A MEMS film manufacturing method and MEMS film sensor

Abstract

The present invention discloses a method for fabricating a MEMS thin film and a MEMS thin film sensor. The method comprises: using a reactive ion etching process to locally etch a thin film material on the surface of a wafer to form a through hole / through groove; using a coating process or a deposition process to fill a filling material into the through hole / through groove formed in the above step; 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 that retains the thin film material. The above-mentioned MEMS thin film fabrication method uses a filling material to cover the through hole / through groove, ensuring that the thin film will not be penetrated from top to bottom during the back cavity etching process of the wafer, greatly improving the production efficiency of non-enclosed thin film structures, and can efficiently and reliably process MEMS sensors with non-enclosed thin film structures.

Description

Technical Field

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

[0002] Some MEMS (Micro-Electro-Mechanical System) sensors, such as thermopile sensors, require an internal cavity structure with a suspended membrane above it to achieve specific functionality. In MEMS sensors, the membrane is a crucial component of their functionality and determines whether the device meets design requirements. Membrane structures typically include closed membranes, closed membranes with open pores, and cantilever beams. Several methods are available for releasing closed membranes with open pores and cantilever beams, including using anisotropic TMAH etching, pre-filling a sacrificial layer beneath the membrane and then etching the sacrificial material to create a cavity. Alternatively, a temporary bonding process can be used to etch the open pores or cantilever structure, followed by temporary bonding of the wafers. Inductively coupled plasma etching (ICP) etching is then used to etch the bulk silicon from the backside, followed by debonding (as described in patent CN114852952B).

[0003] In existing ICP (Inductively Coupled Plasma) etching processes, conventional steps can only produce closed thin film structures. However, the use of a die ring, as employed in patent CN114852952B, can result in uneven heating of the wafer to be etched during the etching process, as the wafer is not in contact with the etching machine's stage. This can lead to poor uniformity in the etching chamber. Without the die ring approach described in the aforementioned patent, directly bonding the wafer to the wafer to be etched with glue requires debonding after etching, potentially making adhesive removal difficult, preventing separation of the wafer from the wafer, leaving glue residue, and potentially causing film breakage. Therefore, existing methods for fabricating MEMS thin films suffer from the inability to efficiently and reliably produce non-closed thin film structures. Summary of the Invention

[0004] The embodiments of the present invention provide a MEMS thin film manufacturing method and a MEMS thin film sensor, aiming to solve the problem in the prior art that a non-enclosed thin film structure cannot be obtained by efficient and reliable processing.

[0005] In a first aspect, an embodiment of the present application provides a method for fabricating a MEMS thin film, wherein the method is used to etch a wafer to fabricate a thin film, wherein the wafer includes a thin film material and a substrate stacked in sequence, and the method includes:

[0006] Using a reactive ion etching process to locally etch the thin film material on the wafer surface to form a through hole / through groove;

[0007] Filling the through-holes / through-grooves formed in the above steps with a filling material using a coating process or a deposition process;

[0008] Performing back cavity etching on a side of the wafer facing away from the thin film material using an inductively coupled plasma etching process;

[0009] The filling material is removed to obtain a thin film structure with the thin film material retained.

[0010] The MEMS thin film manufacturing method, wherein, before using a coating process or a deposition process to fill the filling material into the through hole / through groove formed in the above step, further comprises:

[0011] depositing a protective material in the formed through-hole / through-groove;

[0012] The deposited protective material is subjected to reactive ion etching to form a small hole / small groove smaller in size than the through hole / through groove, and a layer of protective material is retained on the inner wall of the through hole / through groove.

[0013] The MEMS thin film manufacturing method, wherein the step of depositing a protective material in the formed through hole / through groove comprises:

[0014] Depositing a protective material in the formed through-hole / through-trench using a plasma enhanced chemical vapor deposition process;

[0015] The deposited protective material surface layer is ground and polished using a chemical mechanical polishing process.

[0016] In the MEMS film manufacturing method, the protective material is one or more of silicon dioxide, silicon nitride, aluminum oxide, silicon carbide, polysilicon, and polyimide.

[0017] In the MEMS film manufacturing method, the thickness of the protective material layer retained on the inner wall of the through hole / through groove is 1 / 12-1 / 4 of the width of the through hole / through groove.

[0018] The MEMS film manufacturing method, wherein the removing of the filling material includes:

[0019] The filled filling material is etched using a chemical etching process to completely remove the filling material.

