A small-pixel long-line infrared focal plane array and detector

Abstract

The application discloses a small-pixel long-line infrared focal plane array and a detector, and belongs to the technical field of infrared photoelectric detection. m The small-pixel long-line infrared focal plane array is provided with a special-arranged group-pixel array, so that the center distance of two adjacent pixels in the line direction along the line direction is equal to the minimum pixel size in the process d , the center distance between two physically adjacent pixels in the line direction in each group-pixel array is expanded to m × d , the etching groove width g between the pixels is also increased under the precondition that the photosensitive area is not reduced, the anti-crosstalk effect is further improved, and an area exceeding the pixel size, i.e. m × s )× d 2 More complex readout circuit pixel circuit functions can be realized, and more process node selections can be provided.

Description

Technical Field

[0001] This invention relates to a small-pixel long linear infrared focal plane array and detector, belonging to the field of infrared photoelectric detection technology. Background Technology

[0002] Infrared photoelectric imaging detectors are imaging infrared detection devices that convert target infrared radiation into electrical signals and reconstruct infrared images based on the photoelectric conversion mechanism and an array pixel structure. According to the pixel arrangement dimension, they can be divided into one-dimensional long linear infrared focal plane detectors and two-dimensional area array infrared focal plane detectors. One-dimensional long linear infrared focal plane detectors focus on wide swath scanning and spectral detection, sacrificing signal-to-noise ratio and integral degrees of freedom for ultra-wide lateral coverage. They are often used in scenarios such as aerospace remote sensing pushbroom cameras, airborne infrared scanners, infrared spectral detection, and wide-swath online scanning detection. On the other hand, area array detectors focus on real-time two-dimensional staring imaging, low noise, and high sensitivity. They are often used in real-time observation scenarios with a fixed field of view.

[0003] For one-dimensional long linear infrared focal plane arrays, the size of the focal plane array directly affects the resolution. Therefore, it is often used to maximize the number of pixels in the linear direction by setting narrow, small pixels (i.e., the length of a single pixel along the scanning direction is greater than its length along the linear direction). To further improve resolution, the pixel pitch can usually be reduced, thereby obtaining a larger linear pixel size within the same wafer size. In long linear infrared focal plane arrays, the pixel pitch consists of two parts: the pixel size and the pixel position. d (i.e., the length of the pixel along the column direction) and the width g of the etching trench between pixels; if the pixel size is reduced d On the one hand, this will result in a reduction in the photosensitive area, a significant drop in signal strength, and a deterioration in the SNR (Signal-to-Noise Ratio). On the other hand, since the readout circuit is located below the pixel, reducing the pixel pitch will reduce the pixel circuit area of ​​the readout circuit, which is detrimental to the design and development of the readout circuit. Moreover, due to limitations in etching, flip-chip interconnect, and other processes, there is a minimum pixel size that the process allows. d If the width g of the inter-pixel etching trench is reduced, the image quality will decrease (the width g of the etching trench is a key structural parameter for reducing inter-pixel crosstalk, which affects the image quality); therefore, the existing technology cannot achieve higher resolution by further reducing the pixel pitch.

[0004] To compensate for the reduction in pixel size dOne existing technique to address signal attenuation caused by smaller pixel size is to use an M-row, N-column linear array. This array is then integrated using Time Delay and Integration (TDI) to accumulate M rows of charge, thereby enhancing the equivalent signal and offsetting the signal attenuation caused by the smaller pixel size. However, in this approach, the pixel spacing along the linear array direction remains the same as the pixel size. d + The width of the inter-pixel etching trench is g, therefore the increase in the number of pixels in the linear direction depends on the size of each pixel. d The reduction in size has a limited effect on improving resolution, and this scheme places higher design requirements on carrier motion stability, readout circuit timing control, and multi-channel uniform correction. Summary of the Invention

[0005] To maximize resolution without reducing the photosensitive area to meet the needs of applications such as meteorological satellite scanning and remote sensing of atmospheric pollution sources, this invention provides a small-pixel long linear infrared focal plane array and detector. By arranging multiple sets of pixels, the process spacing of traditional arrangement methods is eliminated, so that the center distance of pixels in the linear direction of the infrared detector reaches the minimum process pixel size. This achieves maximum resolution without reducing the photosensitive area, and also provides an area beyond the pixel size for readout circuit design, enabling more complex readout circuit pixel circuit functions.

