Infrared Sensor and Imaging Device

Abstract

To provide an infrared sensor, etc., with which it is possible to reduce the warp of a board on which an infrared detection element is formed.SOLUTION: Provided is an infrared sensor comprising: a detection board including a first board where a plurality of infrared detection elements are arranged in lattice form and a first terminal associated with each of the infrared detection elements is arranged in plurality; a readout board including a second board where a second terminal associated with each of the plurality of first terminals is arranged in plurality, and on which is formed a readout circuit for reading out electric signals based on the infrared ray detected by each of the plurality of infrared detection elements; and a plurality of bumps for electrically connecting each of the plurality of first terminals to the plurality of second terminals associated with the plurality of first terminals, respectively. At least some of the plurality of first terminals, the plurality of second terminals and the plurality of bumps is arranged at a position between the adjacent infrared detection elements in a top view.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an infrared sensor for detecting infrared rays and the like.

Background Art

[0002] A general infrared sensor has a structure in which a substrate formed with a detection unit in which infrared detection elements for detecting infrared rays are arranged in a lattice pattern and a substrate formed with a readout circuit are flip-chip connected. For example, the material of the substrate on which the detection unit is formed is a compound semiconductor such as gallium arsenide (GaAs), and the material of the substrate on which the readout circuit is formed is silicon (Si). Each of the plurality of elements (also called pixels) included in the detection unit is connected one-to-one to each subsequent-stage circuit of the readout circuit by metal bumps. Therefore, the plurality of bumps connecting the detection unit and the readout circuit are arranged in a lattice pattern corresponding to the plurality of pixels.

[0003] A quantum-type infrared camera is used while being cooled by liquid helium or liquid nitrogen. Therefore, due to the difference in the coefficient of thermal expansion between the substrate (also called the detection substrate) on which the infrared detection element is formed and the substrate (also called the readout substrate) on which the readout circuit is formed, the infrared sensor is likely to warp. When warping occurs in the detection substrate and the readout substrate, cracks are likely to occur in the relatively thin detection substrate. When cracks occur in the detection substrate, unclear portions appear in the image captured by the quantum-type infrared camera.

[0004] Patent Document 1 discloses a display device including a substrate, conductive pads arranged over a plurality of rows on the substrate, and a drive circuit chip including bumps arranged over a plurality of rows so as to be electrically connected to the conductive pads. In the display device of Patent Document 1, the plurality of bumps arranged in the same row and corresponding to each of the plurality of conductive pads are arranged such that the positions of the centers of gravity or the ends in the column direction are zigzag and shifted from each other in the column direction between adjacent bumps.

[0005] Patent Document 2 discloses a method for manufacturing a hybrid device that electrically and mechanically joins a plurality of elements two-dimensionally arranged on a compound semiconductor crystal and an integrated circuit for processing signals from those elements using a plurality of bumps. The manufacturing method of Patent Document 2 includes two steps. The first step is a step of forming bumps on each of the compound semiconductor crystal and the integrated circuit such that the pitch of the bumps on the compound semiconductor crystal is larger than the pitch of the bumps on the integrated circuit. The second step is a step of thermally expanding each of the compound semiconductor crystal and the integrated circuit at different temperatures and joining them in a state where the pitches of the bumps of the compound semiconductor crystal and the integrated circuit match.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the method of Patent Document 1, adjacent bumps are arranged with a shift in the column direction. Therefore, in the method of Patent Document 1, due to factors such as pressure and temperature generated during the mounting process, cracks and damages are less likely to occur on the substrate when mounting the drive circuit chip. According to the method of Patent Document 1, regarding a plurality of conductive pads constituting the same row, warping and cracks can be reduced by shifting the bumps on the conductive pads. However, with the method of Patent Document 1, it was not possible to reduce warping and cracks generated between the conductive pads.

[0008] According to the method of Patent Document 2, at the liquid nitrogen temperature (77 Kelvin), which is the operating temperature of the device, the distance between the ends of the pixel array on the compound semiconductor crystal is smaller than the distance between the ends of the pixel array on the integrated circuit, resulting in the occurrence of bump distortion. According to the method of Patent Document 2, the distortion during cooling is reduced by an amount offset by the distortion at room temperature, so the deterioration of the diode characteristics caused by the stress due to the distortion during cooling is reduced. However, in the method of Patent Document 2, since distortion occurs in the bumps both at room temperature and during cooling, there is a possibility that the device may warp even at room temperature.

[0009] An object of the present invention is to provide an infrared sensor or the like that can reduce the warping of a substrate on which an infrared detection element is formed.

Means for Solving the Problems

[0010] An infrared sensor according to an aspect of the present invention includes a detection substrate including a first substrate on which a plurality of infrared detection elements are arranged in a lattice pattern and a plurality of first terminals associated with each of the infrared detection elements; a reading substrate including a second substrate on which a plurality of second terminals associated with each of the plurality of first terminals are arranged and a reading circuit for reading an electrical signal based on infrared rays detected by each of the plurality of infrared detection elements is formed; and a plurality of bumps for electrically connecting each of the plurality of first terminals and the plurality of second terminals associated with each of the plurality of first terminals. At least a part of the plurality of first terminals, the plurality of second terminals, and the plurality of bumps is arranged at a position between adjacent infrared detection elements in a top view.

Effects of the Invention

[0011] According to the present invention, it becomes possible to provide an infrared sensor or the like that can reduce the warping of a substrate on which an infrared detection element is formed.

Brief Description of the Drawings

[0012]

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MODE FOR CARRYING OUT THE INVENTION

[0013] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, although the embodiments described below have technically preferable limitations for carrying out the present invention, they do not limit the scope of the invention below. In all the drawings used in the description of the following embodiments, the same reference numerals are given to the same parts unless otherwise specified. In addition, in some of the drawings used in the description of the following embodiments, the x-axis, y-axis, and z-axis orthogonal to each other are shown to clarify the viewing angle. In addition, in the following embodiments, repeated descriptions of the same configuration and operation may be omitted.

