CN115594145B

CN115594145B - Capacitive pressure sensor and manufacturing method thereof

Info

Publication number: CN115594145B
Application number: CN202211592331.XA
Authority: CN
Inventors: 吕萍
Original assignee: Memsensing Microsystems Suzhou China Co Ltd
Current assignee: Memsensing Microsystems Suzhou China Co Ltd
Priority date: 2022-12-13
Filing date: 2022-12-13
Publication date: 2023-05-09
Anticipated expiration: 2042-12-13
Also published as: CN115594145A

Abstract

The invention provides a capacitive pressure sensor and a manufacturing method thereof, aiming at solving the problems of overlarge packaging size and performance degradation of the capacitive pressure sensor caused by stress generated by difference of thermal expansion coefficients among multiple layers of materials of the traditional capacitive pressure sensor by manufacturing the capacitive pressure sensor on a substrate provided with a signal processing circuit structure. The manufacturing method of the reference capacitor of the capacitive pressure sensor is simple, and the capacitance value output by the reference capacitor can be maintained unchanged when pressure is applied.

Description

Capacitive pressure sensor and manufacturing method thereof

Technical Field

The invention relates to the technical field of sensors, in particular to a capacitive pressure sensor and a manufacturing method thereof.

Background

Capacitive pressure sensors of MEMS (Micro-electro-Mechanical Systems, microelectromechanical systems) technology, by detecting a capacitance change output signal between two plates, have a temperature drift far lower than that of piezoresistive pressure sensors, and therefore, in some applications (such as altimeters, unmanned aerial vehicles, etc.) where temperature stability is critical, capacitive pressure sensors are generally used.

The pressure sensor chip needs to be electrically connected with a signal processing circuit (also called an application specific integrated circuit (Application SpecificIntegrated Circuit, ASIC)) to form electric signal transmission, so as to realize signal processing on the pressure sensor chip, and further realize analog signal output, digital signal output and the like. In practical use, for a capacitive pressure sensor, one capacitive MEMS pressure chip and one ASIC chip need to be packaged. There are generally two packaging approaches: 1) The MEMS pressure chip and the ASIC chip are placed in parallel, the MEMS pressure chip and the ASIC chip are adhered to the substrate by the die bond adhesive and are interconnected by the wire bond, the packaging size is larger, and the material thermal expansion coefficients among the substrate, the die bond adhesive and the MEMS pressure chip are mismatched, so that the performance is influenced; 2) The MEMS pressure chip and the ASIC chip are stacked, the MEMS pressure chip is arranged on the ASIC chip, the MEMS pressure chip is bonded to the ASIC chip by adopting die bonding glue, and then the MEMS pressure chip is bonded to the ASIC chip through a lead, so that the requirement of the whole thickness is ensured, and the MEMS pressure chip is usually required to be thinned. Although the size of such packages can be made smaller, the fabrication process is more than the first, and as such, when the coefficients of thermal expansion are not uniform between the layers of material of the stacked package, stresses are easily induced and transferred to the MEMS, thereby affecting the performance output.

In view of the foregoing, there is a need to provide a novel capacitive pressure sensor and a manufacturing method thereof, so as to solve the problems of the existing capacitive pressure sensor that the package size is too large and the performance of the capacitive pressure sensor is degraded due to the stress generated by the difference of thermal expansion coefficients between the multiple layers of materials.

Disclosure of Invention

The invention aims to at least solve one of the technical problems in the prior art and provides a capacitive pressure sensor and a manufacturing method thereof.

The invention adopts the following technical scheme:

according to an aspect of the present invention, there is provided a method of manufacturing a capacitive pressure sensor, the method comprising: providing a substrate, wherein a signal processing circuit structure is arranged on the substrate; manufacturing at least one induction capacitance blank and at least one reference capacitance which are respectively and electrically connected with the signal processing circuit structure on one side surface of the substrate, wherein each induction capacitance blank and each reference capacitance comprise a lower polar plate, an upper polar plate and a cavity between the lower polar plate and the upper polar plate, and the cavity is filled with a dielectric body; and releasing the medium body in the cavity of each induction capacitance blank body to form a corresponding induction capacitance.

Further, the fabricating at least one induction capacitor blank and at least one reference capacitor on one side surface of the substrate, which are electrically connected to the signal processing circuit structure, respectively, includes:

manufacturing a first conductive layer on the surface of one side of the substrate, and performing patterned etching on the first conductive layer to respectively form a lower electrode plate of each induction capacitor blank, a first connecting body for interconnection with an upper electrode plate corresponding to each induction capacitor blank, and simultaneously form a second connecting body for interconnection with an upper electrode plate corresponding to each reference capacitor, and a plurality of conductive bonding pads, wherein the plurality of conductive bonding pads are electrically connected with corresponding ports of the signal processing circuit structure; manufacturing a sacrificial layer on the first conductive layer, and patterning the sacrificial layer to form dielectric bodies covering the lower electrode plate of each induction capacitor blank and the lower electrode plate of each reference capacitor respectively; manufacturing a second conductive layer on the sacrificial layer, so that the second conductive layer is electrically connected with a first connector corresponding to each induction capacitor blank and a second connector corresponding to each reference capacitor respectively, and sealing the sacrificial layer between the second conductive layer and the substrate; and patterning the second conductive layer to form each induction capacitor blank and the upper polar plate of each reference capacitor respectively, and etching partial areas of the upper polar plate of each induction capacitor blank to form release holes which are arranged at intervals on the corresponding sacrificial layer.

Further, the releasing only the dielectric body in the cavity of each induction capacitance blank to form a corresponding induction capacitance includes: removing dielectric bodies in the cavity of each induction capacitance blank by using a solution release method to form a corresponding induction capacitance; a sealing layer is fabricated on the second conductive layer to form a pressure sensing cavity between the second conductive layer and the first conductive layer.

Further, the manufacturing method further comprises the following steps: and before the sacrificial layer is manufactured on the first conductive layer, manufacturing a dielectric layer covering the first conductive layer on the first conductive layer.

