CN105785073A - Piezoresistive acceleration sensor and manufacturing method thereof - Google Patents
Piezoresistive acceleration sensor and manufacturing method thereof Download PDFInfo
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- CN105785073A CN105785073A CN201410815643.1A CN201410815643A CN105785073A CN 105785073 A CN105785073 A CN 105785073A CN 201410815643 A CN201410815643 A CN 201410815643A CN 105785073 A CN105785073 A CN 105785073A
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Abstract
The invention provides a piezoresistive acceleration sensor and a manufacturing method thereof. The sensor is improved by comprising a sensitive structure part. The left and right sides of a mass block in the sensitive structure are symmetrically provided with four mutually independent sensitive girders. Each sensitive girder is provided with a force-sensitive resistor. The two sides of the four sensitive girders are respectively provided with one support girder for supporting the mass block. The force-sensitive resistors are arranged on the mutually independent sensitive girders, so that the widths of the sensitive girders are reduced. Therefore, the influence of the sensitive girders on the stiffness coefficient of the sensitive structure is significantly reduced, so that the high sensitivity and the high figure of merit are realized. The sensitive girders are arranged closer to the centerline of the mass block, thus being smaller in deflection. The paraxial sensitivity is reduced. The support girders are closer to the edge of the mass block, thus being large in the arm of force. Therefore, the twist of the mass block, caused by the paraxial acceleration, can be better inhibited. The upper surfaces of the support girders are lower and are free of any oxidation layer. Therefore, the structural deflection, caused by the stress of the oxidation layer, can be reduced. The thickness of the sensitive girders is larger than the thickness of the support girders, so that the stress concentration can be achieved. As a result, the sensitivity and the figure of merit are improved.
Description
Technical field
The present invention relates to a kind of piezoresistance type acceleration sensor and preparation method thereof, particularly relate to a kind of utilize different-thickness support beam and sensitive beam to piezoresistance type acceleration sensor improving sensor performance and preparation method thereof.
Background technology
Micro-mechanical accelerometer is micro electronmechanical integrated system (MicroElectroMechanicalSystems, MEMS) one of pillar product of technical field, have that size is little, cost is low, high reliability, have a wide range of applications in fields such as consumer electronics product, automotive electronics, Industry Control and national defence.Micro-mechanical accelerometer can be divided into again pressure resistance type, piezoelectric type, tunnel type, condenser type etc. by Cleaning Principle.Wherein, resistance-type accelerometer has the advantages such as interface circuit is simple, capacity of resisting disturbance is strong, processing technique is simple.
Body micro mechanical technology is the common method making piezoresistance type acceleration sensor.Body micromechanics piezoresistance type acceleration sensor adopts sandwich structure.So-called sandwich structure is made up of three-decker: upper cover plate, movable sensitive structure and lower cover.Wherein movable sensitive structure adopts beam-mass block structure, is namely supported mass block structure by several beam, makes force sensing resistance on beam, when there being acceleration, mass produces displacement makes beam bend, thus producing stress on beam, measuring stress by force sensing resistance and just can obtain accekeration.Upper and lower cover plates provides protection for movable structure, also makes position limiting structure in upper and lower cover plates, the displacement of mass during restriction high overload, it is to avoid structural failure.
Sensitivity and bandwidth are the important indicator of static characteristic and the dynamic characteristic characterizing acceleration transducer respectively.But, be there is contradiction by the two index in the requirement of structure.In general, the structure coefficient of stiffiness is more little, mass quality is more big, then sensitivity is more high, bandwidth is more low；On the contrary, the structure coefficient of stiffiness is more big, mass quality is more little, then sensitivity is more low, bandwidth is more high.Therefore, the product figure of merit as acceleration transducer of sensitivity and bandwidth it is generally adopted.The figure of merit is more high, then combination property is more good.