[0006] The first objective of this invention is to provide a small-pixel long-line infrared focal plane array, the array comprising a total of m × x × y 100 pixels, the pixel size in the linear direction is 100 pixels. m × x Scan direction settings y Each pixel achieves TDI; m × x × y Each pixel is divided into m Group pixel array, m ≥2, the m The pixel arrays are arranged sequentially along the scanning direction, and each pixel array contains y OK x Column pixels, that is, a total of [number] pixels in the column direction x There are [number] pixels, and the scanning direction has [number] pixels. y Each pixel, with pixel size denoted as . d × d ; The first column of pixels in each pixel array is arranged in a stepped indentation along the column direction, and the center-to-center distance between the first column pixels of two adjacent pixel arrays along the column direction is... d .

[0007] Optionally, in each pixel array, the center-to-center distance between two adjacent pixels in the linear direction is... m × d The center-to-center distance between two adjacent pixels in the scanning direction is s × d , s ≥2.

[0008] Optional, the first i Group (1 < i ≤ m ) the first pixel array y row pixels and the first i The center-to-center spacing of the first row of pixels in the +1 pixel array along the scanning direction is... n × d , n ≥ s .

[0009] Optionally, the first pixel of the first pixel array and the second pixel... i The center-to-center spacing of the first pixel in the pixel array along the column direction is ( i -1)× d The first pixel of the first pixel array and the second pixel... i The center-to-center spacing of the first pixel in the pixel array along the scanning direction is ( m -1)×[(y-1)× s + n ]× d .

[0010] The second objective of this invention is to provide a small-pixel long-line infrared focal plane array detector chip, wherein the chip is provided with the aforementioned small-pixel long-line infrared focal plane array, and the length of the line array along the chip is... m × x × d The width along the scanning direction is ( s × y - s + n )× m × d+ (1- n )× d .

[0011] A third objective of the present invention is to provide a small-pixel long-line infrared focal plane detector, wherein the detector comprises the aforementioned small-pixel long-line infrared focal plane array or the aforementioned small-pixel long-line infrared focal plane detector chip.

[0012] Optionally, when the detector performs imaging, the first pixel along the line column direction, i.e., the first column of pixels in the first group of pixel arrays, and the first column of pixels in the first group of pixel arrays... yThe TDI signal integral of each pixel is the signal acquired by the first pixel; the second pixel along the column direction is the first column of the second group of pixel arrays, and the first column of the second group of pixel arrays... y The TDI signal integral of the first pixel is the signal acquired by the second pixel; ..., along the column direction, the first... m The pixel is the first m The first column of pixels in the group pixel array, the m The first column in the group pixel array y The integral of the TDI signal of the nth pixel is the nth m The signal obtained by each pixel; Along the column direction m +1 pixel, which is the second column of pixels in the first group of pixel arrays. y The integral of the TDI signal of the nth pixel is the nth m +1 pixel's acquired signal; ..., along the column direction, the 2nd... m The pixel is the first m The second column of pixels in the group pixel array, the first m The second column in the group pixel array y The TDI signal integration of each pixel is the second... m The signal acquired from the first pixel; ..., along the column direction, the second... m The pixel is the first m The second column of pixels in the group pixel array, the first m The second column in the group pixel array y The TDI signal integration of each pixel is the second... m The signal acquired from the first pixel; ..., along the column direction, the signal acquired from the first pixel; ... m × x The pixel is the first m The first in the group of pixel array x Column, number m The first in the group of pixel array x Columns y The integral of the TDI signal of the nth pixel is the nth m × x The signal obtained from each pixel; thus, the direction of the linear array is obtained. m × x An accumulated signal, detector output m × x A linear image composed of accumulated signals.

[0013] Optionally, the detector further includes a readout circuit corresponding to each pixel, the usable area of ​​which is ( m × s )× d 2 .

[0014] The present invention also provides the application of the above-mentioned detector in meteorological satellite scanning and remote sensing of atmospheric pollution sources.