[0014] (First Embodiment) First, the infrared sensor according to the first embodiment will be described with reference to the drawings. In this embodiment, it is assumed that an infrared sensor is mounted on a quantum type infrared camera in which the infrared sensor is cooled during use. Note that the infrared sensor of this embodiment is not limited to a quantum type infrared camera and can be applied to any infrared camera.

[0015] FIGS. 1 to 4 are conceptual diagrams for explaining the structure of the infrared sensor 100 of this embodiment. FIG. 1 is a plan view of the infrared sensor 100. FIG. 2 is a side view when the left side surface of the infrared sensor 100 in FIG. 1 is viewed. FIG. 3 is a side view when the lower side surface of the infrared sensor 100 in FIG. 1 is viewed. FIG. 4 is a plan view when a detection substrate 110 described later is removed. In FIG. 1, the electrodes (first terminals 115) of the detection substrate 110, the electrodes (second terminals 125) of the readout substrate 120, and the positions of the bumps 130 described later are indicated by broken lines. In FIGS. 2 to 4, for easy understanding, a plurality of bumps 130 constituting adjacent rows are shown with different hatchings.

[0016] The infrared sensor 100 includes a detection substrate 110, a readout substrate 120, and a plurality of bumps 130. The detection substrate 110 has a first substrate 111, a plurality of infrared detection elements 113, and a plurality of first terminals 115. The readout substrate 120 has a second substrate 121, a readout circuit 123, and a plurality of second terminals 125. Each of the plurality of first terminals 115 is associated with one of the plurality of second terminals 125. Each of the plurality of first terminals 115 is connected to the corresponding second terminal 125 via a bump 130. The infrared sensor 100 has a structure in which the detection substrate 110 and the readout substrate 120 are flip-chip connected by the plurality of bumps 130.

[0017] The first substrate 111 is a substrate made of a compound semiconductor such as gallium arsenide (GaAs). A plurality of infrared detection elements 113 are formed in a lattice pattern on the first substrate 111. FIG. 1 shows a lattice (dashed line) connecting the central positions (also called lattice points) of the plurality of infrared detection elements 113 constituting the infrared sensor 100. Note that the first substrate 111 may be a substrate made of a material other than GaAs as long as the infrared detection elements 113 can be formed. For example, the first substrate 111 may be a substrate made of a compound semiconductor such as gallium nitride (GaN) or indium phosphide (InP). The first substrate 111 is flip-chip connected to the second substrate 121 via a plurality of bumps 130. In order to prevent infrared light reception loss, the first substrate 111 is preferably polished as thin as possible. Therefore, the first substrate 111 has less mechanical strength than the second substrate 121.

[0018] The plurality of infrared detection elements 113 constitute a plurality of pixels. Each of the plurality of infrared detection elements 113 converts the received infrared light into an electrical signal. The electrical signals converted by each of the plurality of infrared detection elements 113 are read out by the readout circuit 123 of the readout substrate 120 via the bumps 130.

[0019] Each of the plurality of first terminals 115 is arranged in association with one of the plurality of infrared detection elements 113. For example, each of the plurality of first terminals 115 is mainly composed of a highly conductive metal such as copper (Cu) plated with gold (Au) on the surface. Each of the plurality of first terminals 115 is connected to a bump 130. Each of the plurality of first terminals 115 is electrically connected to the corresponding second terminal 125 via the bump 130.

[0020] In the present embodiment, an example is shown in which a plurality of infrared detection elements 113 form an m-row × n-column grid (m and n are even natural numbers). FIG. 2 shows an example where m and n are even, but m and n may be odd. For example, a plurality of infrared detection elements 113 form pixels of 256×320 or 480×640. For example, if an infrared detection element 113 of one pixel is a square of about 30 micrometers, the size of the infrared sensor 100 with 256×320 pixels is about 1 centimeter square. Note that the number of pixels formed by the plurality of infrared detection elements 113 may be other than 256×320 or 480×640. Usually, ground electrodes are arranged in the peripheral portion of the infrared sensor 100. For example, the bumps 130 at the outermost grid points not associated with the infrared detection elements 113 may be displaced, and the bumps 130 associated with the infrared detection elements 113 may be arranged in the normal arrangement.

[0021] The second substrate 121 is a substrate made of silicon (Si). Therefore, the second substrate 121 has a different coefficient of thermal expansion from the first substrate 111. A readout circuit 123 is formed on the second substrate 121. Note that the second substrate 121 may be a substrate made of a material other than Si as long as the readout circuit 123 can be formed.

[0022] The readout circuit 123 is a circuit for detecting infrared rays received by each of a plurality of infrared detection elements 113 formed on the detection substrate 110. For example, the readout circuit 123 is realized by a CMOS (Complementary Metal Oxide Semiconductor) circuit formed on a silicon wafer. The readout circuit 123 reads an electrical signal from each of the plurality of infrared detection elements 113. The electrical signals read out by the readout circuit 123 from each of the plurality of infrared detection elements 113 are converted into image data.

[0023] Each of the plurality of second terminals 125 is arranged in association with one of the plurality of first terminals. For example, each of the plurality of second terminals 125 is mainly composed of a highly conductive metal such as copper (Cu) plated with gold (Au) on the surface. Each of the plurality of second terminals 125 is connected to the bump 130. Each of the plurality of second terminals 125 is electrically connected to the corresponding first terminal 115 via the bump 130.

[0024] Each of the plurality of bumps 130 is arranged in association with one of the plurality of infrared detection elements 113. Each of the plurality of bumps 130 electrically connects one-to-one the first terminal 115 associated with each of the plurality of infrared detection elements 113 and the second terminal 125 associated with the first terminal 115. The shape and size of the plurality of bumps 130 are preferably uniform. Usually, the shape and size of the plurality of bumps 130 include manufacturing errors. Note that the shape and size of the plurality of bumps 130 may be different to such an extent that there is no problem with mechanical / electrical connection. For example, the arrangement of the bumps 130 can be specified by polishing the infrared sensor 100 to cut out the bumps or by inspecting the infrared sensor 100 with an X-ray camera.

