CN1069972C - Double-electrode monocrystal silicon capacitance acceleration sensor and mfg. method therefor - Google Patents
Double-electrode monocrystal silicon capacitance acceleration sensor and mfg. method therefor Download PDFInfo
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- CN1069972C CN1069972C CN97121626.6A CN97121626A CN1069972C CN 1069972 C CN1069972 C CN 1069972C CN 97121626 A CN97121626 A CN 97121626A CN 1069972 C CN1069972 C CN 1069972C
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Abstract
The present invention relates to a double-electrode monocrystal silicon capacitance acceleration transducer. The transducer comprises a quality block, at least two elastic beams, a plurality of long and thin pieces composed of a silicon epitaxial layer with holes at the bottom and a pedestal for supporting the elastic beams, wherein the upper part of the pedestal is composed of a silicon epitaxial layer, the lower part is separated from a substrate by an oxidizing layer, the function of electric insulation is performed, and the side surface of each of the long and thin pieces is used for being manufactured into a moving electrode of a transversely changeable capacitor. The quality block and the bottom surface of each of the long and thin pieces are used for being manufactured into a moving electrode of a longitudinally changeable capacitor, and a fixed electrode of the transversely changeable capacitor is composed of a plurality of long and thin pieces electrically insulated from the substrate and rigidly connected with the substrate, and a fixed electrode of the longitudinally changeable capacitor is composed of a substrate surface.
Description
The present invention relates to a kind of capacitance acceleration sensor, particularly relate to a kind of two vertical direction acceleration of measuring, is the bipolar electrode capacitance acceleration sensor of material acceleration sensitive unit with monocrystalline silicon.
The capacitance acceleration sensor of micromachined is an acceleration transducer of new generation, and its development foundation is an ic manufacturing technology.Owing to have the many advantages that have as integrated circuit (IC) products, this capacitance acceleration sensor is subjected to the user and welcomes once putting goods on the market, and application extension is very fast, has now exceeded the extent of occupation of traditional acceleration transducer.Most typical application is a trigger of making anti-collision system for automobile, and its annual requirement is up to ten million, and every year also will be with very high speed increase from now on.
Early stage capacitance acceleration sensor product, adopt two-sided body micromachining technology to make silicon single crystal capacitance-sensitive unit, because two-sided body micromachined complicate fabrication process, with the general manufacturing process poor compatibility of integrated circuit, thereby production cost is high for a long time, applies being subjected to serious obstruction.
Newer product adopts the surface micromachined technology to make the responsive unit of polysilicon capacitance, simplified manufacturing process, and production cost reduces.The responsive unit of this capacitance acceleration sensor, its inertial mass is a ＂ H ＂ shape, the slender arm of ＂ H ＂ is similar to tether, and elastic beam is fixed on the substrate that supports usefulness.Inertial mass can move freely on the plane of vertical tether.The identical finger-like polysilicon strip of a string shape size stretches out from the mass both sides, is the float electrode of plate condenser, and another string finger-like polysilicon strip stretches out from substrate, with above-mentioned polysilicon strip alternately, be the fixed electorde of plate condenser.
Be to make the responsive unit of polysilicon, isolation oxidation silicon layer that must deposit one deck is thicker on the substrate of making electronic detection circuit is drawn hole processing to silicon oxide layer, to form fixed leg.The thicker polysilicon of deposit one deck on silicon oxide layer is used as responsive first structured material then.Fixed leg is on the circuit connecting wire of elastic beam and one-stage amplifier.Polysilicon is carried out ion inject, increasing its conductance, and then carry out photoetching corrosion processing, to form mass, beam, finger-like bar, and electrode.For avoiding mass and substrate adhesion behind the sacrifice layer corrosion, the corrosion of isolation oxidation silicon layer must be with a kind of special ＂ born-free ＂ technology.Metallize at last and form the silicon oxynitride passivation layer.
The capacitance acceleration sensor that can survey the surface micromachined of 50 acceleration of gravity (g) has been successfully used to automobile air-bag system, but on performance and price, still has many problems.
In general, automobile air-bag system requires to measure the acceleration of vertical and horizontal both direction, and the capacitance acceleration sensor of surface micromachined can only be surveyed the acceleration of a direction, and two sensors need be installed by each system for this reason.
