CN112014596B - Accelerometer and manufacturing method thereof - Google Patents
Accelerometer and manufacturing method thereof Download PDFInfo
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- CN112014596B CN112014596B CN201910464711.7A CN201910464711A CN112014596B CN 112014596 B CN112014596 B CN 112014596B CN 201910464711 A CN201910464711 A CN 201910464711A CN 112014596 B CN112014596 B CN 112014596B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
- G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
- G01P15/0802—Details
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
- G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
- G01P15/12—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values by alteration of electrical resistance
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Abstract
The application discloses an accelerometer and a method of making the same. Wherein the accelerometer includes a structural layer, the structural layer including: the frame structure is provided with an accommodating space; the fixed supporting beam is arranged in the accommodating space; the mass block is arranged on the clamped beam; a detection circuit for outputting an electrical signal corresponding to at least one axial acceleration based on the force generated by the mass, wherein the detection circuit comprises: the at least two strain resistors are respectively arranged at one end or two ends of the clamped beam close to the mass block; the at least two matching resistors are arranged on the mass block; wherein, the at least two strain resistors and the at least two matching resistors form at least one group of Wheatstone bridges. According to the scheme, the cross coupling interference of the acceleration can be weakened.
Description
Technical Field
The present application relates to the field of sensing technologies, and in particular, to an accelerometer and a method for manufacturing the same.
Background
In recent years, accelerometers, particularly Micro-Electro-Mechanical systems (MEMS) accelerometers, are widely used in the fields of aerospace, consumer electronics, automotive electronics, and the like. With the rapid expansion of various applications, the performance requirements of accelerometers are also increasing. However, the performance of the accelerometer is limited to a large extent due to the problem of cross-coupling interference of the existing accelerometer. So-called cross-coupling interference, that is, the electrical signal related to the axial acceleration output by the accelerometer has signal components of other axial acceleration interference, for example, for a three-axis accelerometer, the Z axial acceleration and the Y axial acceleration affect the electrical signal corresponding to the X axial acceleration to some extent, so that the X axial acceleration measured according to the electrical signal is not accurate enough, and the other axial accelerations are the same, so that the performance of the acceleration is limited.
Therefore, how to weaken or even eliminate cross-coupling interference is a very important issue for accelerometer design at present.
Disclosure of Invention
The technical problem mainly solved by the application is to provide the accelerometer and the manufacturing method thereof, which can weaken cross coupling interference of acceleration.
In order to solve the above problem, a first aspect of the present application provides an accelerometer, including a structural layer, the structural layer including:
the frame structure is provided with an accommodating space;
the fixed supporting beam is arranged in the accommodating space;
the mass block is arranged on the clamped beam, and when the accelerometer is subjected to acceleration, the mass block generates acting force on the clamped beam due to the acceleration;
the detection circuit is used for outputting an electric signal corresponding to at least one axial acceleration based on the acting force generated by the mass block; wherein the detection circuit comprises:
the strain resistors are respectively arranged at one end or two ends of the clamped beam, which are close to the mass block, and the strain resistors can cause resistance value change due to the acting force generated by the mass block;
the at least two matching resistors are arranged on the mass block;
the at least two strain resistors and the at least two matching resistors form at least one group of Wheatstone bridges, and each group of Wheatstone bridges is used for generating an electric signal corresponding to a target axial acceleration; the Wheatstone bridge generates the electrical signal when the accelerometer is subject to the target axial acceleration greater than the electrical signal generated when the accelerometer is subject to a non-target axial acceleration.
In order to solve the above problem, a second aspect of the present application provides a method for manufacturing an accelerometer, including:
providing a base layer;
manufacturing at least two strain resistors, at least two matching resistors and a lead for connecting the at least two strain resistors and the at least two matching resistors on the first surface of the base layer to manufacture a detection circuit; wherein the at least two matching resistors are located on the proof mass; the at least two strain resistors are respectively positioned at one end or two ends of the clamped beam close to the mass block; the at least two strain resistors and the at least two matching resistors are connected through the lead to form at least one group of Wheatstone bridges, and each group of Wheatstone bridges is used for generating an electric signal corresponding to a target axial acceleration; the Wheatstone bridge generates a greater electrical signal when the accelerometer is subject to the target axial acceleration than when the accelerometer is subject to a non-target axial acceleration;
etching a second surface of the base layer, which is opposite to the first surface, to form a mass block and a frame structure, wherein a gap is formed between the frame structure and the mass block;
and etching the first surface of the base layer to form a clamped beam, wherein the clamped beam is arranged in an accommodating space formed by the frame structure, and two ends of the clamped beam are respectively fixed on the frame structure.
In the above scheme, the accelerometer is provided with a strain resistor capable of sensing the acting force of the mass block on the clamped beam, and at least one group of Wheatstone bridges is formed by the strain resistor and the matching resistor on the mass block, wherein for each group of Wheatstone bridges, the influence of an electric signal generated when the acceleration of a non-target shaft is received on the electric signal generated when the acceleration of the target shaft is received is low or even negligible, so that no matter any axial acceleration is received, the electric signal output by the Wheatstone bridges basically comes from the target axial acceleration and is basically not interfered by the non-target axial acceleration of the Wheatstone bridges or is interfered by the non-target axial acceleration of the Wheatstone bridges to a low degree, so that the target axial acceleration can be directly calculated by using the electric signal output by the Wheatstone bridges, and cross coupling interference is reduced.
Drawings
FIG. 1a is a schematic top view of an embodiment of an accelerometer of the present application;
FIG. 1b is a schematic top view of an accelerometer of the present application;
FIG. 2a is a schematic diagram of a Wheatstone bridge according to an embodiment of the accelerometer of the present application;
FIG. 2b is a schematic diagram of another Wheatstone bridge configuration of an embodiment of the accelerometer of the present application;
FIG. 3 is a schematic diagram of yet another Wheatstone bridge according to an embodiment of the accelerometer of the present application;
FIG. 4 is a schematic diagram of a partial top view of another embodiment of an accelerometer of the present application;
FIGS. 5 a-5 d are schematic diagrams of top views of various embodiments of the accelerometer of the present application;
FIG. 6 is a schematic diagram of a side view of an embodiment of an accelerometer of the present application;
FIG. 7 is a schematic diagram of a side view of another embodiment of an accelerometer of the present application;
FIG. 8 is a schematic diagram of a top view of yet another embodiment of an accelerometer of the present application;
FIG. 9 is a schematic flow chart diagram illustrating one embodiment of a method for fabricating an accelerometer of the present application;
fig. 10a to 10i are schematic structural diagrams of an accelerometer manufactured by corresponding steps of the method for manufacturing an accelerometer according to the present application.
Detailed Description
The following describes in detail the embodiments of the present application with reference to the drawings attached hereto.
In the following description, for purposes of explanation and not limitation, specific details are set forth such as particular system structures, interfaces, techniques, etc. in order to provide a thorough understanding of the present application.
