Inertial sensor and method of manufacturing the same

Abstract

The present application discloses an inertial sensor and a manufacturing method thereof, comprising: a substrate; a first movable mass block, located above the substrate; a second movable mass block, located above the first movable mass block; and a detection electrode arranged on the first movable mass block, wherein the detection electrode and the second movable mass block form a detection capacitor, wherein when an external acceleration occurs, the capacitance change difference of the detection capacitor is twice the capacitance change difference of an inertial sensor with a single-layer movable mass block under the same area, thereby improving the sensitivity of the inertial sensor without increasing the area of ​​the inertial sensor.

Description

Technical Field

[0001] The present invention relates to the field of MEMS technology, and more particularly to an inertial sensor and a manufacturing method thereof. Background Art

[0002] The micro-electro-mechanical system (MEMS) inertial sensor made by surface technology is based on silicon wafers and is formed into a three-dimensional micro-mechanical structure through multiple thin film deposition and graphic processing. Commonly used thin film layer materials are: polysilicon, silicon nitride, silicon dioxide and metal.

[0003] An accelerometer is an electronic device that can measure acceleration force. It is one of the commonly used devices of micro-electromechanical systems (MEMS) inertial sensors. Accelerometers are mainly used in the fields of position sensing, displacement sensing, or motion state sensing.

[0004] The inertial sensor is mainly composed of a movable mass block, a fixed anchor point, an elastic structure and a fixed electrode. Among them, one end of the elastic structure is connected to the fixed anchor point, and the other end is connected to the movable mass block. A variable capacitor is formed between the fixed electrode and the movable mass block. When the external acceleration acts on the movable mass block, an inertial force will be formed. The inertial force will cause a displacement of the movable mass block. The displacement change can be detected by sensing the capacitance change between the fixed electrode and the movable mass block, and the magnitude of the external acceleration can be determined. The main indicators of the inertial sensor are: sensitivity, linearity, temperature drift and impact resistance. The existing method of improving the sensitivity of the inertial sensor is mainly to increase the area, so that it can be amplified by the chip when the mechanical sensitivity is small. Although this can improve the sensitivity of the inertial sensor, it increases the area of ​​the inertial sensor and increases the manufacturing cost.

[0005] Therefore, it is necessary to improve the existing inertial sensor to improve the sensitivity of the inertial sensor without increasing the area of ​​the inertial sensor. Summary of the invention

[0006] In view of this, an object of the present invention is to provide an inertial sensor and a manufacturing method thereof, so as to further improve the sensitivity of the inertial sensor.

[0007] According to one aspect of the present invention, there is provided an inertial sensor, comprising: a substrate; a first movable mass block located above the substrate; a second movable mass block located above the first movable mass block; and a detection electrode disposed on the first movable mass block, the detection electrode and the second movable mass block forming a detection capacitor.

[0008] Preferably, the inertial sensor further comprises: a first anchor point, to which the first movable mass block is connected; and a second anchor point, to which the second movable mass block is connected.

[0009] Preferably, the inertial sensor further comprises a wiring layer located on the substrate, and the first anchor point and the second anchor point are fixed on the wiring layer.

[0010] Preferably, the inertial sensor further comprises at least one first elastic element and a second elastic element extending along the first direction, the first elastic element being used to connect the first anchor point and the first movable mass block, and the second elastic element being used to connect the second anchor point and the second movable mass block.

[0011] Preferably, the first anchor point and the second anchor point are arranged in parallel along the first direction.

[0012] Preferably, the first anchor point and the second anchor point are arranged in parallel along a second direction perpendicular to the first direction.

[0013] 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.

[0014] Preferably, the masses of the first movable mass block located on two sides of the first elastic element are unequal, and the masses of the second movable mass block located on two sides of the second elastic element are unequal.

[0015] Preferably, the mass of the first movable mass block located on the left side of the first elastic element is equal to the mass of the second movable mass block located on the left side of the second elastic element, or the mass of the first movable mass block located on the right side of the first elastic element is equal to the mass of the second movable mass block located on the right side of the second elastic element.

[0016] Preferably, the first mass block is asymmetrically arranged with respect to the first elastic element, and the second mass block is asymmetrically arranged with respect to the second elastic element.

[0017] Preferably, at least one side of each mass block is provided with a weight-reducing hole.

[0018] Preferably, a counterweight is provided on at least one side of each mass block.

[0019] Preferably, the weight-reducing hole comprises a through hole and / or a blind hole.

[0020] Preferably, the detection electrode comprises at least 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 constitute a differential capacitor structure.

[0021] Preferably, the first detection electrode and the second detection electrode are symmetrical about a midline of the first anchor point and / or the second anchor point.

[0022] Preferably, the inertial sensor further includes an insulating layer located between the detection electrode and the first movable mass block.

[0023] Preferably, the thickness of the first movable mass block and the second movable mass block are respectively 10-25 microns.

[0024] Preferably, the thickness of the detection electrode and the wiring layer are respectively 0.4-1 micrometer.

[0025] Preferably, the thickness of the insulating layer is 0.1-0.3 micrometers.

[0026] According to another aspect of the present invention, there is provided a method for manufacturing an inertial sensor, comprising: forming a wiring layer on a substrate; forming a first sacrificial layer on the substrate and the wiring layer; forming a first structural layer on the first sacrificial layer; forming a detection electrode on the first structural layer; forming a second sacrificial layer on the first structural layer and the detection electrode; forming a second structural layer on the second sacrificial layer; patterning the first structural layer and the second structural layer to form a moving mass block pattern; and removing the first sacrificial layer and the second sacrificial layer to form a first movable mass block and a second movable mass block, the first movable mass block and the second movable mass block being floated on the substrate, and the detection electrode and the second movable mass block forming a detection capacitor.