There are many difficulties in the acceleration transducer that needs low g in many practical applications with the low g acceleration transducer of surface micromachined technology manufacturing.For guaranteeing that hanging down the g acceleration transducer has sufficiently high sensitivity, inertial mass must be enough big, and the method that increases inertial mass has two, and the one, the area of increase mass, the 2nd, the thickness of increase mass.The former can cause the monolithic productive rate to reduce, and production cost improves, and the latter is subjected to the restriction of polysilicon film deposition technology, being limited in scope of increase.Have two kinds of dissimilar stress on the silicon chip of capping oxide in the polysilicon film of deposit: growth stress and thermal stress, these two kinds of stress all increase and increase along with thickness.Stress is crossed conference and is caused that polysilicon film breaks, even comes off, and occurs for avoiding this situation, and the thickness of polysilicon film generally is controlled within 2 microns.
In fact, the capacitance acceleration sensor of surface micromachined belongs to the polysilicon sensor, and under periodic mechanical stress effect, polysilicon can constantly be wriggled, produce hysteresis or cool work hardening phenomenon, cause the stability of sensor and reliability to become serious problems.
The adhesion of responsive unit is the principal organ that the capacitance acceleration sensor of surface micromachined lost efficacy.Adhesion was lost efficacy and was divided two kinds of forms, i.e. bonding ＂ when ＂ flushing back bonding ＂ and ＂ work.After bonding ＂ appeared at the isolation oxidation silicon layer of corrosion sacrifice after the ＂ flushing, this moment, hanging beam and mass were touched substrate by stretch bending, become permanent adhesion owing to the surface tension effects of rinse solution in dry run.＂ when work bonding ＂ appears at responsive unit and is exposed in the moist ambiance, and steam condenses into water droplet in can be between responsive unit and the substrate narrow gap, because the surface tension effects of water droplet, responsive unit is by stretch bending and substrate stickup.
Solve the problem of the early stage and recent product existence of above-mentioned micromachined capacitance acceleration sensor, main aim of the present invention just.
One of the object of the invention is to propose a kind of capacitance acceleration sensor, and the manufactured materials of its acceleration sensitive unit is low dislocation, the monocrystalline silicon of low defective.
Two of the object of the invention is to propose a kind of capacitance acceleration sensor, adopts the manufacturing of monohedron micromachining technology, to simplify technology, reduces cost.
Three of the object of the invention is to propose a kind of capacitance acceleration sensor, the acceleration of two vertical direction of energy measurement.
Four of the object of the invention is to propose a kind of capacitance acceleration sensor, the acceleration of energy measurement lower range or ultralow range.
Five of the object of the invention is to propose a kind of capacitance acceleration sensor, and its mass can have bigger gap between elastic beam and substrate, and elastic beam has bigger rigidity, can avoid mass, produces adhesion between elastic beam and substrate.
Above-mentioned purpose and other purposes can realize by the double-electrode monocrystal silicon capacitance acceleration sensor that the present invention proposes.The responsive unit of double-electrode monocrystal silicon capacitance acceleration sensor comprises a rectangle inertial mass, at least two elastic beams, the strip that some shapes are identical with size.Responsive unit is made of the part silicon epitaxy layer, and the pedestal that supports the central dip of responsive unit also is made of the part silicon epitaxy layer, and the silicon epitaxy layer shop is applied on a monocrystalline substrate.One air buffer separates sensitivity unit with substrate, the monoxide interlayer is arranged between supporting platform seat and the substrate, and insulating effect electrifies.The float electrode that the strip side of responsive unit is used for making the transverse variable capacitor, the float electrode that the bottom surface of whole responsive unit is used for making vertical variable condenser.The fixed electorde of transverse variable capacitor is by some and substrate electrical isolation but constitute with the hardwired strip of substrate, and vertically the fixed electorde of variable condenser is made of the bottom surface of air buffer.
When moving under inertial mass is being parallel to the external force effect of substrate surface direction, the lateral capacitance acceleration transducer changes its capacitance, the acceleration that produces corresponding to parallel direction.When inertial mass moved under the external force effect perpendicular to the substrate surface direction, vertically capacitance acceleration sensor changed its capacitance, corresponding to the acceleration of vertical direction generation.
