A method of manufacturing a detector

Abstract

The application provides a preparation method of a detector, which can improve the uniformity of a micro-bridge unit structure. The method comprises the following steps: providing a silicon substrate, wherein a readout circuit is formed on the silicon substrate; forming a metal reflection layer and a dielectric layer on the surface of the silicon substrate; sequentially depositing a first sacrificial layer, a second sacrificial layer, a first release protection layer, a sensitive material detection layer, a metal electrode layer and a patterned metal electrode layer on the surface of the metal reflection layer and the dielectric layer; depositing a second release protection layer to cover the sensitive material detection layer and the metal electrode layer; etching to form a contact hole after the second release protection layer is patterned; depositing metal in the contact hole to form a support structure; depositing a third release protection layer and patterning to form a micro-bridge unit structure; depositing a third sacrificial layer on the surface of the micro-bridge unit structure; performing photoetching to form a beam structure; and removing the first sacrificial layer, the second sacrificial layer and the third sacrificial layer by a process release to form a suspended micro-bridge unit structure.

Description

Technical Field

[0001] This invention relates to the field of semiconductor integrated circuit manufacturing, and more particularly to a method for fabricating a detector. Background Technology

[0002] Micro-electro-mechanical systems (MEMS) technology integrates mechanical components, drive components, electronic control systems, and digital processing systems into a single miniature system. These MEMS systems can not only acquire, process, and transmit information or commands, but also act autonomously or according to external instructions. Using a manufacturing process combining microelectronics and microfabrication techniques, they produce a variety of high-performance, low-cost, miniaturized sensors, actuators, drivers, and microsystems. With its numerous advantages such as miniaturization, intelligence, actuation capability, integrability, good process compatibility, and low cost, it has begun to be widely used in detectors, sensors, and many other fields.

[0003] The MEMS microbridge unit structure of the detector typically requires a release process to remove the sacrificial layer beneath the microbridge unit structure, forming a suspended microbridge unit structure. For microbridge unit structures as arrays of units, during conventional release processes, the released gas passes through the pattern spacing between repeating units and reacts chemically with the sacrificial layer downwards to remove it. However, during this reaction, the upper surface of the microbridge unit structure is in direct contact with the released gas, thus causing some damage to the microbridge unit structure. Because the release process involves a chemical reaction, the uniformity is relatively poor, especially when the release selectivity is low. This results in a longer reaction time for the released protective layer on the surface of the microbridge unit structure, leading to uneven etching thickness and causing inhomogeneity in the microbridge unit structure after release.

[0004] Therefore, it is necessary to develop a novel method for fabricating detectors to address the aforementioned problems in existing technologies. Summary of the Invention

[0005] This invention provides a method for fabricating a detector to improve the uniformity of the microbridge unit structure of the detector.

[0006] In a first aspect, the present invention provides a method for fabricating a detector, the method comprising: providing a silicon substrate on which a readout circuit is formed; forming a metal reflective layer and a dielectric layer on the surface of the silicon substrate; sequentially depositing a first sacrificial layer, a second sacrificial layer, a first release protection layer, a sensitive material detection layer, a metal electrode layer, and a patterned metal electrode layer on the surfaces of the metal reflective layer and the dielectric layer; depositing a second release protection layer covering the sensitive material detection layer and the metal electrode layer; patterning the second release protection layer and then etching to form contact holes exposing a portion of the metal reflective layer, and depositing metal within the contact holes to form a support structure; depositing a third release protection layer and patterning to form a microbridge unit structure, the microbridge unit structure including the first release protection layer, the sensitive material detection layer, the metal electrode layer, the second release protection layer, and the third release protection layer; depositing a third sacrificial layer on the surface of the microbridge unit structure; performing photolithographic etching to form a beam structure; and removing the first sacrificial layer, the second sacrificial layer, and the third sacrificial layer through process release to form a suspended microbridge unit structure.

