has significant advantages in the preparation process.

[0050] It is understandable that the bottom of the epitaxial material of the above-mentioned infrared focal plane array refers to the bottom electrode contact layer, or the buffer layer located at the bottom of the bottom electrode contact layer, or the substrate located at the bottom of the buffer layer, which will be described in detail later.

[0051] In summary, the above-mentioned infrared focal plane array provided by the embodiment of the present invention is designed to have two isolation grooves with different widths and depths that can be obtained by one etching, thereby simplifying the etching process; the width of the first isolation groove is smaller than the preset width, and a smaller value can be taken in combination with actual conditions to increase the table duty cycle and enhance the response performance; the depth of the first isolation groove is greater than the preset depth, and a larger value can be taken in combination with actual conditions to reduce the lateral diffusion current; the width of the second isolation groove is greater than the first isolation groove, which can provide a larger bottom electrode contact area and reduce the difficulty of preparing the common electrode; a conductive metal is deposited between the bottom of the first isolation groove in the common electrode area - the bottom of the second isolation groove and the sidewall - the common electrode table to form a metal connection, which can lead the common electrode from the bottom of the epitaxial material of the infrared focal plane array to the surface of the common electrode table, thereby improving the conductive stability.

[0052] Exemplarily, in order to simplify the process, the first isolation trench is an isolation trench of equal width, such as Figure 1 The first isolation grooves between the 9 pixel mesas shown are all isolation grooves of equal width.

[0053] Exemplarily, the second isolation trench is an isolation trench of equal width having a width greater than that of the first isolation trench, such as Figure 2 There are first isolation grooves and second isolation grooves between the nine common electrode mesas, and the second isolation grooves are all isolation grooves with equal widths greater than the first isolation grooves. Figure 2 Take the common electrode table located in the upper left corner as an example, the main view is as follows Figure 3 As shown, the width d2 of the second isolation groove is greater than the width d1 of the first isolation groove, and the depth h2 of the second isolation groove is greater than the depth h1 of the first isolation groove. Figure 3The dark shadow in the figure indicates that the metal electrode is deposited on the corresponding part. It can be seen that due to the large depth-to-width ratio of the first isolation groove, it is difficult for the metal electrode to be deposited on the bottom sidewall of the first isolation groove, while the width d2 of the second isolation groove is greater than the width d1 of the first isolation groove, and the depth-to-width ratio is relatively large, so the metal electrode can also cover the bottom sidewall of the second isolation groove well, thereby ensuring a stable conductive path between the bottom electrode contact layer and the top electrode contact layer of the common electrode mesa.

[0054] Preferably, the second isolation trench is a non-uniform width isolation trench whose minimum width is greater than the width of the first isolation trench, the width of the non-uniform width isolation trench gradually increases in the length direction of the isolation trench, and the depth of the non-uniform width isolation trench increases as the width increases.

[0055] It can be understood that the length of the second isolation groove can be less than, equal to, or greater than the length of adjacent sides of adjacent common electrode mesas.

[0056] For example, Figure 4 There are first isolation grooves and second isolation grooves between the nine common electrode mesas shown, and the second isolation grooves are the above-mentioned isolation grooves of non-uniform width. Figure 4 Take the common electrode table located in the upper left corner as an example, the main view is as follows Figure 5 As shown, the width of the second isolation groove gradually increases from d3 to d2 in the length direction of the isolation groove, the depth increases with the increase of the width, and the bottom of the second isolation groove is sloped. Figure 5 The dark shadows in the figure indicate that metal electrodes are deposited on the corresponding parts. Figure 5 The width of the connecting portion between the first isolation trench and the second isolation trench is between d3 and d2, and the depth is between h1 and h2. Wherein, d3 is the minimum width of the second isolation trench, and d1<d3<d2.

