CN113532655B

CN113532655B - Infrared thermal imaging sensor pixel and infrared thermal imaging sensor

Info

Publication number: CN113532655B
Application number: CN202110753305.XA
Authority: CN
Inventors: 李成强; 刘大河; 李克之; 陈光毅; 施薛优; 王添翼
Original assignee: Beijing Anku Zhixin Technology Co ltd
Current assignee: Beijing Anku Zhixin Technology Co ltd
Priority date: 2021-07-02
Filing date: 2021-07-02
Publication date: 2023-04-18
Anticipated expiration: 2041-07-02
Also published as: CN113532655A

Abstract

The invention provides an infrared thermal imaging sensor pixel and an infrared thermal imaging sensor, which relate to the field of sensor pixels and comprise: the bridge comprises a bridge pier, an absorption layer, a bridge arm, an ROIC substrate, a thermosensitive element and an interconnection through hole; the bridge piers are connected with the bridge arms, the interconnection through holes are arranged in the bridge piers, the absorption layer and the thermosensitive elements form a bridge deck structure, the absorption layer is located on the upper surfaces of the thermosensitive elements, the bridge arms are bent to form an array, the length of each coil of the array is increased progressively, and the bridge piers are of a flat structure; the distance arrangement between the piers is increased, the space for bridge arm arrangement is increased, and the bridge arm length is increased in a limited space by combining the folding arrangement of the bridge arms, so that the heat conduction of the pixel structure is reduced, and the NETD index is improved. Furthermore, the lengthened bridge arm space structure is bent in an increasing mode, and the multi-layer bending structure can enhance the anti-vibration performance of the bridge arm. An additional backup interconnection through hole is arranged in the pier, so that the effective contact area is increased, the contact resistance is reduced, and the bad pixel rate is reduced due to the existence of the backup interconnection through hole.

Description

Infrared thermal imaging sensor pixel and infrared thermal imaging sensor

Technical Field

The invention relates to the field of imaging sensors, in particular to an infrared thermal imaging sensor pixel and an infrared thermal imaging sensor.

Background

With the development of uncooled infrared thermal focal plane detector technology, the application of infrared imaging technology gradually goes into people's lives. In an infrared system, an infrared thermal imaging sensor is a core, and detects infrared radiation by using a physical effect exhibited by interaction between the infrared radiation and a substance. In an infrared imaging sensor, a pixel structure is a core, and mainly includes a ROIC (Read Out Integrated Circuit) substrate, a bridge pier, a bridge deck, and a bridge arm.

With the development of Micro-Electro-Mechanical System (MEMS) technology, the infrared thermal imaging sensor has realized miniaturization, high integration, and mass production, and is developed towards a large area array and small pixels, but the reduction of the pixel size leads to the reduction of the area of the thermistor, which increases thermal noise to a certain extent and reduces the response rate of the sensor; meanwhile, in the prior art, in order to achieve a large filling rate, a mode that one pixel uses one pier alone is changed into a mode that a plurality of adjacent pixels share one pier (specifically, as shown in fig. 1), but in the mode, when one pier is damaged, functions of the adjacent pixels are affected, and the probability of the bad pixels is increased.

In order to solve the above problems, a MEMS image sensor pixel is further provided in the prior art, as shown in fig. 2. The bridge deck is fixed on the substrate through bridge arms and piers, and electric signals generated on the bridge deck are transmitted to a reading circuit on the ROIC substrate through leads in the piers, the cross sections of the bridge arms are in a periodic zigzag shape, so that the bridge arms can be prolonged to a greater extent in a limited space, the thermal conductivity is reduced, and the NETD (Noise Equivalent Temperature Difference) index is improved. However, in the mode, the cross section of the bridge arm is in a continuous trapezoidal waveform or zigzag shape and other special shapes, the preparation process is complex, the cost is high, and the existing MEMS plane process is difficult to support the wide application of the improved technology.