For piezoresistance type acceleration sensor, sensitivity is directly proportional to beam upper surface maximum stress, and bandwidth is directly proportional to mesomerism circular frequency, therefore can use the product figure of merit S as sensitive structure of beam upper surface maximum stress and resonant frequencyTf.For the sensitive structure of two-end fixed beam-mass block structure, its figure of merit STfIt is similar to and is directly proportional to the square root of mass and beam volume ratio:
Owing to the minimum dimension of beam is determined by process conditions, it is difficult to reduce.When size sensor reduces, figure of merit STfAlso reduce.More seriously, resonant frequency increases with structure scaled down, when size sensor reduces, in order to ensure sensitivity and resonant frequency in the reasonable scope, it is necessary to suitably increases the size of beam, causes figure of merit STfReduce further.Therefore, sensitive structure is optimized to improve the S of structureTfThe figure of merit is a challenge of acceleration transducer design.
Another design difficulty of acceleration transducer is in that the suppression to paraxonic sensitivity.Acceleration is vector, there is x, three components of y and z, ideally single-axis acceleration sensors should be only sensitive to one-component, but practical devices is generally all sensitive to three components, suppress need not the sensitivity (paraxonic sensitivity) of component be another subject matter of sensor design as far as possible.
The Stress match of sensitive structure is also the design difficulty of acceleration transducer.Beam mass sensitive structure counter stress is sensitive.When beam surface exists oxide layer, the thermal stress in oxide layer can cause structure to have the flexure of micron dimension, causes device performance to decline and even lost efficacy.Conventional method is first by bulk silicon micromachining technology, beam district is thinning, then makes force sensing resistance, so structurally can form the oxide layer of symmetry by lower surface, it is achieved Stress match.But the poor compatibility of the method and integrated circuit technology.General integrated circuit factory does not provide bulk silicon micromachining service, does not allow the silicon chip having been carried out bulk silicon micromachining to enter factory yet.Therefore desirably work flow is the processing first carrying out force sensing resistance electric bridge in integrated circuit foundries, then carries out bulk silicon micromachining.And this flow process must solve Stress match problem structure.
Summary of the invention
The shortcoming of prior art in view of the above, it is an object of the invention to provide a kind of piezoresistance type acceleration sensor and preparation method thereof, low and to easily paraxonic being produced the problem of sensitive reaction and overcoming the difficulty of conventional acceleration sensor Stress match difference for solving the figure of merit of acceleration transducer in prior art.
For achieving the above object and other relevant purposes, the present invention provides a kind of piezoresistance type acceleration sensor, and described piezoresistance type acceleration sensor at least includes: sensitive structure；It is bonded to the upper cover plate in this sensitive structure front and the lower cover at the back side thereof respectively；Described sensitive structure includes: rectangle outer rim, be positioned at the mass of described rectangle outer rim center；Described mass is respectively symmetrically relative to two groups of opposite side of described rectangle outer rim；Described mass be respectively arranged on the left side and the right side two support beams that are fixing and that be connected between described mass and rectangle outer rim；Four sensitive beam being connected between described mass and described rectangle outer rim it are respectively provided with between two described support beams of every side, the described mass left and right sides；Described sensitive beam, mass and the respective upper surface of rectangle outer rim are generally aligned in the same plane；Described sensitive beam more described support beam more integrated distribution is near described mass central axis in left-right direction；Being positioned at described four sensitive beam of described mass the same side, described central axis about described mass is symmetrical each other to be one group between two；The head of described each sensitive beam or afterbody are respectively equipped with a force sensing resistance；The force sensing resistance four sensitive beam in closest with the described central axis of described mass position consistency in respective sensitive beam；With the described central axis of the described mass force sensing resistance in four farthest sensitive beam position consistency in respective sensitive beam；Described support beam and the respective lower surface of described sensitive beam are generally aligned in the same plane and the upper surface of described support beam is lower than the upper surface of described sensitive beam；The width of described sensitive beam is much smaller than the width of described support beam；Described each sensitive beam is provided with and connects the metal lead wire at force sensing resistance two ends in this sensitive beam；The width of described sensitive beam is slightly wider than the width of described force sensing resistance and metal lead wire.
Preferably, closest with the described central axis of the described mass described force sensing resistance in described four sensitive beam is positioned close to the head position of each sensitive beam of this mass；The tail position of each sensitive beam of this mass it is located remotely from the described central axis of described mass described force sensing resistance in farthest described four sensitive beam.
