CN102778586A - Differential capacitive micro-acceleration transducer and manufacturing method thereof - Google Patents
Differential capacitive micro-acceleration transducer and manufacturing method thereof Download PDFInfo
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- CN102778586A CN102778586A CN2012102871281A CN201210287128A CN102778586A CN 102778586 A CN102778586 A CN 102778586A CN 2012102871281 A CN2012102871281 A CN 2012102871281A CN 201210287128 A CN201210287128 A CN 201210287128A CN 102778586 A CN102778586 A CN 102778586A
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Abstract
The invention discloses a differential capacitive micro-acceleration transducer and a manufacturing method thereof. According to the method, the manufacturing of a movable mass block and an elastic beam is completed by using a bulk-silicon process, and the structure manufacturing and the releasing of a device structure are simultaneously completed by using a dry etching method; a movable electrode and the movable mass block are same in shape and size, so that an operation of repeated photoetching is avoided, thereby greatly simplifying the process; the stiffness of the designed elastic beam is small in the sensitive direction and large in the sensitive vertical direction, therefore, the elastic beam is higher in selectivity and anti-crosstalk capacity; and a device is simply and reliably packaged by using a wafer-level low-temperature vacuum aligned-bonding technology, thereby facilitating the large-scale manufacturing of the device. In addition, the differential capacitive micro-acceleration transducer disclosed by the invention adopts a variable-area type operating principle, so that the movable mass block is only damped by a sliding membrane in the process of moving, thereby improving the sensitivity.
Description
Technical field
The present invention relates to a kind of acceleration transducer, particularly relate to grating structure differential capacitance micro-acceleration sensor of the little extremely millimeter of a kind of manufacturing approach simple Devices size magnitude and preparation method thereof, belong to microelectron-mechanical and make the field.
Background technology
Miniature acceleration sensor is extensive being applied in the fields such as space guidance, vehicle control, robot, cell phone intelligent, industry mine locating, medical science with characteristics such as its volume are little, in light weight, power consumption is little, cost is low, easy of integration.In order to adapt to the restriction of different field measuring condition; The type of acceleration transducer is also varied, but capacitance acceleration transducer is because its good temperature characterisitic, high sensitivity, stability is high and process the main direction that characteristics such as simple always are research.
The sensitive mechanism that is applied to micro-acceleration sensor is a lot, and what bibliographical information was arranged at present mainly contains pressure resistance type, condenser type, temperature sensitive formula, resonant mode etc.Piezoresistive micro-accelerometer is through the movable mass induction acceleration; Input is converted into the deformation of elastic construction; Thereby cause the variation of the voltage dependent resistor (VDR) resistance that is produced on the elastic construction, convert changes in resistance into voltage or electric current variation through external circuitry again.Advantages such as it is simple that piezoresistance type acceleration sensor has processing technology, and measuring method is easy, and the linearity is good, but important disadvantages is also arranged, for example temperature effect is serious, unstable working condition, and sensitivity is low etc.
Condenser type micro-acceleration sensor is through the movable mass induction acceleration, utilizes parallel plate capacitor to convert the relative displacement of mass into changes in capacitance, through testing circuit the subtle change of electric capacity is converted into the variation of the voltage that is directly proportional with it again.Capacitance acceleration transducer has outstanding advantages such as temperature effect is low, power consumption is little, sensitivity is higher relatively, simple in structure, but extraneous acceleration only can cause the small variation of electric capacity (usually in 10-15 magnitude even lower), so method of testing is complicated.For capacity plate antenna, capacitance is:
Wherein ε is the specific inductive capacity of medium, A be pole plate over against area, d is a vertical range between pole plate.
Can know that by following formula capacitance acceleration sensor roughly is divided into two types by principle of work.One type is to become space type, and mass upper/lower electrode distance changes under the effect of acceleration, and adopting in most of documents more is the acceleration transducer that becomes space type; Another kind of is the variable area formula, and the parallel misalignment through upper/lower electrode makes the overlapping area change.The former is because electric capacity and the spacing relation of being inversely proportional to can cause the non-linear of capacitance variations, and it is non-linear to utilize feedback circuit to reduce, in addition because last bottom crown relative motion can produce bigger press-filming damping.The latter then is linear relation fully, and because what produce in the motion process is slide-film damping, this has improved the sensitivity of accelerometer greatly.
Given this, how to produce a kind of condenser type micro-acceleration sensor,, become present problem demanding prompt solution to overcome the complicated shortcoming of the small method of testing that causes of the capacitance variations non-linear and that acceleration causes of capacitance variations in the prior art.
Summary of the invention
The shortcoming of prior art in view of the above; The object of the present invention is to provide a kind of differential capacitance micro-acceleration sensor and preparation method thereof, be used for solving the non-linear of prior art capacitance variations and the small method of testing complicated problems that causes of capacitance variations that acceleration causes.
