A kind of capacitance pressure transducer, and preparation method thereof
Technical field
The invention belongs to art of pressure sensors, relate to a kind of capacitance pressure transducer, and preparation method thereof, particularly the capacitance pressure transducer, that changes of a kind of bulky capacitor.
Background technology
Pressure transducer because of pressure, the sensor that the Parameters variation such as resistance, electric capacity, electric current, light carry out test pressure change occurs by detecting, pressure transducer is the same with acceleration transducer, be all the sensor had a large capacity and a wide range, annual demand reaches tens.
Pressure transducer is of a great variety, mainly contain silicon piezoresistance type pressure sensor, resonance type pressure sensor, capacitance pressure transducer, etc., silicon piezoresistance type pressure sensor carrys out detected pressures by detecting sensistor resistance with change in pressure, this pressure transducer is because sensistor is semiconductor resistor, there is resistance to vary with temperature, also have and adopt PN junction isolation, there is the problems such as PN junction electric leakage, the detection signal pickup that its treatment circuit should complete resistance signal processes with amplification, carry out the temperature compensation of sensistor again, this just proposes very high requirement to treatment circuit, therefore, silicon piezoresistance type pressure sensor is limited to cost, be mainly used in accuracy requirement not high, the field that environmental requirement is not high.Resonance type pressure sensor utilizes the pressure-dependent feature of the natural resonance frequency of sensor to carry out detected pressures, which eliminate sensor and cause because external environment changes (as: temperature, magnetic etc.) impact that pressure detection precision is brought, it is the first-selected sensor that high-precision pressure detects, but difficulty of processing is comparatively large, also only has three companies to succeed in developing at present in the world.Capacitance pressure transducer, is that the relative position of capacitor plate can change along with the change of pressure, thus causes the change of electric capacity, by the measurement of testing circuit to electric capacity, realizes the measurement of pressure.The problem of the impact that this sensor eliminates the electric leakage of silicon piezoresistance type pressure sensor PN junction, electrical resistance temperature variation is brought, also there is the advantage of low-power consumption simultaneously, it is the desired pressure sensor of medium accuracy pressure detection, but due to the difference in electric capacity processing mode method, performance difference is also very large.Patent documentation 1 " capacitor type semiconductor pressure sensor " (application number: 03147270.2) propose to adopt polysilicon to make movable capacitor plate, the capacity plate antenna (plate capacitor) that metal fixed electorde and a movable polysilicon barrier film are formed, be arranged in a non-monocrystalline silicon substrate, become a kind of capacitor type semiconductor pressure sensor, the pressure transducer that this method makes comes far short of what is expected compared with stainless steel or monocrystalline silicon due to polysilicon Young modulus, cause polysilicon barrier film fatigue resistance poor, therefore reliability is not high, in addition, cavity between this electric capacity is apart from little, capacitance variations scope is little, very high requirement is proposed to peripheral electric circuit inspection, polysilicon barrier film and the lead-in wire of induction ambient pressure are coplanars, need to increase protection technique and protect lead-in wire, avoid by ectocine.Patent documentation 2 " the large relative variation capacitive pressure transducer of high q-factor " (application number: 201010548819.3), propose to form capacitor by the elastic vibration diaphragm of periphery fixed, by the ratio of adjustment circular electrode and vibrating diaphragm radius, the means such as salient point that insulate are set, vibrating diaphragm is made to be in large sstrain state, maximum capacitor is large as far as possible with the ratio of initial capacitance, thus makes electric capacity reach the object of large relative variation, high q-factor.Although the method can realize bulky capacitor change, reduce the requirement of peripheral testing circuit, vibrating diaphragm can adopt the stainless steel material of high Young's modulus to make, improve fatigue resistance, further raising reliability, but the volume of whole electric capacity is comparatively large, and mass production capabilities is poor
Summary of the invention
In view of this, the object of the present invention is to provide a kind of capacitance pressure transducer, and preparation method thereof.
