CN210222061U

CN210222061U - Inertial sensor

Info

Publication number: CN210222061U
Application number: CN201920437611.0U
Authority: CN
Inventors: Jianping Wang; 汪建平; Dengfeng Deng; 邓登峰
Original assignee: Hangzhou Silan Microelectronics Co Ltd
Current assignee: Hangzhou Silan Microelectronics Co Ltd
Priority date: 2019-04-02
Filing date: 2019-04-02
Publication date: 2020-03-31
Anticipated expiration: 2029-04-02

Abstract

The application discloses inertial sensor includes: a substrate; a first movable mass located above the substrate; a second movable mass located above the first movable mass; and the detection electrode is arranged on the first movable mass block, the detection electrode and the second movable mass block form a detection capacitor, and the capacitance change difference of the detection capacitor is twice of the capacitance change difference of the inertial sensor with a single-layer movable mass block under the same area when the external acceleration occurs, so that the sensitivity of the inertial sensor is improved while the area of the inertial sensor is not increased.

Description

Inertial sensor

Technical Field

The utility model relates to a MEMS technical field, more specifically relate to an inertial sensor.

Background

A Micro-Electro-Mechanical System (MEMS) inertial sensor manufactured by adopting a surface process takes a silicon wafer as a substrate, and a three-dimensional micromechanical structure is prepared by multiple thin film depositions and graphic processing. Commonly used film layer materials are: polysilicon, silicon nitride, silicon dioxide, and metal.

The acceleration sensor is an electronic device capable of measuring acceleration force, is one of common devices of micro-electromechanical (MEMS) inertial sensors, and is mainly applied to the fields of position sensing, displacement sensing or motion state sensing and the like.

The inertial sensor mainly comprises a movable mass block, a fixed anchor point, an elastic structure, a fixed electrode and the like. One end of the elastic structure is connected with the fixed anchor point, the other end of the elastic structure is connected with the movable mass block, and a variable capacitor is formed between the fixed electrode and the movable mass block. When external acceleration acts on the movable mass block, inertial force can be formed, the inertial force can form displacement to the movable mass block, and the displacement change is detected by sensing capacitance change between the fixed electrode and the movable mass block, so that the magnitude of the external acceleration can be determined. The main indicators of an inertial sensor are: sensitivity, linearity, temperature drift, impact resistance, etc. The existing method for improving the sensitivity of the inertial sensor is mainly to increase the area, so that the sensitivity of the inertial sensor can be improved by a chip under the condition of small mechanical sensitivity, but the area of the inertial sensor is increased, and the manufacturing cost is increased.

There is therefore a need for improvements to existing inertial sensors to increase the sensitivity of the inertial sensor without increasing the area of the inertial sensor.

SUMMERY OF THE UTILITY MODEL

In view of the above, the present invention is directed to an inertial sensor, which further improves the sensitivity of the inertial sensor.

According to an aspect of the present invention, there is provided an inertial sensor, including: a substrate; a first movable mass located above the substrate; a second movable mass located above the first movable mass; and the detection electrode is arranged on the first movable mass block, and the detection electrode and the second movable mass block form a detection capacitor.

Preferably, the inertial sensor further comprises: a first anchor point to which the first movable mass is connected; and a second anchor point to which the second movable mass is connected.

Preferably, the inertial sensor further includes a wiring layer on the substrate, the first anchor point and the second anchor point being fixed on the wiring layer.

Preferably, the inertial sensor further comprises at least one first elastic element and a second elastic element extending along a first direction, the first elastic element being adapted to connect the first anchor point and the first movable mass, the second elastic element being adapted to connect the second anchor point and the second movable mass.

Preferably, the first anchor point and the second anchor point are arranged in parallel along the first direction.

Preferably, the first anchor point and the second anchor point are disposed in parallel along a second direction perpendicular to the first direction.

Preferably, the length direction of the first elastic element coincides with the midline of the first anchor point, and the length direction of the second elastic element coincides with the midline of the second anchor point.

Preferably, the masses of the first movable mass on the two sides of the first elastic element are not equal, and the masses of the second movable mass on the two sides of the second elastic element are not equal.

Preferably, the mass of the first movable mass on the left side of the first spring element is equal to the mass of the second movable mass on the left side of the second spring element, or the mass of the first movable mass on the right side of the first spring element is equal to the mass of the second movable mass on the right side of the second spring element.

Preferably, the first mass is asymmetrically arranged with respect to the first spring element and the second mass is asymmetrically arranged with respect to the second spring element.

Preferably, at least one side of each mass is provided with a lightening hole.

Preferably, at least one side of each mass is provided with a weight.

Preferably, the lightening holes comprise through holes and/or blind holes.

Preferably, the detection electrodes at least include a first detection electrode and a second detection electrode, the second movable mass block and the first detection electrode and the second detection electrode respectively form a first detection capacitor and a second detection capacitor, and the first detection capacitor and the second detection capacitor form a differential capacitor structure.

Preferably, the first and second detection electrodes are symmetrical about a midline of the first and/or second anchor point.

