Micro-hotplate of leadless glass substrate and method of making same

Abstract

The present disclosure provides a leadless glass substrate micro-hotplate and a preparation method thereof. The micro-hotplate comprises: a glass substrate, which has a glass film structure on the front surface of the glass substrate, two through-hole structures respectively arranged on both sides of the glass film structure, and a conductive silicon column arranged in each through-hole structure; a heat insulation groove arranged on the back surface of the glass substrate opposite to the glass film structure, and an ohmic contact metal electrode arranged at the bottom end of the conductive silicon column on the back surface of the glass substrate; a heating electrode and a detection electrode formed on the glass film structure; and an insulation structure formed between the heating electrode and the detection electrode on the glass film structure. The micro-hotplate is prepared by using the glass substrate, which has a lower thermal conductivity than the silicon substrate and is integrally formed by using a hot reflow process to soften and melt the glass wafer at high temperature. The micro-hotplate prepared by using the glass substrate can effectively reduce the heat loss of the micro-hotplate and improve the structural stability of the micro-hotplate.

Description

Technical Field

[0001] This disclosure relates to the field of micro-electro-mechanical systems (MEMS) technology, and in particular to a leadless glass substrate micro-hot plate and its fabrication method. Background Technology

[0002] Gas sensors, as an important type of sensor, come in a variety of forms, including semiconductor, electrochemical, catalytic combustion, solid electrolyte, and optical types. Among them, semiconductor metal oxide gas sensors, since their introduction in 1962, have become the most widely used type of gas sensor due to their advantages such as high sensitivity, rapid response, and low cost. However, they still suffer from problems such as high power consumption, large size, and difficulty in integration with circuits. The application of MEMS technology can effectively solve these problems, and the advancement of micro-hot plates, as one of the core components of MEMS gas sensors, is driving the further development of gas sensors towards low power consumption, small size, and high integration.

[0003] Currently, most commercially available MEMS gas sensors use silicon substrates for their micro-hotplates, integrating heaters and detection electrodes on the silicon substrate. Because silicon substrates have high thermal conductivity, they are prone to heat loss. To reduce power consumption, silicon-based micro-hotplates require etching away the supporting silicon at the bottom of the heaters and detection electrodes, forming a suspended thin-film structure. This type of structure relies solely on a suspended beam structure or the thin-film itself for support, resulting in relatively low structural strength. Furthermore, since micro-hotplates typically operate at high temperatures, this type of structure is prone to deformation, thus weakening the structural stability of the micro-hotplate. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] In view of this, the main objective of this disclosure is to provide a leadless glass substrate micro-hot plate and its preparation method, so as to reduce the heat loss of the micro-hot plate and improve the structural stability of the micro-hot plate.

[0006] (II) Technical Solution

[0007] According to one aspect of this disclosure, a leadless glass substrate micro-hotplate is provided for use in a gas sensor, the micro-hotplate comprising:

[0008] A glass substrate has a glass thin film structure on its front side, two through-hole structures on each side of the glass thin film structure, and a conductive silicon pillar in each through-hole structure; a heat insulation groove is provided on the back side of the glass substrate opposite to the glass thin film structure, and an ohmic contact metal electrode is provided at the bottom end of the conductive silicon pillar on the back side of the glass substrate.

[0009] A heating electrode and a detection electrode are formed on the glass thin film structure; and

[0010] An insulating structure is formed between the heating electrode and the detection electrode on the glass thin film structure.

[0011] In some embodiments, the glass film structure is a cube or cylinder structure, which is directly connected to the surrounding glass edge structure and integrally formed, or is supported by four suspended beam structures connected to the surrounding glass edge structure.

[0012] In some embodiments, the heating electrode, the insulating structure, and the detection electrode are sequentially formed on the glass film structure in a layered structure. First, the heating electrode is formed on the glass film structure, then the insulating structure is formed on the heating electrode and the glass film structure, and finally the detection electrode is formed on the insulating structure.

[0013] In some embodiments, the heating electrode, the insulating structure, and the detection electrode are formed on the glass film structure in a co-layer structure. First, the heating electrode and the detection electrode are formed simultaneously on the glass film structure by depositing an electrode layer, with the detection electrode inside and the heating electrode outside, forming an enclosed shape. Then, an insulating structure is formed between the metal strips forming the heating electrode and the detection electrode and on the glass film structure.

[0014] In some embodiments, the detection electrode employs an interdigitated structure.

[0015] In some embodiments, the insulating structure is made of SiO2, or a composite material layer formed by stacking a Si3N4 layer on a SiO2 layer.

[0016] According to another aspect of this disclosure, a method for preparing a leadless glass substrate micro-hot plate is provided, the method comprising:

[0017] The front side of the silicon wafer is etched to form silicon grooves and conductive silicon pillars;

[0018] The glass wafer is anodicly bonded to the front side of the etched silicon wafer, and a hot reflow process is used to soften and melt the glass wafer at high temperature, and then reflow it into the silicon structure of the etched silicon wafer to form a bulk glass.