[0007] In one possible implementation, the specific steps for forming the beam structure through photolithographic etching include:

[0008] Photolithography is performed to form trenches that penetrate the first sacrificial layer, the second sacrificial layer, and the third sacrificial layer, forming the beam structure between adjacent trenches. The size of the trenches is smaller than the width of the beam structure. The third sacrificial layer is disposed on the upper surface of the beam structure, and the second sacrificial layer is disposed on the lower surface of the beam structure, thus protecting the upper and lower surfaces of the beam structure.

[0009] In one possible implementation, the second sacrificial layer and the first sacrificial layer are made of the same material. The release selectivity ratio between the second sacrificial layer and the third release protection layer is greater than that between the first sacrificial layer and the third release protection layer. Although the materials are the same, the thicknesses of the third sacrificial layer, the second sacrificial layer, and the first sacrificial layer can be determined according to the release rate, so that while releasing the sacrificial layer inside the suspended structure, the sacrificial layer at the top of the microbridge unit structure is also released without damaging the third release protection layer at the top, thereby indirectly improving the selectivity ratio.

[0010] In another possible implementation, the first sacrificial layer is made of amorphous silicon; the second and third sacrificial layers are both made of amorphous carbon. This embodiment uses new materials for the second and third sacrificial layers, maintaining a relatively thin thickness. The thickness of the first sacrificial layer is much greater than the sum of the thicknesses of the second and third sacrificial layers. During the release process, after releasing the first sacrificial layer, a new release gas can be used to remove the second and third sacrificial layers, thereby protecting the upper and lower surfaces of the microbridge unit structure and obtaining a high-performance structure.

[0011] In one possible implementation, after depositing a third sacrificial layer on the surface of the microbridge unit structure, the method further includes: patterning the third sacrificial layer, removing a portion of the third sacrificial layer from the surface of the microbridge unit structure, such that the thickness of the third sacrificial layer is lower than the thickness of the beam structure.

[0012] In other possible implementations, the thickness of the third sacrificial layer is greater than the thickness of the second sacrificial layer. For example, the ratio is greater than 2:1, because the reaction rate of the reactive gas is slower at the bottom of the microbridge unit structure.

[0013] In one possible implementation, the dielectric layer may be planarized such that the height of the metal reflective layer is the same as the height of the dielectric layer.

[0014] In one possible implementation, the metal is tungsten or aluminum.

[0015] The beneficial effects of the detector fabrication method provided in this invention are as follows: Based on the original process, this invention adds a second sacrificial layer to the lower surface of the microbridge unit structure and a third sacrificial layer to the upper surface of the microbridge unit structure. When the third and second sacrificial layers are made of the same material as the first sacrificial layer, the thickness of each sacrificial layer can be determined according to the release rate. This allows the top sacrificial layer to be released simultaneously with the release of the sacrificial layer inside the suspended structure, without damaging the top release protection layer, thereby indirectly improving the selectivity. When the third and second sacrificial layers are made of the same material, but the third sacrificial layer is made of a different material than the first sacrificial layer, the thickness of the second and third sacrificial layers can be made thinner. After releasing the first sacrificial layer, the second and third sacrificial layers are removed with a new release gas, thereby protecting the upper and lower surfaces of the microbridge and making the MEMS microbridge unit structure of the detector uniform, resulting in a high-performance microbridge unit structure. Attached Figure Description

[0016] Figure 1 A three-dimensional structural diagram of a detector provided in an embodiment of the present invention;

[0017] Figure 2 Provided for embodiments of the present invention Figure 1 A schematic diagram of the cross-sectional structure of the detector in the image;

[0018] Figure 3 This is a schematic flowchart of a detector manufacturing method provided in an embodiment of the present invention;

[0019] Figures 4A to 4H The diagram shown is a flowchart illustrating the fabrication method of the microbridge unit structure in an embodiment of the present invention.