Preferably, the inertial sensor further comprises an insulating layer between the detection electrode and the first movable mass.

Preferably, the thickness of the first movable mass and the thickness of the second movable mass are respectively 10-25 micrometers.

Preferably, the thicknesses of the detection electrode and the wiring layer are 0.4-1 micron respectively.

Preferably, the thickness of the insulating layer is 0.1-0.3 microns.

The embodiment of the utility model provides an inertial sensor has following beneficial effect.

The inertial sensor comprises two layers of movable mass blocks, a detection electrode is arranged on the first movable mass block, and the detection electrode and the second movable mass block form a differential capacitance structure. When the acceleration in the Z-axis direction exists, the capacitance change difference value of the detection capacitor is obtained through an external circuit, and the corresponding acceleration value can be obtained. The utility model discloses inertial sensor's detection capacitance's capacitance variation difference is the twice of the capacitance variation difference of the inertial sensor of the movable mass block of individual layer under the same area, has improved inertial sensor's sensitivity.

In a preferred embodiment, the areas of the first movable mass block and the second movable mass block are equal, and the lightening holes are arranged on at least one side of the first movable mass block and one side of the second movable mass block, and the lightening holes can be distributed in an array mode, so that the first movable mass block and the second movable mass block can be guaranteed to form a seesaw effect when acceleration in the Z-axis direction is applied to the outside, deep groove etching is not needed to change the areas of the first movable mass block and the second movable mass block when movable mass block patterns are formed, and the process difficulty can be reduced.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings.

Fig. 1 and 2 show schematic cross-sectional views of an inertial sensor according to a first embodiment of the invention in the X-direction and the Y-direction, respectively;

fig. 3 shows a top view of an inertial sensor according to a first embodiment of the invention;

fig. 4 and 5 show a schematic cross-sectional view and a top view, respectively, of another inertial sensor according to a first embodiment of the invention;

fig. 6 shows a schematic structural view of an inertial sensor according to a first embodiment of the present invention when subjected to acceleration in the Z-axis direction;

fig. 7 is a schematic view showing another structure of the inertial sensor according to the first embodiment of the present invention when subjected to acceleration in the Z-axis direction.

Figure 8 shows a schematic cross-sectional view of an inertial sensor according to a second embodiment of the invention;

fig. 9 shows a schematic structural view of a mass according to a second embodiment of the invention;

figure 10 shows a schematic cross-sectional view of an inertial sensor according to a third embodiment of the invention;

fig. 11 to 21 respectively show schematic cross-sectional views at various stages of a method of manufacturing an inertial sensor according to a fourth embodiment of the present invention.

Detailed Description

The invention will be described in more detail below with reference to the accompanying drawings. Like elements in the various figures are denoted by like reference numerals. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale. Moreover, certain well-known elements may not be shown in the figures.

Numerous specific details of the invention, such as structure, materials, dimensions, processing techniques and techniques of components, are set forth in the following description in order to provide a more thorough understanding of the invention. However, as will be understood by those skilled in the art, the present invention may be practiced without these specific details.

It will be understood that when a layer, region or layer is referred to as being "on" or "over" another layer, region or layer in describing the structure of the component, it can be directly on the other layer, region or layer or intervening layers or regions may also be present. Also, if the component is turned over, one layer or region may be "under" or "beneath" another layer or region.

Fig. 1, 2 and 3 show a schematic cross-sectional view and a plan view of an inertial sensor according to a first embodiment of the present invention along the X direction and the Y direction, respectively, and fig. 3 and 4 show a schematic cross-sectional view and a plan view of another inertial sensor according to a first embodiment of the present invention, respectively. The inertial sensor comprises a substrate 11, a wiring layer 12, a first movable mass 13, a second movable mass 14, a first anchor point 15, a second anchor point 16, and a first elastic element 17 and a second elastic element 20.

For convenience of description, in the present invention, the extending direction of the elastic element is recorded as the Y-axis direction, the direction perpendicular to the Y-axis direction and located on the plane of the mass block is recorded as the X-axis direction, and the direction perpendicular to the plane of the mass block is recorded as the Z-axis direction.

The first anchor 15 and the second anchor 16 are fixed to the wiring layer 12, respectively, and the first anchor 15 and the second anchor 16 are adjacent to each other and do not overlap with each other.

As a non-limiting example, as shown in fig. 1-3, the first anchor point 15 and the second anchor point 16 extend in parallel in the Y direction; as another non-limiting example, as shown in fig. 4 and 5, the first anchor point 15 and the second anchor point 16 extend in parallel in the X direction.