Therefore, a widely applicable novel infrared thermal imaging sensor pixel structure is needed to reduce the probability of bad pixels, optimize the anti-vibration performance of the sensor, and enable the sensor to obtain an excellent NETD value.

Disclosure of Invention

The embodiment of the invention provides an infrared thermal imaging sensor pixel and an infrared thermal imaging sensor, which can improve NETD (network Internet data) indexes of an integral pixel structure, reduce the bad pixel rate and realize wide application.

In order to solve the above problem, a first aspect of embodiments of the present invention provides an infrared thermal imaging sensor pixel, including: the bridge comprises a pier 1, an absorption layer 2, a bridge arm 3, an interconnection through hole 4 and a thermosensitive element 5;

each pier 1 is connected with the thermosensitive element 5 through one bridge arm 3; at least one interconnection through hole 4 is arranged inside one pier 1;

the absorption layer 2 is positioned on the upper surface of the thermosensitive element 5;

the absorption layer 2 and the thermosensitive element 5 form a bridge deck structure

Each bridge arm 3 is bent to form an array, and the coil lengths of a plurality of bent sections in the array are arranged in an increasing mode;

the pier 1 may have a flat structure.

In some embodiments, the pixel structure of the infrared thermal imaging sensor further comprises a substrate ROIC 6, and the substrate ROIC 6 is arranged at the bottom of the heat sensitive element 5.

In some embodiments, the thermosensitive element 5 is connected to at least one of the piers 1 through the bridge arm 3 on each of the left and right sides.

In some embodiments, the plurality of interconnected through holes 4 in the pier 1 includes at least one reserved hole therein.

In some embodiments, the bending of the legs 3 into the coil lengths of the plurality of bends in the array comprises: and at least one of an arithmetic series, an geometric series and an exponential distributed arrangement.

In some embodiments, the bent array shape of the bridge arm 3 includes: at least one of U-shaped folding, V-shaped folding and wave-shaped folding.

In some embodiments, a preset distance is kept between the piers 1 which are arranged adjacently up and down on the same side of the thermosensitive element 5.

In some embodiments, the interconnect vias 4 may be at least circular or flat in shape.

In some embodiments, the number of the interconnection vias 4 included in the pier 1 is at least 2.

In some embodiments, the predetermined shapes of the interconnect vias 4 may be different.

The second aspect of the embodiments of the present invention further provides an infrared thermal imaging sensor, where the thermal infrared sensor includes the pixel described in the above embodiments, and a plurality of pixels form an array in the infrared thermal imaging sensor.

In some embodiments, in the array composed of the pixels, the bent shapes of two adjacent bridge arms 3 are complementary.

The embodiment of the invention provides a pixel for changing the spatial structures of bridge arms and bridge piers and an infrared thermal imaging sensor. Furthermore, the bridge arm space structure with the variable length adopts incremental bending, and the multi-layer bending structure can enhance the anti-vibration performance of the bridge arm. An additional backup interconnection through hole is set in the pier, so that the effective contact area is increased, the contact resistance is reduced, and the bad pixel rate is reduced due to the existence of the backup interconnection through hole.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application.

FIG. 1 is a schematic diagram of an L-shaped pixel structure in the prior art;

FIG. 2 is a schematic cross-sectional view of a pixel structure further appearing in the prior art;

FIG. 3 is a schematic diagram of a pixel structure for changing a spatial structure of a bridge arm and a bridge pier according to an embodiment of the invention;

FIG. 4 is a schematic diagram of a pixel structure of an equal-difference incremental bridge arm arrangement according to an embodiment of the present invention;

fig. 5 is a schematic diagram of a pixel structure interconnection via for changing the spatial structures of a bridge arm and a bridge pier according to an embodiment of the invention.

Fig. 6 is a schematic layout diagram of a folded pixel structure array according to an embodiment of the present invention.

