Gas sensor and preparation method thereof

Abstract

The invention discloses a gas sensor and a preparation method thereof. The preparation method comprises the following steps: preparing a plurality of heating layers and a plurality of electrodes in one-to-one connection with the heating layers on a first substrate; preparing a covering layer covering the heating layer and the electrode; preparing a plurality of release grooves based on the covering layer; etching the first substrate by a predetermined depth through the partial release groove; obtaining a cover plate layer with an oxide layer; bonding the side, with the covering layer, of the device layer with the side, with the oxide layer, of the cover plate layer; the cover plate layer is slotted to obtain a measurement channel, the measurement channel extends to the covering layer containing part of the heating layer and the electrode, and part of the heating layer between the cover plate layer and the release groove forms a reference channel. The volume of the gas sensor is reduced, the packaging complexity is reduced, and the preparation cost is reduced.

Description

Technical Field

[0001] The present application relates to the field of gas detection technology, and in particular to a gas sensor and a preparation method thereof. Background Art

[0002] The principle of thermal conductivity gas sensor is based on the fact that different gas molecules have different thermal conductivities. In order to improve the measurement accuracy, thermal conductivity gas sensor generally includes two channels, namely reference channel and measurement channel. The reference channel is exposed to the air, and the measurement channel is exposed to the measured air. The two channels are heated to the same temperature, and the concentration of the measured gas molecules in the measured air is obtained based on the data difference between the two channels. The existing thermal conductivity gas sensor chips are all made of two identical units, one of which is sealed as a reference channel through a packaging process, and the other unit is exposed to the air as a measurement channel. However, due to the low precision of the packaging of the prior art, and the need to reserve additional space for packaging, the packaging process is complicated and the gas sensor is large in size. Summary of the invention

[0003] Based on this, it is necessary to provide a method for preparing a gas sensor. The method for preparing a gas sensor of the present invention has a simple packaging process and the prepared gas sensor has a small volume.

[0004] An embodiment of the present application provides a method for preparing a gas sensor.

[0005] A method for preparing a gas sensor comprises the following steps:

[0006] Prepare the device layer: obtain a first substrate; prepare a plurality of heating layers and a plurality of electrodes respectively connected to the heating layers on the first substrate; prepare a covering layer covering the heating layers and the electrodes on the first substrate; prepare a plurality of release grooves based on the covering layer, wherein some of the release grooves leak out the electrodes and some of the release grooves extend to the first substrate; and, through some of the release grooves, etch the first substrate to a predetermined depth to form a plurality of independent release spaces, wherein each of the release spaces is distributed corresponding to a plurality of the heating layers;

[0007] obtaining a cover layer including an oxide layer;

[0008] Bonding a side of the device layer having the cover layer to a side of the cover plate layer having the oxide layer;

[0009] Furthermore, the cover plate layer is grooved to obtain a measurement channel, the measurement channel extends to a portion of the release space, and a reference channel is formed between the cover plate layer and a portion of the release space.

[0010] In some of the embodiments, the measuring channel simultaneously extends to one of the release spaces and contains a portion of the heating layer, so that the measuring channel leaks out a portion of the heating layer and the electrode.

[0011] In some of the embodiments, the following steps are also included: after obtaining the first substrate, preparing a support layer on the first substrate, preparing a heating layer and an electrode on the support layer; and preparing the covering layer on the support layer.

[0012] In some embodiments, the support layer includes one or both of silicon oxide and silicon nitride.

[0013] In some of the embodiments, when preparing the supporting layer on the first substrate, one or more of LPCVD, PECVD and TEOS processes are adopted.

[0014] In some embodiments, the thickness of the support layer is 200 nm to 2 μm.

[0015] In some embodiments, the first substrate comprises a silicon wafer.

[0016] In some embodiments, the heating layer is made of one or more materials selected from the group consisting of W, Pt, Au, and doped polysilicon.

[0017] In some embodiments, the electrode is made of one or more materials selected from the group consisting of Pt, Au, and Al.

[0018] In some embodiments, the thickness of the heating layer is 200 nm to 2 μm.

[0019] In some embodiments, the thickness of the electrode is 200 nm to 2 μm.

[0020] In some embodiments, the capping layer includes one or both of silicon oxide and silicon nitride.

[0021] In some of the embodiments, when preparing the covering layer, one or more of LPCVD, PECVD and TEOS processes are adopted.

[0022] In some embodiments, the thickness of the covering layer is 200 nm to 2 μm.

[0023] In some embodiments, the first substrate is etched through a portion of the release groove to a predetermined depth of 5 μm to 100 μm.

[0024] In some embodiments, obtaining a cover layer containing an oxide layer includes the following steps:

[0025] obtaining a second substrate;

[0026] preparing a first mask layer on the second substrate;

[0027] Patterning the first mask layer;

[0028] Performing a groove process on the second substrate based on the patterned first mask layer to obtain a plurality of groove bodies respectively corresponding to the release grooves;

[0029] And, an oxide layer is prepared on the second substrate after the groove processing.

[0030] In some embodiments, the first mask layer includes an oxide layer, a nitride layer or a photoresist.