Preferably, closest with the described central axis of the described mass described force sensing resistance in described four sensitive beam is located remotely from the tail position of each sensitive beam of this mass；The head position of each sensitive beam of this mass it is positioned close to the described central axis of described mass described force sensing resistance in farthest described four sensitive beam.
Preferably, the upper surface of described sensitive beam is provided with oxide layer；The upper surface non-oxidation layer of described support beam.
Preferably, described upper cover plate and lower cover are bonded to the upper and lower surface of described rectangle outer rim respectively；Space below described mass and between described lower cover is provided with the buffer stopper of described lower cover.
The present invention also provides for the manufacture method of a kind of piezoresistance type acceleration sensor, and this manufacture method at least includes: (1) provides a silicon base, and makes described force sensing resistance in the front of described silicon base；(2) corrosion barrier layer is made respectively at the front and back of this silicon base；(3) etch the described corrosion barrier layer at the described silicon base back side to exposing the described silicon base back side, form corrosion window；(4) corrode the described silicon base back side along described corrosion window until the thickness that thickness is described sensitive beam of the remaining silicon fiml of corrosion area, form the back side of described sensitive structure, it does not have the part that is corroded forms described mass；(5) the described metal lead wire being connected to described force sensing resistance two ends is made in the front of described sensitive structure；(6) make described lower cover and described lower cover is bonded to the back side of described sensitive structure；(7) etching the described metal lead wire both sides in thinning described silicon base front, form concave regions, the thickness of described concave regions is the thickness of described support beam；(8) penetrate described silicon base front, formed by the described rectangle outer rim being separated from each other, the front supporting the described sensitive structure that beam, sensitive beam and mass form；(9) make described upper cover plate and described upper cover plate is bonded to the front of described sensitive structure, after described rectangle outer rim scribing, forming described piezoresistance type acceleration sensor.
Preferably, the described corrosion barrier layer in described step (2) is silicon oxide, silicon nitride composite bed.
Preferably, the corrosive liquid corroding the described silicon base back side in described step (4) is alkaline anisotropic corrosive liquid.
Preferably, described alkaline anisotropic corrosive liquid includes KOH, TMAH corrosive liquid.
Preferably, the method that in described step (7), the thinning described metal lead wire both sides of etching form described concave regions is deep reaction ion etching method；The method penetrating described silicon base front in described step (8) is deep reaction ion etching method.
As mentioned above, piezoresistance type acceleration sensor of the present invention and preparation method thereof, have the advantages that the present invention adopts and wide and thin support beam and the narrow and sensitive beam common support mass of thickness, utilizing narrow and that the sensitive beam the moment of inertia of thickness is big feature to realize stress to concentrate, being significantly reduced sensitive beam to the impact of the structure coefficient of stiffiness thus improving the figure of merit.Sensitive beam it is produced near structure center line and realizes the suppression to paraxonic sensitivity in conjunction with electric bridge connected mode.The sensitive beam flexure of the present invention is less, it is possible to reduce paraxonic sensitivity；Supporting beam near mass edge, its arm of force is long, it is possible to suppress the mass that paraxonic acceleration causes to reverse around center line better；Support beam upper surface lower than mass and frame, and surface does not have oxide layer, it is possible to reduce the structural deflection that oxide layer stress causes.The thickness supporting beam is thin, it is possible to reduce the structure coefficient of stiffiness, improves sensitivity and the figure of merit.
Accompanying drawing explanation
Fig. 1 is shown as the piezoresistance type acceleration sensor sensitive structure schematic diagram of the present invention.
Fig. 2 is shown as the sensitive structure schematic top plan view of the present invention.
Fig. 3 is shown as the metal lead wire of the present invention and the connection diagram of force sensing resistance.
Fig. 4 is shown as the electric bridge connected mode schematic diagram of the force sensing resistance of the present invention.
Fig. 5 a to Fig. 5 e is shown as the manufacturing process structural representation of the piezoresistance type acceleration sensor of the present invention.
