Infrared heat sensing pixel unit array imaging device and manufacturing method thereof

Abstract

The present invention provides a far-infrared thermal sensing pixel unit array imaging device and a manufacturing method thereof, which is composed of a thermal sensing pixel unit array constructed on a semiconductor substrate; each thermal sensing pixel unit in the array comprises: an upper cavity and a lower cavity that are interconnected, and a sensing unit suspended between the upper cavity and the lower cavity, and the sensing unit is connected to a transistor in the substrate through a first vertical interconnection component and a second vertical interconnection component vertically constructed on the substrate; there are isolation walls between the thermal sensing pixel units, which can not only achieve pixel-level vacuum and microwave crosstalk isolation of the thermal sensing pixel units, but also solve the above-mentioned performance limitations or defects by distinguishing and isolating pixel-level microwaves from the vacuum cavity.

Description

Technical Field

[0001] The present application relates to the field of medical devices, and in particular to an infrared thermal sensing pixel unit array imaging device and a manufacturing method thereof. Background Art

[0002] Uncooled infrared imaging sensors are widely used due to their small size and high sensitivity. Figure 1 FIG. 1 is a partial cross-sectional view of a typical uncooled far-infrared radiation sensing unit array imaging sensor R900. Figure 1 As shown, the infrared absorption and heat sensing sheet 211 of all pixel units R90 and the conductive interconnection bracket R210 connected thereto are all arranged in a completely connected large vacuum cavity R220. At the same time, a whole piece of infrared transparent vacuum cover sheet R300 arranged on the large vacuum cavity R220 first receives the far-infrared radiation electromagnetic waves emitted vertically and at a certain angle from the outside. Therefore, there are at least two direct factors that cause the thermal induction and induction signal crosstalk of the pixel. One is that the electromagnetic waves emitted at a certain angle to the cover are transmitted to the adjacent pixels due to refraction. The other is that the thermal sensing sheet 211 and the conductive interconnection bracket R210 in the pixel emit the electromagnetic waves entering the large cavity R220 vertically and obliquely to the adjacent pixels, and the reflective sheet 120 at the bottom of the large cavity R220 will also produce a small amount of side reflection. Therefore, it is difficult to fundamentally solve the thermal induction and signal crosstalk between pixels of the traditional non-cooled focal plane thermal sensing pixel unit array sensor R900. Because it seriously affects the signal-to-noise ratio of the sensor and the clarity of the imaging.

[0003] In addition, due to the use of low melting point alloys, such as gold and silver, to fuse the vacuum cover to form the vacuum chamber R220 and seal the entire thermal radiation absorption and sensing unit array, there are considerable challenges for large-size and high-resolution imaging sensor chips, and it will seriously affect its processing yield and cost. Summary of the invention

[0004] In order to solve the above-mentioned product performance problems, the present invention provides an infrared thermal sensing pixel unit array imaging device and a manufacturing method thereof.

[0005] A far-infrared thermal radiation sensing unit array imaging sensor is composed of a thermal sensing pixel unit array constructed on a semiconductor substrate; each thermal sensing pixel unit in the array comprises: an upper cavity and a lower cavity that are interconnected, a sensing unit suspended between the upper cavity and the lower cavity, the sensing unit is connected to a transistor in the substrate through a first vertical interconnection component and a second vertical interconnection component vertically constructed on the substrate; and an isolation wall is provided between the thermal sensing pixel units.

[0006] The far-infrared thermal sensing pixel unit array imaging sensor and the manufacturing method thereof provided by the present invention can not only realize the pixel-level vacuum and microwave crosstalk isolation of the thermal sensing pixel unit, but also solve the above-mentioned performance limitations or defects by distinguishing and isolating the pixel-level microwave from the vacuum cavity; at the same time, it also provides a complete set of full-crystal-level micro-device processing and vacuum sealing process flow, which can effectively solve the bottlenecks of processing yield and cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0008] Figure 1 is a cross-sectional schematic diagram of an existing uncooled infrared imaging sensor;

[0009] Figure 2 It is a cross-sectional schematic diagram of the infrared heat sensing pixel unit array imaging device of the present invention;