The manufacturing of the double-electrode monocrystal silicon capacitance acceleration sensor that the present invention proposes is with the formation of porous silicon, and the peculiar property that oxidation and corrosion are had is the basis.Porous silicon is a kind of monocrystalline silicon that contains a large amount of micropores, is silicon carries out galvanic corrosion in dense HF product.One of characteristic of porous silicon is that its formation is relevant with the doping type and the doping content of silicon, and the selectivity of various different dopant materials is arranged as: n
+＞p
+＞p＞n.According to this arrangement, porous silicon can optionally be formed on the p around the n-type silicon island
+-distinguish, and n-type silicon island is surrounded fully.Another characteristic of porous silicon is that porous causes great surface area, thereby has extremely strong chemical reaction ability.Porous silicon can change silicon dioxide under lower temperature, and can optionally erode from silicon substrate with high speed in the silicon etchant of dilution.The application of porous silicon in SOI (silicon on insulator) just is based on these characteristics.
In the manufacture method of double-electrode monocrystal silicon capacitance acceleration sensor, monocrystalline substrate resistivity is the 0.5-20 ohm-cm, silicon epitaxy layer resistivity is the 0.5-20 ohm-cm, and the buried regions square resistance is the 5-20 ohms/square, and the surface impurity concentration of high concentration superficial layer is 10
18-10
20/ cubic centimetre, the anodic oxidation diaphragm can be golden chromium composite bed.
Describe structure of the present invention and method for making in detail below in conjunction with implementing accompanying drawing.
Fig. 1 represents the skeleton view of the double-electrode monocrystal silicon capacitance acceleration sensor that the present invention proposes.
Fig. 2 represents the part cutting skeleton view of the double-electrode monocrystal silicon capacitance acceleration sensor that the present invention proposes.
Fig. 3 represents the simplification principle of work synoptic diagram of the double-electrode monocrystal silicon capacitance acceleration sensor that the present invention proposes.
Fig. 4 to Figure 13 represents that each main manufacturing step of double-electrode monocrystal silicon capacitance acceleration sensor that the present invention proposes partly cuts skeleton view.
Double-electrode monocrystal silicon capacitance acceleration sensor such as Fig. 1, Fig. 2 and shown in Figure 3.The responsive unit of this sensor comprises 105, two unsettled elastic beam 104a of a unsettled rectangle inertial mass, 104b, some unsettled strips 106.Mass is by elastic beam 104a, and 104b holds up, and elastic beam is on the extended line of mass 105 cross central lines, is arranged in the both sides of mass 105 respectively.Strip 106 stretches out from 105 liang long relatively limits of mass, and with elastic beam 104a, 104b is parallel, is arranged in elastic beam 104a respectively, the both sides of 104b.
The pedestal 110a of the central dip that two elastic beams are relative with two respectively, 110b links to each other, and pedestal 110a, 110b stand on the substrate 101, by pedestal 110a, 110b, unsettled responsive unit is finally supported by substrate 101.Pedestal 110a, folder one deck oxide 111 between 110b and the substrate 101, buffer action electrifies.Also have some strips 107,108 to stand on these landing strips and responsive first unsettled strip 106 staggered uniformly-spaced arrangements on the substrate 101.Landing strip 107,108 links to each other by ＂ shape connecting portion and the latticed rectangular block 112,113 of ＂.Also separate between landing strip 107,108 and the substrate 101 by oxide skin(coating) 111.
The two relative side of unsettled strip 106 adheres to the float electrode 115 of transverse variable capacitor, the fixed electorde 116 of relative therewith landing strip 107,108 side attachment transverse variable capacitors.The float electrode 120 of vertical variable condenser is adhered in the bottom surface of unsettled rectangle mass 105 and unsettled strip 106, and the substrate surface relative with unsettled strip 106 bottom surfaces with unsettled rectangle mass 105 adheres to the fixed electorde 119 of vertical variable condenser.The float electrode 115,120th of transverse variable capacitor and vertical variable condenser, electricity communicates, these two the unsettled elastic beam of electrodes process bottom surfaces, supporting platform seat 110a, the side of 110b links to each other with external circuit with the high concentration diffusion layer of front edge 118.The fixed electorde 116 of transverse variable capacitor is by the coupled rectangular block side and the high concentration diffusion layer 118 of front edge, and the metal film lines that are arranged in the rectangular block front link to each other with external circuit.Vertically the fixed electorde 119 of variable condenser links to each other with external circuit with epitaxial loayer side high concentration diffusion layer 118 by the substrate frame.
