CN112393806A

CN112393806A - Heterogeneous integrated thermal infrared sensing element and thermal infrared sensor

Info

Publication number: CN112393806A
Application number: CN202010709601.5A
Authority: CN
Inventors: 周正三
Original assignee: Individual
Current assignee: Individual
Priority date: 2019-08-12
Filing date: 2020-07-22
Publication date: 2021-02-23
Also published as: CN212539430U; TW202120893A

Abstract

A heterogeneous integrated thermal infrared sensing device comprises: a substrate; a sensing circuit in or on the substrate; a cavity in or on the substrate, the sensing circuit being located below the cavity; and one or more thermocouples made of a material and transferred above the cavity in a bonding manner, wherein the thermocouples comprise a first conductor and a second conductor, the first ends of the first conductor and the second conductor of the thermocouples are connected to a hot end located above the cavity, and the second ends of the first conductor and the second conductor of the thermocouples are cold ends arranged at the edge of the cavity and are electrically connected to the sensing circuit.

Description

Heterogeneous integrated thermal infrared sensing element and thermal infrared sensor

Technical Field

The present invention relates to a thermal infrared sensing device and a thermal infrared sensor, and more particularly, to a heterogeneous thermal infrared sensing device and a thermal infrared sensor.

Background

In recent years, thermal infrared sensing elements such as thermocouples have been used for temperature measurement, which generate a diffusion current by heating a hot end of a junction between conductors to cause a temperature difference between the hot end and a cold end (another junction between the conductors). To eliminate this current spreading, the thermocouple must provide a significant back emf, which is the seebeck voltage. By measuring the magnitude of the seebeck voltage, the temperature difference between the two ends of the thermocouple can be known to correct the temperature. The magnitude of the seebeck voltage is determined by the product of the magnitude of the temperature difference between the two ends and the seebeck coefficient of the two conductors. A plurality of pairs of thermocouples are connected in series to form a thermopile, and therefore, the thermoelectromotive force of the thermopile is equal to the seebeck voltage value of a single thermocouple multiplied by the even number of thermocouples connected in series.

In the current technology, the most commonly used materials are silicon and polysilicon if the thermopile is to be integrated with the semiconductor process. For example, in Complementary Metal-Oxide Semiconductor (CMOS), a polysilicon layer is defined at the front end of a silicon substrate (high temperature process), a Metal layer is defined at the back end, and finally a structure is released, and a portion of the silicon substrate is removed by a sacrificial layer to form a cavity, such as disclosed in taiwan patent No. TW 451260. The disadvantage of this approach is that there is no way to configure the circuitry under the cavity, which is more cumbersome in fabricating the array element because the circuitry can only be placed beside the thermopile, so that the Fill Factor (FF) of each pixel (pixel), the ratio of the area of the sensing part in the pixel to the total area of the pixel, is greatly reduced, where a higher FF indicates a better quality factor (qu-inity factor). Thus, the known art has the disadvantage of low FF, and there is still considerable room for improvement.

Disclosure of Invention

An object of the present invention is to provide a hetero-integrated thermal infrared sensing device and a thermal infrared sensor, which can improve the fill factor, shorten the signal transmission path, improve the signal-to-noise ratio, and effectively prevent the sensing circuit from being affected by the high temperature process required by the polysilicon.

An embodiment of the present invention provides a heterogeneous integrated thermal infrared sensing device, at least comprising: a substrate; a sensing circuit in or on the substrate; a cavity in or on the substrate, the sensing circuit being located below the cavity; and one or more thermocouples made of a material on the second substrate and transferred to the upper part of the cavity by bonding, wherein the or each thermocouple comprises a first conductor and a second conductor, the first ends of the first and second conductors of the thermocouple are connected to a hot end located above the cavity, and the second ends of the first and second conductors of the thermocouple are cold ends arranged at the edge of the cavity and electrically connected to the sensing circuit.

Furthermore, the hetero-integrated thermal infrared sensing device further comprises a first insulating layer disposed on the substrate and covering the cavity as an upper wall of the cavity, wherein a bonding interface is formed between the first insulating layer and the substrate.

Furthermore, a plurality of openings are formed in the first insulating layer, and penetrate through the first insulating layer and are communicated with the cavity.

Furthermore, the first insulating layer is used as the sidewall surface of the cavity.

Further, a material of at least one of the first conductor and the second conductor includes silicon.

Furthermore, a fill factor of the hetero-integrated thermal infrared sensing device is at least greater than 30%.

Furthermore, the sensing circuit at least comprises a transistor device and a metal connection line. The present invention further provides a thermal infrared sensor, which comprises a plurality of thermal infrared sensing elements arranged in a two-dimensional array for sensing thermal images, wherein the plurality of thermal infrared sensing elements share a substrate.

Furthermore, the thermal infrared sensor further comprises: and the cover body layer is provided with a cover body groove and bonded and jointed with the substrate, so that the plurality of thermal infrared sensing elements are accommodated in the cover body groove.

Furthermore, the cover body groove is in a vacuum state or a near vacuum state with less than one atmosphere pressure so as to increase the sensing sensitivity of the plurality of thermal infrared sensing elements.

Furthermore, the thermal infrared sensor further comprises: and the band-pass filtering layer is positioned on the cover body layer and performs band-pass filtering action on the electromagnetic waves entering the groove of the cover body from the outside.

Further, the cover layer includes: a first bonding layer on the substrate; a second bonding layer; the cover body substrate is provided with the cover body groove, a body positioned above the cover body groove and a frame body positioned around the cover body groove, the second jointing layer is positioned on the bottom surface of the frame body, and the second jointing layer is jointed with the first jointing layer.

