A novel multi-layer infrared detector and its preparation method

Abstract

The present invention belongs to the technical field of semiconductors, and discloses a novel multi-layer infrared detector, including a pixel set arranged in a multi-layer array on a substrate with a readout circuit, each pixel including a micro-bridge resonant cavity structure including a micro-bridge deck, a beam structure, a support and an electrical connection hole, and the corresponding high-level pixels and low-level pixels in the pixel sets of two adjacent layers are arranged staggered with each other, and the projection surface of the micro-bridge deck in the high-level pixel overlaps with the projection surface of the beam structure, the support and the electrical connection hole in the low-level pixel, and the gap between adjacent pixels. The multi-layer infrared detector of the present invention uses the staggered arrangement to make the micro-bridge deck in the high-level pixel cover the beam structure, the support and the electrical connection hole of the micro-bridge in the low-level pixel, and the gap between adjacent pixels, thereby increasing the absorption area of ​​infrared rays, improving the infrared absorption efficiency, and improving the product performance under the premise of controllable costs.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductors, and in particular to a novel multi-layer infrared detector and a preparation method thereof. Background Art

[0002] The core structure of the uncooled infrared detector product is the microbridge resonant cavity structure. The traditional infrared detector microbridge resonant cavity structure is a single-layer structure. Due to the microbridge projection area occupied by its support and electrical connection holes, beams, gaps between adjacent pixels and other structures, its absorption efficiency of incident infrared rays is relatively low. Some people have proposed using a multi-layer structure to improve the infrared absorption rate, but when a multi-layer structure is manufactured using a traditional stacking scheme, it can only improve the reabsorption of infrared rays transmitted from high-level microbridges, and does not utilize the area occupied by structures such as support and electrical connection holes, beams, and gaps between adjacent pixels, which is not conducive to expanding the absorption area. Summary of the invention

[0003] The purpose of the present invention is to overcome the defects in the prior art that when manufacturing a multi-layer structure with a stacking scheme, it can only improve the re-absorption of infrared rays transmitted from high-level micro-bridges, but does not utilize the area occupied by structures such as supporting and electrical connection holes, beams, and gaps between adjacent pixels, which is not conducive to the expansion of the absorption area. A new type of multi-layer infrared detector and preparation method are provided.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A novel multi-layer infrared detector comprises a set of pixels arranged in a multi-layer array on a substrate with a reading circuit, each pixel comprising a microbridge resonant cavity structure including a microbridge deck, a beam structure, a support and electrical connection holes, the corresponding high-layer pixels and low-layer pixels in the pixel sets of two adjacent layers are staggered, and the projection surface of the microbridge deck in the high-layer pixels overlaps with the projection surface of the beam structure, the support and the electrical connection holes in the low-layer pixels, and the gaps between adjacent pixels.

[0006] Furthermore, the projection surface of each of the low-layer pixels partially overlaps with the projection surfaces of four high-layer pixels in two adjacent rows or columns of the upper layer corresponding to the position of the low-layer pixel.

[0007] Furthermore, the center point of the projection surface of each of the low-layer pixels and the center point of the overall image composed of the projection surfaces of four high-layer pixels in two adjacent rows or columns of the upper layer corresponding to the position of the low-layer pixel are located on the same straight line.

[0008] Furthermore, two layers of array-arranged pixel sets are provided on the substrate with the readout circuit, the first layer is provided with 2*2 pixels, respectively marked as A1, A2, A3, A4, and the second layer is provided with 3*3 pixels, respectively marked as B1, B2...B9. Then, the array corresponding to the first layer of pixel sets is expanded to form a 4*4 array, namely (A1+B1) / 4, (A1+B2) / 4, (A2+B2) / 4, (A2+B3) / 4; (A1+B4) / 4, (A1+B5) / 4, (A2+B5) / 4, (A2+B6) / 4; (A3+B4) / 4, (A3+B5) / 4, (A4+B5) / 4, (A4+B6) / 4; (A3+B7) / 4, (A3+B8) / 4, (A4+B8) / 4, (A4+B9) / 4, where (A1+B1) / 4 represents one quarter of the projection surface of pixel A1 that overlaps with pixel B1, and so on, up to (A4+B9) / 4.