Unsettled mass 105, unsettled elastic beam 104a, 104b and unsettled strip 106 all are the parts of epitaxial loayer 102 on the substrate 101, they are separated, and the bottom is hollowed out and it is hung on the substrate 101.Landing pedestal 110a, 110b, rectangular block 112,113, landing strip 107,108, the ＂ shape connecting portion of ＂ also is the part of epitaxial loayer 102 on the substrate 101, the oxide interlayer 111 of its bottom is an oxidized porous silicon.The electrode of all variable condenser is formed by the impurity diffusion layer 118 of high concentration, and its doping type and substrate and epitaxial loayer are different, and to form PN junction, buffer action electrifies.
Float electrode 115 is formed transverse variable capacitor 121 with the fixed electorde 116 that adheres to landing strip 107 sides, float electrode 115 is formed transverse variable capacitor 122 with the fixed electorde 116 that adheres to landing strip 108 sides, and float electrode 120 is formed vertical variable condenser 123 with the fixed electorde 119 of attachment substrate 101 inside surfaces.When sensor during in horizontal arrow direction shown in Figure 3, transverse variable capacitor 121 and 122 appearance value change round about, acceleration with the motion of reaction level direction, when sensor during in vertical arrows direction shown in Figure 3 motion, vertically the appearance value of variable condenser 123 changes, with the acceleration of reaction movement in vertical direction.
Fig. 4 to Figure 13 represents the manufacturing process flow of double-electrode monocrystal silicon capacitance acceleration sensor.Manufacturing step one mainly is the diffusion region that forms high concentration as shown in Figure 4.The stock that is used for making is (100) crystal orientation, single-sided polishing, the N-type monocrystalline silicon piece 201 of resistivity 2-8 ohm-cm.Silicon chip put in 1100 degrees centigrade the oxidation furnace, logical wet oxygen 90 minutes forms the thick thermal oxide layer of 9000 dusts at silicon chip surface.Silicon chip after the oxidation is carried out photoetching corrosion, form the window of diffusion usefulness in oxide layer, this window is determined the scope of the shared silicon chip of sensor sensing unit.Then with have spread window oxide layer for sheltering, carry out two the step arsenic diffusions.The first step is arsenic predeposition, and the arsenic source is As
2O
3, furnace temperature is 480 degrees centigrade, deposition time is 1 hour.Second step spread for advancing, 1225 degrees centigrade of furnace temperature, and the time is 5 hours, produces dark 4 microns N thus
+ Diffusion layer 202.
The method that the N+ layer also can adopt ion to inject forms.Still carry out the ion injection to have the oxide layer that spreads window for sheltering, injection condition is: air source A sH
4, dosage 1 * 10
16/ square centimeter, 180 kiloelectron-volts of energy.Carry out thermal annealing after the injection, 1200 degrees centigrade of temperature, 4 hours time, atmosphere N
2: O
2=10: 1.
Manufacturing step two is having grown silicon epitaxial loayer on the silicon chip of diffusion region as shown in Figure 5.Before the growth, silicon chip is immersed in the HF solution of dilution and erodes oxide remaining on the silicon chip.After silicon chip is gone into stove, remove the superficial layer of the silicon chip of 0.3-0.5 micron thickness earlier with the HCl gas attack. epitaxial growth condition: source of the gas SiCl
4+ H
2, 1150 degrees centigrade of furnace temperature, growth rate 0.7-0.8 micron/minute.The epitaxial growth time is controlled, to obtain thick 5 microns, the epitaxial loayer 203 of resistivity 2-8 ohm-cm.
Manufacturing step three mainly is to form anodic oxidation protection figure as shown in Figure 6.When silicon chip is immersed in dense HF solution, with the silicon chip anode when adding a voltage, can generate porous silicon at silicon chip surface, this electrochemical reaction is called anodic oxidation.For forming porous silicon in the silicon chip surface selectivity, silicon chip surface must form the protection figure.The anodic oxidation protective seam must be stood the corrosion of HF under the situation of energising.The composite bed of polysilicon and silicon nitride can meet this requirement; silicon nitride is an insulating material, can stop anode current to pass through, under the situation that no anode current passes through; the polysilicon that contacts with HF is not to be subjected to the HF corrosion, therefore is subjected to the silicon chip surface of this composite bed protection not generate porous silicon.Because the side of composite bed is exposed in the HF solution, still has the problem of lateral encroaching, in order to reduce the lateral encroaching of silicon nitride, silicon nitride must be grown under than higher temperature, and has than higher silicone content, and this silicon nitride is called low stress nitride silicon.
