阅读说明：本技术 一种红外热成像传感器像元及红外热成像传感器 (Infrared thermal imaging sensor pixel and infrared thermal imaging sensor ) 是由 李成强 于 2021-09-01 设计创作，主要内容包括：本发明提供一种红外热成像传感器像元及红外热成像传感器,涉及传感器像元领域,包括：桥墩、桥臂、桥面、互连通孔、热敏电阻以及释放孔；所述像元结构整体呈现夹心式叠层结构,所述顶铝处于所述像元结构最底层,所述桥面处于所述像元结构最顶层,所述桥墩、桥臂、互连通孔以及所述热敏电阻均处于所述叠层结构内部。通过夹心式叠层结构设计加大热敏电阻可排布面积,提高了整体像元结构利用率,并降低了材料的闪烁噪声。结合桥臂所用折叠式排布,在有限空间内进一步加大桥臂长度,进而降低了像元结构热导,提升了像元结构整体响应率。另外,中心释放孔的设计,在不破坏热敏电阻的情况下,优化了PI牺牲层在燃烧过程中对于PI胶的释放。(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 piers, bridge arms, a bridge deck, interconnection through holes, thermistors and release holes; the pixel structure integrally presents a sandwich type laminated structure, the top aluminum is positioned at the bottommost layer of the pixel structure, the bridge floor is positioned at the topmost layer of the pixel structure, and the bridge pier, the bridge arm, the interconnecting through hole and the thermistor are all positioned inside the laminated structure. The sandwich type lamination structure design increases the arraying area of the thermistor, improves the utilization rate of the whole pixel structure and reduces the flicker noise of the material. The length of the bridge arm is further increased in a limited space by combining with the folding arrangement of the bridge arm, so that the thermal conductivity of the pixel structure is reduced, and the overall response rate of the pixel structure is improved. In addition, the design of the central release hole optimizes the release of PI glue in the combustion process of the PI sacrificial layer under the condition of not damaging the thermistor.)

1. An infrared thermal imaging sensor pixel, comprising at least: the bridge comprises a top aluminum (1), piers (2), bridge arms (3), a bridge deck (4), interconnection through holes (5) and thermistors (6);

the pixel structure integrally presents a sandwich type laminated structure, the top aluminum (1) is positioned at the bottommost layer of the pixel structure, the bridge deck (4) is positioned at the topmost layer of the pixel structure, and the bridge pier (2), the bridge arm (3), the interconnection through hole (5) and the thermistor (6) are all positioned inside the laminated structure.

2. The infrared thermal imaging sensor pixel of claim 1, characterized in that the bridge piers (2) are arranged on the upper surface of the top aluminum (1), the upper edges of the bridge piers (2) are connected with the bridge arms (3), and the upper surfaces of the bridge arms (3) are provided with the interconnection through holes (5).

3. The infrared thermal imaging sensor pixel according to claim 1, characterized in that the interconnection via (5) penetrates the thermistor (6), an inner sputtered deposited metal is arranged inside the interconnection via (5), and the thermistor (6) is connected with the bridge arm (3) through the inner sputtered deposited metal.

4. The infrared thermal imaging sensor pixel as recited in claim 1, further comprising a structural contact hole (7) and a release hole (8), wherein the contact hole (7) is disposed on the upper surface of the thermistor (6), and the arrangement position of the release hole (8) comprises the periphery and the central device-free area of the thermistor (6).

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, a V-fold, and a wave-fold.

6. The infrared thermal imaging sensor pixel of claim 1, characterized in that 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.

7. The infrared thermal imaging sensor pixel of claim 1, characterized in that the thermistor (6) has a segmented structure, the shape comprising at least a flat shape.

8. The infrared thermal imaging sensor pixel as recited in claim 1, characterized in that the contact hole (7) design profile comprises: round and flat.

9. An infrared thermal imaging sensor, characterized in that the infrared thermal imaging sensor comprises a plurality of picture elements according to any one of claims 1 to 8, the plurality of picture elements being organized in an array in the infrared thermal imaging sensor.

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

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 the 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 been miniaturized, highly integrated, and mass-produced, and developed in the direction of large area array and small pixel, but the reduction of pixel size leads to the reduction of thermistor area, 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 good response rate, increasing the length of the bridge arm is a feasible method, but simply increasing the length of the bridge arm can reduce the filling rate of the pixel structure.

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 pixel structure of a novel infrared thermal imaging sensor is needed, which can ensure the increase of the absorption amount of infrared radiation and the reduction of the thermal conductivity of the whole pixel structure on the premise of ensuring that the pixel structure can obtain a larger filling rate.