[0009] Furthermore, the high-level pixel set in the pixel sets of the two adjacent layers completely covers the low-level pixel set, and the high-level pixel set is divided into a peripheral non-overlapping area and a central overlapping area. The high-level pixels in the peripheral non-overlapping area are connected to the substrate through support and electrical connection holes, and the high-level pixels in the central overlapping area are connected to the electrode layer of the corresponding low-level pixels through support and electrical connection holes to achieve electrical connection with the substrate.

[0010] Furthermore, the pixels in each layer of the pixel set are respectively provided with a sensitive layer, an electrode layer, a release protection layer and an absorption layer from bottom to top, and the electrode layer is located above the sensitive layer, covers the surface of each pixel, and has a pattern; at the same time, for the high-level pixels in the central overlapping area, the sensitive layer resistor defined by the electrode pattern is respectively connected to the electrode layers of two adjacent low-level pixels through two supports and electrical connection holes,

[0011] For high-level pixels in the peripheral non-overlapping area, one support and electrical connection hole has a depth greater than the other. The sensitive layer resistor defined by the electrode pattern is electrically connected to the substrate through the support and electrical connection hole with a larger depth, and is connected to the electrode layer of the adjacent low-level pixels through the support and electrical connection hole with a smaller depth.

[0012] Furthermore, two low-layer pixels respectively connected to two supports and electrical connection holes of the high-layer pixel located in the central overlapping area are located directly below the diagonal position of the high-layer pixel.

[0013] A method for preparing the novel multi-layer infrared detector described above comprises the following steps:

[0014] Step 1: On a substrate with a readout circuit, a plurality of microbridge resonant cavity structures arranged in an M*N array are manufactured to form a first layer of pixel sets;

[0015] Step 2: Continue to make multiple microbridge resonant cavity structures arranged in an (M+1)*(N+1) array on the first layer of pixel sets to form a second layer of pixel sets. The second layer of pixel sets completely covers the first layer of pixel sets and are arranged in pairs. In the second layer of pixel sets, the microbridge resonant cavity structure of each pixel includes two supports and electrical connection holes arranged at diagonal positions.

[0016] For the second layer of pixels in the central overlapping area, the bottoms of the two support and electrical connection holes are respectively in contact with the positions near the centers of the two adjacent pixels in the first layer of pixel set directly below them, and are connected to the electrode layers in the microbridge resonant cavity structures of the two adjacent pixels;

[0017] For the second layer of pixels in the peripheral non-overlapping area, the depth of one support and electrical connection hole is greater than the other, the bottom of the support and electrical connection hole with a smaller depth is in contact with a position near the center of the corresponding pixel in the first layer of pixel set directly below it, and is connected to the electrode layer in the microbridge resonant cavity structure of the corresponding pixel; the bottom of the support and electrical connection hole with a larger depth is connected to the substrate;

[0018] Step 3: Repeat steps 1 to 2, and the number of rows and columns of the upper array arrangement in the pixel sets of two adjacent layers are one more than the number of rows and columns of the lower array arrangement, until the production of pixel sets of all layers is completed.

[0019] The beneficial technical effects of the present invention are:

[0020] 1. With the help of staggered arrangement, the bridge deck of the microbridge in the high-level pixels covers the beam structure, support and electrical connection holes of the microbridge in the low-level pixels, and the gaps between adjacent pixels, thereby increasing the absorption area of ​​infrared rays, improving the infrared absorption efficiency, and improving product performance under the premise of controllable costs.