[0027] Preferably, the manufacturing method also includes, before forming the first structural layer, etching on the upper surface of the first sacrificial layer to form a first through hole, the first through hole exposing at least a portion of the surface of the wiring layer; and filling the first through hole to form a first anchor point and a portion of the structure of the second anchor point; before forming the second structural layer, etching on the upper surface of the second sacrificial layer to form a second through hole, the second through hole exposing at least a portion of the detection electrode, and filling the second through hole to form another portion of the structure of the second anchor point.

[0028] Preferably, before forming the detection electrode on the first structural layer, the method further includes: forming an insulating layer on the upper surface of the first structural layer; and patterning the insulating layer so that the insulating layer partially covers the first structural layer.

[0029] Preferably, the forming of the first movable mass block and the second movable mass block includes: using the insulating layer as a deep groove etching protection layer to form a plurality of first deep grooves and a second deep groove extending from the upper surface of the second structural layer to the upper surface of the first sacrificial layer; and performing isotropic etching through the plurality of first deep grooves and the second deep grooves, thereby laterally removing at least a portion of the first sacrificial layer and the second sacrificial layer.

[0030] Preferably, the manufacturing method also includes patterning the first structural layer and the second structural layer to respectively form a first elastic element and a second elastic element extending along a first direction, the first elastic element being used to connect the first anchor point and the first movable mass block, and the second elastic element being used to connect the second anchor point and the second movable mass block.

[0031] Preferably, the first anchor point and the second anchor point are arranged in parallel along the first direction.

[0032] Preferably, the first anchor point and the second anchor point are arranged in parallel along a second direction perpendicular to the first direction.

[0033] 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.

[0034] Preferably, the masses of the first movable mass block located on two sides of the first elastic element are unequal, and the masses of the second movable mass block located on two sides of the second elastic element are unequal.

[0035] Preferably, the manufacturing method further comprises patterning at least one side of the first movable mass block and the second movable mass block to form a weight-reducing hole.

[0036] Preferably, the weight-reducing hole comprises a through hole and / or a blind hole.

[0037] Preferably, the manufacturing method further comprises forming a counterweight on at least one side of the first movable mass block and the second movable mass block.

[0038] Preferably, the thickness of the first structural layer and the second structural layer are respectively 10-25 microns.

[0039] Preferably, the thickness of the detection electrode and the wiring layer are respectively 0.4-1 micrometer.

[0040] Preferably, the thickness of the insulating layer is 0.1-0.3 micrometers.

[0041] Preferably, the thickness of the first sacrificial layer and the second sacrificial layer is 1.2-1.8 microns.

[0042] The inertial sensor and the manufacturing method thereof provided by the embodiments of the present invention have the following beneficial effects.

[0043] The inertial sensor includes two layers of movable mass blocks, and the detection electrode is arranged on the first movable mass block, and the detection electrode and the second movable mass block form a differential capacitor structure. When there is an acceleration in the Z-axis direction, the capacitance change difference of the detection capacitor is obtained through an external circuit, and the corresponding acceleration value can be obtained. The capacitance change difference of the detection capacitor of the inertial sensor of the embodiment of the present invention is twice the capacitance change difference of the inertial sensor of the single-layer movable mass block under the same area, which improves the sensitivity of the inertial sensor.

[0044] In a preferred embodiment, the areas of the first movable mass block and the second movable mass block are equal, and a weight-reducing hole is provided on at least one side of the first movable mass block and the second movable mass block. The weight-reducing holes may be multiple and distributed in an array. This not only ensures that the first movable mass block and the second movable mass block form a seesaw effect when there is an acceleration in the Z-axis direction in the outside world, but also eliminates the need for deep groove etching to change the areas of the first movable mass block and the second movable mass block when forming the movable mass block pattern, thereby reducing the process difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings.

[0046] Figure 1 and Figure 2 Schematic cross-sectional views of an inertial sensor along the X direction and the Y direction according to the first embodiment of the present invention are respectively shown;

[0047] Figure 3 A top view of an inertial sensor according to a first embodiment of the present invention is shown;

[0048] Figure 4 and Figure 5 A schematic cross-sectional view and a top view respectively show another inertial sensor according to a first embodiment of the present invention;

[0049] Figure 6 A schematic diagram showing a structure of an inertial sensor according to a first embodiment of the present invention when subjected to acceleration in the Z-axis direction;

[0050] Figure 7 Another schematic structural diagram of the inertial sensor according to the first embodiment of the present invention when subjected to acceleration in the Z-axis direction is shown.

[0051] Figure 8 A schematic cross-sectional view showing an inertial sensor according to a second embodiment of the present invention;

[0052] Fig. 9 A schematic structural diagram of a mass block according to a second embodiment of the present invention is shown;

[0053] Fig.10 A schematic cross-sectional view showing an inertial sensor according to a third embodiment of the present invention;

[0054] Figures 11 to 21 Schematic cross-sectional views of various stages of a method for manufacturing an inertial sensor according to a fourth embodiment of the present invention are shown respectively. DETAILED DESCRIPTION

[0055] The present invention will be described in more detail below with reference to the accompanying drawings. In each of the accompanying drawings, the same elements are represented by similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not drawn to scale. In addition, some well-known parts may not be shown in the drawings.

[0056] Many specific details of the present invention are described below, such as component structures, materials, dimensions, processing techniques and technologies, in order to more clearly understand the present invention. However, as those skilled in the art will appreciate, the present invention may be implemented without following these specific details.

[0057] It should be understood that when describing the structure of a component, when a layer or a region is referred to as being "on" or "over" another layer or another region, it may mean that it is directly on the other layer or another region, or that other layers or regions are included between it and the other layer or another region. Moreover, if the component is turned over, the layer or a region will be "below" or "beneath" another layer or another region.

