MEMS thin film manufacturing method and MEMS thin film sensor

Abstract

The invention discloses an MEMS thin film manufacturing method and an MEMS thin film sensor, and the manufacturing method comprises the steps: carrying out the local etching of a thin film material on the surface of a wafer through employing a reactive ion etching technology, and forming a through hole / through groove; filling a filling material into the through hole / through groove formed in the previous step by using a coating process or a deposition process; performing back cavity etching on one side, deviating from the thin film material, of the wafer by using an inductively coupled plasma etching process; and removing the filled filling material to obtain the thin film structure with the thin film material reserved. According to the MEMS thin film manufacturing method, the filling material is used for covering the through hole / through groove, it is ensured that the thin film cannot be vertically through in the process of back cavity etching on the wafer, the manufacturing efficiency of the non-closed thin film structure is greatly improved, and an MEMS sensor with the non-closed thin film structure can be efficiently and reliably machined.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, and in particular to a method for manufacturing an MEMS thin film and an MEMS thin film sensor. Background Art

[0002] In some MEMS (Micro-Electro-Mechanical System) sensors (such as thermopile sensors), a cavity structure needs to be arranged inside the sensor, and there is a suspended film above the cavity structure to achieve specific functions. In MEMS sensors, the thin film is an important part of its functional composition and determines whether the functions of MEMS devices can meet the design requirements. In terms of the structure of the thin film, it generally includes a closed film structure, a closed film with an opening structure, and a cantilever beam structure. For the release process of the closed film with an opening structure and the cantilever beam structure, there are several ways to carry out the release process; for example, using the TMAH anisotropic etching process; or pre-filling a sacrificial layer under the thin film, and then corroding the sacrificial material after all processes are completed to form a cavity; or using a temporary bonding process. After etching the opening or cantilever structure, temporarily bond the wafers, and then use the ICP etching process to perform bulk silicon etching from the back. After the etching is completed, then perform debonding (such as Patent CN114852952B).

[0003] In the existing ICP (Inductively Couple Plasma) etching process, using conventional steps, only a closed thin film structure can be fabricated; while in Patent CN114852952B, the method of setting a patch ring may cause uneven heating of the wafer to be etched during the etching process because the wafer to be etched is not in contact with the stage of the etching machine, resulting in poor uniformity of the etching cavity; if the method of setting a patch ring in the above patent is not adopted and the dummy wafer is directly bonded to the wafer to be etched with glue, after the etching is completed, it is necessary to debond the dummy wafer and the wafer to be etched, which may cause difficulties in removing the glue, inability to separate the dummy wafer and the wafer to be etched, glue residue, and thin film rupture. Therefore, the methods in the prior art for manufacturing MEMS thin films have the problem of being unable to efficiently and reliably process non-closed thin film structures. Summary of the Invention

[0004] Embodiments of the present invention provide a method for manufacturing an MEMS thin film and an MEMS thin film sensor, aiming to solve the problem in the prior art methods that non-closed thin film structures cannot be efficiently and reliably processed.

[0005] In a first aspect, an embodiment of the present application provides a method for fabricating a MEMS thin film. Among them, the method for fabricating a MEMS thin film is used to etch a wafer to fabricate a thin film. The wafer includes a thin film material and a substrate stacked in sequence. The method includes: Locally etch the thin film material on the surface of the wafer using a reactive ion etching process to form through holes / through grooves; Use a coating process or a deposition process to fill the through holes / through grooves formed in the above step with a filling material; Use an inductively coupled plasma etching process to perform back cavity etching on the side of the wafer facing away from the thin film material; Remove the filled filling material to obtain a thin film structure with the thin film material retained.

[0006] For the method for fabricating a MEMS thin film, among them, before using a coating process or a deposition process to fill the through holes / through grooves formed in the above step with a filling material, it further includes: Deposit a protective material in the formed through holes / through grooves; Perform reactive ion etching on the deposited protective material to form small holes / small grooves with dimensions smaller than the through holes / through grooves, so that a protective material layer is retained on the inner wall of the through holes / through grooves.

[0007] For the method for fabricating a MEMS thin film, among them, depositing a protective material in the formed through holes / through grooves includes: Use plasma enhanced chemical vapor deposition process to deposit a protective material in the formed through holes / through grooves; Use chemical mechanical polishing process to grind and polish the surface layer of the deposited protective material.

[0008] For the method for fabricating a MEMS thin film, among them, the protective material is one or more of silicon dioxide, silicon nitride, aluminum oxide, silicon carbide, polysilicon, polyimide.