Fig. 7 is a schematic diagram illustrating comparison of data related to arrangement of a folding pixel structure according to an embodiment of the present invention.

Detailed Description

In order to make the objects, features and advantages of the present invention more apparent and understandable, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

It will be understood by those within the art that the terms "first", "second", etc. in this application are used only to distinguish one device, module, parameter, etc., from another, and do not denote any particular technical meaning or necessary order therebetween.

In the prior art, the pixel structure is designed as shown in fig. 1, bridge arms are mostly in an L-shaped design, a single pixel bridge floor carries two shared circular piers which are symmetrically arranged in the center, each circular pier is connected with the bridge floor through an independent bridge arm, and in the working process of the pixel structure, if the shared piers are abnormal, the transmission of pixel signals adjacent to the shared piers is blocked, so that the phenomenon of bad pixels is caused, and the bridge arm arrangement in the prior art is influenced by the distance between the piers, and the distance between the adjacent piers is insufficient, so that the bridge arm length is smaller, and the thermal conductivity of the whole structure of the infrared thermal imaging sensor is larger, and the NETD is larger; meanwhile, the L-shaped bridge arm space presents a single-layer folded state, and the effect of resisting environmental vibration is poor.

In order to solve the above problems, a MEMS image sensor pixel has further appeared in the prior art, as shown in fig. 2. The bridge deck structure is fixed on the substrate through bridge arms and bridge piers, electric signals generated on the bridge deck are transmitted to the read-out circuit on the ROIC substrate through leads in the bridge piers, the cross sections of the bridge arms are in a periodic zigzag shape, the bridge arms can be prolonged to the maximum extent in a limited space, and therefore thermal conductivity is reduced, and NETD indexes are improved. The existing MEMS mainly takes photoetching, film deposition, sputtering, etching, cleaning, scribing, packaging and the like as basic process steps to carry out micro-processing on three-dimensional bodies of semiconductors, the processing scale is different from nanometer to millimeter, but because the cross section of a bridge arm is in a special shape such as a continuous trapezoidal waveform or sawtooth shape, the existing MEMS plane process is difficult to support the wide application of the improvement technology thereof.

As shown in fig. 3, a pixel for changing a spatial structure of a bridge arm and a bridge pier according to an embodiment of the present invention includes: the bridge comprises a bridge pier 1, an absorption layer 2, a bridge arm 3, an interconnection through hole 4, a thermosensitive element 5 and an ROIC substrate 6; the pier 1 is flat (but not limited to flat), the interconnection through holes 4 are arranged in the pier 1, the left side and the right side of the thermosensitive element 5 are respectively connected with at least one pier 1 through the bridge arm 3, a preset distance (the order of magnitude is 8-25 mu m) is kept between the piers 1 arranged on the same side of the thermosensitive element 5 so that the piers do not contact and interfere with each other, the absorption layer 2 wraps the upper surface of the thermosensitive element 5, and the ROIC substrate 6 is paved below the pier 1, the bridge arm 3 and the thermosensitive element 5 and bears an integral pixel.

In the mode of the invention, in order to ensure that the length of the bridge arm 3 is prolonged as much as possible in the space for fixing the pixel structure, the design of the bridge pier 1 is different from the design of the existing round bridge pier, a flat structure design is adopted, under the condition of a fixed area, as shown in figure 3, the flat structure can increase the distance (space) between two adjacent bridge piers in the vertical direction, further ensure that the reserved storage space of the bridge arm 3 is increased, and the strength of the bridge arm 3 can be prolonged, according to a thermal resistance calculation formula of theta = L/(lambda S) (lambda is the thermal conductivity, L is the material thickness or length, and S is the heat transfer area), the capability of an object for obstructing heat flow conduction is known to be in direct proportion to the length of a conduction path under the condition of the fixed thermal conductivity lambda; when the thermal resistance is increased, the thermal conductivity of the pixel structure is reduced, so that the thermal conductivity can be effectively reduced by increasing the length of the bridge arm 3. Combining with the existing actual production or the published DOE (Design Of experience) conclusion, it can be known that the thermal conductivity is a main factor influencing the NETD index Of the pixel structure, the thermal conductivity and the NETD index are in positive correlation, the lower the value expectation Of the NETD in the existing stage production preparation is, the better the value expectation is, the lower the thermal conductivity is, the lower the value Of the NETD is, and the NETD index is improved (the smaller the NETD is, the better the value Of the NETD index is expected to be, the lower the value Of the NETD index is, and the lower the value Of the NETD index is).