Element numbers explanation
11 upper cover plates
12 lower covers
101 rectangle outer rim
102 masses
103 support beam
104 sensitive beam
105 force sensing resistances
106 metal lead wires
13 silicon base
131 corrosion barrier layers
Detailed description of the invention
Below by way of specific instantiation, embodiments of the present invention being described, those skilled in the art the content disclosed by this specification can understand other advantages and effect of the present invention easily.The present invention can also be carried out by additionally different detailed description of the invention or apply, and the every details in this specification based on different viewpoints and application, can also carry out various modification or change under the spirit without departing from the present invention.
Refer to Fig. 1 to Fig. 5 e.It should be noted that, the diagram provided in the present embodiment only illustrates the basic conception of the present invention in a schematic way, then assembly that in graphic, only display is relevant with the present invention but not component count when implementing according to reality, shape and size drafting, during its actual enforcement, the kenel of each assembly, quantity and ratio can be a kind of random change, and its assembly layout kenel is likely to increasingly complex.
The described piezoresistance type acceleration sensor of the present invention at least includes: sensitive structure, upper cover plate and lower cover, and described upper cover plate is bonded in the front of described sensitive structure, and described lower cover is bonded in the back side of described sensitive structure.As it is shown in figure 1, Fig. 1 is shown as the piezoresistance type acceleration sensor sensitive structure schematic diagram of the present invention.Described sensitive structure in the present embodiment includes: rectangle outer rim 101, mass 102, as shown in Figure 1, described mass 102 is positioned at the center within described rectangle outer rim 101, and described mass 102 is respectively symmetrically relative to two groups of opposite side of described rectangle outer rim 101；Preferably, the cross section of described mass 102 is rectangle, as it can be seen, two groups of opposite side of described mass 102 cross section are parallel with two groups of opposite side of described rectangle outer rim 101 respectively.Preferably, described upper cover plate 11 and lower cover 12 are bonded to the upper and lower surface of described rectangle outer rim 101 respectively.Described sensitive structure also includes supporting beam 103, as shown in Figure 1, described mass 102 be respectively arranged on the left side and the right side two fixing and be connected to the support beam 103 between described mass 102 and rectangle outer rim 101, two of the described every side of mass 102 support two support beams 103 of beam 103 and opposite side and are respectively symmetrically, such as, in Fig. 1, on the left of described mass 102, the support beam 103 of top on the right side of beam 103 and mass 102 that supports of top is on same straight line, and this straight line parallel is in the described mass 102 center line (dotted line in Fig. 1) at left and right directions；The support beam 103 of mass 102 lower left and mass 102 bottom-right support beam 103 are in same straight line, and this straight line is also parallel with the described mass 102 center line at left and right directions.
The described sensor of the present invention also includes the sensitive beam 104 being arranged between described support beam 103, as shown in Figure 1, four sensitive beam 104 being connected between described mass 102 and described rectangle outer rim 101 it are respectively provided with between two described support beams 103 of every side, described mass 102 left and right sides, four sensitive beam 104 that on the left of described mass 102 two support between beam 103 are spaced parallel arranged, and four described sensitive beam 104 are in same plane；It is similarly positioned in two on the right side of described mass 102 four sensitive beam 104 supported between beam 103 and is spaced parallel arranged, and four described sensitive beam 104 are in same plane.As it is shown in figure 1, in the present invention, described sensitive beam 104, mass 102 and the respective upper surface of rectangle outer rim 101 are generally aligned in the same plane.In the present invention, it is arranged in the described sensitive beam 104 more described support beam 103 more integrated distribution of described mass 102 the same side in described mass 102 center (dotted line of Fig. 1) near axis in left-right direction；That is, the distance each other of four sensitive beam 104 on the left of described mass 102 is adjacent the distance between the sensitive beam 104 of position less than the upper left support beam 103 of this mass 102, the beam 103 that supports in described mass 102 lower left is adjacent the distance that the distance of sensitive beam 104 of position is adjacent between the sensitive beam 104 of position equal to the upper left support beam 103 of mass 102, and the position relationship supported between beam 103 and sensitive beam 104 and each sensitive beam 104 on the right side of described mass 102 is also such.And the position relationship between described mass 102 and described sensitive beam 104 is: be positioned at described four sensitive beam 104 of described mass 102 the same side, described central axis (dotted line in Fig. 1) about described mass 102 is symmetrical each other to be one group between two.Preferably, each sensitive beam 104 on the left of described mass 102 is parallel to each other and distance between adjacent sensitive beam 104 is equal to each other, the position relationship each other being positioned at four sensitive beam 104 on the right side of described mass 102 is also such, and it is symmetrical with the sensitive beam 104 being positioned on the right side of this mass 102 to be positioned at the sensitive beam 104 on the left of described mass 102.
