CN109596859B - Piezoresistive acceleration sensor - Google Patents
Piezoresistive acceleration sensor Download PDFInfo
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- CN109596859B CN109596859B CN201910047934.3A CN201910047934A CN109596859B CN 109596859 B CN109596859 B CN 109596859B CN 201910047934 A CN201910047934 A CN 201910047934A CN 109596859 B CN109596859 B CN 109596859B
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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
Abstract
The invention provides a piezoresistive acceleration sensor, which belongs to the field of acceleration sensors and comprises: a frame, inside which a movable cavity is arranged; the mass block is movably arranged in the movable cavity; the two ends of the long shaft are respectively connected with the frame and the mass block through measuring sections provided with pressure-sensitive elements; and two ends of the long shaft are respectively connected with the sensitive beam and the frame, and the rigidity of the first support beam in the mass block sensing direction is smaller than that of the first support beam in the direction perpendicular to the mass block sensing direction. The first supporting beam is used for reinforcing the sensitive beam, and the degree of the first supporting beam in the sensing direction of the mass block is smaller, so that the piezoresistive acceleration sensor keeps higher sensitivity; the rigidity of the first supporting beam in the direction perpendicular to the sensing direction of the mass block is high, so that the deformation of the sensing beam and the measuring section is reduced when the sensor is accelerated in the direction other than the sensing direction, and the breakage of the sensing beam and the measuring section is avoided.
Description
Technical Field
The invention belongs to the technical field of acceleration sensors, and particularly relates to a piezoresistive acceleration sensor.
Background
Micro-Electro-Mechanical systems (MEMS), also called Micro-Electro-Mechanical systems, microsystems, micromachines, etc., refer to high-tech devices with dimensions of a few millimeters or even smaller. MEMS acceleration sensors are sensors made using micromachining techniques. The MEMS acceleration sensor can be classified into a capacitive type, a piezoresistive type, a thermal current type, a piezoelectric type, a resonant type, and the like according to different working principles. Compared with other forms of MEMS acceleration sensors, the MEMS piezoresistive acceleration sensor has the characteristics of simple processing technology, convenient testing, low cost and the like, so that the MEMS piezoresistive acceleration sensor is widely applied.
A typical MEMS piezoresistive acceleration sensor is based on the piezoresistive effect of a semiconductor, and is composed of a mass block and a cantilever beam. The manufacture of the piezoresistor is a key technology for realizing the MEMS piezoresistive acceleration sensor, and the current processing technology mainly manufactures the piezoresistor on the upper surface of the cantilever beam. When the structure is subjected to the action of acceleration vertical to the direction of the silicon chip, the mass block generates displacement in the vertical direction, the cantilever beam bends upwards or downwards according to the direction of the acceleration, and pressure stress or tensile stress is generated on the upper surface of the cantilever beam, so that the resistance value of the piezoresistor on the upper surface is reduced or increased, and the acceleration can be obtained by measuring the change of the resistance value. Therefore, the MEMS piezoresistive acceleration sensor with piezoresistors fabricated on the upper surface of the cantilever beam is mainly used for measuring acceleration in the vertical direction. However, because the sensitive direction of the acceleration sensor is determined, and the measured acceleration direction has randomness, the acceleration in the direction other than the sensitive direction easily causes the cantilever beam to break, so that the sensor is damaged.
Disclosure of Invention
The invention aims to provide a piezoresistive acceleration sensor to solve the technical problems that acceleration in directions other than the sensitive direction of the acceleration sensor easily causes overload of the acceleration sensor, and breakage of a cantilever beam easily causes damage of the acceleration sensor in the prior art.
