Micro-electro-mechanical system unit and capacitive pressure sensor

Abstract

The embodiment of the invention provides an MEMS unit and a capacitive pressure sensor. The MEMS unit includes: a housing including a first wall portion and a second wall portion opposite to each other, and a cavity located between the first wall portion and the second wall portion, the first wall portion being adapted to deform in a first direction toward the second wall portion under pressure from an external environment; at least one first electrode plate arranged to extend from the first wall portion into the cavity and adapted to be electrically connected to a first potential; and at least one second electrode plate arranged to extend from the second wall portion into the cavity and adapted to be electrically connected to a second potential different from the first potential, the at least one second electrode plate is separated from the at least one first electrode plate in at least one of a second direction and a direction opposite to the second direction to form at least one capacitance, and the second direction intersects the first direction. The scheme disclosed by the invention is helpful for eliminating or relieving the adverse effect of the change of the external environment on the capacitive pressure sensor.

Description

Technical Field

[0001] The present disclosure relates to the field of microelectromechanical systems (MEMS), and more particularly, to MEMS units and capacitive pressure sensors including such MEMS units. Background Art

[0002] Microelectromechanical systems (MEMS) refer to microelectromechanical devices with an outer contour dimension below the millimeter level fabricated using microfabrication techniques. MEMS technology can be used to manufacture various types of micro sensing devices or sensors, such as capacitive pressure sensors. MEMS sensing devices or sensors have advantages such as small size, light weight, low energy consumption, and short response time, and thus are widely used in various industrial fields.

[0003] Currently, capacitive pressure sensors using MEMS technology still have some deficiencies. For example, the measurement results are susceptible to non-pressure factors (such as humidity) in the external environment, and the linearity is not good. Summary of the Invention

[0004] To at least partially solve the above and other possible problems, embodiments of the present disclosure provide an improved MEMS unit and a capacitive pressure sensor including such MEMS unit.

[0005] According to a first aspect of the present disclosure, there is provided an MEMS unit, comprising: a housing including a first wall portion and a second wall portion opposite to each other, and a cavity located between the first wall portion and the second wall portion, the first wall portion being adapted to deform in a first direction towards the second wall portion under pressure from the external environment; at least one first electrode plate arranged to extend from the first wall portion into the cavity and adapted to be electrically connected to a first potential; and at least one second electrode plate arranged to extend from the second wall portion into the cavity and adapted to be electrically connected to a second potential different from the first potential, the at least one second electrode plate being separated from the at least one first electrode plate in at least one of a second direction and a direction opposite to the second direction to form at least one capacitor, the second direction intersecting the first direction.

[0006] In some embodiments of the present disclosure, the second direction is perpendicular to the first direction.

[0007] In some embodiments of the present disclosure, the at least one first electrode plate and the at least one second electrode plate are arranged to at least partially overlap in the second direction.

[0008] In some embodiments of the present disclosure, the at least one first electrode plate includes a plurality of first electrode plates, and the at least one second electrode plate includes a plurality of second electrode plates.

[0009] In some embodiments of the present disclosure, a plurality of first electrode plates and a plurality of second electrode plates are arranged alternately.

[0010] In some embodiments of the present disclosure, the MEMS unit further includes: a first conductive terminal electrically connected to the plurality of first electrode plates; and a second conductive terminal electrically connected to the plurality of second electrode plates.

[0011] In some embodiments of the present disclosure, the housing is arranged to hermetically isolate the cavity from the external environment.

[0012] In some embodiments of the present disclosure, when observed in a first direction, the electrode plates among at least one first electrode plate and at least one second electrode plate have at least one of the following shapes: bar-shaped, circular, square, and rectangular.

[0013] According to a second aspect of the present disclosure, there is provided a capacitive pressure sensor, which includes: the MEMS unit according to the first aspect.

[0014] In some embodiments of the present disclosure, the capacitive pressure sensor further includes: a processing unit configured to determine the pressure from the external environment based on the capacitance value of the MEMS unit.