The term "and/or" herein is merely an association describing an associated object, meaning that three relationships may exist, e.g., a and/or B, may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship. A plurality or a plurality of the applications mentioned in the present application is to be understood as two or more.
Referring to fig. 1a, fig. 1a is a schematic top view of an accelerometer according to an embodiment of the present application. In this embodiment, the accelerometer 100 includes a structural layer 110, and the structural layer 110 includes a clamped beam 111, a mass 112, a frame structure 116, and a detection circuit 130.
The frame structure 116 forms a receiving space 1161 for receiving the clamped beam 111 and the mass 112. In particular, perimeter structure 116 surrounds mass 112 and clamped beam 111 with a gap 118 from mass 112. It is understood that the frame structure 116 may be, but is not limited to, a circular ring or a square ring (as shown in fig. 1 a).
The two ends 111b of the clamped beam 111 are fixed to the frame structure 116. It is understood that two ends 111b of the clamped beam 111 may be directly connected to the frame structure 116, for example, two ends 111b of the clamped beam 111 respectively extend to the frame structure 116 along the length direction away from the mass block 112; or clamped beam 111 may be coupled to frame structure 116 via other structures, such as isolation structure 117.
The mass block 112 is disposed on the clamped beam 111, specifically, in the middle of the clamped beam 111 (i.e., between two ends 111b connected to the frame structure). When accelerometer 100 is subjected to an acceleration, mass 112 exerts a force on clamped beam 111 due to the acceleration. The shape of the mass block 112 may be set according to actual requirements, as shown in fig. 1a, the mass block is configured as an i-shape, and in other embodiments, the mass block may also be configured as a rectangle or any other shape, which is not limited herein.
The detection circuit 130 is disposed on at least one of the clamped beam 111 and the mass 112, and is configured to output an electrical signal corresponding to at least one axial acceleration based on the acting force generated by the mass 112. It is understood that the axial acceleration may be a horizontal axial acceleration, or a vertical axial acceleration. Specifically, the detection circuit 130 may include several strain resistors 113 and matching resistors 114 electrically connected.
In this embodiment, the accelerometer is provided with the clamped beam with two ends fixed on the frame structure, and compared with the cantilever beam with one end fixed, the clamped beam with two ends fixed can reduce the degree of freedom of the motion of the mass block, so that when the accelerometer is subjected to a certain axial acceleration, the interference introduced to other axial directions can be weakened, and particularly when the accelerometer is subjected to an axial acceleration (such as a Z axis) perpendicular to the clamped beam, the interference introduced to other axial directions (such as an X axis and a Y axis) parallel to the plane where the clamped beam is located can be greatly weakened, so that the cross coupling interference is reduced.
To further reduce cross-coupling interference, the detection circuit 130 may generate an electrical signal corresponding to the axial acceleration by using a wheatstone bridge formed by the strain resistor 113 and the matching resistor 114. With continued reference to fig. 1a, in one embodiment, the detection circuit 130 includes at least two strain resistors 113, at least two matching resistors 114, and wires 115 for connecting the above resistors. The at least two matching resistors 114 are disposed on the mass block 112, and the resistance of the matching resistor 114 does not change along with the acceleration applied to the accelerometer. At least two strain resistors 113 are used for sensing the change of the acceleration, and therefore, the strain resistors 113 are respectively disposed on one end 111a or both ends 111a of the clamped beam 111 close to the mass block 112, and particularly, for facilitating the strain resistors 113 to better sense the change of the acceleration, the strain resistors 113 may be disposed at the contact position of the clamped beam 111 and the mass block 112, or disposed relatively close to the contact position. When the accelerometer 110 is subjected to an acceleration, the mass 112 generates a force on the clamped beam 111 due to the acceleration, and the strain resistor 113 can cause a resistance value change due to the force generated by the mass 112. It is understood that fig. 1a only schematically shows the positions and the routing of the strain resistors 113, the matching resistors 114 and the related wires 115, and that the resistors and the wires may be actually disposed at other positions on the mass block and the clamped beam and different routing may be provided according to the requirement.
Referring to fig. 2a, the at least two strain resistors 113 (as shown in fig. R11 and R12) and the at least two matching resistors 114 (as shown in fig. R21 and R22) are connected by the wires 115 on the mass block 112 and/or the clamped beam 111 to form at least one set of wheatstone bridges 120, and each set of wheatstone bridges 120 is used for measuring a target axial acceleration, i.e. for generating an electrical signal corresponding to the target axial acceleration. It is understood that the target axial acceleration may be a horizontal axial acceleration, or a vertical axial acceleration. Specifically, when there is only one wheatstone resistor 120 composed of the at least two strain resistors 113 and the at least two matching resistors 114, the accelerometer 110 is a single-axis accelerometer for measuring single axial acceleration; when there are multiple sets, such as two or three sets, of the wheatstone resistors 120 formed by the at least two strain resistors 113 and the at least two matching resistors 114, the accelerometer 110 is a multi-axis accelerometer for measuring multi-axial acceleration, such as a two-axis accelerometer and a three-axis accelerometer.
In this embodiment, the arrangement and connection relationship of the strain resistor 113 and the matching resistor 114 may be such that the electrical signal generated by the wheatstone bridge 120 when the accelerometer 100 is subjected to the target axial acceleration of the wheatstone bridge 120 is greater than the electrical signal generated when the accelerometer 100 is subjected to the non-target axial acceleration of the wheatstone bridge 120, so that for each group of wheatstone bridges 120, the electrical signal generated when the accelerometer 100 is subjected to the non-target axial acceleration has a relatively low or negligible effect on the electrical signal generated when the accelerometer is subjected to the target axial acceleration, and therefore, regardless of any axial acceleration, the electrical signal output by the wheatstone bridge is substantially from the target axial acceleration and is substantially not or to a relatively low degree interfered by the non-target axial acceleration of the wheatstone bridge, so that the target axial acceleration can be directly calculated by using the electrical signal output by the wheatstone bridge, and the cross-coupling interference is reduced. It should be noted that, in other embodiments, only one end of the clamped beam of the accelerometer may be fixed to the frame structure, the other end of the clamped beam is not connected to the frame structure, and the acceleration detection circuit forms the wheatstone bridge described herein, so that cross-coupling interference is also reduced to some extent.
The wheatstone bridge composed of the strain resistor 113 and the matching resistor 114 is exemplified below. Each set of wheatstone bridges 120 comprises two branches 121 connected in parallel, two ends of each branch 121 respectively serving as two power input terminals for connecting an external power potential, for example, two ends of each branch 121 respectively connecting a first potential and a second potential different in potential. Wherein the potentials connected to different sets of wheatstone bridges 120 of the same acceleration 100 may be the same or different. It will be appreciated that the first and second potentials described herein may be two potentials that are different in any potential, such as one of zero potential and the other of a supply voltage VCC. For convenience of explanation, the first potential is uniformly set to zero potential GND and the second potential is set to power supply voltage VCC for example.
