Far-infrared sensing element and sensor comprising the same

Abstract

A far infrared sensing element and a sensor including the same are disclosed. The far infrared sensing element includes a substrate, a light absorbing layer disposed on the substrate, a sensing layer disposed in the light absorbing layer, an indium tin oxide (ITO) layer, and a conductive plug. The light absorbing layer further has a plurality of contact window openings, and the sensing layer has an extension extending to the contact window openings. The ITO layer is disposed between the light absorbing layer and the substrate, and has a first portion and a plurality of second portions. The first portion is located under the sensing layer as a reflection layer, and the second portions are connected to the extension of the sensing layer as a plurality of arms with the light absorbing layer thereon. The conductive plug connects the arms and an interconnect in the substrate, respectively, and forms a thermal isolation space between the reflection layer and the substrate.

Description

TECHNICAL FIELD

[0001] The present application relates to a far infrared sensing technology, and in particular, to a far infrared sensing element and a sensor comprising the same. BACKGROUND

[0002] Far infrared micro-bolometer is a temperature sensor that converts far infrared rays emitted from human body into an electrical signal output.

[0003] Currently, far infrared micro-bolometers fabricated using micro-electro-mechanical systems (MEMS) technology are available, such as thermoresistive far infrared micro-bolometers using amorphous silicon as a sensing layer.

[0004] However, far infrared micro-bolometers are very sensitive to ambient temperature, so how to block unnecessary temperature conduction has become an important issue. Moreover, in order to achieve environmental insulation, a photoresist-like material, such as polyimide (PI), is usually used as a sacrificial layer in the fabrication process, which causes problems such as difficulty in controlling the thickness and subsequent particle contamination of the deposition machine. SUMMARY

[0005] The present application provides a far infrared sensing element with excellent thermal insulation effect and low fabrication cost.

[0006] The present application further provides a far infrared sensor comprising the above far infrared sensing element.

[0007] The far infrared sensing element of the present application comprises a substrate, a light absorbing layer, a sensing layer, an indium tin oxide (ITO) layer, and a conductive plug. The light absorbing layer is disposed on the substrate, wherein the light absorbing layer has a plurality of contact window openings. The sensing layer is disposed in the light absorbing layer, and the sensing layer has an extension portion extending to the contact window openings. The ITO layer is disposed between the light absorbing layer and the substrate, wherein the ITO layer has a first portion and a plurality of second portions, the first portion is located below the sensing layer as a reflective layer, and the second portions are connected to the extension portion of the sensing layer as a supporting arm with the light absorbing layer above. The conductive plug connects the supporting arm and the interconnect in the substrate, respectively, and forms a thermal insulation space between the reflective layer and the substrate.

[0008] In an embodiment of the present application, the thickness of the ITO layer is in the range of 50-200 nm. The above.

[0009] In an embodiment of the present application, the distance d between the ITO layer and the sensing layer satisfies the following formula (1):

[0010] d = λ / 4n1 Formula (1)

[0011] wherein n1 is the refractive index of the light-absorbing layer, and λ is the wavelength of the absorbed light.

[0012] In an embodiment of the present application, the light-absorbing layer comprises a silicon oxide layer, a silicon nitride layer, or a combination of a silicon oxide layer and a silicon nitride layer.

[0013] In an embodiment of the present application, the light-absorbing layer comprises a first silicon nitride layer on the sensing layer and a first silicon oxide layer on the first silicon nitride layer.

[0014] In an embodiment of the present application, the thickness of the first silicon nitride layer is between 10 nm and 100 nm.

[0015] In an embodiment of the present application, the thickness of the first silicon oxide layer is between 10 nm and 100 nm.

[0016] In an embodiment of the present application, the light-absorbing layer comprises a second silicon nitride layer under the sensing layer and a second silicon oxide layer between the second silicon nitride layer and the reflecting layer.

[0017] In an embodiment of the present application, the thickness t of the second silicon oxide layer satisfies the following equation (2):

[0018] t = λ / 4n2 Equation (2)

[0019] wherein n2 is the refractive index of the second silicon oxide layer, and λ is the wavelength of the absorbed light.

[0020] In an embodiment of the present application, the thickness of the second silicon nitride layer is between 10 nm and 100 nm.

[0021] In an embodiment of the present application, the thickness of the sensing layer is between 10 nm and 100 nm.

[0022] In an embodiment of the present application, the material of the sensing layer comprises amorphous silicon or vanadium oxide (VO x ).

[0023] In an embodiment of the present application, the adiabatic space is filled with nitrogen or air, or the adiabatic space is in a vacuum state.