[0015] In some embodiments of the present disclosure, the capacitive pressure sensor further includes a reference capacitor, and the capacitance value of the reference capacitor is equal to the capacitance value of the MEMS unit when no pressure from the external environment is applied.

[0016] In some embodiments of the present disclosure, the capacitive pressure sensor includes a variable capacitor and at least two reference capacitors, wherein the variable capacitor, the at least two reference capacitors, and the MEMS unit are connected in a Wheatstone bridge manner.

[0017] The summary of the invention is provided to introduce a selection of concepts in a simplified form, which will be further described in the detailed implementation below. The summary of the invention is not intended to identify the key features or main features of the present disclosure, nor is it intended to limit the scope of the present disclosure. Brief Description of the Drawings

[0018] By describing the exemplary embodiments of the present disclosure in more detail in conjunction with the drawings, the above and other objects, features, and advantages of the present disclosure will become more apparent, wherein in the exemplary embodiments of the present disclosure, the same reference numerals generally represent the same components.

[0019] Figure 1 A schematic structural diagram showing the MEMS structure of the pressure sensor is shown.

[0020] Figure 2 A schematic block diagram showing the capacitive pressure sensor according to an embodiment of the present disclosure is shown.

[0021] Figure 3 Shows a side view of a MEMS unit according to an embodiment of the present disclosure.

[0022] Figure 4 Shows a top view of a MEMS unit according to an embodiment of the present disclosure.

[0023] Figure 5 Shows a side view of a MEMS unit without pressure applied according to an embodiment of the present disclosure.

[0024] Figure 6 Shows a schematic diagram of the capacitive connection of a MEMS unit without pressure applied according to an embodiment of the present disclosure.

[0025] Figure 7 Shows a side view of a MEMS unit with pressure applied according to an embodiment of the present disclosure.

[0026] Figure 8 Shows a schematic diagram of the capacitive connection of a MEMS unit with pressure applied according to an embodiment of the present disclosure.

[0027] Figure 9 Shows a top view of a MEMS unit according to another embodiment of the present disclosure. Detailed Description

[0028] Embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present disclosure more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art. Those skilled in the art can obtain alternative technical solutions from the following description without departing from the spirit and scope of the present disclosure.

[0029] The term "including" and its variations used herein mean open inclusion, i.e., "including but not limited to". Unless otherwise specified, the term "or" means "and / or". The term "based on" means "at least partially based on". The terms "an example embodiment" and "an embodiment" mean "at least one example embodiment". There may also be other explicit and implicit definitions hereinafter.

[0030] Figure 1 Shows a schematic structural diagram of a MEMS structure 100' of a pressure sensor. As Figure 1As shown, the MEMS structure 100’ includes an upper capacitor plate 110’ and a lower capacitor plate 120’. The upper capacitor plate 110’ and the lower capacitor plate 120’ are separated by a dielectric to form a capacitor C’. Under the action of an external pressure P’, the magnitude of the capacitor C’ will change. Thus, by measuring the change in the capacitor C’ in the MEMS structure 100’, the magnitude of the external pressure P’ can be determined. Specifically, the relationship between the capacitor C’ and the external pressure P’ can be expressed by the following equation:

[0031]

[0032] where ε0 is the vacuum permittivity, ε r is the permittivity of the dielectric between the upper and lower capacitor plates, A is the area of the parts of the upper capacitor plate 110’ and the lower capacitor plate 120’ that face each other, P’ is the effective pressure applied to the MEMS structure 100’, and d is the distance between the upper capacitor plate 110’ and the lower capacitor plate 120’. The distance d between the upper capacitor plate 110’ and the lower capacitor plate 120’ changes with the increase and decrease of the pressure P’. For example, when the pressure P’ increases, the distance d decreases, and when the pressure P’ decreases, the distance d increases. Therefore, the distance d can be expressed as a function of the pressure P’.