For realizing above-mentioned purpose and other relevant purposes, the present invention provides a kind of differential capacitance micro-acceleration sensor and preparation method thereof, may further comprise the steps at least:
1) substrate is provided, prepares metal level, and on said metal level, carry out photoetching and etching process is produced a pair of interdigitated fixed electorde and two fixed electorde contacts in the front of said substrate;
2) a structure substrate is provided, and said structure substrate back carry out photoetching and etching process prepare be used for discharging movable structure preset cavity and two electrodes are drawn through hole;
3) with the front and the step 2 of substrate described in the step 1)) described in the back side of structure substrate be bonded together;
4) from said structure substrate front it is thinned to target thickness after; At its front depositing metal layers, and on said metal level, carry out photoetching and etching process and form the figure that movable electrode, movable mass, elastic beam and fixed electorde are drawn through-hole structure;
5) litho pattern foundation said rapid 4) is drawn through hole through said structure substrate being carried out dry etching to obtain movable mass, elastic beam and two electrodes;
6) a cover plate substrate is provided, carries out photoetching and etching process is produced and the corresponding cover plate cavity of said movable mass at said cover plate substrate back;
7) front with structure substrate in cover plate substrate back in the said step 6) and the said step 5) is bonded together;
8) draw through hole through forming electrode on the cover plate substrate of deep etch technology in said step 7) of photoetching and silicon;
9) draw from said electrode through the routing mode and draw fixed electorde and movable electrode the through hole.
Alternatively, the material at the positive metal level that deposits of said structure substrate is Au, Al, Cu or Ag in the said step 4); Bonding technology in the said step 7) is a wafer level cryogenic vacuum bonding, and the bonding material of employing is glass paste, polymkeric substance or metal-to-metal adhesive; Said step 2) the on-chip electrode of structure is drawn through hole and the on-chip electrode of said step 5) cover plate and is drawn through hole and align in, is used for said fixed electorde and movable electrode are drawn; When the substrate in the said step 1) was glass sheet, the material of the metal level that on said glass sheet, deposits in this step 1) was Au, Al, Cu or Ag; Adopt anode linkage technology that the back side of substrate face and said structure substrate is bonded together in the said step 3).
Alternatively, when the substrate in the said step 1) was silicon chip, said step 1) also comprised:
1-1) substrate is provided, thermal oxide growth one deck monox in the front of said substrate;
1-2) at said step 1-1) front of substrate prepares the Au layer, and on said Au layer, carry out photoetching and etching process is produced a pair of interdigitated fixed electorde;
Said step 2) also comprise:
2-1) a structure substrate is provided, and at said structure substrate back thermal oxide growth one deck monox;
2-2) at said step 2-1) monox on carry out photoetching and etching process produce be used for discharging movable structure preset cavity and electrode is drawn through hole;
2-3) make the bonding contact ring at said structure substrate back.
Alternatively, the material of bonding contact ring is glass paste, polymkeric substance or metal-to-metal adhesive said step 2-3).
Alternatively, said structure substrate is silicon chip or SOI substrate; Said cover plate substrate is a silicon chip.
Alternatively, when said structure substrate is the SOI substrate, said step 2) also comprise:
2-1) a structure substrate is provided, at top layer silicon Film by Thermal Oxidation one deck monox of said structure substrate back;
2-2) on the silicon oxide layer of said structure substrate back, carry out photoetching and etching; Leave the corrosion window of said top layer silicon; Be mask then with the monox; The top layer silicon of said corrosion window is carried out etching until reaching the buried regions silicon oxide layer, with formation be used for discharging movable structure preset cavity and electrode is drawn through hole;
2-3) utilize dry etching with said step 2-2) in the said buried regions monox that exposes of structure substrate back etch away.
Another object of the present invention provides a kind of differential capacitance micro-acceleration sensor, comprises at least:
Substrate, its front have a pair of interdigitated fixed electorde and pair of stationary electrodes contact;
The structure substrate, the back side with a cavity is bonded on the said substrate, constitutes the electric capacity spacing through this cavity and said substrate surface, and the front has the palisade movable electrode; Corresponding said cavity top is hung with the palisade movable mass, and said movable mass both sides are connected to said structure substrate through some symmetrical elastic beams respectively; A pair of said fixed electorde contact also has two electrodes and draws through hole on the corresponding said substrate on said structure substrate;
The cover plate substrate, the back side with a cavity is bonded on the said structure substrate front, has constituted the movement clearance of said movable quality through this cavity and said structure substrate front; A pair of said fixed electorde contact and the on-chip movable electrode of structure on the corresponding said substrate also have two electrodes and draw through hole on said cover plate substrate, with realization said fixed electorde and movable electrode are drawn.
Alternatively, the material of said fixed electorde and movable electrode is Au, Al, Cu or Ag; Said elastic beam and movable mass are formed in the said structure substrate body material; Said elastic beam is symmetrically distributed in said movable mass both sides, and its number is 2, and said elastic beam be shaped as annular; The on-chip palisade movable mass of interdigitated fixed electorde on the said substrate and structure is formed the sensitization capacitance device; The direction of motion of the palisade movable mass in the said acceleration transducer is the edge direction parallel with this mass upper surface, belongs to acceleration transducer in the face.
