A flip-chip interconnect structure of a focal plane detector

Abstract

The present invention relates to the field of optoelectronic technology, and specifically to a flip-chip interconnect structure of a focal plane detector. The interconnect structure includes a readout circuit and a sensitive array, and the readout circuit and the sensitive array are respectively provided with a first pixel interconnect structure and a second pixel interconnect structure, and at least one of the first pixel interconnect structure and the second pixel interconnect structure is an elastic interconnect structure with telescopic deformation performance. The interconnect structure with telescopic deformation performance adopts conventional metal as the main body, and there is no problem of particle morphology. The preparation size is easier to control and is more suitable for the small-size high-precision interconnection needs of small pixels. It can avoid the adjacent pixels from short-circuiting when the reverse solder interconnection is not leveled enough to generate overvoltage; this interconnect structure ensures the directionality of deformation, and can avoid the problem of adjacent indium bumps being connected due to local overvoltage when the sensitive array and the readout circuit are not parallel in traditional technology.

Description

Technical Field

[0001] The invention relates to the field of optoelectronic technology, in particular to a flip-chip interconnection structure of a focal plane detector. Background Art

[0002] At present, the existing cooling infrared focal plane chip uses indium bumps as the interconnection structure to interconnect the readout circuit and the sensitive array with reverse soldering, see the attached Figure 1 As shown in the figure. Since metal indium is relatively soft and easy to deform at room temperature, and two pieces of indium are easy to bond together under pressure, indium metal has always been used to prepare "column-shaped" or "cone-shaped" indium interconnect bumps through photolithography and coating to achieve reverse soldering interconnection of cooling infrared chips.

[0003] As focal plane infrared detectors develop towards large arrays and small pixels, the size of interconnect bumps is getting smaller and smaller, and the aspect ratio is getting higher and higher. Under this circumstance, traditional indium interconnect bumps have the following shortcomings, see the attached Figure 2 As shown:

[0004] 1. As the pixel size decreases, the diameter of the indium bumps becomes smaller and smaller; due to the large indium metal grains, the uniformity of small-sized indium bumps is very poor, which seriously affects the efficiency of interconnection and becomes a bottleneck in the development of small pixel technology;

[0005] 2. As the pixel size decreases and the specifications increase, the consistency of the solder connection in the entire array area is very high. Slight leveling, particle contamination, unevenness and other problems may cause local overvoltage. In the case of overvoltage, the indium bump will become thicker laterally and connect with the indium bump of the adjacent pixel, thus forming a large area of ​​regional bad pixels.

[0006] Therefore, there is a need for a solution to solve the problems in the prior art. Summary of the invention

[0007] To solve the above technical problems, according to one aspect of the present invention, the present invention provides a technical solution: an interconnect structure with telescopic deformation performance is prepared by using MEMS technology. This interconnect structure will not expand to the surroundings even under overvoltage conditions, which can avoid the problem of adjacent indium bumps being connected due to local overvoltage when the sensitive array and the readout circuit are not parallel in traditional technologies, and can at least solve some of the problems existing in the prior art.

[0008] A flip-chip interconnect structure of a focal plane detector includes a readout circuit and a sensitive array, wherein the readout circuit and the sensitive array are respectively provided with a first pixel interconnect structure and a second pixel interconnect structure, and the characteristic is that at least one of the first pixel interconnect structure and the second pixel interconnect structure is an elastic interconnect structure with telescopic deformation performance.

[0009] As a preferred solution of the flip-chip interconnect structure of a focal plane detector described in the present invention, one of the first pixel interconnect structure and the second pixel interconnect structure is the elastic interconnect structure, and the other is a bump or a pad.

[0010] As a preferred solution of the flip-chip interconnection structure of the focal plane detector described in the present invention, wherein: the first pixel interconnection structure and the second pixel interconnection structure are both the elastic interconnection structure.

[0011] As a preferred solution of the flip-chip interconnection structure of a focal plane detector described in the present invention, each of the elastic interconnection structures includes a contact platform portion and an elastic deformation portion, the contact platform portion and the elastic deformation portion are connected, and the lower end of the elastic deformation portion is electrically connected to a readout circuit or a sensitive array.

[0012] As a preferred solution of the flip-chip interconnect structure of a focal plane detector described in the present invention, the contact platform portion includes a hard metal bottom layer and a contact metal upper layer.

[0013] As a preferred solution of the flip-chip interconnect structure of a focal plane detector described in the present invention, the material of the hard metal bottom layer or the elastic deformation part is Al, Au or Cu.

[0014] As a preferred solution of the flip-chip interconnect structure of a focal plane detector described in the present invention, the hard metal bottom layer and the elastic deformation portion are made of the same material and are integrally formed.