In an embodiment of the present invention, in order to ensure that the length of the bridge arm 3 is extended as much as possible within a predetermined fixed distance reserved between the bridge piers 1, the arrangement shape of the bridge arm 3 is a bending arrangement, and in combination with the relative position between the connection point of the bridge arm 3 to the thermosensitive element 5 and the bridge pier 1, the coil arrangement mode of the plurality of bending sections of the bridge arm 3 formed by bending into an array can be an incremental arrangement or a decremental arrangement.

In an embodiment of the present invention, the pixels are arranged in an array manner in an infrared thermal imaging sensor, as shown in fig. 6, two piers 1 are respectively distributed on the left and right sides of each thermal sensitive element 5 in a centrosymmetric manner, the piers 1 are connected to the thermal sensitive elements 5 through the bridge arms 3, a reserved space of the piers 1 adjacent to each other is set on one side of each thermal sensitive element 5, the bridge arms 3 are arranged, coils of bent sections of the bridge arms 3 are arranged in a U-shaped incremental arithmetic progression manner, an arithmetic progression value Δ is fixed, bent shapes of two bridge arms 3 adjacent to each other in position are complementary, and a plurality of pixels are arranged in an array manner to form the infrared thermal imaging sensor. Compared with the existing L-shaped bridge arm technical arrangement, under the condition of the same fixed thermistor area (70 μm < 2 >), the length of the bridge arm 3 is increased by 89.3%, the NETD index is reduced by 32.5%, and the related verification comparison data are shown in FIG. 7.

In an embodiment of the invention, in order to further ensure the anti-vibration capability of the bridge arm of the pixel structure of the novel infrared thermal imaging sensor, and particularly prevent the bridge arm from being deformed due to environmental impact on the pixel array, the bridge arms 3 are arranged in a bending manner to fill the space between adjacent piers 1, and the corresponding arrangement logic of the bridge arms 3 is set according to the internal space state of the pixel structure, including but not limited to one or more of a U shape, a V shape, a wave shape and an arch shape. The bridge arm and the bridge pier in the pixel structure can be integrally regarded as a cantilever beam structure, the bridge arm 3 has a space folding structure compared with the existing L-shaped bridge arm in structure, so that the overall cross section area is indirectly increased, and according to a stress formula delta = F/A (F: external acting force; A: unit area of material), under the condition of the same external acting force, the larger the unit area of the stressed material is, the smaller the stress borne by the bridge arm 3 structure is, and the overall vibration resistance of the pixel structure is better.

In an embodiment of the present invention, when the bridge pier 1 is in a flat state, in order to ensure that the internal space of the bridge pier 1 is fully utilized, the interconnecting through holes 4 may be flat and may have different shapes, and the number of the interconnecting through holes 4 arranged inside the bridge pier 1 may be at least 2.

In an embodiment of the invention, in order to ensure that the bad pixel rate of the pixel structure is effectively reduced, the interconnection through holes 4 can be used as reserved holes, at least 1 reserved hole is arranged in the pier 1, and when the interconnection through holes 4 are influenced by environmental abnormal factors (such as dust fall, oil stain fall, and the like) to cause that the interconnection through holes 4 cannot maintain a normal working state, the reserved holes can be used as backup interconnection through holes to replace a main interconnection through hole to work, so that the normal operation of the pixel structure is maintained.