The first anchor point 15 and the second anchor point 16 are used to support the first movable mass 13 and the second movable mass 14, respectively, above the substrate 11. In particular, the first anchor point 15 is connected to the side wall of the first movable mass 13 by a first elastic element 17, so that the first movable mass 13 floats above the substrate 11 and the length direction of the first elastic element 17 coincides with the midline of the first anchor point 15; similarly, the second anchor point 16 is connected to the sidewall of the second movable mass 14 through the second elastic element 20, so that the second movable mass 14 floats above the substrate 11, and the length direction of the second elastic element 20 coincides with the midline of the second anchor point 16. The first elastic element 17 and the second elastic element 20 may be elastic sheets or springs or equivalent members. The connection manner of the mass and the substrate is common knowledge of those skilled in the art, and will not be described in detail herein.

The first movable mass 13 and the second movable mass 14 extend in the XY plane, respectively, and the first movable mass 13 and the second movable mass 14 are in turn floated above the substrate 11, so that the first movable mass 13 and the second movable mass 14 are disposed opposite to each other in a direction perpendicular to the substrate 11 (for example, the Z-axis direction in fig. 1).

In order to detect the acceleration in the Z-axis direction, the first movable mass 13 is provided with a detection electrode, and the detection electrode and the second movable mass 14 form a differential capacitor structure, so that the acceleration in the Z-axis direction can be obtained by detecting a change in capacitance value of the capacitor. Specifically, the inertial sensor of the present embodiment includes at least a first detection electrode 18A on the first sub-mass 13A and a second detection electrode 18B on the second sub-mass 13B. The first detection electrode 18A and the third sub-mass block 14A form a first detection capacitor, the second detection electrode 18B and the fourth sub-mass block 14B form a second detection capacitor, and the capacitance change difference between the first detection capacitor and the second detection capacitor is detected through an external circuit, so that the corresponding acceleration in the Z-axis direction can be obtained. The first detection electrode 18A and the second detection electrode 18B may be formed of a capacitor plate structure known to those skilled in the art.

In a preferred embodiment, as shown in fig. 3, the first detection electrode 18A and the second detection electrode 18B are symmetrically disposed about the midline of the first anchor point 15 and the second anchor point 16.

In addition, with the first elastic element 17 as a boundary, the masses on the two sides of the first movable mass 13 are not equal, that is, the masses of the first sub-mass 13A and the second sub-mass 13B of the first movable mass 13 on the two sides of the first elastic element 17 in the X-axis direction are not equal; similarly, the masses of the two sides of the second movable mass 14 are not equal, that is, the masses of the third sub-mass 14A and the fourth sub-mass 14B of the second movable mass 14 located on the two sides of the second elastic element 20 in the X-axis direction are not equal, so as to ensure that the first movable mass 13 and the second movable mass 14 form a "seesaw" effect when the acceleration exists in the Z-axis direction.

In a specific embodiment of the present invention, as shown in fig. 1 and 3, the areas of the first sub-mass block 13A and the second sub-mass block 13B are not equal, and thus the corresponding masses are different; the areas of the third sub-mass 14A and the fourth sub-mass 14B are not equal, and thus their corresponding masses are different. As an example, the area of the first sub-mass 13A is larger than that of the second sub-mass 13B, and the area of the third sub-mass 14A is smaller than that of the fourth sub-mass 14B, so that when there is an acceleration in the Z-axis direction, the first sub-mass 13A and the second sub-mass 13B perform a "seesaw" motion around the elastic elements connected thereto; the third sub-mass 14A and the fourth sub-mass 14B perform a "seesaw" motion about the elastic members connected thereto. In addition, the first movable mass 13 and the second movable mass 14 are in asymmetric and opposite layouts, that is, the mass centers of the first movable mass 13 and the second movable mass 14 are respectively located at two sides of the elastic element, when acceleration in the Z-axis direction exists, one sides of the first movable mass 13 and the second movable mass 14 will move relatively, and the other sides of the first movable mass 13 and the second movable mass 14 will move back to back, so as to ensure that the detection electrode on the first movable mass 13 and the second movable mass 14 form a differential capacitance structure.

In an alternative embodiment, the masses of the second sub-mass 13B and the fourth sub-mass 14B are equal. As shown in fig. 1 and 3, the areas of the second sub-mass block 13B and the fourth sub-mass block 14B are equal, so that the seesaw effect of the first movable mass block 13 and the second movable mass block 14 can be ensured to be formed when the external has the acceleration in the Z-axis direction, and the process difficulty can be reduced.

The inertial sensor furthermore comprises an insulating layer 19 between the first movable mass 13 and the detection electrodes, the insulating layer 19 being, for example, Al₂O₃Or Si₃N₄The device has the functions of insulation and fumigation protection.

Fig. 6 and 7 are schematic structural views of the inertial sensor according to the first embodiment of the present invention when subjected to acceleration in the Z-axis direction, respectively.

As shown in fig. 6, when there is an acceleration g in the Z-axis direction, since the weights of the two sides of the first movable mass 13 and the second movable mass 14 are not equal, the distance between the first sub mass 13A and the third sub mass 14A increases, and the distance between the second sub mass 13B and the fourth sub mass 14B decreases, so that the first detection capacitor and the second detection capacitor form a differential capacitor structure.