[0057] It can be understood that the depth of the non-uniform width isolation groove is greater than h1 and less than or equal to h2, and the difference in depth corresponds to the difference in width. Figure 5 As shown, it is difficult to deposit a metal electrode in the area corresponding to the width close to d3 in the bottom sidewall of the second isolation trench, which is the same reason as the difficulty in depositing a metal electrode in the bottom sidewall of the first isolation trench. At the same time, since other areas in the bottom sidewall of the second isolation trench are easy to deposit metal electrodes, the conductive path is still sufficiently stable.

[0058] Compared to Figure 2 and Figure 3 The second isolation groove shown is a case of equal-width isolation grooves. The above-mentioned non-equal-width isolation grooves can allow the common electrode mesa to have a larger area, and the metal electrode conduction is also more stable.

[0059] For example, Figure 6 The second isolation grooves between the 9 common electrode mesas shown are all the above-mentioned non-uniform width isolation grooves. Figure 6 Take the common electrode table located in the upper left corner as an example, the main view is as follows Figure 7 As shown, the minimum width portions of the two second isolation trenches are connected.

[0060] It is understandable that compared to Figure 4 and Figure 5 The situation shown, Figure 6 and Figure 7 The common electrode mesa shown enhances the stability of the conductive metal electrode and is beneficial to the preparation of the common electrode mesa electrode.

[0061] It is understandable that the two situations that the second isolation grooves are equal-width isolation grooves and the second isolation grooves are non-equal-width isolation grooves can exist simultaneously on an infrared focal plane array. Two, three or four second isolation grooves located around the same common electrode table can also include the above two situations at the same time. Those skilled in the art can design second isolation grooves of different shapes based on the specific shape, number and arrangement of the common electrode table.

[0062] Preferably, second isolation grooves are etched on opposite sides of the common electrode mesa, and when the second isolation grooves are unequal width isolation grooves, the ends with the smallest widths of the two unequal width isolation grooves are respectively close to different sides of the common electrode mesa, and two adjacent common electrode mesas on the same side share one second isolation groove. Figure 4 As shown, the conductive stability of the metal electrode can be enhanced while allowing the common electrode table to have a larger area.

[0063] Preferably, the second isolation grooves are etched on both adjacent sides of the common electrode mesa, and when the second isolation grooves are non-uniform width isolation grooves, the ends of the two non-uniform width isolation grooves with the smallest widths are adjacent, or the ends of the two non-uniform width isolation grooves with the largest widths are adjacent, such as Figure 6 The common electrode mesas at the four corners are shown in FIG. This can enhance the conductive stability of the metal electrode while allowing the common electrode mesas to have a larger area.

[0064] Preferably, three second isolation grooves are etched around the common electrode mesa, and when the second isolation grooves are non-uniform width isolation grooves, the end of the middle isolation groove with the smallest width is adjacent to the end of one non-uniform width isolation groove with the smallest width, and the end of the middle isolation groove with the largest width is adjacent to the end of another non-uniform width isolation groove with the largest width, wherein the middle isolation groove is a non-uniform width isolation groove located in the middle of the three non-uniform width isolation grooves, such as Figure 6 As shown in the figure, four common electrode mesas adjacent to the common electrode mesas in the middle, where adjacent means that the four common electrode mesas are adjacent to the common electrode mesas in the middle edge to edge. This can enhance the conductive stability of the metal electrode while allowing the common electrode mesas to have a larger area.

[0065] It is understandable that if Figure 6 As shown in the figure, four second isolation grooves are etched around the common electrode mesa, and when the second isolation grooves are non-uniform width isolation grooves, every two adjacent non-uniform width isolation grooves are adjacent at the end with the smallest width, or at the end with the largest width. This can enhance the conductive stability of the metal electrode while allowing the common electrode mesa to have a larger area.

[0066] Preferably, a plurality of pixel mesas are arranged in a matrix form in a pixel electrode region, and the pixel electrode region is rectangular; a plurality of common electrode mesas are arranged in a matrix form in a common electrode region, and the common electrode region is linear, L-shaped, concave, or loop-shaped.