Further, the fabricating a second conductive layer on the sacrificial layer, so that the second conductive layer is electrically connected to the first connector corresponding to each inductor-capacitor blank and the second connector corresponding to each reference capacitor, and seals the sacrificial layer between the second conductive layer and the substrate, including: a plurality of first through holes are formed in the sacrificial layer, and each first through hole penetrates through the sacrificial layer and the dielectric layer in the thickness direction so as to expose the first connector corresponding to each induction capacitor blank and the second connector corresponding to each reference capacitor respectively; and completely filling the second conductive layer into each first through hole so that the second conductive layer is electrically connected with the corresponding first connector and the corresponding second connector respectively.

Further, the fabricating a second conductive layer on the sacrificial layer, so that the second conductive layer is electrically connected to the first connector corresponding to each inductor-capacitor blank and the second connector corresponding to each reference capacitor, and seals the sacrificial layer between the second conductive layer and the substrate, including:

and forming a plurality of third through holes on the sacrificial layer, wherein each third through hole penetrates through the sacrificial layer and the dielectric layer in the thickness direction, each third through hole is annular and surrounds a dielectric layer column, the dielectric layer column comprises a part of the sacrificial layer and a part of the dielectric layer in the thickness direction, the dielectric layer column is completely filled and wrapped with a conductive medium through growth so as to form a conductive column wrapping the dielectric layer column, and the upper bottom surface and the lower bottom surface of each conductive column are respectively exposed from one side surface of the dielectric layer close to the substrate and one side surface of the sacrificial layer far from the substrate, so that the second conductive layer is respectively electrically connected with the first connector of the corresponding sensing capacitor and the second connector of the corresponding reference capacitor through each conductive column.

Optionally, the conductive medium comprises tungsten or titanium tungsten.

Further, the fabricating a second conductive layer on the sacrificial layer, so that the second conductive layer is electrically connected to the first connector corresponding to each inductor-capacitor blank and the second connector corresponding to each reference capacitor, and seals the sacrificial layer between the second conductive layer and the substrate, including: carrying out opening treatment on the dielectric layer to expose the first connector corresponding to each induction capacitor and the second connector corresponding to each reference capacitor; and manufacturing the second conductive layer on the sacrificial layer so that the second conductive layer is in direct contact with the first connecting body corresponding to each sensing capacitor and the second conductive layer is in direct contact with the second connecting body corresponding to each reference capacitor.

Further, the manufacturing method further comprises the following steps: and after the sealing layer is manufactured on the second conductive layer, a plurality of second through holes are formed in the dielectric layer and the sealing layer above the dielectric layer, and the second through holes penetrate through the dielectric layer and the sealing layer in the thickness direction so as to expose the conductive pads.

According to another aspect of the present invention, there is provided a capacitive pressure sensor comprising: a substrate on which a signal processing circuit is provided; the device comprises a substrate, at least one sensing capacitor and at least one reference capacitor, wherein the sensing capacitor and the at least one reference capacitor are positioned on one side surface of the substrate and are respectively and electrically connected with the signal processing circuit, each sensing capacitor and each reference capacitor comprise a lower polar plate, an upper polar plate and a cavity between the lower polar plate and the upper polar plate, the cavity of each sensing capacitor is a cavity without a filler, and a dielectric body is filled in the cavity of each reference capacitor.

The capacitive pressure sensor and the manufacturing method thereof provided by the embodiment of the invention aim to solve the problems of overlarge packaging size and performance degradation of the capacitive pressure sensor caused by stress generated by difference of thermal expansion coefficients among multiple layers of materials of the traditional capacitive pressure sensor by manufacturing the capacitive pressure sensor on the substrate provided with the signal processing circuit structure. The manufacturing method of the reference capacitor of the capacitive pressure sensor is simple, and the capacitance value output by the reference capacitor can be maintained unchanged when pressure is applied.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other embodiments may be obtained according to these drawings without inventive effort to a person skilled in the art.

FIG. 1 is a flow chart of a method of manufacturing a capacitive pressure sensor according to an embodiment of the invention.

Fig. 2A to fig. 2G are schematic views illustrating a manufacturing process of a manufacturing method of a capacitive pressure sensor according to an embodiment of the invention.

Fig. 3A to 3F are schematic views of a manufacturing process of a manufacturing method of a capacitive pressure sensor according to another embodiment of the present invention.

Fig. 4A to 4E are schematic views of a manufacturing process of a manufacturing method of a capacitive pressure sensor according to another embodiment of the present invention.

Fig. 5 is a block diagram of a circuit structure according to an embodiment of the present invention.

Fig. 6 is a block diagram of a circuit structure according to still another embodiment of the present invention.

Detailed Description

The foregoing description is only an overview of the present invention, and is intended to be implemented in accordance with the teachings of the present invention, as well as the preferred embodiments thereof, together with the following detailed description of the invention, given by way of illustration only, together with the accompanying drawings.

In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically connected, electrically connected or can be communicated with each other; can be directly connected or indirectly connected through an intermediate medium, and can be communicated with the inside of two elements or the interaction relationship of the two elements. The order illustrated herein represents one exemplary scenario when referring to method steps, but does not represent a limitation on the order. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.

The invention will be further described in detail with reference to the drawings and detailed description below in order to make the objects, features and advantages of the invention more comprehensible.

FIG. 1 is a flow chart of a method of manufacturing a capacitive pressure sensor according to an embodiment of the invention. The manufacturing method of the capacitive pressure sensor comprises the following steps:

s10, providing a substrate, wherein a signal processing circuit structure is arranged on the substrate;

S20, manufacturing at least one induction capacitor blank and at least one reference capacitor which are respectively and electrically connected with the signal processing circuit structure on one side surface of the substrate, wherein each induction capacitor blank and each reference capacitor comprises a lower polar plate, an upper polar plate and a cavity between the lower polar plate and the upper polar plate, and the cavity is filled with a dielectric body;

and S30, only releasing the medium body in the cavity of each induction capacitance blank body to form a corresponding induction capacitance.

Steps S10 to S30 will be specifically described below.

In step S10, a substrate is provided, where the substrate material may be silicon, or may be another material, such as gallium arsenide, silicon carbide, or the like. The substrate is provided with a signal processing circuit structure, namely an application specific integrated circuit ASIC, which refers to an integrated circuit designed and manufactured according to the requirements of specific users and the needs of specific electronic systems. For example, ASICs in capacitive pressure sensors are used to further process and transmit electrical signals generated by externally applied changes in pressure across the sensor to the next stage circuitry. Illustratively, in embodiments of the present invention, the signal processing circuitry may be embedded in the substrate, and in other embodiments, the signal processing circuitry may be located on a side surface of the substrate.

