CN100439890C - Capacitor type pressure sensor for single chip single crystal silicon micromechanical processing - Google Patents
Capacitor type pressure sensor for single chip single crystal silicon micromechanical processing Download PDFInfo
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- CN100439890C CN100439890C CNB2005100928800A CN200510092880A CN100439890C CN 100439890 C CN100439890 C CN 100439890C CN B2005100928800 A CNB2005100928800 A CN B2005100928800A CN 200510092880 A CN200510092880 A CN 200510092880A CN 100439890 C CN100439890 C CN 100439890C
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Abstract
The invention relates to a capacitor pressure sensor, which comprises: single crystal silicon substrate; extending single crystal silicon layer at the surface of substrate as flexible electrode of capacitor; extending single crystal frame at the edge surface of single crystal silicon substrate; medium film covering the surface of extending single crystal silicon frame; extending single crystal silicon layer support by the frame as the fixed electrode of capacitor; and a capacity interlayer surrounded by the frame and between two extending single crystal silicon layers. The production of sensor is selectively formed on porous silicon, and extends on the porous silicon, and uses he selective corrosion technique. It can improve the property and reduce the cost.
Description
Technical field
The invention relates to the capacitance pressure transducer, of micromachined, particularly about its structure based on the epitaxial monocrystalline silicon plate condenser, Qi Zhi Zao Only relates to the capacitance pressure transducer, of single monocrystalline silicon piece processing.
Technical background
The scope of pressure sensor application is very extensive, comprises petrochemical industry, hydraulic pressure, food, medicine, machinery, metallurgy, mining, electrical equipment, and Medical Instruments etc., almost spread all over industry-by-industry.
The formation of capacitance pressure transducer, is generally two parallel plate electrodes to be separated by an empty interlayer, and wherein a cube electrode is a stiffness films, and another cube electrode is an elastic film.Externally under the pressure effect, elastic film generation deformation, thus change two distance between electrodes, the electric capacity of capacitor is changed, and the proportional relation of this variation and applied pressure, thereby can calculate pressure by measuring electric capacity.
The elastic film of early stage capacitance pressure transducer, is a metallic film, and its capacitor arrangement adopts the mode of traditional machining to finish.Developed afterwards and ic manufacturing technology and micromachining technology, and released the pressure transducer of micromachined on this basis, comprised piezoresistive pressure sensor and capacitance pressure transducer.The shortcoming of piezoresistive pressure sensor is that temperature characterisitic is poor, and the advantage of capacitance pressure transducer, just in time is a good temp characteristic, thereby capacitance pressure transducer, day by day replaces piezoresistive pressure sensor and is applied to temperature characterisitic is required relatively stricter every field.
The capacitance pressure transducer, of the micromachined of Chu Xianing is two chip architectures the earliest, promptly except that silicon chip, also to use and send the lux glass sheet, elastic electrode is formed by the part wafer thinning, fixed electorde is formed by depositing metal films on glass sheet, pass through anode linkage then, silicon chip and glass sheet are cohered mutually, and between two electrodes, form empty interlayer.Wafer thinning adopts the KOH corrosion, and three kinds of methods are adopted in the control of sheet thickness: the one, and silicon chip is carried out the doping of high concentration boron stop KOH that it is corroded; The 2nd, the control etching time is not corroded to keep certain thickness silicon layer; The 3rd, adopt soi wafer, silicon dioxide buried regions wherein is separated into thick-layer and thin layer two parts with silicon chip, and further corrosion is just stoped by the silicon dioxide buried regions after eroding thick-layer with KOH, thereby thin layer can be remained.There are many problems in the capacitance pressure transducer, of this structure: the one, except sending lux glass, increase material cost with also using the silicon chip; The 2nd, except to also processing the silicon chip processing, increase manufacturing cost to glass sheet; The 3rd, always the width than elasticity silicon fiml is big for the A/F that corrodes for KOH on the silicon chip, is 400 microns as silicon wafer thickness, and then A/F is bigger at least 560 microns than the width of elasticity silicon fiml, thereby causes reducing the utilization factor of silicon chip and the monolithic output capacity of silicon chip; The 4th, the difference of the thermal expansivity of silicon chip and glass sheet causes the thermal stress that is attached on the elasticity silicon fiml, and the characteristic of sensor is constantly degenerated in long-term use.
The Capacitive Absolute Pressure Sensor that single chip architecture later also occurs, the elastic film of such sensor is generally the polysilicon membrane of low-pressure chemical vapor deposition (LPCVD), it deposits the LPCVD silica membrane down simultaneously, form empty interlayer behind the corrode silicon dioxide film, and making polysilicon membrane unsettled and have elasticity, fixed electorde then directly is formed on the silicon chip.The capacitance pressure transducer, of this structure also has the bad solution of some problems: the one, and polysilicon is easy to generate wriggling, influences the long-time stability of device; The 2nd, polysilicon membrane deposits on silicon chip, has the growth thermal stress, influences the sensitivity of device; The 3rd, the thickness of polysilicon membrane is defined in 2 microns usually, and the range ability of device is difficult to expand; The 4th, outside microstructure is exposed to, damage easily, particularly in slicing processes, be unable to undergo water spray and clean.