[0019] The upper surface of the bulk glass is planarized until the upper surface of the conductive silicon pillars is exposed, forming a glass thin film structure and a glass edge structure.

[0020] The back side of the silicon wafer is thinned until the lower surface of the conductive silicon pillar is exposed;

[0021] A heating electrode, an insulating structure, and a detection electrode are formed on a glass thin film structure;

[0022] An ohmic contact metal is formed on the lower surface of the conductive silicon pillars exposed on the back side of the silicon wafer; and

[0023] The silicon wafer under the glass film structure is etched from the back side of the silicon wafer until the glass film structure is suspended, forming a heat insulation groove below the glass film structure.

[0024] In some embodiments, etching the front side of the silicon wafer to form silicon grooves and conductive silicon pillars includes: using double-surface polishing, crystal orientation... <100> A single-crystal silicon wafer with a resistivity ≤0.001Ω·cm is used as the silicon wafer; using photoresist or SiO2 as a mask, the front side of the silicon wafer is etched using photolithography and deep reactive ion etching processes to form silicon grooves; the front side of the silicon wafer is etched on the outside of the silicon grooves using photolithography and deep reactive ion etching processes to form conductive silicon pillars.

[0025] In some embodiments, the step of anodicly bonding the glass wafer to the front side of the etched silicon wafer and using a hot reflow process to soften and melt the glass wafer at high temperature and reflow it into the etched silicon structure of the silicon wafer to form a block glass includes: selecting BF33 high borosilicate glass as the glass wafer, anodicly bonding the glass wafer to the front side of the etched silicon wafer, using an anodic bonding voltage of 800V to 1000V, a temperature of 450℃, and a bonding time of 30 minutes; and performing hot reflow on the anodicly bonded glass wafer and silicon wafer in a high-temperature tube furnace, whereby the glass wafer softens and melts at high temperature and reflows into the etched silicon structure of the silicon wafer to form a block glass, using a hot reflow temperature of 750℃ to 900℃.

[0026] In some embodiments, the planarization of the upper surface of the bulk glass and the thinning of the back side of the silicon wafer are both accomplished using a chemical mechanical polishing method.

[0027] In some embodiments, forming a heating electrode, an insulating structure, and a detection electrode on a glass thin film structure includes: forming a heating electrode on the glass thin film structure; forming an insulating structure on the heating electrode and the glass thin film structure; and forming a detection electrode on the insulating structure.

[0028] In some embodiments, forming a heating electrode, an insulating structure, and a detection electrode on a glass thin film structure includes: simultaneously forming a heating electrode and a detection electrode on the glass thin film structure by depositing an electrode layer, wherein the detection electrode is inside and the heating electrode is outside, forming an enclosing shape; and forming an insulating structure between the metal strips forming the heating electrode and the detection electrode and on the glass thin film structure.

[0029] In some embodiments, forming an ohmic contact metal on the lower surface of the conductive silicon pillar exposed on the back side of the silicon wafer includes: forming an ohmic contact metal on the lower surface of the conductive silicon pillar exposed on the back side of the silicon wafer using photolithography etching or a stripping method, wherein the ohmic contact metal is made of metal Al and has a thickness of 0.3 μm to 1 μm.

[0030] In some embodiments, etching the silicon wafer under the glass thin film structure from the back of the silicon wafer until the glass thin film structure is suspended, and forming a heat insulation groove below the glass thin film structure, includes: using deep reactive ion etching technology to etch the silicon wafer directly below the glass thin film structure from the back of the silicon wafer until the glass thin film structure is suspended, forming a heat insulation groove below the glass thin film structure, thus completing the fabrication of the entire micro-hot plate;

[0031] The heat insulation groove is a cavity formed by etching the silicon wafer directly below the glass thin film structure after the glass wafer has undergone thermal reflow.

[0032] In some embodiments, after the fabrication of the entire hot plate is completed, the method further includes: performing leadless packaging of the hot plate and the integrated circuit using solder joints.

[0033] According to another aspect of this disclosure, a gas sensor is also provided, which is fabricated using the aforementioned leadless glass substrate micro-hot plate, or using the micro-hot plate fabricated by the method described.

[0034] (III) Beneficial Effects

[0035] As can be seen from the above technical solutions, the leadless glass substrate micro-hot plate and its preparation method provided in this disclosure have at least the following beneficial effects:

[0036] 1. The leadless glass substrate micro hot plate and its preparation method provided in this disclosure utilize the characteristic that the thermal conductivity of the glass substrate is lower than that of the silicon substrate to prepare the micro hot plate, which can effectively reduce the heat loss of the micro hot plate and improve the energy utilization rate.

[0037] 2. The leadless glass substrate micro-hot plate and its preparation method provided in this disclosure are integrally formed by softening and melting a glass wafer at high temperature and reflowing it into the silicon structure of an etched silicon wafer using a hot reflow process. This provides good support for the heating electrode, insulation structure, and detection electrode. Furthermore, the glass substrate fabrication technology does not require etching or corroding of the glass, and the glass substrate has high forming quality, which can effectively improve the structural stability of the micro-hot plate. In addition, the glass substrate is easy to process and form, which effectively reduces the processing difficulty. This is an effective way to realize the glass-based micro-hot plate process.

