Preparation method of micromechanical suspended structure, micromechanical suspended structure and micromechanical sensor

Abstract

The invention provides a preparation method of a micro-mechanical suspended structure, the micro-mechanical suspended structure and a micro-mechanical sensor. The preparation method comprises the following steps: preparing a first mask layer with a groove structure on a first surface of a substrate layer; performing etching treatment and mask removal treatment on the substrate layer provided with the first mask layer to obtain a substrate layer with a groove structure; the side, with the groove structure, of the substrate layer is bonded with a preset bonding layer based on temporary bonding, so that a bonding structure comprising the substrate layer and the bonding layer is obtained; preparing a second mask layer with a second preset pattern on the second surface of the substrate layer; etching the second mask layer to obtain a bonding structure with a back cavity structure; performing bonding release on the bonding structure with the back cavity structure based on de-bonding so as to obtain a released suspended structure; and cleaning the released suspended structure to obtain the micro-mechanical suspended structure.

Description

Technical Field

[0001] The present application relates to the technical field of micromechanical sensors, and in particular to a method for preparing a micromechanical suspended structure, a micromechanical suspended structure and a micromechanical sensor. Background Art

[0002] MEMS sensor (Micro-ElectroMechanical System) is a new type of sensor manufactured based on microelectronics and micromechanical technology. The suspended structure in MEMS sensor is one of its core features. With the continuous development of MEMS technology, based on the application of DIRE (Deep Reactive Ion Etching), a series of MEMS device structures (i.e. suspended structures) with high aspect ratio silicon structures can be prepared.

[0003] In the prior art, a double-sided etching process is generally used to etch the front and back sides of a silicon wafer or the silicon layer and the substrate layer of a SOI silicon wafer (Silicon-On-Insulator) structure using DIRE to prepare a MEMS sensor with a suspended structure.

[0004] However, the inventors of the present application have discovered that in the process of preparing the suspended structure, the requirements for the bonding method are relatively high. During the bonding process, due to the influence of the bonding materials and the bonding method, problems such as etching stop, fragments, glue sticking, and inability to reliably release the bonding may easily occur, making the preparation of the suspended structure difficult. Summary of the invention

[0005] The present application provides a method for preparing a micromechanical suspended structure, a micromechanical suspended structure and a micromechanical sensor, which are used to solve the technical problem that in the current preparation of micromechanical suspended structures, etching stops, fragments, glue sticking and inability to reliably release the adhesive are easily caused during the bonding process due to the influence of adhesive materials and adhesive methods, making the preparation of suspended structures difficult.

[0006] According to one aspect of the present application, the present application provides a method for preparing a micromechanical suspended structure, including: preparing a first mask layer having a groove structure on a first surface of a base layer; etching and demasking the base layer provided with the first mask layer to obtain a base layer having a groove structure; bonding a side of the base layer having the groove structure to a preset bonding layer based on temporary bonding to obtain a bonding structure including the base layer and the bonding layer; preparing a second mask layer having a second preset pattern on a second surface of the base layer; etching the second mask layer to obtain a bonding structure having a back cavity structure; debonding the bonding structure having the back cavity structure based on debonding to obtain a released suspended structure; and cleaning the released suspended structure to obtain a micromechanical suspended structure.

[0007] According to some embodiments of the present application, preparing a first mask layer having a groove structure on a first surface of a base layer includes: sequentially performing a glue coating process, an exposure process, and a development process on the first surface to obtain a first mask layer having a groove structure.

[0008] According to some embodiments of the present application, at a first mask layer level having a groove structure, the first mask layer is used as a barrier layer, and a deep silicon etching process and a mask removal process are performed to obtain a base layer with a groove structure.

[0009] According to some embodiments of the present application, a side of a base layer having a groove structure is bonded to a preset bonding layer based on temporary bonding to obtain a bonding structure including a base layer and a bonding layer, including: setting a first bonding adhesive layer on a side of the base layer having a groove structure; setting a second bonding adhesive layer on one side of the bonding layer; and bonding the first bonding adhesive layer and the second bonding adhesive layer based on a temporary bonding device to obtain a bonding structure.