In step S20, at least one induction capacitor blank and at least one reference capacitor are fabricated on a surface of one side of the substrate, and each induction capacitor blank and each reference capacitor are respectively electrically connected with the signal processing circuit structure, wherein each induction capacitor blank and each reference capacitor comprises a lower polar plate, an upper polar plate, and a cavity between the lower polar plate and the upper polar plate, and the cavity is filled with a dielectric body. It should be noted that, the inductor capacitor blank refers to an intermediate process body that finally forms the inductor capacitor structure. For example, in order to save manufacturing process flow, the reference capacitor may be manufactured simultaneously with the manufacturing of the induction capacitor blank.

It should be understood that, in the embodiment of the present invention, the sensing capacitor refers to a capacitor whose capacitance varies with the action of the air pressure of the outside, and the reference capacitor refers to a capacitor whose capacitance does not vary with the action of the air pressure of the outside.

In step S30, only the dielectric body in the cavity of each induction capacitor blank is released to form a corresponding induction capacitor. That is, only the dielectric body in the cavity of each induction capacitor blank is removed through a release process to form the induction capacitor with a corresponding cavity structure. The medium body in the cavity of each reference capacitor is not required to be released, the cavity of each reference capacitor is still filled with the medium body, and the structure is a solid structure, when the external air pressure acts, the upper polar plate of each reference capacitor cannot deform due to the supporting effect of the medium body in the cavity of each reference capacitor, so that the distance (gap) between the upper polar plate and the lower polar plate of each reference capacitor cannot change, and therefore, the size of each reference capacitor is basically fixed.

Example 1

Embodiments of the present invention will be described in detail below with reference to fig. 2A to 2G.

Referring to fig. 2A, first, a substrate 100 is provided, and the substrate 100 is provided with a dedicated signal processing circuit structure (not shown), which is illustratively embedded in the substrate 100, and a first conductive layer 110 is formed on one side surface of the substrate 100, and the first conductive layer 110 is made of a metal conductive material, such as aluminum, tungsten, or silicon tungsten. The first conductive layer 110 is etched to form a first lower plate 112 of each of the induction capacitor blanks 161, a first connector 113 for interconnection with a first upper plate corresponding to each of the induction capacitor blanks 161, and simultaneously form a second lower plate 115 of each of the reference capacitors 170, a second connector 114 for interconnection with a second upper plate corresponding to each of the reference capacitors 170, and a plurality of conductive pads 117, wherein the plurality of conductive pads 117 are electrically connected with corresponding ports of the signal processing circuit structure (not shown) for transmitting electrical signals to external electronic devices.

In the embodiment of the present invention, by fabricating the first conductive layer 110 and using the first conductive layer 110, both the output terminal serving as the signal processing circuit structure and the first lower electrode plate 112 serving as each of the induction capacitor blanks 161 and the first connecting body 113 for interconnecting the first upper electrode plate corresponding to each of the induction capacitor blanks 161 are formed, and simultaneously the second lower electrode plate 115 serving as each of the reference capacitors 170 and the second connecting body 114 for interconnecting the second upper electrode plate corresponding to each of the reference capacitors are formed, thereby facilitating the overall thinning of the capacitive pressure sensor package structure.

Optionally, with continued reference to fig. 2B, a dielectric layer 120 is fabricated on the first conductive layer 110 that covers the first conductive layer 110. The dielectric layer 120 is typically a material such as silicon nitride or silicon-rich silicon nitride, and may serve as a protective layer to protect the first conductive layer 110 from being corroded by moisture in the environment, and may serve as a subsequent etch stop layer to protect the first conductive layer 110 from being etched.

With continued reference to fig. 2C, a sacrificial layer 130 is fabricated on the dielectric layer 120 using a low temperature process, and the sacrificial layer 130 is patterned to form a first dielectric body 131 covering the first bottom plate 112 of each of the inductor capacitor blanks 161 and a second dielectric body 132 covering the second bottom plate 115 of each of the reference capacitors 170, respectively. Alternatively, the material of the sacrificial layer 130 may be germanium or germanium-silicon, and is grown by low-temperature chemical vapor deposition at a process temperature of 400 ℃. Alternatively, the material of the sacrificial layer 130 may be aluminum, and the material is sputtered by a magnetron sputtering device. Alternatively, the material of the sacrificial layer 130 may be silicon oxide, which is grown by vapor deposition using plasma enhanced chemistry.

Illustratively, the sacrificial layer 130 is etched to etch a plurality of first through holes 26 while forming the first dielectric body 131 covering the first lower plate 112 of each of the inductor-capacitor blanks 161 and the second dielectric body 132 covering the second lower plate 115 of each of the reference capacitors 170, and each of the first through holes 26 penetrates through the sacrificial layer 130 and the dielectric layer 120 in the thickness direction to expose the first connection body 113 corresponding to each of the inductor-capacitor blanks 161 and the second connection body 114 corresponding to each of the reference capacitors 170, respectively.

With continued reference to fig. 2D, a second conductive layer 140 is formed on the sacrificial layer 130, where the second conductive layer 140 may be a single conductive layer or a composite conductive layer, such as silicon tungsten, titanium nitride, tungsten, titanium, or a composite layer containing the above materials. Preferably, the second conductive layer 140 is a composite conductive layer that facilitates stress matching between the second conductive layer 140 and the sacrificial layer 130.

Illustratively, the second conductive layer 140 may be grown on the sacrificial layer 130 by a thin film deposition process to completely fill the second conductive layer 140 into each of the first through holes 26, so that the second conductive layer 140 is electrically connected with the first connection 113 corresponding to each of the sense capacitor blanks 161 and the second connection 114 corresponding to each of the reference capacitors 170, respectively, and the sacrificial layer 130 is sealed between the second conductive layer 140 and the substrate 100 by completely filling the second conductive layer 140 into each of the first through holes 26, that is, the first dielectric body 131 corresponding to each of the sense capacitor blanks 161 is sealed between the second conductive layer 140 and the substrate 100, and the second dielectric body 132 corresponding to each of the reference capacitors 161 is sealed between the second conductive layer 140 and the substrate 100, so as to form the first cavity 35 corresponding to each of the sense capacitor blanks and the second cavity 36 corresponding to each of the reference capacitors 170, respectively.