[0015] The beneficial effects of this invention are: By setting a special arrangement m A pixel array is configured such that the center-to-center distance between two abstractly adjacent pixels along the linear direction is equal to the minimum pixel size in the manufacturing process. d Under the same pixel size conditions, the present invention can obtain a larger number of linear pixel sizes; in the present invention, the center-to-center distance between two physically adjacent pixels in the linear direction in each pixel array is increased to m × d Without reducing the photosensitive area, the width g of the inter-pixel etching trenches is increased, further improving the anti-crosstalk effect. This enables the creation of mesa pixels with high fill factor, maximizing the signal-to-noise ratio while maintaining MTF, achieving excellent imaging quality. Furthermore, it provides an area exceeding the pixel size for readout circuit design, i.e. ( m × s )× d 2 This allows for more complex readout circuit pixel circuit functions and provides more process node options; the present invention's solution arranges the pixel circuit along the scanning direction. y The center-to-center distance is s × d (s is any integer ≥ 2) pixels, to implement y The Time Delay Integral (TDI) level compensates for the signal-to-noise ratio loss caused by pixel reduction. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the small pixel long linear infrared focal plane array arrangement of the present invention; Figure 2 It is a pixel center distance chart for the traditional pixel-adjacent arrangement method; Figure 3 This is a schematic diagram of the arrangement of a long linear infrared focal plane array of small pixels representing the linear direction pixels, according to the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0019] Example 1 This embodiment provides a small-pixel long linear infrared focal plane array, see [link to previous document]. Figure 1 The small-pixel long linear infrared focal plane array includes arrays arranged sequentially along the scanning direction. m Group pixel array, m ≥2, each cell array contains y OK x Column pixels, that is, a total of [number] pixels in the column direction x There are [number] pixels, and the scanning direction has [number] pixels. y Each pixel, with pixel size denoted as . d × d .

[0020] In each pixel array, the center-to-center distance between two adjacent pixels in the linear direction is... m × d The center-to-center distance between two adjacent pixels in the scanning direction is s × d , s ≥2. In practical applications, the area required by the readout circuit can be determined. s The specific value of ; and to facilitate subsequent image processing time correction, s Take the integer part.

[0021] No. i Group (1 < i ≤ m ) the first pixel array y row pixels and the first i The center-to-center spacing of the first row of pixels in the +1 pixel array along the scanning direction is... n × d , n ≥ s The design of the group spacing being greater than or equal to the intra-group spacing in this application is to ensure the area of ​​the readout circuit; the positions of the first column pixels of each group of pixel arrays are arranged in a stepped indentation along the column direction, and the center-to-center spacing of the first column pixels of two adjacent groups of pixel arrays along the column direction is... d .

[0022] The above m The pixel array contains a total of m × x × y 1 pixel, the pixel size in the linear direction is 1. m × x The scanning direction has y The first pixel of the first pixel array can achieve TDI (Time Delay Integration). iThe center-to-center spacing of the first pixel in the pixel array along the column direction is ( i -1)× d The first pixel of the first pixel array and the second pixel... i The center-to-center spacing of the first pixel in the pixel array along the scanning direction is ( m -1)×[(y-1)× s + n ]× d .

[0023] Based on the above m The length of the infrared focal plane detector chip fabricated by arranging the pixel array along the line column is m × x × d The width along the scanning direction is ( s × y - s + n )× m × d+ (1- n )× d .like Figure 3 As shown, when imaging using this infrared focal plane detector, the first pixel along the line column direction is the first column of pixels in the first group of pixel arrays, and the first column of pixels in the first group of pixel arrays... y The TDI signal integral of each pixel is the signal acquired by the first pixel; the second pixel along the column direction is the first column of the second group of pixel arrays, and the first column of the second group of pixel arrays... y The TDI signal integral of the first pixel is the signal acquired by the second pixel; ..., along the column direction, the first... m The pixel is the first m The first column of pixels in the group pixel array, the m The first column in the group pixel array y The integral of the TDI signal of the nth pixel is the nth m The signal acquired by the pixel along the column direction. m +1 pixel, which is the second column of pixels in the first group of pixel arrays. y The integral of the TDI signal of the nth pixel is the nth m +1 pixel's acquired signal; ..., along the column direction, the 2nd... m The pixel is the first m The second column of pixels in the group pixel array, the first m The second column in the group pixel array y The TDI signal integration of each pixel is the second... m The signal acquired from the first pixel; ..., along the column direction, the second... m The pixel is the firstm The second column of pixels in the group pixel array, the first m The second column in the group pixel array y The TDI signal integration of each pixel is the second... m The signal acquired by the first pixel. ..., along the column direction, the signal acquired by the first pixel. m × x The 1st pixel (the last pixel), i.e., the 1st... m The first in the group of pixel array x Column, number m The first in the group of pixel array x Columns y The integral of the TDI signal of the nth pixel is the nth m × x The signal obtained from each pixel; thus, the direction of the linear array is obtained. m × x An accumulated signal, detector output m × x A linear image composed of accumulated signals.