[0033] Generally speaking, ε0, ε r and A in equation (1) are all constants or set values. Thus, it can be seen that based on equation (1) and by measuring the capacitance magnitude of the capacitor C’, the magnitude of the external pressure P’ can be determined. However, there are still some problems in using this kind of MEMS structure for pressure sensing. For example, the MEMS structure 100’ is often affected by non-pressure factors in the external environment, resulting in inaccurate pressure sensing results.

[0034] Research shows that in addition to the capacitor C’, there is actually a capacitor C” in the MEMS structure 100’ (see Figure 1 ), which is formed between the two capacitor plates 110’ and 120’ and the external environment and is in parallel with the capacitor C’. Therefore, the actually measured capacitance magnitude of the MEMS structure will depend on the magnitudes of both the capacitor C’ and the capacitor C”. However, the capacitor C” is affected not only by the pressure P’ but also by non-pressure factors in the external environment. For example, when the humidity in the external environment changes, the air permittivity in the external environment will also change (i.e., ε in equation (1)) rWhen it changes, it will change the magnitude of the capacitance C'', and thus change the magnitude of the measured total capacitance. That is to say, the change in the measured total capacitance is no longer uniquely related to the change in the distance d, which deteriorates the accuracy of pressure sensing. For example, in an application scenario where such a pressure sensor is used to sense changes in air pressure and estimate altitude accordingly, due to the significant differences in humidity at different altitudes, the accuracy of this pressure sensor will be poor, resulting in errors of several meters or even dozens of meters in estimating altitude.

[0035] In addition, the change in the distance d in the MEMS structure 100' depends on the deformation of the capacitor plate 110'. However, changes in the external environment (such as temperature changes) will also affect or interfere with the deformation of the capacitor plate, especially Figure 1 for the relatively long capacitor plate 110' shown in [the figure], which is prone to expansion or contraction with temperature, and this will have an adverse effect on the linearity of the sensing result. In addition, in addition to capacitive pressure sensors, in traditional piezoresistive pressure sensors, the adverse effect of external environment changes on linearity is more significant because there are multiple layers made of different materials stacked on top of each other in piezoresistive pressure sensors, and the thermal expansion coefficients of the respective layers of different materials are not the same, making the linearity of the sensing result significantly deteriorated.

[0036] In an embodiment of the present disclosure, an improved MEMS structure of a capacitive pressure sensor is provided. In the improvement scheme, the electrode plates are arranged to extend from two opposite wall portions into the internal cavity to form a capacitor, so as to minimize the influence of non-pressure factors in the external environment on the accuracy of pressure sensing. In addition, some embodiments of the present disclosure help to improve the linearity of the pressure sensing result, as well as reduce the occupied area and volume of the pressure sensor and lower the cost.

[0037] Figure 2 The schematic block diagram of a capacitive pressure sensor 10 according to an embodiment of the present disclosure is shown. The capacitive pressure sensor 10 can sense the pressure in the external environment by using capacitance changes. For example, the capacitive pressure sensor 10 can sense the air pressure, so as to help the electronic device provided with this sensor determine its altitude. However, it can be understood that the application of the capacitive pressure sensor 10 is not limited to this, but can be used to sense other types of pressure. As Figure 2As shown, the capacitive pressure sensor 10 includes a MEMS unit 100 and a processing unit 200. The MEMS unit 100 is provided with a capacitor that varies with pressure, and the processing unit 200 determines the pressure from the external environment based on the capacitance value of the MEMS unit 100. In some embodiments, the capacitive pressure sensor 10 may further include a reference capacitor, the capacitance value of which is equal to the capacitance value of the MEMS unit 100 when no pressure from the external environment is applied. By comparing the capacitance value of the MEMS unit 100 with the capacitance value of the reference capacitor, it is convenient to obtain the capacitance change caused by the pressure to determine the pressure magnitude. In some embodiments, the capacitive pressure sensor 10 may further include a variable capacitor and at least two reference capacitors, wherein the variable capacitor, the at least two reference capacitors, and the MEMS unit 100 are connected in the form of a Wheatstone bridge. With the aid of the Wheatstone bridge, the capacitance change of the MEMS unit 100 can be determined more precisely, thus helping to obtain a high-precision pressure sensing result.