[0009] For the method for fabricating a MEMS thin film, among them, the thickness of the protective material layer retained on the inner wall of the through holes / through grooves is 1 / 12 - 1 / 4 of the width of the through holes / through grooves.

[0010] For the method for fabricating a MEMS thin film, among them, removing the filled filling material includes: Use a chemical etching process to etch the filled filling material to completely remove the filling material.

[0011] For the method for fabricating a MEMS thin film, among them, removing the filled filling material includes: Use an oxygen plasma etching process to etch the filled filling material to completely remove the filling material.

[0012] The described method for fabricating a MEMS thin film, wherein the inductively coupled plasma etching process is used to perform back cavity etching on the side of the wafer facing away from the thin film material, including: On the side of the wafer facing away from the thin film material, silicon oxide, silicon nitride, or photoresist is used as an etching mask; The inductively coupled plasma etching process is used to etch the side of the wafer with the mask added.

[0013] The described method for fabricating a MEMS thin film, wherein the filling material is one or more of porous silicon, photoresist, silicon dioxide, polyimide, and polymethyl methacrylate.

[0014] In a second aspect, an embodiment of the present application further provides a MEMS thin film sensor, which is fabricated by the method for fabricating a MEMS thin film described in the first aspect above. Among them, the MEMS thin film sensor includes a thin film layer and a substrate stacked in sequence; at least one through hole / through groove is provided in the thin film layer.

[0015] An embodiment of the present invention provides a method for fabricating a MEMS thin film and a MEMS thin film sensor. The fabrication method includes locally etching a thin film material on the surface of a wafer using a reactive ion etching process to form through holes / through grooves; using a coating process or a deposition process to fill the through holes / through grooves formed in the above steps with a filling material; using an inductively coupled plasma etching process to perform back cavity etching on the side of the wafer facing away from the thin film material; and removing the filled filling material to obtain a thin film structure retaining the thin film material. In the above method for fabricating a MEMS thin film, the through holes / through grooves are covered with a filling material to ensure that the thin film does not penetrate up and down during the back cavity etching of the wafer, greatly improving the fabrication efficiency of the non-closed thin film structure, and enabling the efficient and reliable processing of a MEMS sensor with a non-closed thin film structure. Description of the Drawings

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for description in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 It is a flowchart of the method for fabricating a MEMS thin film provided by an embodiment of the present invention; Figure 2 It is another flowchart of the method for fabricating a MEMS thin film provided by an embodiment of the present invention; Figure 3Schematic diagram of the processing procedure of the MEMS thin film manufacturing method provided by the embodiment of the present invention; Figure 4 Another schematic diagram of the processing procedure of the MEMS thin film manufacturing method provided by the embodiment of the present invention; Figure 5 Cross-sectional structure diagram of the MEMS thin film sensor provided by the embodiment of the present invention; Reference numerals: 1, substrate; 2, thin film layer; 3, protective material; 4, filling material; 5, back cavity; 21, through groove. Detailed implementation manners

[0018] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0019] It should be understood that when used in this specification and the appended claims, the terms "comprises" and "comprising" indicate the presence of the described features, wholes, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or their combinations.

[0020] It should also be understood that the terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" are intended to include the plural forms. It should be further understood that the term " / and" used in the specification of the present invention and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0021] The specific embodiment of the present application discloses a method for manufacturing a MEMS thin film. Among them, the method for manufacturing a MEMS thin film is used to etch a wafer to manufacture a thin film. The wafer includes a thin film material and a substrate stacked in sequence. The initial structure of the wafer is as Figure 3 shown in (a) of Figure 4 or Figure 1 shown in (a) of

[0022] S1. Use a reactive ion etching process to locally etch the thin film material on the surface of the wafer to form a through hole / through groove.

[0023] First, local etching can be performed on the film collection on the wafer surface through a reactive ion etching (RIE) process, so as to form vias / troughs in the film material on the wafer surface. As Figure 3 in (b) and Figure 4 in (b) shown, a plurality of vias / troughs 21 are formed in the film material on the wafer surface through the RIE process.

[0024] S2. Use a coating process or a deposition process to fill the vias / troughs formed in the above step with a filling material.

[0025] Then use the filling material 4 to fill the vias / troughs formed in the above step. Specifically, a coating process or a deposition process can be used to fill the vias / troughs. Among them, the coating process can be spin coating or spraying; the deposition process can be PVD (Physical Vapor Deposition) or CVD (Chemical Vapor Deposition). The filling material 4 used above is one or more of porous silicon, photoresist, silicon dioxide, polyimide, and polymethyl methacrylate. Preferably, polyimide is used as the filling material. The specific implementation steps are as Figure 3 in (c) shown. At this time, the etching agent used to remove the filling material has no damage to the original wafer material, so there is no need to fill the protective material.