[0025] The bump 130 is mainly composed of a low melting point metal such as indium (In). Additives other than In may be mixed in the bump 130. The material of the bump 130 is not limited to In as long as the detection substrate 110 and the readout substrate 120 can be flip-chip connected. When the bump 130 is mainly composed of a soft metal such as In, the stress caused by the difference in the thermal expansion coefficients between the first substrate 111 and the second substrate 121 is relaxed due to the deformation of the bump 130. For example, the bump 130 is formed on the surface of the first terminal 115 or the second terminal 125 by plating or electron gun evaporation through a mask with an open arrangement pattern. The bump 130 is cylindrical when formed on the surface of the first terminal 115 or the second terminal 125, and is melted by wet back and formed into a spherical shape.

[0026] When the detection substrate 110 and the readout substrate 120 are flip-chip connected, a gap is formed between the plurality of bumps 130. Note that the bump 130 may be formed on the surface of the second terminal 125 of the readout substrate 120. Also, the bump 130 may be a combination of a bump formed on the surface of the first terminal 115 of the detection substrate 110 and a bump formed on the surface of the second terminal 125 of the readout substrate 120 that are melted and integrated.

[0027] Normally, a thermosetting resin is filled as underfill in the gap formed by the plurality of bumps 130. In order to facilitate the flow of the underfill between adjacent bumps 130, a gap with a vertical-to-horizontal ratio of 1:1 is formed when viewed from the side direction. For example, the underfill is poured into the gap between the plurality of bumps 130 in a vacuum state. Note that in this embodiment, the underfill is not shown in order to simplify the description.

[0028] Among the plurality of bumps 130, the bumps 130 forming at least one row and one column are arranged with their centers shifted from the lattice points of the lattice formed by the plurality of infrared detection elements 113. The bumps 130 arranged with their centers shifted from the lattice points are arranged so as not to contact the adjacent bumps 130 when they reach the maximum width in top view during the manufacturing process. The bumps 130 arranged with their centers shifted from the lattice points are arranged such that their ends are located in the gap between the adjacent first terminals 115 and second terminals 125. The bumps 130 arranged with their centers shifted from the lattice points are arranged at positions where they are not in electrical contact with the first terminal 115, the second terminal 125, and the bumps 130 associated with the adjacent lattice points.

[0029] For example, the bumps 130 are arranged with their centers shifted from the center of the pixel within a range of not less than 10% and not more than 50% of the pitch size of the pixels of the infrared detection elements 113. If the shift from the center of the pixel is less than 10%, the effect of relaxing the stress applied to the gap between the bumps 130 is small. If the shift from the center of the pixel exceeds 50%, it becomes difficult to form the wiring inside the first substrate 111 or the second substrate 121. Also, if the shift from the center of the pixel exceeds 50%, the adjacent bumps 130 are likely to contact each other.

[0030] In the example of FIG. 1, the bumps 130 in the fourth row and the fourth column are arranged with their centers shifted from the lattice points. One end of the bumps 130 in the fourth row and the fourth column is located in the gap between the adjacent first terminals 115 (second terminals 125). If the plurality of bumps 130 are arranged as shown in FIG. 1, for all rows and columns, the ends of any of the bumps 130 will be located on the line of the gap between any of the electrodes (first terminal 115 / second terminal 125) associated with the plurality of infrared detection elements 113. For example, on the line A of the gap between the electrodes in the fourth row and the electrodes in the fifth row, the bump 130 in the fourth column of the fifth row is located. For example, on the line B of the gap between the electrodes in the third column and the electrodes in the fourth column, the bump 130 in the fourth column of the fourth row is located.

[0031] In the first substrate 111, the position of the gap between the plurality of first terminals 115 has a lower mechanical strength than the position where the first terminals 115 reinforced by the bumps 130 are formed. Therefore, if there is nothing at the position of the gap between the plurality of first terminals 115, the stress caused by the warping that occurs when the infrared sensor 100 is cooled may be directly applied to the gap, and cracks may occur in a straight line. If at least one of the bumps 130 is located on the line of the gap between the plurality of electrodes, the stress caused by the warping that occurs when the infrared sensor 100 is cooled is relaxed by the bumps 130 arranged in the gap. As a result, the first substrate 111 becomes less likely to deform along the row direction and the column direction of the lattice formed by the plurality of infrared detection elements 113. Therefore, the stress applied to the gap between the plurality of electrodes is relaxed, and warping and cracks are less likely to occur in the detection substrate 110, which has relatively lower strength compared to the readout substrate 120.

[0032] 〔Related Art〕 Next, an example of a related-art infrared sensor will be described. In the related-art infrared sensor, a plurality of bumps are arranged at the lattice point positions of the lattice formed by the plurality of infrared detection elements 113. FIGS. 5 and 6 are conceptual diagrams for explaining an example of the related-art infrared sensor 500. FIG. 5 is a plan view of the infrared sensor 500. FIG. 6 is a side view when the lower side surface of the infrared sensor 100 in FIG. 5 is viewed.

[0033] The infrared sensor 500 includes a detection substrate 510, a readout substrate 520, and a plurality of bumps 530. The detection substrate 510 has a first substrate 511, a plurality of infrared detection elements 513, and a plurality of first terminals 515. The readout substrate 520 has a second substrate 521, a readout circuit 523, and a plurality of second terminals 525. Each of the plurality of first terminals 515 is associated with one of the plurality of second terminals 525. Each of the plurality of first terminals 515 is connected to the corresponding second terminal 525 via a bump 530. The infrared sensor 500 has a structure in which the detection substrate 510 and the readout substrate 520 are flip-chip connected by the plurality of bumps 530.

[0034] In the first substrate 511, the position of the gap between the plurality of first terminals 515 has a lower mechanical strength than the position where the first terminals 515 are formed. Therefore, the stress caused by the warping that occurs when the infrared sensor 500 is cooled is directly applied to the position of the gap between the plurality of first terminals 515. As a result, due to the stress applied to the gap between the plurality of electrodes, the detection substrate 510, which has relatively lower strength compared to the readout substrate 520, is likely to warp or crack.