As shown in fig. 7, when an acceleration g in the Z-axis direction exists, since the weights of the two sides of the first movable mass 13 and the second movable mass 14 are not equal, the distance between the first sub mass 13A and the third sub mass 14A decreases, and the distance between the second sub mass 13B and the fourth sub mass 14B increases, so that the first detection capacitor and the second detection capacitor form a differential capacitor structure.

The first detection capacitor and the second detection capacitor are completely opposite in change, a differential capacitor structure is formed jointly, and the acceleration in the Z-axis direction can be obtained by detecting the difference value of the capacitance change of the first detection capacitor and the capacitance change of the second detection capacitor.

In this embodiment, the inertial sensor includes two layers of movable masses, the detection electrode is disposed on the first layer of movable mass, and the detection electrode and the second layer of movable mass form a differential capacitor structure. When the acceleration in the Z-axis direction exists, the capacitance change difference value of the detection capacitor is obtained through an external circuit, and the corresponding acceleration value can be obtained. The utility model discloses inertial sensor's detection capacitance's capacitance variation difference is the twice of the capacitance variation difference of the inertial sensor of the movable mass block of individual layer under the same area, has improved inertial sensor's sensitivity when not increasing inertial sensor's area.

Fig. 8 shows a schematic cross-sectional view of an inertial sensor according to a second embodiment of the present invention, and as shown in fig. 8, the inertial sensor of the present embodiment includes a substrate 21, a wiring layer 22, a first movable mass 23, a second movable mass 24, a first anchor point 25, and a second anchor point 26.

The first anchor points 25 and the second anchor points 26 are fixed on wiring layers of the substrate 21, respectively, and the first anchor points 25 and the second anchor points 26 are adjacent and do not overlap with each other. The first anchor point 25 and the second anchor point 26 are used to support the first movable mass 23 and the second movable mass 24, respectively, above the substrate 21. Specifically, the first anchor point 25 is connected to the sidewall of the first movable mass 23 through first elastic elements (not shown) on two sides thereof, so that the first movable mass 23 floats above the substrate 21, and the length direction of the first elastic elements coincides with the center line of the first anchor point 25; in a similar manner to that described above,

the second anchor point 26 is connected to the sidewall of the second movable mass 24 through a second elastic element (not shown) on both sides thereof, so that the second movable mass 24 floats above the substrate 21, and the length direction of the second elastic element coincides with the center line of the second anchor point 26. The first elastic element and the second elastic element may be elastic pieces or springs or equivalent members thereof. The connection manner of the mass and the substrate is common knowledge of those skilled in the art, and will not be described in detail herein.

In order to detect the acceleration in the Z-axis direction, the first movable mass 23 is provided with a detection electrode, and the detection electrode and the second movable mass 24 form a differential capacitance structure, so that the acceleration in the Z-axis direction can be obtained by detecting a change in capacitance value of the capacitance. Specifically, the inertial sensor of the present embodiment includes at least a first detection electrode 28A on the first sub-mass 23A and a second detection electrode 28B on the second sub-mass 23B. The first detection electrode 28A and the third sub-mass block 24A form a first detection capacitor, the second detection electrode 28B and the fourth sub-mass block 24B form a second detection capacitor, and the capacitance change difference between the first detection capacitor and the second detection capacitor is detected through an external circuit, so that the corresponding acceleration in the Z-axis direction can be obtained. First sensing electrode 28A and second sensing electrode 28B may be formed of a capacitor plate structure known to those skilled in the art.

The inertial sensor furthermore comprises an insulating layer 29 between the first movable mass 23 and the detection electrodes, the insulating layer 29 being, for example, Al₂O₃Or Si₃N₄The device has the functions of insulation and fumigation protection.

The inertial sensor of the present embodiment is different from the inertial sensor of the first embodiment in that the areas of the first sub-mass 23A, the second sub-mass 23B, the third sub-mass 24A and the fourth sub-mass 24B in the present embodiment are equal, and therefore in order to make the masses on the two sides of the first movable mass 23 and the second movable mass 24 unequal, at least one side of the first movable mass 23 and the second movable mass 24 is provided with lightening holes, which may be a plurality of lightening holes distributed in an array. The lightening hole can be a through hole and is formed by an etching method during manufacturing; or blind holes, and can be etched by adding a layer of mask. In another embodiment, it is also possible to make the masses on both sides of the first movable mass 23 and the second movable mass 24 unequal by adding a weight on at least one side of the first movable mass 23 and the second movable mass 24.

Fig. 9 shows a schematic structural diagram of a mass block of an inertial sensor according to a second embodiment of the present invention. As an example, the first, second, third and fourth sub-masses 23A, 23B, 24A and 24B are all provided with lightening holes 41, the lightening holes 41 may be plural and distributed in an array, and the mass of each lightening hole may be changed by controlling the number of lightening holes on each mass. As shown in fig. 9, the first sub-mass 23A has 9 lightening holes 41, the second sub-mass 23B and the fourth sub-mass 24B have 16 lightening holes 41, and the third sub-mass 24A has 36 lightening holes 41, so that the mass of the first sub-mass 23A is greater than that of the second sub-mass 23B, the mass of the third sub-mass 24A is less than that of the fourth sub-mass 24B, and the masses of the second sub-mass 23B and the fourth sub-mass 24B are equal.