[0015] As a preferred solution of the flip-chip interconnect structure of a focal plane detector described in the present invention, the material of the contact metal upper layer is In, Sn, Au, PbSn, AuSn, CuSn, SnZn or SnAg.

[0016] As a preferred solution of the flip-chip interconnect structure of a focal plane detector described in the present invention, the elastic deformation portion is a multi-segment bending structure or a spiral structure.

[0017] As a preferred solution of the flip-chip interconnection structure of the focal plane detector described in the present invention, wherein: the lateral dimension of the elastic interconnection structure remains unchanged when the longitudinal expansion and contraction deformation occurs.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] (1) The flip-chip interconnect structure of the focal plane detector provided by the present invention is compressed under pressure to adapt to the height difference caused by uneven leveling, thereby ensuring the reliability of the connection of each pixel point, and only deforms in the longitudinal direction but does not produce obvious dimensional expansion in the lateral direction. When the flip-chip interconnection is not leveled enough to generate overpressure, short circuits between adjacent pixels can be avoided.

[0020] (2) The flip-chip interconnect structure of the focal plane detector provided by the present invention has a telescopic deformation performance. The main body of the interconnect structure is made of conventional metal, there is no problem of particle morphology, the preparation size is easier to control, and it is more suitable for the small-size high-precision interconnection needs of small pixels. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0022] Figure 1 It is a schematic diagram of the interconnection structure in the prior art;

[0023] Figure 2 A schematic diagram of the shortcomings of the interconnection structure in the prior art;

[0024] Figure 3 A schematic diagram of a flip-chip interconnect structure of a focal plane detector of the present invention;

[0025] Figure 4 It is a schematic diagram of the assembly of a flip-chip interconnection structure of a focal plane detector of the present invention.

[0026] Description of Figure Numbers:

[0027] 100 readout circuit, 101 circuit end indium bump, 200 sensitive array, 201 array end indium bump, 300 contact platform portion, 301 deformation portion, 400 elastic interconnection structure.

[0028] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0029] The following will be described clearly and completely in conjunction with the technical solutions in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0031] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0032] Example 1

[0033] As attached Figure 3-4 As shown, a flip-chip interconnection structure of a focal plane detector includes a readout circuit 100 and a sensitive array 200. The readout circuit 100 and the sensitive array 200 are respectively provided with a first pixel interconnection structure and a second pixel interconnection structure, and at least one of the first pixel interconnection structure and the second pixel interconnection structure is an elastic interconnection structure 400 with a telescopic deformation performance. When the readout circuit 100 and the sensitive array 200 are flip-chip interconnected, the electrical connection between each detection element of the sensitive array 200 and the corresponding readout circuit 100 is realized through the first pixel interconnection structure and the second pixel interconnection structure.

[0034] The elastic interconnect structure 400 with telescopic deformation capability is prepared by using MEMS technology. This interconnect structure will not expand in all directions even under overvoltage, and can avoid the problem of adjacent indium bumps being connected due to local overvoltage when the sensitive array 200 and the readout circuit 100 are not parallel in the traditional technology.

[0035] Example 2

[0036] As attached Figure 3-4 As shown, a flip-chip interconnect structure of a focal plane detector includes a readout circuit 100 and a sensitive array 200, wherein the readout circuit 100 and the sensitive array 200 are respectively provided with a first pixel interconnect structure and a second pixel interconnect structure, and at least one of the first pixel interconnect structure and the second pixel interconnect structure is an elastic interconnect structure 400 with telescopic deformation performance.

[0037] The structure of the elastic interconnect structure 400 with telescopic deformation capability is specifically defined as follows:

[0038] Each elastic interconnect structure 400 with telescopic deformation capability includes a contact platform portion 300 and an elastic deformation portion 301 , and the lower end of the elastic deformation portion 301 is connected to the readout circuit 100 or the sensitive array 200 .

[0039] The contact platform portion 300 includes a hard metal bottom layer and a contact metal upper layer.

[0040] The elastic deformation part 301 is preferably made of a metal with a certain strength, and the specific material may be Al, Au or Cu, etc. The hard metal bottom layer and the elastic deformation part may be made of the same material and integrally formed. The contact metal upper layer is preferably made of a soft metal, and the specific material may be In, Sn, Au, PbSn, AuSn, CuSn, SnZn or SnAg, etc.

[0041] The elastic deformation part 301 should ensure that its transverse dimension remains basically unchanged when the longitudinal expansion and contraction occurs, and a multi-section bending structure or a spiral structure can be adopted. In this embodiment, a multi-section bending structure is adopted, which specifically includes a first horizontal section, a second bending section and a third bending section. The first horizontal section, the second bending section and the third bending section are arranged in a "Z" shape, and there is an angle between the first horizontal section and the second bending section, and the second bending section and the third bending section are connected to each other. There is an angle between the third bending section and the readout circuit 100 or the sensitive array 200 connected at the lower end. Such an arrangement can ensure that deformation occurs in the longitudinal direction, but no obvious dimensional expansion occurs in the transverse direction.