Specifically, for each set of wheatstone bridges 120: each of the branches 121 includes a strain resistor 113 and a matching resistor 114 connected in series, and a connection between the strain resistor 113 and the matching resistor 114 on each branch serves as an electrical signal output end 122 of the target axial acceleration, so that each wheatstone bridge 120 includes two electrical signal output ends 122, and the electrical signal corresponding to the target axial acceleration generated by the wheatstone bridge 120 can be a signal difference, such as a voltage difference, between the two electrical signal output ends 122. Specifically, when the accelerometer 100 is subjected to the target axial acceleration, the resistance ratio variation amounts of the two branches 121 are respectively increased and decreased; when the accelerometer 100 is subjected to non-target axial acceleration, the resistance ratio variation of the two branches 121 is increased or decreased, where the resistance ratio variation is the variation of the ratio between the resistance at the low potential end of the branch 121 and the total resistance of the branch 121, such as the variation of R11/(R11 + R21) in the branch 121 shown in fig. 2. When the strain resistor is subjected to acceleration, the resistance ratio variation of the two branches of the wheatstone bridge 120 occurs as described above, so that the electrical signals output by the two electrical signal output ends 122 of the wheatstone bridge 120 also change, and the target axial acceleration corresponding to the wheatstone bridge 120 can be measured through the electrical signals output by the two electrical signal output ends 122.
In this embodiment, the accelerometer is equipped with the strain resistor that can respond to the mass block to the effort of solidly braced beam, constitutes at least a set of wheatstone bridge through the matching resistance on strain resistor and the mass block, wherein, to every group wheatstone bridge: the device comprises two branches connected in parallel, wherein each branch comprises a strain resistor and a matching resistor which are connected in series, and the joint between the strain resistor and the matching resistor of each branch is used as an electric signal output end of the target axial acceleration; when the accelerometer is subjected to the target axial acceleration, the resistance ratio variable quantities of the two branches are respectively increased and decreased, one voltage signal output by the two electric signal output ends of the Wheatstone bridge is increased, the other voltage signal is decreased, and therefore the voltage difference between the two voltage signals is larger when the accelerometer is subjected to the target axial acceleration; when the accelerometer is subjected to non-target axial acceleration, the resistance ratio variable quantities of the two branches are increased or decreased, and at the moment, two voltage signals output by two electric signal output ends of the Wheatstone bridge are increased or decreased together, so that the voltage difference between the two voltage signals is smaller when the accelerometer is subjected to the non-target axial acceleration.
In another embodiment, the target axial acceleration of the wheatstone bridge 120 in the accelerometer 100 may be a horizontal axial acceleration or a vertical axial acceleration.
When the target axial acceleration of the wheatstone bridge 120 is a horizontal axial direction, as shown in fig. 2a or fig. 2b, both the two strain resistors 113 of the wheatstone bridge 120 are resistors at the end corresponding to the branch 121 at a low potential, and when the accelerometer 100 is subjected to the target axial acceleration of the wheatstone bridge 120, the resistance value of one strain resistor 113 of the wheatstone bridge 120 becomes large, and the resistance value of the other strain resistor 113 becomes small, so that the resistance ratio variation amounts of the two branches 121 of the wheatstone bridge 120 are respectively increased and decreased; when the accelerometer 100 is subjected to a non-target axial acceleration of the wheatstone bridge 120 (e.g., a vertical axial acceleration or another horizontal axial acceleration different from the target horizontal axial direction), the resistance values of the two strain resistors 113 of the wheatstone bridge 120 are both increased or both decreased, and thus, the resistance ratio variation of the two branches 121 of the wheatstone bridge 120 is both increased or decreased.
When the target axial acceleration of the wheatstone bridge 120 is a vertical axial direction, as shown in fig. 3, the strain resistor 113 of one branch 121 of the wheatstone bridge 120 is a resistor at a low potential end, and the matching resistor 114 of the other branch 121 is a resistor at a low potential end, when the accelerometer 100 is subjected to the target axial acceleration of the wheatstone bridge 120, the resistance values of the two strain resistors 113 of the wheatstone bridge 120 are both increased or both decreased, and thus, the resistance ratio variation amounts of the two branches 121 of the wheatstone bridge 120 are respectively increased and decreased; when the accelerometer 100 is subjected to a non-target axial acceleration of the wheatstone bridge 120, the resistance of one strain resistor 113 of the wheatstone bridge 120 becomes larger and the resistance of the other strain resistor 114 becomes smaller, so that the resistance ratio variation of the two branches 121 of the wheatstone bridge 120 is increased or decreased.
It is understood that the positions of the strain resistors on the clamped beam 111 can be correspondingly set according to the resistance change of the strain resistors 114 when subjected to different axial accelerations.
For example, as shown in fig. 4, the clamped beam 111 is arranged near two ends 111a of the mass block 112 according to a first horizontal axis, and each end 111a of the clamped beam 111 near the mass block 112 includes a first stress region a1 and a second stress region a2 arranged according to a second horizontal axis, where, when the accelerometer 100 is subjected to an acceleration of the second horizontal axis, a force applied to the first stress region a1 by the mass block 112 is opposite to a force applied to the second stress region a2, and the first horizontal axis is perpendicular to the second horizontal axis. In the present embodiment, the accelerometer 100 is a three-axis accelerometer, so it includes three wheatstone bridges 120, namely, a first wheatstone bridge, a second wheatstone bridge and a third wheatstone bridge.
Specifically, the target axial acceleration of the first wheatstone bridge 120 is a first horizontal axial direction, for example, the target axial acceleration thereof is a first axial acceleration parallel to the first horizontal axial direction, and the first axial acceleration may be defined as an X axial acceleration. The two strain resistors 113 of the first wheatstone bridge 120 are respectively located in the same stress region of the clamped beam 111 near the two ends 111a of the mass 112. For example, as shown in fig. 2a, the first wheatstone bridge 120 forms a circuit, one branch 121 of the first wheatstone bridge 120 includes a first strain resistor R11 and a first matching resistor R21, the other branch 121 includes a second strain resistor R12 and a second matching resistor R22, the first strain resistor R11 is disposed in a first stress region a1 of the fixed beam 111 near the first end 111a of the mass 112, and the second strain resistor R12 is disposed in a first stress region a1 of the fixed beam 111 near the second end 111a of the mass 112. Of course, in other embodiments, two strain resistors 113 (i.e., R11 and R12) may be respectively located in the second stress regions a2 of the clamped beam 111 near the two ends 111a of the mass 112.