[0021] 2. The projection surface of each low-level pixel overlaps with one-fourth of the projection surface of four adjacent high-level pixels corresponding to two adjacent rows or columns, and its center is on the same straight line with the centers of the four high-level pixels. Therefore, it can be considered that a beam of infrared light irradiated from the centers of the four high-level pixels can be divided into four beams that are incident on the low-level pixels directly below, thus completing the array expansion of the low-level pixel set in disguise, improving the accuracy of infrared imaging, greatly enhancing the performance of the product, and having great application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic diagram comparing a partial cross-sectional view and a three-dimensional structure of a central overlapping region of a pixel set arranged in a two-layer array of the present invention;

[0023] Figure 2 A partial cross-sectional view of a non-overlapping area around a set of pixels arranged in a two-layer array of the present invention;

[0024] Figure 3 A schematic top view of a pixel set arranged in a two-layer array of the present invention;

[0025] Figure 4 It is a top view schematic diagram of the first layer 2*2 pixel set and the second layer 3*3 pixel set of the present invention when they are arranged in a staggered manner. DETAILED DESCRIPTION

[0026] The specific implementation of the present invention is described in detail below with reference to the accompanying drawings and preferred embodiments.

[0027] The present invention provides a novel multi-layer infrared detector, comprising a multi-layer array of pixel sets arranged on a substrate with a readout circuit, such as Figure 1 and 2 As shown in the figure, the corresponding high-level pixels and low-level pixels in the pixel sets of two adjacent layers are staggered, and the projection surface of the microbridge deck in the high-level pixels overlaps with the projection surface of the beam structure, support and electrical connection holes of the microbridge in the low-level pixels, and the gap between adjacent pixels. In this way, with the help of staggered arrangement, the microbridge deck in the high-level pixels covers the beam structure, support and electrical connection holes of the microbridge in the low-level pixels, and the gap between adjacent pixels, increasing the infrared absorption area, improving the infrared absorption efficiency, and improving product performance under the premise of controllable costs.

[0028] Specifically, the projection surface of each low-level pixel partially overlaps with the projection surfaces of four adjacent high-level pixels corresponding to two adjacent rows or columns. In this way, the partial projection surface combination from the above four high-level pixels covers most of the low-level pixels, and the gaps, supports and electrical connection holes, and even the beam structures of the corresponding adjacent pixels fall on the micro-bridge surface of the low-level pixels, thereby increasing the absorption area of ​​infrared rays and improving the infrared absorption efficiency. It can be that one-quarter of the projection surface of the above four high-level pixels overlaps with the low-level pixels, and their center points are on the same straight line as the center points of the low-level pixels, which is equivalent to each low-level pixel being divided into four equal parts. In this way, it can be considered that a beam of infrared rays irradiated from the centers of the four high-level pixels can be divided into four beams that are incident on the low-level pixels directly below, thereby completing the array expansion of the low-level pixel set in disguise, improving the accuracy of infrared imaging, and greatly improving the performance of the product, which has great application prospects.

[0029] For example, a two-layer array of pixel sets is arranged on a substrate with a readout circuit, such as Figure 3 and 4As shown, the first layer is provided with 2*2 pixels, marked as A1, A2, A3, A4, and the second layer is provided with 3*3 pixels, marked as B1, B2...B9, then the array corresponding to the pixel set of the first layer is expanded to form a 4*4 array, that is, (B1+A1) / 4, (A1+B2) / 4, (A2+B2) / 4, (A2+B3) / 4; (A1+B4) / 4, (A1+B5) / 4, (A2+B5) / 4, (A2+B6) / 4; (A3+B4) / 4, (A3 +B5) / 4, (A4+B5) / 4, (A4+B6) / 4; (A3+B7) / 4, (A3+B8) / 4, (A4+B8) / 4, (A4+B9) / 4, among which, (A1+B1) / 4 represents the quarter of the projection surface of pixel A1 overlapping with pixel B1, (A1+B2) / 4 represents the quarter of the projection surface of pixel A1 overlapping with pixel B2, (A2+B2) / 4 represents the quarter of the projection surface of pixel A2 overlapping with pixel B2, and so on, up to (A4+B9) / 4.