[0010] Figure 3a-3h The schematic diagram of the manufacturing method of the infrared thermal sensing pixel unit array imaging device is shown as a thermal sensing pixel unit as an example;

[0011] Figure 4a-4c The figure is a schematic diagram of another method for manufacturing an infrared thermal sensing pixel unit array imaging device, taking a thermal sensing pixel unit as an example. DETAILED DESCRIPTION

[0012] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0013] In the present invention, unless otherwise specified, the directional words used, such as "upper and lower", generally refer to the upper and lower parts of the device in normal use, and "inside and outside" refer to the outline of the device. In addition, the terms "first, second, third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first, second, third" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined. In the present invention, it is an electrical device, so connection and interconnection both refer to conductive interconnection. Since the accompanying drawings are descriptions of the same device, the same numbers in the drawings represent the same components.

[0014] The specific examples of the present invention are further described in detail below with reference to the accompanying drawings.

[0015] like Figure 2 As shown, the infrared heat sensing pixel unit array imaging device 900 of the present invention is composed of an array of heat sensing pixel units 90 constructed on a silicon semiconductor substrate 100; each heat sensing pixel unit 90 in the array includes:

[0016] The upper hollow cavity 340 and the lower hollow cavity 240 are interconnected, and the sensing unit 315 is suspended between the upper hollow cavity 340 and the lower hollow cavity 240. The sensing unit is connected to the transistor 121 in the substrate 100 through a vertical interconnection component vertically arranged on the substrate. In this embodiment, the semiconductor substrate is a silicon substrate or a substrate of other semiconductor materials, and the transistor is a silicon-based transistor or a transistor of other semiconductor materials. There is an isolation wall between the thermal sensing pixel units 90.

[0017] Figure 2 The cross-sectional schematic diagram of a thermal sensing pixel unit 90 in the infrared thermal sensing pixel unit array imaging device of the present invention is shown in detail.

[0018] Continue to refer Figure 2 A thermal sensing pixel unit 90 is shown. In this embodiment, the isolation wall 510 is honeycomb-shaped and is specifically located between the sensing units 315. The material of the isolation wall 510 is an insulating dielectric material, such as SiO2. The isolation wall 510 includes an upper wall 510a and a lower wall 510b. In one embodiment of the present invention, a metal upper side wall 243 is provided in the isolation wall corresponding to the upper cavity 340, and a metal lower side wall 343 is provided in the isolation wall corresponding to the lower cavity 240. Thus, the upper wall is laterally surrounded by the metal upper side wall 243, and the lower wall is laterally surrounded by the metal lower side wall. At the same time, the upper cavity 340 and the lower cavity 240 and the top surface of the isolation wall 510, as well as the bottom substrate surface of the lower cavity are all covered with a barrier layer 423, the preferred material of which is a Si3N4 film formed by chemical vapor deposition, and the barrier layer is used for protection when removing the sacrificial layer material. Optionally, a metal bottom reflective layer 444 is further provided at the bottom of the lower cavity 240, so that the metal upper side wall 243, the metal lower side wall 343 and the metal bottom reflective layer 444 can further enhance the utilization of the light in the cavity, so that it is further reflected to the thermal sensing pixel unit 90 for recollection.

[0019] The heat sensing pixel units 90 are laterally divided by the isolation wall 510. Each heat sensing pixel unit 90 includes: a sensing unit 315, a first horizontal connecting sheet 311, an infrared transmission window 422 and a microlens 521. The sensing unit 315 is arranged between the upper cavity 340 and the lower cavity 240. The sensing unit 315 is used for infrared radiation absorption and sensing. The upper cavity 340 and the lower cavity 240 are connected to form a vacuum cavity. The sensing unit 315 is suspended between the upper cavity 340 and the lower cavity 240. The first horizontal connecting sheet 311 is connected to the sensing unit 315 and partially horizontally filled into the isolation wall 510 to support and connect the sensing unit 315 suspended between the upper cavity 340 and the lower cavity 240. The sensing unit also includes: a pressure sensitive unit and a pressure sensitive electrical unit arranged at both ends of the pressure sensitive unit; the other end of the pressure sensitive electrical unit is connected to the transistor in the substrate through the first vertical interconnection component and the second vertical interconnection component.