[0026] Please refer to Figure 2 , as shown in the figure, the MEMS thin film manufacturing method of the second embodiment of the present application further includes steps S11 and S12, wherein S11 and S12 are performed before S2. At this time, the etching agent used to remove the filling material may cause damage to the original wafer material. S11. Deposit a protective material in the formed vias / troughs; S12. Perform reactive ion etching (RIE) on the deposited protective material to form small holes / small troughs with sizes smaller than the vias / troughs, then a protective material layer is retained on the inner wall of the vias / troughs.

[0027] A protective material can be deposited in the formed vias / troughs. The device structure obtained after depositing the protective material is as Figure 4 in (c) shown. The specific operation method of depositing the protective material can be any one or a combination of PVD, CVD, spin coating, and spraying. Further perform reactive ion etching on the deposited protective material to obtain a small hole or a small trough. Then the size of the small hole / small trough is smaller than the size of the vias / troughs. The obtained device structure is as Figure 4 in (d) shown. In Figure 4Based on the device shown in (d) of the figure, the above-mentioned step S2 is further used to fill the filling material, and the obtained device structure is as Figure 4 shown in (e) of the figure.

[0028] In a specific embodiment, a protective material is deposited in the formed through hole / through groove, specifically including: using a plasma enhanced chemical vapor deposition process (PECVD) to deposit a protective material 3 in the formed through hole / through groove; using a chemical mechanical polishing process (CMP) to grind and polish the surface layer of the deposited protective material 3.

[0029] Among them, the protective material can be one or more of silicon dioxide, silicon nitride, aluminum oxide, silicon carbide, polysilicon, and polyimide. If polyimide is selected as the filling material, the protective material can be correspondingly selected as silicon nitride. Further, to ensure that the protective material can form a good protection effect, the thickness of the protective material layer retained on the inner wall of the through hole / through groove can be set to 1 / 12 - 1 / 4 of the width of the through hole / through groove. For example, if the thickness of the protective material layer is 1 / 12 of the width of the through hole / through groove, the remaining width between the two protective material layers is 5 / 6 of the width of the through hole / through groove; if the thickness of the protective material layer is 1 / 4 of the width of the through hole / through groove, the remaining width between the two protective material layers is 1 / 2 of the width of the through hole / through groove.

[0030] Further, the specific steps for removing the filled filling material include: using a chemical etching process to etch the filled filling material to completely remove the filling material. Since a protective material is deposited in the through hole / through groove here and a protective material layer is obtained, the problem of damage to the original wafer material caused by the etching agent does not need to be considered when removing the filling material. In a specific application process, the protective material can be filled only outside the through hole / through groove, and can also cover other positions of the wafer. If necessary, the protective material can also be deposited on the top surface of the wafer, or a protective material can be added between the substrate and the thin film material to avoid affecting the device performance or the reliability of the thin film when removing the filling material.

[0031] S3. Use an inductively coupled plasma etching process to perform back cavity etching on the side of the wafer facing away from the thin film material.

[0032] An inductively coupled plasma etching process (ICP) can be used to perform back cavity etching on the side of the wafer facing away from the thin film material, that is, to etch the back surface of the wafer to form a back cavity 5. The specific device structure obtained after etching is as Figure 3 shown in (d) of the figure and Figure 4 shown in (f) of the figure.

[0033] In a more specific embodiment, the steps of performing back cavity etching include: using silicon oxide, silicon nitride or photoresist as an etching mask on the side of the wafer facing away from the thin film material; using an inductively coupled plasma etching process to etch the side of the wafer with the mask added, and at this time the etched pattern / area corresponds to the etching mask.

[0034] S4. Remove the filled filling material to obtain a thin film structure with the thin film material retained.

[0035] Furthermore, the filling material in the through holes / through grooves can be removed, so as to obtain a thin film structure with the thin film material retained. At this time, the substrate below the thin film structure is etched to form a cavity, and the obtained device structure is as Figure 3 in (e) and Figure 4 shown in (g).

[0036] After completing the above steps, post-processing of the device can also be performed, such as annealing or heat treatment, etc. In addition, one or several of chemical dissolution, plasma etching, heat treatment, and electrochemical dissolution can also be used to remove the filling material.

[0037] More specifically, an oxygen plasma etching process can be used to etch the filled filling material to completely remove the filling material; in the case where the protective material is not deposited and the protective material layer is not obtained, a corrosion agent that will not damage the original wafer material needs to be used, and the oxygen plasma etching process can be used to remove the filling material, and this process method will not damage the original wafer material.