With continued reference to fig. 2E, the second conductive layer 140 is then patterned to form a first upper plate 141 of each of the inductor-capacitor blanks 161 and a second upper plate 142 of each of the reference capacitors 170, respectively, and a partial region of the first upper plate 141 of each of the inductor-capacitor blanks 161 is etched to form release holes 44 arranged at intervals above the corresponding sacrificial layer 130.

Specifically, release holes 44 are formed on the second conductive layer 140 above the corresponding first dielectric body 131 at intervals. The projection pattern of each of the release holes 44 may be circular, square, elongated, etc. in the thickness direction of the substrate 100, and a plurality of release holes 44 may be arranged in an array.

Illustratively, the second conductive layer 140 is etched over the first, second, and

third regions

31, 32, 33 while patterning the second conductive layer 140 to expose the second sub-portion 134 of the sacrificial layer between the first upper plate 141 corresponding to each of the sensing capacitor blanks 161 and the second upper plate 142 corresponding to each of the reference capacitors 170, the first sub-portion 133 of the sacrificial layer exposing the periphery of each of the sensing capacitor blanks, and the third sub-portion 135 of the sacrificial layer exposing the periphery of each of the reference capacitors.

With continued reference to fig. 2E-2F, in the embodiment of the present invention, only a partial area of the first upper electrode plate 141 of each of the induction capacitor blanks 161 is etched to form release holes 44 arranged at intervals above the corresponding sacrificial layer 130, and the first dielectric body 131 in the first cavity 35 of each of the induction capacitor blanks 161 is removed by a solution release method to form a pressure sensing cavity of the corresponding induction capacitor 160. And the second upper plate 142 corresponding to each reference capacitor 170 is not etched to form a release hole, so that the second dielectric 132 in the second cavity 36 of each reference capacitor 170 is maintained during the subsequent release of the sacrificial layer 130. That is, the second cavity 36 of each reference capacitor 170 is still filled with the second dielectric body 132, and is a solid structure, and when the external air pressure acts, the second upper plate 142 of each reference capacitor 170 is not deformed due to the supporting effect of the second dielectric body 132 in the second cavity 36 of the reference capacitor 170, so the distance (gap) between the second upper plate 142 and the second lower plate 115 of each reference capacitor 170 is not changed, and thus the size of each reference capacitor 170 is substantially unchanged.

The first dielectric body 131 in the first cavity 35 of each of the inductor-capacitor blanks is removed by a solution release method to form the corresponding inductor capacitor 160, and the first sub-portion 133 of the sacrificial layer located above the first region 31, the second sub-portion 134 of the sacrificial layer located above the second region 32, and the third sub-portion 135 of the sacrificial layer located above the third region 33 may be etched away to expose a portion of the dielectric layer 120 located above the first region 31, the second region 32, and the third region 33.

Alternatively, if the material of the sacrificial layer 130 is germanium or germanium-silicon, a mixed solution containing hydrogen peroxide and hydrochloric acid or a mixed solution of phosphoric acid and nitric acid may be introduced into the release hole 44 for release. Alternatively, if the material of the sacrificial layer 130 is aluminum, a solution containing phosphoric acid may be used to enter the release holes 44 for release. Alternatively, if the material of the sacrificial layer 130 is silicon oxide, a solution of VHF may be used to enter the release holes 44 for release.

With continued reference to fig. 2G, a full-face sealing layer 150 is formed on the second conductive layer 140, and the sealing layer 150 may be made of silicon nitride or silicon-rich silicon nitride. Specifically, a sealing layer 150 is deposited on the entire surface of the side of the second conductive layer 140 facing away from the substrate 100, so as to seal the pressure sensing cavity of the sensing capacitor 160 and the reference capacitor 170, thereby forming a sealed pressure sensing cavity between the second conductive layer 140 and the first conductive layer 110. Ideally, the air pressure of the sensing capacitor 160 remains unchanged, and the size of the sensing capacitor 160 is determined by the distance between the upper and lower plates and the dielectric constant of the medium between the upper and lower plates. However, since the first dielectric body 131 in the first cavity 35 of the sensing capacitor is completely removed by the solution discharge method, the cavity formed is equivalent to air having a dielectric constant of 1, and thus the capacitance value of the sensing capacitor is determined by the distance between the upper and lower plates. The sensing capacitor senses a change in air pressure or the like caused by an external environment through the deformation of the first upper plate 141. When the air pressure in the external environment changes, the first upper plate 141 of the sensing capacitor will generate a tiny displacement deformation, and the tiny displacement deformation will cause the capacitance value of the sensing capacitor to change to a certain extent, so as to generate a detection signal for detecting the external environment pressure.

Further, after the sealing layer 150 is fabricated on the second conductive layer 140, a plurality of second through holes 56 are disposed on the dielectric layer 120 and the sealing layer 150 above the dielectric layer 120, and the plurality of second through holes 56 penetrate through the dielectric layer 120 and the sealing layer 150 in the thickness direction so as to expose the plurality of conductive pads 117.

Example two

Referring to fig. 3A, after the first conductive layer 110 and the dielectric layer 120 are formed on the substrate 100, a sacrificial layer 130 is formed on the dielectric layer 120 by using a low temperature process, and the material of the sacrificial layer 130 may be germanium or silicon germanium, for example, by using low temperature chemical vapor deposition at a process temperature of 400 ℃. Alternatively, the material of the sacrificial layer 130 may be aluminum, and the material is sputtered by a magnetron sputtering device. Alternatively, the material of the sacrificial layer 130 may be silicon oxide, which is grown by vapor deposition using plasma enhanced chemistry.

The sacrificial layer 130 is patterned to form a first dielectric body 131 covering the first bottom plate 112 of each of the sensing capacitor blanks 161 and a second dielectric body 132 covering the second bottom plate 115 of each of the reference capacitors 170, respectively. And etching the sacrificial layer 130 for a region other than the first bottom plate 112 covering each of the inductor-capacitor blanks 161 and the second bottom plate 115 covering each of the reference capacitors 170 to etch a plurality of third through holes 49A, wherein in this embodiment, each of the third through holes 49A is annular and surrounds a dielectric layer post 49B, and the dielectric layer post 49B includes the dielectric layer 120 and the sacrificial layer 130. Each of the third through holes 49A penetrates through the sacrificial layer 130 and the dielectric layer 120 in the thickness direction to expose a portion of the surface of the first connector 113 corresponding to each of the inductor-capacitor blanks 161 and a portion of the surface of the second connector 114 corresponding to each of the reference capacitors 170, respectively.

