Table-top type focal plane infrared detector and preparation method thereof

Abstract

The invention relates to a table-board type focal plane infrared detector and a preparation method thereof, the table-board type focal plane infrared detector comprises a reading circuit and an infrared sensitive layer, the infrared sensitive layer comprises a table-board array formed by arranging a plurality of table-board units, each table-board unit is connected with the reading circuit, and the reading circuit is connected with the table-board array. The edges of at least part of the table top units are filleted corners. According to the table-board type focal plane infrared detector provided by the invention, the edges of at least part of the table-board units are in fillet transition, so that the phenomenon of thermal stress concentration at the edges of the table-board units is avoided, the stress uniformity of the table-board units is improved, and the detection performance and the working reliability of the table-board type focal plane infrared detector are improved.

Description

Technical Field

[0001] The present invention relates to a mesa-type focal plane infrared detector and a preparation method thereof. Background Art

[0002] Existing infrared focal plane chips mainly have two structural forms: planar junctions and mesa junctions. Among them, the mesa-junction type focal plane chip is formed by flip-chip interconnecting the readout circuit and the mesa array of photosensitive elements in the vertical direction through indium pillars. Its mesa unit is a trapezoidal mesa unit obtained by ICP etching after lithography, and the side walls of the mesa unit have obvious edges and sharp corners.

[0003] During the use of a cooled infrared detector, in order to reduce background noise, it needs to be cooled by liquid nitrogen. However, due to the differences in the thermal conductivity and thermal expansion coefficient of each layer of materials in the focal plane chip, large thermal stresses are generated between the layers and at the mesa of the chip, and the stress has a great impact on the reliability and performance of the detector. As Figure 1 shown, during the cooling process of the trapezoidal mesa unit, stress concentration will occur at the edges and corners of the trapezoidal mesa unit. Excessive stress affects the reliability of the device, and will cause problems such as excessive local noise and increased dark current of the device. For long-wave and very long-wave devices that are sensitive to stress, excessive stress will cause the device performance to fail and become unusable. Summary of the Invention

[0004] The present invention relates to a mesa-type focal plane infrared detector and a preparation method thereof, which can at least solve some defects of the prior art.

[0005] The present invention relates to a mesa-type focal plane infrared detector, including a readout circuit and an infrared sensitive layer. The infrared sensitive layer includes a mesa array formed by arranging a plurality of mesa units, and each of the mesa units is connected to the readout circuit. At least some of the edges of each mesa unit are rounded.

[0006] As one of the embodiments, at least some of the mesa units are frustum-shaped mesa units, and the edges where the mesa intersects with the side walls are rounded.

[0007] As one of the embodiments, at least some of the mesa units are square frustum-shaped mesa units, and the edges where the mesa intersects with the side walls and the edges where the adjacent side walls intersect are rounded.

[0008] As one of the embodiments, each of the mesa units is flip-chip interconnected with the indium pillar of the readout circuit.

[0009] As one of the embodiments, an electrode metal thin film is formed on the mesa of the mesa unit, and the indium pillar is connected to the electrode metal thin film.

[0010] The present invention also relates to a method for manufacturing a mesa-type focal plane infrared detector, including

[0011] Manufacturing a readout circuit and an infrared sensitive layer respectively. For the infrared sensitive layer, a mesa array formed by arranging a plurality of mesa units is processed on a material substrate, and at least part of the edges of each mesa unit are rounded;

[0012] Completing the connection between the mesa array and the readout circuit.

[0013] As one of the implementation manners, the method for manufacturing the infrared sensitive layer includes:

[0014] According to the shape of the mesa unit, a mask array is processed on the material substrate, and at least part of the edges of each mask of the mask array are rounded;

[0015] Performing dry etching on the material substrate through each mask in the mask array to form mesa units consistent with the shapes of the masks.

[0016] As one of the implementation manners, the processing of forming a mask array on the material substrate according to the shape of the mesa unit specifically includes:

[0017] Forming a layer of mask material on the material substrate;

[0018] According to the shape of the mesa unit, a photoresist mask pattern array is processed above the mask material, and at least part of the edges of each photoresist mask pattern of the photoresist mask pattern array are rounded;

[0019] Performing dry etching on the mask material through the photoresist mask pattern array to form a mask array consistent with the shape of the photoresist mask pattern array.