Said structure is also made into the condenser type differential pressure transducer, and its method is to open numerous apertures in polysilicon membrane, allows fluid therefrom pass, make it not be subjected to fluid pressure action, become fixed electorde, and film is corroded in the subregion of silicon chip, make it bear hydrodynamic pressure, become elastic electrode.Obviously, the capacitance pressure transducer, of this structure does not solve the problem that exists in above-mentioned two kinds of different structure capacitance pressure transducer,s.
Summary of the invention
First purpose of the present invention is to release a kind of capacitance pressure transducer, of micromachined, it consists of single epitaxy single-crystal silicon structure, promptly only with a monocrystalline silicon piece, only single monocrystalline silicon piece is processed, and the elastic electrode of sensor and fixed electorde are all formed by the epitaxial monocrystalline silicon that is grown on the monocrystalline substrate.
Second purpose of the present invention is to release a kind of capacitance pressure transducer, of micromachined, its elastic electrode, fixed electorde, and two empty interlayer between the electrode all form by the multilayer film of homojunction, thereby in electrode film, do not have any thermal stress that causes by the difference of thermal expansion coefficients between the heterojunction material.
The 3rd purpose of the present invention is to release a kind of capacitance pressure transducer, of micromachined, the formation of its elastic electrode film and KOH corrosion are irrelevant, the KOH corrosion is just in order to form the passage that fluid arrives at elastic electrode, thereby the corrosion opening can be dwindled as far as possible, to reduce the silicon area that it takies as far as possible, prevent that also the physical strength of silicon chip from reducing too much simultaneously.
The 4th purpose of the present invention is to release a kind of capacitance pressure transducer, of micromachined, its elastic electrode, fixed electorde, and the final technological level decision of all making of the vertical and horizontal yardstick of empty interlayer by semiconductor, promptly by diffuser extension, the technological level decision of photoetching corrosion etc., well-known, semiconductor fabrication process is very ripe, control accuracy is very high, so elastic electrode, fixed electorde, and the yardstick in cavity can both accurately limit.
The 5th purpose of the present invention is to release a kind of capacitance pressure transducer, of micromachined; make the elasticity silicon fiml of its most fragile be in protected state; do not allow it directly contact with external environment condition; the transmission of fluid is only by some apertures; in order to avoid making; section, and damaged in the use.
To achieve these goals and other purpose, the present invention proposes a kind of capacitance pressure transducer, of micromachined, and its composition comprises: monocrystalline substrate; Be in the monocrystalline substrate surface, play the epitaxy single-crystal silicon layer of capacitor elastic electrode effect; Be in the epitaxy single-crystal silicon frame of elasticity epitaxy single-crystal silicon layer edge surface; Cover the dielectric film on epitaxial monocrystalline silicon framework surface; Be in elasticity epitaxy single-crystal silicon layer top, center on, play the empty interlayer of condenser dielectric membrane action by the epitaxy single-crystal silicon frame; Support by the epitaxy single-crystal silicon frame, have some tiny through holes, play the epitaxy single-crystal silicon layer of capacitor fixed electorde effect; Be in elasticity epitaxy single-crystal silicon layer bottom, shape and elasticity epitaxy single-crystal silicon layer cavity similar; And run through the cavity bottom silicon layer, connect the through hole of cavity inside and monocrystalline silicon silicon substrate external environment condition.
The metering system of differential capacitance is generally adopted in the capacitance measurement of capacitance pressure transducer,, to eliminate temperature effect and other various external disturbance.For this reason, on monocrystalline substrate, form above-mentioned being subjected to and also will form the reference capacitor that not influenced by external pressure outside the pressure capacitor that external pressure influences.Reference capacitor and pressure capacitor difference are that its two cube electrode all is a fixed electorde, and the elasticity monocrystalline silicon thin film of deformation promptly need not take place with the external pressure effect, the substitute is the monocrystalline substrate that need not carry out micromachined.In addition other structural detail, reference capacitor all is identical with the pressure capacitor, when guaranteeing that externally pressure act as zero, the capacitance of two capacitors is identical.
Make the capacitance pressure transducer, of micromachined and at first use selectivity formation porous silicon technology.Porous silicon is that monocrystalline silicon carries out the special monocrystal silicon structure that anodic oxidation produced in hydrofluoric acid solution, though be corroded into cellularly apparently, the silicon atom in the solid network still keeps original periodic arrangement.Porous silicon forms the anode voltage that need add and raises with the increase of monocrystalline silicon resistivity, therefore can make the silicon layer of low-resistivity be transformed into porous silicon, and the silicon layer of high resistivity still keep original nonporous monocrystalline silicon structure by control voltage.
The capacitance pressure transducer, manufacturing also will be used and be carried out epitaxial growth on the porous silicon layer surface and form epitaxy single-crystal silicon layer technology.As the porous silicon of monocrystalline silicon, it is brilliant to become son, and forms the epitaxy single-crystal silicon layer thereon, and just epitaxial growth is easy to be subjected to the interference of foreign matter atom, the fault of construction of exert an influence epitaxial loayer crystal mass and configuration of surface.For this reason, before carrying out epitaxial growth, need carry out high temperature hydrogen treatment, the silicon atom of superficial layer is rearranged the porous silicon layer surface, the reduced bore, closed orifices forms fine and close porous surface silicon thin layer.Carrying out epitaxial growth through on the porous silicon of densification like this, bright seemingly mirror of the epitaxy single-crystal silicon surface that is obtained and the epitaxy single-crystal silicon layer of growing on normal monocrystalline substrate almost do not have any difference.In order to prevent that the porous silicon layer top layer from epitaxially grown pyroprocess avalanche taking place with the porous silicon of lower area, also need before the epitaxial growth to handle with carrying out low thermal oxidation, so that form the silicon oxide film of thick about 20 dusts in the micropore inner wall surface, experiment showed, that this silicon oxide film can stop silicon atom heat to move completely and arranges again.