It should be noted that, the shape, number and combination relationship of the lightening holes on the mass block of the present embodiment are not limited thereto, and those skilled in the art may select the number of the lightening holes on the mass block according to specific situations.

Fig. 10 shows a schematic cross-sectional view of an inertial sensor according to a third embodiment of the invention. As shown in fig. 10, the inertial sensor includes a substrate 31, a wiring layer 32, a first movable mass 33, a second movable mass 34, a first anchor point 35, and a second anchor point 36.

The first anchor points 35 and the second anchor points 36 are fixed on the substrate 31, respectively, and the first anchor points 35 and the second anchor points 36 are adjacent and do not overlap with each other. The first anchor point 35 and the second anchor point 36 are used to support the first movable mass 33 and the second movable mass 34, respectively, above the substrate 31. Specifically, the first anchor point 35 is connected to the sidewall of the first movable mass 33 through the first elastic elements (not shown) on two sides thereof, so that the first movable mass 33 floats above the substrate 31, and the length direction of the first elastic elements coincides with the center line of the first anchor point 35; similarly, the second anchor point 36 is connected to the sidewall of the second movable mass 34 through a second elastic element (not shown) on both sides thereof, so that the second movable mass 34 floats above the substrate 31, and the length direction of the second elastic element coincides with the center line of the second anchor point 36. The first elastic element and the second elastic element may be elastic pieces or springs or equivalent members thereof. The connection manner of the mass and the substrate is common knowledge of those skilled in the art, and will not be described in detail herein.

In order to detect the acceleration in the Z-axis direction, the first movable mass 33 is provided with a detection electrode, and the detection electrode and the second movable mass 34 form a differential capacitance structure, so that the acceleration in the Z-axis direction can be obtained by detecting a change in capacitance value of the capacitance. Specifically, the inertial sensor of the present embodiment includes at least a first detection electrode 38A on the first sub-mass 33A and a second detection electrode 38B on the second sub-mass 33B. The first detection electrode 38A and the third sub mass block 34A form a first detection capacitor, the second detection electrode 38B and the fourth sub mass block 34B form a second detection capacitor, and the capacitance change difference between the first detection capacitor and the second detection capacitor is detected by an external circuit, so that the corresponding acceleration in the Z-axis direction can be obtained. The first detection electrode 38A and the second detection electrode 38B may be formed of a capacitor plate structure known to those skilled in the art.

The inertial sensor furthermore comprises an insulating layer 39 between the first movable mass 33 and the detection electrodes, the insulating layer 39 being, for example, Al₂O₃Or Si₃N₄The device has the functions of insulation and fumigation protection.

The inertial sensor of the present embodiment is different from the inertial sensor of the first embodiment in that the areas of the second sub-mass 33B and the fourth sub-mass 34B in the present embodiment are not equal, that is, the masses of the second sub-mass 33B and the fourth sub-mass 34B are not equal, so that the mass difference exists on both sides of the first movable mass 33 and the second movable mass 34, thereby improving the sensitivity of mass deflection and improving the sensitivity of the inertial sensor.

Fig. 11 to 21 are schematic cross-sectional views of respective stages of a method for manufacturing an inertial sensor according to a fourth embodiment of the present invention, and the method for manufacturing the inertial sensor according to the first embodiment will be described below by way of example.

As shown in fig. 11, doped polysilicon is deposited on a substrate 101 and patterned using photolithography and etching processes to form a wiring layer 102. Preferably, the substrate 101 may be a semiconductor substrate. More preferably, the semiconductor substrate 101 is, for example, a silicon substrate. Further preferably, the semiconductor substrate 101 is, for example, an N-type silicon substrate having a crystal orientation of <100 >.

In the deposition step, a low pressure chemical vapor deposition (LP-CVD) method may be used to deposit doped polysilicon on the substrate 101, wherein the deposition temperature may be 570 ℃ to 630 ℃, and the thickness of the polysilicon is 0.4 to 1 μm. Further, the thickness of the polysilicon is 0.8 μm.

In the patterning step, for example, a resist layer is formed on the surface of the polysilicon, and a pattern including an opening is formed in the resist layer by a photolithography process. The exposed portions of the polysilicon are removed with a selective etchant using the resist layer as a mask. The etch may stop at the substrate 101 surface due to the selectivity of the etch. After etching, the resist layer may be removed by ashing or dissolution in a solvent.

After patterning, the remaining portions of polysilicon form the wiring layer 102. The etching process of the patterning step is, for example, anisotropic etching. The pattern of the wiring layer 102 is complementary to the shape of the pattern of the opening in the mask.

The wiring layer 102 is used to realize electrical connection between the anchor point of the subsequent step and an external circuit. Further, in a subsequent step, a first anchor and a second anchor will be implemented above the wiring layer 102A.