In order to achieve the purpose, the invention adopts the technical scheme that: provided is a piezoresistive acceleration sensor comprising:
a frame, inside which a movable cavity is arranged;
the mass block is movably arranged in the movable cavity;
the two ends of the long shaft are respectively connected with the frame and the mass block through measuring sections provided with pressure-sensitive elements; and
and two ends of the long shaft are respectively connected with the middle part of the sensitive beam and the frame, and the rigidity of the first support beam in the sensing direction of the mass block is smaller than that of the first support beam in the direction vertical to the sensing direction of the mass block.
Further, the thickness of the first support beams in the proof-mass sensing direction is smaller than the thickness of the sense beams in the proof-mass sensing direction.
Further, the measuring section comprises a sensitive thin beam; two ends of a long shaft of the sensitive thin beam are respectively connected with the end part of the sensitive beam and the mass block; the width direction of the sensitive thin beam is perpendicular to the sensing direction of the mass block, the width direction of the sensitive beam is perpendicular to the sensing direction of the mass block, and the width of the sensitive thin beam is smaller than that of the sensitive beam; one side of the sensitive thin beam in the width direction is provided with a minimum distance limiting block, and the minimum distance limiting block is positioned between the end face of the sensitive beam and the side face of the mass block opposite to the end face of the sensitive beam.
Further, the thickness direction of the sensitive thin beam is parallel to the sensing direction of the mass block, the thickness direction of the sensitive beam is parallel to the sensing direction of the mass block, and the thickness of the sensitive thin beam is smaller than that of the sensitive beam; the pressure-sensitive element is arranged on one side of the sensitive thin beam in the thickness direction.
Furthermore, the sensitive beam is located in the movable cavity and parallel to the side edge of the mass block close to the sensitive beam, the first support beam is located in the movable cavity and located on one side of the sensitive beam far away from the mass block, and the first support beam and the sensitive beam are arranged in parallel.
Further, the piezoresistive acceleration sensor further includes:
and two ends of the long shaft are respectively connected with the mass block and the frame, and the thickness of the second supporting beam in the mass block sensing direction is smaller than that of the sensitive beam in the mass block sensing direction.
Further, the second support beam includes:
the main body section is positioned in the movable cavity and is parallel to the side edge of the mass block close to the main body section;
the first bending section is arranged at an included angle with the main body section, one end of the first bending section is connected with one end of the main body section, and the other end of the first bending section is connected with the mass block; and
and the second bending section is arranged at an included angle with the main body section, one end of the second bending section is connected with the other end of the main body section, and the other end of the second bending section is connected with the mass block.
Furthermore, the mass block is provided with a plurality of first through holes, the first through holes penetrate through the mass block along the sensing direction of the mass block, and the first through holes are rectangular holes.
Further, the movable cavity forms open ports on two sides of the frame in the sensing direction of the mass block respectively;
the piezoresistive acceleration sensor further comprises:
a substrate connected to the frame to close one of the openings; and
the cover plate is connected with the frame and used for closing the other opening;
the quality piece towards the surface of substrate is equipped with the spacing groove, the spacing groove is close to the inner wall of apron one side is equipped with the second perforating hole, the second perforating hole is followed quality piece sensing direction runs through the quality piece, the substrate be equipped with be used for with the spacing groove is close to the inner wall butt and the restriction of apron one side the quality piece with the spacing arch of the minimum interval of substrate.
The piezoresistive acceleration sensor provided by the invention has the beneficial effects that: compared with the prior art, the piezoresistive acceleration sensor provided by the invention has the advantages that the mass block moves in the movable cavity of the frame to drive the sensitive beam and the measuring section to bend, the pressure stress or the tensile stress of the measuring section is detected through the pressure-sensitive element, and the acceleration is obtained through calculation. The first supporting beam is used for reinforcing the sensitive beam, the rigidity of the first supporting beam is smaller in the sensing direction of the mass block, and the sensitive beam can be bent to a larger degree in the sensing direction, so that the piezoresistive acceleration sensor keeps higher sensitivity; in the direction perpendicular to the sensing direction of the mass block, the rigidity of the first supporting beam is high, the rigidity of the sensitive beam in the plane perpendicular to the sensing direction of the mass block can be increased, and when the piezoresistive acceleration sensor faces acceleration in a direction other than the sensing direction, the bending of the sensitive beam and the measuring section in the plane perpendicular to the sensing direction of the mass block is reduced, so that the sensitive beam and the measuring section are prevented from being broken.