[0030] When making multi-layer pixel sets, the high-level pixel sets in the pixel sets of two adjacent layers can completely cover the low-level pixel sets, and the two layers are staggered in correspondence. If the high-level pixel sets are divided into the peripheral non-overlapping area and the central overlapping area, such as Figure 1-4 As shown, the high-level pixels in the central overlapping area are connected to the electrode layers of the corresponding low-level pixels through the support and electrical connection holes, and finally realize electrical connection with the substrate; while some parts of the high-level pixels in the peripheral non-overlapping area are suspended, and can be directly electrically connected to the substrate through a support and electrical connection hole with a larger depth. In this way, while realizing the electrical connection, it can also provide support for the surrounding high-level pixels, and of course, support can also be achieved through a false structure; the non-suspended parts can be connected to the electrode layer of the corresponding low-level pixels through the same support and electrical connection holes as the high-level pixels in the central overlapping area, and finally realize electrical connection with the substrate.

[0031] Assume that the incident light signal passes through the first layer and then transmits to the second layer after being focused by the optical imaging lens, and the intensity of the signal incident to the first layer is the same as that of the signal incident to the second layer at the same position, i.e., projection position and area. Figure 4As shown, the middle area circled by the solid line is the central overlapping area, that is, the new 4*4 array after the algorithm expansion, and the other areas are the peripheral non-overlapping areas. At this time, the expanded pixel in the upper left corner is the upper left corner 1 / 4 area of ​​pixel A1, which overlaps with the lower right corner 1 / 4 area of ​​pixel B1. The input light signal illuminates 1 / 4 area of ​​pixel A1, and then projects to 1 / 4 area of ​​pixel B1. Assuming that the signal strength within the corresponding area of ​​each pixel is uniform and equal, the signal strength corresponding to the newly expanded pixel is the sum of the signal strengths corresponding to pixel A1 / 4 and pixel B1 / 4.

[0032] And so on:

[0033] The signal strength of the four pixels in the first row after expansion is:

[0034] The sum of the signal strengths of pixel A1 / 4 and pixel B1 / 4, the sum of the signal strengths of pixel A1 / 4 and pixel B2 / 4, the sum of the signal strengths of pixel A2 / 4 and pixel B2 / 4, and the sum of the signal strengths of pixel A2 / 4 and pixel B3 / 4;

[0035] The signal strength of the four pixels in the second row of pixels is:

[0036] The sum of the signal strengths of pixel A1 / 4 and pixel B4 / 4, the sum of the signal strengths of pixel A1 / 4 and pixel B5 / 4, the sum of the signal strengths of pixel A2 / 4 and pixel B5 / 4, and the sum of the signal strengths of pixel A2 / 4 and pixel B6 / 4;

[0037] The signal strength of the four pixels in the third row of pixels is:

[0038] The sum of the signal strengths of pixel A3 / 4 and pixel B4 / 4, the sum of the signal strengths of pixel A3 / 4 and pixel B5 / 4, the sum of the signal strengths of pixel A4 / 4 and pixel B5 / 4, and the sum of the signal strengths of pixel A4 / 4 and pixel B6 / 4;

[0039] The signal strengths of the four pixels in the fourth row of pixels are:

[0040] The sum of the signal strengths of pixel A3 / 4 and pixel B7 / 4, the sum of the signal strengths of pixel A3 / 4 and pixel B8 / 4, the sum of the signal strengths of pixel A4 / 4 and pixel B8 / 4, and the sum of the signal strengths of pixel A4 / 4 and pixel B9 / 4.

[0041] Assume that the pixels in each layer of pixel set are respectively provided with a sacrificial layer, a sensitive layer, an electrode layer, a release protection layer and an absorption layer from bottom to top, and the electrode layer is located above the sensitive layer, covers the microbridge surface of each pixel, and has a pattern. In this way, for the high-level pixel in the central overlapping area, the sensitive layer resistor defined by the electrode pattern is connected to the electrode layers of the two adjacent low-level pixels through two supports and electrical connection holes, until it is electrically connected to the substrate. The two supports and electrical connection holes can be set at the diagonal position of the high-level pixel, and the two low-level pixels connected thereto are located directly below the diagonal position of the high-level pixel, which can be the lower left, upper right, or upper left and lower right, such as Figure 3 As shown, this can not only simplify the structure and facilitate the process, but also ensure the stability of the entire structure and a good electrical connection effect;

[0042] For high-level pixels in the peripheral non-overlapping area, one of the support and electrical connection holes has a depth greater than the other. The sensitive layer resistor defined by the electrode pattern is electrically connected to the substrate through the support and electrical connection hole with a larger depth, and is connected to the electrode layer of the adjacent low-level pixels through the support and electrical connection hole with a smaller depth until it is electrically connected to the substrate. Similarly, the two support and electrical connection holes with different depths can also be set at the diagonal position of the high-level pixels, which is consistent with the high-level pixels in the central overlapping area, so as to facilitate unified production and reduce the complexity of the process.