[0067] Among them, the linear type is a shape area that contacts one side of the rectangular pixel electrode area; the L-type is a shape area that contacts two adjacent sides of the rectangular pixel electrode area; the concave type is a shape area that contacts three sides of the rectangular pixel electrode area; and the U-type is a shape area that contacts four sides of the rectangular pixel electrode area.

[0068] It is understandable that the shapes and layouts of the pixel electrode regions and the common electrode regions can be adjusted by those skilled in the art according to actual needs.

[0069] Specifically, when the common electrode region is linear, a first isolation groove or a second isolation groove is etched between adjacent common electrode mesas and pixel mesas on an edge adjacent to the common electrode region and the pixel electrode region. Figure 8 The figure shows a situation where a plurality of first isolation grooves are etched between adjacent common electrode mesas and pixel mesas, the pixel electrode region has 5×3 pixel mesas, and the common electrode region has 4×1 common electrode mesas.

[0070] Specifically, when the common electrode region is L-shaped, a first isolation groove or a second isolation groove is etched between adjacent common electrode mesas and pixel mesas on two adjacent sides of the common electrode region and the pixel electrode region. Fig. 9 The figure shows a situation where a plurality of first isolation grooves and second isolation grooves are etched between adjacent common electrode mesas and pixel mesas, the pixel electrode region has 3×3 pixel mesas, and the common electrode region has 1×3+4×2 common electrode mesas.

[0071] It is understandable that, in actual situations, the number of pixel mesas arranged in the pixel electrode region and the number of common electrode mesas arranged in the common electrode region are far more than the above example, and can reach 10. 6 The above examples are only provided to make the distribution of the isolation grooves clearly visible in the drawings.

[0072] Specifically, when the common electrode region is concave, on three adjacent sides of the common electrode region and the pixel electrode region, first isolation grooves or second isolation grooves are etched between adjacent common electrode mesas and pixel mesas.

[0073] Specifically, when the common electrode region is in a loop shape, the common electrode region surrounds the pixel electrode region, and the first isolation groove or the second isolation groove is etched between adjacent common electrode mesas and pixel mesas on four adjacent sides of the common electrode region and the pixel electrode region.

[0074] Preferably, the infrared focal plane array is a multi-layer material structure, and the multi-layer material structure is separated into a pixel table and a common electrode table by a first isolation groove and a second isolation groove; the multi-layer material structure includes a substrate, and a buffer layer, a bottom electrode contact layer, a barrier layer, an absorption layer and a top electrode contact layer grown in sequence from the substrate to the table. The bottom of the first isolation groove is etched to the inside of the bottom electrode contact layer, and the bottom of the second isolation groove is etched to the first region, and the first region is any region between the inside of the bottom electrode contact layer and the inside of the substrate.

[0075] The above-mentioned multilayer material structure has good stability and compatibility while realizing the photoelectric characteristics of the photodiode. Among them, the buffer layer is grown on the substrate, which can further alleviate the lattice mismatch and stress between the substrate and the subsequent growth layer, and improve the crystal quality of the material.

[0076] Since the depth of the second isolation trench is greater than that of the first isolation trench, when the bottom of the second isolation trench is etched to the inside of the bottom electrode contact layer, it can be understood that the bottom of the first isolation trench is etched to the upper half of the bottom electrode contact layer, and the bottom of the second isolation trench is etched to the lower half of the bottom electrode contact layer.

[0077] In the infrared focal plane array provided by the embodiment of the present invention, the bottom of the second isolation groove can break through the bottom electrode contact layer and reach the buffer layer or even the substrate. Therefore, during the preparation process, technicians only need to accurately control the etching depth of the first isolation groove, thereby reducing the difficulty of preparation and facilitating large-scale production.

[0078] Specifically, in the pixel electrode region, the surface of the pixel table is deposited with conductive metal; in the common electrode region, the bottom of the first isolation groove, the bottom and sidewall of the second isolation groove, and the surface of the common electrode table are all deposited with conductive metal, which can ensure the stability of the circuit connection between the infrared focal plane array and the readout circuit. The conductive metal includes but is not limited to titanium, platinum, and gold.

