MEMS pressure sensor and manufacturing method thereof
By forming induction capacitors and reference capacitors during the manufacturing process of the MEMS pressure sensor, the problem of low accuracy in the prior art caused by air conductor holes through the polysilicon layer is solved, and higher accuracy and accuracy are achieved.
Patent Information
- Application Number
- CN202311544918.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-17
- Publication Date
- 2025-05-20
AI Technical Summary
During the manufacturing process, the air conductor holes of the existing capacitive MEMS pressure sensors need to penetrate at least one polysilicon layer, resulting in low accuracy.
By sequentially forming the first sacrificial layer, the second sacrificial layer, and the second sacrificial layer on the first conductive layer, and patterning the opening exposing the second conductive layer on the second sacrificial layer, and then bonding the third conductive layer, an induction capacitor and a reference capacitor are formed.
The accuracy and accuracy of the MEMS pressure sensor are improved, and the damage to the conductive layer forming the induction capacitor is avoided.
Smart Images
Figure CN120020502A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of semiconductor technology, and more particularly to a MEMS pressure sensor and a manufacturing method thereof. Background Art
[0002] With the development of Micro-Electro-Mechanical System (MEMS) technology, pressure sensors have become indispensable key devices in many industries and have been widely used in fields such as consumer electronics, automotive electronics, petrochemical industry, biomedicine, and national defense. Compared with piezoresistive pressure sensors, capacitive pressure sensors have advantages such as high sensitivity, low power consumption, and good temperature characteristics.
[0003] Currently, capacitive pressure sensors mainly use two polysilicon layers as the upper and lower electrodes of the capacitive pressure sensor, and release the sacrificial dielectric layer between the two polysilicon layers through air vents to form a movable structure. The air vents need to penetrate at least one polysilicon layer. Although this manufacturing method has a simple process, its accuracy is not high. Summary of the Invention
[0004] A series of simplified concepts are introduced in the Summary of the Invention section, which will be further described in detail in the Detailed Description section. The Summary of the Invention section of the present invention does not mean to attempt to define the key features and essential technical features of the claimed technical solution, nor does it mean to attempt to determine the protection scope of the claimed technical solution.
[0005] The present invention provides a manufacturing method of a MEMS pressure sensor, including:
[0006] Providing a first substrate, and forming a first conductive layer on the upper surface of the first substrate;
[0007] Sequentially forming a first sacrificial layer, a second conductive layer, and a second sacrificial layer on the first conductive layer;
[0008] Patterning the second sacrificial layer to form an opening exposing the second conductive layer in the second sacrificial layer;
[0009] Bonding a third conductive layer on the patterned second sacrificial layer;
[0010] Wherein, the second conductive layer and the third conductive layer form an induction capacitor, and the first conductive layer and the second conductive layer form a reference capacitor.
[0011] Exemplarily, the first conductive layer and the second conductive layer are fixed electrodes, and the third conductive layer is a movable electrode.
[0012] Exemplarily, a cavity is formed between the second conductive layer and the third conductive layer by the patterned second sacrificial layer, and the cavity is in a vacuum or the air pressure in the cavity is less than 0.1 MPa.
[0013] Exemplarily, there is no cavity between the first conductive layer and the second conductive layer.
[0014] Exemplarily, bonding the third conductive layer on the patterned second sacrificial layer includes:
[0015] Bonding a second substrate on the patterned second sacrificial layer, and the second substrate includes a silicon-on-insulator substrate;
[0016] Removing the silicon base layer and the buried oxide layer of the silicon-on-insulator substrate, and using the single-crystalline silicon layer of the silicon-on-insulator substrate as the third conductive layer.
[0017] Exemplarily, forming the first conductive layer on the upper surface of the first substrate includes:
[0018] Performing ion implantation on the first substrate to form the first conductive layer on the upper surface of the first substrate.
[0019] Exemplarily, the second conductive layer includes a doped polysilicon layer, and the doping ions of the second conductive layer have the same ion type as the implanted ions of the first conductive layer.