[0038] Figure 3 A side view of the MEMS unit 100 according to an embodiment of the present disclosure is shown, and Figure 4 A top view of the MEMS unit 100 according to an embodiment of the present disclosure is shown. As Figure 3 and Figure 4 shown, the MEMS unit 100 includes a housing, which includes a first wall portion 110 and a second wall portion 120 opposite to each other, and a cavity 180 located between the first wall portion 110 and the second wall portion 120. The first wall portion 110 is adapted to deform in a first direction D1 toward the second wall portion 120 under the pressure P from the external environment.

[0039] As an example, the MEMS unit 100 can be obtained by processing a bare chip or wafer through semiconductor processes such as deposition, etching, and lithography. The first wall portion 110 can be a protective layer formed after processing, and the second wall portion 120 can be an oxide insulating layer formed after processing. In one embodiment, the housing of the MEMS unit 100 may further include sidewalls 150 and a substrate 160. The sidewalls 150 and the substrate 160 can provide support and connection for other parts of the MEMS unit 100, and can enclose the cavity 180 together with the first wall portion 110 and the second wall portion 120. In some embodiments of the present disclosure, the housing of the MEMS unit 100 is arranged to hermetically isolate the cavity 180 from the external environment. Through this arrangement, it is possible to avoid the influence of factors such as humidity, air flow, and dust in the external environment on the cavity 180 to obtain higher sensing accuracy. In one embodiment, the air pressure inside the cavity 180 is lower than the air pressure of the external environment. Thus, a pressure difference can be generated inside and outside the cavity to deform the first wall portion 110, and this deformation can be used to effectively sense the air pressure change of the external environment.

[0040] According to an embodiment of the present disclosure, the MEMS unit 100 includes at least one first electrode plate (e.g., electrode plates 130-1... 130-N) and at least one second electrode plate (e.g., electrode plates 140-1... 140-N). The first electrode plate is arranged to extend from the first wall portion 110 into the cavity 180 and is adapted to be electrically connected to a first potential, while the second electrode plate is arranged to extend from the second wall portion 120 into the cavity 180 and is adapted to be electrically connected to a second potential different from the first potential. The second electrode plate (e.g., electrode plate 140-2) may be separated from the first electrode plate (e.g., electrode plate 130-1) in a second direction D2 intersecting the first direction D1 to form a capacitance, as Figure 3 shown in the CA region. Additionally or alternatively, the second electrode plate (e.g., electrode plate 140-2) may also be separated from the first electrode plate (e.g., electrode plate 130-2) in a third direction D3 opposite to the second direction D2 to form a capacitance, as Figure 3 shown in the CB region.

[0041] In this way, when a pressure P (e.g., air pressure) is applied to the first wall portion 110 along the first direction D1, at least a change in the relative area between the first electrode plate and the second electrode plate will be caused. Thereby, the capacitance of the CA region and / or the CB region formed by the two electrode plates can change with the pressure P, so as to realize the sensing of the pressure P. This arrangement can effectively improve the accuracy of pressure sensing. Specifically, the entire electrode plate and the regions CA and / or CB for constructing the capacitance are arranged within the cavity 180. Thus, the first electrode plate and the second electrode plate achieve capacitance coupling all or mainly through the dielectric within the cavity, rather than or very little through the external environment for capacitance coupling. This effectively avoids capacitance changes caused by non-pressure factors (e.g., humidity changes) in the external environment, thereby eliminating or alleviating the adverse effects of the external environment on pressure sensing.