[0024] This application's solution uses a special arrangement. m A pixel array is configured such that the center-to-center distance between two abstractly adjacent pixels along the linear direction is equal to the minimum pixel size in the manufacturing process. d Furthermore, the center-to-center spacing between two physically adjacent pixels in the linear column direction within each pixel array is increased to m × d Without reducing the photosensitive area, the width g of the inter-pixel etching trench was increased, further improving the anti-crosstalk effect. Moreover, it provided an area exceeding the pixel size for the readout circuit design, i.e. ( m × s )× d 2 It can realize more complex readout circuit pixel circuit functions and provide more process node options.

[0025] Example 2 This embodiment provides a small-pixel long linear infrared focal plane array detector, including the small-pixel long linear infrared focal plane array and the corresponding readout circuit provided in Embodiment 1, as detailed below: First, based on existing process capabilities, determine the minimum pixel size supported by the process. d × d Based on the requirements of the optoelectronic system, determine the number of pixels that need to participate in the time delay integration. y .

[0026] Based on the technical requirements of the readout circuit, assess the area required for the pixel circuit and determine the pixel center spacing in the line column direction: Pitch L = m× d ( m ≥2); Determine the pixel center spacing in the scanning direction: Pitch S = s × d ( s ≥2); Determine the number of pixel groups m =Pitch L / d Set the center-to-center spacing of pixels along the scanning direction between adjacent groups: Gap group = n × d ( n ≥ s ).

[0027] The width of the photosensitive element array chip along the scanning direction was calculated as follows: W = ( s × y - s + n )× m × d +(1- n )× d .

[0028] Assuming the effective process area of ​​the infrared photosensitive wafer is [diameter value missing] R The longest length of the circle along the line column direction of the photosensitive element array chip: ; The pixel size along the line column direction is calculated based on the size of the selected wafer: N L =m × x= L / d In the formula, " " is the floor symbol; Then, within each group, the number of pixels in the linear direction is: x = L / d / m .

[0029] In summary, the design elements of a pixel layout can be derived as follows: Center-to-center spacing of pixels in each inner column: Pitch L ; Spacing between center-to-center pixels in each scan direction: Pitch S ; Pixel size: Pitch = d ; Number of pixel groups: m= Pitch L / d ; Center-to-center spacing between adjacent groups along the scanning direction: Gap group =n × d ( n ≥ s ); Number of pixels in each inner column direction: x = / d / m In the formula: W= ( s × y - s + n )× m × d +( 1 - n )× d ; Number of pixels in each scan direction within each group: y .

[0030] Based on the above elements, refer to Figure 1 The process of creating a photolithographic pattern and using it to fabricate an infrared focal plane array includes the following main steps: wafer cleaning; mask deposition, pattern photolithography development, mask etching, pattern etching, and mask removal; mask deposition, mesa etching pattern photolithography development, mask etching, mesa etching, and mask removal; pixel passivation layer deposition, passivation aperture pattern photolithography development, and passivation aperture; electrode pattern photolithography development, electrode deposition, and electrode stripping; and dicing.

[0031] The corresponding readout circuit is designed to read out the infrared focal plane pixel signal, wherein... y The Level TDI accumulation function is designed to accumulate the first pixel within the same group. T The signal integrated at time 0, the second pixel's T 0-2× T The signal for time-integration... y one pixel T 0 -y × T The signal integrated over time is accumulated and output, where T is the line period time of the detector.