[0020] The present invention also provides a MEMS pressure sensor, including:
[0021] A substrate, on the upper surface of which a first conductive layer is formed;
[0022] A first sacrificial layer, a second conductive layer, a patterned second sacrificial layer and a third conductive layer are sequentially formed on the first conductive layer; wherein, the second conductive layer and the third conductive layer form an induction capacitor, and the first conductive layer and the second conductive layer form a reference capacitor.
[0023] Exemplarily, the first conductive layer and the second conductive layer are fixed electrodes, and the third conductive layer is a movable electrode.
[0024] Exemplarily, the patterned second sacrificial layer forms a cavity between the second conductive layer and the third conductive layer, and there is no cavity between the first conductive layer and the second conductive layer.
[0025] According to the MEMS pressure sensor and its manufacturing method provided by the present invention, the MEMS pressure sensor includes an induction capacitor and a reference capacitor. Taking the reference capacitor as a benchmark, the accuracy of the MEMS pressure sensor is improved. In addition, the present invention forms the induction capacitor by a bonding method, avoiding damage to the conductive layer forming the induction capacitor and improving the precision of the MEMS pressure sensor. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The following drawings of the present invention are used as a part of the present invention to understand the present invention. The embodiments of the present invention shown in the drawings and their descriptions are used to explain the principles of the present invention.
[0027] In the drawings:
[0028] Figure 1 is a flowchart of a manufacturing method of a MEMS pressure sensor according to an embodiment of the present invention;
[0029] Figures 2A - 2E is a cross-sectional schematic view of the structure obtained by successively implementing the manufacturing method of the MEMS pressure sensor according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0030] In the following description, numerous specific details are given to provide a more thorough understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without one or more of these details. In other instances, some well-known technical features are not described to avoid confusion with the present invention.
[0031] It should be understood that the present invention can be implemented in different forms and should not be construed as limited to the embodiments presented herein. On the contrary, these embodiments are provided to make the disclosure thorough and complete and to fully convey the scope of the present invention to those skilled in the art. In the drawings, for clarity, the dimensions and relative dimensions of layers and regions may be exaggerated. The same reference numerals denote the same elements throughout.
[0032] It should be understood that when an element or layer is referred to as being "on", "adjacent to", "connected to" or "coupled to" another element or layer, it can be directly on, adjacent to, connected or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as being "directly on", "directly adjacent to", "directly connected to" or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and / or portions, these elements, components, regions, layers and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or portion from another element, component, region, layer or portion. Thus, a first element, component, region, layer or portion discussed below may be denoted as a second element, component, region, layer or portion without departing from the teachings of the present invention.
[0033] Spatial relationship terms such as "under", "below", "beneath", "underneath", "above", "over", etc. are used herein for convenience in describing the relationship of one element or feature shown in the figures to other elements or features. It should be understood that, in addition to the orientation shown in the figures, spatial relationship terms are intended to include different orientations of the device in use and operation. For example, if the device in the figures is flipped, then an element or feature described as "under" or "beneath" or "underneath" another element or feature will be oriented "over" the other element or feature. Thus, the exemplary terms "under" and "beneath" can include both an upper and a lower orientation. The device may be otherwise oriented (rotated 90 degrees or other orientation) and the spatial descriptors used herein are to be interpreted accordingly.
[0034] The purpose of the terms used herein is only to describe specific embodiments and is not a limitation of the present invention. As used herein, the singular forms "a", "an" and "the" are also intended to include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprising" and / or "including", when used in this specification, specify the presence of the stated features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups. As used herein, the term "and / or" includes any and all combinations of the associated listed items.
[0035] To fully understand the present invention, detailed steps and detailed structures will be presented in the following description to illustrate the technical solutions proposed by the present invention. The preferred embodiments of the present invention are described in detail below. However, in addition to these detailed descriptions, the present invention may have other embodiments.