[0020] Wherein, 10-substrate, 11-readout circuit, 12-dielectric layer, 13-metal reflective layer, 14-support structure, 15-microbridge unit structure, 151-first release protection layer, 152-sensitive material detection layer, 153-metal electrode layer.

[0021] 154 - Second release protection layer, 155 - Third release protection layer, 161 - First sacrificial layer, 162 - Second sacrificial layer, 163 - Third sacrificial layer. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be described below with reference to the accompanying drawings. In the description of the embodiments of the present invention, the terminology used in the following embodiments is for the purpose of describing specific embodiments only and is not intended to be a limitation of the present invention. As used in the specification and appended claims of the present invention, the singular expressions “a,” “the,” “the,” “the,” and “this” are intended to also include expressions such as “one or more,” unless the context clearly indicates otherwise.

[0023] References to "one embodiment" or "some embodiments" as used in this specification mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in one or more embodiments of the invention. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including, but not limited to," unless otherwise specifically emphasized. The term "connection" includes both direct and indirect connections, unless otherwise stated. "First" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0024] In embodiments of the present invention, the terms "exemplarily" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplarily" or "for example" in embodiments of the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the terms "exemplarily" or "for example" is intended to present the relevant concepts in a specific manner.

[0025] Figure 1 This is a three-dimensional structural diagram of a detector provided in an embodiment of the present invention. Figure 2 This is a schematic cross-sectional view of a detector provided in an embodiment of the present invention. See also... Figure 1 and Figure 2 As shown, an embodiment of the present invention provides a detector, which sequentially includes a silicon substrate 10; a readout circuit 11, a dielectric layer 12, a metal reflective layer 13, a support structure 14 covering the silicon substrate 10; a microbridge unit structure 15 and two beam structures a located on the support structure 14; the microbridge unit structure 15 is connected to the support structure 14 through the beam structures a.

[0026] The microbridge unit structure 15 includes: a first release protection layer 151, a sensitive material detection layer 152, a metal electrode layer 153, a second release protection layer 154, and a third release protection layer 155. In other possible implementations, the microbridge unit structure 15 may further include a dielectric insulating layer, an absorption layer, and an antireflective material layer. Figure 2 (Not shown in the image).

[0027] It is worth noting that, Figure 1 The beam structure a in the embodiment of the present invention is an illustrative shape. The beam structure a may also include other serpentine or other irregular shapes. The embodiments of this application do not limit this.

[0028] The second release protection layer 154 structurally covers the sensitive material detection layer 152 and the metal electrode layer 153 to protect them. For example, the metal reflective layer 13 may be made of aluminum. The sensitive material detection layer 152 may be made of amorphous silicon or vanadium oxide. In one embodiment of the invention, the metal electrode layer 153 may be one or a combination of a titanium electrode, a tantalum electrode, stacked titanium nitride and titanium electrodes, and stacked tantalum and tantalum nitride electrodes.

[0029] In one embodiment of the present invention, the first release protection layer 151, the second release protection layer 154 and the third release protection layer 155 may be thin films based on silicon, oxygen, carbon and nitrogen, such as silicon dioxide (SiO2), silicon oxynitride (SiON), silicon nitride (SiN) and silicon carbide (SiC), or thin films with non-stoichiometric ratios, such as oxygen-rich or silicon-rich silicon dioxide films, or thin films doped with impurity elements such as boron, phosphorus, carbon or fluorine, such as fluorosilicone glass (FSG), borosilicate glass (BPSG) or phosphosilicate glass (PSG), or composite films composed of the above materials.

[0030] In one possible implementation, the height of the dielectric layer 12 located between the metal reflection patterns in the metal reflection layer 13 is the same as the height of the metal reflection layer 13. Specifically, the dielectric layer 12 may be made of silicon dioxide, silicon oxynitride, or silicon dioxide or silicon oxynitride doped with impurity elements such as fluorine.