[0058] Figure 1 , Figure 2 , Figure 3 1 and 2 respectively show a cross-sectional schematic diagram and a top view of an inertial sensor along the X direction and the Y direction according to the first embodiment of the present invention, Figure 3 and Figure 4 1 and 2 show a schematic cross-sectional view and a top view of another inertial sensor according to the first embodiment of the present invention. The inertial sensor includes a substrate 11, a wiring layer 12, a first movable mass block 13, a second movable mass block 14, a first anchor point 15, a second anchor point 16, and a first elastic element 17 and a second elastic element 20.

[0059] For ease of description, in the present invention, the extension direction of the elastic element is recorded as the Y-axis direction, the direction perpendicular to the Y-axis direction and located in the plane where the mass block is located is recorded as the X-axis direction, and the direction perpendicular to the plane where the mass block is located is recorded as the Z-axis direction.

[0060] The first anchor point 15 and the second anchor point 16 are respectively fixed on the wiring layer 12 , and the first anchor point 15 and the second anchor point 16 are adjacent to each other and do not overlap each other.

[0061] As a non-limiting example, Figure 1-Figure 3 As shown, the first anchor point 15 and the second anchor point 16 extend parallel to the Y direction; as another non-limiting example, Figure 4 and Figure 5 As shown, the first anchor point 15 and the second anchor point 16 extend in parallel along the X direction.

[0062] The first anchor point 15 and the second anchor point 16 are used to support the first movable mass block 13 and the second movable mass block 14 above the substrate 11, respectively. Specifically, the first anchor point 15 is connected to the side wall of the first movable mass block 13 through the first elastic element 17, so that the first movable mass block 13 is floated above the substrate 11, and the length direction of the first elastic element 17 coincides with the center line of the first anchor point 15; similarly, the second anchor point 16 is connected to the side wall of the second movable mass block 14 through the second elastic element 20, so that the second movable mass block 14 is floated above the substrate 11, and the length direction of the second elastic element 20 coincides with the center line of the second anchor point 16. The first elastic element 17 and the second elastic element 20 can be springs or springs or equivalent components. Among them, the connection method between the mass block and the substrate belongs to the common knowledge of those skilled in the art and will not be described in detail here.

[0063] The first movable mass block 13 and the second movable mass block 14 extend along the XY plane respectively, and the first movable mass block 13 and the second movable mass block 14 are sequentially floated above the substrate 11, so the first movable mass block 13 and the second movable mass block 14 are moved in a direction perpendicular to the substrate 11 (for example, Figure 1 The Z-axis direction in the image is set relative to the image.

[0064] In order to detect the acceleration in the Z-axis direction, a detection electrode is provided on the first movable mass block 13, and the detection electrode and the second movable mass block 14 constitute a differential capacitor structure. The acceleration in the Z-axis direction can be obtained by detecting the change in the capacitance value of the capacitor. Specifically, the inertial sensor of this embodiment includes at least a first detection electrode 18A located on the first sub-mass block 13A and a second detection electrode 18B located on the second sub-mass block 13B. The first detection electrode 18A and the third sub-mass block 14A constitute a first detection capacitor, and the second detection electrode 18B and the fourth sub-mass block 14B constitute a second detection capacitor. The capacitance change difference between the first detection capacitor and the second detection capacitor is detected by an external circuit, and the corresponding acceleration in the Z-axis direction can be obtained. Among them, the first detection electrode 18A and the second detection electrode 18B can adopt a capacitor plate structure well known to those skilled in the art.

[0065] In a preferred embodiment, if Figure 3As shown, the first detection electrode 18A and the second detection electrode 18B are symmetrically arranged with respect to the center line of the first anchor point 15 and the second anchor point 16 .

[0066] In addition, with the first elastic element 17 as the boundary, the masses on both sides of the first movable mass block 13 are not equal, that is, the masses of the first sub-mass block 13A and the second sub-mass block 13B of the first movable mass block 13 located on both sides of the first elastic element 17 in the X-axis direction are not equal; similarly, with the second elastic element 20 as the boundary, the masses on both sides of the second movable mass block 14 are not equal, that is, the masses of the third sub-mass block 14A and the fourth sub-mass block 14B of the second movable mass block 14 located on both sides of the second elastic element 20 in the X-axis direction are not equal, so as to ensure that when there is acceleration in the Z-axis direction, the first movable mass block 13 and the second movable mass block 14 form a "seesaw" effect.

[0067] In a specific embodiment of the present invention, Figure 1 and Figure 3 As shown, the areas of the first sub-mass block 13A and the second sub-mass block 13B are not equal, so the corresponding masses are different; the areas of the third sub-mass block 14A and the fourth sub-mass block 14B are not equal, so the corresponding masses are different. For example, the area of ​​the first sub-mass block 13A is larger than the area of ​​the second sub-mass block 13B, and the third sub-mass block 14A is smaller than the fourth sub-mass block 14B. Therefore, when there is an acceleration in the Z-axis direction, the first sub-mass block 13A and the second sub-mass block 13B perform a "seesaw" motion around the elastic element connected thereto; the third sub-mass block 14A and the fourth sub-mass block 14B perform a "seesaw" motion around the elastic element connected thereto. In addition, the first movable mass block 13 and the second movable mass block 14 are arranged in an asymmetrical opposite manner, that is, the centers of mass of the first movable mass block 13 and the second movable mass block 14 are respectively located on both sides of the elastic element. When there is acceleration in the Z-axis direction, one side of the first movable mass block 13 and the second movable mass block 14 will move relative to each other, and the other sides of the first movable mass block 13 and the second movable mass block 14 will move in opposite directions to ensure that the detection electrode on the first movable mass block 13 and the second movable mass block 14 form a differential capacitance structure.