The present invention also provides a mobile device comprising: any one of the piezoresistive acceleration sensors described above.
The mobile equipment provided by the invention has the beneficial effects that: compared with the prior art, the mobile equipment provided by the invention has the advantages that the piezoresistive acceleration sensor is adopted, and the piezoresistive acceleration sensor can be prevented from being damaged when the acceleration direction of the mobile equipment is different from the sensitive direction of the piezoresistive acceleration sensor in the mobile equipment.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.
Fig. 1 is a perspective view of a piezoresistive acceleration sensor according to an embodiment of the present invention;
fig. 2 is a perspective view of the piezoresistive acceleration sensor in fig. 1, on the other side opposite to the direction of fig. 1;
FIG. 3 is a top view of the piezoresistive acceleration sensor of FIG. 1;
FIG. 4 is a bottom view of the piezoresistive acceleration sensor of FIG. 1;
FIG. 5 is an enlarged view taken at A in FIG. 3;
FIG. 6 is a cross-sectional view taken at C-C of FIG. 3;
FIG. 7 is a cross-sectional view taken along line B-B of FIG. 3;
FIG. 8 is a cross-sectional view taken along line D-D of FIG. 3;
fig. 9 is a sectional view of a piezoresistive acceleration sensor according to another embodiment of the present invention.
Wherein, in the figures, the respective reference numerals:
1-a frame; 2-a mass block; 21-a first through hole; 22-a limiting groove; 23-a second through hole; 3-a sensitive beam; 4-measuring section; 41-sensitive thin beam; 42-a minimum distance stopper; 43-a pressure sensitive element; 5-a first support beam; 6-a second support beam; 61-a body section; 62-a first bend section; 63-a second bend section; 7-a substrate; 71-a limiting bulge; 8-cover plate; 9-support layer.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 1 to 8, a piezoresistive acceleration sensor according to an embodiment of the present invention will be described. Piezoresistive acceleration sensor, comprising:
the frame 1 is internally provided with a movable cavity;
the mass block 2 is movably arranged in the movable cavity;
two ends of a long shaft of the sensitive beam 3 are respectively connected with the frame 1 and the mass block 2 through a measuring section 4 provided with a pressure-sensitive element 43; and
and two ends of the long shaft of the first support beam 5 are respectively connected with the middle part of the sensitive beam 3 and the frame 1, and the rigidity of the first support beam 5 in the sensing direction of the mass block 2 is smaller than that in the direction vertical to the sensing direction of the mass block 2.
Compared with the prior art, the piezoresistive acceleration sensor drives the sensitive beam 3 and the measuring section 4 to bend through the movement of the mass block 2 in the movable cavity of the frame 1, detects the compressive stress or the tensile stress of the measuring section 4 through the pressure-sensitive element 43, and obtains the acceleration through calculation. The sensitive beam 3 is reinforced by the first supporting beam 5, the first supporting beam 5 has smaller rigidity in the sensing direction of the mass block 2, and the sensitive beam 3 can be bent to a larger degree in the sensing direction, so that the piezoresistive acceleration sensor keeps higher sensitivity; in the direction perpendicular to the sensing direction of the mass block 2, the rigidity of the first supporting beam 5 is high, the rigidity of the sensitive beam 3 in the plane perpendicular to the sensing direction of the mass block 2 can be increased, and when the piezoresistive acceleration sensor faces the acceleration in the direction other than the sensing direction, the bending of the sensitive beam 3 and the measuring section 4 in the plane perpendicular to the sensing direction of the mass block 2 is reduced, so that the sensitive beam 3 and the measuring section 4 are prevented from being broken.