[0020] As one of the implementation manners, at least part of the mesa units are configured as frustum-shaped mesa units, and the processing method of the photoresist mask pattern corresponding to the frustum-shaped mesa unit is as follows:

[0021] Forming a frustum-shaped photoresist mask pattern above the mask material by photolithography,

[0022] Making the edges where the mesa and the side wall of the frustum-shaped photoresist mask pattern intersect become rounded by baking.

[0023] As one of the implementation manners, at least part of the mesa units are configured as square frustum-shaped mesa units, and the processing method of the photoresist mask pattern corresponding to the square frustum-shaped mesa unit is as follows:

[0024] Forming a square frustum-shaped photoresist mask pattern above the mask material by photolithography,

[0025] By baking, the edges where the tabletop of the square tabletop photoresist mask pattern intersects with the sidewalls and the edges where adjacent sidewalls intersect are all made into rounded corners.

[0026] The present invention has at least the following beneficial effects:

[0027] For the mesa-type focal plane infrared detector provided by the present invention, the edges at least part of the mesa units are transitioned with rounded corners. In this way, the edges of the mesa units are eliminated, thus avoiding the phenomenon of thermal stress concentration at the edges of the mesa units, improving the force uniformity of the mesa units, and enhancing the detection performance and working reliability of the mesa-type focal plane infrared detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0029] Figure 1 The force test diagram of the trapezoidal mesa unit provided for the background technology;

[0030] Figure 2 The structural schematic diagram of the mesa-type focal plane infrared detector provided for the embodiment of the present invention;

[0031] Figure 3 The structural schematic diagram of the infrared sensitive layer provided for the embodiment of the present invention;

[0032] Figure 4 The schematic diagram of the preparation process of the frustum-shaped mesa unit provided for the embodiment of the present invention;

[0033] Figure 5 The force test diagram of the frustum-shaped mesa unit provided for the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The following clearly and completely describes the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0035] Embodiment 1

[0036] As Figure 2 and Figure 3, an embodiment of the present invention provides a mesa-type focal plane infrared detector, including a readout circuit 1 and an infrared sensitive layer. The infrared sensitive layer includes a mesa array formed by arranging a plurality of mesa units, and each of the mesa units is connected to the readout circuit 1.

[0037] In one embodiment, at least some of the edges of each mesa unit are rounded. In this way, the edges of the mesa unit are eliminated, thereby avoiding the phenomenon of thermal stress concentration at the edges of the mesa unit, improving the stress uniformity of the mesa unit, and enhancing the detection performance and working reliability of the mesa-type focal plane infrared detector.

[0038] In one embodiment, as Figure 2 and Figure 3 , at least some of the mesa units are frustum-shaped mesa units 22, and the edges where their mesa intersects with the side walls are rounded, that is, their mesa is connected to their side walls through a rounded transition surface 220. Among them, the small-diameter end of the frustum-shaped mesa unit 22 is the end close to the readout circuit 1.

[0039] In the above solution, at least some of the mesa units are designed as frustum-shaped mesa units 22, making the side walls of the mesa units without sharp corners, avoiding the phenomenon of stress concentration at the side wall corners of the mesa units due to thermal mismatch between different materials during the cooling process of the detector chip, and making the stress of the mesa units more uniform; the edges where the mesa of the frustum-shaped mesa unit 22 intersects with the side walls are rounded, also avoiding the phenomenon of stress concentration here and making the stress of the mesa unit more uniform.

[0040] Preferably, all the mesa units are frustum-shaped mesa units 22, further ensuring the detection performance and working reliability of the infrared detector.

[0041] In one embodiment, at least some of the mesa units are square frustum-shaped mesa units (that is, the structure of the mesa unit is a frustum), and the edges where their mesa intersects with the side walls and the edges where the adjacent side walls intersect are all rounded, that is, their mesa is connected to their side walls through a rounded transition surface 220, and the adjacent side walls are also connected through a rounded transition surface 220. In this solution, all the edges of the square frustum-shaped mesa unit are rounded, avoiding the phenomenon of stress concentration at the edges of the mesa unit and making the stress of the mesa unit more uniform. Among them, the small-size end of the square frustum-shaped mesa unit is the end close to the readout circuit 1.