Disclosure of Invention

The embodiment of the invention provides an infrared thermal imaging sensor pixel and an infrared thermal imaging sensor, which can reduce the flicker noise of materials, reduce the thermal conductivity, improve the response rate, improve the NETD index of the whole pixel structure and realize wide application.

In order to solve the above problem, a first aspect of an embodiment of the present invention provides an infrared thermal imaging sensor pixel, including: the bridge comprises a top aluminum 1, piers 2, bridge arms 3, a bridge deck 4, interconnection through holes 5 and thermistors 6;

the pixel structure integrally presents a sandwich type laminated structure, the top aluminum 1 is positioned at the bottommost layer of the pixel structure, the bridge deck 4 is positioned at the topmost layer of the pixel structure, and the bridge pier 2, the bridge arm 3, the interconnection through hole 5 and the thermistor 6 are all positioned inside the laminated structure.

In some embodiments, the bridge piers 2 are arranged on the upper surface of the roof aluminum 1, the upper edges of the bridge piers 2 are connected with the bridge arms 3, and the upper surfaces of the bridge arms 3 are provided with the interconnection through holes 5.

In some embodiments, the interconnection via 5 penetrates through the thermistor 6, an inner sputtered metal is disposed inside the interconnection via 5, and the thermistor 6 is connected with the bridge arm 3 through the inner sputtered metal.

In some embodiments, the pixel structure further comprises a structure contact hole 7 and a release hole 8, the contact hole 7 is arranged above the thermistor 6, and the arrangement position of the release hole 8 comprises the periphery and the central device-free area of the thermistor 6.

In some embodiments, the pixel structure further comprises a PI sacrificial layer inside.

In some embodiments, the legs 3 are bent to form an array, and the bent array of legs 3 at least comprises: u-shaped folding, V-shaped folding and wave-shaped folding.

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 thermistor 6 is segmented and includes at least a flat shape.

In some embodiments, at least one contact hole 7 is disposed above the thermistor 6.

In some embodiments, the interconnect vias 5 may be at least circular or flat in shape.

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

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 with a sandwich type laminated structure and an infrared thermal imaging sensor. The bridge arm length is further increased in an enlarged space by combining with the folding arrangement of the bridge arm, so that the thermal conductivity of the pixel structure is reduced, the overall response rate of the pixel structure is improved, and the NETD index is improved. By the reactive magnetron sputtering method, the thermistor film with high sheet Resistance (Rs) and high TCR (Temperature Coefficient Of Resistance) is relatively easy to realize, and meanwhile, better Resistance uniformity and consistency can be ensured. Through the design of the sectional type thermistor, the pixel structure can be ensured to obtain a smaller resistor, and meanwhile, the resistance consistency is ensured. In addition, the design of the internal release holes improves the release of PI glue in the combustion process of the PI sacrificial layer, and reduces the risk of glue stain residue. The pixel has clear integral structure lamination, does not need to be supported by a complex MEMS technology in the preparation process, and has universality in application.

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 view of a pixel structure lamination of a sandwich lamination structure according to an embodiment of the invention;

FIG. 4 is a schematic structural diagram of a bridge arm with a bent arrangement structure according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of a bent bridge arm and a bridge deck according to an embodiment of the present invention.

Fig. 6 is a schematic diagram of the arrangement of a bending bridge arm and a thermistor layer according to an embodiment of the invention.

FIG. 7-a is a schematic diagram of a segmented thermistor structure and connection according to an embodiment of the invention.

FIG. 7-b is a schematic diagram of a segmented thermistor structure and a connecting circuit according to an embodiment of the invention.

FIG. 8 is a schematic view of an arrangement of release holes according to an embodiment of the present invention. FIG. 9 is a schematic illustration of bridge arm length dimensions according to a preferred embodiment of 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 drawings in the embodiments of the present application, and it is apparent 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 figure 1, bridge arms are designed in an L shape, a single pixel bridge deck carries two shared circular piers which are arranged in a centrosymmetric mode, and each circular pier is connected with the bridge deck through an independent bridge arm. Nowadays, with the development of the MEMS technology, the infrared thermal imaging sensor has been miniaturized, highly integrated, and mass-produced. In recent years, the infrared thermal imaging sensor has realized the evolution of the pixel size from 17 μm to 8 μm, and continues to develop towards the large area array, small pixel, low NETD index. However, in the background of the existing L-shaped pixel structure design, the reduction of the area of the thermistor is brought by the simple reduction of the area of the pixel, which causes the flicker noise of the material for preparing the thermistor to be increased, and meanwhile, the reduction of the area of the pixel has negative effects on the length and the filling rate of the bridge arm.