Specifically, the frame 1, the mass block 2, the sensitive beam 3, the measuring section 4, the first support beam 5 and other components are made of silicon materials through an MEMS technology. The frame 1 is rectangular and annular, and a movable cavity is formed inside the frame. In fig. 6, the mass 2 is located in the movable cavity and can move in the up-and-down direction for sensing the acceleration in the up-and-down direction, which is the sensing direction of the mass 2, that is, the sensitive direction of the piezoresistive acceleration sensor. The number of the sensitive beams 3 can be two, and the two sensitive beams 3 are positioned in the movable cavity and are respectively positioned at the two longitudinal sides of the mass block 2. The thickness of the sensitive beam 3 is far smaller than that of the mass block 2, and the width of the sensitive beam 3 is far smaller than that of the mass block 2. Two ends of a long shaft of the sensitive beam 3 are respectively connected with the mass block 2 and the frame 1 through the measuring section 4, so that the mass block 2 can move in corresponding directions after being subjected to upward or downward acceleration, and the sensitive beam 3 and the measuring section 4 are driven to bend. In fig. 7, the piezoresistors 43 can be piezoresistors manufactured on the upper surface of the sensitive thin beam 41 by a surface diffusion process, and four piezoresistors can form a wheatstone measuring bridge, and the corresponding acceleration can be obtained by detecting the bending degree of the measuring section 4 upwards or downwards and calculating the bending degree. The two first supporting beams 5 are respectively connected with the two sensitive beams 3, so that the rigidity of the sensitive beams 3 in a plane perpendicular to the sensing direction of the mass block 2 is increased, and the first supporting beams 5 can be made of other materials with different rigidities in different directions.
Referring to fig. 1 to 3 and fig. 6 and 7, as an embodiment of the piezoresistive acceleration sensor provided by the present invention, the thickness of the first support beam 5 in the sensing direction of the proof mass 2 is smaller than the thickness of the sensing beam 3 in the sensing direction of the proof mass 2. The rigidity of the first supporting beams 5 in the sensing direction of the mass block 2 is lower than that in the direction perpendicular to the sensing direction of the mass block 2, so that the production and the processing are convenient.
Specifically, the first support beam 5 is located in the movable cavity and has a long strip shape, and may be made of silicon material by using an MEMS technique. The thickness direction of the first support beams 5 is parallel to the sensing direction of the mass block 2, the width direction of the first support beams 5 is perpendicular to the sensing direction of the mass block 2, as shown in fig. 6 and 7, the thickness of the first support beams 5 in the up-down direction is smaller than that of the sensitive beams 3 in the up-down direction, and the influence on the rigidity of the sensitive beams 3 in the up-down direction is reduced.
Referring to fig. 5 and 7, as an embodiment of the piezoresistive acceleration sensor provided by the present invention, the measuring section 4 includes a sensing thin beam 41; two ends of a long shaft of the sensitive thin beam 41 are respectively connected with the end part of the sensitive beam 3 and the mass block 2; the width direction of the sensitive thin beam 41 is vertical to the sensing direction of the mass block 2, the width direction of the sensitive beam 3 is vertical to the sensing direction of the mass block 2, and the width of the sensitive thin beam 41 is smaller than that of the sensitive beam 3; one side of the sensitive thin beam 41 in the width direction is provided with a minimum distance limiting block 42, and the minimum distance limiting block 42 is positioned between the end face of the sensitive beam 3 and the mass block 2.