[0010] According to some embodiments of the present application, the released suspended structure is cleaned to obtain a micromechanical suspended structure, including: placing the released suspended structure in a degumming liquid and letting it stand for a first preset time to obtain a degummed suspended structure; placing the degummed suspended structure in a cleaning liquid and letting it stand for a second preset time to clean it; and air-drying and baking the cleaned suspended structure to obtain a micromechanical suspended structure.

[0011] According to some embodiments of the present application, the bonding layer is made of glass.

[0012] According to another aspect of the present application, the present application provides a micromechanical suspended structure. The micromechanical suspended structure is prepared by the preparation method as described above.

[0013] According to another aspect of the present application, the present application further provides a micromechanical sensor. The micromechanical sensor includes the micromechanical suspended structure as described above.

[0014] The present application bonds the base layer and the bonding layer through a temporary bonding process, and releases the bonding structure through a debonding process; based on the temporary bonding process, the base layer of the single-sided etching structure can be temporarily bonded to the bonding layer, avoiding the problems of etching stop, debris, glue sticking, and inability to reliably release the adhesive film caused by the double-sided etching structure during etching. And the present application ensures the integrity of the suspended structure through the debonding release process. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0016] Figure 1 A flow chart showing the preparation method of an embodiment of the present application;

[0017] Figure 2 A schematic diagram showing a substrate layer of an embodiment of the present application;

[0018] Figure 3 A schematic diagram showing a first mask layer of an embodiment of the present application;

[0019] Figure 4 A schematic diagram showing a groove structure of an embodiment of the present application;

[0020] Figure 5 Another schematic diagram showing the groove structure of an embodiment of the present application;

[0021] Figure 6 Another schematic diagram showing the preparation method of the embodiment of the present application;

[0022] Figure 7 A schematic diagram showing a first bonding adhesive layer according to an embodiment of the present application;

[0023] Figure 8 A schematic diagram showing a second bonding adhesive layer according to an embodiment of the present application;

[0024] Fig. 9 A schematic diagram showing a bonding structure of an embodiment of the present application;

[0025] Fig.10 A schematic diagram showing a second mask layer of an embodiment of the present application;

[0026] Fig.11 A schematic diagram showing a back cavity structure of an embodiment of the present application;

[0027] Fig.12A schematic diagram showing a released suspended structure according to an embodiment of the present application;

[0028] Fig.13 Another flow chart showing the preparation method of the embodiment of the present application;

[0029] Fig.14 A schematic diagram showing a micromechanical suspended structure according to an embodiment of the present application.

[0030] Description of reference numerals:

[0031] Base layer 10 ; first surface SA1 ; second surface SA2 ; first mask layer 20 ; groove structure 11 ; bonding layer 30 ; first bonding adhesive layer 12 ; second bonding adhesive layer 31 ; second mask layer 40 ; back cavity structure 13 . DETAILED DESCRIPTION

[0032] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this application will be comprehensive and complete and will fully convey the concepts of the example embodiments to those skilled in the art. The same reference numerals in the figures represent the same or similar parts, and thus their repeated description will be omitted.

[0033] The described features, structures or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced without one or more of these specific details, or other modes, components, materials, devices, etc. may be adopted. In these cases, known structures, methods, devices, implementations, materials or operations will not be shown or described in detail.

[0034] In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units that are not listed, or may optionally include other steps or units that are inherent to these processes, methods, products or devices.

[0035] The terms "first", "second" and the like in the specification and claims of this application and the above drawings are used to distinguish different objects rather than to describe a specific order.

[0036] The following is a clear and complete description of the technical solution of the present application in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0037] The steps for preparing the suspended structure based on the double-sided etching process generally include the following steps:

[0038] S1: etching the substrate layer based on DIRE to form a chamber;

[0039] S2: removing the exposed silicon dioxide in the base layer chamber by wet or dry etching and bonding the companion wafer;

[0040] S3: Etching the structural layer of the SOI silicon wafer to form a suspended structure.