[0042] In some embodiments of the present disclosure, the second direction D2 or the third direction D3 is perpendicular to the first direction D1. In this way, when the pressure P is applied along the first direction D1, only a change in the relative plate area between the first electrode plate and the second electrode plate will be caused. In some embodiments of the present disclosure, the first electrode plate and the second electrode plate are arranged to at least partially overlap in the second direction D2. Thereby, it can be ensured that there is always a part of the plates of the first electrode plate and the second electrode plate facing each other, so that a capacitor with better electrical performance can be formed, which helps to accurately determine the capacitance change caused by the pressure. As an example, the capacitance C of the MEMS unit 100 can be represented by the following formula:

[0043]

[0044] where ε0 is the permittivity of free space, and ε r is the permittivity of the dielectric between or around the first electrode plate and the second electrode plate, A is the area of the portions of the first electrode plate and the second electrode plate that face each other, P is the effective pressure applied to the MEMS unit 100, and d is the distance between the first electrode plate and the second electrode plate. The area A of the portions of the first electrode plate and the second electrode plate that face each other changes as the pressure P increases and decreases. For example, when the pressure P increases, the area A increases, and when the pressure P decreases, the area A decreases. Therefore, the distance A can be expressed as a function of the pressure P. Since the first electrode plate and the second electrode plate are disposed in the cavity 180, the dielectric between or around the first electrode plate and the second electrode plate is not or less affected by the external environment, and ε r can remain substantially constant. Thereby, it is ensured that the capacitance change is only related to the pressure P, thus improving the sensing accuracy.

[0045] In some embodiments of the present disclosure, the first electrode plate includes a plurality of electrode plates 130-1, 130-2, 130-3... 130-N, and the second electrode plate includes a plurality of electrode plates 140-1, 140-2, 140-3... 140-N. N can be a positive integer greater than 1, such as 10 or 11, and the number of the first electrode plate and the second electrode plate can be the same or different. It can be understood that only one first electrode plate and one second electrode plate can also be provided. However, it is more advantageous to use a plurality of first electrode plates and a plurality of second electrode plates because more electrode plates can form or construct more capacitors that change with the pressure P. Thereby, the occupied area and volume of the MEMS unit can be reduced while ensuring the sensing accuracy, and thus the cost can be reduced. In addition, compared with Figure 1 the scheme of a single pair of capacitor plates, arranging multiple pairs of electrode plates in the cavity to form multiple capacitors can effectively reduce the size of a single electrode plate, and the relatively small-sized electrode plates are less susceptible to temperature changes. Thereby, the influence of environmental factors such as temperature on the electrode plates is minimized, thus improving the linearity of the sensing result, that is, the capacitance change at different pressures has better linearity.

[0046] In some embodiments of the present disclosure, a plurality of first electrode plates 130-1, 130-2, 130-3... 130-N and a plurality of second electrode plates 140-1, 140-2, 140-3... 140-N are arranged alternately. The alternate arrangement can ensure that each first electrode plate forms a capacitance with two adjacent second electrode plates before and after it, or each second electrode plate forms a capacitance with two adjacent first electrode plates before and after it. Thus, the first electrode plates, the second electrode plates, and the cavity space can be utilized with maximum efficiency. In some embodiments, the MEMS unit 100 further includes a first conductive terminal 171 and a second conductive terminal 172. The first conductive terminal 171 is electrically connected to the plurality of first electrode plates 130-1, 130-2, 130-3... 130-N, and the second conductive terminal 172 is electrically connected to the plurality of second electrode plates 140-1, 140-2, 140-3... 140-N. Specifically, the plurality of first electrode plates 130-1, 130-2, 130-3... 130-N are connected to a common conductive end and the same potential, and the plurality of second electrode plates 140-1, 140-2, 140-3... 140-N are connected to another common conductive end and another potential. For example, the first electrode plates 130-1, 130-2, 130-3... 130-N can be connected to the first conductive terminal 171 via conductive connectors 131, and the second electrode plates 140-1, 140-2, 140-3... 140-N can be connected to the second conductive terminal 172 via conductive connectors 141. Thus, the plurality of capacitances formed by the plurality of first electrode plates 130-1, 130-2, 130-3... 130-N and the plurality of second electrode plates 140-1, 140-2, 140-3... 140-N can be connected in parallel with each other, and the total capacitance of the MEMS unit 100 can be regarded as the sum of these capacitances.