Through the above embodiments, the thermal infrared sensing device and the thermal infrared sensor are fabricated by bonding two wafers, wherein the lower wafer (the first initial structure) is formed with the circuit and the recess by using the CMOS process (temperature is about 300 to 400 ℃), and the upper wafer (the second initial structure) is formed with the polysilicon process (temperature is about 600 to 700 ℃), which belong to two wafers formed under different process conditions, and patterning and wiring processes are performed after bonding, so that the situation that the circuit is damaged due to too high process temperature does not occur. Since a circuit can be fabricated below the cavity, FF is very large, and the signal transmission path is shortened, the signal-to-noise ratio is improved. In addition, the heterogeneous integration technology can stack polysilicon requiring high temperature processing on top of the CMOS wafer.

Drawings

FIG. 1A is a top view of a thermal infrared sensor according to a preferred embodiment of the invention.

FIG. 1B is a schematic top view of the thermal infrared sensor of FIG. 1A.

FIG. 1C is a partial top view of the thermal infrared sensor of FIG. 1A.

Fig. 2A to 2J show schematic cross-sectional views corresponding to the line CL-CL in fig. 1B at various steps of the method for manufacturing the thermal infrared sensing element according to the first embodiment.

Fig. 3A to 3L are schematic cross-sectional views corresponding to the line CL-CL in fig. 1B at various steps of the method for manufacturing a thermal infrared sensing element according to the second embodiment.

Fig. 4A to 4H are partially enlarged schematic top views showing structures corresponding to some steps of the method for manufacturing a thermal infrared sensing element according to the second embodiment.

FIG. 5A shows a partial cross-sectional view corresponding to line PL-PL of FIG. 4G.

Fig. 5B shows a partial cross-sectional view of a variation corresponding to fig. 5A.

Fig. 6A is a schematic cross-sectional view illustrating a first variation of the thermal infrared sensor of fig. 1A.

FIG. 6B is a cross-sectional view illustrating a bonding method of the thermal infrared sensor of FIG. 6A.

Fig. 6C is a schematic cross-sectional view illustrating a second variation of the thermal infrared sensor of fig. 1A.

Fig. 7A to 7D are schematic cross-sectional views corresponding to the line CL-CL in fig. 1B at various steps of the method for manufacturing a thermal infrared sensing element according to the third embodiment.

Fig. 8A and 8B are schematic cross-sectional views illustrating a variation of fig. 7A and 7B.

Fig. 9A to 9D are schematic cross-sectional views corresponding to the line CL-CL in fig. 1B at various steps of the method for manufacturing a thermal infrared sensing element according to the fourth embodiment.

Fig. 10A and 10B are schematic cross-sectional views illustrating a variation of fig. 9A and 9B.

Reference numerals

CJ: a cold end; CJW: a cold end window; CL-CL, PL-PL: a wire; HJ: a hot end; HJW: a hot end window; 10: a substrate; 12: a sensing circuit; 14: a cavity; 14S: a sacrificial layer; 14U: an upper wall surface; 14W: a side wall surface; 15: a bonding interface; 16: a protective bonding layer; 20, 20': a first insulating layer; 22: an opening; 30: a thermocouple; 32: a first conductor; 34: a second conductor; 40: a second insulating layer; 50: a protective layer; 50A: a first sub-protective layer; 50B: a second sub-protective layer; 60: a black body layer; 70: a connecting conductor; 100: a thermal infrared sensing element; 200: a thermal infrared sensor; 300: a first initial structure; 340: a second conductor layer; 400: a second initial configuration; 410: a second substrate; 432: a first conductor layer; 434: a second conductor layer; 440: a dielectric layer; 450: a second dielectric layer; 500: a cover layer; 501: a first bonding layer; 502: a second bonding layer; 510: a groove of the cover body; 515: a body; 516: an oxide layer; 520: a frame body; 521: a bottom surface; 522: a top surface; 530: a cover substrate; 600: a band-pass filter layer.

Detailed Description

In order to make the aforementioned and other objects of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.

The spirit of the present invention is to use heterogeneous integration technology, which uses the front-end process of integrated circuit (especially CMOS) to form the circuit (containing multi-layer metal layer) in the wafer, and then defines a groove or cavity or predetermined sacrificial layer structure on the wafer by the back-end process. Then, a wafer bonding technique is used to bond the two wafers together, and then material removal, patterning and connection processes are performed to manufacture the thermal infrared sensing device or the thermal infrared sensor (array device).

FIG. 1A is a top view of a thermal infrared sensor according to a preferred embodiment of the invention. As shown in fig. 1A, a thermal infrared sensor 200 comprises a plurality of thermal infrared sensing elements 100 arranged in a two-dimensional array for sensing a thermal image, the thermal infrared sensing elements 100 share a substrate 10, such as a silicon substrate, and a plurality of thermal infrared sensors 200 can be produced on a silicon wafer, and each thermal infrared sensor 200 is formed by cutting.