[0041] The commonly used bonding companion wafers or other bonding methods (SOI silicon wafers without bonding companion wafers) in the prior art generally include:

[0042] 1. Use silicone oil to bond a wafer with one side structure etched to another complete wafer. When etching the back silicon, due to the problem of etching uniformity at the wafer level, the edge structure is etched first, exposing the silicone oil, making the etching process ineffective.

[0043] 2. Use photoresist to bond a wafer with one side structure etched to another complete wafer. When etching the back silicon, it will be limited by the bonding effect of the bonding surface. In the presence of a cavity, the etching process will cause heat accumulation in the cavity, resulting in problems such as photoresist paste and wafer fragmentation, and there is also the problem of being unable to reliably release the bonding.

[0044] 3. When using SOI silicon wafers, after etching the SOI silicon wafer structure layer, when etching the base layer, at the moment of etching to the buried oxide layer, the buried oxide layer will be deformed and cracked due to its own stress. For some suspended structures with large gaps and small structural line widths, the rupture of the buried oxide layer can easily lead to the rupture of the silicon structure and stop etching.

[0045] According to one aspect of the present application, the present application provides a method for preparing a micromechanical suspended structure based on bonding technology.

[0046] like Figure 1 As shown, the preparation method includes steps S100-S700.

[0047] According to example embodiments, in step S100 , a first mask layer having a groove structure is prepared on a first surface of a base layer.

[0048] like Figure 2 As shown, the base layer 10 includes a first surface SA1 and a second surface SA2. For example, the base layer 10 may be a silicon wafer or a SOI silicon wafer. Figure 3 As shown, a first mask layer 20 is prepared on the first surface SA1 of the base layer 10 .

[0049] Optionally, step S100 may further include: sequentially performing a coating process, an exposure process, and a development process on the first surface SA1 to obtain a first mask layer 20 with a groove structure.

[0050] For example, a photoresist coating may be performed on the first surface SA1, and then the mask layer is exposed by scanning a laser beam, and the denatured photoresist layer is removed by wet etching after development, thereby obtaining a mask pattern having a first preset pattern (such as Figure 3 The first mask layer 20 having a groove structure is shown in FIG.

[0051] In step S200 , the base layer 10 provided with the first mask layer 20 is subjected to an etching process and a mask removal process to obtain the base layer 10 having the groove structure 11 .

[0052] like Figure 4 As shown, based on the first mask layer 20 (photoresist layer) as the mask layer, etching is performed based on the deep silicon etching process to obtain the groove structure 11. And as Figure 5 As shown, the base layer 10 is subjected to a mask removal process (eg, removing the remaining unetched photoresist layer by plasma), so as to obtain the base layer 10 having the groove structure 11 .

[0053] In step S300 , the side of the base layer 10 having the groove structure 11 is bonded to the preset bonding layer 30 based on temporary bonding to obtain a bonding structure including the base layer 10 and the bonding layer 30 .

[0054] Temporary bonding is a technology used to temporarily fix and support wafers during semiconductor manufacturing and micro-electromechanical system manufacturing. For example, the base layer 10 and the bonding layer 30 are bonded together by a temporary bonding process to form a bonding structure including the base layer 10 and the bonding layer 30.

[0055] The double-sided structure etching process based on temporary bonding in this application can perform high-quality wafer bonding at the wafer level with a good line of sight. With this arrangement, there is no problem of silicone oil leakage caused by etching uniformity, which makes etching ineffective. Compared with photoresist wafer bonding, the wafer bonding method provided by this application also does not cause etching paste or fragments due to large-sized cavities.

[0056] Alternatively, if Figure 6As shown, step S300 may also include steps S310-S330.

[0057] In step S310, Figure 7 As shown, a first bonding adhesive layer 12 is disposed on the side of the base layer 10 having the groove structure 11 .

[0058] For example, a temporary bonding glue (such as TB4130 bonding glue) with a certain thickness is spin-coated on the surface of the groove structure 11. Exemplarily, the coating parameters of the temporary bonding glue may be:

[0059] Speed ​​parameter: 1000rpm@30s;

[0060] Baking parameters: 115℃@10min; 220℃@10min;

[0061] Coating thickness parameter: 60um.