As in figure 2 it is shown, Fig. 2 is shown as the sensitive structure schematic top plan view of the present invention.Head or the afterbody of described each sensitive beam 104 of the present invention are respectively equipped with a force sensing resistance 105, the force sensing resistance 105 four sensitive beam 104 in closest with the described central axis of described mass 102 (dotted line in Fig. 1) position consistency in respective sensitive beam 104；With the described central axis of described mass 102 force sensing resistance 105 in four farthest sensitive beam 104 position consistency in respective sensitive beam 104, that is, in Fig. 2, it is arranged in the sensitive beam 104 on the left of described mass 102, the wherein middle force sensing resistance 105 in two sensitive beam 104 and the force sensing resistance 105 in two sensitive beam 104 on the bright sensitive beam 104 being arranged on the right side of described mass 102 middle (central axis both sides) position consistency in respective sensitive beam 104；It is similarly positioned on the left of described mass 102 on the right side of force sensing resistance 105 in two sensitive beam 104 at most edge (adjacent with described support beam 103) and mass 102 position consistency in respective described sensitive beam 104 of the force sensing resistance 105 in two sensitive beam 104 at most edge.The head being in this sensitive beam 104 of so-called positional representation in described sensitive beam 104 or afterbody in the present embodiment, head refers to this sensitive beam 104 one end near described mass 102, and afterbody refers to one end that this sensitive beam 104 is connected with described rectangle outer rim 101.
A preferred embodiment of the present invention is, as in figure 2 it is shown, the described force sensing resistance 105 (being positioned at middle each two sensitive beam 104 of mass 102 left and right sides) in described four sensitive beam 104 closest with the described central axis of described mass 102 is positioned close to the head position of each sensitive beam 104 of this mass 102；The tail position of each sensitive beam 104 of this mass 102 it is located remotely from the described force sensing resistance 105 in described four sensitive beam 104 of the described central axis of described mass 102 distance farthest (each two sensitive beam 104 at edge, mass 102 left and right sides).The another kind of preferred version of the present invention is, the described force sensing resistance 105 described four sensitive beam 104 (be positioned at middle each two sensitive beam 104 of mass 102 left and right sides) in closest with the described central axis of described mass 102 is located remotely from the tail position of each sensitive beam 104 of this mass 102；The head position of each sensitive beam 104 of this mass 102 it is positioned close to the described force sensing resistance 105 in described four sensitive beam 104 of the described central axis of described mass 102 distance farthest (each two sensitive beam 104 at edge, mass 102 left and right sides).Preferably simultaneously, the upper surface of described sensitive beam 104 has oxide layer to cover；The upper surface non-oxidation layer of described support beam 103 covers.
As it is shown in figure 1, described support beam 103 and the described respective lower surface of sensitive beam 104 are generally aligned in the same plane and the upper surface of described support beam 103 is lower than the upper surface of described sensitive beam 104；The width of described sensitive beam 104 is much smaller than the width of described support beam 103；As it is shown on figure 3, Fig. 3 is shown as the metal lead wire 106 of the present invention and the connection diagram of force sensing resistance 105.Described each sensitive beam 104 is provided with and connects the metal lead wire 106 at force sensing resistance 105 two ends in this sensitive beam 104；The width of described sensitive beam 104 is slightly wider than the width of described force sensing resistance 105 and metal lead wire 106.