[0068] In an optional embodiment, the masses of the second sub-mass block 13B and the fourth sub-mass block 14B are equal. Figure 1 and Figure 3 As shown, the areas of the second sub-mass block 13B and the fourth sub-mass block 14B are equal, which not only ensures that the first movable mass block 13 and the second movable mass block 14 form a seesaw effect when there is external acceleration in the Z-axis direction, but also reduces the process difficulty.

[0069] In addition, the inertial sensor further includes an insulating layer 19 located between the first movable mass block 13 and the detection electrode. The insulating layer 19 is, for example, Al2O3 or Si3N4, and plays a role of insulation and fumigation protection.

[0070] Figure 6 and Figure 7 Schematic diagrams of the structure of the inertial sensor according to the first embodiment of the present invention when subjected to acceleration in the Z-axis direction are shown respectively.

[0071] like Figure 6 As shown, when there is an acceleration g downward along the Z axis, due to the unequal weights on both sides of the first movable mass block 13 and the second movable mass block 14, the distance between the first sub-mass block 13A and the third sub-mass block 14A increases, and the distance between the second sub-mass block 13B and the fourth sub-mass block 14B decreases, so that the first detection capacitor and the second detection capacitor constitute a differential capacitor structure.

[0072] like Figure 7 As shown, when there is an acceleration g along the Z-axis, due to the unequal weights on both sides of the first movable mass block 13 and the second movable mass block 14, the distance between the first sub-mass block 13A and the third sub-mass block 14A decreases, and the distance between the second sub-mass block 13B and the fourth sub-mass block 14B increases, so that the first detection capacitor and the second detection capacitor constitute a differential capacitor structure.

[0073] The changes of the first detection capacitor and the second detection capacitor are completely opposite, and together they constitute a differential capacitor structure. By detecting the difference in capacitance change between the first detection capacitor and the second detection capacitor, the magnitude of the acceleration in the Z-axis direction can be obtained.

[0074] In this embodiment, the inertial sensor includes two layers of movable mass blocks, and the detection electrode is arranged on the first layer of movable mass blocks, and the detection electrode and the second layer of movable mass blocks constitute a differential capacitor structure. When there is an acceleration in the Z-axis direction, the capacitance change difference of the detection capacitor is obtained through an external circuit, and the corresponding acceleration value can be obtained. The capacitance change difference of the detection capacitor of the inertial sensor of the embodiment of the present invention is twice the capacitance change difference of the inertial sensor of the single-layer movable mass block under the same area, which improves the sensitivity of the inertial sensor without increasing the area of ​​the inertial sensor.

[0075] Figure 8 FIG. 4 is a cross-sectional schematic diagram showing an inertial sensor according to a second embodiment of the present invention. Figure 8 As shown, the inertial sensor of this 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 .

[0076] The first anchor point 25 and the second anchor point 26 are respectively fixed on the wiring layer of the substrate 21, and the first anchor point 25 and the second anchor point 26 are adjacent and do not overlap each other. The first anchor point 25 and the second anchor point 26 are used to support the first movable mass block 23 and the second movable mass block 24 above the substrate 21 respectively. Specifically, the first anchor point 25 is connected to the side wall of the first movable mass block 23 through the first elastic elements (not shown in the figure) on both sides thereof, so that the first movable mass block 23 is floated above the substrate 21, and the length direction of the first elastic element coincides with the center line of the first anchor point 25; similarly, the second anchor point 26 is connected to the side wall of the second movable mass block 24 through the second elastic elements (not shown in the figure) on both sides thereof, so that the second movable mass block 24 is floated 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 can be springs or springs or equivalent components. Among them, the connection method between the mass block and the substrate belongs to the common knowledge of those skilled in the art and will not be described in detail here.

[0077] In order to detect the acceleration in the Z-axis direction, a detection electrode is provided on the first movable mass block 23, and the detection electrode and the second movable mass block 24 constitute a differential capacitor structure. The acceleration in the Z-axis direction can be obtained by detecting the change in the capacitance value of the capacitor. Specifically, the inertial sensor of this embodiment includes at least a first detection electrode 28A located on the first sub-mass block 23A and a second detection electrode 28B located on the second sub-mass block 23B. The first detection electrode 28A and the third sub-mass block 24A constitute a first detection capacitor, and the second detection electrode 28B and the fourth sub-mass block 24B constitute a second detection capacitor. The capacitance change difference between the first detection capacitor and the second detection capacitor is detected by an external circuit, and the corresponding acceleration in the Z-axis direction can be obtained. Among them, the first detection electrode 28A and the second detection electrode 28B can adopt a capacitor plate structure well known to those skilled in the art.

[0078] In addition, the inertial sensor further includes an insulating layer 29 located between the first movable mass block 23 and the detection electrode. The insulating layer 29 is, for example, Al2O3 or Si3N4, and plays a role of insulation and fumigation protection.

[0079] The difference between the inertial sensor of this embodiment and the inertial sensor of the first embodiment is that the areas of the first sub-mass block 23A, the second sub-mass block 23B, the third sub-mass block 24A and the fourth sub-mass block 24B in this embodiment are equal. Therefore, in order to make the masses on both sides of the first movable mass block 23 and the second movable mass block 24 unequal, a weight-reducing hole is provided on at least one side of the first movable mass block 23 and the second movable mass block 24. The weight-reducing hole can be multiple and distributed in an array. The weight-reducing hole can be a through hole formed by etching during manufacturing; it can also be a blind hole, which can be etched by adding a layer of mask. In another embodiment, a counterweight block can be added on at least one side of the first movable mass block 23 and the second movable mass block 24 so that the masses on both sides of the first movable mass block 23 and the second movable mass block 24 are unequal.