Specifically, the width of the sensitive thin beam 41 is smaller than that of the sensitive beam 3, so that the stress at the sensitive thin beam 41 is more concentrated, and the sensitive thin beam 41 can generate larger deformation. The minimum distance limiting block 42 is located between the end face of the sensing beam 3 and the side face of the mass block 2 opposite to the end face of the sensing beam 3, when the mass block 2 is subjected to a large transverse or longitudinal acceleration, the end face of the sensing thin beam 41 and the side face of the mass block 2 clamp the minimum distance limiting block 42, so that the minimum distance between the end face of the sensing thin beam 41 and the side face of the mass block 2 is limited, the relative rotation of the mass block 2 and the sensing beam 3 in a plane perpendicular to the sensing direction of the mass block 2 is limited, the displacement of the mass block 2 in the transverse or longitudinal direction is further limited, and the transverse sensitivity of the sensor is further limited. More specifically, the mass 2 includes a rectangular main body portion and a connecting portion protruding from a lateral side of the main body portion, and one end of the sensitive beam 41 is connected to a longitudinal side of the connecting portion. The two sides of the sensitive thin beam 41 in the width direction are both provided with a minimum distance limiting block 42, and the minimum distance limiting block 42 is positioned between the end face of the sensitive thin beam 41 and the longitudinal side face of the connecting part of the mass block 2. From top to bottom, the two minimum distance limiting blocks 42 and the sensitive thin beam 41 are connected in a cross shape, as shown in fig. 5.
More specifically, a support layer 9 is connected between the end face of the sensor beam 3 and the side face of the mass 2 opposite to the end face of the sensor beam 3. The supporting layer 9 is connected to the sensing beam 41 and is located on one side of the sensing beam 41 in the sensing direction of the proof mass 2, and more specifically, the supporting beam 9 and the pressure-sensitive element 43 are respectively located on two opposite sides of the sensing beam 41. The width of the supporting layer 9 in the direction perpendicular to the sensing direction of the proof mass 2 is larger than the width of the sensitive thin beam 41 in the direction perpendicular to the sensing direction of the proof mass 2. The thickness of the support layer 9 in the sensing direction of the proof mass 2 is smaller than the thickness of the sensitive thin beam 41 in the sensing direction of the proof mass 2.
Referring to fig. 2, fig. 5 and fig. 7, as an embodiment of the piezoresistive acceleration sensor provided by the present invention, a thickness direction of the sensing thin beam 41 is parallel to a sensing direction of the proof mass 2, a thickness direction of the sensing beam 3 is parallel to the sensing direction of the proof mass 2, and a thickness of the sensing thin beam 41 is smaller than a thickness of the sensing beam 3; the pressure-sensitive element 43 is provided on one side in the thickness direction of the sensitive thin beam 41. The thickness of the sensitive thin beam 41 is reduced, so that the stress at the sensitive thin beam 41 is more concentrated, the sensitive thin beam 41 can generate larger bending deformation in the vertical direction, and the sensitive thin beam 41 is prevented from being broken.
Specifically, the surface on one side in the thickness direction of the sensitive thin beam 41 is flush with the surface on the same side in the thickness direction of the sensitive beam 3, and the pressure-sensitive element 43 is provided on the surface of the sensitive thin beam 41.
Referring to fig. 1 to 4, as an embodiment of the piezoresistive acceleration sensor provided by the present invention, the sensing beam 3 is located in the movable cavity and parallel to the side of the mass block 2 close to the sensing beam 3, the first supporting beam 5 is located in the movable cavity and on the side of the sensing beam 3 far from the mass block 2, and the first supporting beam 5 and the sensing beam 3 are parallel. The mass block 2 is parallel to the side edge of the mass block 2 connected with the sensitive beam 3, so that the sensitive beam 3 can be arranged longer under the condition that the retaining frame 1 and the movable cavity are smaller, and the sensitivity is improved. The first supporting beams 5 are arranged in parallel with the sensitive beams 3, and the first supporting beams 5 can be arranged longer, so that the rigidity of the first supporting beams 5 in the moving direction of the mass block 2 is reduced. In fig. 7, the pressure sensitive element 43 is a pressure sensitive resistor made by a surface diffusion process on the upper surface of the sensitive thin beam 41.