[0038] 3. The leadless glass substrate micro hot plate and its preparation method provided in this disclosure adopt glass-silicon anode bonding and glass hot reflow process to realize the synchronous forming of conductive silicon pillars and micro hot plate. The metal electrodes of micro hot plate are packaged and connected to integrated circuit by solder joints. Compared with gold wire bonding, the device's ability to resist mechanical and thermal shock is greatly improved, thereby increasing the structural stability and performance reliability of the device.

[0039] 4. The leadless glass substrate micro hot plate and its preparation method provided in this disclosure adopt a leadless glass substrate, which reduces the structural size of the micro hot plate and the packaged device, and facilitates the further development of the device towards low power consumption, small size and high integration. Attached Figure Description

[0040] The above and other objects, features, and advantages of this disclosure will become clearer from the following description of embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0041] Figure 1 This is a cross-sectional view of a leadless glass substrate micro-hot plate according to an embodiment of the present disclosure.

[0042] Figure 2 This is a flowchart of a method for preparing a leadless glass substrate micro-hotplate according to an embodiment of the present disclosure.

[0043] Figure 3 This is a cross-sectional view of a silicon groove 101 etched on the front side of a silicon wafer in accordance with an embodiment of the present disclosure.

[0044] Figure 4 This is a cross-sectional view of a conductive silicon pillar 102 etched on the front side of a silicon wafer in accordance with an embodiment of the present disclosure.

[0045] Figure 4A and Figure 4B This is a top view of the conductive silicon pillar 102 etched on the front side of a silicon wafer according to an embodiment of the present disclosure.

[0046] Figure 5 This is a cross-sectional view of anodizing the glass wafer 200 and the front side of the etched silicon wafer 100 according to an embodiment of the present disclosure.

[0047] Figure 6 This is a cross-sectional view of a glass hot reflow process according to an embodiment of the present disclosure.

[0048] Figure 7 This is a cross-sectional view of the planarization of the upper surface of the block glass 201 after the glass hot reflow process according to an embodiment of the present disclosure.

[0049] Figure 8 This is a cross-sectional view of the back side of a silicon wafer 100 being thinned according to an embodiment of the present disclosure.

[0050] Figure 9 This is a cross-sectional view of a heating electrode 301 fabricated on a glass thin film structure according to an embodiment of the present disclosure.

[0051] Figure 9A This is a top view of a heating electrode 301 fabricated on a glass thin film structure according to an embodiment of the present disclosure.

[0052] Figure 10 This is a cross-sectional view of an insulating structure 401 fabricated on a heating electrode 301 in accordance with an embodiment of the present disclosure.

[0053] Figure 11 This is a cross-sectional view of a detection electrode 501 fabricated on an insulating structure 401 according to an embodiment of the present disclosure.

[0054] Figure 11A This is a top view of a detection electrode 501 fabricated on an insulating structure 401 according to an embodiment of the present disclosure.

[0055] Figure 12 A cross-sectional view of an ohmic contact metal 601 formed on the lower surface of a conductive silicon pillar 102 exposed on the back side of a silicon wafer 100 in accordance with an embodiment of the present disclosure.

[0056] Figure 13 This is a cross-sectional view of a heat insulation groove 701 formed under a glass film structure according to an embodiment of the present disclosure.

[0057] Figure 14 This is a cross-sectional view of a leadless package of a micro hotplate and integrated circuit 802 according to an embodiment of the present disclosure.

[0058] [Explanation of Labels in the Attached Image]

[0059] 100 - Silicon wafer; 101 - Silicon trench; 102 - Conductive silicon pillar;

[0060] 200 - Glass wafer; 201 - Bulk glass after reflow; 202 - Glass thin film structure; 203 - Glass edge structure;

[0061] 301 - Heating electrode;

[0062] 401 - Insulation structure;

[0063] 501 - Detection electrode;

[0064] 601 - Ohmic contact metal;

[0065] 701 - Insulation Groove;

[0066] 801 - Solder joint; 802 - Integrated circuit. Detailed Implementation

[0067] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0068] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0069] Furthermore, the shapes and dimensions of the components in the figures do not reflect actual size and proportion, but are merely illustrative of embodiments of this disclosure. Additionally, any reference numerals placed between parentheses in the claims should not be construed as limiting the scope of the claims.

[0070] Furthermore, the words "comprising" or "including" do not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

[0071] To reduce heat loss and improve the structural stability of micro-hotplates in MEMS gas sensors, some research has utilized the low thermal conductivity and high structural strength of glass to design and optimize thin-film structures on glass substrates to fabricate micro-hotplates. However, high-quality fabrication of glass substrates remains challenging. Furthermore, current MEMS gas sensors often employ wire bonding for interconnection and packaging with circuitry, leaving room for improvement in integration levels.