[0031] Figure 3 This is a schematic diagram of a method for manufacturing a detector provided by the present invention.

[0032] S301, Fabricate a silicon substrate 10, on which a readout circuit 11 is formed.

[0033] In this embodiment, the detector's readout circuit 11 is fabricated using standard Complementary Metal Oxide Semiconductor (CMOS) technology. See [link to documentation]. Figure 4A .

[0034] S302, a metal reflective layer 13 and a dielectric layer 12 are formed on the surface of the silicon substrate 10.

[0035] Specifically, in one possible embodiment, a metal reflective layer 13 can be first formed and patterned on the surface of the silicon substrate 10, and then a dielectric layer 12 can be formed on the metal reflective layer 13. In this embodiment, the pattern of the metal reflective layer 13 can be achieved using processes such as photolithography and etching. The metal reflective layer 13 serves as a spectral reflective layer, improving the detector's absorption and thus its responsivity. In this embodiment, the metal reflective layer 13 is formed using physical vapor deposition (PVD) technology, and the metal material can be a thin film of metal such as aluminum, tantalum, or titanium. The detector's metal reflective layer 13 is electrically connected to the readout circuit 11 through metal vias, see [link to relevant documentation]. Figure 4A As shown.

[0036] In one possible embodiment, the dielectric layer 12 can be further planarized so that the height of the metal reflective layer 13 is the same as the height of the dielectric layer 12. The dielectric material used in the dielectric layer 13 may be one or a combination of silicon dioxide, silicon oxynitride, silicon nitride and silicon carbide, and / or one or a combination of silicon dioxide, silicon oxynitride, silicon nitride and silicon carbide doped with impurity elements such as boron, phosphorus, carbon or fluorine.

[0037] S303, a first sacrificial layer 161, a second sacrificial layer 162, a first release protection layer 151, a sensitive material detection layer 152, a metal electrode layer 153, and a patterned metal electrode layer 153 are sequentially deposited on the surfaces of the metal reflective layer 13 and the dielectric layer 12.

[0038] For example, such as Figure 4B As shown, a first sacrificial layer 161 is deposited on the dielectric layer 12. Then, as... Figure 4C As shown, a second sacrificial layer 162 is deposited on the first sacrificial layer 161, and a first release protection layer 151 and a sensitive material detection layer 152 are deposited on the second sacrificial layer 162. Then, a metal electrode layer 153 is deposited on the surface of the sensitive material detection layer 152. The metal electrode layer 153 is used to achieve electrical contact. Then, the metal electrode layer 153 is patterned.

[0039] S304, a second release protection layer 154 is deposited to cover the sensitive material detection layer 152 and the metal electrode layer 153.

[0040] For example, such as Figure 4D As shown, a second release protection layer 154 is deposited on the metal electrode layer 153. The second release protection layer 154 covers the sensitive material detection layer 152 and the metal electrode layer 153, thereby effectively protecting the sensitive material detection layer 152 and the metal electrode layer 153 during the release process; simultaneously, it isolates external contamination and damage during manufacturing and use, improving the reliability of the sensitive material detection layer 152; furthermore, it can prevent short circuits in the metal electrode layer 153.

[0041] S305, after patterning the second release protection layer 154, etching is performed to form contact holes that expose a portion of the metal reflective layer, and metal is deposited in the contact holes to form a support structure 14.

[0042] The metal may be tungsten or aluminum. For example, such as... Figure 4EAs shown, in this embodiment, the pattern to be filled in the support structure 14 can be achieved using photolithography and etching, and then the standard copper electroplating and chemical mechanical polishing processes in the damascus copper interconnect process can be used to complete the filling and patterning of the support structure 14. The support structure 14 serves both as the support structure for the microbridge unit structure 15 after the release of the first sacrificial layer 161 and the second sacrificial layer 162, and as the electrical connection structure between the microbridge unit structure 15 and the metal reflective layer 13.

