Preparation method of infrared detector chip and ratchet auxiliary structure

Abstract

This invention discloses a toothed auxiliary structure for fabricating infrared detector chips, processed on a readout circuit and a photosensitive chip. The readout circuit and the photosensitive chip are flip-soldered together. The structure includes a board, several raised units, and several recessed units. All raised and recessed units are located on the same plane of the board. The raised units are arranged sequentially, with a recessed unit formed between adjacent raised units. Adjacent raised and recessed units are arranged in a toothed pattern. The readout circuit and the photosensitive chip are morphologically coupled, with the coupling points being the matching coupling between the raised units and their corresponding recessed units. This invention can significantly reduce the stringent requirements of fabrication processes regarding the consistency of small-sized indium pillar solder joint morphology, large array flip-solder offset, and controllable flip-solder gaps, solving the flip-soldering technical challenges of large-array small-pixel infrared detector chips, thereby reducing the cost of infrared detectors and improving production efficiency.

Description

Technical Field

[0001] This invention belongs to the field of chip manufacturing, and particularly relates to a method for preparing an infrared detector chip and a toothed auxiliary structure. Background Technology

[0002] Flip-chip bonding (FIP) is an advanced semiconductor packaging technology widely used in high-frequency, high-speed, high-I / O-port-count integrated circuit chips, as well as in heterogeneous material-based light-emitting, detection, and power semiconductor devices. Infrared detector chips, as the core components of infrared imaging systems, typically consist of a silicon-based readout circuit and an infrared photosensitive chip (usually a compound semiconductor material). These two parts are electrically interconnected by pre-depositing corresponding indium solder joints and then using flip-chip bonding technology. The imaging principle is as follows: the photosensitive chip converts the infrared light emitted by targets at different temperatures in the detected scene into electrons through the photoelectric effect. The readout circuit converts these electrons into a voltage signal usable by the imaging system and outputs it according to a set timing requirement, allowing the user to obtain an infrared image of the target. Infrared imaging systems have outstanding advantages such as good passive detection concealment, high temperature resolution, unaffected by visible light visibility, and 24 / 7 monitoring capabilities. They are widely used in various military and civilian applications, including alarm systems, guidance systems, temperature measurement, industrial flaw detection, night vision security, and resource exploration.

[0003] To achieve higher resolution and longer detection distances, domestic infrared detector arrays are gradually moving towards megapixel scale. While expanding the pixel array size, it's crucial to simultaneously reduce pixel dimensions to ensure higher pixel density. Otherwise, simply increasing the pixel array size will lead to extremely high costs for infrared imaging systems, ultimately hindering the application of large-array detectors. Currently, the mainstream pixel size for domestic infrared detectors is 15 micrometers. Detectors with pixel sizes below 15 micrometers are gradually entering the market. One of the key challenges affecting their large-scale application is the flip-soldering technology with sub-micrometer offset. Key aspects related to this technology include: consistency of small-size indium solder joint morphology, large array flip-soldering offset, and flip-soldering gap. On the device side, this manifests as substandard conductivity and unstable process reliability. Summary of the Invention

[0004] The technical objective of this invention is to provide a method for fabricating an infrared detector chip and a toothed auxiliary structure to solve the problems of low conductivity and unstable process in the prior art.

[0005] To solve the above problems, the technical solution of the present invention is as follows:

[0006] A toothed auxiliary structure for fabricating an infrared detector chip, fabricated on a readout circuit and a photosensitive chip, wherein the readout circuit and the photosensitive chip are flip-soldered together, comprising:

[0007] The plate consists of several raised elements and several recessed elements; the raised elements and recessed elements are all located on the same plane of the plate; the raised elements are arranged sequentially, and recessed elements are formed between two adjacent raised elements; adjacent raised elements and recessed elements cooperate with each other in a toothed arrangement.

[0008] The readout circuit and the photosensitive chip are morphologically coupled. The coupling point is that the raised units on both sides are matched and coupled to the corresponding pit units to achieve mutual coupling.

[0009] The raised units and the pit units are obtained by etching process, and the etching angle is greater than 85°.

[0010] Specifically, when located at the mutual coupling point, the difference between the protrusion height of the protrusion unit and the pit depth of the pit unit is the post-reverse welding gap required for the reverse welding process; the difference between the protrusion side length of the protrusion unit and the pit side length is the post-reverse welding offset required for the reverse welding process.

[0011] A method for fabricating an infrared detector chip, using a toothed auxiliary structure for fabricating an infrared detector chip according to any one of the above, includes the following steps: constructing a toothed auxiliary structure placed at a specified position on the readout circuit and the photosensitive chip by an etching process, wherein at least 3 toothed auxiliary structures are placed on the readout circuit and the photosensitive chip respectively, and the 3 toothed auxiliary structures must not be on the same straight line; and coupling the readout circuit and the photosensitive chip together by a flip-soldering process.