[0036] The present invention provides a manufacturing method for a MEMS pressure sensor, as Figure 1 shown, including:
[0037] Step S110: Provide a first substrate, and form a first conductive layer on the upper surface of the first substrate;
[0038] Step S120: Sequentially form a first sacrificial layer, a second conductive layer, and a second sacrificial layer on the first conductive layer;
[0039] Step S130: Pattern the second sacrificial layer to form an opening exposing the second conductive layer in the second sacrificial layer;
[0040] Step S140: Bond a third conductive layer on the patterned second sacrificial layer;
[0041] Wherein, the second conductive layer and the third conductive layer form an induction capacitor, and the first conductive layer and the second conductive layer form a reference capacitor.
[0042] Next, with reference to Figures 2A to 2E a detailed description will be given of the manufacturing method for the MEMS pressure sensor of the present invention, wherein, Figures 2A to 2E is a cross-sectional schematic view of the structure obtained by sequentially implementing the manufacturing method for the MEMS pressure sensor according to an embodiment of the present invention.
[0043] First, perform step S110, as Figure 2A shown, provide a first substrate 200, and form a first conductive layer 210 on the upper surface of the first substrate.
[0044] In one embodiment, the first substrate 200 can be any suitable semiconductor substrate, such as a silicon substrate, and it can also be at least one of the following materials: Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, or other III / V compound semiconductors, and also includes multilayer structures composed of these semiconductor materials, etc., or is a silicon-on-insulator (SOI) substrate, stacked silicon-on-insulator (SSOI), stacked silicon-germanium-on-insulator (S-SiGeOI), silicon-germanium-on-insulator (SiGeOI), and germanium-on-insulator (GeOI), or can also be a double-sided polished silicon wafer (Double Side Polished Wafers, DSP), and can also be an aluminum 2 O 3 sapphire substrate such as, ceramic substrate, quartz or glass substrate, etc.
[0045] Exemplarily, forming the first conductive layer 210 on the upper surface of the first substrate 200 includes: performing ion implantation on the first substrate 200 to form the first conductive layer 210 on the upper surface of the first substrate 200.
[0046] In one embodiment, the ion implantation injects P-type doping ions (such as boron ions, gallium ions) or N-type doping ions (such as phosphorus ions, arsenic ions) into the upper surface of the first substrate 200. Specifically, the implantation angle, implantation energy, implantation dose, etc. of the ion implantation can all be set as needed, and this application does not limit this. After the ion implantation, an annealing step is further included, and both the annealing temperature and annealing time can be set as needed, and this application does not limit this.
[0047] In one embodiment, the material of the first conductive layer 210 includes but is not limited to polysilicon or doped polysilicon. Any existing technology well-known to those skilled in the art can be adopted for the conventional semiconductor process method of forming the first conductive layer 210, preferably chemical vapor deposition (CVD), such as low-temperature chemical vapor deposition (LTCVD), low-pressure chemical vapor deposition (LPCVD), metalorganic chemical vapor deposition (MOCVD), rapid thermal chemical vapor deposition (RTCVD), plasma-enhanced chemical vapor deposition (PECVD).
[0048] Next, step S120 is performed, as Figure 2B shown, a first sacrificial layer 220, a second conductive layer 230, and a second sacrificial layer 240 are sequentially formed on the first conductive layer 210.
[0049] In one embodiment, as Figure 2B shown, first, a first sacrificial layer 220 is formed on the first conductive layer 210. The material of the first sacrificial layer 220 includes but is not limited to silicon dioxide. Any existing technology well-known to those skilled in the art, such as LPCVD or PECVD, can be adopted for the formation method of the first sacrificial layer 220, and details are not described herein again.
[0050] In one embodiment, as Figure 2B shown, the second conductive layer 230 is directly formed on the first sacrificial layer 220. The material of the second conductive layer 230 includes but is not limited to polysilicon or doped polysilicon. Any existing technology well-known to those skilled in the art, such as LPCVD or PECVD, can be adopted for the formation method of the second conductive layer 230, and details are not described herein again. It should be noted that when the material of the second conductive layer 230 is a doped polysilicon layer, the doping ions of the second conductive layer 230 have the same ion type as the implanted ions of the first conductive layer 210.