[0043] S306, deposit the third release protective layer 155, and pattern it to form a microbridge unit structure 15.

[0044] For example, such as Figure 4F As shown, a third release protection layer 155 is deposited on the surface of the above structure. Similarly, the third release protection layer 155 covers the second release protection layer 154 and the upper surface of the support structure 14, effectively protecting the support structure 14; at the same time, it isolates external contamination and damage during manufacturing and use. It can be seen that the microbridge unit structure 15 includes the first release protection layer 151, the sensitive material detection layer 152, the metal electrode layer 153, the second release protection layer 154, and the third release protection layer 155.

[0045] S307, a third sacrificial layer 163 is deposited on the surface of the microbridge unit structure 15.

[0046] For example, such as Figure 4G As shown, a third sacrificial layer 163 is deposited on the surface of the microbridge unit structure 15. It can be seen that the third sacrificial layer 163 is located on the upper surface of the microbridge unit structure, and the second sacrificial layer 162 is located on the lower surface of the microbridge unit structure, with the second sacrificial layer 162 and the third sacrificial layer 163 covering the microbridge unit structure. Optionally, the thickness of the third sacrificial layer is greater than the thickness of the second sacrificial layer. For example, the ratio is greater than 2:1, because the reaction rate of the reactant gas is slower at the bottom of the microbridge unit structure.

[0047] S308, photolithography etching is performed to form beam structure a.

[0048] In one possible embodiment, the specific steps of photolithographic etching to form a beam structure include: performing photolithographic etching to form at least two trenches penetrating the first sacrificial layer 161, the second sacrificial layer 162 and the third sacrificial layer 163, and forming a beam structure a between two adjacent trenches.

[0049] For example, the formed trenches are as follows Figure 4H As shown in the figure, four grooves are formed by etching, and beam structures a of microbridge unit structure 15 are formed between two adjacent grooves, resulting in a total of two beam structures a. The microbridge unit structure 15 is connected to the support structure 14 through the beam structures a.

[0050] In one possible implementation, the size L of the groove is smaller than the width D of the beam structure. The third sacrificial layer 163, the second sacrificial layer 162, and the first sacrificial layer 161 cover the upper and lower surfaces of the beam structure a. Since the third sacrificial layer is located on the upper surface of the beam structure and the second sacrificial layer is located on the lower surface of the beam structure, the sacrificial layers protect the upper and lower surfaces of the beam structure a and have a certain thickness, such as the thickness of the third sacrificial layer 163 > 0.05 μm. The beam structure is thin, and the sacrificial layers on the upper and lower surfaces of the structural area are released together. Because the groove is provided on the side of the beam structure, the sacrificial layer is released faster, thus protecting the upper and lower surfaces of the beam structure.

[0051] In one possible implementation, after depositing a third sacrificial layer 163 on the surface of the microbridge unit structure, the method further includes: patterning and removing a portion of the sacrificial layer on the surface of the microbridge unit structure, wherein the thickness h of the third sacrificial layer 163 is less than the thickness H of the beam structure a.

[0052] S309, the process release removes the first sacrificial layer 161, the second sacrificial layer 162 and the third sacrificial layer 163 to form the suspended microbridge unit structure 15.

[0053] Exemplarily, the suspended microbridge unit structure 15 after release is as follows: Figure 2 As shown.

[0054] In this embodiment, in one possible implementation, the third sacrificial layer 163, the second sacrificial layer 162, and the first sacrificial layer 161 are made of the same material, which can all be amorphous silicon or amorphous carbon, formed by enhanced plasma chemical vapor deposition (PECVD). The release selectivity ratio between the second sacrificial layer 162 or the third sacrificial layer 163 and the third release protection layer 155 is greater than the release selectivity ratio between the first sacrificial layer 161 and the third release protection layer 155. Although the materials are the same, the thickness of the third sacrificial layer 163, the second sacrificial layer 162, and the first sacrificial layer 161 can be determined according to the release rate, so that while releasing the sacrificial layer inside the suspended structure, the third sacrificial layer 163 at the top of the microbridge unit structure will also be released without damaging the top release protection layer, thereby indirectly improving the selectivity ratio.