[0035] 〔Modification Example 1〕 Next, an example of the infrared sensor of Modification Example 1 will be described. The infrared sensor of this modification example is an example in which all of the plurality of bumps 130 are displaced and arranged. FIGS. 7 and 8 are conceptual diagrams for explaining an example of the infrared sensor 100-1 of this modification example. FIG. 7 is a plan view when the detection substrate 110 is removed. FIG. 8 is a side view when the lower side surface of the infrared sensor 100-1 in FIG. 7 is viewed.

[0036] In this modification example, the bumps 130 in the odd-numbered rows are displaced in the upper right direction of the electrodes (second terminals 125), and the bumps 130 in the even-numbered rows are displaced in the upper left direction of the electrodes (second terminals 125). Note that this modification example is just an example, and no particular limitation is imposed on the direction, position, etc. of displacing the bumps 130. In this modification example, the bumps 130 are displaced in a regular manner, but the bumps 130 may be displaced randomly.

[0037] In this modified example, a plurality of bumps 130 belonging to adjacent rows and columns are shifted in opposite directions from each other. Therefore, in the infrared sensor 100-1 of this modified example, the plurality of bumps 130 are located in all the gaps between the electrodes. For example, all the bumps 130 in the fifth row are located on line A in the gap between the electrodes in the fourth row and the electrodes in the fifth row. For example, all the bumps 130 in the third column and the fourth column are located on line B in the gap between the electrodes in the third column and the electrodes in the fourth column. Compared with the infrared sensors 100 in FIGS. 1 to 4, the infrared sensor 100-1 of this modified example has a larger number of bumps 130 located in the gaps between the electrodes. Therefore, according to the infrared sensor 100-1 of this modified example, compared with the infrared sensors 100 in FIGS. 1 to 4, it is less likely to be deformed along the row direction and the column direction of the infrared sensor 100.

[0038] 〔Modified Example 2〕 Next, an example of the infrared sensor of Modified Example 2 will be described. The infrared sensor of this modified example is an example in which all of the plurality of bumps 130 are shifted and arranged in the row direction. FIG. 9 is a conceptual diagram for explaining an example of the infrared sensor of this modified example. FIG. 9 is a plan view when the detection substrate 110 is removed.

[0039] In this modified example, the bumps 130 in the odd-numbered rows are shifted to the right (+x) with respect to the electrodes (second terminals 125), and the bumps 130 in the even-numbered rows are shifted to the left (-x) with respect to the electrodes (second terminals 125). Note that this modified example is just an example, and there are no particular limitations on the direction and position of shifting the bumps 130, etc.

[0040] In this modified example, a plurality of bumps 130 belonging to adjacent rows are shifted in opposite directions along the row direction (x direction). Therefore, in the infrared sensor of this modified example, the bumps 130 are located in all the gaps between the electrodes adjacent in the row direction (x direction). For example, there are no bumps 130 on line A in the gap between the electrodes in the fourth row and the electrodes in the fifth row. On the other hand, for example, some bumps 130 in the third column and the fourth column are located on line B in the gap between the electrodes in the third column and the electrodes in the fourth column. Compared with the infrared sensor 100-1 of Modified Example 1, the infrared sensor of this modified example has fewer bumps 130 located in the gaps between the electrodes. For example, in an infrared detection element such as a line sensor where the ratio of the length in the longitudinal direction (also called the first direction) to the length in the short direction (also called the second direction) is large, warping in the longitudinal direction is likely to occur. Therefore, when there is a difference in the lengths in the longitudinal direction and the short direction, a relatively large stress is likely to be applied along the short direction, and it is likely to crack along the short direction. In such a case, if a part of the bumps 130 is located in the gap between the electrodes arranged along the longitudinal direction, warping in the longitudinal direction is less likely to occur.

[0041] [Modified Example 3] Next, an example of the infrared sensor of Modified Example 3 will be described. The infrared sensor of this modified example is an example in which the shapes of at least some of the electrodes (the first terminal 115 and the second terminal 125) are deformed. FIG. 10 is a conceptual diagram for explaining an example of the infrared sensor of this modified example. FIG. 10 is a plan view when the detection substrate 110 is removed. In the following, it is assumed that the first terminal 115 associated with the deformed second terminal 125 is also deformed in the same manner as the associated second terminal 125.

[0042] In this modification example, the second terminal 125 in the even rows is deformed so that the bumps 130 in the even rows are arranged with a large shift to the right (+x) or left (-x). In the example of FIG. 10, the right side of the second terminal 125 in the second row is deformed into a shape in which a semicircle protrudes. Also, the left side of the second terminal 125 in the 2nd to nth columns in the second row is deformed into a shape with a notch avoiding the semicircle protruding from the second terminal 125 adjacent to the left. Also, the left side of the second terminal 125 in the fourth row is deformed into a shape in which a semicircle protrudes. Also, the right side of the second terminal 125 in the 1st to n-1th columns in the fourth row is deformed into a shape with a notch avoiding the semicircle protruding from the second terminal 125 adjacent to the right. The bump 130 is arranged on the protruding semicircle. Note that this modification example is just an example, and there is no particular limitation on the shape of the second terminal 125, the position where the bump 130 is arranged, etc. Also, not only the even rows but also the second terminals 125 in the odd rows may be deformed. Also, not only in the row direction but also in the column direction, the second terminal 125 may be deformed.

[0043] In this modification example, by deforming the electrodes, a part of the electrode is located on the line of the gap between the electrodes. Then, bumps are arranged on the electrodes located on the line of the gap between the electrodes. Therefore, in the plurality of bumps 130 of the infrared sensor of this modification example, the electrodes and the bumps 130 are located in the gap between the electrodes. For example, on the line B of the gap between the electrode in the third column and the electrode in the fourth column, the second terminals 125 and the bumps 130 in the second row and third column, the fourth row and fourth column, and the nth row and third column are located. Compared with Modification Example 1 and 2, in this modification example, deformation along the gap between the electrodes is less likely to occur by the amount that the electrodes and the bumps are located in the gap between the electrodes.