As shown in fig. 12, a first sacrificial layer 103 is formed on exposed surfaces of the substrate 101 and the wiring layer 102. The first sacrificial layer 103 is composed of an insulating material, such as silicon dioxide. For example, a first sacrificial layer 103 made of silicon dioxide may be formed on the semiconductor substrate 101 by a method such as low pressure chemical vapor deposition (LP-CVD) or Plasma Enhanced Chemical Vapor Deposition (PECVD), and the thickness of the first sacrificial layer 103 is in a range of 1.2 to 1.8 μm. Further, the thickness of the first sacrificial layer is 1.2 μm. Preferably, the surface of the first sacrificial layer 103 is planarized by Chemical Mechanical Polishing (CMP) or by glue spreading followed by isotropic etch back.

As described below, the first sacrificial layer 103 is used not only to provide interlayer insulation for a conductor layer to be formed later, but also at least a portion of the first sacrificial layer 103 serves as a sacrificial layer to be removed in a subsequent step to form a cavity.

Then, patterning is performed using the above-described photolithography and etching process, thereby forming a via hole 103A that passes through the first sacrificial layer 103 to the wiring layer 102 located on the substrate 101, the via hole 103A exposing at least a part of the surface of the wiring layer 102A, as shown in fig. 13.

In the etching process of this step, an appropriate etchant may be selected, utilizing the property of the etchant to selectively remove the exposed portion of the first sacrificial layer 103 with respect to the substrate 101, such that the etching stops at the surface of the substrate 101. Thus, by the selective etching by the etchant, the etching depth can be controlled so that the via hole 103A passes right through the first sacrificial layer 103. In an alternative embodiment, the depth of etching is controlled by controlling the time of etching so that the via penetrates the first sacrificial layer 103 to reach the surface of the wiring layer 102A.

As shown in fig. 14, polysilicon is epitaxially grown on the first sacrificial layer 103, thereby forming a first structural layer 104.

For example, polysilicon may be epitaxially grown on the first sacrificial layer 103 by low pressure chemical vapor deposition (LP-CVD) or Plasma Enhanced Chemical Vapor Deposition (PECVD) to form the first structure layer 104. The thickness of the first structural layer 104 is in the range of 10 to 25 μm. Further, the thickness of the first structural layer 104 is 10 μm.

Further, forming a first anchor and a second anchor (not shown in the figure) above the wiring layer 102A at the same time of forming the first structural layer 104 is also included. Further, the via hole 103A is filled while the first structure layer 104 is formed to form a lower half structure of the first anchor point and the second anchor point.

As shown in fig. 15, an insulating layer 105 is formed over the first structure layer 104, and the insulating layer 105 is made of an insulating material such as silicon dioxide or aluminum oxide (Al)₂O₃) Or silicon nitride (Si)₃N₄) The insulating materials play the roles of insulation and fumigation protection, and are used as a deep groove etching protective layer. Thermal oxidation, low pressure chemical vapor deposition (LP-CVD), Plasma Enhanced Chemical Vapor Deposition (PECVD), or the like may be used to deposit an insulating material on the surface of the first structural layer 104, and patterning may be performed using photolithography and etching processes, and then an insulating layer 105 may be formed on the surface of the first structural layer 104, wherein the insulating layer 105 partially covers the first structural layer 104. Further, the thickness of the insulating layer 105 is in a range of 0.1 to 0.3 μm. Further, the thickness of the insulating layer 105 is 0.1 μm.

As shown in fig. 16, polysilicon is epitaxially grown on the insulating layer 105, and the detection electrode 106 is formed using a photolithography or etching process. The detection electrode 106 is formed not only on the surface of the insulating layer 105 but also on the first structural layer 104. Further, the detection electrode 106 formed on the insulating layer 105 is symmetrical with respect to the central axis of the through hole 103A, and an orthographic projection of the detection electrode 106 formed on the first structural layer 104 on the substrate 101 is located in the through hole 103A.

For example, polysilicon may be epitaxially grown on the insulating layer 105 by a method such as low pressure chemical vapor deposition (LP-CVD) or Plasma Enhanced Chemical Vapor Deposition (PECVD), and then patterned by photolithography and etching processes to form the sensing electrode 106. Furthermore, the thickness of the detecting electrode 106 is 0.4 to 1 μm. Further, the thickness of the detection electrode 106 is 0.8 μm.

In the patterning step, for example, a resist layer is formed on the surface of the polysilicon, and a pattern including an opening is formed in the resist layer by a photolithography process. The exposed portions of the polysilicon are removed with a selective etchant using the resist layer as a mask. Due to the selectivity of the etching, the etching may be stopped at the surface of the insulating layer 105 or the first structural layer 104. After etching, the resist layer may be removed by ashing or dissolution in a solvent.

After patterning, the remaining portion of the polysilicon forms the sensing electrode 106. The etching process of the patterning step is, for example, anisotropic etching. The pattern of the detection electrode 106 is complementary to the shape of the pattern of the opening in the mask.