[0031] In some of the embodiments, when preparing the first mask layer, one or more of LPCVD, PECVD and TEOS processes are used.

[0032] In some embodiments, the thickness of the first mask layer is 200 nm-2 μm.

[0033] In some embodiments, when patterning the first mask layer, one or both of laser etching and photolithography etching methods are used.

[0034] In some embodiments, when the second substrate is grooved, the depth of the grooves is 5 μm to 100 μm.

[0035] In some of the embodiments, when preparing the oxide layer, one or more of LPCVD, PECVD and TEOS processes are used.

[0036] In some embodiments, the oxide layer has a thickness of 1 μm to 5 μm.

[0037] In some of the embodiments, after bonding the device layer to the cover layer, a step of thinning the device layer and the cover layer is further included.

[0038] In some embodiments, the overall thickness of the device layer and the cover layer after thinning is 50 μm to 200 μm.

[0039] In some embodiments, when the cover plate layer is grooved to obtain the measuring channel, the following steps are included:

[0040] preparing a second mask layer on the bonded cover plate layer;

[0041] Part of the second mask layer and the cover plate layer is grooved to obtain a measurement channel, and the measurement channel extends to the cover layer.

[0042] In some embodiments, the second mask layer includes an oxide layer, a nitride layer or a photoresist.

[0043] In some of the embodiments, when preparing the second mask layer, one or more of LPCVD, PECVD and TEOS processes are adopted.

[0044] In some embodiments, the thickness of the second mask layer is 200 nm-2 μm.

[0045] An embodiment of the present application also provides a gas sensor.

[0046] A gas sensor is prepared by any one of the above preparation methods.

[0047] In some embodiments, the gas sensor includes a first substrate, a supporting layer, a plurality of heating layers, a plurality of electrodes, a covering layer, and a cover plate layer. The first substrate is provided with a plurality of release grooves. The first substrate is provided with a supporting layer. The plurality of heating layers and the plurality of electrodes are distributed on the supporting layer. Each of the release grooves corresponds to a plurality of the heating layers. The covering layer covers the first substrate and encapsulates one of the release grooves to form a reference channel. The cover plate layer has a measurement channel corresponding to one of the release grooves, and the electrode leaks out of the measurement channel.

[0048] The preparation method of the above-mentioned gas sensor realizes wafer-level packaging of the device layer and the cover layer by bonding, and the packaging process is sophisticated. During the preparation process, the reference channel is directly packaged through the cover layer, and the measurement channel is obtained by grooving part of the second mask layer and the cover layer. Such a processing technology can reduce the volume of the gas sensor, reduce the packaging complexity, and reduce the preparation cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative work.

[0050] In order to more completely understand the present application and its beneficial effects, the following description will be given in conjunction with the accompanying drawings. In the following description, the same reference numerals represent the same parts.

[0051] Figure 1 A schematic diagram of a process for preparing a gas sensor according to an embodiment of the present invention;

[0052] Figure 2A schematic diagram of one step of the method for preparing a gas sensor according to Example 1 of the present invention;

[0053] Figure 3 A schematic diagram of one step of the method for preparing a gas sensor according to Example 1 of the present invention;

[0054] Figure 4 A schematic diagram of one step of the method for preparing a gas sensor according to Example 1 of the present invention;

[0055] Figure 5 A schematic diagram of one step of the method for preparing a gas sensor according to Example 1 of the present invention;

[0056] Figure 6 A schematic diagram of one step of the method for preparing a gas sensor according to Example 1 of the present invention;

[0057] Figure 7 A schematic diagram of one step of the method for preparing a gas sensor according to Example 1 of the present invention;

[0058] Figure 8 A schematic diagram of one step of the method for preparing a gas sensor according to Example 1 of the present invention;

[0059] Fig. 9 A schematic diagram of one step of the method for preparing a gas sensor according to Example 1 of the present invention;

[0060] Fig.10 A schematic diagram of one step of the method for preparing a gas sensor according to Example 1 of the present invention;

[0061] Fig.11 A schematic diagram of one step of the method for preparing a gas sensor according to Example 1 of the present invention;

[0062] Fig.12 A schematic diagram of one step of the method for preparing a gas sensor according to Example 1 of the present invention;

[0063] Fig.13 A schematic diagram of one step of the method for preparing a gas sensor according to Example 1 of the present invention;

[0064] Fig.14 A schematic diagram of one step of the method for preparing a gas sensor according to Example 1 of the present invention;

[0065] Fig.15 A schematic diagram of one step of the method for preparing a gas sensor according to Example 1 of the present invention;

[0066] Fig.16 A schematic diagram of one step of the method for preparing a gas sensor according to Example 1 of the present invention;

[0067] Fig.17 A schematic diagram of one step of the method for preparing a gas sensor according to Embodiment 2 of the present invention;

[0068] Fig.18 A schematic diagram of one step of the method for preparing a gas sensor according to Embodiment 2 of the present invention;

[0069] Fig.19 A schematic diagram of one step of the method for preparing a gas sensor according to Embodiment 2 of the present invention;

[0070] Fig. 20 A schematic diagram of one step of the method for preparing a gas sensor according to Embodiment 2 of the present invention;

[0071] Fig.21 This is a schematic diagram of one step of the method for preparing a gas sensor according to Embodiment 2 of the present invention.