Selective corrosion low thermal oxidation porous silicon also is a gordian technique of making capacitance pressure transducer.The porous silicon of low thermal oxidation is almost the same with silicon dioxide, can keep out the sulfur hexafluoride plasma etching, and the sulfur hexafluoride plasma is very effective to the corrosion of monocrystalline silicon, particularly highdensity sulfur hexafluoride plasma up to 6 microns/minute, and reaches 0.3 micron/minute to the corrosion rate of the porous silicon of 400 degrees centigrade of thermal oxides is low to the corrosion rate of monocrystalline silicon.What form distinct contrast therewith is to use etchant solution 49%HF: H
2O
2Carry out wet etching at=1: 5, and up to 2.4 microns/minute, and very little to the corrosion of monocrystalline silicon, corrosion is selected than up to 10 to the corrosion rate of the porous silicon of 400 degrees centigrade of thermal oxides for it
-5Therefore, can be used for the porous silicon of selective corrosion mild oxidation.
Description of drawings
Figure 1A and Figure 1B are respectively the front and the cross sectional representation of the capacitance pressure transducer, of the micromachined that the present invention proposes.
Cross sectional representation when the capacitance pressure transducer, of the micromachined that Fig. 2 proposes for the present invention is in manufacturing step 1 the figure shows the formation porous silicon layer monocrystalline substrate top layer in.
Cross sectional representation when the capacitance pressure transducer, of the micromachined that Fig. 3 proposes for the present invention is in manufacturing step 2 the figure shows the monocrystalline substrate surface, comprises that the porous silicon layer surface forms the epitaxy single-crystal silicon layer of two-layer doped structure.
Cross sectional representation when the capacitance pressure transducer, of the micromachined that Fig. 4 proposes for the present invention is in manufacturing step 3, the doped layer that the figure shows the top low-resistivity of epitaxy single-crystal silicon layer is transformed into porous silicon layer.
Cross sectional representation when the capacitance pressure transducer, of the micromachined that Fig. 5 proposes for the present invention is in manufacturing step 4 the figure shows in the extension monocrystalline surface, comprises that the porous silicon layer surface forms the epitaxy single-crystal silicon layer.
Cross sectional representation when the capacitance pressure transducer, of the micromachined that Fig. 6 proposes for the present invention is in manufacturing step 5 the figure shows at the back side of monocrystalline substrate wet etching and forms the deep trouth relative with the front porous silicon layer.
Cross sectional representation when the capacitance pressure transducer, of the micromachined that Fig. 7 proposes for the present invention is in manufacturing step 6, the figure shows epitaxy single-crystal silicon layer ionic medium corrosion formation pore array in the front of monocrystalline substrate, and further deepen back side deep trouth, make it arrive at the porous silicon layer lower interface.
Cross sectional representation when the capacitance pressure transducer, of the micromachined that Fig. 8 proposes for the present invention is in manufacturing step 7, the figure shows the selective corrosion porous silicon layer, make two porous silicon layers become empty interlayer and cavity respectively, form unsettled perforation epitaxy single-crystal silicon layer on the interlayer of cavity, as the capacitor fixed electorde, the cavity interlayer forms unsettled epitaxy single-crystal silicon layer down, as the capacitor elastic electrode, thereby forms the differential capacitance type pressure transducer.
Cross sectional representation when the capacitance pressure transducer, of the micromachined that Fig. 9 proposes for the present invention is in manufacturing step 8, the figure shows the through hole of shut capacitor fixed electorde, intercept the communicative channel of empty interlayer and monocrystalline substrate outside, in order to form the absolute pressure capacitance pressure transducer.
Figure 10 is the signal processing circuit calcspar of the capacitance pressure transducer, of the micromachined of the present invention's proposition, and this circuit can carry out digital calibration to sensor, and numeral output or simulation output are provided.
Specific implementation method
1A and 1B with reference to the accompanying drawings, this two figure are respectively the differential capacitance type pressure transducer front and the cross sectional representation of the micromachined that the present invention proposes.Front schematic view 1A expresses, and this pressure transducer comprises presser sensor plate condenser 101 and export press welding block 102 that press welding block 104 is gone in reference plate capacitor 103 and output thereof.Capacitor 101 and 103 is arranged side by side, is wide 100 to 1000 microns rectangle, and its top electrodes is in monocrystalline silicon region, on every side by polysilicon strip 107 around.Polysilicon strip 107 extends from the edge, lateral of capacitor, and is extended to the press welding block base.Center line along polysilicon strip 107 has air channels 108, with two capacitors and separately press welding block be spaced from each other, simultaneously with two capacitors and press welding block and other monocrystalline silicon region 106 are separated separately.The bottom electrode of two capacitors links to each other with monocrystalline silicon region 106, and the press welding block 105 on the monocrystalline silicon region 106 is that press welding block is gone in the public output of two capacitors in fact.