[0079] It can be understood that the surface of the pixel mesa and the surface of the common electrode mesa refer to the upper surface of the mesa, which is the side of the mesa away from the isolation groove.

[0080] See also Fig.10As shown, the present invention also provides a method for preparing a mesa electrode of an infrared focal plane array, comprising: step S101, coating a photoresist on a top electrode contact layer of a superlattice epitaxial wafer.

[0081] Step S102, performing photolithography on the photoresist according to the mask plate to form a photoresist mask layer, wherein the mask plate is provided with a pattern of a first isolation groove and a second isolation groove, the width of the first isolation groove is less than a preset width, the width of the second isolation groove is greater than the width of the first isolation groove, and the photoresist mask layer is a photoresist mask layer after the photoresist corresponding to the pattern is removed.

[0082] Step S103, dry-etching the superlattice epitaxial wafer having a photoresist mask layer by etching gas to obtain a mesa structure having a first isolation groove and a second isolation groove, wherein the first isolation groove and the second isolation groove are obtained simultaneously in one etching, the depth of the first isolation groove is greater than a preset depth, the depth of the second isolation groove is greater than the depth of the first isolation groove, each pixel mesa of the mesa structure is separated by the first isolation groove, each common electrode mesa of the mesa structure is separated by the first isolation groove or the second isolation groove, and at least one second isolation groove is etched around each common electrode mesa.

[0083] Step S104 , performing metal electrode deposition on the mesa structure to obtain a mesa electrode of the infrared focal plane array.

[0084] It is understood that superlattice epitaxial wafers are the basic materials of infrared focal plane arrays. They are semiconductor thin films with superlattice structures grown on substrates using epitaxial growth technology. Superlattice structures refer to artificial periodic structures formed by alternating growth of two or more different semiconductor materials with nanometer-level thickness.

[0085] The above-mentioned preparation method provided by the embodiment of the invention can obtain two isolation grooves with different widths and depths through one etching, which simplifies the etching process; the width of the first isolation groove is smaller than the preset width, and a smaller value can be taken according to the actual situation to increase the table duty cycle and enhance the response performance. At the same time, the depth of the first isolation groove is greater than the preset depth, that is, a deep etching process is adopted, which reduces the influence of the lateral diffusion current between the pixel table tops; the width of the second isolation groove is greater than the first isolation groove, which provides a larger bottom electrode contact area, thereby improving the stability of the detector and reducing energy loss; the metal electrode deposited at the bottom of the first isolation groove in the common electrode area can be electrically connected along the path of the bottom of the first isolation groove-the bottom of the second isolation groove-the side wall of the second isolation groove-the common electrode table top, thereby improving the conductive stability.

[0086] Preferably, before step S101, the superlattice epitaxial wafer having a multi-layer material structure is wet cleaned to effectively remove impurities.

[0087] Specifically, the multilayer material structure includes a substrate, and a buffer layer, a bottom electrode contact layer, a barrier layer, an absorption layer and a top electrode contact layer that are sequentially grown from the substrate to the table surface.

[0088] Preferably, in step S101, applying photoresist on the top electrode contact layer of the superlattice epitaxial wafer includes: using a coating baking machine to spin-coat the photoresist on the surface of the superlattice epitaxial wafer, the coating speed is 3000 rpm, and the thickness of the coating is 2 μm. The coated photoresist is subjected to a soft baking curing treatment, and the soft baking curing temperature is 120° C. and the time is 100 s.

[0089] Exemplarily, the photoresist is AZ-5214E, TI 35 ESX or AZ NL of 2000.