[0020] The MEMS film manufacturing method, wherein the removing of the filling material includes:

[0021] The filled filling material is etched using an oxygen plasma etching process to completely remove the filling material.

[0022] The MEMS thin film manufacturing method, wherein the inductively coupled plasma etching process is used to perform back cavity etching on the side of the wafer away from the thin film material, comprises:

[0023] Using silicon oxide, silicon nitride or photoresist as an etching mask on the side of the wafer facing away from the thin film material;

[0024] The masked side of the wafer is etched using an inductively coupled plasma etching process.

[0025] In the MEMS film manufacturing method, the filling material is one or more of porous silicon, photoresist, silicon dioxide, polyimide, and polymethyl methacrylate.

[0026] In a second aspect, an embodiment of the present application further provides a MEMS thin film sensor, which is manufactured by the MEMS thin film manufacturing method as described in the first aspect above, wherein the MEMS thin film sensor includes a thin film layer and a substrate stacked in sequence; the thin film layer is provided with at least one through hole / through groove.

[0027] An embodiment of the present invention provides a method for fabricating a MEMS thin film and a MEMS thin film sensor. The method includes: using a reactive ion etching process to locally etch the thin film material on the surface of a wafer to form a through hole / through groove; using a coating process or a deposition process to fill the through hole / through groove formed in the above step with a filling material; using an inductively coupled plasma etching process to perform back cavity etching on the side of the wafer away from the thin film material; and removing the filled filling material to obtain a thin film structure that retains the thin film material. The above-mentioned MEMS thin film fabrication method uses the filling material to cover the through hole / through groove, ensuring that the thin film will not be penetrated from top to bottom during the back cavity etching process of the wafer, greatly improving the production efficiency of non-enclosed thin film structures, and can efficiently and reliably process MEMS sensors with non-enclosed thin film structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 A flow chart of a method for fabricating a MEMS thin film according to an embodiment of the present invention;

[0030] Figure 2 Another flow chart of the method for manufacturing a MEMS thin film according to an embodiment of the present invention;

[0031] Figure 3 A schematic diagram of the processing process of the MEMS thin film manufacturing method provided by an embodiment of the present invention;

[0032] Figure 4 A schematic diagram of another process of the MEMS film manufacturing method provided by an embodiment of the present invention;

[0033] Figure 5 A cross-sectional structural diagram of a MEMS thin film sensor provided by an embodiment of the present invention;

[0034] Reference numerals: 1. substrate; 2. film layer; 3. protective material; 4. filling material; 5. back cavity; 21. through groove. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0036] It will be understood that when used in this specification and the appended claims, the terms “comprises” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0037] It should also be understood that the terminology used in this specification is for the purpose of describing specific embodiments only and is not intended to limit the present invention. As used in this specification and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly indicates otherwise. It should further be understood that the term "and / or" as used in this specification and the appended claims refers to any and all possible combinations of one or more of the associated listed items, including and including these combinations.

[0038] The specific embodiment of the present application discloses a method for manufacturing a MEMS thin film, wherein the method is used to etch a wafer to manufacture a thin film, wherein the wafer comprises a thin film material and a substrate stacked in sequence, and the initial structure of the wafer is as follows: Figure 3 As shown in (a) or Figure 4 See (a) in the figure. Figure 1 As shown in the figure, the wet etching processing method in the first embodiment of the present application includes steps S1 to S4.

[0039] S1. Use reactive ion etching process to locally etch the thin film material on the surface of the wafer to form a through hole / through groove.

[0040] First, the thin film on the wafer surface can be partially etched by reactive ion etching (RIE) to form through holes / grooves on the thin film material on the wafer surface. Figure 3 (b) and Figure 4 As shown in (b), a plurality of through holes / through grooves 21 are formed on the thin film material on the surface of the wafer by RIE process.

[0041] S2. Filling the through holes / through grooves formed in the above steps with a filling material using a coating process or a deposition process.

[0042] Then, fill the through hole / through groove formed in the above steps with a filling material 4. Specifically, a coating process or a deposition process can be used to fill the through hole / through groove. The coating process can be spin coating or spray coating; 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 as the filling material. The specific implementation steps are as follows: Figure 3 As shown in (c), the corrosive agent used to remove the filling material does not damage the original wafer material, so there is no need to fill the protective material.