[0012] Specifically, in-situ etching is performed at designated locations on the readout circuit and the photosensitive chip to obtain the readout circuit and the photosensitive chip equipped with the toothed auxiliary structure.

[0013] In this process, the tooth-assisted structure is independently etched and then placed at the designated positions of the readout circuit and the photosensitive chip. The material of the independently etched tooth-assisted structure is consistent with the material of the corresponding readout circuit or photosensitive chip.

[0014] The designated location is the coupling connection point between the readout circuit and the photosensitive chip.

[0015] Preferably, the toothed auxiliary structures are respectively processed and placed at the four corners of the readout circuit and the photosensitive chip, and the toothed auxiliary structures on both sides of the four corners are coupled to each other.

[0016] Because the present invention adopts the above technical solution, it has the following advantages and positive effects compared with the prior art:

[0017] This invention can simultaneously and significantly reduce the stringent requirements of the processing technology on the uniformity of small-sized indium pillar solder joint morphology, the offset of large array flip soldering, and the controllability of flip soldering gap, thus solving the flip soldering technical problem of large array small pixel infrared detector chips, thereby reducing the cost of infrared detectors and improving production efficiency. Attached Figure Description

[0018] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention.

[0019] Figure 1 This is a schematic flowchart of a method for fabricating an infrared detector chip according to the present invention.

[0020] Figure 2 These are a top view (a) and a side view (b) of a toothed auxiliary structure according to the present invention;

[0021] Figure 3 For the present invention and Figure 1 Top view (a) and side view (b) of the other mutually coupled tooth auxiliary structure;

[0022] Figure 4 This is a schematic diagram of the toothed auxiliary structure of the present invention placed in the readout circuit (a) and the photosensitive chip (b);

[0023] Figure 5 The diagram shows the flip-soldering process between the readout circuit and the photosensitive chip in this invention, before flip-soldering (a) and after flip-soldering (b). Detailed Implementation

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without any creative effort.

[0025] To keep the drawings concise, only the parts relevant to the invention are shown schematically in each figure, and they do not represent the actual structure of the product. Furthermore, for ease of understanding, in some figures, only one of components with the same structure or function is shown schematically, or only one is labeled. In this document, "one" can mean not only "only one" but also "more than one".

[0026] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a method for fabricating an infrared detector chip and a toothed auxiliary structure based on the present invention. The advantages and features of the present invention will become clearer from the following description and claims.

[0027] Example

[0028] See Figures 1 to 5This embodiment provides a method for fabricating an infrared detector chip and a toothed auxiliary structure. By introducing high-precision toothed auxiliary structures on both sides of the readout circuit and the photosensitive chip, this embodiment significantly reduces the requirements for the consistency of small-sized indium pillar solder joint morphology and large-array flip-flop technology in the processing technology, ensuring the yield of the flip-flop process. The mutual coupling of the toothed auxiliary structure moves the processing of indium solder joints and the accuracy of flip-flop alignment of the large-array infrared chip forward. The flip-flop gap and offset considerations are designed in advance and reflected in the toothed auxiliary structure, and it is no longer sensitive to flip-flop pressure. This toothed auxiliary structure can be fabricated in situ on both sides of the readout circuit and the photosensitive chip, or it can be pre-processed independently and then placed at designated positions on the readout circuit and the photosensitive chip respectively.

[0029] See Figure 2 and Figure 3 The toothed auxiliary structure includes a board, several raised units, and several recessed units. Both the raised and recessed units are located on the same plane of the board, i.e., distributed along the XY plane of the board. Precise mutual coupling is achieved through the raised and recessed units in the Z direction, that is, morphological mutual coupling between the readout circuit and the photosensitive chip. This can be understood as the mutual coupling points being the matching coupling connection between the raised units on both sides and the corresponding recessed units. Specifically, the raised units are arranged sequentially, with a recessed unit formed between two adjacent raised units, thus creating a toothed arrangement when viewed from the side.

[0030] Since the shape of the sheet metal on the XY plane can be freely customized, this embodiment only uses... Figure 1 and Figure 2 The following example illustrates this. The board surface is designed as a square island platform, including square raised units and square recessed units. Both the raised and recessed units can be customized in shape; the square shape shown here is merely illustrative. Specifically, the required post-soldering gap for the soldering process is obtained by designing the difference between the raised height of one side's raised unit and the recess depth of the other side's recessed unit. The required post-soldering offset for the soldering process is obtained by designing the difference between the side length of one side's raised unit and the side length of the other side's recessed unit.

[0031] For example, if the gap (i.e., the height value in the Z direction) between the readout circuit and the chip after flip soldering of an infrared detector is required to be 5 micrometers, the height of the protrusion on one side can be designed to be a+5 (micrometers), and the depth of the pit on the other side can be designed to be a micrometers. After the flip soldering process is completed, the target gap value of 5 micrometers can be obtained.