The target axial acceleration of the second wheatstone bridge 120 is the second horizontal axis direction, for example, the target axial acceleration is a second axial acceleration parallel to the second horizontal axis direction, and the second axial acceleration may be defined as a Y-axis acceleration. The two strain resistors 113 of the second wheatstone bridge 120 are respectively located in different stress regions of one end 111a of the clamped beam 111 close to the mass 112. For example, as shown in fig. 2b, the second wheatstone bridge 120 forms a circuit, one branch 121 of the second wheatstone bridge 120 includes a first strain resistor R11 and a first matching resistor R21, and the other branch 121 includes a third strain resistor R13 and a third matching resistor R23; the first strain resistor R11 is disposed in a first stress region a1 of the clamped beam 111 near the first end 111a of the mass 112, and the third strain resistor R13 is disposed in a second stress region a2 of the clamped beam 111 near the first end 111a of the mass 112. In other embodiments, two strain resistors 113 (i.e., R11 and R13) may be respectively located in two stress regions of the clamped beam 111 near the second end 111a of the mass 112.
The target axial acceleration of the third wheatstone bridge 120 is the vertical axis, for example, the target axial acceleration is a third axial acceleration parallel to the vertical axis, which may be defined as a Z axial acceleration. The two strain resistors 113 of the third wheatstone bridge 12 are respectively located in different strain areas of the clamped beam 111 near the two ends 111a of the mass 112. For example, the third wheatstone bridge 120 forms a circuit as shown in fig. 3, one branch 121 of the third wheatstone bridge 120 includes a first strain resistor R11 and a first matching resistor R21, and the other branch 121 includes a fourth strain resistor R14 and a fourth matching resistor R24; the first strain resistor R11 and the fourth strain resistor R14 are resistors corresponding to the branch 121 at the end with the low potential, the first strain resistor R11 is disposed in a first stress region a1 of the clamped beam 111 near the first end 111a of the mass block 112, and the fourth strain resistor R14 is disposed in a second stress region a2 of the clamped beam 111 near the second end 111a of the mass block 112.
The first power supply input ends of the three groups of Wheatstone bridges are uniformly grounded (namely zero potential), and the second power supply input ends are uniformly connected with a power supply voltage. Specifically, for example, a junction b1 of the first strain resistor R11 and the second strain resistor R12 is grounded as a first power input terminal, a junction b2 of the first matching resistor R21 and the second matching resistor R22 is grounded as a second power input terminal, and is connected to a power supply voltage VCC, where the power supply voltage is output as V. Of course, in other embodiments, the junction b1 of the first strain resistor R11 and the second strain resistor R12 may also be connected to the power supply voltage VCC, and the junction b2 of the first matching resistor R21 and the second matching resistor R22 is grounded.
In one embodiment, the first matching resistor R21, the second matching resistor R22, the third matching resistor R23 and the fourth matching resistor R24 are all fixed to a predetermined resistance R. The resistance values of the first strain resistor R11, the second strain resistor R12 and the third strain resistor R13R14 are all preset resistance values R when no acting force is applied. Wherein R is not zero.
When the accelerometer 100 is subjected to a first axial acceleration a x Then, the resistance values of the first and third strain resistors R11 and R13 becomeIs R + Δ R x The resistance values of the second strain resistor R12 and the fourth strain resistor R14 become R- Δ R x ，ΔR x Is not zero, and the resistance value of each matching resistor is kept unchanged, so that the voltage difference V output by the first Wheatstone bridge can be obtained out1 A voltage difference V output by the second Wheatstone bridge out2 A voltage difference V output by the third Wheatstone bridge out3 The method comprises the following steps:
from the above formula, the first axial shaft acceleration a x The third wheatstone bridge output with the target axial direction as the vertical axial direction is interfered, but the numerical value of the third wheatstone bridge output is 2 times of the first wheatstone bridge output with the target axial direction as the first axial acceleration, and the third wheatstone bridge output can be regarded as 2 times of nonlinear indexes of the first wheatstone bridge output. Typically, the magnitude of this value is negligibly small. In other words, the first axial acceleration is not the first axial acceleration a to the target axial acceleration x The output interference of the other wheatstone bridges of (a) is negligible.
When the accelerometer 100 is subjected to a second axial acceleration a y Then, the resistance values of the first and second strain resistors R11 and R12 become R + Δ R y The resistance values of the third and fourth strain resistors R13 and R14 become R- Δ R y ，ΔR y All are not zero, and the resistance values of the matching resistors are kept unchanged, so that the voltage difference V output by the first Wheatstone bridge can be obtained out1 A voltage difference V output by the second Wheatstone bridge out2 A voltage difference V output by the third Wheatstone bridge out3 The method comprises the following steps:
the second axial acceleration is not the second axial acceleration a to the target axial acceleration y The output interference of the other wheatstone bridges of (a) is negligible.
When the accelerometer 100 is subjected to a third axial acceleration a z Then, the resistances of the first strain resistor R11, the second strain resistor R12, the third strain resistor R13, and the fourth strain resistor R14 all become R + Δ R z (ii) a Wherein Δ R z Are all not zero; the resistance value of each matching resistor is kept unchanged, so that the voltage difference V output by the first Wheatstone bridge can be obtained out1 A voltage difference V output by the second Wheatstone bridge out2 A voltage difference V output by the third Wheatstone bridge out3 The method comprises the following steps:
therefore, when receiving the third axial acceleration a z While, the target axial acceleration is divided into a third axial acceleration a z The output of other Wheatstone bridges except the third Wheatstone bridgeThe voltage difference of (a) is 0, so the third axial acceleration is not the third axial acceleration a to the target axial acceleration z The output interference of the other wheatstone bridges of (a) is negligible.
From the analysis of the above three axial acceleration output voltage formulas, the maximum coupling output is represented as the first axial acceleration a x And a second axial acceleration a y The disturbance to the vertical axial output, but the value of which is 2 times the sensitive axial output, is negligibly small in magnitude. Therefore, through the reasonable layout of the resistors and the reasonable design of the connecting loop, the cross coupling interference can be reduced or weakened to the maximum extent.
It is understood that in other embodiments, the accelerometer may be a single axis or two axes, and correspondingly, the axis to be measured is a horizontal axis or a vertical axis, and the above setting is performed, which is not described herein again. In addition, in the embodiment shown in fig. 4, each wheatstone bridge shares part of the strain resistors and matching resistors, thereby saving the cost of resistors and the space volume of the accelerometer. Of course, in other embodiments, the resistors of each wheatstone bridge may be independently arranged, and are not limited herein.
In another embodiment, in order to reduce the influence of the package on the performance of the accelerometer, an isolation structure is arranged at the periphery of the clamped beam and the mass block to isolate the frame structure from both the clamped beam and the mass block, so that the package stress and the interference of the package on an internal detection circuit (such as the interference of the temperature gradient stress caused by the package on the wheatstone bridge) can be isolated, and the influence of the package stress on the accelerometer can be reduced. For example, with continued reference to fig. 1a, the structural layer 110 further includes an isolation structure 117; the isolation structure 117 is disposed in the accommodating space 1161 and fixed to the frame structure 116. At least one end of the clamped beam 111 is connected to the isolation structure 117, so as to be fixed to the frame structure 116 through the isolation structure 117. In this embodiment, the isolation structure 117 and the frame structure 116 have a gap 118, and the isolation structure 117 and the mass 112 and the clamped beam 111 also have a gap 118, so as to separate the acceleration-sensitive mass from the isolation structure. The gap 118 may be a groove, or a structure relief groove.