[0051] In one embodiment, since the second conductive layer 230 is directly formed on the first sacrificial layer 220 without any etching or other processing on the first sacrificial layer 220, the first sacrificial layer 220 between the first conductive layer 210 and the second conductive layer 230 is intact, and there is no cavity between the first conductive layer 210 and the second conductive layer 230. Therefore, both the first conductive layer 210 and the second conductive layer 230 are fixed electrodes, and the first conductive layer 210 and the second conductive layer 230 form a reference capacitor, which does not change with the change of the externally applied pressure. The MEMS pressure sensor can use the stable reference capacitor as a benchmark, improving the accuracy of the MEMS pressure sensor.
[0052] Next, step S130 is executed. As Figure 2C shown, the second sacrificial layer 240 is patterned to form an opening in the second sacrificial layer that exposes the second conductive layer.
[0053] In one embodiment, the method of patterning the second sacrificial layer 240 to form an opening in the second sacrificial layer that exposes the second conductive layer includes: forming a mask layer (not shown) on the second sacrificial layer 240, patterning the mask layer using a photoresist, and etching the second sacrificial layer 240 using the patterned mask layer as a mask until the second conductive layer 230 is exposed to form an opening in the second sacrificial layer 240.
[0054] Next, step S140 is executed. As Figure 2D and 2E shown, a third conductive layer 250 is bonded on the patterned second sacrificial layer 240.
[0055] Exemplarily, bonding the third conductive layer 250 on the patterned second sacrificial layer 240 includes: bonding a second substrate 250' on the patterned second sacrificial layer 240, where the second substrate 250' includes a silicon-on-insulator (SOI) substrate; removing the silicon base layer and the buried oxide layer of the silicon-on-insulator substrate, and using the single-crystalline silicon layer of the silicon-on-insulator substrate as the third conductive layer 250.
[0056] In one embodiment, the second sacrificial layer 240 and the second substrate 250' are bonded, where the second substrate 250' uses a silicon-on-insulator (SOI), and the SOI substrate includes a three-layer structure from bottom to top: a silicon base layer 2501, a buried oxide layer 2502, and a single-crystalline silicon layer 2503. As Figure 2DAs shown. Specifically, chemical mechanical polishing (CMP) is performed on the surface of the second sacrificial layer 240 and the surface of the single-crystalline silicon layer 2503 in the second substrate 250' so that the surface of the second sacrificial layer 240 and the surface of the single-crystalline silicon layer 2503 in the second substrate 250' meet the bonding requirements, and then the surface of the second sacrificial layer 240 is directly and frontally bonded to the surface of the single-crystalline silicon layer 2503 in the second substrate 250' through plasma-activated bonding. Next, the silicon-based bottom layer 2501 and the buried oxide layer 2502 of the SOI substrate are removed by thinning processes such as etching or CMP, and only the single-crystalline silicon layer 2503 of the SOI substrate is retained as the third conductive layer 250, as Figure 2E shown.
[0057] In one embodiment, since an opening is formed in the second sacrificial layer 240, a cavity 260 is formed between the second conductive layer 230 and the third conductive layer 250 after the third conductive layer 250 is bonded to the patterned second sacrificial layer 240. The cavity 260 is in a vacuum or close to a vacuum (for example, the air pressure in the cavity is less than 0.1 MPa). Therefore, the third conductive layer 250 is a movable electrode plate, and the second conductive layer 230 and the third conductive layer 250 form a capacitive sensor.
[0058] In one embodiment, the first conductive layer 210, the second conductive layer 230, and the third conductive layer 250 are arranged in parallel or nearly in parallel (for example, the included angle is less than 5°). The first conductive layer 210 and the second conductive layer 230 are both fixed electrode plates to form a reference capacitor, and the second conductive layer 230 and the third conductive layer 250 are respectively a fixed electrode plate and a movable electrode plate to form a capacitive sensor. The first conductive layer 210 is led out as the first electrode P1, the second conductive layer 230 is led out as the second electrode P2, and the third conductive layer 250 is led out as the third electrode P3.