[0038] Compared with the prior art, the present invention can be compatible with any opening or grooving thin film process, without introducing jigs, and is completely based on semiconductor processes. When performing an ICP etching (or ICP-RIE etching) process, the wafer can be ensured to be heated evenly, and the etching uniformity can be improved.

[0039] An embodiment of the present invention also provides a MEMS thin film sensor, and the MEMS thin film sensor is fabricated by the MEMS thin film fabrication method as described in the above embodiment, as Figure 5 shown, the MEMS thin film sensor includes a thin film layer 2 and a substrate 1 stacked in sequence; at least one through hole / through groove 21 is provided on the thin film layer 2. Since through holes / through grooves 21 are formed on the thin film layer 2, the sensor is a MEMS sensor with a non-closed thin film structure.

[0040] An embodiment of the present invention provides a method for fabricating a MEMS thin film and a MEMS thin film sensor. The fabrication method includes locally etching a thin film material on the surface of a wafer using a reactive ion etching process to form through holes / through grooves; filling the through holes / through grooves formed in the above step with a filling material using a coating process or a deposition process; performing back cavity etching on the side of the wafer facing away from the thin film material using an inductively coupled plasma etching process; and removing the filled filling material to obtain a thin film structure with the thin film material retained. In the above MEMS thin film fabrication method, the through holes / through grooves are covered with a filling material to ensure that the thin film does not penetrate up and down during the back cavity etching of the wafer, greatly improving the fabrication efficiency of the non-closed thin film structure, and enabling the efficient and reliable processing of a MEMS sensor with a non-closed thin film structure.

[0041] As described above, the above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A method for fabricating a MEMS thin film, characterized in that, The MEMS thin film manufacturing method is used to etch a wafer to fabricate a thin film. The wafer includes a thin film material and a substrate stacked in sequence. The method includes: Locally etching the thin film material on the surface of the wafer using a reactive ion etching process to form vias / troughs; Filling the formed vias / troughs with a filling material using a coating process or a deposition process; Performing back cavity etching on the side of the wafer facing away from the thin film material using an inductively coupled plasma etching process; Removing the filled filling material to obtain a thin film structure with the thin film material retained; 2. The MEMS thin film manufacturing method according to claim 1, wherein Before filling the formed vias / troughs with a filling material using a coating process or a deposition process, it further includes: Depositing a protective material in the formed vias / troughs; Performing reactive ion etching on the deposited protective material to form small holes / small troughs with sizes smaller than the vias / troughs, so that a protective material layer is retained on the inner wall of the vias / troughs; 3. The MEMS thin film manufacturing method according to claim 2, characterized in that, Depositing the protective material in the formed vias / troughs includes: Depositing a protective material in the formed vias / troughs using a plasma enhanced chemical vapor deposition process; Grinding and polishing the surface layer of the deposited protective material using a chemical mechanical polishing process; 4. The MEMS thin film manufacturing method according to claim 3, characterized in that, The protective material is one or more of silicon dioxide, silicon nitride, aluminum oxide, silicon carbide, polysilicon, and polyimide; 5. The MEMS thin film manufacturing method according to claim 4, wherein The thickness of the protective material layer retained on the inner wall of the vias / troughs is 1 / 12 - 1 / 4 of the width of the vias / troughs; 6. The MEMS thin film manufacturing method according to claim 5, characterized in that, Removing the filled filling material includes: Etching the filled filling material using a chemical etching process to completely remove the filling material; 7. The method for fabricating the MEMS thin film according to claim 1, wherein, Removing the filled filling material includes: Etching the filled filling material using an oxygen plasma etching process to completely remove the filling material; 8. The method for fabricating a MEMS thin film according to any one of claims 1-7, characterized in that Performing back cavity etching on the side of the wafer facing away from the thin film material using an inductively coupled plasma etching process includes: Using silicon dioxide, silicon nitride, or photoresist as an etching mask on the side of the wafer facing away from the thin film material; Etching the side of the wafer with the mask added using an inductively coupled plasma etching process; 9. The MEMS thin film manufacturing method according to any one of claims 1-7, characterized in that, The filling material is one or more of porous silicon, photoresist, silicon dioxide, polyimide, and polymethyl methacrylate; 10. A MEMS thin film sensor, which is fabricated by the MEMS thin film fabrication method according to any one of claims 1-9, characterized in that, The MEMS thin film sensor includes a thin film layer and a substrate stacked in sequence; at least one via / trough is provided in the thin film layer.

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