[0044] As described above, the infrared sensor of this embodiment includes a detection substrate, a readout substrate, and a plurality of bumps. The detection substrate includes a first substrate on which a plurality of infrared detection elements are arranged in a lattice pattern, and a plurality of first terminals associated with each of the infrared detection elements are arranged. The readout substrate includes a second substrate on which a plurality of second terminals associated with each of the plurality of first terminals are arranged, and a readout circuit for reading an electrical signal based on infrared rays detected by each of the plurality of infrared detection elements is formed. The plurality of bumps electrically connect each of the plurality of first terminals and the plurality of second terminals associated with each of the plurality of first terminals. At least a part of any one of the plurality of first terminals, the plurality of second terminals, and the plurality of bumps is arranged at a position between adjacent infrared detection elements in a top view.

[0045] In this embodiment, in a top view, at least a part of any one of the plurality of bumps is arranged at a position between adjacent infrared detection elements. Therefore, according to this embodiment, warping of the substrate on which the infrared detection elements are formed can be reduced.

[0046] In one aspect of this embodiment, at least a part of any one of the plurality of bumps is arranged at a position of a gap formed between the plurality of first terminals and the plurality of second terminals. For example, at least any one of the plurality of bumps is arranged offset from the center of the plurality of infrared sensors within a range of 10% or more and 50% or less of the pitch size of the plurality of infrared sensors. For example, when the first substrate and the second substrate are rectangular, at least any one of the plurality of bumps is arranged offset along the longitudinal direction of the first substrate and the second substrate. For example, all of the plurality of bumps are arranged at a position of a gap formed between the plurality of first terminals and the plurality of second terminals. For example, the plurality of first terminals and the plurality of second terminals are deformed in accordance with the displacement of the plurality of bumps.

[0047] According to this aspect, it becomes difficult to deform along the row direction and the column direction of the lattice formed by a plurality of infrared detection elements. Therefore, the stress applied to the gaps between the plurality of electrodes is relaxed, and it becomes difficult for the detection substrate, which has relatively low strength compared to the readout substrate, to warp or crack.

[0048] Normally, a quantum infrared detector is used at liquid helium temperature (4.2 Kelvin) or liquid nitrogen temperature (77 Kelvin). Therefore, when using a quantum infrared detector, warping occurs in the chips constituting the infrared sensor due to the difference in the coefficient of thermal expansion of the flip-chip connected substrates. When warping occurs in the chips, the detection substrate, which is relatively weak in strength, becomes easily cracked. Cracking of the detection substrate (also called chip cracking) leads to a decrease in the operability of the quantum infrared detector. For example, when imaging infrared rays detected by a plurality of infrared detection elements arranged in a lattice pattern, variations in sensitivity and bad pixels of each element are corrected. When chip cracking occurs, streaks caused by the chip cracking appear in the image. Since the streaks caused by chip cracking cannot be completely eliminated even with correction, they become a factor in reducing the sharpness of the image.

[0049] In this embodiment, by deliberately shifting the arrangement of the plurality of bumps from an orderly lattice pattern, a linearly mechanically weak location that crosses the chip is eliminated, and the mechanical strength of the entire chip is increased. As a result, chip cracking can be prevented and the operability is improved.

[0050] For example, a GaAs substrate used for the detection substrate has a plane orientation that is prone to cracking. The GaAs substrate is prone to cracking in a direction parallel / perpendicular to a notch (also called an orihira) of a straight line indicating the direction of the crystal axis (plane orientation). For example, when a plurality of bumps are arranged along a direction oblique to the crystal axis as in the related art, the substrate can be made less likely to crack in the direction along the matrix of pixels. However, even in such a case, it remains true that the substrate is prone to cracking along the crystal axis. According to this embodiment, even in such a case, chip cracking can be prevented.

[0051] (Second Embodiment) Next, an infrared sensor according to the second embodiment will be described with reference to the drawings. The infrared sensor of this embodiment is different from the first embodiment in that electrodes associated with a plurality of infrared detection elements are shifted from the centers (lattice points) of the plurality of infrared detection elements.

[0052] FIGS. 11 to 13 are conceptual diagrams for explaining the structure of the infrared sensor 200 of this embodiment. FIG. 11 is a plan view of the infrared sensor 200. FIG. 12 is a side view when looking at the lower side surface of the infrared sensor 200 of FIG. 11. FIG. 13 is a plan view when a detection substrate 210 described later is removed. In FIG. 11, the positions of electrodes (first terminals 215) of the detection substrate 210 described later, electrodes (second terminals 225) of the readout substrate 220, and bumps 230 are indicated by broken lines. In FIGS. 12 and 13, for ease of understanding, a plurality of bumps 230 constituting adjacent rows are indicated by different hatchings.

[0053] The infrared sensor 200 includes a detection substrate 210, a readout substrate 220, and a plurality of bumps 230. The detection substrate 210 has a first substrate 211, a plurality of infrared detection elements 213, and a plurality of first terminals 215. The readout substrate 220 has a second substrate 221, a readout circuit 223, and a plurality of second terminals 225. Each of the plurality of first terminals 215 is associated with one of the plurality of second terminals 225. Each of the plurality of first terminals 215 is connected to the corresponding second terminal 225 via a bump 230. The infrared sensor 200 has a structure in which the detection substrate 210 and the readout substrate 220 are flip-chip connected by a plurality of bumps 230. The infrared sensor 200 is the same as the infrared sensor 100 of the first embodiment except for the arrangement of the first substrate 211, the second substrate 221, and the bump 130. Therefore, hereinafter, descriptions of the same parts as those of the infrared sensor 100 will be omitted. Hereinafter, regarding the arrangement of the electrodes (first terminals 215, second terminals 225), mainly FIG. 13 (second terminals 225) will be used for explanation.