[0047] Figure 5 and Figure 6 respectively show a side view and a capacitance connection schematic diagram of the MEMS unit 100 without applying pressure P according to an embodiment of the present disclosure. As Figure 5 and Figure 6 shown, without applying pressure P, the total capacitance C a of the MEMS unit 100 can be expressed by the following equation:

[0048]

[0049] where C an is the capacitance value of the nth capacitance without applying pressure P, L is the plate length of the first electrode plate and the second electrode plate when observed in the first direction D1 (assuming the sizes of the first plate and the second plate are the same), W anis the overlapping width of the plates of the nth capacitor when observed in the second direction D2 without applying pressure P, and d is the distance between adjacent first and second electrode plates (assuming that all first and second electrode plates are evenly distributed and have the same spacing).

[0050] Figure 7 and Figure 8 respectively show a side view and a schematic diagram of the capacitor connection of the MEMS unit 100 under the application of pressure P according to an embodiment of the present disclosure. As Figure 7 and Figure 8 shown, when pressure P is applied, the total capacitance C of the MEMS unit 100 b can be expressed by the following equation:

[0051]

[0052] where C bn is the capacitance value of the nth capacitor when pressure P is applied, W bn is the overlapping width of the plates of the nth capacitor when observed in the second direction D2 under the application of pressure P, and the meanings of L and d are the same as those in equation (3) and will not be elaborated here.

[0053] Based on equations (3) and (4), the capacitance change value ΔC before and after the application of pressure P can be calculated v and is expressed as follows:

[0054]

[0055] It can be seen from equation (5) that the capacitance change value ΔC v is a function of pressure P. In other words, the capacitance change value ΔC v has a corresponding relationship with pressure P. Therefore, the pressure sensor 10 can determine the magnitude of pressure P by determining the capacitance change value ΔC v .

[0056] Figure 9 shows a top view of the MEMS unit 100 according to another embodiment of the present disclosure. Different from the MEMS unit 100 in Figure 3 and Figure 4 , Figure 3 and Figure 4 the bar-shaped first electrode plates 130-1, 130-2... 130-N in Figure 9 are replaced by the first electrode plates 130-1', 130-2'... 130-N' of another shape in Figure 9The second electrode plates 140-1’, 140-2’... 140-N’ of another shape in []. The replaced first electrode plates 130-1’, 130-2’... 130-N’ and the second electrode plates 140-1’, 140-2’... 140-N’ have a circular shape when observed in the first direction D1. Thus, the first electrode plates 130-1’, 130-2’... 130-N’ and the second electrode plates 140-1’, 140-2’... 140-N’ form a circular array arranged in a concentric and staggered manner. Alternatively, the first electrode plate and the second electrode plate may also have a square or rectangular shape, or a combination of more than one of the above shapes (such as strip and circular, or strip and square). When the first electrode plate and the second electrode plate are square or rectangular, the first electrode plate and the second electrode plate may form a square array or a rectangular array arranged in a concentric and staggered manner. Thus, the first electrode plate and the second electrode plate can be flexibly manufactured according to the situation to maximize the use of the space in the cavity, which helps to reduce the occupied area and volume of the pressure sensor and the MEMS unit and reduce the cost.

[0057] In an embodiment of the present disclosure, an improved pressure sensor MEMS structure is provided. This improved structure can effectively avoid the adverse effects of non-pressure factors in the external environment on pressure sensing, thereby improving the accuracy of sensing. In addition, in some embodiments, this improved structure can also improve the linearity of the pressure sensing results under different pressures, and helps to reduce the occupied area and volume of the sensor and its MEMS unit and reduce the manufacturing cost.