[0090] Preferably, in step S102, the photoresist is subjected to photolithography processing according to the mask to form a photoresist mask layer, including using a photolithography mask to cover a preset mesa portion for exposure, the exposure time is 7 seconds, and the exposure is developed in a developer for 90 seconds. Subsequently, the photoresist mask layer with a thickness of 2 μm is prepared by baking at a preparation temperature of 120°C for 100 seconds. Among them, the first isolation groove is an equal-width isolation groove with a width of 1 μm, and the second isolation groove is an equal-width isolation groove with a width of 2 μm, or a non-equal-width isolation groove with a width gradually changing from 1 μm to 2 μm.

[0091] Preferably, in step S103, the superlattice epitaxial wafer having a photoresist mask layer is dry-etched by etching gas to obtain a mesa structure having a first isolation groove and a second isolation groove, including: step S1031, determining the depth of the first isolation groove.

[0092] It is understandable that the bottom of the first isolation groove in the common electrode region can contact the bottom electrode contact layer of the superlattice epitaxial wafer so that the metal electrode deposited later can cover the bottom electrode contact layer. The depth of the first isolation groove can be determined by the thickness difference between the top electrode contact layer and the bottom electrode contact layer, and the thickness of the bottom electrode contact layer, the top electrode contact layer and the functional layer therebetween can be determined during the material growth process. Therefore, those skilled in the art can determine the depth of the first isolation groove relatively easily and accurately.

[0093] Step S1032, determining the dry etching time according to the depth of the first isolation trench.

[0094] Step S1033, dry etching the superlattice epitaxial wafer having the photoresist mask layer by using etching gas according to the above time to obtain a mesa structure having a first isolation groove and a second isolation groove.

[0095] Exemplarily, the etching gas is Cl 2 / BCl3 or CH 4 / H 2 .

[0096] Preferably, in step S104, metal electrode deposition is performed on the mesa structure to obtain a mesa electrode of an infrared focal plane array, including: step S1041, performing deposition pretreatment on the mesa structure to obtain a product to be deposited, specifically: removing the photoresist on the mesa structure to obtain a first process product; passivating the first process product to obtain a second process product having a passivation film; and opening a hole in the passivation film of the second process product to obtain a product to be deposited, wherein the area of ​​the passivation film exposed by the opening corresponds to the area where the metal electrode needs to be deposited.

[0097] Step S1042, performing metal electrode deposition on the product to be deposited to obtain a table electrode of the infrared focal plane array, specifically: by thermal evaporation or magnetron sputtering, conductive metals titanium, platinum, and gold are deposited in sequence on the bottom of the first isolation groove in the common electrode area, the bottom and side walls of the second isolation groove, the common electrode table, and the pixel table in the pixel electrode area to obtain the table electrode of the infrared focal plane array.

[0098] Exemplarily, the metal electrode is formed by photolithography, deposition, and lift-off processes.

[0099] The specific method for forming the metal electrode is: firstly, a layer of photoresist is coated on the surface of the passivation film, then the desired metal electrode pattern is formed on the photoresist by development, then the metal electrode layer is deposited on the pattern formed by the photoresist, and finally the unnecessary metal electrode layer and the photoresist are stripped off to form the desired metal electrode. The metal electrode layer can be formed by deposition processes such as chemical vapor deposition, physical vapor deposition, plasma enhanced chemical vapor deposition or atomic layer deposition, and the material can be titanium, platinum, gold, tin, chromium, aluminum, etc.

[0100] The invention also provides an infrared detector, which includes the above-mentioned mesa-type infrared focal plane array and a readout circuit with a substrate, wherein the above-mentioned mesa-type infrared focal plane array and the above-mentioned readout circuit are electrically connected through the mesa electrode prepared according to the above-mentioned method. The above-mentioned mesa electrode can be led out from the side wall of the common electrode mesa to the surface of the common electrode mesa, which can effectively improve the electrode contact of the infrared detector.

[0101] It should be noted that the term "including" and its variations used in the embodiments of the present invention are open inclusions, that is, "including but not limited to". The term "based on" means "based at least in part on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one other embodiment"; the term "some embodiments" means "at least some embodiments". The modifications of "one" and "multiple" mentioned in the embodiments of the present invention are illustrative and not restrictive. Those skilled in the art should understand that unless otherwise clearly indicated in the context, they should be understood as "one or more". The descriptions of the terms "first", "second", etc. are for descriptive purposes only and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated.