Specifically, the isolation structure 117 includes at least one first isolation structure 117a, and at least one end of the clamped beam 111 is connected to the first isolation structure 117a to be fixed to the frame structure 116. As shown in fig. 1a, the isolation structure 117 includes two first isolation structures 117a respectively disposed at two ends 111b of the clamped beam 111 far from the mass block 112. Two ends 111b of the clamped beam 111 are respectively connected to a first isolation structure 117a to be fixed to the frame structure 116. Of course, as shown in fig. 1b, the isolation structure 117 may also include a first isolation structure 117a, where the first isolation structure 117a is disposed at one end 111b of the clamped beam 111 away from the mass block 112, so that the one end 111b of the clamped beam 111 is fixed to the frame structure 116 through the first isolation structure 117a, and the other end 111b of the clamped beam 111 may be directly connected to the frame structure 116.
The two ends of the first isolation structure 117a may extend to the frame structure 116 to connect with the frame structure 116, so that the resistors on the mass and the clamped beam may be conveniently wired. In this embodiment, an included angle between the length direction of the clamped beam and the length direction of the first isolation structure is greater than a predetermined angle, for example, the included angle is 90 degrees, that is, the first isolation structure 117a is perpendicular to the clamped beam 111. In other embodiments, the first isolation structure 117a and the clamped beam 111 may be disposed at other angles. The first isolation structure 117a can isolate the stress of the package on two opposite outer sides of the mass block 112 and the clamped beam 111 and the interference on the wheatstone bridge, thereby reducing the influence of the package on the performance of the accelerometer to a certain extent.
In another embodiment, the isolation structure 117 may further include at least one second isolation structure 117b, and the at least one first isolation structure 117a and the at least one second isolation structure 117b surround the mass block 112 and the clamped beam 111 with a gap between the mass block 112 and the clamped beam 111. As shown in fig. 5a, the isolation structure 117 includes two second isolation structures 117b in addition to the two first isolation structures 117a, and the two first isolation structures 117a and the two second isolation structures 117b form a square, such as a square, a rectangle, a diamond, and the like, so as to surround the mass block 112 and the clamped beam 111, and have a gap with the mass block 112 and the clamped beam 111. The isolation structures 117 forming the square shape also have a certain gap with the frame structure 116, and they extend to the frame structure 116 through the second isolation structure to achieve connection, thereby facilitating the wiring of the resistors on the mass block and the clamped beam. The second isolation structure 117b further isolates the package from stress and interference with the wheatstone bridge on the other two opposite outer sides of the mass block 112 and the clamped beam 111, thereby further mitigating the effect of the package on the performance of the accelerometer.
It is understood that the isolation structure 117 may also include other numbers of the first and second isolation structures 117a and 117b. As shown in fig. 5b, the isolation structure 117 includes a first isolation structure 117a and a second isolation structure 117b, and one end of the clamped beam 111 is connected to the first isolation structure 117a. One end of the first isolation structure 117a is fixed to the frame structure 116; the other end of the first isolation structure 117a is connected to the second isolation structure 117b to be fixed on the frame structure 116 through the second isolation structure 117b. As shown in fig. 5c, the isolation structure includes two first isolation structures 117a and one second isolation structure 117b, and both ends of the clamped beam 111 are respectively connected to one first isolation structure 117a. One end of each of the two first isolation structures 117a is fixed to the frame structure 116; the other ends of the two first isolation structures 117a are connected to the second isolation structure 117b to be fixed on the frame structure 116 through the second isolation structure 117b. As shown in fig. 5d, the isolation structure includes a first isolation structure 117a and two second isolation structures 117b, and one end of the clamped beam 111 is connected to the first isolation structure 117a. The two ends of the first isolation structure 117a are respectively connected to a second isolation structure 117b to be fixed on the frame structure 116 through the second isolation structure 117b. Therefore, the specific structure of the isolation structure can be set according to actual requirements, and is not limited herein.
It should be noted that the thicknesses of the isolation structure 117 and the clamped beam 111 may be set to be the same, as shown in fig. 6, where fig. 6 is a cross-sectional view along the direction y1-y2 shown in fig. 1 a. Alternatively, the thickness of the isolation structures 117 and the clamped beams 111 may be set differently, as shown in fig. 7, where fig. 7 is a cross-sectional view along the x1-x2 direction shown in fig. 1 a. The present embodiment provides a good isolation effect for the package stress and the temperature gradient stress caused by the package by providing the simple isolation structure 117, so as to reduce the influence of the package on the performance of the accelerometer and reduce the package cost. In addition, the strain resistor layout clamped beam is close to the end part of the mass block and is far away from the isolation structure and the frame structure, so that the influence of packaging stress on the detection unit can be reduced to the greatest extent, the influence of packaging on the performance of the chip is further reduced or weakened, the packaging difficulty is reduced, and the packaging cost is reduced.
In this embodiment, a plurality of external bonding pads 119 are disposed on a surface of the frame structure 116 that is the same as the clamped beam 111 on which the detection circuit 130 is disposed (i.e., the same side surface on which the strain resistor 113 is disposed), and at least one electrical signal output terminal 122 of the detection circuit 130 is correspondingly connected to the plurality of external bonding pads 119 through wires 115 disposed on the clamped beam 111 and the isolation structure 117, respectively. The specific wiring of the wires on the clamped beam and the isolation structure 117 may be set according to actual conditions, as long as the electrical connection relationship between the corresponding resistor and the external pad 119 is satisfied.
Generally, different electrical signal output terminals 122 of the detection circuit 130 and the first and second power input terminals b1 and b2 may be respectively connected to different external pads 119, and the first and second power input terminals b1 and b2 are used for providing voltage to the detection circuit 130. As an embodiment, the detection circuit 130 includes at least one set of the wheatstone bridges 120, and an electrical signal output terminal 122 and the first and second power input terminals b1 and b2 of each wheatstone bridge are respectively connected to different external pads 119. As shown in fig. 8, for a tri-axial accelerometer, the number of external pads 119 includes 8, which from left to right define pads in turn: the first electrical signal output terminal Y "of the second wheatstone bridge, the first power input terminal (which is grounded in this embodiment, i.e., GND), the second electrical signal output terminal Y" of the second wheatstone bridge, the first electrical signal output terminal X "of the first wheatstone bridge, the first electrical signal output terminal Z" of the third wheatstone bridge, the second electrical signal output terminal X "of the first wheatstone bridge, the second power input terminal VCC, and the second electrical signal output terminal Z" of the third wheatstone bridge. Of course, in this embodiment, the three wheatstone bridges share the first power input terminal and the second power input terminal. In addition, the three wheatstone bridges share the first strain resistor R11 and the first matching resistor R21, so that the three wheatstone bridges share an electrical signal output terminal, and thus share an external pad 119, such as Y +, X +, and Z +, and share an external pad 119.