[0020] A CMOS transistor circuit electrically connected to the sensing unit 315 is provided in the substrate below the thermal sensing pixel unit 90 .

[0021] The infrared lens window 422 is placed on the upper cavity 340 and is made of a transparent material, which can transmit light and seal the vacuum cavity formed by the upper cavity and the lower cavity. The microlens 521 is placed on the infrared lens window 422 and has a polymerization effect on the incident infrared radiation. Among them, the infrared lens window 422 includes at least one physical layer release perforation (not shown) forming the upper and lower cavities and a perforation plug 424 that partially fills the perforation to achieve isolation of the upper and lower cavities from the outside.

[0022] The first horizontal connecting sheet 311 is electrically connected to the CMOS transistor 121 in the substrate 100 below the infrared imaging sensor through the second vertical interconnection 224 vertically filled in the isolation wall 510 and the first vertical interconnection 131 in the semiconductor substrate 100, converting the external pressure on the connected infrared transmission window 422 into an induced electrical signal and transmitting it. The isolation wall 510 and the vacuum cavity are both constructed on the substrate. The substrate is a semiconductor silicon substrate.

[0023] A piezoresistive unit 441 composed of N-type or P-type doped semiconductor Si or Ge is provided on the surface of the cavity side of the infrared lens window 422, and is interconnected with the second CMOS transistor 122 in the substrate 100 through a second vertical interconnect 224, for adding the function of sensing external pressure.

[0024] In order to solve the problem of crosstalk or loss between different thermal sensing pixel units in the prior art, the present invention forms an isolation wall 510 between the thermal sensing pixel units 90, so as to effectively collect the reflected and refracted light into the thermal sensing pixel unit, thereby improving the utilization rate and also improving the accuracy.

[0025] The method for forming the thermal sensing pixel unit 90 is described below with reference to FIGS. 3 and 4 .

[0026] refer to Figure 3a~3h As shown, a semiconductor substrate 100 is first provided, in which CMOS transistor devices and interconnection components can be formed.

[0027] Next, a first dielectric layer 111 and a barrier layer 423 located between the first dielectric layers are formed on the semiconductor substrate.

[0028] Next, the first metal layer 101 is deposited on the first dielectric layer 111 and the barrier layer. Since the thickness of the first dielectric layer 111 is greater than that of the barrier layer, a trench region is formed above the barrier layer.

[0029] Next, the first sacrificial layer 103 is filled in the trench region, and a thermal sensing material 102 is formed on the first sacrificial layer and the first dielectric layer around it, so as to form a subsequent sensing unit.

[0030] Next, a second dielectric layer 104 is deposited.

[0031] Next, a transparent medium 105 is deposited.

[0032] Next, a second metal layer 106 is deposited.

[0033] Next, a second sacrificial layer 107 is deposited and etched to form a first through hole 105a in the deposited transparent medium 105 and a second through hole 102a in the thermal sensing material 102. The first through hole and the second through hole are used to remove the first sacrificial layer, the second sacrificial layer and the second dielectric layer in the corresponding area of ​​the first sacrificial layer.

[0034] Next, the first through hole is filled to form an infrared transmission window 422 .

[0035] Finally, a microlens 521 is formed on the infrared transmission window.

[0036] Wherein, the materials of the first metal layer and the second metal layer are Cu.

[0037] Optionally, the step of forming a thermal sensing material 102 on the first sacrificial layer and the first dielectric layer around it to form a subsequent sensing unit may further include forming a pressure-sensitive unit and a pressure-sensitive electrical unit disposed at both ends of the pressure-sensitive unit; the other end of the pressure-sensitive electrical unit is connected to the transistor in the substrate through the first vertical interconnection component and the second vertical interconnection component. For example, after forming the first sacrificial layer, the pressure-sensitive unit and the pressure-sensitive electrical units at both ends of the pressure-sensitive unit may be formed thereon, and then the thermal sensing material 102 may be formed on the pressure-sensitive unit.