In the present invention, each force sensing resistance 105 is interconnected to form electric bridge, and as shown in Figure 4, Fig. 4 is shown as the electric bridge connected mode schematic diagram of the force sensing resistance 105 of the present invention.In Fig. 2, represent each force sensing resistance 105 with R1 to R8, be wherein positioned at four force sensing resistances 105 on the left of described mass 102 and be represented sequentially as R1, R2, R1, R5 from top to bottom；It is positioned at four force sensing resistances 105 on the right side of described mass 102 and is represented sequentially as R4, R3, R7, R8 from top to bottom.The electric bridge that each described force sensing resistance 105 connects into is as shown in Figure 4: wherein R2, R7, R8, R1 concatenate mutually；R5, R4, R3, R6 concatenate (tandem of each force sensing resistance 105 is to concatenate through the metal lead wire 106 being positioned in respective sensitive beam 104) mutually, and R2 and R5 is interconnected in supply voltage；R1 and R6 is connected with each other and ground connection；Between R7 and R8, it is provided with outfan simultaneously, between R4 and R3, is provided with outfan.These two outfans are used for measuring output voltage.
The operation principle of the described piezoresistance type acceleration sensor of the present invention with working method is: assume that described mass 102 is subject to the acceleration vertical with its surface；Sensitive beam 104 is stressed thus causing that the change of resistance value occurs the force sensing resistance 105 being positioned in described each sensitive beam 104 due to acceleration, owing to the ratio of increased resistance value to former resistance value is directly proportional to subjected to stress, and stress can directly reflect suffered acceleration magnitude；Therefore, the size of increased resistance value is used directly for the size of reflection acceleration.And practical situation is, mass 102 is generally not the acceleration being subject to merely its surface vertical, and actually acceleration in the horizontal direction also can be important, therefore, in order to offset the acceleration transducer sensitivity to paraxonic, each force sensing resistance 105 designs electric bridge method of attachment as above, and this connected mode can offset this piezoresistance type acceleration sensor acceleration in the horizontal direction, only calculates the effective acceleration in vertical direction.As previously mentioned, the change in resistance of force sensing resistance 105 can directly reflect the size of normal acceleration, therefore in test electric bridge the change in voltage of two described outfans can the change of direct reflected resistance, the change in voltage of two outfans namely tested out just can be directly changed into the size of acceleration in vertical direction.
The present invention also provides for the manufacture method based on the above piezoresistance type acceleration sensor, in the present embodiment, this manufacture method comprises the following steps: as shown in Fig. 5 a to Fig. 5 d, and Fig. 5 a to Fig. 5 d is shown as the manufacturing process structural representation of the piezoresistance type acceleration sensor of the present invention.
Step one: as shown in Figure 5 a a, it is provided that silicon base 13, and described force sensing resistance 105 is made in the front of described silicon base 13；The described force sensing resistance 105 made is eight force sensing resistances 105 as shown in Figure 2.
Step 2: in Fig. 5 a, the front and back in this silicon base 13 makes corrosion barrier layer 131 respectively, it is preferable that described corrosion barrier layer 131 is silicon oxide, silicon nitride composite bed.
Step 3: etch the described corrosion barrier layer 131 at described silicon base 13 back side to exposing described silicon base 13 back side, forms corrosion window.
Then step 4 is implemented: as shown in Figure 5 b, described silicon base 13 back side thickness that thickness is described sensitive beam 104 until the remaining silicon fiml of corrosion area is corroded along described corrosion window, form the back side of described sensitive structure, it does not have the part that is corroded forms described mass 102；Preferably, the corrosive liquid corroding described silicon base 13 back side is alkaline anisotropic corrosive liquid.Further preferably; in the present embodiment; described alkaline anisotropic corrosive liquid includes the corrosive liquids such as KOH, TMAH; the described alkaline anisotropic corrosive liquid that the present invention adopts is not limited to KOH, TMAH corrosive liquid, and other also all fall within present invention scope required for protection except the various alkaline anisotropic corrosive liquids of KOH, TMAH corrosive liquid.