[0102] The user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in the embodiments of the present invention are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with the relevant laws, regulations and standards of relevant countries and regions, and provide corresponding operation entrances for users to choose to authorize or refuse.

[0103] The various steps described in the method implementation methods provided by the embodiments of the present invention can be performed in different orders and / or in parallel. In addition, the method implementation methods may include additional steps and / or omit the steps shown. The scope of protection of the present invention is not limited in this respect.

[0104] The term "embodiment" in this specification refers to specific features, structures or characteristics described in conjunction with the embodiment that can be included in at least one embodiment of the invention. The appearance of this phrase in various places in the specification does not necessarily mean the same embodiment, nor does it mean that it is mutually exclusive with other embodiments and is independent or optional. The various embodiments in this specification are described in a related manner, and the same and similar parts between the various embodiments refer to each other. In particular, for the device, equipment, and system embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts refer to the partial description of the method embodiment.

[0105] The above-described embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of protection. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the attached claims.

Claims

1. A table-type infrared focal plane array, characterized in that: It includes a pixel electrode area and a common electrode area, wherein the pixel electrode area includes a plurality of pixel mesas, and the common electrode area includes a plurality of common electrode mesas; Each of the pixel mesas is separated by a first isolation groove, wherein a conductive metal is deposited on the surface of the pixel mesas as a pixel electrode of the infrared focal plane array, and the first isolation groove is an isolation groove with a width less than a preset width and a depth greater than a preset depth; Each of the common electrode mesas is separated by the first isolation groove or the second isolation groove, and at least one second isolation groove is etched around each of the common electrode mesas, wherein the second isolation groove is an isolation groove having a width greater than that of the first isolation groove and a depth greater than that of the first isolation groove, and the first isolation groove and the second isolation groove are obtained synchronously by one etching; In the common electrode area, conductive metal is deposited on the bottom of the first isolation groove, the bottom and sidewalls of the second isolation groove, and the surface of the common electrode table, so as to lead the common electrode of the infrared focal plane array from the bottom of the epitaxial material of the infrared focal plane array to the surface of the common electrode table.

2. The table-type infrared focal plane array according to claim 1, characterized in that: The first isolation groove is an isolation groove of equal width; The second isolation trench is an equal-width isolation trench whose width is greater than that of the first isolation trench, or an unequal-width isolation trench whose minimum width is greater than that of the first isolation trench; The width of the non-uniform width isolation groove gradually increases in the length direction of the isolation groove, and the depth of the non-uniform width isolation groove increases as the width increases.

3. The table-type infrared focal plane array according to claim 1, characterized in that: The second isolation grooves are etched on opposite sides of the common electrode mesa, and when the second isolation grooves are isolation grooves of non-uniform width, the ends of the two isolation grooves of non-uniform width with the smallest width are respectively close to different other sides of the common electrode mesa; Two adjacent common electrode mesas on the same side share one second isolation groove.

4. The table-type infrared focal plane array according to claim 1, characterized in that: The second isolation grooves are etched on both adjacent sides of the common electrode mesa, and when the second isolation grooves are unequal width isolation grooves, the ends with the smallest widths of the two unequal width isolation grooves are adjacent, or the ends with the largest widths of the two unequal width isolation grooves are adjacent.

5. The table-type infrared focal plane array according to claim 1, characterized in that: Three second isolation grooves are etched around the common electrode table, and in the case where the second isolation grooves are non-equal width isolation grooves, the end with the smallest width of the middle isolation groove is adjacent to the end with the smallest width of one of the non-equal width isolation grooves, and the end with the largest width of the middle isolation groove is adjacent to the end with the largest width of another non-equal width isolation groove, wherein the middle isolation groove is a non-equal width isolation groove located in the middle of the three non-equal width isolation grooves.