[0055] In another possible implementation, the first sacrificial layer is made of amorphous silicon; the second and third sacrificial layers are both made of amorphous carbon. This embodiment uses new materials for the second sacrificial layer 162 and the third sacrificial layer 163, maintaining a relatively thin thickness. The thickness of the first sacrificial layer 161 is much greater than the sum of the thicknesses of the second and third sacrificial layers 162 and 163. In the release process, after releasing the first sacrificial layer 161, the second and third sacrificial layers 162 and 163 can be removed using a new release gas, thereby protecting the upper and lower surfaces of the microbridge unit structure 15 and obtaining a high-performance structure.

[0056] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0057] In summary, the above description is merely a preferred embodiment of the technical solution of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for fabricating a detector, characterized in that, The method includes: A silicon substrate is provided on which a readout circuit is formed; A metal reflective layer and a dielectric layer are formed on the surface of the silicon substrate; A first sacrificial layer, a second sacrificial layer, a first release protection layer, a sensitive material detection layer, a metal electrode layer, and a patterned metal electrode layer are sequentially deposited on the surfaces of the metal reflective layer and the dielectric layer. A second release protection layer is deposited to cover the sensitive material detection layer and the metal electrode layer; After the second release protective layer is patterned, an etching process is performed to form contact holes that expose a portion of the metal reflective layer, and metal is deposited within the contact holes to form a support structure. A third release protection layer is deposited and patterned to form a microbridge unit structure, the microbridge unit structure including the first release protection layer, the sensitive material detection layer, the metal electrode layer, the second release protection layer and the third release protection layer; A third sacrificial layer is deposited on the surface of the microbridge unit structure; A beam structure is formed by photolithography etching, and the microbridge unit structure is connected to the support structure through the beam structure; The process releases the first sacrificial layer, the second sacrificial layer, and the third sacrificial layer to form the suspended microbridge unit structure.

2. The method according to claim 1, characterized in that, The specific steps for forming a beam structure through photolithography and etching include: Photolithography is performed to form trenches that penetrate the first sacrificial layer, the second sacrificial layer, and the third sacrificial layer, and the beam structure is formed between two adjacent trenches; The size of the groove is smaller than the width of the beam structure, the third sacrificial layer is disposed on the upper surface of the beam structure, and the second sacrificial layer is disposed on the lower surface of the beam structure.

3. The method according to claim 1, characterized in that, The third sacrificial layer, the second sacrificial layer, and the first sacrificial layer are made of the same material.

4. The method according to claim 3, characterized in that, The release selectivity ratio between the second sacrificial layer and the third release protection layer is greater than the release selectivity ratio between the first sacrificial layer and the third release protection layer.

5. The method according to claim 1, characterized in that, The first sacrificial layer is made of amorphous silicon; the second and third sacrificial layers are both made of amorphous carbon.

6. The method according to claim 1, characterized in that, After depositing a third sacrificial layer on the surface of the microbridge unit structure, the method further includes: The third sacrificial layer is graphically represented, and a portion of the third sacrificial layer on the surface of the microbridge unit structure is removed, so that the thickness of the third sacrificial layer is lower than the thickness of the beam structure.

7. The method according to claim 3, characterized in that, The thickness of the third sacrificial layer is greater than the thickness of the second sacrificial layer.

8. The method according to claim 3, characterized in that, The thickness of the first sacrificial layer is much greater than the sum of the thicknesses of the second and third sacrificial layers.

9. The method according to claim 1, characterized in that, Also includes: The dielectric layer is planarized so that the height of the metal reflective layer is the same as the height of the dielectric layer.

10. The method according to claim 1, characterized in that, The metal is tungsten or aluminum.

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