Cross sectional representation 1B expresses the pressure transducer manufactured materials will use monocrystalline substrate 109, the bottom epitaxy single- crystal silicon layer 110 and 111 of height different resistivity, electric insulating medium film 117, and top epitaxy single-crystal silicon layer 112.Monocrystalline substrate 109 is in P-type doped monocrystalline silicon sheet in 0.1 to the 0.001 ohmcm scope for resistivity.Epitaxy single- crystal silicon layer 110 and 111 is respectively resistivity and is in P-type in 1 to the 20 ohmcm scope or N-type doped single crystal silicon layer and is in P-type or N-type doped single crystal silicon layer in 0.1 to the 0.001 ohmcm scope.Electric insulating medium film 117 is the composite dielectric film that the silicon nitride of 500 to 1000 microns silicon dioxide and 2000 to 3000 microns is formed.
The presser sensor capacitor is formed and is comprised: have 10 to 20 microns tiny through holes of straight Trail, thick 10 to 20 microns, wide 100 to 1000 microns top fixed electorde 114, empty interlayer 115 between thick 2 to 4 microns electrode, thick 2 to 4 microns supporting frame 116, thick 1 to 8 micron, wide 100 to 1000 microns bottom elastic electrode 113 is in the elastic electrode bottom, thick 10 to 20 microns cavity 118, and 50 to 200 microns of straight Trail, the through hole 119 that directes reach the monocrystalline substrate back side.Reference capacitor is formed and is comprised: have 10 to 20 microns tiny through holes of straight Trail, thick 10 to 20 microns, wide 100 to 1000 microns top fixed electorde 121, empty interlayer 122 between thick 2 to 4 microns electrode, thick 2 to 4 microns supporting frame 123, and thick 1 to 8 micron, wide 100 to 1000 microns bottom fixed electorde 120.Above-mentioned top fixed electorde 114, supporting frame 116, bottom elastic electrode 113, and bottom fixed electorde 120 is all formed by the epitaxy single-crystal silicon layer.The epitaxy single-crystal silicon layer that forms top fixed electorde 114 and supporting frame 116 is that resistivity is in P-type or the N-type monocrystalline silicon layer in 0.1 to the 0.001 ohmcm scope.The epitaxy single-crystal silicon layer that forms bottom elastic electrode 113 and bottom fixed electorde 120 is that resistivity is in the N-type doped single crystal silicon layer in 1 to the 20 ohmcm scope.
Presser sensor plate condenser when impressed pressure is zero and the electric capacity of reference plate capacitor can be expressed as C
0=ε A/d, wherein ε is the specific inductive capacity of empty interlayer between electrode, and A is an electrode area, and d is an interelectrode distance.If the presser sensor plate condenser is added the differential pressure effect, interelectrode distance change value can be expressed as x=0.0151 Δ Pa
4(1-v
2)/E (2h)
3, Δ P is the pressure reduction that acts on the elastic electrode two sides in the formula, and a is the elastic electrode width, and h is an elastic electrode thickness, and v is a paper tinsel pine ratio, E is a young modulus.And the expression formula of the electric capacity of the presser sensor plate condenser of this moment changes over C=C
0/ (1-x/d).The electric capacity difference of responsive plate condenser of gaging pressure and reference plate capacitor can be eliminated the environmental factor that comprises temperature and the influence of various interference, makes measured value only make monotone variation with the external action differential pressure.
By Figure 1A and Figure 1B as seen, as long as the tiny through hole of closure tip fixed electorde, the cavity interlayer just is in the state of isolating with external environment condition, impressed pressure only acts on the surface that elastic electrode leads to external environment condition, and the pressure in the empty interlayer keeps vacuum or a certain fixation pressure, the pressure that measure this moment is absolute pressure, thereby becomes absolute pressure transducer.
Cross sectional representation when Fig. 2 to Fig. 9 represents that the differential capacitance type pressure transducer of the micromachined that the present invention proposes is in each manufacturing step.Fig. 2 is the cross sectional representation when being in manufacturing step 1, and the expression monocrystalline substrate forms porous silicon layer in the top layer.With reference to Fig. 2, prepare monocrystalline substrate 201, the doping type of substrate does not have special requirement, but preferably the P-type mixes, and resistivity is in 0.1 to the 0.001 ohmcm scope.By the silica membrane of thermal oxide, then by low-pressure chemical vapor deposition (LPCVD), then form the silicon nitride film of thick 2000 to 3000 dusts, thereby obtain composite dielectric film 202 at thick 500 to 1000 dusts of monocrystalline substrate surface formation.Anodic oxidation solution in silicon dioxide and silicon nitride film 202, forms wide 100 to 1000 microns rectangle anodic oxidation window by photoetching corrosion, so that can contact the monocrystalline substrate surface.Anodic oxidation solution is 49%HF: C
2H
5OH (1 to 2 to 1) when anodic oxidation begins, allows anode current from 10mA/cm
2Slowly be increased to 60 to 70mA/cm
2, so that form 1 micron thickness, porosity is in the porous silicon layer between 10 to 20%, forms 9 to 19 micron thickness along with current density increases then, porosity is in the porous silicon layer 203 between 60 to 70%.In fact, current density is started from scratch and is increased to 70mA/cm
2Always will experience the regular hour, always porosity is lower for the therefore initial porous silicon that generates.Control current density is advanced the speed intentionally, just in order to make the lower top layer porous silicon of porosity thicker as far as possible.