6. The table-type infrared focal plane array according to claim 1, characterized in that: The plurality of pixel tables are arranged in a matrix form in the pixel electrode area, and the pixel electrode area is rectangular; The plurality of common electrode mesas are arranged in a matrix form in the common electrode area; The common electrode area is linear, L-shaped, concave, or loop-shaped; wherein the linear shape is a shape area that contacts one side of a rectangular pixel electrode area; the L-shape is a shape area that contacts two adjacent sides of a rectangular pixel electrode area; the concave shape is a shape area that contacts three sides of a rectangular pixel electrode area; and the loop shape is a shape area that contacts four sides of a rectangular pixel electrode area.

7. The table-type infrared focal plane array according to claim 6, characterized in that: In the case where the common electrode region is linear, on an edge of the common electrode region adjacent to the pixel electrode region, the first isolation groove or the second isolation groove is etched between the adjacent common electrode mesas and the pixel mesas; In the case where the common electrode region is L-shaped, the first isolation groove or the second isolation groove is etched between the adjacent common electrode mesas and the pixel mesas on two adjacent sides of the common electrode region and the pixel electrode region; In the case where the common electrode region is concave, the first isolation groove or the second isolation groove is etched between the adjacent common electrode mesas and the pixel mesas on three adjacent sides of the common electrode region and the pixel electrode region; When the common electrode region is in a circular shape, the common electrode region surrounds the pixel electrode region, and the first isolation groove or the second isolation groove is etched between adjacent common electrode mesas and pixel mesas on four adjacent sides of the common electrode region and the pixel electrode region.

8. The table-type infrared focal plane array according to claim 1, characterized in that: The infrared focal plane array is a multi-layer material structure, and the multi-layer material structure is separated into the pixel table and the common electrode table by the first isolation groove and the second isolation groove; The multilayer material structure includes a substrate, and a buffer layer, a bottom electrode contact layer, a barrier layer, an absorption layer and a top electrode contact layer sequentially grown from the substrate to the table surface; The bottom of the first isolation trench is etched to the inside of the bottom electrode contact layer, and the bottom of the second isolation trench is etched to the first region, which is any region between the inside of the bottom electrode contact layer and the inside of the substrate.

9. A method for preparing a mesa electrode of an infrared focal plane array, characterized in that: include: coating a photoresist on a top electrode contact layer of the superlattice epitaxial wafer; Performing photolithography on the photoresist according to a mask plate to form a photoresist mask layer, wherein the mask plate is provided with patterns of a first isolation groove and a second isolation groove, the width of the first isolation groove is smaller than a preset width, the width of the second isolation groove is larger than the width of the first isolation groove, and the photoresist mask layer is a photoresist mask layer after the photoresist corresponding to the pattern is removed; The superlattice epitaxial wafer having the photoresist mask layer is dry-etched by etching gas to obtain a mesa structure having the first isolation groove and the second isolation groove, wherein the first isolation groove and the second isolation groove are obtained simultaneously in one etching, the depth of the first isolation groove is greater than a preset depth, the depth of the second isolation groove is greater than the depth of the first isolation groove, each pixel mesa of the mesa structure is separated by the first isolation groove, each common electrode mesa of the mesa structure is separated by the first isolation groove or the second isolation groove, and at least one second isolation groove is etched around each common electrode mesa; metal electrode deposition is performed on the mesa structure to obtain a mesa electrode of an infrared focal plane array.

10. The method according to claim 9, characterized in that The superlattice epitaxial wafer having the photoresist mask layer is dry-etched by etching gas to obtain a mesa structure having the first isolation groove and the second isolation groove, comprising: determining a depth of the first isolation trench; Determining the time for performing dry etching according to the depth of the first isolation groove; The superlattice epitaxial wafer having the photoresist mask layer is dry-etched by the etching gas according to the time to obtain a mesa structure having the first isolation groove and the second isolation groove.

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