With continued reference to fig. 3B, the conductive pillars 49B are formed by growing a conductive medium 50A to completely fill and encapsulate the dielectric layer pillars 49B with a plurality of third vias 49A. Wherein the conductive medium 50A is tungsten or titanium tungsten, which is compatible with integrated circuit processes and which reduces differences in thermal expansion coefficients between the different materials. The upper and lower bottom surfaces of each conductive pillar are respectively exposed from a side surface of the dielectric layer 120 close to the substrate 100 and from a side surface of the sacrificial layer 130 far from the substrate 100, so that the second conductive layer 140 is respectively electrically connected to the first connector 113 of the corresponding sensing capacitor 160 and to the second connector 114 of the corresponding reference capacitor 170 through each conductive pillar.

With continued reference to fig. 3C, a second conductive layer 140 is formed on the sacrificial layer 130, where the second conductive layer 140 may be a single conductive layer or a composite conductive layer, such as silicon tungsten, titanium nitride, tungsten, titanium, or a composite layer containing the above materials. Preferably, the second conductive layer 140 is a composite conductive layer that facilitates stress matching between the second conductive layer 140 and the sacrificial layer 130.

Illustratively, the second conductive layer 140 may be grown on the sacrificial layer 130 by a thin film deposition process, where the second conductive layer 140 is in direct contact with the conductive medium 50A and the dielectric layer post 49B, the second conductive layer 140 is electrically connected to the first connection 113 corresponding to each of the induction capacitor blanks 161 and the second connection 114 corresponding to each of the reference capacitors 170 respectively by the conductive medium 50A located in the third through hole 49A, and the second conductive layer 140 is completely filled into each of the third through holes 49A to seal the sacrificial layer 130 between the second conductive layer 140 and the substrate 100, that is, seal the first dielectric body 131 corresponding to each of the induction capacitor blanks 161 between the second conductive layer 140 and the substrate 100, and seal the second dielectric body 132 corresponding to each of the reference capacitors between the second conductive layer 140 and the substrate 100, and form each of the third cavities 53B corresponding to each of the induction capacitors 161 and the fourth cavities 53B.

In this embodiment, a plurality of annular third through holes 49A are formed in the sacrificial layer 130, the third through holes 49A surround the dielectric layer pillars 49B, and the conductive medium 50A is filled in the plurality of third through holes 49A, so that the conductive medium 50A wraps the dielectric layer pillars 49B, thereby forming conductive pillars wrapping the dielectric layer pillars 49B. A second conductive layer 140 is then formed over the sacrificial layer 130 that can be planarized to overlie the third via 49A filled with conductive medium 50A. Compared to the solution of the first embodiment, since the second conductive layer 140 does not need to be buried in the third via hole 49A to form an electrical connection structure, not only the film thickness of the second conductive layer 140 can be saved, but also the reliability of electrical connection between the second conductive layer 140 and the first connection body 113 corresponding to each of the sensing capacitor blanks 161 and the second connection body 114 corresponding to each of the reference capacitors 170 can be improved.

With continued reference to fig. 3D, the second conductive layer 140 is then patterned to form a first upper plate 141 of each of the inductor-capacitor blanks 161 and a second upper plate 142 of each of the reference capacitors 170, respectively, and a partial region of the first upper plate 141 of each of the inductor-capacitor blanks 161 is etched to form release holes 44 arranged at intervals above the corresponding sacrificial layer 130.

Specifically, release holes 44 are formed on the corresponding first dielectric body 131 at intervals. The projection pattern of each of the release holes 44 may be circular, square, elongated, etc. in the thickness direction of the substrate 100, and a plurality of release holes 44 may be arranged in an array. And will not be described in detail herein.

third regions

31, 32, 33 while patterning the second conductive layer 140 to expose the second sub-portion 134 of the sacrificial layer between the first upper plate 141 corresponding to each of the sensing capacitor blanks 161 and the second upper plate 142 corresponding to each of the reference capacitors 170, the first sub-portion 133 of the sacrificial layer exposing the periphery of each of the sensing capacitor blanks 161, and the third sub-portion 135 of the sacrificial layer exposing the periphery of each of the reference capacitors.

With continued reference to fig. 3E-3F, in the embodiment of the present invention, only a partial area of the first upper electrode plate 141 of each of the induction capacitor blanks 161 is etched to form release holes 44 arranged at intervals above the corresponding sacrificial layer 130, and the first dielectric body 131 in the third cavity 53A of each of the induction capacitor blanks 161 is removed by a solution release method to form a pressure sensing cavity of the corresponding induction capacitor 160. And the second upper plate 142 corresponding to each reference capacitor 170 is not etched to form a release hole, so that the second dielectric body 132 in the fourth cavity 53B of each reference capacitor 170 is maintained during the subsequent release of the sacrificial layer 130. That is, the fourth cavity 53B of each reference capacitor 170 is still filled with the second dielectric body 132, and is a solid structure, and when the external air pressure acts, the second upper plate 142 of each reference capacitor 170 is not deformed due to the supporting effect of the second dielectric body 132 in the fourth cavity 53B of the reference capacitor 170, so the distance (gap) between the second upper plate 142 and the second lower plate 115 of each reference capacitor 170 is not changed, and thus the size of each reference capacitor 170 is substantially constant.

The first dielectric body 131 in the third cavity 53A of each of the inductor-capacitor blanks is removed by a solution release method to form a corresponding inductor capacitor, and a part of the sacrificial layer above the first region 31, the second region 32 and the third region 33 may be etched away to expose a part of the dielectric layer 120 above the first region 31, the second region 32 and the third region 33.

With continued reference to fig. 3F, a sealing layer 150 is formed on the second conductive layer 140, where the sealing layer 150 may be made of silicon nitride or silicon-rich silicon nitride. Specifically, a sealing layer 150 is deposited on the entire surface of the side of the second conductive layer 140 facing away from the substrate 100, so as to seal the pressure sensing cavity of the sensing capacitor 160 and the reference capacitor 170, thereby forming a sealed pressure sensing cavity between the second conductive layer 140 and the first conductive layer 110.