[0043] The present invention also provides a method for preparing the novel infrared detector described above, such as Figure 1 and 2 As shown, the specific steps include:

[0044] Step 1: On a substrate with a readout circuit, a plurality of microbridge resonant cavity structures arranged in an M*N array are fabricated by a deposition and etching process to form a first layer of pixel sets;

[0045] Step 2: Continue to make multiple microbridge resonant cavity structures arranged in an (M+1)*(N+1) array on the first layer of pixel sets to form a second layer of pixel sets. The second layer of pixel sets completely covers the first layer of pixel sets and are arranged in pairs. In the second layer of pixel sets, the microbridge resonant cavity structure of each pixel includes two supports and electrical connection holes arranged at diagonal positions.

[0046] For the second layer of pixels in the central overlapping area, the bottoms of the two support and electrical connection holes are respectively in contact with the positions near the centers of the two adjacent pixels in the first layer of pixel set directly below them, and are connected to the electrode layers in the microbridge resonant cavity structures of the two adjacent pixels in the first layer of pixel set;

[0047] For the second layer of pixels in the peripheral non-overlapping area, the depth of one support and electrical connection hole is greater than the other, the bottom of the support and electrical connection hole with a smaller depth is in contact with a position near the center of the corresponding pixel in the first layer of pixel set directly below it, and is connected to the electrode layer in the microbridge resonant cavity structure of the corresponding pixel in the first layer of pixel set; the bottom of the support and electrical connection hole with a larger depth is connected to the substrate;

[0048] Step 3: Repeat steps 1 to 2, and the number of rows and columns of the upper array in the pixel sets of two adjacent layers are one more than the number of rows and columns of the lower array, until the production of all layers of pixel sets is completed to form the final product.

[0049] The above description is only a preferred embodiment of the present invention, and the embodiment is not intended to limit the protection scope of the present invention. Therefore, all equivalent structural changes made using the description and drawings of the present invention should be included in the protection scope of the claims attached to the present invention.

Claims

1. A new type of multi-layer infrared detector, characterized by: A pixel set comprising a multi-layer array arrangement on a substrate with a readout circuit, each pixel comprising a microbridge resonant cavity structure including a microbridge deck, a beam structure, a support and an electrical connection hole, the corresponding high-level pixels and low-level pixels in the pixel sets of two adjacent layers are arranged staggered with each other, and the projection surface of the microbridge deck in the high-level pixel overlaps with the projection surface of the beam structure, the support and the electrical connection hole in the low-level pixel, and the gap between adjacent pixels; The projection surface of each of the low-layer pixels partially overlaps with the projection surfaces of four high-layer pixels in two adjacent rows or columns of the upper layer corresponding to the position of the low-layer pixel; The center point of the projection surface of each low-layer pixel and the center point of the overall image composed of the projection surfaces of four high-layer pixels in two adjacent rows or columns of the upper layer corresponding to the position of the low-layer pixel are located on the same straight line.

2. The novel multi-layer infrared detector according to claim 1 is characterized in that: Two layers of array-arranged pixel sets are arranged on the substrate with a readout circuit. The first layer is provided with 2*2 pixels, which are marked as A1, A2, A3, and A4 respectively. The second layer is provided with 3*3 pixels, which are marked as B1, B2...B9 respectively. Then, the array corresponding to the first layer of pixel sets is expanded to form a 4*4 array, namely (A1+B1) / 4, (A1+B2) / 4, (A2+B2) / 4, (A2+B3) / 4; (A1+B4) / 4, (A1+B5) / 4, (A2+B5) / 4, (A2+B6) / 4; (A3+B4) / 4, (A3+B5) / 4, (A4+B5) / 4, (A4+B6) / 4; (A3+B7) / 4, (A3+B8) / 4, (A4+B8) / 4, (A4+B9) / 4, where (A1+B1) / 4 represents one quarter of the projection surface of pixel A1 that overlaps with pixel B1, and so on, up to (A4+B9) / 4.