[0043] See also Figure 2 As shown in the figure, the MEMS film fabrication 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 corrosive agent used to remove the filler material may damage the original wafer material. S11: depositing a protective material within the formed through-hole / through-groove; S12: performing reactive ion etching (RIE) on the deposited protective material to form a small hole / small groove smaller than the through-hole / through-groove, so that a layer of protective material remains on the inner wall of the through-hole / through-groove.

[0044] A protective material may be deposited in the formed through hole / through groove, and the device structure obtained after depositing the protective material is as follows: Figure 4 As shown in (c). The specific operation method of depositing the protective material can be any one or more combinations of PVD, CVD, spin coating, and spray coating. The deposited protective material is further subjected to reactive ion etching to obtain a small hole or small groove. The size of the small hole / small groove is smaller than that of the through hole / through groove. The resulting device structure is as follows: Figure 4 As shown in (d). Figure 4 Based on the device shown in (d), the above step S2 is used to further fill the filling material, and the resulting device structure is as follows Figure 4 As shown in (e).

[0045] In a specific embodiment, depositing a protective material in the formed through-hole / through-groove specifically includes: using a plasma enhanced chemical vapor deposition process (PECVD, Plasma Enhanced Chemical Vapor Deposition) to deposit the protective material 3 in the formed through-hole / through-groove; and using a chemical mechanical polishing process (CMP, Chemical Mechanical Polishing) to grind and polish the surface of the deposited protective material 3.

[0046] 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 selected as silicon nitride. Furthermore, in order to ensure that the protective material can form a good protective 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 through hole / through groove width. For example, if the thickness of the protective material layer is 1 / 12 of the through hole / through groove width, the remaining width between the two protective material layers is 5 / 6 of the through hole / through groove width; if the thickness of the protective material layer is 1 / 4 of the through hole / through groove width, the remaining width between the two protective material layers is 1 / 2 of the through hole / through groove width.

[0047] Furthermore, the specific step of removing the filling material includes: using a chemical etching process to corrode the filled filling material to completely remove the filling material. Since the protective material is deposited in the through hole / through groove and a protective material layer is obtained, the filling material can be removed without considering the problem of corrosive agents causing damage to the original wafer material. In the specific application process, the protective material can not only fill the through hole / through groove, but also cover other positions of the wafer. If necessary, the protective material can also be deposited on the top surface of the wafer, or the protective material can be added between the substrate and the thin film material to avoid affecting the device performance or thin film reliability when removing the filling material.

[0048] S3. Using an inductively coupled plasma etching process, perform back cavity etching on the side of the wafer away from the thin film material.

[0049] The inductively coupled plasma (ICP) etching process can be used to perform back cavity etching on the side of the wafer away from the thin film material, that is, etching the back of the wafer to form a back cavity 5. The device structure obtained after etching is as follows Figure 3 Middle (d) and Figure 4 As shown in (f).

[0050] In a more specific embodiment, the step of performing back cavity etching includes: using silicon oxide, silicon nitride or photoresist as an etching mask on the side of the wafer facing away from the thin film material; and etching the side of the wafer to which the mask is added using an inductively coupled plasma etching process, so that the pattern / area etched at this time corresponds to the etching mask.

[0051] S4, removing the filling material to obtain a thin film structure with the thin film material retained.

[0052] Furthermore, the filling material in the through hole / through groove can be removed to obtain a thin film structure retaining the thin film material. At this time, the substrate below the thin film structure is etched to form a cavity. The obtained device structure is as follows: Figure 3 Middle (e) and Figure 4 As shown in (g).

[0053] After completing the above steps, the device may be subjected to post-processing, such as annealing or heat treatment, etc. In addition, the filling material may be removed by using one or more of chemical dissolution, plasma etching, heat treatment, and electrochemical dissolution.

[0054] More specifically, an oxygen plasma etching process can be used to etch the filled filling material to completely remove the filling material; when the protective material is not deposited and a protective material layer is obtained, a corrosive agent that does not damage the original wafer material is required, and an oxygen plasma etching process can be used to remove the filling material. This process method does not damage the original wafer material.

[0055] Compared to existing technologies, this invention is compatible with any thin-film hole or slotting process, requires no fixtures, and is completely based on semiconductor processes. During ICP etching (or ICP-RIE etching), it ensures uniform heating of the wafer, improving etching uniformity.