In one embodiment, as shown in fig. 8, the external pads 119 include a first pad 119a (pad Y-) and a second pad 119b (pad VCC), wherein the first pad 119a can be used as the first power input terminal or the second power input terminal, and in this embodiment, the first pad 119a is connected to the power voltage VCC to be used as the second power input terminal. The electrical signal output by the second pad 119b is used to calculate an axial acceleration, specifically, a target axial acceleration corresponding to the wheatstone bridge 120, and is also used to test whether the structure of the accelerometer 100 has defects. A second power input end b2 of the detection circuit is connected to the first bonding pad 119a through a first lead 115a located at one end 111a of the clamped beam 111 close to the mass block 112; an electrical signal output end 122 of the detection circuit 130 (such as the electrical signal output end 122 between the third strain resistor R13 and the third matching resistor R23 in the second wheatstone bridge 120) is connected to the second pad 119b through a second conducting wire 115b located at the other end 111a of the clamped beam 111 close to the mass block 112, wherein the first conducting wire 115a and the second conducting wire 115b both extend from the end 111a of the clamped beam 111 close to the mass block 112 to the corresponding first isolation structure 117a in a direction away from the mass block 112, and pass through the corresponding first isolation structure 117a at least once along the length direction of the first isolation structure 117a, so that the first conducting wire and the second conducting wire can traverse the accelerometer in a larger range, and further, whether the structure has defects can be detected by detecting whether the conducting wires have problems.
Specifically, the accelerometer can perform self-test to test whether a structure of the accelerometer has a defect in the following way, and the specific detection steps are as follows: the second power input terminal b2 is supplied with power V (specifically, a dc voltage or a square wave voltage) through the first pad 119a, and when the accelerometer is normal, the output of the electrical signal output terminal 122 connected to the second pad 119b should be a level of about V/2, which will have a certain change with the change of acceleration, but does not affect the real-time detection of the accelerometer. It is possible to monitor whether the structure of the accelerometer is defective in real time by detecting whether the electrical signal output from the second pad 119b is at a level of about V/2. For example, if the difference between the electrical signal output from the second pad 119b and V/2 is within a predetermined threshold, it is determined that the structure of the accelerometer has no defect, otherwise, a defect exists.
When the power supply mode is square wave voltage, the detection mode has two types: 1) Monitoring whether the square wave period output by the second bonding pad 119b is the same as the power supply square wave period, and if so, determining that the structure of the accelerometer has no defect, namely the structure is complete; otherwise, the structure has defects; 2) Monitoring whether the amplitude of the voltage output by the second pad 119b is about V/2 (specifically, judging whether the difference between the electric signal output by the second pad 119b and V/2 is within a preset threshold), the amplitude will have a certain change along with the change of the acceleration, the change of the amplitude can be calculated according to the magnitude of the acceleration, except the change of the voltage caused by the acceleration, the amplitude of the voltage output by the second pad 119b should be about V/2, and if the value is far away from V/2 (for example, the value is V or GND), the structure has defects.
The accelerometer can realize self-checking of the structure by utilizing a self circuit, and additional structures and circuits are not required to be added, so that the cost is saved.
With continued reference to fig. 6, in yet another embodiment, the accelerometer 100 may further include a first cover 120a and a second cover 120b. The first cover 120a is disposed on a side 112a of the mass 112 away from the clamped beam 111, and the second cover 120b is disposed on a side 111b of the clamped beam 111 away from the mass 112. The first cover 120a and the second cover 120b and the frame structure 116 completely enclose the mass 112 and the clamped beam 111. It is understood that in other embodiments, the middle layer of the accelerometer may not have a frame structure, and the first cover 120a and the second cover 120b form an inner space for accommodating the middle layer. Further, in order to facilitate the connection between the external connection pad of the intermediate layer and the external circuit, a corresponding through hole 122 may be disposed at a position of the second cover 120b corresponding to the external connection pad, and an electric wire of the external circuit may pass through the through hole 122 to be connected with the external connection pad 119, or the external connection pad 119 may pass through the through hole 122 to be exposed to the outside, and then be connected with the electric wire of the external circuit.
In one embodiment, in order to limit the mass block to protect the mass block, a first blocking structure 121 is disposed on a side of the first cover 120a facing the mass block 112, and when the accelerometer 100 is not subjected to acceleration, a certain distance is provided between the first blocking structure 121 and the mass block 112; a second blocking structure 121 is disposed on a side of the second cover 120b facing the clamped beam 111, and when the accelerometer 1000 is not subjected to acceleration, a certain distance is provided between the second blocking structure 121 and the clamped beam 111. The first barrier structures and the second barrier structures 121 may be square blocks (as shown in fig. 6) or stripe-shaped structures (as shown in fig. 7, the stripe-shaped structures extend along the y1-y2 directions).
In the above embodiments, the material of the mass block, the clamped beam, the isolation structure, and the frame structure of the middle layer may be, but is not limited to, an SOI wafer, a common wafer, or a SiC wafer. The material of the barrier structure 121 may be, but is not limited to, silicon.
Referring to fig. 9, fig. 9 is a schematic flowchart illustrating a method for manufacturing an accelerometer according to an embodiment of the present application. In this embodiment, the manufacturing method includes the following steps:
s910: a base layer is provided.
The material of the base layer can be, but is not limited to, an SOI wafer, a general wafer, or a SiC wafer. In this embodiment, the base layer 910 may include a stacked multi-layer structure, wherein the multi-layer structure includes at least one silicon (Si) layer and a silicon dioxide (SiO) layer, as shown in fig. 1a0 a.
S920: and manufacturing a detection circuit on the first surface of the base layer.
Specifically, at least two strain resistors, at least two matching resistors and wires connecting the at least two strain resistors and the at least two matching resistors are manufactured on the first surface of the base layer. Wherein, the at least two matching resistors are positioned on the mass block manufactured by the following steps; the at least two strain resistors are respectively positioned at one end or two ends of the clamped beam which is manufactured in the following way and is close to the mass block.
The at least two strain resistors and the at least two matching resistors are connected through the lead to form at least one group of Wheatstone bridges, and each group of Wheatstone bridges is used for measuring a target axial acceleration. Each group of Wheatstone bridges is used for generating an electric signal corresponding to a target axial acceleration; the Wheatstone bridge generates the electrical signal when the accelerometer is subject to the target axial acceleration greater than the electrical signal generated when the accelerometer is subject to a non-target axial acceleration.
For example, for each set of wheatstone bridges: the device comprises two branches connected in parallel, wherein each branch comprises a strain resistor and a matching resistor which are connected in series, and the joint between the strain resistor and the matching resistor is used as an electric signal output end of the target axial acceleration; when the accelerometer is subjected to the target axial acceleration, the resistance ratio variable quantities of the two branches are respectively increased and decreased; when the accelerometer is subjected to non-target axial acceleration, the resistance ratio variation of the two branches is increased or decreased, wherein the resistance ratio variation is the variation of the ratio between the resistance at the low-potential end in the branch and the total resistance of the branch.