[0042] As Figure 2 and Figure 3, preferably, the infrared sensitive layer includes a material substrate 21, and the mesa array is formed on the material substrate 21; wherein, the material substrate 21 has a first base surface facing the readout circuit 1 and a second base surface facing away from the readout circuit 1, the mesa array is formed on the first base surface, and the large-sized end of the frustum-shaped mesa unit 22 / square mesa unit is connected to the first base surface.

[0043] In one embodiment, each of the mesa units is respectively flip-chip interconnected with the indium pillars of the readout circuit 1; correspondingly, indium pillar bumps are provided at the small-diameter end of the mesa unit, and indium pillar bumps are also provided on the readout circuit 1 in a matching manner. The indium pillar bumps of the mesa unit are aligned and interconnected with the indium pillar bumps on the readout circuit 1 to form indium pillars 3, realizing the electrical interconnection between the mesa unit and the readout circuit 1.

[0044] Furthermore, an electrode metal thin film 23 is formed on the mesa of the mesa unit, and the indium pillar 3 is connected to the electrode metal thin film 23 to ensure the electrical connection reliability of the flip-chip interconnect structure; wherein, optionally, holes are opened on the mesa of the mesa unit and the electrode metal thin film 23 is fabricated, and the electrode metal thin film 23 can cover the inner wall of the mesa opening and the remaining area of the mesa.

[0045] Embodiment 2

[0046] The embodiment of the present invention provides a method for manufacturing a mesa-type focal plane infrared detector, including:

[0047] Manufacture the readout circuit 1 and the infrared sensitive layer respectively. Among them, for the infrared sensitive layer, a mesa array formed by arranging a plurality of mesa units is processed on the material substrate 21, and at least part of the edges of each of the mesa units are rounded.

[0048] Complete the connection between the mesa array and the readout circuit 1.

[0049] Among them, through the above manufacturing method, the mesa-type focal plane infrared detector provided in the first embodiment can be manufactured.

[0050] In one embodiment, as Figure 4 , the manufacturing method of the infrared sensitive layer includes:

[0051] According to the shape of the mesa unit, a mask pattern array is processed on the material substrate 21, and at least part of the edges of each mask 204 of the mask array are rounded.

[0052] The material substrate 21 is dry-etched through each mask 204 in the mask array to form each mesa unit having the same shape as each mask 204. Among them, the dry-etching process used in this step includes but is not limited to the ICP (Inductively Coupled Plasma) etching process; wherein, different fillet radius sizes can be obtained by adjusting the dry-etching process parameters.

[0053] Further, after forming each mesa unit having the same shape as each mask 204, each mesa unit is passivated.

[0054] As described above, the mesa unit is preferably flip-chip interconnected with the indium pillar of the readout circuit 1. Correspondingly, the manufacturing method of the infrared sensitive layer further includes:

[0055] After passivating each mesa unit, an interconnect electrode is fabricated at the mesa of the mesa unit.

[0056] The connection between each mesa unit and the readout circuit 1 is achieved by flip-chip interconnecting with indium pillars.

[0057] Among them, indium pillar bumps are respectively fabricated on the mesa unit and the readout circuit 1, and the indium pillar bumps on the mesa unit are aligned and interconnected with the indium pillar bumps on the readout circuit 1 to form indium pillars 3, realizing the electrical interconnection between the mesa unit and the readout circuit 1.

[0058] After completing the connection between the mesa array and the readout circuit 1, subsequent chip processes can be performed according to process requirements.

[0059] Preferably, as Figure 4 , processing a mask array on the material substrate 21 according to the shape of the mesa unit specifically includes:

[0060] Forming a layer of mask material 201 on the material substrate 21;

[0061] According to the shape of the mesa unit, a photoresist mask pattern array is processed above the mask material 201, and the edges of at least some of the photoresist mask patterns 203 in the photoresist mask pattern array are all rounded;

[0062] The mask material 201 is dry-etched through the photoresist mask pattern array to form a mask array having the same shape as the photoresist mask pattern array. Among them, the dry-etching process used in this step includes but is not limited to the RIE (reaction ion etching) etching process; wherein, different fillet radius sizes can be obtained by adjusting the dry-etching process parameters.

[0063] Optionally, at least part of the tabletop unit is configured as a frustum-shaped tabletop unit 22. The processing method of the photoresist mask pattern 203 corresponding to the frustum-shaped tabletop unit 22 is as follows:

[0064] An initial photoresist mask pattern 202 is processed and formed above the mask material 201 by photolithography. The initial photoresist mask pattern 202 is a frustum-shaped photoresist mask pattern.