Example III

Referring to fig. 4A, after the first conductive layer 110 and the dielectric layer 120 are formed on the substrate 100, a sacrificial layer 130 is formed on the dielectric layer 120 by a low temperature process, and the sacrificial layer 130 is patterned to form a first dielectric body 131 covering only the first bottom plate 112 of each of the sensing capacitor blanks 161 and a second dielectric body 132 covering the second bottom plate 115 of each of the reference capacitors 170, respectively.

With continued reference to fig. 4B, in this embodiment, the dielectric layer 120 is subjected to an opening process to expose the first connection body corresponding to each of the sensing capacitors 160 and the second connection body corresponding to each of the reference capacitors 170; a second conductive layer 140 is fabricated on the sacrificial layer 130 such that the second conductive layer 140 is in direct contact with the first connection body corresponding to each of the sensing capacitors 160 and the second conductive layer 140 is in direct contact with the second connection body corresponding to each of the reference capacitors 170. So that the second conductive layer 140 is electrically connected to the first connector corresponding to each of the induction capacitor blanks 161 and the second connector corresponding to each of the reference capacitors 170, and the sacrificial layer 130 is sealed between the second conductive layer 140 and the substrate 100, so as to form a fifth cavity 55A corresponding to each of the induction capacitor blanks 161 and a sixth cavity 55B corresponding to each of the reference capacitors 170, respectively.

With continued reference to fig. 4C, the second conductive layer 140 is patterned to form the first upper plate 141 of each of the inductor-capacitor blanks 161 and the second upper plate 142 of each of the reference capacitors 170, and a partial region of the first upper plate 141 of each of the inductor-capacitor blanks 161 is etched to form release holes 44 arranged at intervals over a corresponding portion of the sacrificial layer 130.

third regions

With continued reference to fig. 4D, in an embodiment of the present invention, only a partial area of the first upper electrode plate 141 of each of the inductor-capacitor blanks 161 is etched to form release holes 44 arranged at intervals over a corresponding portion of the sacrificial layer 130, and the first dielectric body 131 in the fifth cavity 55A of each of the inductor-capacitor blanks 161 is removed by a solution release method to form a pressure sensing cavity of the corresponding inductor-capacitor 160. And the second upper plate 142 corresponding to each reference capacitor 170 is not etched to form a release hole, so that the second dielectric body 132 in the sixth cavity 55B of each reference capacitor 170 is retained during the subsequent release of the sacrificial layer 130. That is, the sixth cavity 55B of each reference capacitor 170 is still filled with the second dielectric body 132, and is a solid structure, and when the external air pressure acts, the second upper plate 142 of each reference capacitor 170 is not deformed due to the supporting action of the second dielectric body 132 in the sixth cavity 55B of each reference capacitor 170, so the distance (gap) between the second upper plate 142 and the second lower plate 115 of each reference capacitor 170 is not changed, and thus the size of each reference capacitor 170 is substantially constant.

The first dielectric body 131 in the fifth cavity 55A of each of the inductor-capacitor blanks is removed by a solution release method to form the corresponding inductor capacitor 160, and a part of the sacrificial layer above the first region 31, the second region 32 and the third region 33 may be etched away to expose a part of the dielectric layer 120 above the first region 31, the second region 32 and the third region 33.

With continued reference to fig. 4E, a full-face sealing layer 150 is formed on the second conductive layer 140, and the sealing layer 150 may be made of silicon nitride or silicon-rich silicon nitride. Specifically, a sealing layer 150 is deposited on the entire surface of the side of the second conductive layer 140 facing away from the substrate 100, so as to seal the pressure sensing cavity of the sensing capacitor 160 and the reference capacitor 170, thereby forming a sealed pressure sensing cavity between the second conductive layer 140 and the first conductive layer 110.

In comparison with the solutions of the first and second embodiments, in this embodiment, the sacrificial layer 130 and the dielectric layer 120 are fabricated to have a stepped structure in advance, and the dielectric layer 120 is perforated to expose the first connector 113 corresponding to each of the inductor-capacitor blanks 161 and the second connector 114 corresponding to each of the reference capacitors 170, so that the second conductive layer 140 fabricated later is electrically connected to the first connector 113 corresponding to each of the inductor-capacitor blanks 161 and the second connector 114 corresponding to each of the reference capacitors 170, respectively, and the sacrificial layer 130 is sealed between the second conductive layer 140 and the substrate 100. The sacrificial layer and the insulating layer do not need to be electrically connected in an opening mode, so that the manufacturing method is simpler in procedure, and the cost of the manufacturing process is correspondingly saved.

According to yet another aspect of the present invention, a capacitive pressure sensor is provided.

Illustratively, as shown in FIG. 2G, there is provided a capacitive pressure sensor comprising: a substrate 100, on which substrate 100 a signal processing circuit (not shown) is provided; at least one sensing capacitor 160 and at least one reference capacitor 170, wherein the at least one sensing capacitor 160 and the at least one reference capacitor 170 are located on a side surface of the substrate 100 and are respectively electrically connected with the signal processing circuit, and each sensing capacitor 160 and each reference capacitor 170 comprises a lower polar plate, an upper polar plate, and a cavity between the lower polar plate and the upper polar plate, wherein the cavity of each sensing capacitor 160 is a cavity without a filler, and the cavity of each reference capacitor 170 is filled with a dielectric body.

For ease of understanding and description, the lower plate corresponding to each of the sensing capacitors 160 is referred to as a first lower plate 112, the upper plate corresponding to each of the sensing capacitors 160 is referred to as a first upper plate 141, the lower plate corresponding to each of the reference capacitors 170 is referred to as a second lower plate 115, and the upper plate corresponding to each of the sensing capacitors 160 is referred to as a second upper plate 142.

The substrate material 100 may be silicon, or may be other materials, such as gallium arsenide, silicon carbide, and the like. The substrate 100 is provided with a signal processing circuit, i.e. an application specific integrated circuit ASIC, which refers to an integrated circuit designed and manufactured to meet the requirements of a specific user and the needs of a specific electronic system. For example, ASICs in capacitive pressure sensors are used to further process and transmit electrical signals generated by externally applied pressure changes to the next stage circuitry. Illustratively, in embodiments of the present invention, the signal processing circuitry may be embedded in the substrate 100, and in other embodiments, the signal processing circuitry may be located on a side surface of the substrate 100.