[0024] ​​​​The far infrared ray sensor of the present application comprises a far infrared ray sensing element and a reference element. The reference element comprises a light-absorbing reference layer, a sensing reference layer, an indium tin oxide (ITO) reference layer, an amorphous silicon sacrificial layer, and a plurality of reference conductive plugs. The light-absorbing reference layer is formed on the substrate, wherein the light-absorbing reference layer has a plurality of contact window openings. The sensing reference layer is formed in the light-absorbing reference layer, and the sensing reference layer has an extension extending to the contact window openings. The ITO reference layer is formed between the light-absorbing reference layer and the substrate, wherein the ITO reference layer has a first portion and a plurality of second portions, the first portion is located below the sensing reference layer as a reflection layer, and the second portions are connected to the extensions of the sensing reference layer. The amorphous silicon sacrificial layer is disposed between the ITO reference layer and the substrate. The reference conductive plugs are formed in the amorphous silicon sacrificial layer and are connected to the second portions and the interconnects in the substrate, respectively.

[0025] Based on the above, by using the ITO layer as a reflection layer and a part of the arm, a better heat insulation effect can be achieved through the ITO layer with low thermal conductivity and high electrical conductivity. Moreover, the distance between the ITO reflection layer and the sensing layer is controlled by the light-absorbing layer, so the light-absorbing layer formed by general deposition can be more easily and accurately controlled in thickness than polymers such as polyimide (PI) to achieve the effect of constructive interference. In addition, the present application can use an amorphous silicon sacrificial layer, so that the problem of particle contamination of subsequent deposition machines can be avoided.

[0026] In order to make the above features and advantages of the present application more obvious and easy to understand, the following specific examples are described in detail below, together with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a top view of a far infrared ray sensing element of a first embodiment of the present application;

[0028] Figure 2 is a cross-sectional view of the II-II' line segment of Figure 1

[0029] Figure 3 is a cross-sectional view of a far infrared ray sensing element of a second embodiment of the present application;

[0030] Figure 4 is a cross-sectional view of a reference element of a far infrared ray sensor of a third embodiment of the present application.

[0031] SYMBOL EXPLANATION

[0032] 100: substrate

[0033] 102: light-absorbing layer

[0034] ​102a, 400a: contact opening

[0035] 104: sensing layer

[0036] 104a, 402a: extension

[0037] 106: indium tin oxide (ITO) layer

[0038] 108: conductive plug

[0039] 110, 418: first portion

[0040] 112, 420: second portion

[0041] 114: thermal isolation space

[0042] 116: release hole

[0043] 302, 410: first silicon nitride layer

[0044] 304, 412: first silicon oxide layer

[0045] 306, 414: second silicon nitride layer

[0046] 308, 416: second silicon oxide layer

[0047] 400: light absorption reference layer

[0048] 402: sensing reference layer

[0049] 404: ITO reference layer

[0050] 406: amorphous silicon sacrificial layer

[0051] 408: reference conductive plug

[0052] d: distance

[0053] t1, t2, t3, t4, t5, t6: thickness DETAILED DESCRIPTION

[0054] The embodiments are illustrated by way of example in the following drawings and detailed description. These embodiments are not provided to limit the scope of the present application, but to explain the principles of the present application. In addition, the accompanying drawings are not drawn to scale. For ease of understanding, the same elements will be marked by the same reference numerals throughout the specification.

[0055] In addition, the terms "comprise", "include", "have" and the like used herein are open-ended terms, i.e., "including but not limited to".

[0056] It should be understood that, although the terms "first", "second", "third", etc. can be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, and / or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Therefore, the "first element", "component", "region", "layer" or "section" discussed below can be referred to as a second element, component, region, layer or section without departing from the teachings herein.

[0057] In addition, directional terms such as "upper", "lower", and the like are used herein for reference only to facilitate discussion of the drawings and are not intended to limit the present application.

[0058] Figure 1 is a top view of a far infrared sensing element according to a first embodiment of the present application. Figure 2 is Figure 1 is a cross-sectional view of the II-II' line segment of

[0059] Please refer to Figure 1 and Figure 2 The far infrared sensing element of the first embodiment includes a substrate 100, a light absorption layer 102, a sensing layer 104, an indium tin oxide (ITO) layer 106, and a conductive plug 108. The substrate 100 is shown as a block, but it is understood that the substrate 100 is typically provided with structures such as transistors (not shown) and interconnects (not shown) for outputting sensing signals (e.g., resistance values) for analysis. The light absorption layer 102 is disposed on the substrate 100 to enhance light absorption. In one embodiment, the light absorption layer 102 includes a silicon oxide layer, a silicon nitride layer, or a combination thereof. The light absorption layer 102 also has a plurality of contact window openings 102a for connection to other elements, such as transistors in the substrate 100. The sensing layer 104 is disposed in the light absorption layer 102, and the sensing layer 104 has an extension 104a extending to the contact window openings 102a. In one embodiment of the present application, the thickness t1 of the sensing layer 104 is, for example, between 10 nm and 100 nm, and the material of the sensing layer 104 includes amorphous silicon (a-Si) or vanadium oxide (VO x ).