Alternatively, said substrate is elected silicon chip or glass sheet as; Said structure substrate is for electing silicon chip or SOI substrate as; Said cover plate substrate is elected silicon chip as; When said structure substrate was the SOI substrate, said electric capacity spacing was the thickness sum of this SOI substrate top layer silicon and buried regions monox; Said cyclic spring beam and movable mass are formed in the substrate silicon of this SOI substrate.
As stated, a kind of differential capacitance micro-acceleration sensor of the present invention and preparation method thereof has following beneficial effect:
The present invention utilizes bulk silicon technological to accomplish the making of movable mass and elastic beam, also accomplishes the release of device architecture when accomplishing structure fabrication through dry etching; Movable electrode and movable mass are of similar shape and size, avoid the repetition photoetching, and technology is simplified greatly; The elastic beam of design is little in sensitive direction rigidity, and responsive vertical direction rigidity is big, has higher selectivity and anti-crosstalk ability; Utilize the wafer level cryogenic vacuum to aim at bonding techniques device is encapsulated simple and reliablely, be convenient to extensive manufacturing.In addition; Micro-acceleration sensor of the present invention has adopted variable area formula principle of work to make movable mass when motion, only receive slide-film damping; Improved sensitivity; And adopted palisade movable electrode and interdigital fixed electorde to make the bigger capacitance change of generation under the same acceleration effect, further reduced the detection difficulty of differential type electric capacity.Therefore, differential capacitance type micro-acceleration sensor of the present invention is simple in structure, and technology is easy to realize that measuring accuracy is high, the linearity is good, highly sensitive, is a kind of practicable solid-state micro accelerometer.
Description of drawings
Fig. 1 a～1i is shown as the differential capacitance micro-acceleration sensor manufacture craft schematic flow sheet in the embodiment of the invention one.
Fig. 2 a～2e is shown as the differential capacitance micro-acceleration sensor preparing department division technique schematic flow sheet in the embodiment of the invention two.
Fig. 3 a～3d is shown as the differential capacitance micro-acceleration sensor preparing department division technique schematic flow sheet in the embodiment of the invention three.
Fig. 4 is shown as the differential capacitance micro-acceleration sensor structural representation in the embodiment of the invention four.
Fig. 5 a～5b is shown as the equivalent electrical circuit and the principle of work synoptic diagram of the differential capacitance micro-acceleration sensor in the embodiment of the invention four
The element numbers explanation
1 substrate
2,4 metal levels
20 interdigitated fixed electordes
21 fixed electorde contacts
3 structure substrates
30 preset cavity
31,51 electrodes are drawn through hole
32 palisade movable mass
33 elastic beams
34 top layer silicon
35 buried regions monox
36 substrate silicon
40 movable electrodes
5 cover plate substrates
50 cover plate cavitys
6 glass paste bondings
7 fixed electordes lead-in wire
8 movable electrodes lead-in wire
9 silicon oxide layers
10 bonding contact rings
S1 ~ S9 step
AB, C direction
Embodiment
Below through specific instantiation embodiment of the present invention is described, those skilled in the art can understand other advantages of the present invention and effect easily by the content that this instructions disclosed.The present invention can also implement or use through other different embodiment, and each item details in this instructions also can be based on different viewpoints and application, carries out various modifications or change under the spirit of the present invention not deviating from.
Need to prove; The diagram that is provided in the present embodiment is only explained basic conception of the present invention in a schematic way; Satisfy only show in graphic with the present invention in relevant assembly but not component count, shape and plotted when implementing according to reality; Kenel, quantity and the ratio of each assembly can be a kind of random change during its actual enforcement, and its assembly layout kenel also maybe be more complicated.
See also Fig. 1 a～1i, Fig. 2 a～2e, Fig. 3 a～3d, Fig. 4 and Fig. 5 a～5b; Further specify a kind of differential capacitance type micro-acceleration sensor provided by the invention and preparation method thereof in conjunction with Figure of description; Different substrates that provide in according to the present invention and various structure substrate; The method for making of said acceleration transducer is also slightly different, is elaborated through various embodiment below.
Embodiment one
Of Fig. 1 a to 1i, present embodiment provides a kind of method for making of differential capacitance micro-acceleration sensor, may further comprise the steps:
Step S1: shown in Fig. 1 a; One glass substrate 1 is provided, passes through electron beam evaporation or vapor deposition layer of metal layer 2 in the front of said glass substrate 1, the material of this metal level 2 is elected Au temporarily as; But be not limited thereto, also can be conducting metals such as Al, Cu or Ag in other embodiments; On said metal level 2, carry out photoetching and etching process then and produce a pair of interdigitated fixed electorde 20 and two fixed electorde contacts 21.
