CN1111741C - Integrated silicon microresistance type acceleration sensor and its manufacturing method - Google Patents

Abstract

The present invention provides an integrated silicon micro-resistance acceleration sensor and a fabrication method thereof. The acceleration sensor comprises a base, a casing and a detecting chip which is composed of a mass block supported by eight strain beams, a voltage dependent resistor and an electric bridge circuit. The processing technological methods of double-polish silicon wafers special for micro machines, SiO2 protective layers, photolithography, phosphorus diffusion, phosphorous ion implantation, annealing (silicon wafers), EPW anisotropic etching, RIE corrosion, etc. are mainly used by the present invention. A measuring part of the integrated silicon micro-resistance acceleration sensor is of an integral structure whose anti-overload capability is strong. One sensor can be used for detecting the acceleration in arbitrary directions from one dimension to three dimension.

Description

Little resistance-type acceleration transducer of integrated silicon and manufacturing job operation thereof

One, technical field

The present invention belongs to the testing sensor technical field, relates to the little resistance-type acceleration transducer of a kind of integrated silicon and makes job operation.

Two, background technology

Acceleration transducer is to measure various machineries, vehicle, boats and ships, the kinematic parameter of aerospace device and the sensor commonly used of vibration data, and traditional acceleration sensor structure has piezoelectric type.It is by the one or more piezoelectric patches that are contained under the mass; and by spring compression on a quite thick metal base; its outer housing that the protection piezoelectric patches is arranged, in the certain frequency scope, the quantity of electric charge that piezoelectric patches presented will be directly proportional with the acceleration that sensor is born.Spring and housing as the ectosome fixed tighten together, pedestal, housing are the parts of spring one quality system, its shortcoming is that the distortion of extraneous temperature, noise and test specimen will be influenced the output of acceleration by shell and pedestal reaction, and the signal of its output is little, the output impedance height.In addition, also have strain gauge acceleration transducer, adopt mass, elastic beam, strainometer, pedestal and shell structure.Though overcome the above-mentioned shortcoming of piezoelectric acceleration transducer, its structure makes the acceleration transducer of making bigger, has influenced usable range.

Along with large scale integrated circuit, chip fabrication techniques, and the development of micromachining technology in recent years.Produced at silicon wafer (semiconductor) and gone up the formation metallic film, produced semiconductor acceleration sensor through etching.U.S. Pat 005760290A discloses a kind of semiconductor acceleration sensor and method of testing thereof.It mainly contains housing, glass pedestal, silicon chip detection bodies, stress sensitive part, mass part, voltage dependent resistor (VDR); Detection bodies its center again is the mass of fine motion, is four crossbeams that are symmetrically distributed around the mass, is used to support mass, and responsive part is four crossbeams, and its test section is made of glass pedestal and silicon chip detection bodies.It is unidirectional acceleration transducer, only is suitable for the measurement of unidirectional acceleration, and the measurement during to three-dimensional and uncertain direction needs to require the precision height of its installation with three sensors, because not on same point, the error of its measurement is bigger.

Three, summary of the invention

The objective of the invention is to overcome existing deficiency of above-described acceleration transducer and shortcoming thereof, it is one-piece construction that a kind of measure portion is provided, anti-overload ability is strong, can carry out integrated silicon little resistance-type acceleration transducer machine and manufacture method thereof that one dimension is measured to three-dimensional acceleration.

The little resistance-type acceleration transducer of a kind of integrated silicon provided by the present invention, comprise pedestal, be contained in the housing that shields on the pedestal, by the stress sensitive part, the mass body portion, voltage dependent resistor (VDR) and the detection chip that bridge diagram constituted, detection chip center are the masses of fine motion, are being symmetrically distributed to be used for bearing mass piece and responsive eight beams of beam partly of conduct around mass; It is characterized in that: described voltage dependent resistor (VDR) is infused on the maximum stress point position and detection chip outward flange on every beam of detection chip for adopting phosphonium ion; Described voltage dependent resistor (VDR) is formed the bridge diagram of measured X, Y, three directional accelerations of Z respectively, wherein:

R1=R2=R3=R4=R5=R6=R7=R8=R12=R13=R, R9=R10=R11=4R and R9, R10, R11, R12, R13 are the fixed resistance on the detection chip outward flange;

The voltage dependent resistor (VDR) of detection chip be connected electric bridge low-resistance lead on the SiO2 protective seam is arranged.