For achieving the above object, the invention provides following technical scheme:
A kind of capacitance pressure transducer, comprise the capacity plate antenna be made up of conductive single crystal silicon movable electrode plate and metal fixed electorde, it is characterized in that: also comprise conductive single crystal silicon base and be arranged on the conductance supporting structure between conductive single crystal silicon movable electrode plate and conductive single crystal silicon base, form airtight chamber in the middle of described conductive single crystal silicon movable electrode plate, conductive single crystal silicon base and conductance supporting structure, described metal fixed electorde is arranged in the conductive single crystal silicon base of airtight chamber inside; Described conductive single crystal silicon base comprises multiple conductive single crystal silico briquette insulated from each other, be communicated with metal fixed electorde with conductive single crystal silicon movable electrode plate during each piece of equal difference in described multiple conductive single crystal silico briquette, but at least respectively have one piece to be communicated with metal fixed electorde with conductive single crystal silicon movable electrode plate respectively.
Preferably, described conductive single crystal silicon movable electrode plate comprises monocrystalline silicon electrode barrier film and monocrystalline silicon support column, and this electrode diaphragm bottom is provided with elastic membrane chamber, and top is provided with movable plate chamber.
Preferably, described conductive single crystal silicon movable electrode sheet material matter is N+ type monocrystalline silicon, and described monocrystalline silicon electrode membrane thicknesses is 105-155 μm, and the degree of depth of elastic membrane chamber is 250 ± 10 μm, and the degree of depth of movable plate chamber is 20 ± 5 μm.
Preferably, described conductive single crystal silicon base comprises two pieces, left and right insulated from each other, monocrystal silicon substrate top, two pieces, described left and right is respectively equipped with conductive terminals, bottom is respectively equipped with projection, Gui Cao district between the monocrystal silicon substrate of two pieces, described left and right and the isolated area of lower surface except projection are equipped with insulating material, and described conductance supporting structure directly contacts with the projection on left side or right side respectively with metal fixed electorde.
Preferably, described conductive single crystal silicon base material is N+ type monocrystalline silicon, and thickness is 400 ± 10 μm, and resistivity is 0.008-0.01 Ω .cm; Described metal fixed electorde material is the silicon-aluminium alloy of silicon content 0.7-1.2%, and thickness is 1.2 ± 0.1 μm.
Preferably, described insulating material is glass dust.
Preferably, conductance supporting structure is titanium-tungsten and Alpax two layer composite structure.
Preferably, the lower surface of described metal fixed electorde is provided with silicon dioxide layer.
The present invention prepares the method for described capacitance pressure transducer, first prepares conductive single crystal silicon movable electrode plate, then prepares fixed electorde, finally group to gained monocrystalline silicon movable electrode plate and fixed electorde and remove fixed electorde excess portion and get product.
Further, described conductive single crystal silicon movable electrode plate is obtained by following steps:
1), choose N+ type monocrystalline silicon piece and carry out twin polishing;
2), oxidation step 1) monocrystalline silicon piece, make its Surface Creation silicon dioxide layer;
3), in step 2) monocrystalline silicon piece double-sided deposition silicon nitride layer;
4), etching removes silicon nitride and the silicon dioxide at elastic membrane chamber place;
5), etching removes the silicon nitride at movable plate chamber place;
6) etching solution, is utilized to etch the silicon at elastic membrane chamber place for the first time;
7), etching removes the silicon dioxide at movable plate chamber place;
8), with the silicon at step etching movable plate chamber and elastic membrane chamber place to designated depth;
9), remaining silicon nitride and silicon dioxide is removed.
Further, comprise the following steps when preparing described fixed electorde:
1), N+ is chosen
Type monocrystalline silicon piece, single-sided polishing, two-sided oxidation make its Surface Creation silicon dioxide layer;
2), removal step 1 is etched) silicon dioxide at monocrystalline silicon piece polished surface Gui Cao district and isolated area place;
3), first etching removes the silicon in Gui Cao district;
4), synchronous etching removes the silicon at Gui Cao district and isolated area place;
5), remaining silicon dioxide layer is removed;
6), glass dust is evenly coated in Gui Cao district and isolated area position and hot setting;
7), in step 6) monocrystalline silicon Gui Cao district surface sputtering aluminium silicon fixed electorde, at isolated area surface sputtering Alpax layer, the projection contacts that described aluminium silicon fixed electorde is different from monocrystalline silicon piece bottom respectively with Alpax layer and not conducting between the two;
8), in step 7) Alpax layer surface sputtering one deck titanium-tungsten.
Further, pressure transducer group is to carrying out as follows:
1), conductive single crystal silicon movable electrode plate and fixed electorde are aimed at superimposed, and accelerate the metal diffusion in conductance supporting structure, make both reliable bond;
2), by step 1) fixed electorde silicon chip that bonding is good carries out thinning, polishing, exposes the insulating material in isolation channel;
3), in step 2) the fixed electorde back side, isolation channel both sides sputter respectively or evaporate the lead-in wire electrode arranging two capacitor plates.