[0072] Description of Reference Numerals

[0073] 100, device layer; 101, first substrate; 102, support layer; 103, heating layer; 104, electrode; 105, covering layer; 106, release groove; 107, release space; 200, cover layer; 201, second substrate; 202, first mask layer; 203, groove body; 204, oxide layer; 205, second mask layer; 301, measurement channel; 302, reference channel. DETAILED DESCRIPTION

[0074] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0075] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0076] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0077] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0078] In the description of the present invention, "several" means more than one, "many" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0079] In this article, "optionally", "optional", "optional" means optional, that is, it means to be selected from any of the two parallel solutions of "yes" or "no". If there are multiple "optional" in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" is independent. In this application, the descriptions such as "optionally contain" and "optionally include" mean "contain or not contain".

[0080] In this article, unless otherwise stated, each reaction step may be carried out in the order described herein or may not be carried out in the order described herein. For example, other steps may be included between each reaction step, and the order of the reaction steps may also be appropriately swapped. This can be determined by the technician based on common knowledge and experience. Preferably, the reaction method herein is carried out sequentially.

[0081] In the present application, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​in the numerical interval is considered to be continuous, and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to an integer in the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical range disclosed in the present application should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows for a broad range of quantitative intervals such as percentage intervals, ratio intervals, and ratio intervals.

[0082] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein 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. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0083] The present application provides a method for preparing a gas sensor to solve the problems of low packaging accuracy, complex packaging process, and large volume of the gas sensor in the prior art thermal conductivity gas sensor preparation method. The preparation method of the gas sensor will be described below in conjunction with the accompanying drawings.

[0084] The method for preparing the gas sensor provided in the embodiment of the present application is exemplary, please refer to Figure 1 As shown, Figure 1 The schematic diagram of the structure of the method for preparing the gas sensor provided in the embodiment of the present application is as follows: The method for preparing the gas sensor of the present application is small in size and has a simple packaging process.

[0085] In order to more clearly illustrate the structure of the method for preparing the gas sensor, the method for preparing the gas sensor will be introduced below with reference to the accompanying drawings.

[0086] For example, see Figure 1 As shown, a method for preparing a gas sensor comprises the following steps:

[0087] (1) Preparing the device layer 100: obtaining a first substrate 101.

[0088] A plurality of heating layers 103 and a plurality of electrodes 104 connected to the heating layers 103 are prepared on the first substrate 101 .

[0089] A covering layer 105 covering the heating layer 103 and the electrode 104 is prepared on the first substrate 101 .

[0090] A plurality of release grooves 106 are formed based on the cover layer 105 , wherein some of the release grooves 106 leak out of the electrode 104 , and some of the release grooves 106 extend to the first substrate 101 .

[0091] Furthermore, a plurality of independent release spaces 107 are formed by etching the first substrate 101 to a predetermined depth through part of the release grooves 106 , and each release space 107 is distributed correspondingly to a plurality of heating layers 103 .

[0092] (2) Obtaining a cover layer 200 including an oxide layer 204 .

[0093] (3) The side of the device layer 100 having the cap layer 105 is bonded to the side of the cover layer 200 having the oxide layer 204 .

[0094] (4) The cover layer 200 is grooved to obtain a measurement channel 301 . The measurement channel 301 extends to the partially released space 107 . A reference channel 302 is formed between the cover layer 200 and the partially released space 107 .

[0095] In some of the embodiments, the measuring channel 301 simultaneously extends to one of the release spaces 107 and contains a portion of the heating layer 103 , so that the measuring channel 301 leaks out of a portion of the heating layer 103 and the electrode 104 .

[0096] In some embodiments, in the present application, each heating layer 103 is connected to an electrode 104. There is a gap between adjacent electrodes 104, and there is a gap between adjacent heating layers 103.

[0097] In some embodiments, the plurality of electrodes 104 are distributed along a first direction of the first substrate 101, and the plurality of heating layers 103 are distributed along a second direction of the first substrate 101, wherein the first direction is different from the second direction. Preferably, the first direction is perpendicular to the second direction.

[0098] In some of the embodiments, the following steps are also included: after obtaining the first substrate 101 , preparing a support layer 102 on the first substrate 101 , preparing a heating layer 103 and an electrode 104 on the support layer 102 ; and preparing a covering layer 105 on the support layer 102 .

[0099] In some embodiments, the support layer 102 includes one or both of silicon oxide and silicon nitride.

[0100] In some of the embodiments, when preparing the support layer 102 on the first substrate 101, one or more of LPCVD (low pressure chemical vapor deposition), PECVD (plasma enhanced chemical vapor deposition) and TEOS (Tetraethyl Orthosilicate) processes are adopted.

[0101] In some embodiments, the thickness of the support layer 102 is 200 nm-2 μm.

[0102] In some embodiments, the first substrate 101 includes a silicon wafer.