Taking fig. 4 as an example of a preferred embodiment of the present invention, the pier 1 is of a flat structure, in which 3 interconnection through holes 4 are arranged, and at least 1 interconnection through hole 4 exists in each pier 1 as a reserved hole; when the connection point of the thermosensitive element 5 and the bridge pier 1 are at similar horizontal positions, the bridge arms 3 are bent and distributed in an incremental arithmetic progression mode, the lengths of two adjacent bent bridge arms are fixed with a difference delta, so that the length of the bending moment arm close to the thermosensitive element 5 is larger than that of the bending moment arm close to the bridge pier 1, the integral anti-vibration capability of the pixel structure is enhanced, and the stability is improved.

The preferred embodiment can be implemented using state-of-the-art MESM technology, such as surface micromachining and bulk micromachining.

The embodiment of the invention provides a novel infrared thermal imaging sensor pixel structure and an infrared thermal imaging sensor, wherein gaps between adjacent piers are increased through piers designed in a flat structure, the accommodating length of a bridge arm 3 is further increased, the thermal conductivity of the pixel structure is reduced, and the noise of the pixel structure is reduced, so that NETD indexes are improved.

The above description is only exemplary of the present invention and should not be taken as limiting the scope of the present invention, and any modifications, equivalents, improvements, etc. that are within the spirit and principle of the present invention should be included in the present invention.

Claims

1. An infrared thermal imaging sensor pixel, comprising at least: the bridge structure comprises a bridge pier (1), an absorption layer (2), a bridge arm (3), an interconnection through hole (4), a thermosensitive element (5) and a substrate ROIC (6), wherein the substrate ROIC (6) is arranged at the bottom of the thermosensitive element (5), and the bridge pier (1) is designed in a flat structure;

each pier (1) is connected with the thermosensitive element (5) through one bridge arm (3); at least one of the interconnecting through holes (4) is arranged inside one of the piers (1);

the absorption layer (2) is positioned on the upper surface of the thermosensitive element (5);

the absorption layer (2) and the thermosensitive element (5) form a bridge deck structure;

each bridge arm (3) is bent to form an array, and the lengths of a plurality of bent sections in the array are arranged in an increasing mode and used for enhancing the anti-vibration performance of the bridge arms (3);

the absorption layer (2) wraps the upper surface of the thermosensitive element (5), and the substrate ROIC (6) is paved below the bridge pier (1), the bridge arm (3) and the thermosensitive element (5) and bears the whole pixels.

2. The infrared thermographic sensor pixel as claimed in claim 1, characterized in that said thermo-sensitive element (5) is connected to at least one of said piers (1) by said bridge arms (3) on both left and right sides, respectively.

3. The infrared thermal imaging sensor pixel according to claim 1, characterized in that at least one reserved hole is included in a plurality of the interconnected vias (4) in each of the piers (1).

4. The infrared thermal imaging sensor pixel as set forth in claim 1, wherein the bending of the legs (3) into a coil length of a plurality of bends in an array comprises: at least one of an arithmetic series, an geometric series, and an exponential distributed arrangement.

5. The infrared thermal imaging sensor pixel of claim 1, characterized in that the bent array shape of the bridge arms (3) comprises: at least one of a U-fold and a V-fold.

6. The infrared thermal imaging sensor pixel according to claim 1 or 2, characterized in that a preset distance is maintained between the piers (1) arranged adjacently above and below on the same side of the thermosensitive element (5).

7. The infrared thermal imaging sensor pixel as recited in claim 1, characterized in that the interconnect via (4) is circular or flat in shape.

8. An infrared thermal imaging sensor comprising a plurality of infrared thermal imaging sensor pixel of any one of claims 1-7, the plurality of pixel elements being arrayed in the infrared thermal imaging sensor.

9. The infrared thermal imaging sensor according to claim 8, characterized in that the meander shape of two neighboring legs (3) in the array of picture elements is complementary.