Fig. 3 is the cross sectional representation when being in manufacturing step 2, is illustrated in the monocrystalline substrate surface that is formed with porous silicon layer and forms the epitaxy single-crystal silicon layer.Before carrying out epitaxial growth, must fall remaining silica and silicon nitride film with the HF solution corrosion, and with acetone and have isopropyl acetone (IPA) organic solvent of etc.ing that the monocrystalline substrate surface is cleaned, the solid particle of removing surface adhesion.Annealing in process 1 hour in 400 degrees centigrade oxygen then is to form the silica membrane of thick about 20 dusts in porous silicon micropore inner wall surface.Silica membrane has very strong interception to the elevated temperature heat migration of silicon atom, therefore can stop in high-temperature process subsequently because the micropore avalanche that silicon atom is arranged again and caused.Silicon chip is used 30 seconds of HF solution corrosion of dilution, and use deionized water rinsing.Subsequently silicon chip is advanced epitaxial furnace, carry out the preceding high temperature hydrogen treatment of epitaxial growth, treatment temperature is between 1050 to 1100 degrees centigrade, and the processing time is 7 to 30 minutes.In the high temperature hydrogen treatment process, the surface energy on porous silicon top layer is greatly reduced, silicon atom in case depth 30 to the 40 angstroms depth scopes is able to again nucleation and growth, result in that micro-pore diameter dwindles or the aperture sealing, make the porous silicon layer surface become fine and close bright, it is brilliant to become quality epitaxial growth preferably.Then under uniform temp, in epitaxial furnace, carry trichlorosilane or the dichloro hydrogen silicon that is used as the grown silicon source, to form the epitaxy single-crystal silicon epitaxy layer.
Epitaxial growth is carried out in two steps, and the first step is not mixed, and forms thick 1 to 8 micron not doped epitaxial layer 204, and the conduction type of epitaxial loayer can be the P type, also can be the N type, N type preferably, and resistivity is in 1 to 20 ohmcm scope; Second step, mix, form the doped epitaxial layer 205 of thick 2 to 4 micron thickness.The doping type of epitaxial loayer can be the P type, also can be the N type, N type preferably, and resistivity is in 0.1 to 0.001 ohmcm scope.Borine is a P type adulterant, and phosphine is a N type adulterant, carry by nitrogen, with send in the stove after silicon source gas mixes.
Cross sectional representation when Fig. 4 is in manufacturing step 3 for pressure transducer, the doped epitaxial monocrystalline silicon layer 205 that the figure shows low-resistivity is transformed into porous silicon layer.For this reason, by LPCVD, form the silicon dioxide of thick 500 to 1000 dusts and the silicon nitride composite dielectric film 206 of thick 2000 to 3000 dusts in the extension monocrystalline surface successively.In composite dielectric film 206, form wide 100 to 1000 microns rectangle anodic oxidation window by photoetching corrosion, to expose epitaxy single-crystal silicon layer 205 surfaces.Adopt condition and the step identical with the front anodic oxidation, form porous silicon layer 207, just the gross thickness of porous silicon layer is 2 to 4 microns, and the superficial layer of low porosity also can reduce to 0.5 micron.
Cross sectional representation when Fig. 5 is in manufacturing step 4 for pressure transducer the figure shows on extension monocrystalline silicon layer 205 surfaces, comprises that porous silicon layer 207 surfaces form the epitaxy single-crystal silicon layer.
The extension condition and the similar manufacturing step of mode of operation and front that adopt are roughly similar, so something in common no longer repeats, and just stress difference.
Before carrying out epitaxial growth, photoetching corrosion be must carry out one time, part remaining silica and silicon nitride film fallen with the HF solution corrosion.Therefore the epitaxy single-crystal silicon growth is actually and carries out on the figure of composite dielectric film, and just the area of composite dielectric film is a considerably less part with respect to the total area of silicon chip, what video display whole epitaxial growth is not had.But length is not monocrystalline silicon on composite dielectric film, but polysilicon, as what express among the figure,
What form on porous silicon layer 207 and exposed epitaxy single-crystal silicon layer 205 surfaces is the epitaxy single-crystal silicon layer 208 of 10 to 20 microns of thickness, and what form on composite dielectric film 206 surfaces also is the extension polysilicon layer 209 of 10 to 20 microns of thickness.
Be noted that the polysilicon layer that forms on composite dielectric film becomes upwards shrink tubaeform, its reason is that transversal epitaxial growth works.If the width of composite dielectric film is very little, and epitaxial loayer is very thick, might be covered by the epitaxy single-crystal silicon layer on the surface of extension polysilicon layer.In addition, in general, the polysilicon generating rate on the composite dielectric film is lower than the monocrystalline silicon generating rate on the porous silicon, so the extension polysilicon layer can seem thinner than epitaxy single-crystal silicon layer.
Cross sectional representation when Fig. 6 is in manufacturing step 5 for pressure transducer the figure shows at the back side of monocrystalline substrate and carries out wet etching, forms and the relative deep trouth in porous silicon layer position, front.For this reason, earlier at monocrystalline substrate 201 back sides,, form the composite dielectric film 210 of the silicon nitride of the silicon dioxide of thick 500 to 1000 dusts and thick 2000 to 3000 dusts by LPCVD.In composite dielectric film, form wide 500 to 600 microns wide rectangle corrosion windows by photoetching corrosion again.Etchant solution is a 80%KOH solution, and corrosion temperature is 80 degrees centigrade, and etchant solution is fully stirred, and obtaining corrosion rate is 5 to 6 microns/minute.In order to obtain accurate corrosion rate, can carry out the corrosion of short time earlier, carry out corrosion rate then and measure.The corrosion rate that records according to the scene is calculated etching time, 10 to 20 microns apart from the positive porous silicon layer bottom surface that forms of monocrystalline substrate of the bottom surfaces that makes the pyramidal pits 211 that corrosion forms.