[0103] In some embodiments, the thickness of the first substrate 101 is 1 mm to 10 mm. Preferably, the thickness of the first substrate 101 is 1 mm to 3 mm.

[0104] In some embodiments, the heating layer 103 is made of one or more materials selected from the group consisting of W, Pt, Au, and doped polysilicon.

[0105] In some embodiments, the heating layer 103 is in the shape of a thin strip. The length and width of the heating layer 103 can be set according to actual needs.

[0106] In some of the embodiments, the number of the heating layers 103 may be three, four, six, eight, etc. The number of the heating layers 103 may be set according to actual application scenarios.

[0107] In some embodiments, the electrode 104 is made of one or more materials selected from the group consisting of Pt, Au, and Al.

[0108] In some embodiments, the thickness of the heating layer 103 is 200 nm-2 μm.

[0109] In some embodiments, the thickness of the electrode 104 is 200 nm to 2 μm.

[0110] In some embodiments, the capping layer 105 includes one or both of silicon oxide and silicon nitride.

[0111] In some of the embodiments, when preparing the capping layer 105, one or more of LPCVD, PECVD and TEOS processes are adopted.

[0112] In some embodiments, the capping layer 105 has a thickness of 200 nm to 2 μm.

[0113] In some embodiments, the first substrate 101 is etched to a predetermined depth of 5 μm to 100 μm through the partial release groove 106 .

[0114] In some of the embodiments, when preparing a plurality of release grooves 106 based on the cover layer 105, a dry etching method or a wet etching method is used. For example, when preparing the release grooves 106, a dry etching method is used, which specifically includes the following processes: using an RIE etching method. During the RIE process, a gas is introduced into a vacuum chamber and ionized into a plasma state. By applying a radio frequency (RF) voltage, the positive ions in the plasma are accelerated and bombarded onto the substrate surface. These ions react chemically with the substrate material to form volatile products and are removed. At the same time, the kinetic energy of the ions also plays a role in physical sputtering, thereby achieving etching.

[0115] In some embodiments, obtaining the cover layer 200 including the oxide layer 204 includes the following steps:

[0116] A second substrate 201 is obtained.

[0117] A first mask layer 202 is prepared on the second substrate 201 .

[0118] The first mask layer 202 is patterned.

[0119] The second substrate 201 is grooved based on the patterned first mask layer 202 to obtain a plurality of groove bodies 203 corresponding to the release grooves 106. One of the groove bodies 203 and the corresponding release groove 106 form a reference channel 302.

[0120] And, an oxide layer 204 is prepared on the second substrate 201 after the groove processing.

[0121] In some embodiments, the thickness of the second substrate 201 is 1 mm to 10 mm. Preferably, the thickness of the second substrate 201 is 1 mm to 3 mm.

[0122] In some embodiments, the first mask layer 202 includes an oxide layer, a nitride layer, or a photoresist.

[0123] In some embodiments, when preparing the first mask layer 202, one or more of LPCVD, PECVD and TEOS processes are used.

[0124] In some embodiments, the thickness of the first mask layer 202 is 200 nm-2 μm.

[0125] In some embodiments, when preparing the cover layer 200, dry etching or wet etching can be used, wherein, when dry etching is used, a first mask layer 202 is prepared on one surface of the second substrate 201. When wet etching is used, first mask layers 202 are prepared on both surfaces of the second substrate 201.

[0126] Dry etching is a widely used technique in semiconductor manufacturing and other microfabrication fields for removing or patterning materials. Dry etching does not require liquid chemical reagents, but uses gas and plasma to remove materials. Dry etching can achieve finer and more controllable etching effects and can reduce environmental pollution. The main types of dry etching include: (1) Reactive ion etching (RIE): RIE is a process that generates plasma by introducing gas into a low-pressure chamber under the action of a radio frequency electric field. The active ions in the plasma are accelerated to collide with the surface to be etched, causing the material to be physically removed, and the chemical reaction that occurs at the same time also helps the etching process. (2) Deep reactive ion etching (DRIE): DRIE is a technology developed based on RIE and is particularly suitable for making structures with high aspect ratios, such as silicon through vias in MEMS devices. It can achieve vertical sidewalls and smooth bottoms by alternating etching and deposition steps. (3) Plasma Etching: This method relies mainly on free radicals in the plasma to etch the material, rather than relying on the momentum transfer of ions. Therefore, it is highly isotropic, that is, the etching rate is similar in all directions. (4) Ion Milling (IonMilling or Sputter Etching): Ion milling is a purely physical process in which a high-energy ion beam directly bombards the target surface, thereby peeling off material atoms layer by layer. This method is often used in applications that require very high precision. (5) Chemical Dry Etching (CDE): CDE involves the use of gaseous chemicals to react directly with the material to remove the material without relying on plasma. For example, hydrogen fluoride gas can be used to etch silicon dioxide.