Specifically, the mass block 2 comprises a rectangular main body part and a connecting part protruding out of the transverse side surface of the main body part, and one end of the sensitive beam 3 is connected with the longitudinal side surface of the connecting part through the measuring section 4, so that the sensitive beam 3 can be parallel to the side edge of the mass block 2 connected with the sensitive beam 3. The first supporting beam 5 is positioned between the sensitive beam 3 and the inner wall of the frame 1, one end of the first supporting beam 5 is connected to the middle of the long shaft of the first supporting beam 5 through a bending section, and the other end of the first supporting beam 5 is connected to the inner wall of the frame 1 through a bending section. The first supporting beam 5 and the bending sections at the two ends of the long shaft thereof are of a Z-shaped bending structure.
Referring to fig. 1 to fig. 4 and fig. 8, as an embodiment of the piezoresistive acceleration sensor provided by the present invention, the piezoresistive acceleration sensor further includes:
and two ends of the long axis of the second supporting beam 6 are respectively connected with the mass block 2 and the frame 1, and the thickness of the second supporting beam 6 in the sensing direction of the mass block 2 is smaller than that of the sensitive beam 3 in the sensing direction of the mass block 2. The second support beam 6 and the sensing beam 3 together position the mass 2 in the active cavity. The thickness of the second support beam 6 is smaller than that of the sensing beam 3, so that the mass block 2 can generate large bending deformation of the sensing beam 3.
In particular, the second support beam 6 is also made of silicon material by MEMS technology. Two second supporting beams 6 are positioned in the movable cavity and are respectively arranged at two transverse sides of the mass block 2. The thicknesses of the sensitive thin beam 41, the first support beam 5, and the second support beam 6 may be the same.
Referring to fig. 5, as an embodiment of the piezoresistive acceleration sensor provided by the present invention, the second supporting beam 6 includes:
a main body section 61 which is positioned in the movable cavity and is parallel to the side edge of the mass block 2 close to the main body section 61;
the first bending section 62 is arranged at an included angle with the main body section 61, one end of the first bending section is connected with one end of the main body section 61, and the other end of the first bending section is connected with the mass block 2; and
the second bending section 63 is disposed at an included angle with the main body section 61, one end of the second bending section is connected to the other end of the main body section 61, and the other end of the second bending section is connected to the mass block 2.
Specifically, the second support beam 6 is of a bent structure, and the main body section 61 and the first bent section 62 and the second bent section 63 at two ends of the long axis thereof are Z-shaped. The body section 61 is parallel to the longitudinal sides of the mass 2, so that with a small holding frame 1 and active chamber, the body section 61 can be arranged longer, increasing the sensitivity.
Referring to fig. 1 to 3 and fig. 5 and 6, as an embodiment of the piezoresistive acceleration sensor provided by the present invention, the mass block 2 is provided with a plurality of first through holes 21, the first through holes 21 penetrate through the mass block 2 along a sensing direction of the mass block 2, and the first through holes 21 are rectangular holes.
When the mass block 2 moves up and down, air above or below the mass block is extruded to cause transverse flow of air, so that air damping is generated, the dynamic performance of a vibration system is obviously influenced, and the piezoresistive acceleration sensor is in states of damping oscillation, free oscillation and the like. When the gas damping is large, large noise is generated, and the quality factor of the sensor is reduced. Especially for micromechanical structures, gas damping has an important influence on the motion of the micromechanical structure, since gas damping has a rate-reducing effect, i.e. the structure resonance frequency and the gas damping ratio, etc. will increase proportionally with decreasing mechanical dimensions. By providing the first through hole 21 in the mass block 2 such that the first through hole 21 communicates with the upper and lower sides of the mass block 2, gas can flow through the first through hole 21 when moving up and down the mass block 2, thereby reducing gas damping. More specifically, the first through hole 21 is a square hole.