[0072] According to embodiments of this disclosure, a leadless glass substrate micro-hot plate is provided for use in gas sensors, such as... Figure 1 As shown, Figure 1 This is a cross-sectional view of a leadless glass substrate micro-hotplate according to an embodiment of the present disclosure, the micro-hotplate comprising:

[0073] A glass substrate has a glass thin film structure 202 on its front side, two through-hole structures on both sides of the glass thin film structure 202, and a conductive silicon pillar 102 in each through-hole structure; a heat insulation groove 701 is provided on the back side of the glass substrate opposite to the glass thin film structure 202, and an ohmic contact metal electrode 601 is provided at the bottom end of the conductive silicon pillar 102 on the back side of the glass substrate.

[0074] A heating electrode 301 and a detection electrode 501 are formed on the glass thin film structure 202; and

[0075] An insulating structure 401 is formed between the heating electrode 301 and the detection electrode 501 on the glass thin film structure 202.

[0076] According to embodiments of this disclosure, the glass substrate is formed by hot reflowing a glass wafer into silicon grooves etched on a silicon wafer. The glass thin film structure 202 and the through-hole structure are formed by two etching processes to create silicon grooves of different depths on the silicon wafer, followed by hot reflowing. The glass substrate can be made of BF33 high borosilicate glass or other glass materials, which have characteristics such as low thermal conductivity, insulation, and high structural strength. The glass substrate is integrally formed by hot reflowing a glass wafer through high-temperature softening and melting into the etched silicon structure of the silicon wafer. This provides good support for the heating electrodes, insulating structures, and detection electrodes. Furthermore, the glass substrate fabrication technology does not require etching or corroding of the glass, resulting in high-quality glass substrate formation. This effectively improves the stability of the micro-hotplate structure and meets the substrate strength requirements of MEMS processes and devices. The glass substrate has poor thermal conductivity with the environment, thereby reducing device power consumption and heat loss. The glass substrate is compatible with standard MEMS processes that pattern metal electrodes.

[0077] According to the embodiments of this disclosure, the glass film structure 202 is a cube or cylinder structure, which is directly connected to the surrounding glass edge structure 203 and integrally formed, or is supported and connected to the surrounding glass edge structure 203 by four suspended beam structures.

[0078] According to an embodiment of this disclosure, the heating electrode 301, the insulating structure 401, and the detection electrode 501 can be formed sequentially on the glass film structure 202 in a layered structure. That is, the heating electrode 301 is first formed on the glass film structure 202, then the insulating structure 401 is formed on the heating electrode 301 and the glass film structure 202, and then the detection electrode 501 is formed on the insulating structure 401.

[0079] According to an embodiment of this disclosure, the heating electrode 301, the insulating structure 401, and the detection electrode 501 can be formed on the glass thin film structure 202 in a co-layer structure. That is, the heating electrode 301 and the detection electrode 501 are first formed on the glass thin film structure 202 by depositing an electrode layer, with the detection electrode 501 inside and the heating electrode 301 outside, forming an enclosed shape; then the insulating structure 401 is formed between the metal strips forming the heating electrode 301 and the detection electrode 501 and on the glass thin film structure 202.

[0080] According to the embodiments of this disclosure, when fabricating the heating electrode 301, the insulating structure 401, and the detection electrode 501, using a monolayer structure can simplify the manufacturing process and save costs compared to using a layered structure.

[0081] According to an embodiment of this disclosure, the detection electrode 501 adopts an interdigitated structure. Both the heating electrode 301 and the detection electrode 501 are made of metallic materials, and a thin metal film with a thickness of 100 nm to 500 nm is formed by electron beam evaporation or sputtering. Different metallic materials are used according to the operating temperature requirements of the micro-hotplate, and suitable adhesion materials are selected based on the material properties. The interconnection region between the heating electrode 301 or the detection electrode 501 and the conductive silicon pillar 102 is made of ohmic contact metal. The heating electrode 301, the detection electrode 501, and the ohmic contact metal are fabricated using photolithography etching or lift-off methods.

[0082] According to embodiments of this disclosure, the insulating structure 401 is made of SiO2, which also serves as a heat insulation layer, and has a thickness of 0.3 μm to 1 μm. The insulating structure 401 is fabricated using chemical vapor deposition or sputtering. Alternatively, the insulating structure 401 can be a composite material layer formed by further stacking a Si3N4 layer on top of the SiO2 layer.

[0083] based on Figure 1 The diagram shown is a cross-sectional view of a leadless glass substrate micro-hot plate according to an embodiment of the present disclosure. Figure 2 A flowchart illustrating a method for fabricating a leadless glass substrate micro-hotplate according to an embodiment of the present disclosure is shown. The leadless glass substrate micro-hotplate uses a silicon wafer as a mold, in which a silicon structure is etched out, and glass is filled into the silicon structure using a thermal reflow process to form a glass substrate. The specific steps include:

[0084] Step S1: Etch the front side of the silicon wafer 100 to form silicon grooves 101 and conductive silicon pillars 102.