FIG. 1B is a schematic top view of the thermal infrared sensor of FIG. 1A. FIG. 1C is a partial top view of the thermal infrared sensor of FIG. 1A. As shown in fig. 1B and 1C, the thermal infrared sensor 100 at least comprises a substrate 10 (besides a semiconductor substrate, an insulating substrate such as a glass substrate, a thin film transistor substrate, etc.), a sensor circuit 12 is formed in the substrate 10, the sensor circuit 12 at least comprises a transistor and a metal connecting wire, the transistor and the metal connecting wire are electrically connected together, and a cavity 14 is formed above the sensor circuit 12. The plurality of thermocouples 30 on the four sides of the cavity 14 are connected together in series and finally electrically connected to an output pad (not shown) or directly to the sensing circuit 12 for the sensing circuit 12 to read out the seebeck voltage or for further processing. For example, first and

second conductors

32 and 34 of one pair of thermocouples 30 are connected to hot side HJ at a thermally insulated region above or directly above cavity 14, and first and

second conductors

32 and 34 of an adjacent pair of thermocouples 30 are connected to cold side CJ in a region of the heat sink outside the thermally insulated region. The black body layer 60 covers the upper portion of the middle hot end HJ to absorb heat, and the heat absorbed by the black body layer 60 cannot be dissipated in the heat insulation region, and can only conduct heat in a solid manner in a direction toward the heat sink region. In the above example, the sensing circuit 12 and the cavity 14 are located in the substrate 10; in another example, the sensing circuit 12 and the cavity 14 may be formed on the substrate 10.

Fig. 2A to 2J are schematic cross-sectional views corresponding to the line CL-CL in fig. 1B at the steps of the method for manufacturing the thermal infrared sensing element according to the first embodiment. As shown in fig. 2A, a first initial structure 300 and a second initial structure 400 are provided. The first initial structure 300 includes a substrate (such as a silicon substrate or a silicon wafer or other substrates) 10 having a sensing circuit 12; and a cavity 14, the sensing circuit 12 being located below or directly below the cavity 14. The second initial structure 400 comprises: a first insulating layer 20; a first conductive layer 432 on the first insulating layer 20; a dielectric layer 440 on the first conductive layer 432; and a second substrate 410, such as a silicon substrate or a silicon wafer or other substrate described above, disposed on the dielectric layer 440.

As shown in fig. 2B, the first insulating layer 20 of the second initial structure 400 and the substrate 10 of the first initial structure 300 are bonded together (by applying pressure and heat), such that the first insulating layer 20 is located on the substrate 10 and covers the cavity 14 to serve as an upper wall 14U of the cavity 14, and a bonding interface (e.g., a wafer bonding interface) 15 is formed between the first insulating layer 20 and the substrate 10, so as to form a stronger chemical bond. The upper wall 14U does not have a wafer bonding interface. It is noted that wafer bonding may be the joining of two wafers to produce a plurality of thermal infrared sensors 200. Another feature of the present invention is that the bonding of the two wafers is blind bonding, which does not require special alignment equipment or techniques, thereby increasing the bonding yield and reducing the cost. Of course, as the alignment bonding technology advances, the present invention may also be applied.

As shown in fig. 2C, the second substrate 410 is removed. As shown in fig. 2D, the dielectric layer 440 is removed. As shown in fig. 2E, the first conductor layer 432 is patterned to form a plurality of first conductors 32 on the first insulating layer 20.

As shown in fig. 2F, a second insulating layer 40 is formed on the first conductors 32 and the first insulating layer 20. As shown in fig. 2G, second insulating layer 40 is patterned to form a plurality of hot side windows HJW and a plurality of cold side windows CJW, in this example, hot side windows HJW and cold side windows CJW are at the same level, i.e., at the same height. As shown in fig. 2H, a second conductive layer 340 is formed on the second insulating layer 40, such that the second conductive layer 340 is electrically connected to the first conductors 32 through the hot side windows HJW and the cold side windows CJW. As shown in fig. 2I, the second conductive layer 340 is patterned to form a plurality of second conductors 34, wherein the first conductors 32 and the second conductors 34 form a plurality of thermocouples 30, the thermocouples 30 are connected in series to form a thermopile (the invention can also be implemented as a single thermocouple 30), each thermocouple 30 includes a first conductor 32 and a second conductor 34 located above the first conductor 32, the first conductor 32 and the second conductor 34 of each thermocouple 30 are connected to a hot end HJ located above the cavity 14, and two adjacent thermocouples 30 are connected to a cold end CJ located away from the cavity 14. In other words, the first ends of the first and

second conductors

32 and 34 of the thermocouple 30 are connected to a hot end HJ located above the cavity 14, and the second ends of the first and

second conductors

32 and 34 of the thermocouple 30 are cold ends CJ disposed at the edge of the cavity 14 and are electrically connected to the sensing circuit 12.

Thus, the steps of fig. 2F to 2I can be summarized as: the thermocouples 30 are formed by using the first conductors 32, the thermocouples 30 are connected together in series to form a thermopile, each thermocouple 30 includes a first conductor 32 and a second conductor 34 located above the first conductor 32, the first conductor 32 and the second conductor 34 of each thermocouple 30 are connected to a hot end HJ located above the cavity 14, and two adjacent thermocouples 30 are connected to a cold end CJ located away from the cavity 14.

Next, as shown in fig. 2J, a protection layer 50 is formed on the second insulating layer 40 and the second conductors 34, covering the hot ends HJ and the cold ends CJ. Of course, a black body layer 60 may be formed on the protection layer 50, and the black body layer 60 covers the hot ends HJ but does not cover the cold ends CJ to absorb heat. The steps of fig. 2C-2J can be generalized to substeps of forming one or more thermocouples (thermopiles) using the second preliminary structure 400.