Cross sectional representation when Fig. 7 is in manufacturing step 6 for pressure transducer, the figure shows in monocrystalline substrate front epitaxy single-crystal silicon layer 208, form tiny through hole by plasma etching, and further deepen the deep trouth that the positive back side of monocrystalline substrate forms, make it arrive at the bottom surface of porous silicon layer 203.For this reason, form thick 3 to 6 microns photoresist figure on epitaxy single-crystal silicon layer 208 surfaces in monocrystalline substrate front earlier, make in the zone of its porous silicon layer 207 below aiming at, form directly through 5 to 6 microns, 20 to 40 microns corrosion micropores at interval distribute, and below aiming at, in the zone of polysilicon strip, form wide 5 to 6 microns corrosion microflutes.Then carry out plasma etching, etchant gas SF
6, passivation gas CF
4, by repeatedly alternating corrosion bottom surface and the operation of protection side, form and pass epitaxy single-crystal silicon layer 208, direct reach the through hole 212 on following porous silicon layer 207 surfaces and the groove 213 that directes reach following composite dielectric film 206 surfaces.With the silicon chip upset,, pyramidal pits 211 bottom surfaces at the back side are advanced to the bottom surface of porous silicon layer 203 then by the corrosion of plasma deep trouth.The porous silicon of low thermal oxidation is almost the same with silicon dioxide, can keep out the plasma etching of sulfur hexafluoride, and the sulfur hexafluoride plasma is very effective to the corrosion of monocrystalline silicon, particularly highdensity sulfur hexafluoride plasma to the corrosion rate of monocrystalline silicon up to 6 microns/minute, and reach 0.3 micron/minute to the corrosion rate of the porous silicon of 400 degrees centigrade of thermal oxides is low, as seen the corrosion of the porous silicon of monocrystalline silicon and light oxidation is selected than being very high.
Cross sectional representation when Fig. 8 is in manufacturing step 7 for pressure transducer, the figure shows the selective corrosion porous silicon layer, make porous silicon layer become empty interlayer and cavity, form unsettled perforation epitaxy single-crystal silicon layer on the interlayer of cavity, as the capacitor fixed electorde, the cavity interlayer forms unsettled epitaxy single-crystal silicon layer down and on the cavity, as the capacitor elastic electrode, thereby forms the differential capacitance type pressure transducer.Use etchant solution 49%HF: H
2O
2=1: 5 corrosion of porous silicon layers, its corrosion rate to the porous silicon of 400 degrees centigrade of thermal oxides is 2.4 microns/minute, and monocrystalline silicon is corroded hardly, the corrosion selectivity is up to 10
-5, also can be with the KOH of dilution or NaOH solution as the mordant of porous silicon.Here need to prove, consider, require the porosity of porous silicon high as far as possible, but consider, wish that the porosity of porous silicon is low as far as possible from epitaxial growth from the facility corrosion.Therefore the porous silicon layer that forms previously all adopts double-layer structure, and the top layer is a low porosity, is beneficial to epitaxial growth, obtain the reasonable epitaxial loayer of monocrystalline quality, bottom is a high porosity, and the micropore lateral magnification reticulates, be beneficial to etchant solution and therefrom flow, accelerate corrosion process.
Corrosion forms thick 1 to 8 micron elasticity epitaxy single-crystal silicon electrode 216, thick 10 to 20 microns fixing epitaxy single-crystal silicon electrodes 217, and thick 2 to 4 microns empty interlayer 214, be in elasticity epitaxy single-crystal silicon electrode 216 and the fixing epitaxial monocrystalline silicon supporting frame 218 between the epitaxy single-crystal silicon electrode 217, be in elasticity epitaxy single-crystal silicon electrode 216 bottoms, thick 10 to 20 microns cavity 215, and the through hole 219 that leads to monocrystalline substrate 201 outsides, and form compression capacitor by these elements.Meanwhile, form thick fixedly epitaxy single-crystal silicon electrode 222, thick 10 to 20 microns fixing epitaxy single-crystal silicon electrodes 221, and thick 2 to 4 microns empty interlayer 220, be in fixedly epitaxy single-crystal silicon electrode 222 and fixedly the epitaxial monocrystalline silicon supporting frame 223 between the epitaxy single-crystal silicon electrode 221, and form reference capacitor by these elements.
Cross sectional representation when Fig. 9 is in manufacturing step 7 for pressure transducer, the figure shows the through hole of shut capacitor fixed electorde, intercept empty interlayer 214 and 220 and the communicative channel of monocrystalline substrate 201 outsides, in order to form the absolute pressure capacitance pressure transducer.For this reason, form thick 3 to 4 microns hydrogeneous silicon oxide layer 224, with sealing through hole 212 and 213 by plasma reinforced chemical vapour deposition (PECVD).Also the metallic aluminium of available electron beam evaporation same thickness replaces and contains the filling material of silicon hydroxide as through hole 212 and 213.Difference between the two is the vacuum tightness difference of the empty interlayer that can cause, and the former can only cause low vacuum tightness, and the latter but can cause condition of high vacuum degree.