[0085] In this step, double-surface polishing is selected, crystal orientation... <100> A single-crystal silicon wafer with a resistivity ≤0.001Ω·cm is used as the silicon wafer 100. Using photoresist or SiO2 as a mask, the front side of the silicon wafer is etched using photolithography and deep reactive ion etching processes to form a silicon groove 101. The front side of the silicon wafer is etched on the outside of the silicon groove 101 using photolithography and deep reactive ion etching processes to form a conductive silicon pillar 102.

[0086] like Figure 3 As shown, Figure 3This is a cross-sectional view of the silicon groove 101 etched on the front side of a silicon wafer according to an embodiment of the present disclosure. The silicon wafer 100 may be made of single-crystal silicon with double-surface polishing and crystal orientation... <100> A silicon wafer with a resistivity ≤0.001Ω·cm and a thickness of 400μm is used. A silicon groove 101 is etched on the upper surface of the silicon wafer 100 using photoresist or SiO2 as a mask and photolithography and deep reactive ion etching processes, with an etching depth of 5μm to 100μm.

[0087] In this step, such as Figure 4 and Figure 4A As shown, Figure 4 This is a cross-sectional view of the conductive silicon pillar 102 etched on the front side of a silicon wafer according to an embodiment of the present disclosure. Figure 4A and Figure 4B This is a top view of the conductive silicon pillars 102 etched on the front side of a silicon wafer according to an embodiment of the present disclosure. Two groove structures are etched on each side of the silicon groove 101 etched on the silicon wafer 100 using photolithography and deep reactive ion etching processes, with an etching depth of 300 μm to 350 μm, forming four conductive silicon pillars 102.

[0088] According to embodiments of this disclosure, the glass film structure 202 is a cube or cylinder structure, directly connected to the surrounding glass edge structures 203 in an integrated form, or supported by four suspended beam structures connected to the surrounding glass edge structures 203. Figure 4A This indicates that the glass film structure 202 is directly connected to the surrounding glass edge structure 203 and integrally formed. Figure 4B The glass film structure 202 is supported by four suspended beam structures and connected to the glass edge structure 203 around the perimeter.

[0089] Step S2: The glass wafer 200 is anodicly bonded to the front side of the etched silicon wafer 100, and the glass wafer 200 is softened and melted at high temperature using a hot reflow process and reflowed into the silicon structure of the etched silicon wafer 100 to form a block glass 201.

[0090] In this step, such as Figure 5 As shown, Figure 5 This is a cross-sectional view of anodizing a glass wafer 200 to the front side of an etched silicon wafer 100 according to an embodiment of the present disclosure. The glass wafer 200 can be BF33 borosilicate glass. The anodizing voltage for anodizing the glass wafer to the front side of the etched silicon wafer can be 800V to 1000V, the temperature can be 450°C, and the bonding time is 30 minutes.

[0091] In this step, such as Figure 6 As shown, Figure 6This is a cross-sectional view of a glass reflow process according to an embodiment of the present disclosure. Anode-bonded glass wafer 200 and silicon wafer 100 are subjected to reflow in a high-temperature tube furnace. The glass wafer 200 is softened and melted at high temperature and reflowed into the etched silicon structure of the silicon wafer to form a bulk glass 201. The reflow temperature is 750°C to 900°C.

[0092] In this step, glass-silicon anode bonding and glass hot reflow process are used to achieve simultaneous forming of conductive silicon pillars and micro hot plates, simplifying the manufacturing process.

[0093] Step S3: Planarize the upper surface of the block glass 201 until the upper surface of the conductive silicon pillar 102 is exposed, forming a glass thin film structure 202 and a glass edge structure 203.

[0094] In this step, such as Figure 7 As shown, Figure 7 This is a cross-sectional view of the planarization of the upper surface of the bulk glass 201 after the glass hot reflow process according to an embodiment of this disclosure. The planarization is performed using a chemical mechanical polishing method until the conductive silicon pillars 102 are exposed on the upper surface.

[0095] According to the embodiments of this disclosure, the glass film structure 202 is a cube or cylinder structure, which is directly connected to the surrounding glass edge structure 203 and integrally formed, or is supported and connected to the surrounding glass edge structure 203 by four suspended beam structures.

[0096] Please refer to Figure 4A and Figure 4B , Figure 4A This indicates that the glass film structure 202 is directly connected to the surrounding glass edge structure 203 and integrally formed. Figure 4B The glass film structure 202 is supported by four suspended beam structures and connected to the glass edge structure 203 around the perimeter.

[0097] Step S4: Thin the back side of silicon wafer 100 until the lower surface of the conductive silicon pillar is exposed.

[0098] In this step, such as Figure 8 As shown, Figure 8 This is a cross-sectional view of the back side of a silicon wafer 100 being thinned according to an embodiment of the present disclosure. The thinning is performed using a chemical mechanical polishing method until the conductive silicon pillars 102 are exposed on the lower surface.