Specifically, S920 may include the following sub-steps:
s921: and manufacturing at least two strain resistors and at least two matching resistors on the first surface of the base layer.
For example, heavily doped B ions may be used to fabricate a strain resistor pad 931 corresponding to at least two strain resistors and a matching resistor pad 931 corresponding to at least two matching resistors on the first surface 910a of the base layer 910, as shown in fig. 1a0 a; then, the at least two strain resistors 932 are correspondingly fabricated on the strain resistor pad 931 and the at least two matching resistors 932 are correspondingly fabricated on the matching resistor pad 931 by using the shallow doped B ions, as shown in fig. 1a 0B. In the embodiment, the resistor is manufactured by firstly heavily doping and then lightly doping, so that the process of manufacturing the resistor is simplified, and the cost is reduced.
S922: and manufacturing an external bonding pad and a lead for connecting the at least two strain resistors, the at least two matching resistors and the external bonding pad on the first surface of the base layer.
For example, the conductive traces 934 and external pads 933 are formed on the first surface 910a of the base layer 910 by sputtering (or evaporation) and etching, as shown in fig. 1 a-0 c. The wires 934 and the external pads 933 may be made of silicon aluminum. In addition, the external connection pad may be thickened with aluminum (for example, by electroplating, evaporation, sputtering, and the like) to meet the requirement of wire bonding (for example, the thickness of the external connection pad 933 may pass through the through hole of the second cover and then be exposed to the outside).
S930: and etching a second surface of the base layer, which is opposite to the first surface, to form a mass block and a frame structure.
Specifically, a back Reactive Ion Etching (DRIE) or a tetramethylammonium hydroxide (TMAH) wet Etching method may be used to etch the second surface 910b of the base layer 910 opposite to the first surface to form the mass 912 and the frame structure 916 surrounding the mass, as shown in fig. 1a0 d. Wherein, the frame structure 916 has a gap with the mass block 912. In the above-described embodiment, the at least two matching resistors are correspondingly located on the first surface 910a of the proof mass 912; the external bonding pads are correspondingly located on the first surface 910a of the frame structure 912.
In one embodiment, the accelerometer includes a first cover and a second cover. After the mass block is manufactured, before performing the following S940, the manufacturing method may further include:
manufacturing the first cover 920a with the blocking structure 921 on the inner side and manufacturing the first cover 920b with the blocking structure 921 on the inner side, as shown in fig. 1a0 e. The first cover 920a and the second cover 920b may be fabricated by wet etching. It is understood that in other embodiments, the cover may be manufactured without the blocking structure 921.
After the cover is formed, the first cover 920a is bonded to the base layer 910 near the second surface 910b, as shown in fig. 1a0 f.
S940: and etching the first surface of the base layer to form a clamped beam, wherein the clamped beam is arranged in an accommodating space formed by the frame structure, and two ends of the clamped beam are respectively fixed on the frame structure.
Specifically, the first surface 910a of the base layer 910 may be etched by dry etching to obtain the clamped beam, as shown in fig. 1a and 0g, and the structure is released, that is, a certain gap exists between the clamped beam and the mass block 912. It will be appreciated that fig. 1a0g does not show clamped beams due to the angle of the section of the accelerometer, and the specific structure and location of the clamped beams can be seen in fig. 1 a-8. It is understood that, in other embodiments, the clamped beam formed in this step may also be of a single-end fixing and frame structure, and is not limited herein.
In an embodiment, the accelerometer is provided with an isolation structure, so the step S930 may specifically include: etching the first surface 910a of the base layer 910 to form a clamped beam 911 and at least one isolation structure 917; wherein the at least one isolation structure 917 is fixed to the rim structure 916, and at least one end of the clamped beam 911 is fixed to the rim structure 916 through the at least one isolation structure 917. The at least one isolation structure 917 may include two first isolation structures respectively disposed at two ends of the clamped beam far away from the mass block. The two ends of the clamped beam are respectively connected with a first isolation structure so as to be fixed on the frame structure through the first isolation structure.
In one embodiment, the accelerometer includes a first cover and a second cover. After performing S940, the manufacturing method may further include:
and bonding the manufactured second cover body 920b with the base layer 910 near the first surface 910a, as shown in fig. 10 h. According to the embodiment, the first cover body is bonded firstly, the clamped beam is manufactured, then the second cover body is bonded, the risk that the yield is reduced due to the fact that the structure on one side of the second surface of the base layer is converted back and forth in different processes is reduced, and the yield is improved and ensured to be improved and stable. Of course, in other embodiments, the first cover and the second cover may be bonded after performing the completion S940.
Further, as shown in fig. 10i, the outer sides of the first cover 920a and the second cover 920b may be thinned, and the position of the second cover 920b corresponding to the external pad 933 is hollowed to form a through hole 922, so as to release the external pad, so that the wire of the external circuit may pass through the through hole and be connected with the external pad, or the external pad passes through the through hole and is exposed to the outside, and is connected with the wire of the external circuit.
It is understood that fig. 10a to 10i are only schematic illustrations of the acceleration structure manufactured in each process, and the actual structure thereof may differ from that of fig. 10a to 10i, but does not affect the understanding of the manufacturing steps of the manufacturing method and the manufactured accelerometer structure.
The above manufacturing method can be used for manufacturing the accelerometer in the above accelerometer embodiment, so the specific structure of the accelerometer manufactured by the manufacturing method can refer to the above accelerometer embodiment.
In the scheme, the accelerometer reduces the degree of freedom of motion of the mass block by arranging the fixed supporting beams with two ends fixed on the frame structure, so that when the accelerometer is subjected to acceleration in a certain axial direction, the accelerometer can weaken the interference introduced in other axial directions, and therefore the cross coupling interference is reduced. In addition, the accelerometer forms at least one group of Wheatstone bridges through the mode, the problem of cross coupling interference can be greatly weakened or even eliminated, the decoupling mode is simple, the synchronous detection of single-axis or multi-axis acceleration can be realized, and the size of a chip is favorably reduced. Moreover, cross coupling interference is greatly weakened, so that an interface circuit externally connected with an accelerometer and used for calculating the acceleration by utilizing an electric signal sensitive to a Wheatstone bridge can be realized simply and conveniently, and functional circuits such as various filtering circuits and the like are not required to be added for eliminating the interference. In addition, the accelerometer can improve linearity, sensitivity and temperature characteristic performance by arranging an isolation structure, and is simple in structure and simple and convenient in implementation process.
In the description above, for purposes of explanation rather than limitation, specific details are set forth such as the particular system architecture, interfaces, techniques, etc., in order to provide a thorough understanding of the present application. It will be apparent, however, to one skilled in the art that the present application may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known devices, circuits, and methods are omitted so as not to obscure the description of the present application with unnecessary detail.