For forming the composite bed 204 of anti-HF corrosion, the thick Si of deposit 1500 dusts on the epitaxial loayer of silicon chip of elder generation
3N
4Deposition conditions: 835 degrees centigrade of temperature, air pressure 300 milli torrs, prescription NH
3=16 cc/min, SiH
2Cl
2=64 cc/min.Consequent Si
3N
4Corrosion rate in 49%HF be the 40-50 dust/minute.The undoped polycrystalline silicon of deposit 1 micron thickness then, deposition conditions: air pressure 300 milli torrs, 605 degrees centigrade of temperature, source of the gas SiH
4, airflow rate 120 side's cm per minute.
Form composite bed protection figure and adopt plasma etching technology, the masking layer aluminium of plasma etching.The formation of aluminium lamination is by sputter, and sputtering condition: 4.5 kilowatts of power, air pressure 6 is torrs in the least, tracking speed 10 cm per minute.Carry out photoetching corrosion and form the aluminium masking graphics, the corrosion of aluminium aluminium corrosive liquid, its prescription is 16H
3PO
4: 1HNO
3: 1Hac: 2H
2O.Plasma etching divided for three steps carried out, and corroded polysilicon, etching condition: source of the gas Cl earlier
2: He=18: 40, air pressure 425 milli torrs, consequent corrosion rate be 3200 dusts/minute.Corrode Si then
3N
4, etching condition: source of the gas SF
6: He=13: 21, air pressure 250 milli torrs, consequent corrosion rate be 1100 dusts/minute.This two steps plasma etching has formed composite bed protection figure; promptly in composite bed, formed anodic oxidation window 205; the anodic oxidation of carrying out subsequently will be limited in the window 205; the epi-layer surface in the zone beyond the window 205 is subjected to the protection of composite bed; anodic oxidation neither takes place, also not by electrolyte corrosion.
The 3rd step plasma etching is the epitaxial loayer in the corrosion window 205.In order to make N
+Anodic oxidation takes place and is transformed into porous silicon in buried regions 202, and the window 205 in the anodic oxidation masking graphics must be deepened, and passes epitaxial loayer 203, until buried regions 202.The condition of plasma etching epitaxial loayer 203 is identical with the corrosion polysilicon.Because etchant gas Cl
2The silicon of article on plasma bombardment just has than higher corrosion rate, and corrosion is by the strict depth direction that is limited in graphical window 205, and the groove that corrosion forms has very high aspect ratio.
Manufacturing step four mainly is that anodic oxidation forms porous silicon as shown in Figure 7.The used reaction tank of anodic oxidation is two ponds, chamber, two Room in pond are separated by silicon chip, the indoor HF solution that is full of, every pond feeds a platinum electrode, and the platinum electrode relative with the silicon chip back side connects the anode of external dc power, and anode current enters the silicon chip back side through HF solution, HF solution plays liquid electrode, metal electrode is not made at the silicon chip back side in addition, and anode reaction occurs in the front of silicon chip, and the platinum electricity of silicon chip front side faces is as negative electrode.
The prescription of HF solution is 40%HF, 10% water and 50% absolute ethyl alcohol.The effect of absolute ethyl alcohol is the surface tension that reduces solution, makes reaction product H
2Discharge easily, to improve the configuration of surface of porous silicon.
The silicon materials of different doping types and doping content, it forms the required anode voltage of porous silicon, and universal law is N
+Silicon is lower than P
+, N, P silicon.According to this rule, anode voltage and anode current are elected 4 volts respectively as, 30 milliamperes/square centimeter.Anodic oxidation is only at N
+Silicon area takes place, and the average growth rate of the porous silicon that is produced is 1.3 microns/minute.
During anodic oxidation, HF solution enters anodic oxidation window 205, the N type silicon that epitaxial loayer 203 and substrate 201 are arranged that contacts with HF solution and the N of buried regions 202
+Silicon because anode voltage is controlled in lower level, has only N
+Silicon generation anode reaction, anode reaction does not take place in N type silicon, and therefore reaction is only along N
+Buried regions 202 to center deployment, is treated whole N from the edge
+After buried regions 202 became porous silicon 206, reaction stopped automatically, and N type silicon area does not generate porous silicon.