[0080] like Fig. 9 The schematic diagram of the structure of the mass block of the inertial sensor according to the second embodiment of the present invention is shown. For example, the first sub-mass block 23A, the second sub-mass block 23B, the third sub-mass block 24A and the fourth sub-mass block 24B are all provided with weight reduction holes 41, and there can be multiple weight reduction holes 41 distributed in an array, and the mass of each weight reduction block can be changed by controlling the number of weight reduction holes on each mass block. Fig. 9 As shown, there are 9 weight-reducing holes 41 on the first sub-mass block 23A, 16 weight-reducing holes 41 on the second sub-mass block 23B and the fourth sub-mass block 24B, and 36 weight-reducing holes 41 on the third sub-mass block 24A. The mass of the first sub-mass block 23A is greater than the mass of the second sub-mass block 23B, the mass of the third sub-mass block 24A is less than the mass of the fourth sub-mass block 24B, and the masses of the second sub-mass block 23B and the fourth sub-mass block 24B are equal.

[0081] It should be noted that the shape, number and combination relationship of the weight-reducing holes on the mass block of the present embodiment are not limited thereto, and those skilled in the art may select the number of weight-reducing holes on the mass block according to specific circumstances.

[0082] Fig.10 FIG. 4 is a schematic cross-sectional view of an inertial sensor according to a third embodiment of the present invention. Fig.10 As shown, 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 .

[0083] The first anchor point 35 and the second anchor point 36 are respectively fixed on the substrate 31, and the first anchor point 35 and the second anchor point 36 are adjacent and do not overlap each other. The first anchor point 35 and the second anchor point 36 are used to support the first movable mass block 33 and the second movable mass block 34 above the substrate 31 respectively. Specifically, the first anchor point 35 is connected to the side wall of the first movable mass block 33 through the first elastic elements (not shown in the figure) on both sides thereof, so that the first movable mass block 33 is floated above the substrate 31, and the length direction of the first elastic element coincides with the center line of the first anchor point 35; similarly, the second anchor point 36 is connected to the side wall of the second movable mass block 34 through the second elastic elements (not shown in the figure) on both sides thereof, so that the second movable mass block 34 is floated 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 can be springs or springs or equivalent components. Among them, the connection method between the mass block and the substrate belongs to the common knowledge of those skilled in the art and will not be described in detail here.

[0084] In order to detect the acceleration in the Z-axis direction, a detection electrode is provided on the first movable mass block 33, and the detection electrode and the second movable mass block 34 constitute a differential capacitor structure. The acceleration in the Z-axis direction can be obtained by detecting the change in the capacitance value of the capacitor. Specifically, the inertial sensor of this embodiment includes at least a first detection electrode 38A located on the first sub-mass block 33A and a second detection electrode 38B located on the second sub-mass block 33B. The first detection electrode 38A and the third sub-mass block 34A constitute a first detection capacitor, and the second detection electrode 38B and the fourth sub-mass block 34B constitute a second detection capacitor. The capacitance change difference between the first detection capacitor and the second detection capacitor is detected by an external circuit, and the corresponding acceleration in the Z-axis direction can be obtained. Among them, the first detection electrode 38A and the second detection electrode 38B can adopt a capacitor plate structure well known to those skilled in the art.

[0085] In addition, the inertial sensor further includes an insulating layer 39 located between the first movable mass block 33 and the detection electrode. The insulating layer 39 is, for example, Al2O3 or Si3N4, and plays a role of insulation and fumigation protection.

[0086] The difference between the inertial sensor of the present embodiment and the inertial sensor of the first embodiment lies in that the areas of the second sub-mass block 33B and the fourth sub-mass block 34B in the present embodiment are not equal, that is, the masses of the second sub-mass block 33B and the fourth sub-mass block 34B are not equal, so that there is a mass difference on both sides of the first movable mass block 33 and the second movable mass block 34, thereby improving the sensitivity of the mass block deflection and improving the sensitivity of the inertial sensor.

[0087] Figures 11 to 21Schematic cross-sectional views of various stages of a method for manufacturing an inertial sensor according to a fourth embodiment of the present invention are shown respectively. The manufacturing method of the present invention is described below by taking the inertial sensor in the first embodiment as an example.

[0088] like Fig.11 As shown, doped polysilicon is deposited on the substrate 101, and patterned by photolithography and etching processes to form a wiring layer 102. Preferably, the substrate 101 can 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, a substrate with a crystal orientation of <100> N-type silicon substrate.

[0089] In the deposition step, doped polysilicon may be deposited on the substrate 101 by low pressure chemical vapor deposition (LP-CVD) at a deposition temperature of 570° C. to 630° C. The polysilicon thickness ranges from 0.4 to 1 μm. Further, the polysilicon thickness is 0.8 μm.

[0090] 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 using a photolithography process. The resist layer is used as a mask, and a selective etchant is used to remove the exposed portion of the polysilicon. Due to the selectivity of the etching, the etching can stop on the surface of the substrate 101. After etching, the resist layer can be removed by ashing or dissolving in a solvent.

[0091] After patterning, the remaining part of the polysilicon forms 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 opening pattern in the mask.

[0092] The wiring layer 102 is used to realize the electrical connection between the anchor point and the external circuit in the subsequent steps. Further, in the subsequent steps, the first anchor point and the second anchor point will be realized above the wiring layer 102A.

[0093] like Fig.12 As shown, a first sacrificial layer 103 is formed on the 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 of silicon dioxide can be formed on the semiconductor substrate 101 by low pressure chemical vapor deposition (LP-CVD) or plasma enhanced chemical vapor deposition (PECVD) and the like, and the thickness of the first sacrificial layer 103 ranges from 1.2 to 1.8 microns. Furthermore, the thickness of the first sacrificial layer is 1.2 microns. Preferably, the surface of the first sacrificial layer 103 is planarized by chemical mechanical polishing (CMP) or isotropic etching after coating.

[0094] As described below, the first sacrificial layer 103 is not only used to provide interlayer insulation for a conductor layer to be formed subsequently, but at least a portion of the first sacrificial layer 103 is removed in a subsequent step as a sacrificial layer to form a cavity.