Illustratively, as shown in fig. 2A-2G, the second conductive layer 140 is filled into the first through hole 26 penetrating the sacrificial layer 130 and the dielectric layer 120, so that the second conductive layer 140 is electrically connected with the first connector 113 corresponding to each of the sensing capacitor blanks 161 and the second connector 114 corresponding to each of the reference capacitors 170, and the sacrificial layer 130 is sealed between the second conductive layer 140 and the substrate 100, thereby forming the first cavity 35 corresponding to each of the sensing capacitors 160, the first dielectric body 131 filled into the first cavity 35, the second cavity 36 corresponding to each of the reference capacitors 170, and the second dielectric body 132 filled into the second cavity 36, respectively.

Further, the second dielectric body 132 filled in the second cavity 36 of each reference capacitor 170 is a solid structure, and when the air pressure acts on the outside, the second upper plate 142 of each reference capacitor 170 will not deform due to the supporting action of the second dielectric body 132 in the second cavity 36 of the reference capacitor 170, so the distance (gap) between the second upper plate 142 and the second lower plate 115 of each reference capacitor 170 will not change, and therefore, the size of each reference capacitor 170 will not change.

In some embodiments, as shown in fig. 3A-3F, a dielectric layer pillar 49B is disposed in the third via 49A, and an electrical connection structure surrounding the dielectric layer pillar 49B is formed by filling a conductive medium 50A into the third via 49A penetrating the sacrificial layer 130 and the dielectric layer 120, and then the second conductive layer 140 is contacted with the electrical connection structure, so that the second conductive layer 140 is electrically connected with the first connector 113 corresponding to each of the induction capacitor blanks 161 and the second connector 114 corresponding to each of the reference capacitors 170, respectively, and the sacrificial layer 130 is sealed between the second conductive layer 140 and the substrate 100, thereby forming a third cavity 53A corresponding to each of the induction capacitors 160, and a fourth cavity 53B corresponding to each of the reference capacitors 170 and a second dielectric 132 filled into the fourth cavity 53B, respectively.

Further, the fourth cavity 53B of each reference capacitor 170 is filled with the second dielectric body 132, which is a solid structure, and when the air pressure of the outside acts, the second upper plate 142 of each reference capacitor 170 is not deformed due to the supporting effect of the second dielectric body 132 in the fourth cavity 53B of the reference capacitor 170, so that the distance (gap) between the second upper plate 142 and the second lower plate 115 of each reference capacitor 170 is not changed, and therefore, the size of each reference capacitor 170 is substantially unchanged.

Illustratively, as shown in fig. 4A to 4E, the sacrificial layer 130 is disposed on the dielectric layer 120, and the sacrificial layer 130 and the dielectric layer 120 are formed to have a step structure, and the dielectric layer 120 is perforated to expose the first connector 113 corresponding to each of the inductor-capacitor blanks 161 and the second connector 114 corresponding to each of the reference capacitors 170, so that the second conductive layer 140 is electrically connected to the first connector 113 corresponding to each of the inductor-capacitor blanks 161 and the second connector 114 corresponding to each of the reference capacitors 170, respectively, and the sacrificial layer 130 is sealed between the second conductive layer 140 and the substrate 100.

Further, the second dielectric body 132 filled in the sixth cavity 55B of each reference capacitor 170 is a solid structure, and when the air pressure of the outside acts, the upper electrode plate 142 of each reference capacitor 170 will not deform due to the supporting effect of the second dielectric body 132 in the sixth cavity 55B of each reference capacitor 170, so the distance (gap) between the upper electrode plate 142 and the lower electrode plate 115 of each reference capacitor 170 will not change, and therefore, the size of each reference capacitor 170 will not change.

Fig. 5 is a block diagram of a circuit structure according to an embodiment of the present invention, and fig. 6 is a block diagram of a circuit structure according to another embodiment of the present invention.

As shown in fig. 5, the first pressure sensor 102 includes a first pressure sensing chip 101B, an application specific integrated circuit chip (ASIC) 10, and an output interface 40. The first pressure sensing chip 101B is a MEMS capacitive pressure sensor. The first pressure sensor chip 101B is formed by electrically connecting 1 variable capacitor (sensing capacitor) 160 and a reference capacitor 170 to form a half-bridge, and is labeled Cs and Cr. When the external air pressure changes, the sensitive film (upper polar plate) of the variable capacitor (sensing capacitor) 160 changes, the variable capacitor Cs changes, the capacitance of the reference capacitor 170 does not change, and the output capacitance signal passes through the ASIC reading circuit, so that the pressure value in the current environment is output.

As shown in fig. 6, the second pressure sensor 104 includes a second pressure sensing chip 101C, an application specific integrated circuit chip (ASIC) 10, and an output interface 40. The second pressure sensing chip 101C is a MEMS capacitive sensor. The second pressure sensor chip 101C is formed by connecting a pair of variable capacitors (sensing capacitors) 160 and a pair of reference capacitors 170 to form a wheatstone bridge, labeled Cs and Cr, respectively. When the external air pressure changes, the sensitive film (upper polar plate) of the variable capacitor (sensing capacitor) 160 changes, the variable capacitor (sensing capacitor) Cs changes, the reference capacitor 170 does not change, and the differential output capacitor signal passes through the ASIC readout circuit, so as to output the pressure value in the current environment.

Therefore, the capacitive pressure sensor and the manufacturing method thereof provided by the embodiment of the invention aim to solve the problems of overlarge packaging size of the traditional capacitive pressure sensor and performance degradation of the capacitive pressure sensor caused by stress generated by difference of thermal expansion coefficients among multiple layers of materials by manufacturing the capacitive pressure sensor on the substrate provided with the signal processing circuit structure. The manufacturing method of the reference capacitor of the capacitive pressure sensor is simple, and the capacitance value output by the reference capacitor can be maintained unchanged when pressure is applied.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of manufacturing a capacitive pressure sensor, the method comprising:

providing a substrate, wherein a signal processing circuit structure is arranged on the substrate;

manufacturing at least one induction capacitance blank and at least one reference capacitance which are respectively and electrically connected with the signal processing circuit structure on one side surface of the substrate, wherein each induction capacitance blank and each reference capacitance comprise a lower polar plate, an upper polar plate and a cavity between the lower polar plate and the upper polar plate, and the cavity is filled with a dielectric body;

releasing only the medium body in the cavity of each induction capacitance embryo body to form a corresponding induction capacitance, wherein the medium body filled in the cavity of each reference capacitance embryo body is not released to form a corresponding reference capacitance;

Wherein the dielectric body is made of one of germanium, germanium-silicon and aluminum.