[0060] Please refer to Figure 1 and Figure 2 The ITO layer 106 is disposed between the light absorption layer 102 and the substrate 100, where the ITO layer 106 has a first portion 110 and a plurality of second portions 112. Moreover, Figure 1 Although the light absorption layer 102 is not shown in Figure 2 ​It should be known that the light absorption layer 102 is formed above the second part 112 of the ITO layer 106.

[0061] In one embodiment, the thickness t2 of the ITO layer 106 is, for example, in... The first portion 110 is located below the sensing layer 104 as a reflective layer to reflect far-infrared rays that are not absorbed by the light-absorbing layer 102. Therefore, the distance d between the ITO layer 106 and the sensing layer 104 is preferably in accordance with the following formula (1):

[0062] d=λ / 4n1 Equation (1)

[0063] Where n1 is the refractive index of the light-absorbing layer 102, and λ is the wavelength of the absorbed light.

[0064] Since the light-absorbing layer 102 can be formed by deposition, the deposition thickness is easy to control, which helps to ensure that the above distance d conforms to Equation (1) to achieve the effect of constructive interference. The second part 112 of the ITO layer 106 and the light-absorbing layer 102 above it are connected as arms to the extension 104a of the sensing layer 104. The conductive plugs 108 are respectively connected to the internal interconnects (not shown) in the substrate 100 and form a heat-insulating space 114 between the reflective layer (i.e., the first part 110) and the substrate 100. The conductive plugs 108 are, for example, a structure composed of a titanium nitride (TiN) barrier layer plus a tungsten plug. Because far-infrared sensing elements are extremely sensitive to heat, an ITO layer 106 with a low thermal conductivity (~14 W / m / K) is used as part of the support arm, providing better heat insulation. Furthermore, the second portion 112 and the light-absorbing layer 102 can be defined by a release hole 116, designed as a meandering structure to further prevent heat output by increasing the path of heat transfer via the conductive plug 108. Moreover, since the first portion 110 and the second portion 112 are on the same layer, they can be integrated into a single fabrication process. This eliminates the need for additional fabrication processes and photomasks required for reflective layers (such as metal layers) in previous far-infrared sensors (such as IR micro-bolometers), thus significantly reducing manufacturing costs. For example, a sacrificial layer (not shown) is first formed on the substrate 100, and a conductive plug 108 is formed therein. Then, an ITO layer is formed by deposition across the entire structure surface, followed by etching of the ITO layer to define (e.g., Figure 1The sensing layer 104 includes a first portion 110 and a portion of a second portion 112 within a predetermined range, while retaining the ITO layer outside the predetermined range of the sensing layer 104. After the light-absorbing layer 102 and the sensing layer 104 are formed, the position of the release hole 116 can be directly defined by etching, while simultaneously completing the second portion 112 as a support and the light-absorbing layer 102. Subsequently, the sacrificial layer can be completely removed through the release hole 116 to form the thermal insulation space 114. In one embodiment, the thermal insulation space 114 is filled with nitrogen (N2) or contains air; in another embodiment, the thermal insulation space 114 may be in a vacuum state.

[0065] Figure 3 This is a cross-sectional schematic diagram of a far-infrared sensing element according to a second embodiment of the present invention, wherein the same element symbols as in the first embodiment are used to represent the same or similar parts and components, and the relevant content of the same or similar parts and components can also refer to the content of the first embodiment, and will not be repeated here.

[0066] Please refer to Figure 3 The difference between the far-infrared sensing element of the second embodiment and the first embodiment is that the light absorption layer 300 includes a first silicon nitride layer 302 located on the sensing layer 104 and a first silicon oxide layer 304 located on the first silicon nitride layer 302, wherein the thickness t3 of the first silicon nitride layer 302 is, for example, in... Between, the thickness t4 of the first silicon oxide layer 304, for example in Furthermore, the light-absorbing layer 300 also includes a second silicon nitride layer 306 located beneath the sensing layer 104 and a second silicon oxide layer 308 located between the second silicon nitride layer 306 and the reflective layer (i.e., the first portion 110 of the ITO layer 106). The thickness t5 of the second silicon nitride layer 306 is, for example, in... Between these conditions, the thickness t6 of the second silicon oxide layer 308 is preferably in accordance with the following formula (2):

[0067] t=λ / 4n2 Equation (2)

[0068] Where n2 is the refractive index of the second silicon oxide layer 308, and λ is the wavelength of the absorbed light.