Referring to fig. 1C and fig. 2J, the method for manufacturing the thermal infrared sensor 100 may further include the following steps: a plurality of openings 22 are formed in the first insulating layer 20 and extend through the first insulating layer 20 to communicate with the cavity 14, thereby increasing the thermal resistance (the higher the thermal resistance is, the better). If the passivation layer 50 also covers the first insulating layer 20, the opening 22 may further penetrate the passivation layer 50.

Therefore, as shown in fig. 2J, 2B and 1C, the hetero-integrated thermal infrared sensing device 100 of the present embodiment includes a substrate 10, a first insulating layer 20, a plurality of thermocouples 30 and a protection layer 50. It should be noted that the first insulating layer 20 and the passivation layer 50 are not necessarily required for implementing the present embodiment, and various configurations are possible. The substrate 10 has a sensing circuit 12 and a cavity 14, the sensing circuit 12 being located below or directly below the cavity 14. The first insulating layer 20 is disposed on the substrate 10 and covers the cavity 14 as an upper wall 14U of the cavity 14, and a bonding interface 15 is formed between the first insulating layer 20 and the substrate 10. Thermocouples 30 are connected together in series to form a thermopile, each thermocouple 30 includes a first conductor 32 and a second conductor 34 positioned above the first conductor 32, the first conductor 32 and the second conductor 34 of each thermocouple 30 are connected to a hot end HJ positioned above the cavity 14, and two adjacent thermocouples 30 are connected to a cold end CJ remote from the cavity 14. The protective layer 50 covers the hot ends HJ and the cold ends CJ. The thermal infrared sensor 100 may further include a black body layer 60 on the passivation layer 50 and covering the hot ends HJ but not the cold ends CJ for absorbing heat. The second conductors 34 are located over the first conductors 32 with a second insulating layer 40 therebetween. Furthermore, a plurality of openings 22 are formed in the first insulating layer 20, penetrating the first insulating layer 20 and communicating with the cavity 14. The first conductor 32 is made of a material such as polysilicon, for example, P/N type polysilicon. The material of the second conductor 34 is, for example, metal. Hot side H J and cold side CJ are electrically connected to sensing circuit 12. In this case, the sensing circuit 12 may include a plurality of active and/or passive devices and metal connection lines for electrical connection, such as MOS devices and metal wires, to form a circuit system (circuit). Since the Circuitry (circuit) is damaged by high temperature during the high temperature process of polysilicon, the sensing circuit 12 of this embodiment is not damaged because it is not subjected to the high temperature process of polysilicon. That is, the sensing circuit 12 and the polysilicon are formed at different stages (different wafers) and then bonded together using wafer bonding techniques. The sensing circuit 12 may also be buried within the substrate 10 and not exposed to the cavity 14 for protection. In addition, the sensing circuit 12 may be electrically connected to the thermocouple 30 through a metal wire, and the horizontal direction area of the sensing circuit 12 may be greater than, equal to, or less than the horizontal direction area of the cavity 14. In addition, the cavity 14 is formed in the substrate 10, and the thermal infrared sensing element 100 may also be regarded as including the cavity 14. As can be seen from the above, the material of the thermocouple 30 (the material of the first conductive layer 432) is formed on another substrate (the second substrate 410) and transferred above the cavity 14 by bonding.

Fig. 3A to 3L are schematic cross-sectional views corresponding to the line CL-CL in fig. 1B at various steps of the method for manufacturing the thermal infrared sensing element according to the second embodiment. Fig. 4A to 4H are partially enlarged schematic top views showing structures corresponding to some steps of the method for manufacturing a thermal infrared sensing element according to the second embodiment. As shown in fig. 3A, a first initial structure 300 and a second initial structure 400 are provided, the first initial structure 300 includes a substrate 10 having a sensing circuit 12 and a cavity 14, the sensing circuit 12 is located below or directly below the cavity 14. The substrate 10 can be used to form the sensing circuit 12 and the cavity 14, which is easily achieved in semiconductor manufacturing. The sensing circuit 12 includes metal interconnects in addition to circuitry. The substrate 10 may also have a thin insulating layer (not shown), such as a silicon dioxide layer, thereon.

The second initial structure 400 comprises: a first insulating layer 20; a first conductive layer 432, which can be single crystal silicon, polysilicon or other material suitable for a thermocouple, and is located on the first insulating layer 20; a dielectric layer 440 on the first conductive layer 432; a second conductive layer 434, which may be monocrystalline silicon, polycrystalline silicon, or other material suitable for a thermocouple, is disposed on the dielectric layer 440; a second dielectric layer 450 on the second conductive layer 434; and a second substrate 410 on the second dielectric layer 450, i.e. the second substrate 410 is located above the dielectric layer 440. Therefore, the second substrate 410 can be used to sequentially form the second dielectric layer 450, the second conductive layer 434, the dielectric layer 440, the first conductive layer 432 and the first insulating layer 20, and then the second initial structure 400 is inverted to the state shown in fig. 3A. The second dielectric layer 450, the second conductive layer 434, the dielectric layer 440, the first conductive layer 432 and the first insulating layer 20 are all monolithic structures, so that the first initial structure 300 and the second initial structure 400 do not need to be precisely aligned.

As shown in fig. 3B, the first insulating layer 20 of the second initial structure 400 and the substrate 10 of the first initial structure 300 are bonded together, such that the first insulating layer 20 is located on the substrate 10 and covers the cavity 14 to serve as an upper wall 14U of the cavity 14, and a bonding interface 15 is formed between the first insulating layer 20 and the substrate 10, similar to the embodiment of fig. 2B. As can be seen from the above, the material of the thermocouple 30 (the material of the first conductive layer 432 and the second conductive layer 434) is fabricated on another substrate (the second substrate 410) and transferred above the cavity 14 by bonding.