[0042] The elastic interconnection structure 400 array is distributed between the readout circuit 100 and the sensitive array 200 . The elastic interconnection structure 400 adapts to the height difference caused by uneven leveling through its own compression deformation.

[0043] More specifically, in this embodiment, the elastic interconnection structure 400 is disposed on one side of the readout circuit 100 and the sensitive array 200, and a bump or pad is disposed on the other side, and the bump is generally an indium bump. For example, the elastic interconnection structure 400 is disposed on one side of the readout circuit 100, and a bump or pad is disposed on one side of the sensitive array 200. The position of the elastic interconnection structure 400 can be set according to the pressure bearing capacity.

[0044] By preparing an elastic interconnection structure 400 with deformation capability, the elastic interconnection structure 400 is arranged corresponding to the pixels distributed in the array, so that it is compressed under pressure and deforms only in the longitudinal direction but does not produce obvious dimensional expansion in the transverse direction, which is different from the indium column becoming lower in height and rapidly increasing in diameter when it is compressed. Therefore, when the reverse solder interconnection is not leveled enough to generate overpressure, short circuits between adjacent pixels can be avoided.

[0045] Example 3

[0046] The technical feature different from the second embodiment is that elastic interconnect structures 400 are provided on both sides of the readout circuit 100 and the sensitive array 200 .

[0047] The advantage of such a back-to-back arrangement is that the elastic interconnection structure 400 can adapt to the height difference caused by uneven leveling through its own compression deformation.

[0048] By preparing a deformable elastic interconnection structure 400, it is compressed under pressure and deforms only in the longitudinal direction without significant dimensional expansion in the transverse direction, which is different from the indium column becoming shorter and its diameter increasing rapidly when it is compressed. When the reverse solder interconnection is not leveled enough and overpressure is generated, short circuits between adjacent pixels can be avoided.

[0049] The results of the above embodiments show that the flip-chip interconnect structure of the focal plane detector provided by the present invention adopts micro-electromechanical system (MEMS) technology to prepare an elastic interconnect structure 400 with elastic deformation ability, and distributes the elastic interconnect structure 400 array between the readout circuit 100 and the sensitive array 200. This interconnect structure ensures the directionality of deformation, and can avoid the problem of adjacent indium bumps being connected due to local overvoltage when the sensitive array 200 and the readout circuit 100 are not parallel in traditional technology, thereby effectively solving the technical problems in the background technology.

[0050] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A flip-chip interconnect structure of a focal plane detector, comprising a readout circuit and a sensitive array, wherein the readout circuit and the sensitive array are respectively provided with a first pixel interconnect structure and a second pixel interconnect structure, characterized in that: At least one of the first pixel interconnection structure and the second pixel interconnection structure is an elastic interconnection structure with telescopic deformation performance; when the elastic interconnection structure undergoes longitudinal telescopic deformation, its lateral dimension remains unchanged.

2. The flip-chip interconnect structure of a focal plane detector according to claim 1, characterized in that: One of the first pixel interconnection structure and the second pixel interconnection structure is the elastic interconnection structure, and the other is a bump or a pad.

3. The flip-chip interconnect structure of a focal plane detector according to claim 1, characterized in that: The first pixel interconnection structure and the second pixel interconnection structure are both the elastic interconnection structures.

4. The flip-chip interconnect structure of a focal plane detector according to claim 1, characterized in that: Each of the elastic interconnect structures comprises a contact platform portion and an elastic deformation portion, wherein the contact platform portion and the elastic deformation portion are connected, and the lower end of the elastic deformation portion is electrically connected to a readout circuit or a sensitive array.

5. The flip-chip interconnect structure of a focal plane detector according to claim 4, characterized in that: The contact platform portion includes a hard metal bottom layer and a contact metal upper layer.

6. The flip-chip interconnect structure of a focal plane detector according to claim 5, characterized in that: The material of the hard metal bottom layer or the elastic deformation part is Al, Au or Cu.

7. The flip-chip interconnect structure of a focal plane detector according to claim 5, characterized in that: The hard metal bottom layer and the elastic deformation portion are made of the same material and are integrally formed.

8. The flip-chip interconnect structure of a focal plane detector according to claim 5, characterized in that: The material of the contact metal upper layer is In, Sn, Au, PbSn, AuSn, CuSn, SnZn or SnAg.

9. The flip-chip interconnect structure of a focal plane detector according to claim 4, characterized in that: The elastic deformation part is a multi-section bending structure or a spiral structure.

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