[0069] Since the second silicon oxide layer 308 in the light absorption layer 300 can be formed by deposition, the deposition thickness t6 is easily controlled to conform to equation (2) to achieve the effect of constructive interference.

[0070] Furthermore, experimental simulations showed that the overall absorption rate of amorphous silicon sensing layers with only silicon nitride layers (302 and 306) formed above and below the silicon nitride layer was approximately 81.7%. This is further increased by considering the thickness of the lower layer. With the silicon oxide layer (308), the overall absorption rate will increase to 83.1% when both the upper and lower layers have increased thickness. With the addition of silicon oxide layers (304 and 308), the overall absorption rate increases to 84%. Therefore, the light absorption layer 300, composed of silicon oxide and silicon nitride layers, can indeed optimize far-infrared absorption efficiency.

[0071] Figure 4 This is a cross-sectional schematic diagram of a reference element of a far-infrared sensor according to a third embodiment of the present invention.

[0072] Please refer to Figure 4 In the third embodiment, the reference element is generally located next to or near the far-infrared sensing element to provide a reference value to remove noise from the sensing signal; for example, the reference element in the third embodiment is located near the far-infrared sensing element in the second embodiment and has the same characteristics as... Figure 3 The reference element has the same film layers and structure as the far-infrared sensing element, but without any release holes, thus retaining a sacrificial layer. Specifically, the reference element includes a light-absorbing reference layer 400, a sensing reference layer 402, an indium tin oxide (ITO) reference layer 404, an amorphous silicon sacrificial layer 406, and several reference conductive plugs 408 formed on the substrate 100. The light-absorbing reference layer 400 includes a first silicon nitride layer 410, a first silicon oxide layer 412, a second silicon nitride layer 414, and a second silicon oxide layer 416. However, the invention is not limited thereto. Because the reference element itself is used to provide reference values, it is sufficient that all the film layers and components (and their dimensions) in the reference element are the same as those in the far-infrared sensing element. In other words, if the light-absorbing layer of the far-infrared sensing element is only a silicon nitride layer, then the light-absorbing reference layer 400 is also a silicon nitride layer; and so on.

[0073] Please continue to refer to Figure 4 The light-absorbing reference layer 400 has several contact window openings 400a. A sensing reference layer 402 is formed in the light-absorbing reference layer 400, and an extension 402a of the sensing reference layer 402 extends to the contact window openings 400a. An indium tin oxide (ITO) reference layer 404 is formed between the light-absorbing reference layer 400 and the substrate 100. The ITO reference layer 404 has a first portion 418 and several second portions 420. The first portion 418 is located below the sensing reference layer 402 as a reflective layer, and the second portions 420 are connected to the extensions 402a. An amorphous silicon sacrificial layer 406, having no release holes, remains between the ITO reference layer 404 and the substrate 100. A reference conductive plug 408 is formed within the amorphous silicon sacrificial layer 406, connecting the second portions 420 to the interconnects (not shown) in the substrate 100.

[0074] Because amorphous silicon itself has a high etch selectivity with its surrounding films and components, as shown in Table 1 below, it can be used as a material for the sacrificial layer.

[0075] Table 1

[0076]

[0077] Compared with the conventional use of a photoresist-like material, such as polyimide, as a sacrificial layer, the present embodiment uses an amorphous silicon sacrificial layer 406, which not only forms a uniform-thickness sacrificial layer (e.g., a-Si:H) by PECVD, but also avoids the machine contamination problem of the subsequent deposition process (e.g., ITO layer, light-absorbing layer, sensing layer, etc.) due to the photoresist-like material. Moreover, since the amorphous silicon sacrificial layer 406 can be left in the peripheral (circuit) area, the far-infrared sensing element and the peripheral area are at the same height, which is conducive to the subsequent deposition, packaging, and other manufacturing processes.