[0099] Thus, the fabrication of the glass substrate is completed through steps S1 to S4. In this embodiment, the glass substrate is formed by hot reflowing a glass wafer into silicon grooves etched on a silicon wafer. The glass thin film structure 202 and the through-hole structure are formed by two etching processes to create silicon grooves of different depths on the silicon wafer, followed by hot reflowing. The glass substrate can be made of BF33 high borosilicate glass or other glass materials, which have characteristics such as low thermal conductivity, insulation, and high structural strength. The glass substrate is integrally formed by hot reflowing a glass wafer through high-temperature softening and melting into the etched silicon structure of the silicon wafer. This provides good support for the heating electrodes, insulating structures, and detection electrodes. Furthermore, the glass substrate fabrication technology does not require etching or corroding of the glass, resulting in high-quality glass substrate formation. This effectively improves the stability of the micro-hot plate structure and meets the substrate strength requirements of MEMS processes and devices. The glass substrate has poor thermal conductivity with the environment, thereby reducing device power consumption, minimizing heat loss, and improving energy utilization. The glass substrate is compatible with standard MEMS processes that pattern metal electrodes.

[0100] Step S5: Form a heating electrode, an insulating structure, and a detection electrode 501 on the glass thin film structure;

[0101] In this step, such as Figures 9 to 11 As shown, the heating electrode 301, the insulating structure 401, and the detection electrode 501 can be formed sequentially on the glass film structure in a layered structure. That is, the heating electrode 301 is first formed on the glass film structure, then the insulating structure 401 is formed on the heating electrode 301 and the glass film structure, and then the detection electrode 501 is formed on the insulating structure 401.

[0102] like Figure 9 and Figure 9A As shown, Figure 9 This is a cross-sectional view of a heating electrode 301 fabricated on a glass thin film structure according to an embodiment of the present disclosure. Figure 9A This is a top view of the fabrication of a heating electrode 301 on a glass thin film structure according to an embodiment of the present disclosure. The heating electrode 301 is made of a metallic material and is formed into a thin metal film with a thickness of 100 nm to 500 nm by electron beam evaporation or sputtering. Different metallic materials are used for the heating electrode 301 according to the operating temperature requirements of the micro-hotplate, and suitable adhesion materials are selected based on the material properties. Ohmic contact metal is used for the interconnection region between the heating electrode 301 and the conductive silicon pillar 102. The heating electrode 301 and the ohmic contact metal are fabricated using photolithography etching or lift-off methods.

[0103] like Figure 10 As shown, Figure 10This is a cross-sectional view of an insulating structure 401 fabricated on a heating electrode 301 according to an embodiment of the present disclosure. The insulating structure 401 is made of SiO2 and also serves as heat insulation, with a thickness of 0.3 μm to 1 μm. The insulating structure 401 is fabricated by chemical vapor deposition or sputtering. The insulating structure 401 can also be a composite material layer formed by further stacking a Si3N4 layer on top of the SiO2 layer.

[0104] like Figure 11 and Figure 11A As shown, Figure 11 This is a cross-sectional view of the fabrication of the detection electrode 501 on the insulating structure 401 according to an embodiment of the present disclosure. Figure 11A This is a top view of the fabrication of a detection electrode 501 on an insulating structure 401 according to an embodiment of the present disclosure. The detection electrode 501 is made of a metallic material, and a thin metal film with a thickness of 100 nm to 500 nm is formed by electron beam evaporation or sputtering. A suitable adhesion material is selected based on the properties of the selected material, and an ohmic contact metal is used for the interconnection region between the detection electrode 501 and the conductive silicon pillar 102. The detection electrode 501 can be an interdigitated electrode, and its fabrication is completed by photolithography etching or lift-off methods.

[0105] Furthermore, the heating electrode 301, the insulating structure 401, and the detection electrode 501 can also be formed on the glass thin film structure in a co-layer structure. That is, the heating electrode 301 and the detection electrode 501 are first formed on the glass thin film structure by depositing an electrode layer, with the detection electrode inside and the heating electrode outside, forming an enclosed shape; then the insulating structure 401 is formed between the metal strips forming the heating electrode 301 and the detection electrode 501.

[0106] According to the embodiments of this disclosure, when fabricating the heating electrode 301, the insulating structure 401, and the detection electrode 501, using a monolayer structure can simplify the manufacturing process and save costs compared to using a layered structure.

[0107] Step S6: An ohmic contact metal 601 is formed on the lower surface of the conductive silicon pillar 102 exposed on the back side of the silicon wafer 100.

[0108] In this step, such as Figure 12 As shown, Figure 12 This is a cross-sectional view of an ohmic contact metal 601 formed on the lower surface of the conductive silicon pillar 102 exposed on the back side of a silicon wafer 100 according to an embodiment of the present disclosure. The ohmic contact metal 601 is formed on the lower surface of the conductive silicon pillar 102 exposed on the back side of the silicon wafer using photolithography etching or lift-off methods. The ohmic contact metal 601 is made of metal Al and has a thickness of 0.3 μm to 1 μm. It is fabricated by photolithography etching or lift-off methods.

[0109] Step S7: Etch the silicon wafer under the glass thin film structure from the back side of the silicon wafer until the glass thin film structure is suspended, forming a heat insulation groove 701 under the glass thin film structure.