Manufacturing step five mainly is to form oxidized porous silicon as shown in Figure 8.Because porous silicon hole multilist area is big, its oxidation rate than the high 20-30 of normal silicon is doubly utilized this characteristic, porous silicon can be transformed into thicker oxidized porous silicon.Oxidation divided for three steps carried out, the first step, and silicon chip heated 1 hour in 300 degrees centigrade dried oxygen, to stablize the structure of porous silicon, prevented that the micropore avalanche from appearring in the thermal treatment under higher temperature subsequently.Second step, in 800 degrees centigrade steam, carry out oxidation, the control oxidization time makes the transverse width 208 of the oxidized porous silicon 207 of generation be approximately 40 microns.The 3rd step, in 1090 degrees centigrade steam, handled 40 minutes, to increase the density of oxidized porous silicon, improve its electrical insulation capability.
The monox that thermal oxide generates, the original silicon volume of its volume ratio is big, does not cause carrying out than higher step influence back step operation in order to make after the oxidation of porous silicon buried regions at silicon chip surface, and tackling after its oxidation volume increases part and compensates.Way is that the porosity of control porous silicon is 45%, and the space that its hole causes just in time is the part that volume increases after the oxidation.The porosity of porous silicon is relevant with anodic oxidation condition, and the concentration of the HF solution of selecting for use previously and the size of anode current are determined according to the porosity that obtains 45%.
After porous silicon becomes oxidized porous silicon, the supporting platform seat 210a of central dip, 210b, the bottom of latticed rectangular block 211 becomes electrical isolation.Simultaneously formed thermal oxide silicon layer 209 at silicon chip surface.
Manufacturing step six mainly is the buried porous silicon of corrosion as shown in Figure 9.To in epitaxial loayer, open the window 212 of corrosion of porous silicon buried regions before the corrosion.The aluminium lamination of elder generation's deposit 1 micron thickness on silicon chip carries out photoetching corrosion then and forms the aluminium masking graphics for this reason.Use the plasma etching polysilicon successively, Si
3N
4, and epitaxial silicon.The source of the gas of corrosion polysilicon and epitaxial silicon is Cl
2, corrosion Si
3N
4Use SF
6, diluents is all used He.
The corrosion of porous silicon 1N-NaOH solution, corrosion is at room temperature carried out.With this understanding, NaOH solution is incorrosive to oxidized porous silicon, and is very little to the corrosion of silicon.After the corrosion, the original shared volume of porous silicon is hollowed out the epitaxial loayer on its top and substrate separation.Remember that for forming corrosion window, this part epitaxial loayer is cut, just form cavity 218, mass 213, elastic beam 214a, 214b and strip 215 after therefore hollowing out down below.Meanwhile also formed the bottom strip 216,217 of oxidized porous silicon interlayer and the ＂ shape connecting portion 219 of ＂ have been arranged.
Manufacturing step seven mainly is to form the diffusion window as shown in figure 10.The low temperature SiO of elder generation's deposit 1 micron thickness on silicon chip
2Layer, deposition conditions are air pressure 300 milli torrs, 450 degrees centigrade of temperature, gas source SiH
4Flow 60 cc/min, diluents O
2Flow 90 cc/min.Carry out photoetching corrosion then and form the diffusion mask figure.The diffusion region comprises rectangular block top slab region 221 and top slab region 220, pedestal 210a, 210b top slab region 223, silicon chip frame top square district 222, the side of all porous silicon etching tanks, and the end face of cavity 218, bottom surface and enclosure wall surface all around.The bar shaped diffusion region 221 of rectangular block end face is used for forming the diffusion admittance of cross wire.
Manufacturing step eight diffuses to form the surface conduction layer of high concentration as shown in figure 11.With SiO
2Layer carries out boron diffusion for sheltering, and is that predeposition is carried out in the source at 950 degrees centigrade with the BN sheet, and deposition time 25 minutes produces surface impurity concentration 1 * 10 thus
19/ cubic centimetre.Diffuse to form the electrode 224 that adheres to unsettled strip 215 sides, adhere to the electrode 225 of landing strip 216,217 sides, adhere to the electrode 226,227 of cavity 218 upper and lower surfaces, pedestal and rectangular block end face high-dopant concentration district 228,229,230,231.