Beneficial effect of the present invention is:
The present invention is as electric capacity movable plate after low resistance monocrystalline silicon piece tow sides erode away deep trouth, and the elastic membrane chamber of contact ambient pressure can be used to the thickness regulating monocrystalline silicon thin film, and movable plate chamber can be used to the electric capacity between control capacitance pole plate; The degree of depth of the electric capacity movable plate chamber of this structure can reach 10-30 μm, far above conventional capacitance polar plate spacing, can significantly increase capacitance variations value, and then improves the sensitivity of sensor and reduce the complexity of circuit; In addition, it is high that this structure also has Young modulus, non-damageable advantage.Fixed electorde of the present invention is made up of the monocrystal silicon substrate that polylith is insulated from each other, metal electrode directly guides to the exit of electric capacity by the projection of low-resistance silicon, movable low-resistance silicon movable plate electrode is connected with another projection of low-resistance silicon by conductance supporting structure, and then another exit of electric capacity is guided to by low-resistance silicon, and the exit of electric capacity is arranged on the back side, effectively simplify circuit, avoid the metal of electric capacity exit by external influence.
Accompanying drawing explanation
In order to make object of the present invention, technical scheme and beneficial effect clearly, the invention provides following accompanying drawing and being described:
Fig. 1 is the cross sectional shape figure of embodiment 1 capacitance pressure transducer;
Fig. 2 is the N+ type monocrystalline silicon piece a cross sectional shape figure of embodiment 1;
Fig. 3 is that the N+ type monocrystalline silicon piece a of Fig. 2 is oxidized, cross sectional shape figure after deposited silicon nitride;
Fig. 4 is Fig. 3 first photoetching elastic membrane region silicon, removes the cross sectional shape figure after the silicon nitride of movable plate region;
Fig. 5 is the cross sectional shape figure after Fig. 4 synchronously etches elastic membrane region and movable plate region silicon;
Fig. 6 is the cross sectional shape figure after Fig. 5 removes silicon nitride, silicon dioxide;
Fig. 7 is the N+ type monocrystalline silicon piece A cross sectional shape figure of embodiment 1;
Fig. 8 is the cross sectional shape figure after the N+ type monocrystalline silicon piece A oxidation processes of Fig. 7;
Fig. 9 is that Fig. 8 removes the silicon dioxide layer of Gui Cao district C and isolated area D and the cross sectional shape figure after first bite Gui Cao district C place monocrystalline silicon;
Figure 10 is after the monocrystalline silicon of synchronous corrosion diagram 9 Zhong Guicao district C and isolated area D and removes the cross sectional shape figure after remaining silicon dioxide layer;
Figure 11 be Figure 10 Zhong Guicao district C and isolated area D coated glass powder slurry, solidification polishing after cross sectional shape figure;
Figure 12 is Figure 11 sputtered silicon aluminium lamination and cross sectional shape figure after photoetching;
Figure 13 is the cross sectional shape figure after the golden also photoetching of Figure 12 deposit silicon dioxide layer and titanium tungsten;
Figure 14 be embodiment 1 Figure 13 and Fig. 6 is aimed at superimposed after cross sectional shape figure.
Embodiment
Below in conjunction with accompanying drawing, the preferred embodiments of the present invention are described in detail.
Embodiment 1:
As shown in Figure 1, the capacitance pressure transducer, of the present embodiment, comprise the capacity plate antenna be made up of conductive single crystal silicon movable electrode plate 1 and metal fixed electorde 2, also comprise conductive single crystal silicon base 3 and be arranged on the conductance supporting structure 4 between conductive single crystal silicon movable electrode plate 1 and conductive single crystal silicon base 3, form airtight chamber in the middle of described conductive single crystal silicon movable electrode plate 1, conductive single crystal silicon base 3 and conductance supporting structure 4, described metal fixed electorde 2 is arranged in the conductive single crystal silicon base 3 of airtight chamber inside; Described conductive single crystal silicon base 3 comprises multiple conductive single crystal silico briquette insulated from each other, be communicated with metal fixed electorde 2 with conductive single crystal silicon movable electrode plate 1 during each piece of equal difference in described multiple conductive single crystal silico briquette, but at least respectively have one piece to be communicated with metal fixed electorde 2 with conductive single crystal silicon movable electrode plate 1 respectively.