[0054] At least any one of the plurality of second terminals 225 is arranged to be shifted from directly below the plurality of infrared detection elements 213 so as to be located on a line between the plurality of infrared detection elements 213 in a top view. The second terminal 225 arranged to be shifted is arranged at a position where it does not come into electrical contact with an adjacent second terminal 225. For example, if the mask used when forming the second terminal 225 on the surface of the second substrate 221 is changed, the arrangement of the second terminal 225 can be changed, so that a new process does not need to be added in manufacturing. Regarding the first terminal 215 as well, the arrangement can be changed by changing the mask, similarly to the second terminal 225.

[0055] In the case of the example of FIG. 13, a part of the second terminals 225 at the first column, the third column, and the fifth column of the fifth row is located on A between the infrared detection elements 213 in the fourth row and the infrared detection elements 213 in the fifth row. Also, a part of the second terminals 225 at the third column of the first row, the fourth column of the second row, the third column of the third row, the fourth column of the fourth row, the third column of the fifth row, and the fourth column of the m-th row is located on line B between the infrared detection elements 213 in the third column and the infrared detection elements 213 in the fourth column.

[0056] In the infrared sensor 200, in a top view, at least any one of the electrodes (the first terminal 215, the second terminal 225) is located between the plurality of infrared detection elements 213 for all rows and columns. Therefore, in the infrared sensor 200, compared with the case where a plurality of electrodes are arranged neatly in a grid pattern directly below the plurality of infrared detection elements 213, the mechanical strength between the plurality of infrared detection elements 213 is high. As a result, the first substrate 211 is less likely to be deformed along the row direction and the column direction of the grid formed by the plurality of infrared detection elements 213. Therefore, the stress applied between the plurality of infrared detection elements 213 is relaxed, and it is less likely that warping or cracks occur in the detection substrate 210, which has relatively low strength compared to the readout substrate 220.

[0057] 〔Modification Example 4〕 Next, an example of the infrared sensor of Modification 4 will be described. The infrared sensor of this modification is an example in which a plurality of bumps 230 are arranged with a shift in addition to a plurality of electrodes (the first terminal 215 and the second terminal 225). FIGS. 14 and 15 are conceptual diagrams for explaining an example of the infrared sensor 200-4 of this modification. FIG. 14 is a plan view when the detection substrate 210 is removed. FIG. 15 is a side view when the lower side surface of the infrared sensor 200-4 in FIG. 14 is viewed.

[0058] In this modification, the bumps 230 in the odd-numbered rows are shifted in the upper right direction of the electrode (the second terminal 225), and the bumps 230 in the even-numbered rows are shifted in the upper left direction of the electrode (the second terminal 225). Note that this modification is just an example, and there is no particular limitation on the direction and position of shifting the bumps 230, etc. In this modification, the bumps 230 are shifted with regularity, but the bumps 230 may be shifted randomly.

[0059] In this modification, a plurality of bumps 230 belonging to adjacent rows and columns are shifted in opposite directions along the row direction. Therefore, the plurality of bumps 230 of the infrared sensor 200-4 of this modification are located on the line between the plurality of infrared detection elements 213. For example, on line A between the infrared detection element 213 in the 4th row and the infrared detection element 213 in the 5th row, the bumps 230 in the 1st column, 3rd column, and 5th column of the 5th row are located. For example, on line B between the infrared detection element 213 in the 3rd column and the infrared detection element 213 in the 4th column, the bumps 230 in the 3rd column of the 1st row, 4th column of the 2nd row, 3rd column of the 3rd row, 4th column of the 4th row, 3rd column of the 5th row, and 4th column of the mth row are located. Thus, in the infrared sensor 200-4 of this modification, in a top view, the bumps 230 are located on the line between the plurality of infrared detection elements 213. Therefore, compared with the infrared sensor 200 in FIGS. 11 to 13, the infrared sensor 200-4 of this modification is less likely to be deformed along the row direction and the column direction.

[0060] 〔Modification 5〕 Next, an example of the infrared sensor of Modification 5 will be described. The infrared sensor of this modification is an example in which the shapes of a plurality of electrodes (the first terminal 215 and the second terminal 225) are deformed. FIG. 16 is a conceptual diagram for explaining an example of the infrared sensor of this modification. FIG. 16 is a plan view when the detection substrate 210 is removed. The infrared sensor of this modification has the same configuration as the infrared sensor 200 of the second embodiment, but some configurations are not shown and the reference numerals are used in a diverted manner.

[0061] In this modification, at least any one of a plurality of second terminals 225-5 with rounded corners is displaced from directly below the plurality of infrared detection elements 213 so as to be located on the line between the plurality of infrared detection elements 213 in a top view. Although not shown, the corners of the plurality of first terminals arranged on the first substrate 211 are also rounded in the same manner as the second terminals 225-5. Note that the shape of the corners of the second terminals 225-5 is not limited as long as they are deformed so as not to be in electrical contact with other adjacent second terminals 225-5.

[0062] In the infrared sensor of this modification, the electrodes (the first terminal 215 and the second terminal 225) can be displaced more greatly than the infrared sensor 200 of the second embodiment by the amount of rounding of the corners. For example, in the infrared sensor 200 of the second embodiment, in a top view, the bumps 230 in the second column, the fourth column, and the nth column could not be positioned on the line A between the infrared detection elements 213 in the fourth row and the infrared detection elements 213 in the fifth row. On the other hand, in the infrared sensor of this modification, in a top view, the bumps 230 in the first column of the fifth row, the second column of the fourth row, the third column of the fifth row, the fourth column of the fourth row, the fifth column of the fifth row, and the nth column of the fourth row are positioned on the line A between the infrared detection elements 213 in the fourth row and the infrared detection elements 213 in the fifth row. Thus, in the infrared sensor of this modification, the electrodes can be displaced more greatly than in the second embodiment. Therefore, compared with the infrared sensor 200 of the second embodiment, the infrared sensor of this modification is less likely to be deformed along the row direction and the column direction.