[0127] Wet etching is a traditional material removal technology, mainly used in semiconductor manufacturing, microelectromechanical systems (MEMS), optoelectronic devices and other fields. Wet etching immerses the substrate to be processed in a specific chemical solution and uses chemical reactions to selectively dissolve and remove unwanted material layers to achieve patterning or other processing purposes. The main types of wet etching include: (1) Isotropic etching: In this type of etching process, the chemical reagents erode the material uniformly from all directions, resulting in the etched area presenting a circular or hemispherical contour. This is usually suitable for applications where the shape accuracy requirements are not particularly high. (2) Anisotropic etching: Unlike isotropic etching, anisotropic etching is direction-dependent, that is, there is a significant difference in etching rate on different crystal planes or directions. For example, certain alkaline solutions in silicon single crystals can achieve highly anisotropic etching effects, forming structures with upright sidewalls and flat bottoms.

[0128] For example, in some embodiments, when the cover layer 200 is prepared by wet etching, the following steps are included:

[0129] 1) Obtain a second substrate 201 .

[0130] 2) First mask layers 202 are prepared on two surfaces of the second substrate 201 respectively.

[0131] 3) Patterning one of the first mask layers 202 .

[0132] 4) Based on the patterned first mask layer 202, the second substrate 201 is grooved by wet etching.

[0133] 5) An oxide layer 204 is prepared on the second substrate 201 after the groove processing.

[0134] For example, in some embodiments, when the cover layer 200 is prepared by dry etching, the following steps are included:

[0135] 1) Obtain a second substrate 201 .

[0136] 2) Preparing a first mask layer 202 on one surface of the second substrate 201 .

[0137] 3) Patterning the first mask layer 202 .

[0138] 4) Based on the patterned first mask layer 202, the second substrate 201 is grooved by dry etching.

[0139] 5) An oxide layer 204 is prepared on the second substrate 201 after the groove processing.

[0140] In some embodiments, when patterning the first mask layer 202, one or both of laser etching and photolithography etching methods are used.

[0141] In some embodiments, when the second substrate 201 is grooved, the depth of the grooves is 5 μm-100 μm.

[0142] In some of the embodiments, when the second substrate 201 is grooved, dry etching or wet etching may be used.

[0143] In some of the embodiments, when preparing the oxide layer 204, one or more of LPCVD, PECVD and TEOS processes are used.

[0144] In some embodiments, the oxide layer 204 has a thickness of 1 μm to 5 μm.

[0145] In some of the embodiments, after bonding the device layer 100 and the cover layer 200 , a step of thinning the device layer 100 and the cover layer 200 is further included.

[0146] In some embodiments, the overall thickness of the device layer 100 and the cover layer 200 after thinning is 50 μm-200 μm.

[0147] In some embodiments, when the cover plate layer 200 is grooved to obtain the measuring channel 301, the following steps are included:

[0148] (1) A second mask layer 205 is prepared on the bonded cover layer 200 .

[0149] (2) Part of the second mask layer 205 and the cover layer 200 are grooved to obtain a measurement channel 301 , and the measurement channel 301 extends to the cover layer 105 .

[0150] In some embodiments, the second mask layer 205 includes an oxide layer, a nitride layer, or a photoresist.

[0151] In some of the embodiments, when preparing the second mask layer 205, one or more of LPCVD, PECVD and TEOS processes are used.

[0152] In some embodiments, the thickness of the second mask layer 205 is 200 nm-2 μm.

[0153] In some of the embodiments, when the cover plate layer 200 is grooved to obtain the measurement channel 301 , dry etching or wet etching may be used.

[0154] In some embodiments, when the cover plate layer 200 is grooved by wet etching to obtain the measurement channel 301, the following steps are included:

[0155] (1) A second mask layer 205 is formed on both sides of the bonded device layer 100 and the cover layer 200. The second mask layer 205 may be an oxide layer, a nitride layer or a photoresist.

[0156] (2) A portion of the second mask layer 205 on the cover layer 200 and the cover layer 200 at a corresponding position are wet-etched to form a groove to obtain a measurement channel 301, and the measurement channel 301 extends to the cover layer 105. The wet etching process can be one or more of LPCVD, PECVD, and TEOS.

[0157] In some embodiments, when the cover layer 200 is grooved by dry etching to obtain the measurement channel 301, the following steps are included:

[0158] (1) Forming the second mask layer 205 for the bonded cover layer 200. The second mask layer 205 may be an oxide layer, a nitride layer or a photoresist.

[0159] (2) Dry etching is performed on a portion of the second mask layer 205 on the cover layer 200 and the cover layer 200 at a corresponding position to form a measurement channel 301 , and the measurement channel 301 extends to the cover layer 105 .

[0160] In some embodiments, LPCVD is usually performed in a specially designed reaction chamber that can operate under low pressure conditions, typically in the range of 0.1 to 10 Torr. Low pressure conditions help reduce collisions between gas molecules, thereby improving the quality and purity of the film. Precursor gas: Specific gases are used as precursors, which react chemically with the substrate surface in the reaction chamber to form the desired solid material. For example, a common precursor in the polysilicon deposition process is silane (SiH 4 ). Heating system: The substrate needs to be heated to a certain temperature to promote the chemical reaction. This temperature depends on the material to be deposited and the type of precursor used. For some materials, additional catalysts or activation energy may be required to start the reaction. Deposition rate control: By adjusting reaction conditions such as temperature, pressure and gas flow, the deposition rate and the thickness of the final film can be precisely controlled.