Referring to fig. 9, as an embodiment of the piezoresistive acceleration sensor provided by the present invention, the movable cavities respectively form open ports at two sides of the frame 1 in the sensing direction of the mass block 2;
piezoresistive acceleration sensor still includes:
a substrate 7 connected to the frame 1 to close an opening; and
a cover plate 8 connected to the frame 1 to close the other opening;
the surface of the mass block 2 facing the substrate 7 is provided with a limiting groove 22, the inner wall of the limiting groove 22 close to one side of the cover plate 8 is provided with a second through hole 23, the second through hole 23 penetrates through the mass block 2 along the sensing direction of the mass block 2, and the substrate 7 is provided with a limiting protrusion 71 which is used for abutting against the inner wall of the limiting groove 22 close to one side of the cover plate 8 and limiting the minimum distance between the mass block 2 and the substrate 7.
During production, the gas damping of the piezoresistive acceleration sensor is adjusted by adjusting the distance between the mass 2 and the substrate 7 and the cover plate 8. Meanwhile, the substrate 7 and the cover plate 8 seal the two open ports to protect the structure in the movable cavity, so that batch wafer level packaging can be realized, and the packaging cost is greatly reduced.
The piezoresistive acceleration sensor of the invention adopts the stress concentration structure of the sensitive thin beam 41 while ensuring high natural frequency, obtains larger sensitivity, has very small gas damping, and limits the position of the mass block 2 by arranging the limit groove 22 and the limit bulge 71 in order to prevent the sensitive beam 3, the first support beam 5 and other structures from being broken when receiving larger acceleration. When the mass block 2 moves close to the substrate 7, the limiting bulge 71 is inserted into the limiting groove 22, so that the top end of the limiting bulge 71 is abutted against the bottom surface of the limiting groove 22, the mass block 2 is prevented from being excessively large in displacement, and the sensing beam 3, the measuring section 4, the first supporting beam 5, the second supporting beam 6 and other structures are prevented from being broken. During the insertion of the stopper projection 71 into the stopper groove 22, the gas in the stopper groove 22 can be discharged through the second through-hole 23.
Specifically, the substrate 7, the frame 1 and the cover plate 8 adopt a three-layer structure of silicon-silicon bonding, and the mass block 2 moves up and down between the substrate 7 and the cover plate 8. The limiting groove 22 is a square hole, the side length of the cross section of the limiting groove is 120 micrometers, the cross section of the limiting bulge 71 is a square with the side length of 116 micrometers, and the gap between the limiting bulge 71 and the inner wall of the limiting groove 22 is 2 micrometers. The second through hole 23 has a square cross section and a sectional area smaller than that of the stopper groove 22.
The present invention also provides a mobile device comprising: any one of the piezoresistive acceleration sensors described above.
The mobile equipment provided by the invention has the beneficial effects that: compared with the prior art, the mobile equipment provided by the invention has the advantages that the piezoresistive acceleration sensor is adopted, and the piezoresistive acceleration sensor can be prevented from being damaged when the acceleration direction of the mobile equipment is different from the sensitive direction of the piezoresistive acceleration sensor in the mobile equipment. The mobile device can be a mobile phone, a balance car, an automobile, an unmanned aerial vehicle and other devices which can move and need to detect acceleration.
The present invention is not limited to the above preferred embodiments, and any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. A piezoresistive acceleration sensor, characterized in that it comprises:
the frame (1) is internally provided with a movable cavity;
the mass block (2) is movably arranged in the movable cavity;
the two ends of the long shaft of the sensitive beam (3) are respectively connected with the frame (1) and the mass block (2) through a measuring section (4) provided with a pressure-sensitive element (43); and
the two ends of the long shaft are respectively connected with the middle part of the sensitive beam (3) and the frame (1), and the rigidity of the first support beam (5) in the sensing direction of the mass block (2) is smaller than that of the first support beam in the direction perpendicular to the sensing direction of the mass block (2);
the thickness of the first supporting beams (5) in the sensing direction of the mass block (2) is smaller than the thickness of the sensitive beams (3) in the sensing direction of the mass block (2).