Step S2: a structure substrate 3 is provided, and in the present embodiment, said structure substrate is elected silicon chip temporarily as, but is not limited to this, also can be other substrate in other embodiments, and various structure substrate technology has difference slightly; Carry out photoetching then forms and to preset cavity 30 and draw through hole 31 figures with electrode at said structure substrate 3 back sides; Then utilize dry method or wet corrosion technique to prepare to be used for the structure that cavity 30 and two electrodes are drawn through hole 31 that presets that discharges movable structure; This degree of depth that presets cavity 30 is the electric capacity spacing of said micro-acceleration sensor, and this electric capacity spacing changes according to the difference of the performance of the acceleration transducer of made.Be depicted as the sectional view of said structure silicon chip like Fig. 1 b.
Step S3: adopt anode linkage technology that the back side of structure substrate 3 described in the front of glass substrate 1 among the said step S1 and the said step S2 is bonded together; Anode linkage technology generally is only limited to glass-silicon bonding; Bonding temperature is 300 ℃～400 ℃, and bias voltage is 500V～1000V.Need to prove; When bonding; On the position of said structure substrate 3 corresponding said metal electrodes lead-in wires, erode away a loculus (not shown), said structure silicon chip 3 back sides can not be contacted with the metal electrode lead-in wire on said substrate 1 silicon chip, be depicted as the sectional view behind the bonding like Fig. 1 c.
Step S4: adopt chemical mechanical milling method or wet corrosion technique to carry out attenuate from said structure substrate 3 fronts; After being thinned to target thickness; Deposit layer of metal layers 4 through vapor deposition or electron beam evaporation process in structure substrate 3 fronts of said attenuate, in the present embodiment, the material of this metal level 4 is elected Au as; But be not limited thereto, also can be conducting metals such as Al, Cu or Ag in other embodiments; Just photoetching on said metal level 4 then, and it is corroded to form movable electrode 40, palisade movable mass 32 (being called for short movable mass 32), elastic beam 33 and fixed electorde respectively draw the figure of through hole 31 structures; It is corresponding in vertical direction with the fixed electorde contact 21 among the said step S1 that said electrode is drawn the figure of through hole 31 structures, can be communicated with this fixed electorde contact 21 so that the fixed electorde that the said structure substrate 3 of corrosion forms in subsequent step is drawn through hole 31; The metal level 4 of said movable mass 32 superstructures is as movable electrode 40; Said structure substrate 4 fronts will be corroded in subsequent step by the place that metal level 4 is covered, and remaining metal level 4 realizes that with the movable electrode 40 on the movable mass 32 electricity is connected on this structure substrate 3.Fig. 1 d is shown as the structure graph planimetric map after carrying out photoetching on the metal level in said structure silicon chip front.
Step S5: according to the litho pattern among the said rapid S4, through drawing through hole 31 to obtain movable mass 32, elastic beam 33 and two electrodes to not carried out dry etching by the structure substrate 3 of said metal level 4 said coverings.Said movable mass 32 is a grating structure, and its both sides are connected to said structure silicon chip 3 through some symmetrical elastic beams 33 respectively.Need to prove; Elastic beam 33 is shaped as annular in the present embodiment; Quantity is 2, but is not limited to this, the form of said in other embodiments elastic beam 32 and performance different change of quantity according to said acceleration transducer; The shape of for example said elastic beam 33 can be shape of straight beam or other symmetrical structure etc., and quantity can be 4,6 etc.Being depicted as along the sectional view of the AB direction of Fig. 1 d like Fig. 1 e, all is according to the cross section of the AB direction of Fig. 1 d (or Fig. 1 d AB direction in device architecture) in the sectional view structure of subsequent technique process flow diagram, is not giving unnecessary details in the subsequent step, hereby statement.
Step S6: shown in Fig. 1 f, provide one at cover plate substrate 5, present embodiment cover plate substrate 5 is elected silicon chip as; But be not limited thereto; Also can be other substrate among other embodiment, Ge substrate etc. for example is after photoetching is carried out at said cover plate substrate 5 back sides; Utilize dry method or wet corrosion technique to erode away and the corresponding cover plate cavity 50 of said movable mass, constituted the movement clearance of said movable mass 32 through this cover plate cavity 50 and said structure substrate 3 fronts.
Step S7: shown in Fig. 1 g; Adopt wafer level cryogenic vacuum packaged glass slurry bonding 6 technologies that the front of structure substrate 3 among cover plate substrate 5 back sides among the said step S6 and the said step S5 is bonded together; Glass paste bonding 6 technology have that technology is simple, bond strength is high, good sealing effect, production efficiency advantages of higher, are a kind of high yield, low cost packaging technique.But be not limited to the bonding technology in the present embodiment, can also adopt wafer level cryogenic vacuum encapsulation polymer-bound technology or metal-to-metal adhesive bonding technology etc. in other embodiments.Cover plate substrate 5 through bonding; Realized the wafer level Vacuum Package of said acceleration transducer; To prevent that movable structure in the said acceleration transducer from receiving the influence of factors such as dust in scribing and the assembling process, steam, causes the breaking-up of device or the decline of overall performance.