Manufacturing step nine as shown in figure 12, in order to realize cross wire, the bar shaped diffusion region 229 of rectangular block end face must be protected with insulating medium, for this reason the low temperature SiO of deposit 1 micron thickness
2Layer, and carry out photoetching corrosion, on end face bar shaped diffusion region, rectangle island 229, form SiO
2 Electric insulation layer 232.
Manufacturing step ten mainly is to connect up and passivation as shown in figure 13.By sputtering at the aluminium lamination of silicon chip end face deposit 1.2 micron thickness, carry out photoetching corrosion, form line 233 and press welding block 234,235,236.Low temperature deposition 1.2 micron thickness phosphorosilicate glass layers carry out photoetching corrosion then, form the pressure welding hole, and double-electrode monocrystal silicon capacitance acceleration sensor chip manufacturing so far finishes.
The present invention proposes a kind of double-electrode monocrystal silicon capacitance acceleration sensor of surveying two vertical direction acceleration, and describes its manufacture method in detail.According to top introduction, be familiar with the technician of integrated circuit and micromachined, can both implement completely this invention.In utilizing the process of this technology, above-mentioned embodiment made amendment and change be not difficult to realize.Do not need to leave the spirit and scope of the present invention, principle that the present invention provides and method can have the application implementation of other purpose.
Claims (12)
1. bipolar electrode silicon single crystal capacitance acceleration sensor is characterized by and comprises:
One silicon epitaxial wafer is made up of silicon monocrystalline substrate and homogeneity silicon single-crystal outer layer;
One inertial mass is the part of said epitaxial loayer, and the bottom has air layer to separate with said substrate;
At least two elastic beams, symmetry holds up said mass, is the part of said epitaxial loayer, and its bottom has air layer that itself and said substrate are separated;
Some unsettled strips, parallel the stretching out of two relative edges from said mass is distributed in said elastic beam both sides, and be parallel with said elastic beam, is the part of said epitaxial loayer, and the bottom has air layer that itself and said substrate are separated;
At least two pedestals that the center is recessed support said elastic beam, and top is the part of said epitaxial loayer, and the bottom has oxide layer that itself and said substrate are carried out the electricity isolation;
Some landing strips, parallel staggered being spaced with said unsettled strip, top is the part of said epitaxial loayer, the bottom has oxide layer that itself and said substrate are carried out the electricity isolation;
Some latticed connecting portions link to each other with said landing strip, and top is the part of said epitaxial loayer, and the bottom has oxide layer that itself and said substrate are carried out the electricity isolation;
One conductive layer covers said mass, elastic beam, and the bottom surface of unsettled strip covers said unsettled strip, landing strip, pedestal, the side of connecting portion, and the end face of said air layer, bottom surface, and circumferential surface;
With said mass bottom surface is float electrode, and the air buffer bottom surface is that fixed electorde constitutes vertical capacitance acceleration sensor;
With said unsettled strip side is float electrode, and landing strip side is that fixed electorde constitutes the lateral capacitance acceleration transducer.
2. want 1 described bipolar electrode silicon single crystal capacitance acceleration sensor according to right, it is characterized by said silicon monocrystalline substrate is the light dope substrate.
3. want 1 described bipolar electrode silicon single crystal capacitance acceleration sensor according to right, it is characterized by said silicon single-crystal outer layer is the light dope epitaxial loayer.
4. want 1 described bipolar electrode silicon single crystal capacitance acceleration sensor according to right, it is characterized by said oxide layer is oxidized porous silicon layer.
5. want 1 described bipolar electrode silicon single crystal capacitance acceleration sensor according to right, it is characterized by the said conductive layer doped single crystal silicon layer of attaching most importance to, its conduction type and said substrate and epitaxial loayer are different.