3. The novel multi-layer infrared detector according to claim 1 is characterized in that: The high-level pixel set in the pixel sets of the two adjacent layers completely covers the low-level pixel set, and the high-level pixel set is divided into a peripheral non-overlapping area and a central overlapping area. The high-level pixels in the peripheral non-overlapping area are connected to the substrate through support and electrical connection holes, and the high-level pixels in the central overlapping area are connected to the electrode layer of the corresponding low-level pixels through support and electrical connection holes to achieve electrical connection with the substrate.

4. The novel multi-layer infrared detector according to claim 3 is characterized in that: The pixels in each layer of the pixel set are respectively provided with a sensitive layer, an electrode layer, a release protection layer and an absorption layer from bottom to top. The electrode layer is located on the sensitive layer, covers the surface of each pixel, and has a pattern; at the same time, for the high-level pixels in the central overlapping area, the sensitive layer resistor defined by the electrode pattern is respectively connected to the electrode layers of two adjacent low-level pixels through two supports and electrical connection holes. For high-level pixels in the peripheral non-overlapping area, one support and electrical connection hole has a depth greater than the other. The sensitive layer resistor defined by the electrode pattern is electrically connected to the substrate through the support and electrical connection hole with a larger depth, and is connected to the electrode layer of the adjacent low-level pixels through the support and electrical connection hole with a smaller depth.

5. The novel multi-layer infrared detector according to claim 4 is characterized in that: Two lower-layer pixels respectively connected to two supports and electrical connection holes of the higher-layer pixel located in the central overlapping area are located directly below the diagonal position of the higher-layer pixel.

6. A method for preparing the novel multi-layer infrared detector as claimed in claim 1, characterized in that The following steps are involved: Step 1: On a substrate with a readout circuit, a plurality of microbridge resonant cavity structures arranged in an M*N array are manufactured to form a first layer of pixel sets; Step 2: Continue to make multiple microbridge resonant cavity structures arranged in an (M+1)*(N+1) array on the first layer of pixel sets to form a second layer of pixel sets, the projection surface of each low-layer pixel partially overlaps with the projection surfaces of four high-layer pixels in two adjacent rows or columns of the upper layer corresponding to the position of the low-layer pixel, the center point of the projection surface of each low-layer pixel and the center point of the overall image composed of the projection surfaces of four high-layer pixels in two adjacent rows or columns of the upper layer corresponding to the position of the low-layer pixel are located on the same straight line, the second layer of pixel sets completely covers the first layer of pixel sets and are staggered in pairs, in the second layer of pixel sets, the microbridge resonant cavity structure of each pixel includes two supports and electrical connection holes arranged at diagonal positions, For the second layer of pixels in the central overlapping area, the bottoms of the two support and electrical connection holes are respectively in contact with the positions near the centers of the two adjacent pixels in the first layer of pixel set directly below them, and are connected to the electrode layers in the microbridge resonant cavity structures of the two adjacent pixels; For the second layer of pixels in the peripheral non-overlapping area, the depth of one support and electrical connection hole is greater than the other, the bottom of the support and electrical connection hole with a smaller depth is in contact with a position near the center of the corresponding pixel in the first layer of pixel set directly below it, and is connected to the electrode layer in the microbridge resonant cavity structure of the corresponding pixel; the bottom of the support and electrical connection hole with a larger depth is connected to the substrate; Step 3: Repeat steps 1 to 2, and the number of rows and columns of the upper array arrangement in the pixel sets of two adjacent layers are one more than the number of rows and columns of the lower array arrangement, until the production of pixel sets of all layers is completed.

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