[0161] In some of the embodiments, the main features and working principles of the PECVD process are as follows: Low-temperature deposition: Since the plasma provides additional energy, the precursor gas molecules can be decomposed and deposited into a solid film at a lower temperature. This not only reduces the impact of thermal stress on the substrate, but also allows the use of a wider variety of substrate materials. Plasma generation: Plasma is generated in the reaction chamber by applying radio frequency (RF), microwaves or other forms of electric fields. The high-energy electrons in the plasma can effectively activate the reaction gas and promote its chemical reaction. Selection of reaction gas: Select an appropriate reaction gas or gas mixture according to the material to be deposited. For example, in order to deposit silicon nitride (SiN x ), silane (SiH 4 ) and ammonia (NH 3 ) as the precursor gas; and the deposition of silicon oxide (SiO 2 ) may use silane and oxygen (O 2 ).

[0162] In some of the embodiments, the TEOS process is widely used due to its good film-forming properties, low thermal expansion coefficient and good compatibility with silicon substrates. It can be deposited at a relatively low temperature, reducing thermal damage to the substrate material and providing a uniform and dense silicon oxide film. TEOS process flow: a. Pretreatment: Clean the substrate to remove surface contaminants to ensure the quality of the subsequently deposited film. It also includes modifying the substrate surface, such as increasing hydrophilicity, so that the deposited material can be better attached. b. Deposition process: CVD mode. In traditional thermal CVD, TEOS and oxygen (O 2 ) is introduced into the heated reaction chamber and undergoes hydrolysis reaction under high temperature to form SiO 2 The typical deposition temperature range is about 300°C to 600°C. PECVD mode, using plasma-enhanced chemical vapor deposition (PECVD), can achieve efficient SiO at lower temperatures (about 200°C to 400°C). 2 Deposition. The plasma provides additional energy to promote the reaction, thereby reducing the required temperature. c. Post-treatment: After the deposition is completed, the formed SiO 2 The film is annealed to improve its density, reduce defects, and adjust its electrical properties.

[0163] Compared with other methods, the TEOS process can deposit high-quality SiO at a lower temperature. 2, which helps protect the temperature-sensitive substrate material. By precisely controlling the reaction conditions, very pure SiO2 films can be obtained, which is essential for high-performance electronic devices. The TEOS process can well cover complex three-dimensional structures, which is especially important for the fine patterns in modern integrated circuits.

[0164] An embodiment of the present application also provides a gas sensor.

[0165] A gas sensor is prepared by any one of the above preparation methods.

[0166] In some of the embodiments, a gas sensor includes a first substrate 101, a supporting layer 102, a plurality of heating layers 103, a plurality of electrodes 104, a covering layer 105, and a cover layer 200. A plurality of release grooves 106 are arranged on the first substrate 101. A supporting layer 102 is arranged on the first substrate 101. A plurality of heating layers 103 and a plurality of electrodes 104 are distributed on the supporting layer 102. A plurality of heating layers 103 correspond to each of the release grooves 106. The covering layer 105 covers the first substrate 101 and encapsulates one of the release grooves 106 to form a reference channel 302. The cover layer 200 has a measurement channel 301 corresponding to one of the release grooves 106, and the electrode 104 leaks out of the measurement channel 301.

[0167] In some of the embodiments, there are gaps between adjacent electrodes 104 and there are gaps between adjacent heating layers 103 .

[0168] In some of these embodiments, see Figure 7 As shown, the plurality of electrodes 104 are distributed along a first direction of the first substrate 101, and the plurality of heating layers 103 are distributed along a second direction of the first substrate 101, wherein the first direction is different from the second direction. Preferably, the first direction is perpendicular to the second direction.

[0169] In some embodiments, a protective layer may be provided on the surface of the gas sensor. Preferably, the inner wall of the groove body 203 and the inner wall of the release groove 106 may also be provided with a protective layer, which may be an oxide layer, a nitride layer, etc. The protective layer may be an oxide layer, a nitride layer, etc.

[0170] The measurement channel 301 and the reference channel 302 of the gas sensor of the present application are heated to the same temperature respectively, and the concentration of the measured gas molecules in the measured air is obtained according to the data difference between the measurement channel 301 and the reference channel 302.

[0171] Example 1

[0172] This embodiment provides a gas sensor.

[0173] The gas sensor of this embodiment is prepared by the following method.

[0174] Obtain a silicon wafer as the first substrate 101, see Figure 2 shown.

[0175] A 200 nm thick silicon oxide is prepared on the first substrate 101 by LPCVD process as a support layer 102. Figure 3 shown.

[0176] A plurality of heating layers 103 with a thickness of 200 nm are prepared on the support layer 102 using Au material, and a plurality of electrodes 104 with a thickness of 200 nm are prepared and connected one by one with the heating layers 103 using Au material, see Figure 4 shown.

[0177] Using LPCVD process, a 200 nm thick silicon oxide and silicon nitride covering the heating layer 103 and the electrode 104 are prepared on the support layer 102 as a covering layer 105, see Figure 5 shown.