In order to ensure that excellent NETD indexes are obtained and that the lower the NETD value is, the better the NETD value is, a common direct means in the industry is to reduce the noise of the whole pixel structure and improve the response rate of the pixel structure. The noise reduction mode needs to be realized by increasing the area of the thermistor, and the higher the consistency of the resistance value of the thermistor under large area is, the better the consistency is; the method for improving the response rate of the pixel structure needs to increase the length of the bridge arm of the pixel structure. However, no matter the area of the thermistor is increased or the bridge arm length of the pixel structure is increased, the two means for optimizing the NETD index are contrary to the trend of miniaturization development of the whole structure of the pixel under the condition of the current-stage pixel structure foundation.

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 uses photoetching, film deposition, sputtering, etching, cleaning, scribing, packaging and the like as basic process steps to carry out micro-processing on three-dimensional shapes of semiconductors, the processing dimension is different from nanometer to millimeter, but the existing MEMS plane process is difficult to support the wide application of the improvement technology because the cross section of a bridge arm is in a special shape such as a continuous trapezoidal waveform or a sawtooth shape.

As shown in fig. 3, a pixel element of a sandwich type stacked structure according to an embodiment of the present invention includes: the bridge comprises a top aluminum 1, piers 2, bridge arms 3, a bridge deck 4, interconnection through holes 5, thermistors 6 and contact holes 7; the pixel structure integrally presents a sandwich type laminated structure, the top aluminum 1 is positioned at the bottommost layer of the pixel structure, the bridge deck 4 is positioned at the topmost layer of the pixel structure, and the piers 2 are arranged on the upper surface of the top aluminum structure;

the upper edge of the bridge pier 2 is connected with the bridge arm 3, and the upper surface of the bridge arm 3 is provided with the interconnection through hole 5;

the interconnection through hole 5 penetrates through the upper surface of the thermistor 6, and the interconnection through hole 5 is connected with the bridge arm 3;

the contact hole 7 is arranged above the thermistor 6, and the upper surface of the contact hole 7 is covered by the bridge deck 4.

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 for the bridge pier 2, the bridge arm 3 is arranged in a bent shape, as shown in fig. 4. According to a thermal resistance calculation formula theta which is L/(lambda S) (lambda is the heat conductivity coefficient, L is the material thickness or length, and S is the heat transfer area), the blocking capacity of an object to heat flow conduction is in direct proportion to the length of a conduction path under the condition of fixed heat conductivity coefficient 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 published DOE (design Of experience) conclusion, it can be known that 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 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 NETD can be, and the NETD index is improved (the smaller the NETD is, the better the value Of NETD index is expected to be, the lower the value Of NETD index is).

Alternatively, in some embodiments, the coil arrangement mode of the plurality of bent segments of the bridge arm 3 bent to form the array may be an incremental arrangement or a decreasing arrangement.

Optionally, in some embodiments, the bending array of the bridge arms 3 is bent transversely, as shown in fig. 4, or alternatively, it is bent longitudinally, as shown in fig. 5.

In one embodiment of the invention, the filling rate of the whole pixel structure and the absorption area of infrared heat radiation are ensured to be as large as possible. The bridge arm 3 and the bridge deck 4 are designed to have a laminated structure so that they are not at the same level, as shown in fig. 5. Ensures that the bridge deck 4 is used as an absorption layer and has a sufficiently large filling rate.

Optionally, in some embodiments, the deck 4 is in a laminated space above the bridge arms 3.

In one embodiment of the invention, the area of the thermistor 6 in the pixel structure is as large as possible. The bridge arm 3 and the thermistor 6 are designed to have a laminated structure so that they are not at the same level as shown in fig. 6. The thermistor is ensured to have a sufficiently large arrangement space.

Alternatively, in some embodiments, the thermistor 6 is disposed above the interconnection via 5, and the interconnection via 5 penetrates through the upper surface of the thermistor 6. And is connected with the bridge arm 3 through the interconnection through hole 5.

In an embodiment of the invention, the manufacturing process of the thermistor generally requires that the resistance value of the pixel structure is preferentially ensured to meet the product requirement. A thermistor is a sensor resistor whose resistance value changes with temperature changes. They are classified into Positive Temperature Coefficient thermistors (PTC thermistors) and Negative Temperature Coefficient thermistors (NTC thermistors) according to their Temperature coefficients. The positive temperature coefficient thermistor has a resistance value that increases with an increase in temperature, and the negative temperature coefficient thermistor has a resistance value that decreases with an increase in temperature, which belong to semiconductor devices.

Generally, on the basis that the resistance value of the thermistor meets the product requirement, the higher the TCR capability of the thermistor is, the better the thermistor is. TCR, the temperature coefficient of resistance, represents the relative change in resistance of a resistor when the temperature is changed by 1 degree Celsius, and is reported in ppm/deg.C (i.e., 10)^-6/° c). Has negative temperature coefficient, positive temperature coefficient and critical temperature coefficient with abrupt change of resistance value at a certain temperature. The temperature coefficient of resistance is a parameter closely related to the microstructure of the material, which has a theoretical maximum without any defects.