Need to prove; Behind said cover plate substrate 5 and structure silicon chip 3 bondings; Cover plate cavity 50 on this cover plate silicon chip 5 just in time covers on the movable mass 32 and elastic beam 33 on the said structure substrate 3, and has formed the free movement space of movable mass 32 with structure substrate 3 fronts.
Step S8: shown in Fig. 1 h; Cover plate substrate 5 fronts behind bonding are carried out photoetching and are drawn the corresponding electrode of through hole 51 structures with these cover plate substrate 5 backplates and draw through hole 51 figures to form; According to the figure of photoetching, and utilize dry method or wet-etching technology on said cover plate substrate 5, to etch electrode and draw through hole 51.Dry etching general using deep reaction ion etching technology, and wet etching adopts KOH solution to carry out the corrosion of silicon.
Need to prove; Electrode on the said cover plate substrate 5 is drawn through hole 51 and is drawn through hole 31 with the electrode on the structure substrate 3 and be connected in vertical direction; So that fixed electorde 20 is drawn; And be positioned at electrode on the cover plate substrate 5 and draw through hole 51 metal lead wire on the said structure substrate 3 is exposed, so that movable electrode 40 is drawn.
Step S9: shown in Fig. 1 i, draw from said electrode through the routing mode and to draw fixed electorde lead-in wire 7 and movable electrode lead-in wire 8 through hole 31 and 51, accomplish the making of condenser type micro-acceleration sensor.
In sum, the present invention utilizes bulk silicon technological to accomplish the making of movable mass and elastic beam, also accomplishes the release of device architecture when accomplishing structure fabrication through dry etching; The elastic beam of design is little in sensitive direction rigidity, and its responsive vertical direction rigidity is big, has higher selectivity, prevents to crosstalk; Adopted palisade movable electrode and interdigital fixed electorde to make the bigger capacitance change of generation under the same acceleration effect, and differential type capacitance detecting mode has further reduced detection difficulty; Utilize the cryogenic vacuum bonding techniques to realize the wafer level Vacuum Package of device; Adopt variable area formula differential capacitance principle of work, guarantee the device good working performance.The utility model acceleration sensor structure is simple in addition, and technology is easy to realize that measuring accuracy is high, the linearity is good, highly sensitive, is a kind of practicable solid-state micro accelerometer.
Embodiment two
2a to 2e as shown in the figure is depicted as the part process chart of the making differential capacitance micro-acceleration sensor in the present embodiment; Present embodiment provides the method for making of another kind of differential capacitance micro-acceleration sensor; With embodiment one difference be that the substrate that provides in the present embodiment is a silicon substrate; Therefore, the difference of substrate has caused technologic difference a little, and specifically the difference of processing step is as follows:
When a silicon substrate 1 was provided, the step S1 of said embodiment one also comprised:
S1-1: shown in Fig. 2 a, a substrate 1 is provided, thermal oxide growth one deck silicon oxide layer 9 in the front of said silicon substrate, this silicon oxide layer 9 is with 2 insulation of the metal level in said silicon substrate and the subsequent step.
S1-2: shown in Fig. 2 b; On the silicon oxide layer 9 of said step S1-1 substrate, prepare layer of metal layer 2 through vapor deposition or electron beam evaporation process; 2 materials of metal level described in the present embodiment are elected Au temporarily as; But be not limited to this, can also elect conductive metallic materials such as Al, Cu or Ag as in other embodiments.On said metal level 2, carry out photoetching and etching process then and produce a pair of interdigitated fixed electorde 20 and two fixed electorde contacts 21.Be depicted as the planimetric map that said substrate forms fixed electorde like Fig. 2 b.
A kind of step S2 of said embodiment also comprises:
S2-1: shown in Fig. 2 c, a structure substrate 3 is provided, the structure substrate 3 in the present embodiment is elected silicon chip temporarily as, then at said structure substrate 3 back side thermal oxide growth one deck monox 9.
S2-2: on said structure substrate 3 back side silicon oxide layers 9, carry out photoetching and form and to preset cavity 30 and draw through hole 31 figures with electrode; Utilize dry method or wet corrosion technique to prepare to be used for the structure that cavity 30 and two electrodes are drawn through hole 31 that presets that discharges movable structure then; But this degree of depth that presets cavity 30 is the dynamic condenser spacing of said micro-acceleration sensor, and this electric capacity spacing changes according to the difference of the performance of the acceleration transducer of made.Be depicted as the sectional view of structure substrate like Fig. 2 d.
S2-3: on said structure substrate 3 back sides and substrate face silicon oxide layer 9, make bonding contact ring 10; Bonding contact ring 10 is elected Au-Au bonding ring temporarily as in the present embodiment; But be not limited thereto, in other embodiments, bonding contact ring 10 also can be glass paste, polymkeric substance or metal-to-metal adhesive.Be depicted as the sectional view of structure substrate like Fig. 2 d.