As shown in fig. 17, a second sacrificial layer 107 is formed on the exposed surfaces of the insulating layer 105, the detection electrode 106, and the first structural layer 104. The second sacrificial layer 107 is composed of an insulating material, such as silicon dioxide. For example, a second sacrificial layer 107 of silicon dioxide may be formed on the exposed surfaces of the insulating layer 105, the sensing electrode 106 and the first structure layer 104 by low pressure chemical vapor deposition (LP-CVD), Plasma Enhanced Chemical Vapor Deposition (PECVD), etc. The thickness of the second sacrificial layer 107 is in the range of 1.2 to 1.8 μm. Further, the thickness of the second sacrificial layer 107 is, for example, 1.6 μm. Preferably, the surface of the second sacrificial layer 107 is planarized by Chemical Mechanical Polishing (CMP) or by glue spreading followed by isotropic etch back.

As described below, the second sacrificial layer 107 is used not only to provide interlayer insulation for a conductor layer to be formed later, but also at least a portion of the second sacrificial layer 107 serves as a sacrificial layer to be removed in a subsequent step to form a cavity.

Then, patterning is performed using the above-described photolithography and etching process, thereby forming a through hole 107A that reaches the detection electrode 106 through the second sacrificial layer 107, as shown in fig. 18.

In the etching process of this step, an appropriate etchant may be selected, utilizing the property of the etchant to selectively remove the exposed portion of the second sacrificial layer 107 with respect to the detection electrode 106, so that etching stops at the surface of the detection electrode 106. Thus, by selective etching with an etchant, the etching depth can be controlled so that the through hole 107A just passes through the second sacrificial layer 107, exposing at least a portion of the detection electrode 106. In an alternative embodiment, the depth of etching is controlled by controlling the time of etching so that the through hole penetrates the second sacrificial layer 107 to reach the surface of the detection electrode 106.

The etching process of the patterning step is, for example, anisotropic etching. The pattern of the via hole formed in the second sacrificial layer 107 and the shape of the opening pattern in the mask are substantially the same.

As shown in fig. 19, polysilicon is epitaxially grown on the second sacrificial layer 107, thereby forming a second structure layer 108. The second structure layer 108 is formed not only on the surface of the second sacrificial layer 107 but also fills the through-hole, reaching the detection electrode 106 via the through-hole.

For example, the second structure layer 108 may be formed by epitaxially growing polysilicon on the second sacrificial layer 107 by a method such as low pressure chemical vapor deposition (LP-CVD) or Plasma Enhanced Chemical Vapor Deposition (PECVD). The thickness of the second structural layer 108 is 10 to 25 μm. Further, the thickness of the second structure layer 108 is, for example, 10 μm.

Further, forming the second structural layer 108 further includes filling the via hole 107A, and forming an upper half portion of the second anchor point on the detection electrode 106 to form a complete second anchor point.

Next, the first structural layer 104 and the second structural layer 108 are patterned using photolithography and etching processes, thereby forming a moving mass pattern having a gap around to expose surfaces of the first sacrificial layer 103 and the second sacrificial layer 107 and an elastic member pattern. As shown in fig. 20, the first structural layer 104 and the second structural layer 108 are patterned by using photolithography and etching processes, thereby forming a first sub-mass 141, a second sub-mass 142, a third sub-mass 143, and a fourth sub-mass 144.

In the etching process of this step, the protective layer is etched using the insulating layer 105 as a deep trench, and the exposed portions of the first structural layer 104, the second structural layer 108, and the second sacrificial layer 107 are selectively removed by using an etchant to form a plurality of

deep trenches

108A and 108B.

Deep trenches

108A and 108B may be used to remove the sacrificial layer in a vapor phase fumigation manner in a later process step.

Moreover, a part of the second sub-mass block 142, the third sub-mass block 143 and the fourth sub-mass block 144 is selectively etched through the deep groove 108B, so that the first sub-mass block 141 and the second sub-mass block 142 have different sizes, and then the first sub-mass block 141 and the second sub-mass block 142 have different masses, and the first sub-mass block 141 and the second sub-mass block 142 can form a seesaw effect when external acceleration in the Z-axis direction occurs; the third sub-mass 143 and the fourth sub-mass 144 have different sizes, and then the third sub-mass 143 and the fourth sub-mass 144 have different masses, so that the third sub-mass 143 and the fourth sub-mass 144 can form a seesaw effect when external acceleration in the Z-axis direction occurs.

In an alternative embodiment, if the mass of the first to fourth sub-masses is changed by providing lightening holes in at least one of the first to fourth sub-masses 141-144, the deep groove 108B need not be formed in this step. The lightening holes can be distributed in an array in a plurality. The lightening hole can be a through hole and is formed by an etching method during manufacturing; or blind holes, and can be etched by adding a layer of mask.

In another embodiment, the masses of the first to fourth sub-masses can be changed by adding a weight to at least one of the first to fourth sub-masses 141-144.