[0095] Then, the above-mentioned photolithography and etching processes are used for patterning, thereby forming a through hole 103A that passes through the first sacrificial layer 103 and reaches the wiring layer 102 located on the substrate 101, and the through hole 103A exposes at least a portion of the surface of the wiring layer 102A. Fig.13 shown.

[0096] In the etching process of this step, a suitable etchant can be selected, and the etchant's property of selectively removing the exposed portion of the first sacrificial layer 103 from the substrate 101 can be utilized so that the etching stops at the surface of the substrate 101. Therefore, through the selective etching of the etchant, the etching depth can be controlled so that the through hole 103A just passes through the first sacrificial layer 103. In an alternative embodiment, the etching depth is controlled by controlling the etching time so that the through hole penetrates the first sacrificial layer 103 and reaches the surface of the wiring layer 102A.

[0097] like Fig.14 As shown, polysilicon is epitaxially grown on the first sacrificial layer 103 to form a first structure layer 104 .

[0098] For example, low pressure chemical vapor deposition (LP-CVD) or plasma enhanced chemical vapor deposition (PECVD) can be used to epitaxially grow polysilicon on the first sacrificial layer 103 to form the first structural layer 104. The thickness of the first structural layer 104 ranges from 10 to 25 microns. Further, the thickness of the first structural layer 104 is 10 microns.

[0099] Furthermore, the first anchor point and the second anchor point (not shown) are formed above the wiring layer 102A while forming the first structure layer 104. Furthermore, the through hole 103A is filled while forming the first structure layer 104 to form the lower half structure of the first anchor point and the second anchor point.

[0100] like Fig.15As shown, an insulating layer 105 is formed on the first structural layer 104. The insulating layer 105 is composed of an insulating material, such as an insulating material such as silicon dioxide, aluminum oxide (Al2O3) or silicon nitride (Si3N4), which plays an insulating and fumigation protection role and serves as a deep groove etching protection layer. The insulating material can be deposited on the surface of the first structural layer 104 by thermal oxidation, low pressure chemical vapor deposition (LP-CVD) or plasma enhanced chemical vapor deposition (PECVD), and patterned by photolithography and etching processes, and then the insulating layer 105 is formed on the surface of the first structural layer 104. The insulating layer 105 partially covers the first structural layer 104. Further, the thickness of the insulating layer 105 ranges from 0.1 to 0.3 microns. Further, the thickness of the insulating layer 105 is 0.1 microns.

[0101] like Fig.16 As shown, polysilicon is epitaxially grown on the insulating layer 105, and a photolithography or etching process is used to form the detection electrode 106. The detection electrode 106 is formed not only on the surface of the insulating layer 105, but also on the first structure layer 104. Further, the detection electrode 106 formed on the insulating layer 105 is symmetrical about the central axis of the through hole 103A, and the orthographic projection of the detection electrode 106 formed on the first structure layer 104 on the substrate 101 is located in the through hole 103A.

[0102] For example, low pressure chemical vapor deposition (LP-CVD) or plasma enhanced chemical vapor deposition (PECVD) can be used to epitaxially grow polysilicon on the insulating layer 105, and then patterned by photolithography and etching processes to form the detection electrode 106. Further, the thickness of the detection electrode 106 ranges from 0.4 to 1 micron. Furthermore, the thickness of the detection electrode 106 is 0.8 micron.

[0103] 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 using a photolithography process. The resist layer is used as a mask, and a selective etchant is used to remove the exposed portion of the polysilicon. Due to the selectivity of the etching, the etching can stop on the surface of the insulating layer 105 or the first structural layer 104. After etching, the resist layer can be removed by ashing or dissolving in a solvent.

[0104] After patterning, the remaining part of the polysilicon forms the detection 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 opening pattern in the mask.

[0105] like Fig.17As shown, 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 can be formed on the exposed surfaces of the insulating layer 105, the detection electrode 106 and the first structural layer 104 by methods such as low-pressure chemical vapor deposition (LP-CVD) or plasma enhanced chemical vapor deposition (PECVD). The thickness of the second sacrificial layer 107 ranges from 1.2 to 1.8 microns. Furthermore, the thickness of the second sacrificial layer 107 is, for example, 1.6 microns. Preferably, the surface of the second sacrificial layer 107 is planarized by chemical mechanical polishing (CMP) or isotropic back etching after coating.

[0106] As described below, the second sacrificial layer 107 is not only used to provide interlayer insulation for a conductor layer to be formed subsequently, but at least a portion of the second sacrificial layer 107 is removed in a subsequent step as a sacrificial layer to form a cavity.

[0107] Then, the above-mentioned photolithography and etching processes are used for patterning, thereby forming a through hole 107A that passes through the second sacrificial layer 107 and reaches the detection electrode 106. Fig.18 shown.

[0108] In the etching process of this step, a suitable etchant can be selected, and the etching can be stopped at the surface of the detection electrode 106 by utilizing the property of the etchant to selectively remove the exposed portion of the second sacrificial layer 107 for the detection electrode 106. Therefore, through the selective etching of the 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 etching depth is controlled by controlling the etching time so that the through hole penetrates the second sacrificial layer 107 to reach the surface of the detection electrode 106.

[0109] The etching process of the patterning step is, for example, anisotropic etching. The pattern of the through hole formed in the second sacrificial layer 107 is substantially the same as the shape of the opening pattern in the mask.

[0110] like Fig.19 As shown, polysilicon is epitaxially grown on the second sacrificial layer 107, thereby forming a second structure layer 108. The second structure layer 108 is not only formed on the surface of the second sacrificial layer 107, but also fills the through hole and reaches the detection electrode 106 through the through hole.