[0065] By baking, the edges where the tabletop of the frustum-shaped photoresist mask pattern intersects with the sidewalls are made into rounded corners.

[0066] Optionally, at least part of the tabletop unit is configured as a square frustum-shaped tabletop unit. The processing method of the photoresist mask pattern 203 corresponding to the square frustum-shaped tabletop unit is as follows:

[0067] An initial photoresist mask pattern 202 is processed and formed above the mask material 201 by photolithography. The initial photoresist mask pattern 202 is a square frustum-shaped photoresist mask pattern.

[0068] By baking, the edges where the tabletop of the square frustum-shaped photoresist mask pattern intersects with the sidewalls and the edges where adjacent sidewalls intersect are both made into rounded corners.

[0069] The above preparation process can ensure the quality of the obtained product. The rounding treatment is carried out by baking, which has the advantages of simple operation, controllability, high rounding accuracy, etc. Moreover, the rounding radius size can be adjusted by the dry etching process, so as to obtain a high-precision rounded corner transition structure and improve the stress uniformity of the tabletop unit.

[0070] The tabletop type focal plane infrared detector obtained based on the technical solution in this embodiment is tested. As Figure 5 , it can be seen that the maximum stress received by the tabletop unit is smaller and the stress is more uniform.

[0071] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A table-type focal plane infrared detector, comprising a readout circuit and an infrared sensitive layer, wherein the infrared sensitive layer comprises a table array formed by arranging a plurality of table units, each of the table units is connected to the readout circuit, characterized in that: At least some of the table top units have rounded edges.

2. The table-top focal plane infrared detector according to claim 1, characterized in that: At least part of the table top units are truncated table top units, and the edges where the table tops intersect with the side walls are rounded.

3. The table-top focal plane infrared detector according to claim 1, characterized in that: At least part of the table top units are square table top units, and the edges where the table tops intersect with the side walls and the edges where adjacent side walls intersect are rounded.

4. The table-top focal plane infrared detector according to claim 1, characterized in that: Each of the mesa units is interconnected with the indium pillar of the readout circuit by reverse soldering.

5. The table-top focal plane infrared detector according to claim 3, characterized in that: An electrode metal film is formed on the table of the table unit, and the indium column is connected to the electrode metal film.

6. A method for preparing a table-type focal plane infrared detector, characterized in that: include A readout circuit and an infrared sensitive layer are manufactured separately, wherein for the infrared sensitive layer, a mesa array formed by arranging a plurality of mesa units is processed on a material substrate, and each edge of at least part of the mesa units is rounded; Complete the connection between the mesa array and the readout circuit.

7. The preparation method according to claim 6, characterized in that: The method for manufacturing the infrared sensitive layer comprises: According to the shape of the mesa unit, a mask array is formed on the material substrate, wherein at least part of the masks of the mask array have rounded edges; The material substrate is dry-etched through each mask in the mask array to form each mesa unit having the same shape as each mask.

8. The preparation method according to claim 7, characterized in that: The process of forming a mask array on a material substrate according to the shape of the mesa unit specifically includes: forming a layer of mask material on a material substrate; According to the shape of the mesa unit, a photoresist mask pattern array is formed on the mask material, wherein at least part of the photoresist mask patterns of the photoresist mask pattern array have rounded corners at their edges; The mask material is dry-etched through the photoresist mask pattern array to form a mask array having the same shape as the photoresist mask pattern array.

9. The preparation method according to claim 8, characterized in that: At least part of the mesa units are constructed as truncated mesa units, and the processing method of the photoresist mask pattern corresponding to the truncated mesa units is as follows: A truncated cone-shaped photoresist mask pattern is formed on the mask material by photolithography. The edges where the table and the side wall of the truncated table-shaped photoresist mask pattern intersect are rounded by baking.

10. The preparation method according to claim 8, characterized in that: At least part of the mesa units are constructed as square mesa units, and the processing method of the photoresist mask pattern corresponding to the square mesa units is as follows: A square-shaped photoresist mask pattern is formed on the mask material by photolithography. By baking, the edges where the terrace and the side wall of the square terrace photoresist mask pattern intersect, as well as the edges where the adjacent side walls intersect, are all rounded.

Images