[0032] Based on the signal output from the readout circuit, the image data is processed: time correction is performed on the stored image data, and the first group of pixels... T Image data exposed at time 0, and the second set of pixels T 0+[(y-1 )× s + n ]× T Image data exposed at different times... m group T 0 + ( m - 1 )×[( y-1 )× s + n ]× T Image data exposed at any given time is time-aligned.

[0033] Specific implementation examples: It is known that existing process conditions can support a minimum size of 10μm × 10μm (i.e. d Given a pixel size of 10 μm, the number of pixels required for time delay integration is determined based on the requirements of the optoelectronic system. y =10.

[0034] Based on the technical requirements of the readout circuit, assess the area required for the pixel circuit and determine the center-to-center spacing of pixels in the line column direction: Pitch L = m × d =40μm, m =4; Pixel center-to-center spacing in the scanning direction: Pitch S = s × d =40μm, s =4; Then determine the number of pixel groups: m= Pitch L / d= 4; Spacing between adjacent groups: Gap group =n × d ( n ≥ s =80μm, n =8; The width of the photosensitive element array chip along the scanning direction can be obtained: W= ( s × y - s + n )× m × d +( 1 - n )× d=1690μm ; Assuming the effective process area of ​​the infrared photosensitive wafer is [diameter value missing] 40.8mmThe longest length of the photosensitive element array chip along the line column direction (2-inch wafer minus 10mm process edge): =40764.98 μm ; Then the cell size along the column direction: N L =m × x= L / d =4076; Then, within each group, the number of pixels in the linear direction is: x = L / d / m= 4076 / 4=1019.

[0035] However, if the existing arrangement is followed, even if the width of the inter-pixel etching trench, g, is taken as the minimum process value of 2μm, and the width of the photosensitive element array chip along the scanning direction is set to 5mm to ensure the mechanical strength of the photosensitive element array chip, then the pixel scale in the linear direction will be... N L The calculation process is as follows: ; ; It can be seen that, if the current arrangement is followed, the pixel scale in the linear direction... N L The current solution can only reach 3374, which is far less than the 4076 that the proposed solution can achieve. This is very important for applications requiring high resolution, such as meteorological satellite scanning and remote sensing of atmospheric pollution sources. Moreover, the existing arrangement will reduce the area of ​​the readout circuit, which will be detrimental to the design and development of the readout circuit.

[0036] Based on the above description, the design elements of the pixel layout in this application are as follows: Center-to-center spacing of pixels in each inner column: Pitch L =40μm ; Spacing between center-to-center pixels in each scan direction: Pitch S =40μm ; Pixel size: Pitch = 10μm ; Number of pixel groups: m= 4 ; Spacing between adjacent groups: Gapgroup =80μm ; Number of pixels in each inner column direction: x =1019; Number of pixels in each scan direction within each group: 10 .

[0037] Based on the above elements, refer to Figure 1 The process of creating a photolithographic pattern and using it to fabricate an infrared focal plane array includes the following main steps: wafer cleaning; mask deposition, pattern photolithography development, mask etching, pattern etching, and mask removal; mask deposition, mesa etching pattern photolithography development, mask etching, mesa etching, and mask removal; pixel passivation layer deposition, passivation aperture pattern photolithography development, and passivation aperture; electrode pattern photolithography development, electrode deposition, and electrode stripping; and dicing.

[0038] Design a readout circuit to read out infrared focal plane pixel signals, wherein 10 The level TDI accumulation function is designed to accumulate the first pixel's TDI value. T The signal integrated at time 0, the second pixel's T 0-2× T The signal for time-integration... 10 one pixel T 0 -10 × T The signal integrated over time is accumulated and output, where T is the line period time of the detector.

[0039] Based on the signal output from the readout circuit, the image data is processed: time correction is performed on the stored image data, and the image data exposed at time T0 of the first group of pixels is compared with that of the second group of pixels. T 0+288× T Image data exposed at different times... Group 4 T 0 + 864× T Image data exposed at any given time is time-aligned.