[0110] In this step, such as Figure 13 As shown, Figure 13 This is a cross-sectional view of a heat insulation groove 701 formed beneath a glass thin film structure according to an embodiment of the present disclosure. Deep reactive ion etching (DRIE) is used to etch the silicon wafer directly beneath the glass thin film structure from the back side of the silicon wafer until the glass thin film structure 202 is suspended, forming the heat insulation groove 701 beneath the glass thin film structure 202, thus completing the fabrication of the entire micro-hotplate. The heat insulation groove is a cavity formed by etching the silicon wafer directly beneath the glass thin film structure after the glass wafer has undergone thermal reflow.

[0111] Furthermore, after completing the fabrication of the entire micro hot plate, this embodiment of the present disclosure also includes a leadless package of the micro hot plate and the integrated circuit 802, specifically as follows: Figure 14 As shown, Figure 14 This is a cross-sectional view of a leadless package of a micro hotplate and integrated circuit 802 according to an embodiment of this disclosure. The micro hotplate and integrated circuit are packaged using solder joints. Figure 14 In the attached drawing, 801 is the solder joint.

[0112] In this embodiment of the disclosure, the metal electrodes of the micro hot plate are packaged and connected to the integrated circuit by solder joints. Compared with the gold wire bonding method, the device's ability to resist mechanical and thermal shock is greatly improved, thereby increasing the device's reliability.

[0113] based on Figure 1 The diagram shown is a cross-sectional view of a leadless glass substrate micro-hot plate according to an embodiment of the present disclosure. Figure 2 The flowchart shown illustrates a method for preparing a leadless glass substrate micro-hotplate according to an embodiment of this disclosure, and... Figures 3 to 14 The flowchart shown illustrates the process for fabricating a leadless glass substrate micro-hot plate according to an embodiment of this disclosure. This disclosure also provides a gas sensor, which employs... Figure 1 The micro-hot plate shown is fabricated using a leadless glass substrate, or by employing... Figure 2 or Figures 3 to 14 The micro-hot plate was prepared by the method shown.

[0114] The embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. The leadless glass substrate micro-hotplate and its fabrication method provided in this disclosure utilize a leadless glass substrate, reducing the structural size of the micro-hotplate and the packaged device, which is beneficial for the further development of devices towards low power consumption, small size, and high integration. It should be noted that implementations not illustrated or described in the accompanying drawings or the main text of the specification are forms known to those skilled in the art and are not described in detail. Furthermore, the definitions of the various elements and methods described above are not limited to the specific structures, shapes, or methods mentioned in the embodiments, and those skilled in the art can easily modify or substitute them.

[0115] In summary, the leadless glass substrate micro-hotplate and its fabrication method disclosed in this disclosure utilize the lower thermal conductivity of the glass substrate compared to the silicon substrate. Using a glass substrate to fabricate the micro-hotplate effectively reduces heat loss and improves energy utilization. The glass substrate is integrally formed by softening and melting a glass wafer at high temperature and reflowing it into the etched silicon structure of the silicon wafer using a hot reflow process. This provides good support for the heating electrodes, insulating structures, and detection electrodes. Furthermore, the glass substrate fabrication technology eliminates the need for etching or corroding the glass, resulting in high-quality glass substrate formation and effectively improving the structural stability of the micro-hotplate. Simultaneously, this disclosure employs glass-silicon anode bonding and a glass hot reflow process to achieve simultaneous formation of the conductive silicon pillars and the micro-hotplate. The metal electrodes of the micro-hotplate are packaged and connected to the integrated circuit using solder joints. Compared to gold wire bonding, this significantly improves the device's resistance to mechanical and thermal shock, thereby increasing the device's structural stability and performance reliability.

[0116] Unless otherwise stated, the numerical parameters in this specification and the appended claims are approximate values ​​and can be varied according to desired characteristics derived from the content of this disclosure. Specifically, all figures used in the specification and claims to indicate composition, reaction conditions, etc., should be understood to be modified by the term "about" in all cases. Generally, this means that a specific amount may vary by ±10% in some embodiments, ±5% in some embodiments, ±1% in some embodiments, and ±0.5% in some embodiments.

[0117] The use of ordinal numbers such as “step S1”, “step S2”, “step S3”, etc., in the specification and claims to modify the corresponding elements does not imply that the element has any ordinal number, nor does it represent the order of one element with another element, or the order of manufacturing methods. The use of these ordinal numbers is only to enable a named element to be clearly distinguished from another element with the same name.

[0118] Similarly, it should be understood that, in order to simplify this disclosure and aid in understanding one or more of the various aspects of the disclosure, in the foregoing description of exemplary embodiments of the disclosure, various features of the disclosure are sometimes grouped together in a single embodiment, figure, or description thereof. However, this approach to disclosure should not be construed as reflecting an intention that the claimed disclosure requires more features than are expressly recited in each claim. Rather, as reflected in the following claims, the aspects of the disclosure consist of fewer than all features of a single foregoing disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the disclosure.