[0058] Through the above description and the teachings given in the related drawings, many modified forms and other embodiments of the present disclosure given here will be realized by those skilled in the art related to the present disclosure. Therefore, it is to be understood that the embodiments of the present disclosure are not limited to the specific embodiments disclosed, and the modified forms and other embodiments are intended to be included within the scope of the present disclosure. In addition, although the above description and the related drawings describe the exemplary embodiments in the context of certain example combinations of components and / or functions, it should be realized that different combinations of components and / or functions can be provided by alternative embodiments without departing from the scope of the present disclosure. In this regard, for example, other combinations of components and / or functions different from those clearly described above are also expected to be within the scope of the present disclosure. Although specific terms are used here, they are only used in a general and descriptive sense and are not intended to be limiting.

Claims

1. A microelectromechanical system (MEMS) unit (100), comprising: A housing, including a first wall portion (110) and a second wall portion (120) opposite to each other, and a cavity (180) located between the first wall portion (110) and the second wall portion (120), wherein the first wall portion (110) is adapted to deform in a first direction (D1) towards the second wall portion (120) under a pressure (P) from an external environment; At least one first electrode plate (130-1, 130-2, 130-3, 130-N), arranged to extend from the first wall portion (110) into the cavity (180), and adapted to be electrically connected to a first potential; And At least one second electrode plate (140-1, 140-2, 140-3, 140-N), arranged to extend from the second wall portion (120) into the cavity (180), and adapted to be electrically connected to a second potential different from the first potential, wherein the at least one second electrode plate (140-1, 140-2, 140-3, 140-N) is separated from the at least one first electrode plate (130-1, 130-2, 130-3, 130-N) in at least one of a second direction (D2) and a direction opposite to the second direction (D3) to form at least one capacitor, and the second direction (D2) intersects with the first direction (D1).

2. The MEMS unit (100) according to claim 1, wherein the second direction (D2) is perpendicular to the first direction (D1).

3. The MEMS unit (100) according to claim 1 or 2, wherein the at least one first electrode plate (130-1, 130-2, 130-3, 130-N) and the at least one second electrode plate (140-1, 140-2, 140-3, 140-N) are arranged to at least partially overlap in the second direction (D2).

4. The MEMS unit (100) according to claim 1 or 2, wherein the at least one first electrode plate (130-1, 130-2, 130-3, 130-N) comprises a plurality of first electrode plates (130-1, 130-2, 130-3, 130-N), and the at least one second electrode plate (140-1, 140-2, 140-3, 140-N) comprises a plurality of second electrode plates (140-1, 140-2, 140-3, 140-N).

5. The MEMS unit (100) according to claim 4, wherein the plurality of first electrode plates (130-1, 130-2, 130-3, 130-N) and the plurality of second electrode plates (140-1, 140-2, 140-3, 140-N) are arranged in an interleaved manner.

6. The MEMS unit (100) according to claim 4, further comprising: A first conductive terminal (171), electrically connected to the plurality of first electrode plates (130-1, 130-2, 130-3, 130-N); and A second conductive terminal (172), electrically connected to the plurality of second electrode plates (140-1, 140-2, 140-3, 140-N).

7. The MEMS unit (100) according to claim 1, wherein the housing is arranged to hermetically isolate the cavity (180) from the external environment.

8. The MEMS unit (100) according to claim 1, wherein the electrode plates of the at least one first electrode plate (130-1, 130-2, 130-3, 130-N) and the at least one second electrode plate (140-1, 140-2, 140-3, 140-N) have at least one of the following shapes when viewed in the first direction (D1): bar-shaped, circular, square, and rectangular.

9. A capacitive pressure sensor (10), comprising: The MEMS unit (100) according to any one of claims 1 to 8.

10. The capacitive pressure sensor (10) according to claim 9, further comprising: A processing unit (200), configured to determine the pressure (P) from an external environment based on the capacitance value of the MEMS unit (100).

11. The capacitive pressure sensor (10) according to claim 9, comprising a reference capacitor, the capacitance value of the reference capacitor being equal to the capacitance value of the MEMS unit when no pressure from the external environment is applied thereto.

12. The capacitive pressure sensor (10) according to claim 9, comprising a variable capacitor and at least two reference capacitors, wherein the variable capacitor, the at least two reference capacitors and the MEMS unit are connected in a Wheatstone bridge configuration.

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