As shown in fig. 3C and 3D, the second substrate 410 and the second dielectric layer 450 are removed, and the top view at this time corresponds to fig. 4A, in which only a portion of the cavity 14 is shown. As shown in fig. 3E, the second conductive layer 434 is patterned (e.g., using photoresist, exposure, and etching) to form a plurality of second conductors 34 on the dielectric layer 440, which corresponds to fig. 4B in a top view. As shown in fig. 3F, the dielectric layer 440 is patterned to form a second insulating layer 40 on the first conductive layer 432, and the top view corresponds to fig. 4C. As shown in fig. 3G, the first conductive layer 432 is patterned to form a plurality of first conductors 32 on the first insulating layer 20, and the top view at this time corresponds to fig. 4D.

As shown in fig. 3H, a first sub-passivation layer 50A is formed on the first conductors 32, the second conductors 34 and the first insulating layer 20, and the top view at this time corresponds to fig. 4E, it should be noted that, without confusion, only a portion of the first sub-passivation layer 50A is drawn (not covering all of the first insulating layer 20 yet). As shown in fig. 3I, the first sub-passivation layer 50A is patterned to form a plurality of hot side windows HJW and a plurality of cold side windows CJW, the top view of which corresponds to fig. 4F, wherein the hot side windows HJW expose portions of the first insulating layer 20 (not required), the first conductor 32, the second conductor 34, and the second insulating layer 40 (not required). As shown in fig. 3J, a plurality of connecting conductors 70 are formed in the hot side windows HJW and the cold side windows CJW, the second conductors 34 are electrically connected to the first conductors 32 through the hot side windows HJW and the cold side windows CJW to form a plurality of thermocouples 30, the thermocouples 30 are connected together in series to form a thermopile, each thermocouple 30 includes the first conductor 32 and the second conductor 34 located above the first conductor 32, the first conductor 32 and the second conductor 34 of each thermocouple 30 are connected to a hot side HJ located above the cavity 14, and two adjacent thermocouples 30 are connected to a cold side CJ located away from the cavity 14, the top view corresponding to fig. 4G. The first conductor 32 is made of a material such as polysilicon, for example, P/N type polysilicon. The second conductor 34 is made of polysilicon, such as N/P-type polysilicon, and has positive/negative seebeck coefficient, which increases the seebeck voltage and increases the sensing sensitivity. It is noted that although hot end HJ is shown as having a steep step shape, hot end HJ should have a more gradual curve shape when actually manufactured.

The steps of FIGS. 3H through 3J can be summarized as follows: the first conductors 32 and the second conductors 34 are used to form a plurality of thermocouples 30, the thermocouples 30 are connected together in series to form a thermopile, each thermocouple 30 comprises a first conductor 32 and a second conductor 34 located above the first conductor 32, the first conductor 32 and the second conductor 34 of each thermocouple 30 are connected to a hot end HJ located above the cavity 14, and two adjacent thermocouples 30 are connected to a cold end CJ located away from the cavity 14. It should be noted that the connecting conductor 70 can also be regarded as a part of the second conductors 34, that is, each second conductor 34 has two sections with different materials, so as to have the comprehensive characteristics capable of being reduced with the structure of fig. 2J.

As shown in fig. 3K, a second sub-passivation layer 50B is formed on the first sub-passivation layer 50A and the connecting conductors 70 (serving as the hot side HJ and the cold side CJ), and the first sub-passivation layer 50A and the second sub-passivation layer 50B form a passivation layer 50 covering the hot side HJ and the cold side CJ, and the top view corresponds to fig. 4H.

As shown in fig. 3L, a black body layer 60 is formed on the protection layer 50, and the black body layer 60 covers the hot ends HJ but does not cover the cold ends CJ to absorb heat. The steps of fig. 3C-3L may be summarized as substeps of forming one or more thermocouples (thermopiles) using the second initial structure 400.

Referring to fig. 1C and 3L, the method for manufacturing the thermal infrared sensor 100 may further include the following steps: a plurality of openings 22 are formed in the first insulating layer 20 and extend through the first insulating layer 20 to the cavity 14, thereby increasing the thermal resistance. If the passivation layer 50 also covers the first insulating layer 20, the opening 22 may further penetrate the passivation layer 50.

FIG. 5A shows a partial cross-sectional view corresponding to line PL-PL of FIG. 4G. As shown in fig. 5A, the connecting conductor 70 or cold junction CJ electrically connects the left second conductor 34 to the right first conductor 32 through the cold junction window CJW of the first sub-shield 50A. This connection is also applicable to the hot-side HJ connection.

Fig. 5B shows a partial cross-sectional view of a variation corresponding to fig. 5A. The structure of fig. 5B is similar to that of fig. 5A, except that the edges of the second insulating layer 40 and the second conductor 34 are aligned, so that the second conductor 34 can be used as a mask for the second insulating layer 40, reducing the number of masks.