[0062] In step S320, Figure 8 As shown, a second bonding adhesive layer 31 is disposed on one side of the bonding layer 30 .

[0063] Optionally, the bonding layer 30 may be made of glass.

[0064] For example, the bonding layer 30 may be a glass sheet, and a photosensitive bonding adhesive (such as LB210 bonding adhesive) is coated on one surface of the glass sheet. Exemplarily, the coating parameters of the photosensitive bonding adhesive may be:

[0065] Speed ​​parameters: 300rpm@10s; 1000rpm@30s;

[0066] Baking parameters: 115℃@10min; 250℃@20mi;

[0067] Coating thickness parameter: 0.35um.

[0068] In step S330, the first bonding adhesive layer 12 and the second bonding adhesive layer 31 are bonded together using a temporary bonding device to obtain a Fig. 9 The bonding structure shown.

[0069] For example, a temporary bonding device is used to bond a wafer coated with a temporary bonding adhesive and a glass sheet coated with a photosensitive bonding adhesive together by heat pressing. Exemplarily, the bonding parameters of the temporary bonding device may be:

[0070] Pressure parameter: 150g / cm 2 ;

[0071] Temperature parameters: 220℃;

[0072] Vacuum parameters: 0.1torr;

[0073] Time parameter: 10min.

[0074] In step S400, Fig.10 As shown, a second mask layer 40 having a second preset pattern is prepared on the second surface SA2 of the base layer 10 .

[0075] In step S500 , the second mask layer 40 is etched to obtain a bonding structure with a back cavity structure.

[0076] For example, after the temporary bonding is completed, the wafer silicon surface is subjected to double-sided alignment photolithography to form a second mask layer 40 (such as a photoresist mask layer) having a second preset pattern. Exemplarily, the second preset pattern can be customized according to user needs.

[0077] Based on the second mask layer 40 as an etching mask, the bonding structure is etched by deep silicon etching process until it is suspended, so as to form Fig.11 The back cavity structure 13 is shown.

[0078] In step S600, the bonding structure with the back cavity structure is debonded based on debonding to obtain a released suspended structure.

[0079] Debonding is a process used to separate temporarily bonded wafers from carriers during wafer fabrication. Fig.12 As shown, a laser debonding device is used on the glass surface of the bonding layer 30 to release the bonding between the bonding layer 30 and the base layer 10, thereby obtaining a released suspended structure.

[0080] Exemplarily, the debonding parameters of the laser debonding device may be:

[0081] Laser power: 5W;

[0082] Ability: 60%;

[0083] Frequency: 5000Hz;

[0084] Scanning speed: 2100mm / s;

[0085] Scanning depth: 0.420mm;

[0086] Energy density: 360mj / cms.

[0087] Through the above embodiments, the present application releases double-sided structure etching based on a temporary debonding process. Compared with release processes such as thermal slip and solution immersion, the release method uses a laser to scan the photosensitive bonding glue through the bonding layer to release the stickiness. This does not cause damage to the suspended structure and can ensure the release integrity of the suspended structure.

[0088] In step S700 , the released suspended structure is cleaned to obtain a micromechanical suspended structure.

[0089] Alternatively, if Fig.13 As shown, step S700 may also include steps S710-S730.

[0090] In step S710, the released suspended structure is placed in a degumming solution and allowed to stand for a first preset time to obtain a degummed suspended structure.

[0091] In step S720, the debonded suspended structure is placed in a cleaning solution and left to stand for a second preset time for cleaning.

[0092] In step S730, the cleaned suspended structure is air-dried and baked to obtain a micromechanical suspended structure.

[0093] For example, the released suspended structure also includes a first bonding adhesive layer 12, so the base layer 10 with the suspended structure is placed in a flower basket and immersed in a temporary bonding adhesive remover. After standing for a certain period of time (such as 30 minutes), the base layer 10 is placed in a cleaning solution (such as isopropanol) and allowed to stand for a certain period of time (such as 5 minutes), and then air-dried and dried (the drying temperature can be 120°C), and finally obtained as shown in the figure. Fig.14 The micromechanical suspended structure shown in FIG. 4 . Exemplarily, the suspended structure released after debonding can be simultaneously freed from the debonding liquid on both sides during the process of soaking in the debonding liquid, and can achieve efficient and high-yield wafer-level release.