[0038] Optionally, after forming the second dielectric layer 104, a piezoresistive unit 441 is formed in a region corresponding to the first sacrificial layer on the second dielectric layer, and the piezoresistive unit 441 is formed of an N-type or P-type doped semiconductor Si or Ge, and then a transparent medium 105 is deposited, and the transparent medium 105 covers the piezoresistive unit 441. Thus, after forming the device, a piezoresistive unit 441 composed of an N-type or P-type doped semiconductor Si or Ge is disposed on the surface of the cavity side of the infrared lens window 422, and is interconnected with the second CMOS transistor 122 in the substrate 100 through the second vertical interconnect 224, so as to increase the function of sensing external pressure.

[0039] Finally, the formation Figure 2 The infrared thermal sensing pixel unit array imaging device shown. Since the isolation wall is divided into an upper wall and a lower wall, the best one is composed of a silicon-based medium and a metal, especially metal Cu vertically filled into the medium SiO2. Among them, the lower wall part is made together with the first vertical interconnection member and the second vertical interconnection member, and because the medium is SiO2, it is necessary to form a barrier layer for releasing or removing the sacrificial material on the side surface of the isolation wall 510 and the bottom surface of the lower cavity 240, preferably Si3N4. This process flow and architecture are relatively compatible with the general CMOS back-end BEOL interconnection layer process. In addition to SiO2 or microcrystalline silicon / amorphous silicon or materials commonly used in the BEOL process of CMOS, the sensing unit 315 can also use Ge as a sacrificial layer material because it is compatible with the BEOL manufacturing of CMOS, and other materials can be borrowed from the BEOL manufacturing.

[0040] Attached Figures 4a to 4c The figure is a schematic diagram of another method for manufacturing an infrared thermal sensing pixel unit array imaging device, taking a thermal sensing pixel unit as an example.

[0041] In the method, as shown in the figure, both the first dielectric layer and the second dielectric layer are replaced with a sacrificial layer material.

[0042] Thus, the sacrificial layer is removed together with the other layer. Then, the surface opening is filled together with the other layer in the process of filling the first through hole, etc. Thus, the metal sidewalls of the upper cavity and the lower cavity are used to surround a vacuum cavity, and also act as an isolation wall for physical isolation.

[0043] The infrared thermal sensing unit array imaging sensor device provided by the present invention has a unique structure of complete radiation isolation and vacuum cavity isolation between 90 thermal sensing unit pixels, as well as a microlens 521 with microwave polymerization effect on the top. Compared with the traditional uncooled focal plane thermal infrared array sensor, it can effectively solve the microwave signal crosstalk between pixels, improve the signal-to-noise ratio of the induced electrical signal and the imaging clarity of the entire imaging sensor.

[0044] The infrared thermal sensing pixel unit array imaging device manufacturing method of the present invention is compatible with the existing semiconductor manufacturing process. Based on the sensing of the 8-12 micron wavelength far-infrared thermal radiation emitted by the target object and the amplification of the acquired electrical signal, analog-to-digital conversion and other signal processing. The infrared thermal imaging device (also called imaging chip) and the matching optical imaging, including the lens device, have extremely wide applications in various fields of human society, from security, medical treatment, transportation, environmental protection to aerospace.

[0045] Compared with compound semiconductor far-infrared imaging sensors such as mercury cadmium telluride that require low-temperature refrigeration to maintain effective hotspot sensing functions and sensitivity, uncooled focal plane infrared sensor unit array imaging sensors based on MEMS micro-electromechanical system micro-basic process and physical structure are the first choice for applications in various fields due to their stronger environmental adaptability, no need for low-temperature refrigeration, integrated integration with silicon-based CMOS signal reading, method, and processing circuit substrate, higher resolution and relatively low manufacturing cost.

[0046] The above descriptions are merely embodiments of the present application and are not intended to limit the patent scope of the present application. Any equivalent structural or equivalent process transformations made using the contents of the specification and drawings of the present application, such as the mutual combination of technical features between the embodiments, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for forming a far-infrared thermal radiation sensing unit array imaging sensor, characterized in that: Includes steps: Providing a semiconductor substrate; forming a first dielectric layer and a barrier layer between the first dielectric layers on a semiconductor substrate; Depositing a first metal layer on the first dielectric layer and the barrier layer, wherein the thickness of the first dielectric layer is greater than that of the barrier layer and a trench region is formed above the barrier layer; Filling the trench region with a first sacrificial layer, and forming a thermal induction material on the first sacrificial layer and a dielectric around the first sacrificial layer; depositing a second dielectric layer; Depositing a transparent medium; depositing a second metal layer; Depositing a second sacrificial layer, and etching the sacrificial layer to form a first through hole in the deposited transparent medium, and a second through hole in the thermal sensing material, and removing the first sacrificial layer, the second sacrificial layer, and the second dielectric layer in the area corresponding to the first sacrificial layer by using the first through hole and the second through hole; Filling the first through hole to form an infrared transmission window; A microlens is formed on the infrared transmission window.