Fig. 6A is a schematic cross-sectional view illustrating a first variation of the thermal infrared sensor of fig. 1A. As shown in fig. 6A, the thermal infrared sensor 200 further includes a cover layer 500 having a cover recess 510 and bonded to the substrate 10, such that the plurality of thermal infrared sensing elements 100 are accommodated in the cover recess 510. In one example, the cover recess 510 is in a vacuum state (air pressure of 0) or near vacuum state (air pressure of 0 to 10)^-3Torr (Torr)), i.e., a state of less than one atmosphere, to increase the sensing sensitivity of the plurality of thermal infrared sensing elements 100. The thermal infrared sensor 200 may further include a Band Pass Filter (Band Pass Filter)600 disposed on the cover layer 500 and performing a Band Pass filtering operation on the electromagnetic waves entering the cover groove 510 from the outside, such as passing only infrared rays. In one example, bandpass filter layer 600 has a thickness of 8 to 14 microns and is an infrared filterA wave filter.

FIG. 6B is a cross-sectional view illustrating a bonding method of the thermal infrared sensor of FIG. 6A. As shown in fig. 6B and 6A, the cap layer 500 includes: a first bonding layer 501 on the substrate 10; a second bonding layer 502; a cover substrate 530 having a cover recess 510, a body 515 located above the cover recess 510, and a frame 520 located around the cover recess 510, wherein the second bonding layer 502 is located on a bottom surface 521 of the frame 520, and the second bonding layer 502 is bonded to the first bonding layer 501. In the present example, a top surface 522 of body 515 is bonded together by an oxide layer (e.g., a semiconductor oxide layer of silicon dioxide) 516. In this example, the material of the body 515 is single crystal silicon (wafer), the material of the frame 520 is polysilicon, the first Bonding layer 501 and the second Bonding layer 502 can be aluminum and germanium, the aluminum and the germanium can form Eutectic Bonding (Eutectic Bonding) at about 420 ℃, and the two materials are compatible with CMOS process and more suitable for the integrated design of this embodiment. Alternatively, the first bonding layer may not be present, the silicon material of the substrate 10 itself may be a material serving as a bonding layer, and the material of the second bonding layer may be gold (Au) in this case. In fig. 6B, an oxide layer 516 is formed on the lower surface of the body 515, a polysilicon layer is formed on the lower surface of the oxide layer 516 (a frame 520 is formed after patterning, and a portion shown by a dotted line is removed), the exposed oxide layer 516 is removed, a germanium layer (a second bonding layer 502) is formed on the lower surface of the frame 520, the second bonding layer 502 is bonded to the aluminum layer on the upper surface of the substrate 10, and the process chamber is evacuated to make the lid recess 510 in a vacuum state or a state close to a vacuum state after bonding. The bonding technique may use Wafer Level Chip Scale Package (WLCSP).

Fig. 6C is a schematic cross-sectional view illustrating a second variation of the thermal infrared sensor of fig. 1A. As shown in fig. 6C, the capping layer 500 and the substrate 10 are both formed with an interface having a hydrogen bond strength by a low temperature bonding (low temperature bonding) method. Of course, before forming the low temperature bonding, a surface plasma (plasma) treatment, such as exposure to oxygen, may be further included to achieve surface activationGas (O)₂) And nitrogen (N)₂) In order to obtain a good flatness of the bonded surface, the surface to be bonded can be polished and leveled by Chemical-Mechanical Polishing (CMP). The precursor of the cap layer 500 may be a Silicon On Insulator (SOI) wafer, the lower wafer is etched to form the cap recess 510, the oxide layer 516 is removed, and then the second bonding layer 502 (which may be a Silicon dioxide layer) is bonded to the substrate 10.

As shown in fig. 7A to 7D, a third embodiment of the invention provides a method for manufacturing a hetero-integrated thermal infrared sensing device 100, which includes the following steps. First, as shown in fig. 7A, a first initial structure 300 and a second initial structure 400 are provided. The first initial structure 300 comprises: a substrate 10 having a sensing circuit 12; a sacrificial layer 14S on the substrate 10; and a protective bonding layer 16 covering the sacrificial layer 14S and the substrate 10, wherein the sensing circuit 12 is located under or just under the sacrificial layer 14S. The second initial structure 400 comprises: a first conductive layer 432; a dielectric layer 440 on the first conductive layer 432; and a second substrate 410 on or over the dielectric layer 440. After the protective bonding layer 16 originally covers the sacrificial layer 14S, the desired thickness can be controlled by grinding the protective bonding layer 16 to obtain a flat surface.

Then, as shown in fig. 7B, the substrate 10 and the second substrate 410 are separated from each other, and the second initial structure 400 and the first initial structure 300 are bonded together to obtain a bonded first insulating layer 20', which is located on the substrate 10 and covers the sacrificial layer 14S.

The following steps of the manufacturing method are similar to fig. 2C to 2H, i.e. the thermopile is formed using the second initial structure 400, which is not drawn again here.

Then, as shown in fig. 7C, a plurality of openings 22 are formed on the bonded first insulating layer 20' to expose the sacrificial layer 14S, wherein the material of the sacrificial layer 14S includes but is not limited to aluminum (e.g., silicon material (silicon n) may also be used, etc.). Next, as shown in fig. 7D, the sacrificial layer 14S is removed through the openings 22 to form a cavity 14, such that the cavity 14 is formed on the substrate 10, and the bonded first insulating layer 20' is located on the substrate 10 and covers the cavity 14 to serve as an upper wall surface 14U and a side wall surface 14W of the cavity 14. The openings 22 communicate with the cavity 14 and the external environment, and communicate with the cavity 14 through the first insulating layer 20', thereby increasing the thermal resistance (the larger the thermal resistance is, the better), so that the thermal resistance is not required to be filled. It should be noted that a bonding interface 15 is also formed between the bonded first insulating layer 20' and the substrate 10; in addition, the bonded first insulating layer 20' is also regarded as a first insulating layer in the thermal infrared sensing device 100, and the first insulating layer further serves as the sidewall surface 14W of the cavity 14. At this time, the cavity 14 is formed on the substrate 10. Of course, the sacrificial layer 14S is represented herein as a cavity technology formed by first forming a wafer bond and then removing the sacrificial layer 14S, however, the present invention is not limited thereto, and any method of forming a cavity, such as a cavity formed by a metal silicide, such as NiSi, is within the scope of the present invention as long as the method conforms to the spirit of the technology for heterostructure integration of the present invention.