[0111] For example, low pressure chemical vapor deposition (LP-CVD) or plasma enhanced chemical vapor deposition (PECVD) can be used to epitaxially grow polysilicon on the second sacrificial layer 107 to form the second structure layer 108. The thickness of the second structure layer 108 is in the range of 10 to 25 microns. Further, the thickness of the second structure layer 108 is, for example, 10 microns.

[0112] Furthermore, forming the second structure layer 108 further includes filling the through hole 107A to form an upper half of the second anchor point on the detection electrode 106 to form a complete second anchor point.

[0113] Next, the first structure layer 104 and the second structure layer 108 are patterned by photolithography and etching processes to form a motion mass pattern and an elastic element pattern, wherein the motion mass pattern has a gap around it to expose the surfaces of the first sacrificial layer 103 and the second sacrificial layer 107. Fig. 20 As shown, the first structure layer 104 and the second structure layer 108 are patterned by photolithography and etching processes, thereby forming a first sub-mass block 141 , a second sub-mass block 142 , a third sub-mass block 143 and a fourth sub-mass block 144 .

[0114] In the etching process of this step, the insulating layer 105 is used as a deep trench etching protection layer, and an etchant is used to selectively remove the exposed portions of the first structure layer 104, the second structure layer 108, and the second sacrificial layer 107 to form a plurality of deep trenches 108A and deep trenches 108B. The deep trenches 108A and deep trenches 108B can be used to remove the sacrificial layer by gas phase fumigation in the subsequent process steps.

[0115] Furthermore, by selectively etching a portion of the second sub-mass block 142, the third sub-mass block 143 and the fourth sub-mass block 144 through the deep groove 108B, 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 when there is an external acceleration in the Z-axis direction, the first sub-mass block 141 and the second sub-mass block 142 can form a seesaw effect; the third sub-mass block 143 and the fourth sub-mass block 144 have different sizes, and then the third sub-mass block 143 and the fourth sub-mass block 144 have different masses, and when there is an external acceleration in the Z-axis direction, the third sub-mass block 143 and the fourth sub-mass block 144 can form a seesaw effect.

[0116] In an optional embodiment, if the mass of the first to fourth sub-mass blocks 141-144 is changed by providing a weight-reducing hole on at least one of the first to fourth sub-mass blocks 141-144, it is not necessary to form the deep groove 108B in this step. The weight-reducing holes can be multiple and distributed in an array. The weight-reducing holes can be through holes formed by etching during manufacturing; or blind holes can be etched by adding a mask.

[0117] In another embodiment, the masses of the first to fourth sub-mass blocks 141 - 144 may be changed by adding a counterweight block to at least one of the first to fourth sub-mass blocks 141 - 144 .

[0118] In an optional embodiment, the mass of the second sub-mass block 142 is less than the mass of the fourth sub-mass block 144. Fig.11 After the first structure layer 104 is formed by epitaxially growing polysilicon, it is patterned by photolithography and etching processes to form a first movable mass block pattern.

[0119] like Fig.21 As shown, the second sacrificial layer 107 between the moving mass block patterns and the first sacrificial layer 103 between the moving mass block and the substrate are then etched away by hydrofluoric acid (HF) vapor fumigation, so that the moving mass block patterns are released to form a movable mass block of the device substrate 101.

[0120] The etching step adopts isotropic etching, for example, using gaseous HF as an etchant. The second structure layer 108 is used as a mask, and the etchant reaches the exposed surfaces of the first sacrificial layer 103 and the second sacrificial layer 107 via the multiple deep grooves in the second structure layer 108. Due to the selectivity of the etching, the etching can selectively remove the first portion of the first sacrificial layer 103 exposed at the bottom of the deep groove relative to the second structure layer 108, the first structure layer 104 and the detection electrode 106, and further laterally remove the second portion of the first sacrificial layer 103 adjacent to the first portion; the etching can also selectively laterally remove the third portion of the second sacrificial layer 107 exposed to the sidewalls of the multiple deep grooves.

[0121] In summary, the inertial sensor of the above embodiment includes two layers of movable mass blocks, and the detection electrode is arranged on the first layer of movable mass blocks, and the detection electrode and the second layer of movable mass blocks constitute a differential capacitor structure. When there is an acceleration in the Z-axis direction, the capacitance change difference of the detection capacitor is obtained through an external circuit to obtain the corresponding acceleration value. The capacitance change difference of the detection capacitor of the inertial sensor of the embodiment of the present invention is twice the capacitance change difference of the inertial sensor of the single-layer movable mass block under the same area, which improves the sensitivity of the inertial sensor.

[0122] In a preferred embodiment, the areas of the first movable mass block and the second movable mass block are equal, and a weight-reducing hole is provided on at least one side of the first movable mass block and the second movable mass block. The weight-reducing holes may be multiple and distributed in an array. This not only ensures that the first movable mass block and the second movable mass block form a seesaw effect when there is an acceleration in the Z-axis direction in the outside world, but also eliminates the need for deep groove etching to change the areas of the first movable mass block and the second movable mass block when forming the movable mass block pattern, thereby reducing the process difficulty.

[0123] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0124] According to the embodiments of the present invention as described above, these embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and changes can be made based on the above description. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can make good use of the present invention and the modified use based on the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. An inertial sensor, comprising: substrate; A first movable mass block is located above the substrate; a second movable mass block, located above the first movable mass block; as well as a detection electrode disposed on the first movable mass block, wherein the detection electrode and the second movable mass block form a detection capacitor, The inertial sensor further includes: a first anchor point, a second anchor point, at least one first elastic element and a second elastic element extending along a first direction, and a wiring layer located on the substrate, wherein the first elastic element is used to connect the first anchor point and the first movable mass block, the second elastic element is used to connect the second anchor point and the second movable mass block, and the first anchor point and the second anchor point are fixed on the wiring layer.