2. The method for forming a far-infrared thermal radiation sensing unit array imaging sensor according to claim 1, characterized in that: The first dielectric layer is used as the lower wall of the isolation wall, and its material is SiO2; the second dielectric layer is used as the upper wall of the isolation wall, and its material is SiO2; the first metal layer and the second metal layer are made of Cu.

3. The method for forming the far-infrared thermal radiation sensing unit array imaging sensor according to claim 1, characterized in that: The method also includes the following steps: after forming the first sacrificial layer, forming a pressure-sensitive unit and pressure-sensitive electrical units at both ends of the pressure-sensitive unit thereon, and then connecting the pressure-sensitive unit to the thermal sensing material.

4. The method for forming the far-infrared thermal radiation sensing unit array imaging sensor according to claim 1, characterized in that: After forming the second dielectric layer, the method further includes forming a piezoresistive unit on the second dielectric layer in an area corresponding to the first sacrificial layer. The piezoresistive unit is composed of N-type or P-type doped semiconductor Si or Ge, and a transparent medium covers the piezoresistive unit.

5. The method for forming the far-infrared thermal radiation sensing unit array imaging sensor according to claim 1, characterized in that: The materials of the first dielectric layer and the second dielectric layer are sacrificial layer materials; and the step of removing the first sacrificial layer and the second sacrificial layer also includes removing the sacrificial layer materials.

6. A far-infrared thermal radiation sensing unit array imaging sensor formed by the forming method according to any one of claims 1 to 5, characterized in that: The invention is composed of a thermal sensing pixel unit array arranged on a semiconductor substrate; each thermal sensing pixel unit in the array comprises: An upper cavity and a lower cavity are interconnected, and a sensing unit is suspended between the upper cavity and the lower cavity, wherein the sensing unit is connected to the transistor in the substrate through a first vertical interconnection component and a second vertical interconnection component vertically constructed on the substrate; There are isolation walls between the heat-sensing pixel units.

7. The far-infrared thermal radiation sensing unit array imaging sensor according to claim 6, characterized in that: The upper cavity is covered with a pixel infrared transmission window.

8. The far-infrared thermal radiation sensing unit array imaging sensor according to claim 7, characterized in that: A thermal radiation wave micro-focusing lens is arranged on the pixel infrared transmission window.

9. The far-infrared thermal radiation sensing unit array imaging sensor according to claim 8, characterized in that: A metal upper side wall is arranged in the isolation wall corresponding to the upper cavity; and a metal lower side wall is arranged in the isolation wall corresponding to the lower cavity.

10. The far-infrared thermal radiation sensing unit array imaging sensor according to claim 9, characterized in that: The sensing unit includes: a pressure-sensitive unit and a pressure-sensitive electrical unit arranged at two ends of the pressure-sensitive unit; the other end of the pressure-sensitive electrical unit is connected to the transistor in the substrate through a first vertical interconnection component and a second vertical interconnection component.

11. The far-infrared thermal radiation sensing unit array imaging sensor according to claim 10, characterized in that: The surface of the bottom semiconductor substrate is covered with a barrier layer, the material of which is a Si3N4 film.

12. The far-infrared thermal radiation sensing unit array imaging sensor according to claim 11, characterized in that: A metal bottom reflection layer is also arranged at the bottom of the lower hollow cavity.

13. The far-infrared thermal radiation sensing unit array imaging sensor according to claim 12, characterized in that: A piezoresistive unit composed of N-type or P-type doped semiconductor Si or Ge is arranged on the surface of one side of the cavity of the infrared lens window.

14. The far-infrared thermal radiation sensing unit array imaging sensor according to claim 13, characterized in that: The isolation wall is a metal side wall.

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