Other step and process chart in the present embodiment are identical with embodiment one, repeat no more at this.Be depicted as the structural drawing of the final acceleration transducer that forms in the present embodiment like Fig. 2 e.
Embodiment three
3a to 3d as shown in the figure is depicted as the part process chart of the making differential capacitance micro-acceleration sensor in the present embodiment; Present embodiment provides the method for making of another kind of differential capacitance micro-acceleration sensor; With embodiment one difference be that the structure substrate that provides in the present embodiment is the SOI substrate; Therefore, the difference of structure substrate has also caused technologic difference a little, and specifically the difference of processing step is as follows:
When a soi structure substrate 3 was provided, the step S2 of said embodiment one also comprised:
S2-1: shown in Fig. 3 a, a structure substrate 3 is provided, top layer silicon 36 Film by Thermal Oxidation one deck monox 9 at said structure substrate 3 back sides.
S2-2: shown in Fig. 3 b; On the silicon oxide layer 9 at said structure substrate 3 back sides, carry out photoetching and etching; Leaving the corrosion window of said top layer silicon 36, is mask with silicon oxide layer 9 then, adopts on dry method or the top layer silicon 36 of wet corrosion technique to said corrosion window and carries out etching until reaching buried regions monox 37; With formation be used for discharging movable structure preset cavity 30 and electrode is drawn through hole 31 structures, remove the monox 9 on the said top layer silicon at last.
S2-3: shown in Fig. 3 c, the said buried regions monox 37 that utilizes dry etching that structure substrate 3 back sides among the said step S2-2 are exposed etches away.
Need to prove that with the acceleration transducer that this method is made, the electric capacity spacing can accurately be controlled, and is the thickness sum of this SOI substrate top layer silicon and buried regions monox; Said cyclic spring beam and movable mass are formed in the substrate silicon of this SOI substrate, and the thickness of said cyclic spring beam and movable mass also can accurately be controlled.
Other step and process chart in the present embodiment are identical with embodiment one, repeat no more at this.Be depicted as the structural drawing of the final acceleration transducer that forms in the present embodiment like Fig. 3 d.
Embodiment four
As scheme institute 4 and show that another object of the present invention provides a kind of differential capacitance micro-acceleration sensor, in the vacuum cavity environment that is applied to seal, comprise substrate 1, structure substrate 3 and cover plate substrate 5 at least.
Said substrate 1 is arranged at the bottom of said micro-acceleration sensor; Substrate described in the present embodiment 1 is elected glass temporarily as; But be not limited to this, also be chosen as silicon chip or germanium wafer etc. in other embodiments, its front has a pair of interdigitated fixed electorde 20 and pair of stationary electrodes contact 21.The material of fixed electorde described in the present embodiment 20 and fixed electorde contact 21 is elected Au temporarily as, but is not limited to this, also is chosen as Al, Cu or Ag in other embodiments.
Said structure substrate 3 has the back side of presetting cavity 30 and is bonded on the said substrate 1, presets cavity 30 through this and constitutes the electric capacity spacing with said substrate 1 surface, and the front has palisade movable electrode 40; Corresponding said cavity 30 tops of presetting are hung with palisade movable mass 32, and said movable mass 32 both sides are connected to said structure substrate 3 through some symmetrical elastic beams 33 respectively; A pair of said fixed electorde contact 21 also has two electrodes and draws through hole 31 on the corresponding said substrate 1 on said structure substrate 3.Structure substrate 3 is elected silicon chip temporarily as in the present embodiment, but is not limited to this, also can be soi structure substrate 3 in other embodiments.When said structure substrate was the SOI substrate, said electric capacity spacing was this structure substrate 3 top layer silicon 36 and the thickness sum of buried regions monox 35, and said elastic beam 33 and movable mass 32 are formed in the substrate silicon 34 of this structure substrate 3 (with reference to figure 3d).
Need to prove; Elastic beam 33 is shaped as annular in the present embodiment; Quantity is 2, but is not limited to this, the form of said in other embodiments elastic beam 33 and performance different change of quantity according to said acceleration transducer; The shape of for example said elastic beam 33 can be shape of straight beam or other symmetrical structure etc., and quantity can be 4,6 etc.
The back side that said cover plate substrate 5 has a cover plate cavity 50 is bonded on said structure substrate 3 fronts, has constituted the movement clearance of said movable quality 32 through this cover plate cavity 50 and said structure substrate 3 fronts; Movable electrode 40 on the corresponding said substrate 1 on a pair of said fixed electorde contact 21 and the structure substrate 3 also has two electrodes and draws through hole 51 on said cover plate substrate 5, with realization said fixed electorde 20 is drawn with movable electrode 40.Cover plate substrate 5 in the present embodiment is elected silicon chip temporarily as, but is not limited to this, also can be germanium substrate etc. in other embodiments.