[0178] A plurality of release grooves 106 are prepared by dry etching based on the cover layer 105, wherein some of the release grooves 106 leak out of the electrode 104, see Figure 6 As shown, part of the release groove 106 extends to the first substrate 101 to form a plurality of independent release spaces 107, and each release space 107 is distributed corresponding to a plurality of heating layers 103, wherein the top view of the first substrate 101 is shown in FIG. Figure 7 shown.

[0179] The first substrate 101 is etched to a depth of 5 μm through the partial release groove 106 by dry etching, see Figure 8 shown.

[0180] A second substrate 201 is obtained.

[0181] The oxide layer 204 with a thickness of 200 nm is prepared on one surface of the second substrate 201 by using the LPCVD process as the first mask layer 202. Fig. 9 shown.

[0182] The first mask layer 202 is patterned by laser etching, see Fig.10 shown.

[0183] Based on the patterned first mask layer 202, the second substrate 201 is grooved by dry etching, and the groove depth is 5 μm. Fig.11 shown.

[0184] The second substrate 201 after the groove processing is processed by LPCVD to prepare an oxide layer 204 with a thickness of 1 μm, see Fig.12 shown.

[0185] The side of the device layer 100 having the cap layer 105 is bonded to the side of the cover layer 200 having the oxide layer 204, see Fig.13 shown.

[0186] The device layer 100 and the cover layer 200 are thinned to a total thickness of 50 μm, see Fig.14 shown.

[0187] For the bonding cover layer 200, an oxide layer, a nitride layer or a photoresist is used as the second mask layer 205, see Fig.15 shown.

[0188] The measurement channel 301 is obtained by dry etching a portion of the second mask layer 205 on the cover layer 200 and the cover layer 200 at the corresponding position. The measurement channel 301 extends to one of the release spaces 107 and contains a portion of the heating layer 103, so that the measurement channel 301 leaks out a portion of the heating layer 103 and the electrode 104. A reference channel 302 is formed between the cover layer 200 and the portion of the release space 107, and a portion of the heating layer 103 between the cover layer 200 and the release groove 106 forms a reference channel 302. Fig.15 shown.

[0189] Example 2

[0190] This embodiment provides a gas sensor.

[0191] The gas sensor of this embodiment is prepared by the following method.

[0192] Obtain a silicon wafer as the first substrate 101, see Figure 2 shown.

[0193] A PECVD process is used to prepare a 2 μm thick silicon oxide as a support layer 102 on the first substrate 101. Figure 3 shown.

[0194] A plurality of heating layers 103 with a thickness of 2 μm are prepared on the support layer 102 using W-doped polysilicon material, and a plurality of electrodes 104 with a thickness of 2 μm connected to the heating layers 103 are prepared using Au material. Figure 4 shown.

[0195] Using the PECVD process, a silicon oxide or silicon nitride layer with a thickness of 2 μm is prepared on the support layer 102 to cover the heating layer 103 and the electrode 104 as a covering layer 105, see Figure 5 shown.

[0196] A plurality of release grooves 106 are prepared by wet etching based on the cover layer 105, wherein some of the release grooves 106 leak out of the electrode 104, see Figure 6As shown, part of the release groove 106 extends to the first substrate 101 to form a plurality of independent release spaces 107, and each release space 107 is distributed corresponding to a plurality of heating layers 103, wherein the top view of the first substrate 101 is shown in FIG. Figure 7 shown.

[0197] The first substrate 101 is etched to a depth of 100 μm through the partial release groove 106 by wet etching, see Figure 8 shown.

[0198] A second substrate 201 is obtained.

[0199] The PECVD process is used to prepare an oxide layer 204 with a thickness of 2 μm on both surfaces of the second substrate 201 as the first mask layer 202. Fig.17 shown.

[0200] A first mask layer 202 is patterned by photolithography and etching. Fig.18 shown.

[0201] Based on the patterned first mask layer 202, the second substrate 201 is grooved by wet etching, and the groove depth is 10 μm. Fig.19 shown.

[0202] The second substrate 201 after the groove treatment is processed by PECVD process to prepare an oxide layer 204 with a thickness of 5 μm, see Fig.12 shown.

[0203] The side of the device layer 100 having the cap layer 105 is bonded to the side of the cover layer 200 having the oxide layer 204, see Fig.13 shown.

[0204] The device layer 100 and the cover layer 200 are thinned to a total thickness of 200 μm, see Fig.14 shown.

[0205] The oxide layer, nitride layer or photoresist is respectively formed on both sides of the bonded device layer 100 and the cover layer 200 as the second mask layer 205, see Fig. 20 shown.

[0206] The measurement channel 301 is obtained by wet etching a part of the second mask layer 205 on the cover layer 200 and the cover layer 200 at the corresponding position. The measurement channel 301 extends to one of the release spaces 107 and contains a part of the heating layer 103, so that the measurement channel 301 leaks part of the heating layer 103 and the electrode 104. A reference channel 302 is formed between the cover layer 200 and the part of the release space 107, and a part of the heating layer 103 between the cover layer 200 and the release groove 106 forms a reference channel 302. Fig.21 shown.