In detail, the step of forming the thermopile using the second initial structure 400 includes the following sub-steps. As shown in fig. 7B, fig. 2C to fig. 2H (the cavity 14 is regarded as the sacrificial layer 14S), the second substrate 410 and the dielectric layer 440 are first removed; next, patterning the first conductive layer 432 to form a plurality of first conductors 32 on the bonded first insulating layer 20'; then, forming a plurality of thermocouples 30 by using the first conductors 32, the thermocouples 30 being connected together in series to form a thermopile, each thermocouple 30 comprising a first conductor 32 and a second conductor 34 located above the first conductor 32, the first conductor 32 and the second conductor 34 of each thermocouple 30 being connected to a hot end HJ located above the cavity 14, two adjacent thermocouples 30 being connected to a cold end CJ located away from the cavity 14, the hot ends HJ and the cold ends CJ being electrically connected to the sensing circuit 12; next, forming a protection layer 50 on the second conductors 34 to cover the hot ends HJ and the cold ends CJ; then, a black body layer 60 is formed on the protection layer 50, and the black body layer 60 covers the hot ends HJ but does not cover the cold ends CJ to absorb heat.

In addition, the step of forming a plurality of thermocouples 30 using the first conductors 32 includes: forming a second insulating layer 40 on the first conductors 32 and the bonded first insulating layer 20'; patterning the second insulating layer 40 to form a plurality of hot side windows HJW and a plurality of cold side windows CJW; forming a second conductive layer 434 on the second insulating layer 40, such that the second conductive layer 434 is electrically connected to the first conductors 32 through the hot side windows HJW and the cold side windows CJW; and patterning the second conductor layer 434 to form the second conductors 34, wherein the first conductors 32 and the second conductors 34 form a plurality of thermocouples 30, the thermocouples 30 are connected together in series to form a thermopile, each thermocouple 30 comprises a first conductor 32 and a second conductor 34 located above the first conductor 32, the first conductor 32 and the second conductor 34 of each thermocouple 30 are connected to a hot end HJ located above the cavity 14, and two adjacent thermocouples 30 are connected to a cold end CJ located away from the cavity 14.

In fig. 7A and 7B, the second preliminary structure 400 further includes a first insulating layer 20, wherein the first conductive layer 432 is disposed on the first insulating layer 20, and the first insulating layer 20 of the second preliminary structure 400 is bonded to the protective bonding layer 16 of the first preliminary structure 300 to obtain a bonded first insulating layer 20'.

In fig. 8A and 8B, the second preliminary structure 400 does not have the first insulating layer 20, and thus the first conductor layer 432 of the second preliminary structure 400 is bonded to the protective bonding layer 16 of the first preliminary structure 300, so that the protective bonding layer 16 becomes the bonded first insulating layer 20'.

As shown in fig. 9A to 9D (see fig. 3A to 3L, respectively, except that the cavity 14 is regarded as the sacrificial layer 14S), the fourth embodiment of the present invention is similar to the third embodiment, and also provides a method for manufacturing a hetero-integrated thermal infrared sensing device 100, except that the second initial structure 400 further includes: a second conductive layer 434 on the dielectric layer 440; a second dielectric layer 450 on the second conductive layer 434, wherein the second substrate 410 is on the second dielectric layer 450. Thus, the step of forming the thermopile using the second preliminary structure 400 comprises the sub-steps of: removing the second substrate 410 and the second dielectric layer 450; patterning the second conductor layer 434 to form a plurality of second conductors 34 on the dielectric layer 440; patterning the dielectric layer 440 to form a second insulating layer 40 on the first conductive layer 432; patterning the first conductor layer 432 to form a plurality of first conductors 32 on the bonded first insulating layer 20'; forming a plurality of thermocouples 30 by using the first conductors 32 and the second conductors 34, the thermocouples 30 being connected together in series to form a thermopile, each thermocouple 30 comprising a first conductor 32 and a second conductor 34 located above the first conductor 32, the first conductor 32 and the second conductor 34 of each thermocouple 30 being connected to a hot end HJ located above the cavity 14, two adjacent thermocouples 30 being connected to a cold end CJ located away from the cavity 14, the hot ends HJ and the cold ends CJ being electrically connected to the sensing circuit 12, the second conductor 34 being covered by a first sub-protection layer 50A; and forming a second sub-passivation layer 50B on the first sub-passivation layer 50A, the hot end HJ and the cold end CJ, wherein the first sub-passivation layer 50A and the second sub-passivation layer 50B form a passivation layer 50 covering the hot end HJ and the cold end CJ. In addition, the step of forming the plurality of thermocouples 30 using the first conductors 32 and the second conductors 34 includes: forming a first sub-passivation layer 50A on the first conductors 32, the second conductors 34 and the bonded first insulating layer 20'; patterning the first sub-passivation layer 50A to form a plurality of hot side windows HJW and a plurality of cold side windows CJW; and forming a plurality of connecting conductors 70 in the hot side windows HJW and the cold side windows CJW, electrically connecting the second conductors 34 to the first conductors 32 through the hot side windows HJW and the cold side windows CJW to form a plurality of thermocouples 30, the thermocouples 30 being connected in series to form a thermopile, each thermocouple 30 including a first conductor 32 and a second conductor 34 located above the first conductor 32, the first conductor 32 and the second conductor 34 of each thermocouple 30 being connected to a hot side HJ located above the cavity 14, two adjacent thermocouples 30 being connected to a cold side CJ located away from the cavity 14, the hot side HJ and the cold side CJ belonging to the connecting conductors 70.