Optionally, the thermistor material is made of vanadium oxide which is commonly used at the present stage, and is designed to be flat (i.e. the current length flow direction is smaller than the width flow direction).

According to the definition of the sheet resistance Rs, when the length is l, the width is w, the height is d (i.e. the film thickness) and the resistivity is ρ, the sheet resistance Rs is equal to ρ ═ l/(w ═ d) ═ p/d (l/w), and when l is equal to w, the sheet resistance Rs is equal to ρ/d. In the case of a constant resistivity p, generally, the greater the thickness d, the more difficult the process used. Therefore, the thickness d of the thermistor used in the actual preparation process is small, and the smaller d is, the larger the resistance value of the thermistor is, under the condition of constant sheet resistance. Generally, the theoretical thermistor value is the product of the thermistor square resistance Rs and the block number θ, which is physically defined as the ratio of the length to the width of the current flow. In the actual production process, the larger the sheet resistance of the thermosensitive film is, the easier the preparation is, the better the uniformity is, the larger the TCR is, so that on the premise that the required resistance value of the thermistor is a fixed value or a fixed range value (that is, the resistance value of the thermistor meets the product requirement), the smaller the actually required square number θ is, the better the square number θ is, that is, the larger the width of the required current running in the thermistor is, the smaller the length is.

Alternatively, the thermistor structure is configured as a segmented flat shape with an optional number of blocks 1/2, the segmented portions being connected in parallel as shown in fig. 7-a. The current flow through the segmented thermistor (two segments are used as an example here) is equivalent to two thermistors connected in parallel in a circuit, as shown in fig. 7-b. Therefore, the number of the blocks of the segmented thermistor structure can reach at least 1/4 of the number of the blocks of the original integrated thermistor structure with the same area theoretically.

In an embodiment of the invention, in order to ensure that the pixel structure ensures that the PI (polyimide) sacrificial layer is fully released in the subsequent process, the probability of negative influence caused by PI glue remaining in the pixel structure due to insufficient release is reduced. As shown in fig. 8, the release hole 8 is provided above the thermistor 6. The arrangement of the release holes 8 can ensure that oxygen plasma can sufficiently circulate in the release process of the PI sacrificial layer, so as to help the PI sacrificial layer to burn sufficiently. Since the release hole 8 is not located on the plane of the thermistor 6, the setting process does not affect the structural arrangement of the thermistor 6.

Optionally, the upper surface of the release hole 8 covers the bridge deck 4.

Optionally, the number of the release holes 8 is at least 1.

In a preferred embodiment of the present invention, a pixel structure of 14 microns is designed as an example. The length of the single-side bridge arm 3 is 144.244 micrometers, the area calculation filling rate can reach 90.39%, and the effective area of the thermistor 6 is 80.6 micrometers². As shown in FIG. 1, in the prior art, the length of the single-side bridge arm is 27.53 μm, the filling rate is 66%, and the effective area of the thermistor is 70 μm². Through comparison of the two, the improved pixel bridge arm is 5.24 times that of the prior art, the improved filling rate is 1.37 times that of the prior art, and the effective area of the thermistor is 1.15 times that of the prior art. The comparison result shows that the bridge arm length, the filling rate and the effective area of the thermistor of the pixel structure are superior to those of the prior art, and the influence is that the bridge arm length is increased, so that the thermal conductivity is reduced, the response rate of the whole structure is improved, the area of the thermistor is increased, the flicker noise of the material is reduced, and the excellent NETD index is obtained. .

The preferred embodiments can be implemented by state-of-the-art MEMS technology such as surface micromachining and bulk micromachining.

The embodiment of the invention provides a pixel with a sandwich type laminated structure and an infrared thermal imaging sensor. The bridge arm length is further increased in an enlarged limited space by combining with the folding arrangement of the bridge arm, so that the thermal conductivity of the pixel structure is reduced, the overall response rate of the pixel structure is improved, and the NETD index is improved. In addition, by the reactive magnetron sputtering method, the thermistor film with high sheet Resistance (Rs) and high TCR (Temperature Coefficient Of Resistance) is relatively easy to realize, and meanwhile, better Resistance uniformity and consistency can be ensured. Meanwhile, through the design of the sectional thermistor, the pixel structure can be ensured to obtain a smaller resistor, and the resistance consistency is ensured. In addition, the design of the internal release holes improves the release of PI glue in the combustion process of the PI sacrificial layer, and reduces the risk of glue stain residue. The pixel has clear integral structure lamination, does not need to be supported by a complex MEMS technology in the preparation process, and has universality in application.

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.