2. The method of manufacturing a capacitive pressure sensor of claim 1, wherein said manufacturing at least one sensing capacitor blank and at least one reference capacitor on a side surface of said substrate, each electrically connected to said signal processing circuit structure, comprises:

manufacturing a first conductive layer on the surface of one side of the substrate, and performing patterned etching on the first conductive layer to respectively form a lower electrode plate of each induction capacitance blank, a first connecting body for interconnection with the upper electrode plate corresponding to each induction capacitance blank, and simultaneously form a lower electrode plate of each reference capacitance, a second connecting body for interconnection with the upper electrode plate corresponding to each reference capacitance, and a plurality of conductive bonding pads, wherein the plurality of conductive bonding pads are electrically connected with corresponding ports of the signal processing circuit structure;

manufacturing a sacrificial layer on the first conductive layer, and patterning the sacrificial layer to form dielectric bodies covering the lower electrode plate of each induction capacitor blank and the lower electrode plate of each reference capacitor respectively;

Manufacturing a second conductive layer on the sacrificial layer, so that the second conductive layer is electrically connected with a first connector corresponding to each induction capacitor blank and a second connector corresponding to each reference capacitor respectively, and sealing the sacrificial layer between the second conductive layer and the substrate;

and patterning the second conductive layer to form each induction capacitor blank and the upper polar plate of each reference capacitor respectively, and etching partial areas of the upper polar plate of each induction capacitor blank to form release holes which are arranged at intervals on the corresponding sacrificial layer.

3. The method of manufacturing a capacitive pressure sensor of claim 2, wherein releasing only the dielectric body within the cavity of each of the inductive capacitance blanks to form a corresponding inductive capacitance comprises:

removing dielectric bodies in the cavity of each induction capacitance blank by using a solution release method to form a corresponding induction capacitance;

a sealing layer is fabricated on the second conductive layer to form a pressure sensing cavity between the second conductive layer and the first conductive layer.

4. The method of manufacturing a capacitive pressure sensor of claim 2, further comprising:

And before the sacrificial layer is manufactured on the first conductive layer, manufacturing a dielectric layer covering the first conductive layer on the first conductive layer.

5. The method of manufacturing a capacitive pressure sensor of claim 4, wherein manufacturing a second conductive layer on the sacrificial layer such that the second conductive layer is electrically connected to the first connector corresponding to each of the sense capacitance blanks and the second connector corresponding to each of the reference capacitances, respectively, and sealing the sacrificial layer between the second conductive layer and the substrate, comprises:

manufacturing a plurality of first through holes on the sacrificial layer, wherein each first through hole penetrates through the sacrificial layer and the dielectric layer in the thickness direction so as to expose the first connector corresponding to each induction capacitor blank and the second connector corresponding to each reference capacitor respectively;

and completely filling the second conductive layer into each first through hole so that the second conductive layer is electrically connected with the corresponding first connector and the corresponding second connector respectively.

6. The method of manufacturing a capacitive pressure sensor of claim 4, wherein manufacturing a second conductive layer on the sacrificial layer such that the second conductive layer is electrically connected to the first connector corresponding to each of the sense capacitance blanks and the second connector corresponding to each of the reference capacitances, respectively, and sealing the sacrificial layer between the second conductive layer and the substrate, comprises: and forming a plurality of third through holes on the sacrificial layer, wherein each third through hole penetrates through the sacrificial layer and the dielectric layer in the thickness direction, each third through hole is annular and surrounds a dielectric layer column, the dielectric layer column comprises a part of the sacrificial layer and a part of the dielectric layer in the thickness direction, the dielectric layer column is completely filled and wrapped with a conductive medium through growth so as to form a conductive column wrapping the dielectric layer column, and the upper bottom surface and the lower bottom surface of each conductive column are respectively exposed from one side surface of the dielectric layer close to the substrate and one side surface of the sacrificial layer far from the substrate, so that the second conductive layer is respectively electrically connected with the first connector of the corresponding sensing capacitor and the second connector of the corresponding reference capacitor through each conductive column.

7. The method of manufacturing a capacitive pressure sensor according to claim 6, wherein,

the conductive medium comprises tungsten or titanium tungsten.

8. The method of manufacturing a capacitive pressure sensor of claim 4, wherein manufacturing a second conductive layer on the sacrificial layer such that the second conductive layer is electrically connected to the first connector corresponding to each of the sense capacitance blanks and the second connector corresponding to each of the reference capacitances, respectively, and sealing the sacrificial layer between the second conductive layer and the substrate, comprises:

carrying out opening treatment on the dielectric layer to expose the first connector corresponding to each induction capacitor and the second connector corresponding to each reference capacitor;

and manufacturing the second conductive layer on the sacrificial layer so that the second conductive layer is in direct contact with the first connecting body corresponding to each sensing capacitor and the second conductive layer is in direct contact with the second connecting body corresponding to each reference capacitor.

9. The method of manufacturing a capacitive pressure sensor of claim 4, wherein the method of manufacturing comprises:

And after the sealing layer is manufactured on the second conductive layer, a plurality of second through holes are formed in the dielectric layer and the sealing layer above the dielectric layer, and the second through holes penetrate through the dielectric layer and the sealing layer in the thickness direction so as to expose the conductive pads.

10. A capacitive pressure sensor, comprising:

a substrate provided with a signal processing circuit;

at least one sensing capacitor and at least one reference capacitor on a side surface of the substrate and electrically connected to the signal processing circuitry, respectively, and each comprising a lower plate, an upper plate and a cavity between the lower plate and the upper plate,

the cavity of each sensing capacitor is a cavity without a filler, and the cavity of each reference capacitor is filled with a dielectric body;

the dielectric body is made of one of germanium, germanium-silicon and aluminum.