[0119] The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of this disclosure. It should be understood that the above descriptions are merely specific embodiments of this disclosure and are not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A method for preparing a leadless glass substrate micro-hot plate, characterized in that, The method includes: The front side of the silicon wafer is etched to form silicon grooves and conductive silicon pillars; The glass wafer is anodicly bonded to the front side of the etched silicon wafer, and a hot reflow process is used to soften and melt the glass wafer at high temperature, and then reflow it into the silicon structure of the etched silicon wafer to form a bulk glass. The upper surface of the bulk glass is planarized until the upper surface of the conductive silicon pillars is exposed, forming a glass thin film structure and a glass edge structure. The back side of the silicon wafer is thinned until the lower surface of the conductive silicon pillar is exposed; A heating electrode, an insulating structure, and a detection electrode are formed on a glass thin film structure; An ohmic contact metal is formed on the lower surface of the conductive silicon pillars exposed on the back side of the silicon wafer; and The silicon wafer under the glass film structure is etched from the back side of the silicon wafer until the glass film structure is suspended, forming a heat insulation groove below the glass film structure.

2. The method for preparing a leadless glass substrate micro-hot plate according to claim 1, characterized in that, The etching of the front side of the silicon wafer to form silicon grooves and conductive silicon pillars includes: Double-surface polishing and crystal orientation are selected. <100> Single-crystal silicon wafers with resistivity ≤0.001Ω·cm are used as silicon wafers; Using photoresist or SiO2 as a mask, photolithography and deep reactive ion etching processes are used to etch the front side of the silicon wafer to form silicon grooves; Photolithography and deep reactive ion etching processes are used to etch the front side of the silicon wafer on the outside of the silicon trench to form conductive silicon pillars.

3. The method for preparing a leadless glass substrate micro-hot plate according to claim 1, characterized in that, The process of anodicly bonding a glass wafer to the front side of an etched silicon wafer, and then using a hot reflow process to soften and melt the glass wafer at high temperature, reflowing it into the etched silicon structure of the silicon wafer to form a bulk glass, includes: BF33 high borosilicate glass was selected as the glass wafer. The glass wafer was anodicly bonded to the front side of the etched silicon wafer. The anodic bonding voltage was 800V~1000V, the temperature was 450℃, and the bonding time was 30min. In a high-temperature tube furnace, the anoly bonded glass wafer and silicon wafer are subjected to thermal reflow. The glass wafer is softened and melted at high temperature and then reflowed into the silicon structure of the etched silicon wafer to form a bulk glass. The thermal reflow temperature is 750℃~900℃.

4. The method for preparing a leadless glass substrate micro-hot plate according to claim 1, characterized in that, The planarization of the upper surface of the bulk glass and the thinning of the back side of the silicon wafer are both accomplished using chemical mechanical polishing.

5. The method for preparing a leadless glass substrate micro-hot plate according to claim 1, characterized in that, The process of forming a heating electrode, an insulating structure, and a detection electrode on a glass thin film structure includes: A heating electrode is formed on the glass thin film structure; An insulating structure is formed on the heating electrode and the glass thin film structure; and A detection electrode is formed on this insulating structure.

6. The method for preparing a leadless glass substrate micro-hot plate according to claim 1, characterized in that, The process of forming a heating electrode, an insulating structure, and a detection electrode on a glass thin film structure includes: A heating electrode and a detection electrode are simultaneously formed on a glass thin film structure by depositing an electrode layer, wherein the detection electrode is inside and the heating electrode is outside, forming an enclosed structure; and An insulating structure is formed between the metal strips forming the heating electrode and the detection electrode and on top of the glass thin film structure.

7. The method for preparing a leadless glass substrate micro-hot plate according to claim 1, characterized in that, The lower surface of the conductive silicon pillar exposed on the back side of the silicon wafer forms an ohmic contact metal, including: An ohmic contact metal is formed on the lower surface of the conductive silicon pillars exposed on the back side of a silicon wafer using photolithography etching or lift-off methods. The ohmic contact metal is made of metal Al and has a thickness of 0.3 μm to 1 μm.

8. The method for preparing a leadless glass substrate micro-hot plate according to claim 1, characterized in that, The etching process, which involves etching the silicon wafer beneath the glass thin-film structure from the back side of the silicon wafer until the glass thin-film structure is suspended, and forming a heat insulation groove beneath the glass thin-film structure, includes: Deep reactive ion etching technology is used to etch the silicon wafer directly below the glass thin film structure from the back of the silicon wafer until the glass thin film structure is suspended, forming a heat insulation groove below the glass thin film structure, thus completing the fabrication of the entire micro hot plate. The heat insulation groove is a cavity formed by etching the silicon wafer directly below the glass thin film structure after the glass wafer has undergone thermal reflow.

9. The method for preparing a leadless glass substrate micro-hot plate according to claim 1, characterized in that, After completing the fabrication of the entire micro-hotplate, the method also includes: The micro hotplate and integrated circuit are packaged without leads using solder joints.

10. A leadless glass substrate micro-hot plate, prepared by any one of claims 1 to 9.

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