2. The inertial sensor according to claim 1, characterized in that: The first anchor point and the second anchor point are arranged in parallel along the first direction.

3. The inertial sensor according to claim 1, characterized in that: The first anchor point and the second anchor point are arranged in parallel along a second direction perpendicular to the first direction. 4 . The inertial sensor according to claim 2 , wherein 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.

5. The inertial sensor according to claim 1, wherein: The masses of the first movable mass block located on two sides of the first elastic element are unequal, and the masses of the second movable mass block located on two sides of the second elastic element are unequal.

6. The inertial sensor according to claim 5, wherein: The mass of the first movable mass block located on the left side of the first elastic element is equal to the mass of the second movable mass block located on the left side of the second elastic element, or The mass of the first movable mass block located on the right side of the first elastic element is equal to the mass of the second movable mass block located on the right side of the second elastic element.

7. The inertial sensor according to claim 5, wherein: The first movable mass block is asymmetrically arranged with respect to the first elastic element, and the second movable mass block is asymmetrically arranged with respect to the second elastic element.

8. The inertial sensor according to any one of claims 5 to 7, wherein: At least one side of each of the first movable mass block and the second movable mass block is provided with a weight-reducing hole.

9. The inertial sensor according to any one of claims 5 to 7, wherein: At least one side of each of the first movable mass block and the second movable mass block is provided with a counterweight block.

10. The inertial sensor according to claim 8, wherein: The weight-reducing holes include through holes and / or blind holes.

11. The inertial sensor according to claim 1, wherein: The detection electrodes include at least 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 constitute a differential capacitor structure.

12. The inertial sensor according to claim 11, characterized in that The first detection electrode and the second detection electrode are symmetrical about a midline of the first anchor point and / or the second anchor point.

13. The inertial sensor according to claim 1, wherein: The invention also includes an insulating layer located between the detection electrode and the first movable mass.

14. The inertial sensor according to claim 1, characterized in that: The thickness of the first movable mass block and the second movable mass block are respectively 10-25 microns.

15. The inertial sensor according to claim 1, characterized in that: The thickness of the detection electrode and the wiring layer are 0.4-1 micrometer respectively.

16. The inertial sensor according to claim 13, characterized in that: The thickness of the insulating layer is 0.1-0.3 microns.

17. A method for manufacturing an inertial sensor, characterized in that: include: forming a wiring layer on a substrate; forming a first sacrificial layer on the substrate and the wiring layer; forming a first structural layer on the first sacrificial layer; forming a detection electrode on the first structural layer; forming a second sacrificial layer on the first structural layer and the detection electrode; forming a second structural layer on the second sacrificial layer; Graphically forming the first structural layer and the second structural layer into a motion mass block pattern; as well as removing the first sacrificial layer and the second sacrificial layer to form a first movable mass block and a second movable mass block, The first movable mass block and the second movable mass block are floated on the substrate, and the detection electrode and the second movable mass block form a detection capacitor. Wherein, the manufacturing method further comprises: Before forming the first structural layer, Etching on the upper surface of the first sacrificial layer to form a first through hole, wherein the first through hole exposes at least a portion of the surface of the wiring layer; and Filling the first through hole to form a first anchor point and a portion of a second anchor point; Before forming the second structural layer, Etching is performed on the upper surface of the second sacrificial layer to form a second through hole, wherein the second through hole exposes at least a portion of the detection electrode, and filling the second through hole to form another part of the structure of the second anchor point, and patterning the first structure layer and the second structure layer to form a first elastic element and a second elastic element extending along a first direction, respectively, The first elastic element is used to connect the first anchor point and the first movable mass block, and the second elastic element is used to connect the second anchor point and the second movable mass block.

18. The manufacturing method according to claim 17, wherein: Before forming the detection electrode on the first structure layer, the method further includes: forming an insulating layer on an upper surface of the first structural layer; and The insulating layer is patterned so that the insulating layer partially covers the first structural layer.

19. The manufacturing method according to claim 18, wherein: The forming of the first movable mass block and the second movable mass block comprises: The insulating layer is used as a deep trench etching protection layer, forming a plurality of first deep grooves and second deep grooves extending from the upper surface of the second structural layer to the upper surface of the first sacrificial layer; and An isotropic etching is performed through the plurality of first deep trenches and the second deep trenches to laterally remove at least a portion of the first sacrificial layer and the second sacrificial layer.

20. The manufacturing method according to claim 17, characterized in that: The first anchor point and the second anchor point are arranged in parallel along the first direction.

21. The manufacturing method according to claim 17, characterized in that: The first anchor point and the second anchor point are arranged in parallel along a second direction perpendicular to the first direction.

22. The manufacturing method according to claim 20 or 21, characterized in that: 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.

23. The manufacturing method according to claim 17, wherein: The masses of the first movable mass block located on two sides of the first elastic element are unequal, and the masses of the second movable mass block located on two sides of the second elastic element are unequal.

24. The manufacturing method according to claim 23, wherein: The method also includes patterning at least one side of the first movable mass block and the second movable mass block to form a lightening hole.

25. The manufacturing method according to claim 24, wherein: The weight-reducing holes include through holes and / or blind holes.

26. The manufacturing method according to claim 23, wherein: The method further includes forming a counterweight on at least one side of the first movable mass block and the second movable mass block.

27. The manufacturing method according to claim 17, wherein: The thickness of the first structural layer and the second structural layer are respectively 10-25 microns.

28. The manufacturing method according to claim 17, wherein: The thickness of the detection electrode and the wiring layer are 0.4-1 micrometer respectively.

29. The manufacturing method according to claim 18, wherein: The thickness of the insulating layer is 0.1-0.3 microns.

30. The manufacturing method according to claim 17, wherein: The thickness of the first sacrificial layer and the second sacrificial layer is 1.2-1.8 microns.

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