[0063] 〔Modification 6〕 Next, an example of the infrared sensor of Modification 6 will be described. The infrared sensor of this modification is an example in which all of a plurality of electrodes (the first terminal 215 and the second terminal 225) are arranged with a shift in the row direction. FIG. 17 is a conceptual diagram for explaining an example of the infrared sensor of this modification. FIG. 17 is a plan view when the detection substrate 210 is removed. The infrared sensor of this modification has the same configuration as the infrared sensor 200 of the second embodiment, but some configurations are not shown and the reference numerals are reused.

[0064] In this modification, the electrodes (the second terminal 225) in the odd-numbered rows are shifted to the right (+x), and the electrodes (the second terminal 225) in the even-numbered rows are shifted to the left (-x). Note that this modification is just an example, and there is no particular limitation on the direction and position of shifting the electrodes (the second terminal 225), etc. Also, although not shown, the first terminal 215 is also shifted corresponding to the second terminal 225.

[0065] In this modification, a plurality of electrodes belonging to adjacent rows are shifted in opposite directions along the row direction (x direction). Therefore, in the infrared sensor of this modification, electrodes are located at all positions between the adjacent infrared detection elements 213 in the row direction (x direction). For example, in a top view, there are no electrodes on line A between the infrared detection elements 213 in the fourth row and the infrared detection elements 213 in the fifth row. On the other hand, for example, in a top view, on line B between the electrodes in the third column and the electrodes in the fourth column, either the electrodes in the third column or the fourth column are located. Compared with the infrared sensor 200 of the second embodiment, the infrared sensor of this modification has fewer electrodes located between the plurality of infrared detection elements 213 in a top view. For example, in an infrared detection element with a large ratio of the length in the longitudinal direction (also called the first direction) to the length in the short transverse direction (also called the second direction) like a line sensor, warping in the longitudinal direction is likely to occur. Therefore, when there is a difference in the lengths of the longitudinal direction and the short transverse direction, relatively large stress is likely to be applied along the short transverse direction, and it is likely to crack along the short transverse direction. In such a case, if electrodes are located between the infrared detection elements 213 arranged along the longitudinal direction in a top view, warping in the longitudinal direction is less likely to occur.

[0066] As described above, the infrared sensor of the present embodiment includes a detection substrate, a readout substrate, and a plurality of bumps. The detection substrate includes a first substrate on which a plurality of infrared detection elements are arranged in a lattice pattern and a plurality of first terminals associated with each of the infrared detection elements are arranged. The readout substrate includes a second substrate on which a plurality of second terminals associated with each of the plurality of first terminals are arranged and a readout circuit for reading an electrical signal based on infrared rays detected by each of the plurality of infrared detection elements is formed. The plurality of bumps electrically connect each of the plurality of first terminals and the plurality of second terminals associated with each of the plurality of first terminals. At least a part of any one of the plurality of first terminals, the plurality of second terminals, and the plurality of bumps is arranged at a position between adjacent infrared detection elements in a top view.

[0067] In the present embodiment, at least a part of any one of the plurality of first terminals and the plurality of second terminals is arranged at a position between adjacent infrared detection elements in a top view. Therefore, according to the present embodiment, warping of the substrate on which the infrared detection elements are formed can be reduced.

[0068] In one aspect of the present embodiment, at least one set of a plurality of first terminals and a plurality of second terminals associated with each other is arranged at a position between adjacent infrared detection elements in a top view. For example, the corners of the plurality of first terminals and the plurality of second terminals are deformed so as not to be in electrical contact with adjacent plurality of first terminals and plurality of second terminals. For example, the first substrate and the second substrate are rectangular, and at least one set of a plurality of first terminals and a plurality of second terminals associated with each other is arranged offset along the longitudinal direction of the first substrate and the second substrate.

[0069] According to this aspect, the first substrate is less likely to be deformed along at least one of the row direction and the column direction of the lattice formed by the plurality of infrared detection elements. Therefore, the stress applied between the plurality of infrared detection elements is relaxed, and warping and cracks are less likely to occur in the detection substrate having relatively low strength compared to the readout substrate.

[0070] (Third Embodiment) Next, an imaging device according to the third embodiment will be described with reference to the drawings. The imaging device of this embodiment includes the infrared sensor of the first or second embodiment. FIG. 18 is a conceptual diagram showing an example of the configuration of the imaging device 30 of this embodiment. The imaging device 30 includes an infrared sensor 300, a lens 31, a cooler 33, and a controller 35.

[0071] The infrared sensor 300 has the same configuration as the infrared sensor 100 of the first embodiment and the infrared sensor 200 of the second embodiment. The infrared sensor 300 outputs an electrical signal based on the received infrared rays to the controller 35 in accordance with the control of the controller 35. The electrical signal output to the controller 35 is converted into image data corresponding to the light reception by a plurality of infrared light receiving elements included in the infrared sensor 300. For example, the infrared sensor 300 is hermetically sealed by a sealing member having a window that transmits infrared rays. For example, a material similar to the lens 31 described later can be used for the window portion provided in the sealing member.

[0072] The lens 31 includes a lens 330 that can focus infrared rays in the wavelength band of the detection target. The lens 31 focuses infrared rays in the wavelength band of the detection target on the light receiving surface of the infrared sensor 300. For example, for the lens 31, a lens 330 made of a material such as germanium (Ge), silicon (Si), zinc sulfide (ZnS), zinc selenide (ZnSe), sapphire (Al2O3), etc. can be used. For example, for the lens 31, a lens 330 made of a material such as barium fluoride (BaF2), calcium fluoride (CaF2), lithium fluoride (LiF), chalcogenide glass, etc. can be used. It is only necessary to use a lens 330 that can focus infrared rays in the wavelength band of the detection target for the lens 31. For example, the lens 31 is equipped with an autofocus function and focuses on the light receiving surface of the infrared sensor 300 in accordance with the control of the controller 35.

[0073] The cooler 33 is a device for cooling the infrared sensor 300. In Fig. 18, the infrared sensor 300 is in contact with the cooler 33. For quantum infrared sensors, a cooler 33 is necessary to eliminate the influence of noise caused by dark current and the like. For example, the cooler 33 cools the infrared sensor 300 so that the temperature is within a range of about 60 to 250 Kelvin. For example, as the cooler 33, a cooler having a Stirling mechanism or an electronic cooling element utilizing the Peltier effect is used. For example, the cooler 33 cools the infrared sensor 300 to an appropriate temperature according to the control of the controller 35.