Step 5: as shown in Figure 5 c, the described metal lead wire 106 being connected to described force sensing resistance 105 two ends is made in the front of described sensitive structure, the width of made metal lead wire 106 is as it is shown on figure 3, the width of the metal lead wire 106 made should be less than the width of described sensitive beam 104.Then step 6 is implemented: as fig 5d, make described lower cover 12 and described lower cover 12 is bonded to the back side of described sensitive structure, preferably, the space below described mass 102 and between described lower cover 12 is provided with the buffer stopper of described lower cover 12.The effect of described lower cover 12 is to provide protection for described sensitive structure, and the effect of described buffer stopper is that in restriction high overload situation, the displacement of mass 102 is too big, it is to avoid structural failure.
Step 7: etch described metal lead wire 106 both sides in thinning described silicon base 13 front, form concave regions, the thickness of described concave regions silicon is the thickness of described support beam 103, that is, as shown in Figure 1, the upper surface of described support beam 103 will lower than the upper surface of described sensitive beam 104, the corrosion barrier layer 131 of described support beam 103 upper surface is etched and removes simultaneously, therefore, the oxide layer that do not have of described support beam 103 upper surface covers, and described sensitive beam 104 upper surface is not owing to being etched, therefore, the upper surface of described sensitive beam 104 is provided with oxide layer.It is further preferred that etching the method that thinning described metal lead wire 106 both sides form described concave regions is deep reaction ion etching method.
Step 8: penetrate described silicon base 13 front, is formed by the described rectangle outer rim 101 being separated from each other, the front supporting the described sensitive structure that beam 103, sensitive beam 104 and mass 102 form, and the front of the described sensitive structure of formation is as shown in Figure 2.Wherein preferably, the method penetrating described silicon base 13 front is deep reaction ion etching method.
Step 9: as depicted in fig. 5e, makes described upper cover plate 11 and described upper cover plate 11 is bonded to the front of described sensitive structure, forming described piezoresistance type acceleration sensor after the scribing of described rectangle outer rim 101.So far, the described piezoresistance type acceleration sensor of the present invention is defined.
In sum, the present invention adopts and wide and thin supports beam and the narrow and sensitive beam common support mass of thickness, utilizes narrow and that the sensitive beam the moment of inertia of thickness is big feature to realize stress and concentrating, being significantly reduced sensitive beam to the impact of the structure coefficient of stiffiness thus improving the figure of merit.Sensitive beam it is produced near structure center line and realizes the suppression to paraxonic sensitivity in conjunction with electric bridge connected mode.The sensitive beam flexure of the present invention is less, it is possible to reduce paraxonic sensitivity；Supporting beam near mass edge, its arm of force is long, it is possible to suppress the mass that paraxonic acceleration causes to reverse around center line better；Support beam upper surface lower than mass and frame, and surface does not have oxide layer, it is possible to reduce the structural deflection that oxide layer stress causes.The thickness supporting beam is thin, it is possible to reduce the structure coefficient of stiffiness, improves sensitivity and the figure of merit.So, the present invention effectively overcomes various shortcoming of the prior art and has high industrial utilization.
Above-described embodiment is illustrative principles of the invention and effect thereof only, not for the restriction present invention.Above-described embodiment all under the spirit and category of the present invention, can be modified or change by any those skilled in the art.Therefore, art has usually intellectual such as modifying without departing from all equivalences completed under disclosed spirit and technological thought or change, must be contained by the claim of the present invention.
Claims (10)
1. a piezoresistance type acceleration sensor, it is characterised in that described piezoresistance type acceleration sensor at least includes:
Sensitive structure；It is bonded to the upper cover plate in this sensitive structure front and the lower cover at the back side thereof respectively；
Described sensitive structure includes: rectangle outer rim, be positioned at the mass of described rectangle outer rim center；Described mass is respectively symmetrically relative to two groups of opposite side of described rectangle outer rim；Described mass be respectively arranged on the left side and the right side two support beams that are fixing and that be connected between described mass and rectangle outer rim；
Four sensitive beam being connected between described mass and described rectangle outer rim it are respectively provided with between two described support beams of every side, the described mass left and right sides；Described sensitive beam, mass and the respective upper surface of rectangle outer rim are generally aligned in the same plane；It is positioned at the described sensitive beam more described support beam more integrated distribution of described mass the same side near described mass central axis in left-right direction；Being positioned at described four sensitive beam of described mass the same side, described central axis about described mass is symmetrical each other to be one group between two；
The head of described each sensitive beam or afterbody are respectively equipped with a force sensing resistance；The force sensing resistance four sensitive beam in closest with the described central axis of described mass position consistency in respective sensitive beam；With the described central axis of the described mass force sensing resistance in four farthest sensitive beam position consistency in respective sensitive beam；
Described support beam and the respective lower surface of described sensitive beam are generally aligned in the same plane and the upper surface of described support beam is lower than the upper surface of described sensitive beam；The width of described sensitive beam is much smaller than the width of described support beam；Described each sensitive beam is provided with and connects the metal lead wire at force sensing resistance two ends in this sensitive beam；The width of described sensitive beam is slightly wider than the width of described force sensing resistance and metal lead wire.