[0040] Some steps in the embodiments of the present invention can be implemented using software, and the corresponding software program can be stored in a readable storage medium, such as an optical disc or a hard disk.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A small-pixel long linear infrared focal plane array, characterized in that, The array contains a total of m × x × y 100 pixels, the pixel size in the linear direction is 100 pixels. m × x Scan direction settings y Each pixel achieves TDI; m × x × y Each pixel is divided into m Group pixel array, m ≥2, the m The pixel arrays are arranged sequentially along the scanning direction, and each pixel array contains y OK x Column pixels, that is, a total of [number] pixels in the column direction x There are [number] pixels, and the scanning direction has [number] pixels. y Each pixel, with pixel size denoted as . d × d ; The first column of pixels in each pixel array is arranged in a stepped indentation along the column direction, and the center-to-center distance between the first column pixels of two adjacent pixel arrays along the column direction is... d .

2. The array according to claim 1, characterized in that, In each pixel array, the center-to-center distance between two adjacent pixels in the linear direction is... m × d The center-to-center distance between two adjacent pixels in the scanning direction is s × d , s ≥2.

3. The array according to claim 2, characterized in that, No. i Group (1 < i ≤ m ) the first pixel array y row pixels and the first i The center-to-center spacing of the first row of pixels in the +1 pixel array along the scanning direction is... n × d , n ≥ s .

4. The array according to claim 3, characterized in that, The first pixel of the first pixel array and the second i The center-to-center spacing of the first pixel in the pixel array along the column direction is ( i -1)× d ; The first pixel of the first pixel array and the second i The center-to-center spacing of the first pixel in the pixel array along the scanning direction is ( m -1)×[(y-1)× s + n ]× d .

5. A small-pixel long-line infrared focal plane detector chip, characterized in that, The chip is provided with a small-pixel long linear infrared focal plane array as described in any one of claims 1-4, wherein the length of the chip along the linear array is... m × x × d The width along the scanning direction is ( s × y - s + n )× m × d+ (1- n )× d .

6. A small-pixel long-line infrared focal plane detector, characterized in that, The detector comprises a small-pixel long linear infrared focal plane array as described in any one of claims 1-4 or a small-pixel long linear infrared focal plane detector chip as described in claim 5.

7. The detector according to claim 6, characterized in that, When the detector performs imaging, the first pixel along the line column direction is the first column of pixels in the first group of pixel arrays, and the first column of pixels in the first group of pixel arrays... y The TDI signal integral of each pixel is the signal acquired by the first pixel; the second pixel along the column direction is the first column of the second group of pixel arrays, and the first column of the second group of pixel arrays... y The TDI signal integral of the first pixel is the signal acquired by the second pixel; ..., along the column direction, the first... m The pixel is the first m The first column of pixels in the group pixel array, the m The first column in the group pixel array y The integral of the TDI signal of the nth pixel is the nth m The signal obtained by each pixel; Along the column direction m +1 pixel, which is the second column of pixels in the first group of pixel arrays. y The integral of the TDI signal of the nth pixel is the nth m +1 pixel's acquired signal; ..., along the column direction, the 2nd... m The pixel is the first m The second column of pixels in the group pixel array, the first m The second column in the group pixel array y The TDI signal integration of each pixel is the second... m The signal acquired from the first pixel; ..., along the column direction, the second... m The pixel is the first m The second column of pixels in the group pixel array, the first m The second column in the group pixel array y The TDI signal integration of each pixel is the second... m The signal acquired from the first pixel; ..., along the column direction, the signal acquired from the first pixel; ... m × x The pixel is the first m The first in the group of pixel array x Column, number m The first in the group of pixel array x Columns y The integral of the TDI signal of the nth pixel is the nth m × x The signal obtained from each pixel; thus, the direction of the linear array is obtained. m × x An accumulated signal, detector output m × x A linear image composed of accumulated signals.

8. The detector according to claim 7, characterized in that, The detector also includes a readout circuit for each pixel, and the available area of ​​the readout circuit is ( m × s )× d 2 .

9. The application of the detector according to any one of claims 6-8 in meteorological satellite scanning and remote sensing scenarios of atmospheric pollution sources.

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