[0059] In one embodiment, since the first conductive layer 210, the second conductive layer 230, and the third conductive layer 250 are not etched or otherwise processed, the first conductive layer 210, the second conductive layer 230, and the third conductive layer 250 are all in a complete structure and no through holes are formed therein. Therefore, the accuracy of the MEMS pressure sensor is improved.
[0060] By using the single-crystalline silicon layer of the SOI substrate as the movable electrode plate of the capacitive sensor, since the single-crystalline silicon layer of the SOI substrate has basically no defects, a small and uniform stress level, and low-temperature annealing basically has no effect on this single-crystalline silicon layer during plasma-activated bonding, the accuracy and stability of the capacitive sensor can be improved.
[0061] Thus, the key steps of the manufacturing method of the MEMS pressure sensor of the present invention have been introduced. For the complete device preparation, multiple other process steps may be required, which will not be elaborated one by one here.
[0062] It is worth mentioning that the order of the above steps is only for example. On the premise of no conflict, the order of the above steps can also be swapped or carried out alternately, etc.
[0063] The present invention also provides a MEMS pressure sensor, as Figure 2E shown, including:
[0064] A substrate 200, on the upper surface of which a first conductive layer 210 is formed;
[0065] On the first conductive layer 210, a first sacrificial layer 220, a second conductive layer 230, a patterned second sacrificial layer 240 and a third conductive layer 250 are sequentially formed; wherein, the second conductive layer 230 and the third conductive layer 250 form a sensing capacitor, and the first conductive layer 210 and the second conductive layer 230 form a reference capacitor.
[0066] In one embodiment, the material of the first conductive layer 210 includes but is not limited to polysilicon or doped polysilicon. The material of the second conductive layer 230 includes but is not limited to polysilicon or doped polysilicon. It should be noted that when the materials of the first conductive layer 210 and the second conductive layer 230 are both doped polysilicon layers, the doping ions of the second conductive layer 230 have the same ion type as the doping ions of the first conductive layer 210. The third conductive layer 250 includes a single crystal silicon layer remaining after removing the silicon substrate layer and the buried oxide layer of the silicon-on-insulator (SOI) substrate. Using the single crystal silicon layer of the SOI substrate as the third conductive layer 250, since the single crystal silicon layer of the SOI substrate is basically defect-free, has a small and uniform stress level, and during plasma-activated bonding, low-temperature annealing basically has no effect on this single crystal silicon layer, the accuracy and stability of the MEMS pressure sensor can be improved.
[0067] In one embodiment, the first sacrificial layer 220 is not patterned. Therefore, the first sacrificial layer 220 between the first conductive layer 210 and the second conductive layer 230 is complete, and there is no cavity between the first conductive layer 210 and the second conductive layer 230. The second sacrificial layer 240 is a patterned second sacrificial layer. Therefore, a cavity 260 is formed between the second conductive layer 230 and the third conductive layer 250. The cavity 260 is a vacuum or close to a vacuum (for example, the air pressure in the cavity is less than 0.1 MPa). Therefore, both the first conductive layer 210 and the second conductive layer 230 are fixed plates, the third conductive layer 250 is a movable plate, the first conductive layer 210 and the second conductive layer 230 form a reference capacitor, and the second conductive layer 230 and the third conductive layer 250 form a sensing capacitor. Since the reference capacitor does not change with the change of the externally applied pressure, the MEMS pressure sensor can use the stable reference capacitor as a reference, improving the accuracy of the MEMS pressure sensor.