Figure 10 is the signal processing circuit calcspar of the capacitance pressure transducer, of the micromachined of the present invention's proposition.As seen from the figure, the compression capacitor 302 of the capacitance pressure transducer, of micromachined and reference capacitor 303 are respectively by time clock 301 modulation, the positive-negative input end of importing charge amplifier 304 that distributes then carries out the integration amplification, and the output voltage after the amplification should keep the external pressure proportional relation suffered with pressure transducer.Sigma-Delta analog/digital converter 305 converts the output voltage of charge amplifier to digital signal, is handled by digital processing unit 306 then, and to realize gain adjustment, skew is eliminated, temperature compensation, and function such as output linearization.Next by Sigma-Delta D/A converter 307 conversion of signals after the digital processing is become simulating signal, shown in Figure 30 8, the simulation output of this moment and the simulation of sensor are output into linear relationship.Also can directly with numeral output, judge the suffered external pressure of pressure transducer without the Sigma-Delta steering D/A conversion according to the density of output pulse.
Calcspar also comprises clock signal generator 309 and EEPROM (EEPROM) 310, the former provides digital processing unit working pulse and sensor modulating pulse, and the latter provides the digital processing unit calibration parameter and charge amplifier range conversion parameter is provided.EEPROM 310 is connected with computing machine with external calibration by standard SPI interface, various calibration parameters are collected the capacitance pressure transducer, test data by computing machine and it are analyzed the back determine, and then store and implement calibration by EEPROM 310.
The feature structure and the manufacture method of the capacitance pressure transducer, spare of micromachined have been described in detail above; those skilled in the art can carry out the part on this basis and adjust and revise; be not difficult to repeat out result of the present invention, but this can't exceed the protection domain of claim of the present invention.
Claims (10)
1. the capacitance pressure transducer, of a micromachined, its architectural feature comprises:
Monocrystalline substrate;
Be in the monocrystalline substrate surface, thick 1 to 8 micron, wide 100 to 1000 microns, play the rectangle epitaxy single-crystal silicon layer of capacitor elastic electrode effect;
Be in epitaxy single-crystal silicon layer edge surface, thick 2 to 4 microns epitaxy single-crystal silicon frame;
Cover the dielectric film on epitaxial monocrystalline silicon framework surface;
Support by the epitaxy single-crystal silicon frame, thick 10 to 20 microns, have 3 to 6 microns through holes of some diameters, play the epitaxy single-crystal silicon layer of capacitor fixed electorde effect;
Be between elastic electrode and the fixed electorde the empty interlayer that is centered on by the epitaxy single-crystal silicon frame;
Be in monocrystalline substrate inside, elastic electrode epitaxy single-crystal silicon layer bottom, thick 10 to 20 microns, wide 100 to 1000 microns, shape and the rectangle epitaxy single-crystal silicon layer cavity similar that plays the effect of capacitor elastic electrode; And
Run through the cavity bottom silicon layer downwards, connect the through hole of cavity inside and monocrystalline substrate external environment condition.
2. according to the capacitance pressure transducer, of the described micromachined of claim 1, its architectural feature is that described monocrystalline substrate is that resistivity is in the P-type doped monocrystalline silicon sheet in 0.1 to the 0.001 ohmcm scope.
3. according to the capacitance pressure transducer, of the described micromachined of claim 1, its architectural feature is that the described epitaxy single-crystal silicon layer that plays the effect of capacitor elastic electrode is that resistivity is in 1 to the 20 ohmcm scope, and doping type is the epitaxy single-crystal silicon layer of N-type or P-type.
4. according to the capacitance pressure transducer, of the described micromachined of claim 1, its architectural feature is that described epitaxy single-crystal silicon frame is that resistivity is in 0.1 to the 0.001 ohmcm scope, and doping type is the epitaxy single-crystal silicon layer of P-type or N-type.
5. according to the capacitance pressure transducer, of the described micromachined of claim 1, its architectural feature is that described dielectric film is the composite dielectric film that the silicon nitride of the silicon dioxide of thickness 500 to 1000 dusts and thick 2000 to 3000 dusts is formed.
6. according to the capacitance pressure transducer, of the described micromachined of claim 1, its architectural feature is that the described epitaxy single-crystal silicon layer that plays the effect of capacitor fixed electorde is that resistivity is in P-type or the N-type monocrystalline silicon layer in 0.1 to the 0.001 ohmcm scope.