2. The piezoresistive acceleration sensor according to claim 1, characterized in that: the measuring section (4) comprises a sensitive thin beam (41); two ends of a long shaft of the sensitive thin beam (41) are respectively connected with the end part of the sensitive beam (3) and the mass block (2); the width direction of the sensitive thin beam (41) is perpendicular to the sensing direction of the mass block (2), the width direction of the sensitive beam (3) is perpendicular to the sensing direction of the mass block (2), and the width of the sensitive thin beam (41) is smaller than that of the sensitive beam (3); one side of the sensitive thin beam (41) in the width direction is provided with a minimum distance limiting block (42), and the minimum distance limiting block (42) is located between the end face of the sensitive beam (3) and the mass block (2).
3. The piezoresistive acceleration sensor according to claim 2, characterized in that: the thickness direction of the sensitive thin beam (41) is parallel to the sensing direction of the mass block (2), the thickness direction of the sensitive beam (3) is parallel to the sensing direction of the mass block (2), and the thickness of the sensitive thin beam (41) is smaller than that of the sensitive beam (3); the pressure-sensitive element (43) is arranged on one side of the sensitive thin beam (41) in the thickness direction.
4. The piezoresistive acceleration sensor according to claim 1, characterized in that: the sensitive beam (3) is located the activity intracavity and be on a parallel with quality piece (2) are close to the side of sensitive beam (3), first supporting beam (5) are located the activity intracavity and be in sensitive beam (3) are kept away from one side of quality piece (2), first supporting beam (5) with sensitive beam (3) parallel arrangement.
5. The piezoresistive acceleration sensor according to any of the claims 1 to 4, characterized in that: the piezoresistive acceleration sensor further comprises:
and two ends of a long shaft of the second supporting beam (6) are respectively connected with the mass block (2) and the frame (1), and the thickness of the second supporting beam (6) in the sensing direction of the mass block (2) is smaller than that of the sensitive beam (3) in the sensing direction of the mass block (2).
6. The piezoresistive acceleration sensor according to claim 5, characterized in that: the second support beam (6) comprises:
a main body section (61) which is positioned in the movable cavity and is parallel to the side of the mass block (2) close to the main body section (61);
the first bending section (62) is arranged at an included angle with the main body section (61), one end of the first bending section is connected with one end of the main body section (61), and the other end of the first bending section is connected with the mass block (2); and
and the second bending section (63) is arranged at an included angle with the main body section (61), one end of the second bending section is connected with the other end of the main body section (61), and the other end of the second bending section is connected with the mass block (2).
7. The piezoresistive acceleration sensor according to any of the claims 1 to 4, characterized in that: the mass block (2) is provided with a plurality of first through holes (21), the first through holes (21) penetrate through the mass block (2) along the sensing direction of the mass block (2), and the first through holes (21) are rectangular holes.
8. The piezoresistive acceleration sensor according to any of the claims 1 to 4, characterized in that: the movable cavity is provided with an opening respectively at two sides of the frame (1) in the sensing direction of the mass block (2);
the piezoresistive acceleration sensor further comprises:
a substrate (7) connected to the frame (1) and closing one of the openings; and
a cover plate (8) connected to the frame (1) to close the other opening;
the quality piece (2) face the surface of substrate (7) is equipped with spacing groove (22), spacing groove (22) are close to the inner wall of apron (8) one side is equipped with second perforating hole (23), second perforating hole (23) are followed quality piece (2) sensing direction runs through quality piece (2), substrate (7) be equipped with be used for with spacing groove (22) are close to the inner wall butt and the restriction of apron (8) one side quality piece (2) with spacing arch (71) of the minimum interval of substrate (7).
9. A mobile device, comprising: the piezoresistive acceleration sensor of any one of claims 1 to 8.
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