[0094] Through the above exemplary embodiments, the present application bonds the base layer and the bonding layer through a temporary bonding process, and releases the bonding structure through a debonding process; based on the temporary bonding process, the base layer of the single-sided etching structure can be temporarily bonded to the bonding layer, avoiding the problems of etching stop, debris, glue sticking, and inability to reliably release the adhesive film caused by the double-sided etching structure during etching. And the present application ensures the integrity of the suspended structure through the debonding release process.

[0095] Compared with the method of etching the structural layer and then etching the base layer using an SOI silicon wafer, the double-sided structural etching method based on the temporary bonding process of the present application can at least solve the following problems:

[0096] 1. This application solves the problem that when etching the base layer, the buried oxide layer will be deformed and cracked due to its own stress at the moment of etching to the buried oxide layer;

[0097] 2. This application solves the problem that for suspended structures with large gaps and small structural line widths, the rupture of the buried oxide layer easily leads to the rupture of the silicon structure, causing the etching to stop;

[0098] 3. This application can leave a certain space for the design of the device structure, which can solve the device processing problem that the gap cannot be reduced at present.

[0099] According to another aspect of the present application, the present application provides a micromechanical suspended structure. The micromechanical suspended structure is prepared by the preparation method as described above.

[0100] According to another aspect of the present application, the present application further provides a micromechanical sensor. The micromechanical sensor includes the micromechanical suspended structure as described above.

[0101] Finally, it should be noted that the above is only a preferred embodiment of the present application and is not intended to limit the present application. Although the present application is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions of the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a micromechanical suspended structure based on bonding technology, characterized in that: include: Preparing a first mask layer having a groove structure on a first surface of the base layer; Performing etching and mask removal on the base layer provided with the first mask layer to obtain a base layer with a groove structure; Bonding the side of the base layer having the groove structure to a preset bonding layer based on temporary bonding to obtain a bonding structure including the base layer and the bonding layer; Preparing a second mask layer having a second preset pattern on the second surface of the base layer; Performing etching on the second mask layer to obtain a bonding structure with a back cavity structure; Based on debonding, the bonding structure with the back cavity structure is released to obtain a released suspended structure; The released suspended structure is cleaned to obtain the micromechanical suspended structure.

2. The preparation method according to claim 1, characterized in that: The step of preparing a first mask layer having a groove structure on the first surface of the base layer comprises: The first surface is sequentially subjected to a coating process, an exposure process, and a development process to obtain the first mask layer with a groove structure.

3. The preparation method according to claim 1, characterized in that: The step of bonding the side of the base layer having the groove structure to a preset bonding layer based on temporary bonding to obtain a bonding structure including the base layer and the bonding layer comprises: Disposing a first bonding adhesive layer on a side of the base layer having the groove structure; Disposing a second bonding adhesive layer on one side of the bonding layer; The first bonding adhesive layer and the second bonding adhesive layer are bonded and connected based on a temporary bonding device to obtain the bonding structure.

4. The preparation method according to claim 1, characterized in that: The step of cleaning the released suspended structure to obtain the micromechanical suspended structure includes: placing the released suspended structure into a degumming solution and leaving it to stand for a first preset time to obtain a degummed suspended structure; placing the degummed suspended structure in a cleaning solution and leaving it to stand for a second preset time for cleaning; The cleaned suspended structure is air-dried and baked to obtain the micromechanical suspended structure.

5. The preparation method according to claim 1, characterized in that: The bonding layer is made of glass.

6. A micromechanical suspended structure, characterized in that: The micromechanical suspended structure is prepared based on the preparation method according to any one of claims 1-5.

7. A micromechanical sensor, characterized in that: It comprises the micromechanical suspended structure as claimed in claim 6.

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