[0207] In summary, the preparation method of the above-mentioned gas sensor realizes wafer-level packaging of the device layer 100 and the cover layer 200 through bonding, and the packaging process is sophisticated. During the preparation process, the reference channel 302 is directly packaged through the cover layer 200, and the measurement channel 301 is obtained by grooving part of the second mask layer 205 and the cover layer 200. Such a processing technology can reduce the volume of the gas sensor, reduce the packaging complexity, and reduce the preparation cost.

[0208] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0209] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0210] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a gas sensor, characterized in that: The steps include: Prepare the device layer: obtain a first substrate; prepare a plurality of heating layers and a plurality of electrodes respectively connected to the heating layers on the first substrate; prepare a covering layer covering the heating layers and the electrodes on the first substrate; A plurality of release grooves are prepared based on the cover layer, wherein some of the release grooves leak out of the electrode and some of the release grooves extend to the first substrate; a plurality of independent release spaces are formed by etching the first substrate to a predetermined depth through some of the release grooves, and each of the release spaces corresponds to a plurality of the heating layers; obtaining a cover layer including an oxide layer; Bonding a side of the device layer having the cover layer to a side of the cover plate layer having the oxide layer; Furthermore, the cover plate layer is grooved to obtain a measurement channel, the measurement channel extends to a portion of the release space, and a reference channel is formed between the cover plate layer and a portion of the release space.

2. The method for preparing a gas sensor according to claim 1, characterized in that: The method further includes the following steps: after obtaining a first substrate, preparing a support layer on the first substrate, preparing the heating layer and the electrode on the support layer; and preparing the covering layer on the support layer.

3. The method for preparing a gas sensor according to claim 2, characterized in that: The support layer includes one or both of silicon oxide and silicon nitride; and / or, when preparing the support layer on the first substrate, one or more of LPCVD, PECVD and TEOS processes are used; And / or, the thickness of the support layer is 200 nm to 2 μm.

4. The method for preparing a gas sensor according to claim 1, characterized in that: The first substrate comprises a silicon wafer; And / or, the heating layer is made of one or more materials selected from the group consisting of W, Pt, Au, and doped polysilicon; And / or, the electrode is made of one or more materials selected from the group consisting of Pt, Au, and Al; And / or, the thickness of the heating layer is 200nm~2μm; And / or, the thickness of the electrode is 200 nm~2 μm.

5. The method for preparing a gas sensor according to claim 1, characterized in that: The covering layer includes one or both of silicon oxide and silicon nitride; and / or, when preparing the cover layer, one or more of LPCVD, PECVD and TEOS processes are used; And / or, the thickness of the covering layer is 200nm~2μm; And / or, the first substrate is etched through part of the release groove to a predetermined depth of 5 μm to 100 μm.

6. The method for preparing a gas sensor according to any one of claims 1 to 5, characterized in that: When obtaining the cover layer containing the oxide layer, the following steps are included: obtaining a second substrate; preparing a first mask layer on the second substrate; Patterning the first mask layer; Performing a groove process on the second substrate based on the patterned first mask layer to obtain a plurality of groove bodies respectively corresponding to the release grooves; And, an oxide layer is prepared on the second substrate after the groove processing.

7. The method for preparing a gas sensor according to claim 6, characterized in that: The first mask layer includes an oxide layer, a nitride layer or a photoresist; and / or, when preparing the first mask layer, one or more of LPCVD, PECVD and TEOS processes are used; And / or, the thickness of the first mask layer is 200 nm-2 μm.

8. The method for preparing a gas sensor according to claim 6, characterized in that: When patterning the first mask layer, one or both of laser etching and photolithography etching methods are used; And / or, when the second substrate is grooved, the depth of the groove is 5 μm to 100 μm; and / or, when preparing the oxide layer, one or more of LPCVD, PECVD and TEOS processes are used; And / or, the thickness of the oxide layer is 1 μm to 5 μm.

9. The method for preparing a gas sensor according to any one of claims 1 to 5, 7 to 8, characterized in that: After bonding the device layer to the cover layer, the step of thinning the device layer and the cover layer is also included; And / or, the overall thickness of the device layer and the cover layer after thinning is 50 μm to 200 μm; And / or, when the cover plate layer is grooved to obtain the measurement channel, the following steps are included: preparing a second mask layer on the bonded cover plate layer; Part of the second mask layer and the cover plate layer is grooved to obtain the measurement channel, and the measurement channel extends to the cover layer.

10. A gas sensor, characterized in that: The gas sensor is prepared by the preparation method described in any one of claims 1 to 9, comprising a first substrate, a support layer, a plurality of heating layers, a plurality of electrodes, a covering layer, and a cover plate layer, wherein a plurality of release grooves are arranged on the first substrate, a support layer is arranged on the first substrate, a plurality of the heating layers and a plurality of the electrodes are distributed on the support layer, and a plurality of the heating layers correspond to each of the release grooves, the covering layer covers the first substrate and encapsulates one of the release grooves to form a reference channel, the cover plate layer has a measurement channel corresponding to one of the release grooves, and the electrode leaks out of the measurement channel.

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