[0074] The controller 35 acquires an electrical signal output from the infrared sensor 300 and generates image data corresponding to the light reception of a plurality of infrared light receiving elements included in the infrared sensor 300. Note that the controller 35 may control the lens 31 and the cooler 33. Fig. 19 is a block diagram showing an example of the configuration of the controller 35. The controller 35 includes an imaging control unit 351, an image processing processor 352, an internal memory 353, and an image output unit 354.

[0075] The imaging control unit 351 controls the infrared sensor 300 to image a shooting target range and acquires an electrical signal output from the infrared sensor 300. The imaging control unit 351 converts the acquired electrical signal into image data. The imaging control unit 351 outputs the converted image data to the image processing processor 352. If the image processing processor 352 cannot process all the data at once, the imaging control unit 351 may temporarily store the converted image data in the internal memory 353.

[0076] The image processing processor 352 acquires image data based on the electrical signal output from the infrared sensor 300 from the imaging control unit 351. The image processing processor 352 is an integrated circuit that performs processes such as dark current correction, interpolation calculation, color space conversion, gamma correction, aberration correction, noise reduction, and image compression on the acquired image data. The image processing processor 352 outputs the image data with image processing added to the image output unit 354.

[0077] The internal memory 353 is a storage element that temporarily stores image information that the image processing processor 352 cannot process all at once or processed image information. Note that the internal memory 353 may be configured to temporarily store the electrical signal detected by the infrared sensor 300. The internal memory 353 can be configured by a general memory.

[0078] The image output unit 354 outputs the image data processed by the image processing processor 352. There is no particular limitation on the output destination where the image output unit 354 outputs the image data. For example, the image output unit 354 outputs the image data to a system (not shown) that uses the image data captured by the imaging device 30. For example, the image output unit 354 causes a display (not shown) mounted on the imaging device 30 to display the image data. For example, the image output unit 354 causes a storage device (not shown) mounted on the imaging device 30 to store the image data.

[0079] As described above, the imaging device of the present embodiment includes the infrared sensor of the first or second embodiment, a lens that condenses infrared rays on the light receiving surface of the infrared sensor, a cooler that cools the infrared sensor, and a controller. The controller acquires the electrical signal output from the infrared sensor and generates image data corresponding to the light reception of a plurality of infrared light receiving elements included in the infrared sensor. According to the present embodiment, since cracks are less likely to occur in the detection substrate on which the infrared detection element is formed, a clear image can be stably captured.

[0080] As described above, the present invention has been described with reference to the embodiments, but the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

Explanation of Reference Numerals

[0081] 30 Imaging device 31 Lens 33 Cooler 35 Controller 100, 200, 300 Infrared sensor 110, 210 Detection substrate 111, 211 First substrate 113, 213 Infrared detection element 115, 215 First terminal 120, 220 Readout substrate 121, 221 Second substrate 123, 223 Readout circuit 125, 225 Second terminal 130, 230 Bump

Claims

1. A detection substrate including a first substrate on which a plurality of infrared detection elements are arranged in a grid pattern and a plurality of first terminals associated with each of the infrared detection elements are arranged; A reading substrate including a second substrate on which a plurality of second terminals associated with each of the plurality of first terminals are arranged and a reading circuit for reading an electrical signal based on infrared rays detected by each of the plurality of infrared detection elements is formed; A plurality of bumps for electrically connecting each of the plurality of first terminals and the plurality of second terminals associated with each of the plurality of first terminals; The plurality of first terminals and the plurality of second terminals are arranged in a grid pattern at the same pitch; The first terminal and the second terminal associated with each other are arranged at positions overlapping each other in a top view; An infrared sensor in which at least a part of the centers of at least some of the plurality of first terminals, the plurality of second terminals, and the plurality of bumps are shifted from a straight line formed by a row or a column constituting a matrix formed by the centers of the plurality of first terminals, the plurality of second terminals, and the plurality of bumps other than the part in a top view and are arranged at positions between adjacent infrared detection elements.

2. At least some of the plurality of bumps are The infrared sensor according to claim 1, which is arranged at a position of a gap formed between the plurality of first terminals and the plurality of second terminals.

3. At least some of the plurality of bumps are The infrared sensor according to claim 1 or 2, which is arranged offset from the center of the plurality of infrared detection elements within a range of 10% or more and 50% or less of the pitch size of the plurality of infrared detection elements.

4. The first substrate and the second substrate are rectangular, At least some of the plurality of bumps are The infrared sensor according to claim 2 or 3, which is arranged with a shift along the longitudinal direction of the first substrate and the second substrate.

5. All of the plurality of bumps are The infrared sensor according to any one of claims 2 to 4, which is arranged at a position of a gap formed between the plurality of first terminals and the plurality of second terminals.

6. Among the sets of the plurality of first terminals and the plurality of second terminals associated with each other, at least any one set is The infrared sensor according to any one of claims 1 to 5, which is arranged at a position between the adjacent infrared detection elements in a top view.

7. The infrared sensor according to claim 6, wherein the corners of the plurality of first terminals and the plurality of second terminals are deformed so as not to be in electrical contact with the adjacent plurality of first terminals and the plurality of second terminals.

8. The first substrate and the second substrate are rectangular, Among the sets of the plurality of first terminals and the plurality of second terminals associated with each other, at least any one set is The infrared sensor according to claim 6 or 7, which is arranged with a shift along the longitudinal direction of the first substrate and the second substrate.

9. The infrared sensor according to any one of claims 1 to 8, A lens that condenses infrared rays on a light receiving surface of the infrared sensor, A cooler that cools the infrared sensor, An imaging device comprising a controller that acquires an electrical signal output from the infrared sensor and generates image data corresponding to the light reception of the plurality of infrared detection elements included in the infrared sensor.

Images