[0068] In one embodiment, the first conductive layer 210, the second conductive layer 230, and the third conductive layer 250 are arranged in parallel or nearly parallel (e.g., the included angle is less than 5°). The first conductive layer 210 and the second conductive layer 230 form a reference capacitor, and the second conductive layer 230 and the third conductive layer 250 form a sensing capacitor. The first conductive layer 210 is led out as the first electrode P1, the second conductive layer 230 is led out as the second electrode P2, and the third conductive layer 250 is led out as the third electrode P3.
[0069] In one embodiment, the first conductive layer 210, the second conductive layer 230, and the third conductive layer 250 are all of complete structures, and no vias are formed therein. Therefore, the accuracy of the MEMS pressure sensor is improved.
[0070] According to the MEMS pressure sensor and its manufacturing method provided by the present invention, the MEMS pressure sensor includes a sensing capacitor and a reference capacitor. Taking the reference capacitor as a benchmark, the accuracy of the MEMS pressure sensor is improved. In addition, in the present invention, the sensing capacitor is formed by a bonding method, which avoids damage to the conductive layer forming the sensing capacitor and improves the accuracy of the MEMS pressure sensor.
[0071] The present invention has been described through the above embodiments. However, it should be understood that the above embodiments are only for the purpose of exemplification and illustration, and are not intended to limit the present invention to the scope of the described embodiments. In addition, those skilled in the art can understand that the present invention is not limited to the above embodiments, and more variations and modifications can be made according to the teachings of the present invention, and these variations and modifications all fall within the scope claimed by the present invention. The protection scope of the present invention is defined by the appended claims and their equivalent scope.
Claims
1. A method for manufacturing a MEMS pressure sensor, characterized in that: include: Providing a first substrate, and forming a first conductive layer on an upper surface of the first substrate; forming a first sacrificial layer, a second conductive layer, and a second sacrificial layer in sequence on the first conductive layer; patterning the second sacrificial layer to form an opening in the second sacrificial layer exposing the second conductive layer; bonding a third conductive layer on the patterned second sacrificial layer; The second conductive layer and the third conductive layer form an inductive capacitor, and the first conductive layer and the second conductive layer form a reference capacitor.
2. The method according to claim 1, characterized in that The first conductive layer and the second conductive layer are fixed electrodes, and the third conductive layer is a movable electrode.
3. The method according to claim 2, characterized in that The patterned second sacrificial layer forms a cavity between the second conductive layer and the third conductive layer, and the cavity is a vacuum or the gas pressure of the cavity is less than 0.1 MPa.
4. The method according to claim 2, characterized in that There is no cavity between the first conductive layer and the second conductive layer.
5. The method according to claim 1, characterized in that Bonding a third conductive layer on the patterned second sacrificial layer comprises: bonding a second substrate on the patterned second sacrificial layer, the second substrate comprising a silicon-on-insulator substrate; The silicon base layer and the buried oxide layer of the silicon-on-insulator substrate are removed, and the single crystal silicon layer of the silicon-on-insulator substrate is used as the third conductive layer.
6. The method according to claim 1, characterized in that Forming a first conductive layer on the upper surface of the first substrate includes: Ion implantation is performed on the first substrate to form a first conductive layer on an upper surface of the first substrate.
7. The method according to claim 6, characterized in that The second conductive layer includes a doped polysilicon layer, and doping ions of the second conductive layer are of the same ion type as implanted ions of the first conductive layer.
8. A MEMS pressure sensor, characterized in that: include: A substrate, a first conductive layer being formed on an upper surface of the substrate; A first sacrificial layer, a second conductive layer, a patterned second sacrificial layer and a third conductive layer are sequentially formed on the first conductive layer; The second conductive layer and the third conductive layer form an inductive capacitor, and the first conductive layer and the second conductive layer form a reference capacitor.
9. The MEMS pressure sensor according to claim 8, characterized in that: The first conductive layer and the second conductive layer are fixed electrodes, and the third conductive layer is a movable electrode.
10. The MEMS pressure sensor according to claim 9, wherein: The patterned second sacrificial layer forms a cavity between the second conductive layer and the third conductive layer, and there is no cavity between the first conductive layer and the second conductive layer.