In the present embodiment, described conductive single crystal silicon movable electrode plate 1 comprises monocrystalline silicon electrode barrier film 1-1 and monocrystalline silicon support column 1-2, and this electrode diaphragm bottom is provided with elastic membrane chamber 1-4, and top is provided with movable plate chamber 1-3.
In the present embodiment, described conductive single crystal silicon movable electrode plate 1 material is N+ type monocrystalline silicon (low-resistance silicon), described monocrystalline silicon electrode barrier film 1-1 thickness is 105-155 μm, and the degree of depth of elastic membrane chamber 1-4 is 250 ± 10 μm, and the degree of depth of movable plate chamber 1-3 is 20 ± 5 μm.
In the present embodiment, described conductive single crystal silicon base 3 comprises two pieces, left and right insulated from each other 3-1,3-2, two pieces, described left and right monocrystal silicon substrate 3-1,3-2 top are respectively equipped with conductive terminals 3-5, bottom is respectively equipped with protruding 3-4, Gui Cao district 3-3 between two pieces, described left and right monocrystal silicon substrate 3-1,3-2 and the isolated area 3-6 of lower surface except protruding 3-4 is equipped with insulating material, and described conductance supporting structure 4 and metal fixed electorde 2 directly contact with the protruding 3-4 on left side or right side respectively.
In the present embodiment, described conductive single crystal silicon base 3 material is N+ type monocrystalline silicon, and thickness is 400 ± 10 μm, and resistivity is 0.008-0.01 Ω .cm; Described metal fixed electorde 2 material is the silicon-aluminium alloy of silicon content 0.7-1.2%, and thickness is 1.2 ± 0.1 μm.
In the present embodiment, described insulating material is glass dust.
In the present embodiment, conductance supporting structure 4 is titanium-tungsten 4-1 and Alpax 4-2 two layer composite structure.
In the present embodiment, the lower surface of described metal fixed electorde 2 is provided with silicon dioxide layer 2-1.
The present embodiment prepares the method for capacitance pressure transducer, comprises the following steps:
One, conductive single crystal silicon movable electrode plate is prepared:
1) choose N+ type monocrystalline silicon piece a, as shown in Figure 2 and carry out twin polishing (100 crystal orientation, thickness 400 ± 10 μm, resistivity 0.008-0.01 Ω .cm);
2), cleaning, oxidation step 1) monocrystalline silicon piece a, make its Surface Creation thickness be the silicon dioxide layer b of 1 ± 0.1 μm;
3), in step 2) the two-sided LPCVD deposited silicon nitride layer c of monocrystalline silicon piece, thickness is 130 ± 10nm, as shown in Figure 3;
4), the elastic membrane region d of photoetching induction ambient pressure, etch away silicon nitride c on this region and silicon dioxide b by dry method and wet process, remove photoresist;
5), dual surface lithography movable plate region e, fallen the silicon nitride c on this region by dry etching, leave silicon dioxide b, remove photoresist;
6), KOH+H is adopted
2the silicon of aqueous solution (EPW) the corrosion area d of O or ethylenediamine, catechol, etching depth is 230 ± 10 μm, and at this moment because movable plate region e has silicon dioxide to protect, the silicon below it is not corroded, as shown in Figure 4;
7), adopt the method for wet etching silicon dioxide, erode the silicon dioxide b of movable plate region e, the silicon dioxide b of other region having silicon nitride c to protect below it is not corroded;
8), KOH+H is adopted
2the aqueous solution (EPW) of O or ethylenediamine, catechol is with the silicon of step etching movable plate region e and elastic membrane region place d, and the degree of depth of control corrosion rate is 20 ± 5 μm, and at this moment the silicon degree of depth of elastic membrane region d is 250 ± 10 μm, as shown in Figure 5;
9), remove remaining silicon nitride c and silicon dioxide b on silicon chip, complete the preparation of conductive single crystal silicon movable electrode plate, as shown in Figure 6.