[0056] The embodiment of the present invention further provides a MEMS thin film sensor, which is manufactured by the MEMS thin film manufacturing method described in the above embodiment. Figure 5 As shown, the MEMS thin film sensor includes a thin film layer 2 and a substrate 1 stacked in sequence; the thin film layer 2 is provided with at least one through hole / through groove 21. Since the through hole / through groove 21 is provided in the thin film layer 2, the sensor is a MEMS sensor with an open thin film structure.

[0057] An embodiment of the present invention provides a method for fabricating a MEMS thin film and a MEMS thin film sensor. The method includes: using a reactive ion etching process to locally etch the thin film material on the surface of a wafer to form a through hole / through groove; using a coating process or a deposition process to fill the through hole / through groove formed in the above step with a filling material; using an inductively coupled plasma etching process to perform back cavity etching on the side of the wafer away from the thin film material; and removing the filled filling material to obtain a thin film structure that retains the thin film material. The above-mentioned MEMS thin film fabrication method uses the filling material to cover the through hole / through groove, ensuring that the thin film will not be penetrated from top to bottom during the back cavity etching process of the wafer, greatly improving the production efficiency of non-enclosed thin film structures, and can efficiently and reliably process MEMS sensors with non-enclosed thin film structures.

[0058] 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 person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A method for manufacturing a MEMS thin film, characterized in that: The MEMS thin film manufacturing method is used to etch a wafer to produce a thin film, wherein the wafer includes a thin film material and a substrate stacked in sequence, and the thin film material is in contact with the substrate. The method includes: locally etching the thin film material on the surface of the wafer using a reactive ion etching process to form a through hole / through groove in the thin film material; Filling the formed through-hole / through-groove with a filling material using a coating process or a deposition process; Using an inductively coupled plasma etching process, etching a side of the substrate away from the thin film material to form a back cavity, so as to expose a surface of the thin film material close to the substrate; removing the filling material to obtain a thin film structure retaining the thin film material; Before filling the formed through hole / through groove with the filling material using a coating process or a deposition process, the method further includes: depositing a protective material in the formed through-hole / through-groove; The deposited protective material is subjected to reactive ion etching to form a small hole / small groove smaller in size than the through hole / through groove, and a layer of protective material is retained on the inner wall of the through hole / through groove.

2. The MEMS thin film manufacturing method according to claim 1, characterized in that: The step of depositing a protective material in the formed through hole / through groove comprises: Depositing a protective material in the formed through hole / trench using a plasma enhanced chemical vapor deposition process; The deposited protective material surface layer is ground and polished using a chemical mechanical polishing process.

3. The MEMS thin film manufacturing method according to claim 2, characterized in that: The protective material is one or more of silicon dioxide, silicon nitride, aluminum oxide, silicon carbide, polysilicon, and polyimide.

4. The method for manufacturing a MEMS thin film according to claim 3, wherein: The thickness of the protective material layer retained on the inner wall of the through hole / through groove is 1 / 12-1 / 4 of the width of the through hole / through groove.

5. The method for manufacturing a MEMS thin film according to claim 4, wherein: The step of removing the filling material comprises: The filled filling material is etched using a chemical etching process to completely remove the filling material.

6. The MEMS thin film manufacturing method according to claim 1, characterized in that: The step of removing the filling material comprises: The filled filling material is etched using an oxygen plasma etching process to completely remove the filling material.

7. The method for manufacturing a MEMS thin film according to any one of claims 1 to 6, characterized in that: The inductively coupled plasma etching process is used to etch a side of the substrate away from the thin film material to form a back cavity, so as to expose a surface of the thin film material close to the substrate, comprising: Using silicon oxide, silicon nitride or photoresist as an etching mask on the side of the substrate facing away from the thin film material; The masked side of the wafer is etched using an inductively coupled plasma etching process to expose a surface of the thin film material close to the substrate.

8. The method for manufacturing a MEMS thin film according to any one of claims 1 to 6, characterized in that: The filling material is one or more of porous silicon, photoresist, silicon dioxide, polyimide, and polymethyl methacrylate.

9. A MEMS thin film sensor, manufactured by the MEMS thin film manufacturing method according to any one of claims 1 to 8, characterized in that: The MEMS thin film sensor includes a thin film layer and a substrate stacked in sequence; the thin film layer is provided with at least one through hole / through groove.

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