[0078] In summary, the far-infrared sensing element of the present embodiment uses an ITO layer as a reflective layer and part of the support arm, so that better thermal insulation can be achieved through the ITO layer, which has a low thermal conductivity and high electrical conductivity, and the manufacturing process and photomask required for the conventional reflective layer (e.g., metal layer) can be saved, thereby significantly reducing the manufacturing cost. Moreover, the distance between the ITO reflective layer and the sensing layer is controlled by the light-absorbing layer, so the light-absorbing layer formed by deposition is more easily controlled in thickness than a polymer such as polyimide, thereby achieving the effect of constructive interference. In addition, the present embodiment can use an amorphous silicon sacrificial layer, so that the problem of particle contamination of the subsequent deposition machine can be avoided, and the amorphous silicon sacrificial layer in the peripheral area does not need to be removed, thereby having a smoother surface, which is conducive to the subsequent deposition and packaging manufacturing processes.

[0079] Although the present application is disclosed in connection with the above embodiments, it is not intended to limit the present application, and anyone with ordinary knowledge in the art can make some changes and modifications without departing from the spirit and scope of the present application, so the scope of protection of the present application should be defined by the appended claims.

Claims

1. A far infrared sensing element, comprising: a substrate; a light absorbing layer disposed on the substrate, wherein the light absorbing layer has a plurality of contact window openings; a sensing layer disposed in the light absorbing layer, and the sensing layer has an extension extending to the plurality of contact window openings; an indium tin oxide (ITO) layer disposed between the light absorbing layer and the substrate, wherein the ITO layer has a first portion and a plurality of second portions in the same layer, the first portion is located below the sensing layer as a reflecting layer, and the plurality of second portions are connected to the extension of the sensing layer as a plurality of arms with the light absorbing layer thereon; a plurality of conductive plugs respectively connecting the plurality of arms and an interconnect in the substrate, and forming a thermal isolation space between the reflecting layer and the substrate.

2. The far infrared sensing element according to claim 1, wherein the thickness of the ITO layer is in the range of 10 to 1000 A. The above.

3. The far infrared sensing element of claim 1, wherein a distance d between the ITO layer and the sensing layer satisfies the following formula (1): d = λ / 4n1 Formula (1) wherein n1 is a refractive index of the light absorbing layer, and λ is an absorption light wavelength. a silicon oxide layer, a silicon nitride layer, or a combination of a silicon oxide layer and a silicon nitride layer.

5. The far infrared sensing element of claim 1, wherein the light absorbing layer comprises:

4. The far infrared sensing element of claim 1, wherein the light absorbing layer comprises: a first silicon nitride layer located on the sensing layer; and a first silicon oxide layer located on the first silicon nitride layer.

8. The far infrared sensing element of claim 1, wherein the light absorbing layer comprises: a second silicon nitride layer located below the sensing layer; and a second silicon oxide layer located between the second silicon nitride layer and the reflecting layer.

6. The far infrared sensing element of claim 5, wherein the first silicon nitride layer has a thickness of between 10 A and 100 A. between 10 A and 100 A.

7. The far infrared ray sensing element according to claim 5, wherein a thickness of the first silicon oxide layer is 1 to 10 nm. The following.

9. The far infrared sensing element of claim 8, wherein a thickness t of the second silicon oxide layer satisfies the following formula (2): t = λ / 4n2 Formula (2) wherein n2 is a refractive index of the second silicon oxide layer, and λ is an absorption light wavelength.

13. The far infrared sensing element of claim 1, wherein the thermal isolation space is filled with nitrogen or has air, or the thermal isolation space is in a vacuum state.

14. A far infrared sensor, comprising: the far infrared sensing element of any one of claims 1-13; and a reference element, comprising: a light absorbing reference layer formed on the substrate, wherein the light absorbing reference layer has a plurality of contact window openings; a sensing reference layer formed in the light absorbing reference layer, and the sensing reference layer has an extension extending to the plurality of contact window openings; 10. The far-infrared sensing element of claim 8, wherein the thickness of the second silicon nitride layer is... between.

11. The far-infrared sensing element as claimed in claim 1, wherein the thickness of the sensing layer is... between.

12. The far infrared sensing element as claimed in claim 1, wherein a material of the sensing layer comprises amorphous silicon or vanadium oxide (VO x ). an indium tin oxide (ITO) reference layer formed between the light absorbing reference layer and the substrate, wherein the ITO reference layer has a first portion and a plurality of second portions, the first portion is located below the sensing reference layer as a reflecting layer, and the plurality of second portions are connected to the extension of the sensing reference layer; an amorphous silicon sacrificial layer disposed between the ITO reference layer and the substrate; and a plurality of reference conductive plugs formed in the amorphous silicon sacrificial layer, respectively connecting the plurality of second portions and the interconnect in the substrate. ​ ​ ​ ​ ​ ​ ​

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