As shown in fig. 10A and 10B, the present variation example is similar to fig. 9A and 9B, except that the second initial structure 400 of fig. 10A does not have the first insulating layer 20, and thus the first conductor layer 432 of the second initial structure 400 is bonded to the protective bonding layer 16 of the first initial structure 300, so that the protective bonding layer 16 becomes the bonded first insulating layer 20'.

Therefore, the spirit of the embodiments of the present invention is to fabricate the thermal infrared sensing device and the thermal infrared sensor by bonding two wafers, especially blind bonding, wherein the lower wafer (the first initial structure 300) utilizes the CMOS process (temperature about 300 to 400 ℃) to form the circuit and the recess, and the upper wafer (the second initial structure 400) utilizes the polysilicon process (temperature about 600 to 700 ℃) and belongs to two wafers formed under different process conditions, and patterning and wiring processes are performed after bonding, so that the condition that the process temperature is too high to damage the circuit is avoided. The sensing circuit comprises at least a transistor element and a metal connection line, which are destroyed if high temperature processes are encountered during the formation of the first and second conductors of the polysilicon together (the material of at least one of the first and second conductors of the thermocouple comprises high temperature polysilicon). In another example, a single crystal Silicon (SOI) wafer with a Silicon On Insulator (SOI) wafer On an insulating layer may also be used as the material for at least one of the first and second conductors. Since the circuitry (e.g., complete MOS FET plus metal wire circuitry) can be fabricated directly underneath the cavity without being affected by the high temperature processing of the thermocouple material, the Fill Factor (FF) is very large, at least greater than 30% (e.g., 30 micrometer (um) pitch (pitch), 20um cavity length), and even greater than 50%, and the signal transmission path is shortened and the signal-to-noise ratio is improved. In addition, the heterogeneous integration technology can stack polysilicon requiring high temperature processing on top of the CMOS wafer.

The detailed description of the preferred embodiments is provided only for the convenience of illustrating the technical contents of the present invention, and the present invention is not limited to the above-described embodiments in a narrow sense, and various modifications can be made without departing from the spirit of the present invention and the scope of the claims.

Claims

1. A heterogeneous integrated thermal infrared sensor device, comprising:

a substrate;

a sensing circuit in or on the substrate;

a cavity in or on the substrate, the sensing circuit being located below the cavity; and

one or more thermocouples made of a material and transferred to the cavity by bonding on a second substrate, the or each thermocouple comprising a first conductor and a second conductor, the first ends of the first and second conductors of the thermocouple being connected to a hot end located above the cavity, the second ends of the first and second conductors of the thermocouple being cold ends disposed at the edge of the cavity and electrically connected to the sensing circuit.

2. The hetero-integrated thermal infrared sensing device according to claim 1, further comprising a first insulating layer on the substrate and covering the cavity as an upper wall of the cavity, wherein a bonding interface is formed between the first insulating layer and the substrate.

3. The hetero-integrated thermal infrared sensing device according to claim 2, wherein the first insulating layer is formed with a plurality of openings penetrating the first insulating layer and communicating with the cavity.

4. The hetero-integrated thermal infrared sensing device according to claim 2, wherein the first insulating layer further serves as a sidewall surface of the cavity.

5. The hetero-integrated thermal infrared sensing element according to claim 1, wherein a material of at least one of the first conductor and the second conductor comprises silicon.

6. The hetero-integrated thermal infrared sensing device according to claim 1, wherein a fill factor of the hetero-integrated thermal infrared sensing device is at least greater than 30%.

7. The hetero-integrated thermal infrared sensor device as recited in claim 1, wherein the sensing circuit comprises at least a transistor device and a metal connection.

8. A thermal infrared sensor comprising a plurality of hetero-integrated thermal infrared sensing elements of claim 1 arranged in a two-dimensional array for sensing a thermal image, the plurality of hetero-integrated thermal infrared sensing elements sharing the substrate.

9. The thermal infrared sensor of claim 8, further comprising:

and the cover body layer is provided with a cover body groove and bonded and connected with the substrate, so that the plurality of heterogeneous integrated thermal infrared sensing elements are accommodated in the cover body groove.

10. The thermal infrared sensor according to claim 9, wherein the cover recess is under vacuum or near vacuum at a pressure lower than one atmosphere to increase the sensing sensitivity of the plurality of hetero-integrated thermal infrared sensing elements.

11. The thermal infrared sensor of claim 9, further comprising:

and the band-pass filtering layer is positioned on the cover body layer and performs band-pass filtering action on the electromagnetic waves entering the groove of the cover body from the outside.

12. The thermal infrared sensor as defined in claim 9, wherein the cover layer comprises:

a first bonding layer on the substrate;

a second bonding layer; and

the cover body substrate is provided with the cover body groove, a body positioned above the cover body groove and a frame body positioned around the cover body groove, the second jointing layer is positioned on the bottom surface of the frame body, and the second jointing layer is jointed with the first jointing layer.