Need to prove; Said micro-acceleration sensor structure applications is in the vacuum cavity environment of sealing; And the direction of motion of the palisade movable mass 32 in this micro-acceleration sensor is edge and the parallel direction of these mass 32 upper surfaces, belongs to acceleration transducer in the face.
Principle and effect in order further to illustrate differential capacitance micro-acceleration sensor of the present invention see also Fig. 5 a to 5b, as shown are the fundamental diagram of this acceleration transducer.
Said movable mass 32 among the present invention is the acceleration of detection level direction planar, has good selectivity.This movable mass 32 is one with movable electrode 30 simultaneously; The movable electrode 30 of grating structure can produce big capacitance variations with the fixed electorde 20 of interdigital structure under the state of little displacement; And become relatively stricter linear relationship, the number and the length of movable mass 32 grid through changing the interdigital number of interdigital fixed electorde 20 and length and grating structure can continue to increase changes in capacitance.When movable mass 32 moved, the identical positive and negative different variation of size can take place with two groups of detection electric capacity that last movable electrode 30 constitutes in following fixed electorde 20.When the direction C in pressing Fig. 5 b moved, big if an electric capacity (C1) becomes, then another one electric capacity (C2) just diminished.Through detecting the size of differential capacitance, just can extrapolate the size of acceleration.It is thus clear that accelerometer of the present invention other accelerometers relatively has bigger output, better linearity degree and less air damping, and follow-up Design of Interface Circuit is also simple relatively with making.
In sum, a kind of differential capacitance micro-acceleration sensor that the present invention proposes and preparation method thereof, this method utilizes bulk silicon technological to accomplish the making of movable mass and elastic beam, also accomplishes the release of device architecture when accomplishing structure fabrication through dry etching; Movable electrode and movable mass are of similar shape and size, avoid the repetition photoetching, and technology is simplified greatly; The elastic beam of design is little in sensitive direction rigidity, and responsive vertical direction rigidity is big, has higher selectivity and anti-crosstalk ability; Utilize the wafer level cryogenic vacuum to aim at bonding techniques device is encapsulated simple and reliablely, be convenient to extensive manufacturing.In addition; Micro-acceleration sensor of the present invention has adopted variable area formula principle of work to make movable mass when motion, only receive slide-film damping; Improved sensitivity; And adopted palisade movable electrode and interdigital fixed electorde to make the bigger capacitance change of generation under the same acceleration effect, and differential type capacitance detecting mode has further reduced detection difficulty.Therefore, differential capacitance type micro-acceleration sensor of the present invention is simple in structure, and technology is easy to realize that measuring accuracy is high, the linearity is good, highly sensitive, is a kind of practicable solid-state micro accelerometer.So the present invention has effectively overcome various shortcoming of the prior art and the tool high industrial utilization.
The foregoing description is illustrative principle of the present invention and effect thereof only, but not is used to limit the present invention.Any be familiar with this technological personage all can be under spirit of the present invention and category, the foregoing description is modified or is changed.Therefore, have common knowledge the knowledgeable in the affiliated such as technical field, must contain by claim of the present invention not breaking away from all equivalence modifications of being accomplished under disclosed spirit and the technological thought or changing.
Claims (15)
1. the method for making of a differential capacitance micro-acceleration sensor is characterized in that, may further comprise the steps at least:
1) substrate is provided, prepares metal level, and on said metal level, carry out photoetching and etching process is produced a pair of interdigitated fixed electorde and two fixed electorde contacts in the front of said substrate;
2) a structure substrate is provided, and said structure substrate back carry out photoetching and etching process prepare be used for discharging movable structure preset cavity and two electrodes are drawn through hole;
3) with the front and the step 2 of substrate described in the step 1)) described in the back side of structure substrate be bonded together;
4) from said structure substrate front it is thinned to target thickness after; At its front depositing metal layers, and on said metal level, carry out photoetching and etching process and form the figure that movable electrode, movable mass, elastic beam and fixed electorde are drawn through-hole structure;
5) litho pattern foundation said rapid 4) is drawn through hole through said structure substrate being carried out dry etching to obtain movable mass, elastic beam and two electrodes;
6) a cover plate substrate is provided, carries out photoetching and etching process is produced and the corresponding cover plate cavity of said movable mass at said cover plate substrate back;
7) front with structure substrate in cover plate substrate back in the said step 6) and the said step 5) is bonded together;
8) draw through hole through forming electrode on the cover plate substrate of deep etch technology in said step 7) of photoetching and silicon;
9) draw from said electrode through the routing mode and draw fixed electorde and movable electrode the through hole.
2. the method for making of differential capacitance micro-acceleration sensor according to claim 1 is characterized in that: the material at the positive metal level that deposits of said structure substrate in the said step 4) is Au, Al, Cu or Ag.