Claims (12)
1. An accelerometer, comprising a structural layer, the structural layer comprising:
the frame structure is provided with an accommodating space;
the fixed supporting beam is arranged in the accommodating space;
the mass block is arranged on the clamped beam, and when the accelerometer is subjected to acceleration, the mass block generates acting force on the clamped beam due to the acceleration;
the detection circuit is used for outputting an electric signal corresponding to at least one axial acceleration based on the acting force generated by the mass block; wherein the detection circuit comprises:
the strain resistors are respectively arranged at two ends of the clamped beam close to the mass block and can cause resistance value change due to the acting force generated by the mass block;
the at least three matching resistors are arranged on the mass block;
the at least three strain resistors and the at least three matching resistors form at least two groups of Wheatstone bridges, the at least two groups of Wheatstone bridges share the at least three strain resistors and the at least three matching resistors, and each group of Wheatstone bridges is used for generating an electric signal corresponding to a target axial acceleration; the wheatstone bridge generates the electrical signal when the accelerometer is subject to the target axial acceleration that is greater than the electrical signal generated when the accelerometer is subject to a non-target axial acceleration.
2. The accelerometer of claim 1,
for each set of said wheatstone bridges: including two branch roads of parallel connection, every the branch road includes a strain resistance and a matching resistance of series connection, just strain resistance with junction between the matching resistance is regarded as the signal of telecommunication output of target axial acceleration.
3. The accelerometer of claim 2,
the two ends, close to the mass block, of the clamped beam are arranged in a first horizontal axial direction, each end, close to the mass block, of the clamped beam comprises a first stress area and a second stress area, the first stress area and the second stress area are arranged in a second horizontal axial direction, when the accelerometer is subjected to acceleration in the second horizontal axial direction, the direction of acting force of the mass block on the first stress area is opposite to that of acting force of the mass block on the second stress area, and the first horizontal axial direction is perpendicular to the second horizontal axial direction.
4. The accelerometer of claim 3, wherein said at least two sets of Wheatstone bridges comprise a first Wheatstone bridge having a target axial acceleration that is a first axial acceleration parallel to said first horizontal axis and a second Wheatstone bridge having a target axial acceleration that is a second axial acceleration parallel to said second horizontal axis;
one branch of the first Wheatstone bridge comprises a first strain resistor and a first matching resistor, and the other branch of the first Wheatstone bridge comprises a second strain resistor and a second matching resistor; the first strain resistor is arranged in a first stress area of the clamped beam close to the first end of the mass block, and the second strain resistor is arranged in a first stress area of the clamped beam close to the second end of the mass block;
one branch of the second Wheatstone bridge comprises the first strain resistor and the first matching resistor, and the other branch comprises a third strain resistor and a third matching resistor; and the third strain resistor is arranged in a second stress area of the clamped beam close to the first end of the mass block.
5. The accelerometer of claim 4, wherein the at least two sets of Wheatstone bridges further comprise a third Wheatstone bridge having a target axial acceleration that is a third axial acceleration parallel to a vertical axis that is perpendicular to the first and second horizontal axes;
one branch of the third Wheatstone bridge comprises the first strain resistor and the first matching resistor, and the other branch comprises a fourth strain resistor and a fourth matching resistor; the first strain resistor and the fourth matching resistor are resistors corresponding to the ends, at low potential, of the branches, and the fourth strain resistor is arranged in a second stress area, close to the second end of the mass block, of the clamped beam.
6. The accelerometer of claim 1, wherein the structural layer further comprises an isolation structure disposed in the receiving space, the isolation structure is fixed to the frame structure, and at least one end of the clamped beam is fixed to the frame structure through the isolation structure.
7. The accelerometer according to claim 6, wherein a plurality of external bonding pads are disposed on a surface of the frame structure, which is the same as a surface of the clamped beam on which the detection circuit is disposed, and an electrical signal output end of the detection circuit is correspondingly connected to the external bonding pads through wires disposed on the clamped beam and the isolation structure, respectively.
8. The accelerometer of claim 7, wherein said plurality of external pads comprises a first pad and a second pad;
a first power supply input end or a second power supply input end of the detection circuit is connected to the first bonding pad through a first lead positioned at one end of the clamped beam close to the mass block; the output end of the detection circuit is connected to the second bonding pad through a second lead located at the other end, close to the mass block, of the clamped beam, wherein the first lead and the second lead both extend to the corresponding isolation structure from the end, close to the mass block, of the clamped beam to the direction far away from the mass block, and pass through the corresponding isolation structure at least once along the length direction of the isolation structure.
9. The accelerometer of claim 1, further comprising a first cover and a second cover;
the first cover body is arranged on one side, far away from the fixed supporting beam, of the mass block, and the second cover body is arranged on one side, far away from the mass block, of the fixed supporting beam.
10. The accelerometer of claim 9, wherein a side of the first cover facing the mass is provided with a first blocking structure, and wherein the first blocking structure is spaced from the mass when the accelerometer is not subjected to acceleration;
and a second blocking structure is arranged on one side, facing the clamped beam, of the second cover body, and a certain distance is reserved between the second blocking structure and the clamped beam when the accelerometer is not accelerated.
11. A method of manufacturing an accelerometer according to any of claims 1 to 10, comprising:
providing a base layer;
manufacturing at least three strain resistors, at least three matching resistors and wires for connecting the at least three strain resistors and the at least three matching resistors on the first surface of the base layer to manufacture a detection circuit; wherein the at least three matching resistors are located on the proof mass; the at least three strain resistors are respectively positioned at two ends of the clamped beam close to the mass block; the at least three strain resistors and the at least three matching resistors are connected through the lead wires to form at least two groups of Wheatstone bridges, the at least two groups of Wheatstone bridges share the at least three strain resistors and the at least three matching resistors, and each group of Wheatstone bridges is used for generating an electric signal corresponding to a target axial acceleration; the Wheatstone bridge generates a greater electrical signal when the accelerometer is subject to the target axial acceleration than when the accelerometer is subject to a non-target axial acceleration;
etching a second surface of the base layer, which is opposite to the first surface, to form a mass block and a frame structure, wherein a gap is formed between the frame structure and the mass block;
and etching the first surface of the base layer to form a clamped beam, wherein the clamped beam is arranged in an accommodating space formed by the frame structure, and two ends of the clamped beam are respectively fixed on the frame structure.
12. The method of claim 11, wherein the fabricating at least three strain resistors, at least three matching resistors, and wires connecting the at least three strain resistors and the at least three matching resistors on the first surface of the base layer comprises:
manufacturing strain resistance pads corresponding to at least three strain resistors and matching resistance pads corresponding to at least three matching resistors on the first surface of the base layer by adopting heavily-doped B ions;
correspondingly manufacturing the at least three strain resistors on the strain resistor bonding pad and the at least three matching resistors on the matching resistor bonding pad by adopting shallow doped B ions;
the first surface of basic layer makes external pad and connects at least three strain resistance, at least three matching resistance and the wire of external pad, wherein external pad is established frame structure first surface is last.
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