In an alternative embodiment, the second sub-mass 142 has a smaller mass than the fourth sub-mass 144, and it is necessary to pattern the first movable mass pattern by photolithography and etching processes after epitaxially growing polysilicon to form the first structural layer 104 in fig. 11.

As shown in fig. 21, the second sacrificial layer 107 between the moving mass patterns and the first sacrificial layer 103 before the moving mass and the substrate are then etched away by means of vapor fumigation with hydrofluoric acid (HF), so that the moving mass patterns are released to form the movable mass of the device substrate 101.

The etching step uses, for example, isotropic etching using gaseous HF as an etchant. The second structural layer 108 serves as a mask, and the etchant reaches the exposed surfaces of the first sacrificial layer 103 and the second sacrificial layer 107 via a plurality of deep grooves in the second structural layer 108. Due to the selectivity of the etching, the etching may selectively remove a first portion of the first sacrificial layer 103 exposed at the bottom of the deep trench with respect to the second structural layer 108, the first structural layer 104, and the detection electrode 106, and further laterally remove a second portion of the first sacrificial layer 103 adjacent to the first portion; the etch may also selectively laterally remove third portions of the second sacrificial layer 107 exposed to the plurality of deep trench sidewalls.

In summary, the inertial sensor of the above embodiment includes two layers of movable masses, the detection electrode is disposed on the first layer of movable mass, and the detection electrode and the second layer of movable mass form a differential capacitor structure. When the acceleration in the Z-axis direction exists, the capacitance change difference value of the detection capacitor is obtained through an external circuit, and the corresponding acceleration value can be obtained. The utility model discloses inertial sensor's detection capacitance's capacitance variation difference is the twice of the capacitance variation difference of the inertial sensor of the movable mass block of individual layer under the same area, has improved inertial sensor's sensitivity.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

In accordance with the embodiments of the present invention as set forth above, these embodiments are not exhaustive and do not limit the invention to the precise embodiments described. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and its various embodiments with various modifications as are suited to the particular use contemplated. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. An inertial sensor, comprising:

a substrate;

a first movable mass located above the substrate;

a second movable mass located above the first movable mass; and

and the detection electrode and the second movable mass block form a detection capacitor.

2. The inertial sensor of claim 1, further comprising:

a first anchor point to which the first movable mass is connected; and

a second anchor point to which the second movable mass is connected.

3. The inertial sensor of claim 2, further comprising a wiring layer on the substrate, the first and second anchors being fixed to the wiring layer.

4. An inertial sensor according to claim 2, characterized in that it further comprises at least one first and second elastic element extending in a first direction,

the first elastic element is used for connecting the first anchor point and the first movable mass, and the second elastic element is used for connecting the second anchor point and the second movable mass.

5. The inertial sensor of claim 4, wherein the first anchor point and the second anchor point are disposed in parallel along the first direction.

6. An inertial sensor according to claim 4, characterised in that the first and second anchor points are arranged in parallel along a second direction perpendicular to the first direction.

7. An inertial sensor according to claim 5 or 6, characterised in that the first elastic element has a length direction coinciding with the midline of the first anchor point and the second elastic element has a length direction coinciding with the midline of the second anchor point.

8. An inertial sensor according to claim 4, characterized in that the masses of the first movable mass on either side of the first elastic element are unequal and the masses of the second movable mass on either side of the second elastic element are unequal.

9. An inertial sensor according to claim 8, characterized in that the mass of the first movable mass on the left of the first elastic element is equal to the mass of the second movable mass on the left of the second elastic element, or

The mass of the first movable mass to the right of the first spring is equal to the mass of the second movable mass to the right of the second spring.

10. An inertial sensor according to claim 8, characterised in that the first movable mass is arranged asymmetrically with respect to the first spring element and the second movable mass is arranged asymmetrically with respect to the second spring element.

11. An inertial sensor according to any of claims 8-10, characterised in that at least one side of each mass is provided with lightening holes.

12. An inertial sensor according to any of claims 8-10, characterised in that at least one side of each mass is provided with a weight.

13. An inertial sensor according to claim 11, characterised in that the lightening holes comprise through holes and/or blind holes.

14. An inertial sensor according to claim 1, characterised in that the detection electrodes comprise at least a first detection electrode and a second detection electrode,

the second movable mass block, the first detection electrode and the second detection electrode form a first detection capacitor and a second detection capacitor respectively, and the first detection capacitor and the second detection capacitor form a differential capacitor structure.

15. An inertial sensor according to claim 14, characterised in that the first and second detection electrodes are symmetrical about a midline of the first and/or second anchor point.

16. An inertial sensor according to claim 1, further comprising an insulating layer between the detection electrode and the first movable mass.

17. An inertial sensor according to claim 1, characterised in that the first and second movable masses are each 10-25 microns thick.

18. The inertial sensor according to claim 3, wherein the thickness of the detection electrode and the wiring layer is 0.4 to 1 μm, respectively.

19. An inertial sensor according to claim 16, characterised in that the thickness of the insulating layer is 0.1 to 0.3 microns.