Two, fixed electorde is prepared:
1), N+ type monocrystalline silicon piece A (100 crystal orientation, single-sided polishing sheet, thickness 400 ± 10 μm, resistivity 0.008-0.01 Ω .cm) is chosen, as shown in Figure 7;
2), clean, oxidation, obtains at monocrystalline silicon surface the silicon dioxide layer B that thickness is 1 ± 0.1 μm, as shown in Figure 8;
3), first adopt photoetching method to make monocrystalline silicon piece polished surface Gui Cao district C and isolated area D by lithography, then wet etching removes the silicon dioxide layer B at Gui Cao district C and isolated area D place, removes photoresist;
4), first adopt photoetching method cover to carve the Gui Cao district C of isolation silicon electrode, solidification photoresist, then adopts the silicon of dry etching Gui Cao district C, etch depth is 150 ± 20 μm, removes photoresist, and now isolated area D protects owing to there being photoresist, the silicon in this region is not corroded, as shown in Figure 9;
5), adopt dry method synchronously to etch the silicon removing Gui Cao district C and isolated area D place, controlling etch depth is 80 ± 10 μm, and the degree of depth of now isolating silicon electrode Gui Cao district C is 230 ± 20 μm;
6), remaining silicon dioxide layer is removed, as shown in Figure 10;
7), adopt spin coating method, the glass dust E of liquid state is coated on region C, D equably, then solidifies in the alloying furnace of 400 degree;
8), adopt CMP finishing method, by the glass dust E leveling on region C, D, allow and do not need the silicon in filling glass powder region out exposed, as shown in figure 11;
9), first adopt sputtering method, sputter one deck sial F at N+ type monocrystalline silicon piece A lower surface, sial silicon content is 1%, thickness is 1.2 ± 0.1 μm, by photoetching method, make sial metal polar plate and the becket for metallic bonding by lithography, as shown in figure 12;
10), employing pecvd process is the silicon dioxide G of 120 ± 20nm in sial metal polar plate surface precipitation a layer thickness;
11), utilize fuming nitric aicd to clean, be then 200 ± 20nm titanium tungsten gold H in the becket surface sputtering a layer thickness for metallic bonding, in this titanium tungsten gold H, titanium tungsten mass ratio is 1:1, as shown in figure 13.
Three, pressure transducer group pair:
1) fuming nitric aicd cleaning step two gained fixed electorde, is first used, cleaning step one gained conductive single crystal silicon movable electrode plate, then with corrosion under the HF dilution normal temperature of 50:1 4 minutes, remove natural oxidizing layer on silicon chip 1, finally utilize double face photoetching machine aforementioned fixed electorde and conductive single crystal silicon movable electrode plate, aligning to be stacked together;
2) under vacuum pressed, metal, is carried out diffusion interlinked, such fixed electorde and conductive single crystal silicon movable electrode plate are bonded together securely, silicon chip due to movable electrode plate has the deep trouth of a control capacitance variation range, the silicon chip of such silicon elastic film is exactly electric capacity movable electrode plate, and the sheet metal on glass dust is exactly the fixed polar plate of electric capacity, the variable capacitance of bottom crown in formation, as shown in figure 14;
3), by step 1) fixed electorde silicon chip that bonding is good carries out thinning, polishing, exposes the glass dust E in isolation channel C;
4), adopt sputtering method deposit one deck sial 15 on the face of glass dust isolation channel of exposing silicon chip, make the lead-in wire electrode of two plates capacitances by lithography, obtain as shown in Figure 1;
5), alloy (440 degree, nitrogen hydrogen alloy, half an hour), allow lead-in wire electrode metal and N+ silicon form good Ohmic contact, obtain capacitance pressure transducer, of the present invention, its structure is as shown in Figure 1.
It should be noted that, process used in the inventive method, except being described in detail, other, as cleaning, oxidation; Deposit silicon nitride, silicon dioxide; Splash-proofing sputtering metal; Dry etching silicon nitride, silicon; Wet etching silicon dioxide, silicon; Photoetching; Remove photoresist; Alloy, the technique such as thinning, polishing is all the common process technology in this integrated circuit and MEMS field, no longer auspiciously states.
Needs illustrate, claims forms part and specific embodiment part employ different Reference numerals to same parts, it will be appreciated by those skilled in the art that above-mentioned different Reference numeral is only used to facilitate language to describe, can't cause ambiguity.
What finally illustrate is, above preferred embodiment is only in order to illustrate technical scheme of the present invention and unrestricted, although by above preferred embodiment to invention has been detailed description, but those skilled in the art are to be understood that, various change can be made to it in the form and details, and not depart from claims of the present invention limited range.