3. the method for making of differential capacitance micro-acceleration sensor according to claim 1 is characterized in that: the bonding technology in the said step 7) is a wafer level cryogenic vacuum bonding, and the bonding material of employing is glass paste, polymkeric substance or metal-to-metal adhesive.
4. the method for making of differential capacitance micro-acceleration sensor according to claim 1; It is characterized in that: the on-chip electrode of structure is drawn through hole and the on-chip electrode of said step 5) cover plate and is drawn through hole and align said step 2), is used for said fixed electorde and movable electrode are drawn.
5. the method for making of differential capacitance micro-acceleration sensor according to claim 1 is characterized in that: when the substrate in the said step 1) was glass sheet, the material of the metal level that on said glass sheet, deposits in this step 1) was Au, Al, Cu or Ag; Adopt anode linkage technology that the back side of substrate face and said structure substrate is bonded together in the said step 3).
6. the method for making of differential capacitance micro-acceleration sensor according to claim 1 is characterized in that, when the substrate in the said step 1) was silicon chip, said step 1) also comprised:
1-1) substrate is provided, thermal oxide growth one deck monox in the front of said substrate;
1-2) at said step 1-1) front of substrate prepares the Au layer, and on said Au layer, carry out photoetching and etching process is produced a pair of interdigitated fixed electorde;
Said step 2) also comprise:
2-1) a structure substrate is provided, and at said structure substrate back thermal oxide growth one deck monox;
2-2) at said step 2-1) monox on carry out photoetching and etching process produce be used for discharging movable structure preset cavity and electrode is drawn through hole;
2-3) make the bonding contact ring at said structure substrate back.
7. the method for making of differential capacitance micro-acceleration sensor according to claim 6 is characterized in that: the material of bonding contact ring is glass paste, polymkeric substance or metal-to-metal adhesive said step 2-3).
8. the method for making of differential capacitance micro-acceleration sensor according to claim 1 is characterized in that: said structure substrate is silicon chip or SOI substrate; Said cover plate substrate is a silicon chip.
9. the method for making of differential capacitance micro-acceleration sensor according to claim 8 is characterized in that: when said structure substrate is the SOI substrate, and said step 2) also comprise:
2-1) a structure substrate is provided, at top layer silicon Film by Thermal Oxidation one deck monox of said structure substrate back;
2-2) on the silicon oxide layer of said structure substrate back, carry out photoetching and etching; Leave the corrosion window of said top layer silicon; Be mask then with the monox; The top layer silicon of said corrosion window is carried out etching until reaching the buried regions silicon oxide layer, with formation be used for discharging movable structure preset cavity and electrode is drawn through hole;
2-3) utilize dry etching with said step 2-2) in the said buried regions monox that exposes of structure substrate back etch away.
10. a differential capacitance micro-acceleration sensor is characterized in that, comprises at least:
Substrate, its front have a pair of interdigitated fixed electorde and pair of stationary electrodes contact;
The structure substrate, the back side with a cavity is bonded on the said substrate, constitutes the electric capacity spacing through this cavity and said substrate surface, and the front has the palisade movable electrode; Corresponding said cavity top is hung with the palisade movable mass, and said movable mass both sides are connected to said structure substrate through some symmetrical elastic beams respectively; A pair of said fixed electorde contact also has two electrodes and draws through hole on the corresponding said substrate on said structure substrate;
The cover plate substrate, the back side with a cavity is bonded on the said structure substrate front, has constituted the movement clearance of said movable quality through this cavity and said structure substrate front; A pair of said fixed electorde contact and the on-chip movable electrode of structure on the corresponding said substrate also have two electrodes and draw through hole on said cover plate substrate, with realization said fixed electorde and movable electrode are drawn.
11. according to the described differential capacitance micro-acceleration sensor of claim 10, it is characterized in that: the material of said fixed electorde and movable electrode is Au, Al, Cu or Ag.
12. differential capacitance micro-acceleration sensor according to claim 10 is characterized in that: said elastic beam and movable mass are formed in the said structure substrate body material; Said elastic beam is symmetrically distributed in said movable mass both sides, and its number is 2, and said elastic beam be shaped as annular.
13. differential capacitance micro-acceleration sensor according to claim 10 is characterized in that: the on-chip palisade movable mass of interdigitated fixed electorde on the said substrate and structure is formed the sensitization capacitance device; The direction of motion of the palisade movable mass in the said acceleration transducer is the edge direction parallel with this mass upper surface, belongs to acceleration transducer in the face.
14. differential capacitance micro-acceleration sensor according to claim 10 is characterized in that: said substrate is elected silicon chip or glass sheet as; Said structure substrate is for electing silicon chip or SOI substrate as; Said cover plate substrate is elected silicon chip as.
15. differential capacitance micro-acceleration sensor according to claim 14 is characterized in that: when said structure substrate was the SOI substrate, said electric capacity spacing was the thickness sum of this SOI substrate top layer silicon and buried regions monox; Said cyclic spring beam and movable mass are formed in the substrate silicon of this SOI substrate.
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