6. bipolar electrode silicon single crystal capacitance acceleration sensor manufacture method, its sensor comprises a silicon epitaxial wafer; One mass is the part of epitaxial loayer, and the bottom has air layer that itself and silicon substrate are separated; Two elastic beams are supported mass, and the bottom has air layer that itself and silicon substrate are separated; Some unsettled strips are stretched out by the mass both sides, and the bottom has air layer and silicon substrate to separate; Two pedestals, bottom have silicon oxide layer and silicon substrate to isolate, and support elastic beam, and then support mass and unsettled strip; Some landing strips are staggered with unsettled strip; Heavy doping silicon layer covering quality piece, unsettled strip, elastic beam, pedestal, landing strip and the surface of silicon relative with the mass bottom surface; The side of unsettled strip and landing strip constitutes the transverse electric container, and mass bottom surface and surface of silicon constitute vertical capacitor, being characterized as of manufacture method:
A) prepare lightly doped silicon monocrystalline substrate;
B) form the high concentration region identical in the part zone of substrate top with the substrate doping type;
C) form the lightly-doped silicon epitaxial single crystal layer identical in substrate top with the substrate doping type;
D) on epitaxial loayer, form the anodic oxidation diaphragm;
E) in the anodic oxidation diaphragm, form anodizing tank;
F) deepen anodizing tank, make it pass epitaxial loayer and arrive at the high-dopant concentration buried regions;
G) in dense HF solution, carry out anodic oxidation, buried regions optionally is transformed into porous silicon;
H) carry out thermal oxide, the peripheral part of porous silicon layer is transformed into oxidized porous silicon, and form the thermal silicon dioxide layer at silicon chip surface;
I) form the porous silicon etching tank, make and pass epitaxial loayer, and arrive at the oxidized porous silicon and the boundary of oxidized porous silicon not;
J) corrosion of porous silicon in the aqueous slkali of dilution;
K) carry out photoetching corrosion, form silicon dioxide diffusion mask figure at silicon chip surface;
L) carry out boron diffusion, at the silicon chip surface regional area, the cavity that porous silicon corrosion back forms is circumferential surface and formation of porous silicon etching tank side and the different high impurity concentration thin layer of substrate doping type up and down;
M) low temperature deposition silicon dioxide covers silicon chip surface;
N) carry out photoetching corrosion, on the high concentration diffusion layer that is used to be electrically connected, form electric insulation layer;
O) metallize, form electric connection line and press welding block.
7. bipolar electrode silicon single crystal capacitance acceleration sensor manufacture method according to claim 6, it is characterized by said silicon substrate resistivity is the 0.5-20 ohm-cm.
8. bipolar electrode silicon single crystal capacitance acceleration sensor manufacture method according to claim 6, it is characterized by said silicon epitaxy layer resistivity is the 0.5-20 ohm-cm.
9. bipolar electrode silicon single crystal capacitance acceleration sensor manufacture method according to claim 6, it is characterized by said buried regions square resistance is the 5-20 ohms/square.
10. bipolar electrode silicon single crystal capacitance acceleration sensor manufacture method according to claim 6 is characterized by the surface impurity concentration 10 of said high concentration superficial layer
18-10
20/ cubic centimetre.
11. bipolar electrode silicon single crystal capacitance acceleration sensor manufacture method according to claim 6, it is characterized by said anodic oxidation diaphragm is undoped polycrystalline silicon and low stress nitride silicon composite bed.
12. bipolar electrode silicon single crystal capacitance acceleration sensor manufacture method according to claim 6, it is characterized by described anodic oxidation diaphragm is golden chromium composite bed.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN97121626.6A CN1069972C (en) | 1997-11-11 | 1997-11-11 | Double-electrode monocrystal silicon capacitance acceleration sensor and mfg. method therefor |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN97121626.6A CN1069972C (en) | 1997-11-11 | 1997-11-11 | Double-electrode monocrystal silicon capacitance acceleration sensor and mfg. method therefor |
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| CN1217470A CN1217470A (en) | 1999-05-26 |
| CN1069972C true CN1069972C (en) | 2001-08-22 |
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| CN97121626.6A Expired - Fee Related CN1069972C (en) | 1997-11-11 | 1997-11-11 | Double-electrode monocrystal silicon capacitance acceleration sensor and mfg. method therefor |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100373162C (en) * | 2001-10-19 | 2008-03-05 | 基翁尼克公司 | Accelerometer |
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| CN106405151A (en) * | 2016-08-25 | 2017-02-15 | 华东光电集成器件研究所 | Method for preparing low stress Z-axis accelerometer |
| CN108598261B (en) * | 2018-05-10 | 2020-01-07 | 中国科学院物理研究所 | Method for preparing single crystal capacitor by using polycrystalline material |
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1997
- 1997-11-11 CN CN97121626.6A patent/CN1069972C/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100373162C (en) * | 2001-10-19 | 2008-03-05 | 基翁尼克公司 | Accelerometer |
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|---|---|
| CN1217470A (en) | 1999-05-26 |
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