7. method of making the capacitance pressure transducer, of the described micromachined of claim 1 is characterized in that manufacturing step comprises:
Prepare monocrystalline substrate, the P-type mixes, and resistivity is in 0.1 to the 0.001 ohmcm scope;
By thermal oxide, low-pressure chemical vapor deposition (LPCVD), and photoetching corrosion, form the composite dielectric film that the silicon nitride of the silicon dioxide of thick 500 to 1000 dusts and thick 2000 to 3000 dusts is formed on P-type monocrystalline substrate surface, and open wide 100 to 1000 microns square type window therein, to expose P-type monocrystalline substrate surface;
By anodic oxidation, in wide 100 to the 1000 microns square type window of surface of silicon, form dark 10 to 20 microns porous silicon layer, wherein 1 micron thickness porous silicon layer porosity is between 10 to 20%, and 9 to 19 micron thickness porous silicon layer porositys are between 60 to 70%;
Carry out epitaxial growth,, comprise the porous silicon layer surface in surface of silicon, form thick 1 to 8 micron earlier, the N-type of resistivity 1 to 20 ohmcm or P-type epitaxy single-crystal silicon layer form thick 2 to 4 microns again, the P-type epitaxy single-crystal silicon layer of resistivity 0.1 to 0.001 ohmcm;
By low-pressure chemical vapor deposition (LPCVD) and photoetching corrosion, form the composite dielectric film that the silicon nitride of the silicon dioxide of thick 500 to 1000 dusts and thick 2000 to 3000 dusts is formed in P-type epitaxy single-crystal silicon surface, and open wide 100 to 1000 microns square type window therein, to expose P-type epitaxy single-crystal silicon layer;
By anodic oxidation, the P-type epitaxy single-crystal silicon layer that exposes in the window is transformed into thick 2 to 4 microns porous silicon layer, and its thick 0.5 micron top layer porosity is in 10 to 20% scopes, the top layer is in 60 to 70% scopes with the porosity of lower area;
Carry out epitaxial growth, form thick 10 to 20 microns on thick 2 to 4 microns porous silicon layer surface, the P-type of resistivity 0.1 to 0.001 ohmcm or N-type epitaxy single-crystal silicon layer, composite dielectric film on extension monocrystalline silicon layer surface forms thick 10 to 20 microns, and resistivity 0.1 is to 0.001 ohm li P-type or N-type extension polysilicon layer;
By corrosion, in the monocrystalline substrate of dark 10 to 20 micron porous silicon layer bottom, form and pass through the through hole of monocrystalline substrate downwards;
By the corrosion of plasma deep trouth, in dark 10 to 20 microns epitaxy single-crystal silicon layer, form the through hole of 5 to 6 microns of some diameters; And
By selective corrosion, remove dark 10 to 20 microns porous silicon layer and thick 2 to 4 microns porous silicon layer, form thick 1 to 8 micron elasticity epitaxy single-crystal silicon electrode, thick 10 to 20 microns fixedly epitaxy single-crystal silicon electrode, thick 2 to 4 microns empty interlayer, and thick 10 to 20 microns cavity, finally finish the manufacturing of differential pressure capacitance pressure transducer.
8. according to the method for the capacitance pressure transducer, of the described manufacturing micromachined of claim 7, it is characterized in that the formation described in the manufacturing step passes through the through hole of monocrystalline substrate downwards and carry out in two steps, form pyramidal pits with the KOH solution corrosion earlier, use SF again
6Plasma etching makes pit bottom extend to porous silicon layer, and stops at the porous silicon layer surface automatically.
9. according to the method for the capacitance pressure transducer, of the described manufacturing micromachined of claim 7, it is characterized in that the formation described in the manufacturing step passes through the through hole SF of monocrystalline substrate downwards
6Plasma etching stops after corrosion proceeds to porous silicon layer automatically.
10. according to the method for the capacitance pressure transducer, of the described manufacturing micromachined of claim 7, it is characterized in that manufacturing step also is included in out the epitaxy single-crystal silicon surface of some through holes, by plasma reinforced chemical vapour deposition (PECVD), form thick 3 to 4 microns silicon dioxide layer, with the sealing through hole, constitute the absolute pressure capacitance pressure transducer.
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| DE102009051611A1 (en) * | 2009-11-02 | 2011-05-05 | Vega Grieshaber Kg | cell |
| CN102052989B (en) * | 2010-11-18 | 2012-02-29 | 华中科技大学 | Capacitance pressure sensor with high Q value and large relative variable quantity |
| CN102815661A (en) * | 2011-06-07 | 2012-12-12 | 无锡华润华晶微电子有限公司 | Preparation method of silicon film |
| CN102620878B (en) * | 2012-03-15 | 2014-03-12 | 西安交通大学 | Capacitive micromachining ultrasonic sensor and preparation and application methods thereof |
| CN103048043B (en) * | 2012-12-18 | 2016-05-25 | 苏州锦富新材料股份有限公司 | Based on light or the gas detector of inorganic semiconductor monocrystalline network structure |
| CN104843633A (en) * | 2014-02-14 | 2015-08-19 | 中芯国际集成电路制造(上海)有限公司 | Silicon anisotropic etching method |
| CN104914275A (en) * | 2014-03-10 | 2015-09-16 | 北京大学 | Novel MEMS capacitive accelerometer temperature compensating circuit |
| CN104677528B (en) * | 2015-03-13 | 2017-02-01 | 中国电子科技集团公司第二十四研究所 | Capacitive pressure sensor and preparation method thereof |
| CN112284608B (en) * | 2020-09-15 | 2022-08-02 | 南京高华科技股份有限公司 | Capacitive micro-mechanical air pressure sensor and preparation method thereof |
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| US6051853A (en) * | 1996-10-03 | 2000-04-18 | Hitachi, Ltd. | Semiconductor pressure sensor including reference capacitor on the same substrate |
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| EP0195985A2 (en) * | 1985-03-27 | 1986-10-01 | Siemens Aktiengesellschaft | Capacitive pressure sensor |
| US6051853A (en) * | 1996-10-03 | 2000-04-18 | Hitachi, Ltd. | Semiconductor pressure sensor including reference capacitor on the same substrate |
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