2. piezoresistance type acceleration sensor according to claim 1, it is characterised in that: the described force sensing resistance described four sensitive beam in closest with the described central axis of described mass is positioned close to the head position of each sensitive beam of this mass；The tail position of each sensitive beam of this mass it is located remotely from the described central axis of described mass described force sensing resistance in farthest described four sensitive beam.
3. piezoresistance type acceleration sensor according to claim 1, it is characterised in that: the described force sensing resistance described four sensitive beam in closest with the described central axis of described mass is located remotely from the tail position of each sensitive beam of this mass；The head position of each sensitive beam of this mass it is positioned close to the described central axis of described mass described force sensing resistance in farthest described four sensitive beam.
4. piezoresistance type acceleration sensor according to claim 1, it is characterised in that: the upper surface of described sensitive beam is provided with oxide layer；The upper surface non-oxidation layer of described support beam.
5. piezoresistance type acceleration sensor according to claim 1, it is characterised in that: described upper cover plate and lower cover are bonded to the upper and lower surface of described rectangle outer rim respectively；Space below described mass and between described lower cover is provided with the buffer stopper of described lower cover.
6. the manufacture method of the piezoresistance type acceleration sensor according to above-mentioned any one, it is characterised in that this manufacture method at least includes:
(1) silicon base is provided, and makes described force sensing resistance in the front of described silicon base；
(2) corrosion barrier layer is made respectively at the front and back of this silicon base；
(3) etch the described corrosion barrier layer at the described silicon base back side to exposing the described silicon base back side, form corrosion window；
(4) corrode the described silicon base back side along described corrosion window until the thickness that thickness is described sensitive beam of the remaining silicon fiml of corrosion area, form the back side of described sensitive structure, it does not have the part that is corroded forms described mass；
(5) the described metal lead wire being connected to described force sensing resistance two ends is made in the front of described sensitive structure；
(6) make described lower cover and described lower cover is bonded to the back side of described sensitive structure；
(7) etching the described metal lead wire both sides in thinning described silicon base front, form concave regions, the thickness of described concave regions silicon is the thickness of described support beam；
(8) penetrate described silicon base front, formed by the described rectangle outer rim being separated from each other, the front supporting the described sensitive structure that beam, sensitive beam and mass form；
(9) make described upper cover plate and described upper cover plate is bonded to the front of described sensitive structure, after described rectangle outer rim scribing, forming described piezoresistance type acceleration sensor.
7. the manufacture method of piezoresistance type acceleration sensor according to claim 6, it is characterised in that the described corrosion barrier layer in described step (2) is silicon oxide, silicon nitride composite bed.
8. the manufacture method of piezoresistance type acceleration sensor according to claim 6, it is characterised in that the corrosive liquid corroding the described silicon base back side in described step (4) is alkaline anisotropic corrosive liquid.
9. the manufacture method of piezoresistance type acceleration sensor according to claim 8, it is characterised in that described alkaline anisotropic corrosive liquid includes KOH, TMAH corrosive liquid.
10. the manufacture method of piezoresistance type acceleration sensor according to claim 6, it is characterised in that the method that in described step (7), the thinning described metal lead wire both sides of etching form described concave regions is deep reaction ion etching method；The method penetrating described silicon base front in described step (8) is deep reaction ion etching method.
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