[0032] The required offset (i.e., the XY plane) after the soldering process can be calculated by taking the X direction as an example. For the raised pattern on one side, the X-direction length can be designed to be b micrometers, and the X-direction length of the recessed pattern on the other side can be designed to be b+0.2 micrometers. After the soldering process is completed, the offset in the X direction can be controlled within ±0.1 micrometers. The same applies to the Y direction.

[0033] The dimensions of the aforementioned raised and recessed units can be precisely obtained through etching. Since the raised and recessed units at the coupling point need to be matched, the etching angle should be greater than 85° so that the preset soldering accuracy target value can be achieved using the aforementioned toothed auxiliary structure.

[0034] See Figure 1 , Figure 4 and Figure 5 The following explains how to obtain a readout circuit or photosensitive chip with a toothed auxiliary structure: Firstly, in-situ etching can be performed at designated locations on both the readout circuit and the photosensitive chip. Secondly, the toothed auxiliary structure can be obtained through independent etching, and then placed at designated locations on both the readout circuit and the photosensitive chip for subsequent flip-flop bonding. To achieve good stress matching, the preferred materials for independently fabricating the toothed auxiliary structure are the silicon substrate of the readout circuit and the compound semiconductor substrate of the photosensitive chip. The designated locations mentioned above refer to the coupling connection points between the readout circuit and the photosensitive chip.

[0035] Furthermore, the readout circuit and the photosensitive chip each have at least three toothed auxiliary structures, and the three toothed auxiliary structures must not be on the same straight line in order to control the offset of the flip solder in the X and Y directions.

[0036] In a better location, Figure 4 and Figure 5 For example, the tooth-shaped auxiliary structure is processed and placed at the four corners of the readout circuit and the photosensitive chip, and the tooth-shaped auxiliary structure located on both sides of the four corners is as follows: Figure 5 The diagram shows a one-to-one coupling, thus achieving a reverse solder joint. The placement of the toothed auxiliary structure here is merely illustrative and not a limitation. For example... Figure 5 As shown, the indium solder joints marked 1 on both sides are welded together, and the substrate on one side marked 2 is flip-welded to the substrate on the other side marked 3.

[0037] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they shall still fall within the protection scope of the present invention.

Claims

1. A toothed auxiliary structure for fabricating an infrared detector chip, fabricated on a readout circuit and a photosensitive chip, wherein the readout circuit and the photosensitive chip are flip-soldered together, characterized in that, include: The plate comprises a plurality of protruding units and a plurality of recessed units; the plurality of protruding units and the plurality of recessed units are all disposed on the same plane of the plate; the plurality of protruding units are arranged sequentially, and the recessed units are formed between two adjacent protruding units; the adjacent protruding units and the recessed units cooperate with each other in a toothed arrangement; The readout circuit and the photosensitive chip are morphologically coupled, and the coupling point is that the protruding units on both sides and the corresponding pit units are matched and coupled to each other to achieve mutual coupling; When located at the mutual coupling point, the difference between the protrusion height of the protrusion unit and the pit depth of the pit unit is the post-reverse welding gap required for the reverse welding process; the difference between the protrusion side length of the protrusion unit and the pit side length of the pit unit is the post-reverse welding offset required for the reverse welding process.

2. The toothed auxiliary structure for fabricating an infrared detector chip according to claim 1, characterized in that, The raised units and the recessed units are obtained by etching process, and the etching angle is greater than 85°.

3. A method for fabricating an infrared detector chip, comprising using the toothed auxiliary structure for fabricating an infrared detector chip as described in any one of claims 1 or 2, characterized in that, The process includes the following steps: constructing a toothed auxiliary structure at a designated location on the readout circuit and the photosensitive chip using an etching process, wherein at least three toothed auxiliary structures are placed on both the readout circuit and the photosensitive chip, and the three toothed auxiliary structures must not be on the same straight line; and coupling the readout circuit and the photosensitive chip together using a flip-soldering process.

4. The method for fabricating an infrared detector chip according to claim 3, characterized in that, In-situ etching is performed at designated locations on the readout circuit and the photosensitive chip to obtain the readout circuit and the photosensitive chip with the toothed auxiliary structure.

5. The method for fabricating an infrared detector chip according to claim 3, characterized in that, After the tooth-shaped auxiliary structure is independently etched and processed, it is placed in the designated position of the readout circuit and the photosensitive chip. The material of the independently processed tooth-shaped auxiliary structure is consistent with the material of the corresponding readout circuit or photosensitive chip.

6. The method for fabricating an infrared detector chip according to claim 3, characterized in that, The specified location is the coupling connection point between the readout circuit and the photosensitive chip.

7. The method for fabricating an infrared detector chip according to claim 3, characterized in that, The tooth-shaped auxiliary structures are respectively processed and placed at the four corners of the readout circuit and the photosensitive chip, and the tooth-shaped auxiliary structures on both sides of the four corners are coupled to each other.

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