The mass of the little resistance-type acceleration transducer of above-described a kind of integrated silicon is a positive water chestnut stage body, and its four sides and bottom surface be the angle of promising α all, and the periphery sides of bearing strain beam is trapezoidal, the angle of medial surface and the promising β in bottom surface.

The manufacturing job operation of the little resistance-type acceleration transducer of a kind of integrated silicon of the present invention, the main manufacturing process of described detection chip comprises:

(1) selects materials, get the special-purpose two silicon wafers of throwing of micromechanics;

(2) adopt the SiO2 protective seam;

(3) photoetching, lead, resistance, mass and rhombus platform;

(4) phosphorous diffusion legal system is made the low-resistance lead;

(5) phosphonium ion injects and forms N type voltage dependent resistor (VDR);

(6) annealing (silicon chip);

(7) the EPW anisotropic etch goes out mass and rhombus platform shape;

(8) RIE corrosion, dry etching goes out strain beam.

The little resistance-type acceleration transducer of a kind of integrated silicon provided by the present invention.It and background technology are relatively.Be miniature one-piece construction, on same point, can carry out the measurement of three-dimensional acceleration simultaneously.The precision height of its orientation measurement, the error of measurement is less.Use it can carry out the acceleration detection of one dimension to three peacekeeping any directions.

Detection chip to acceleration transducer adopts the Ansys analysis software to carry out simulation calculation.Though structure is a two-dimensional symmetric, and is stressed asymmetric, and for the separability of analytical structure to 3-axis acceleration, carried out simulation calculation to one-piece construction, Figure 8 shows that the finite element model of acceleration transducer.Choose 45 nodes of Solid and 3D unit, all unit are the standard rectangular structure, and the ratio that length and width are high approaches 1, totally 8868 unit, 10080 nodes.Material behavior is pressed following calculating: elastic modulus: Ex=130 * 10^9Pa, modulus of shearing: G=79 * 10^9Pa, density: 2.33 * 10^3Kg/m^3, Poisson ratio: 0.18.Fig. 9, Figure 10 and shown in Figure 11 being respectively are subjected to x, y, and the deformation pattern of structure under the situation of z unidirectional load, and Figure 12 shows that x, y, the deformation pattern of structure under the situation of z three direction resultant loads.Figure 13 shows that displacement curve.Figure 14 shows that stress curve.Simulation result and test result are close, and its monodrome error and has been verified in micron-sized stress and the little theory of scale effect relation in 10% scope.Through above simulation analysis of computer result, the little resistance-type acceleration transducer of a kind of integrated silicon provided by the invention has good reliability and durability.

The manufacturing job operation of the chip of the little resistance-type acceleration transducer of a kind of integrated silicon provided by the present invention.The used silicon chip of it and microelectronics processing is incomplete same, requires that based on the piezoresistive transducer of piezoresistive effect high piezoresistance coefficient is arranged, and the position of voltage dependent resistor (VDR) is in the maximum direction of silicon wafer piezoresistance coefficient.Adopted the special-purpose two silicon wafers of throwing of micromechanics, P type (100) face is made substrate, and resistive layer has adopted phosphonium ion to inject as N type voltage dependent resistor (VDR), and uses technologies such as photoetching plate-making, corrosion and annealing.Guaranteed to have produced by designing requirement contain that precision height, anti-overload ability are strong, temperature and zero point drift is little, the three dimension acceleration sensor of the detection chip of good stability.

Four, description of drawings:

Fig. 1 is the little resistance-type acceleration sensor structure of an integrated silicon synoptic diagram;

Fig. 2 is eight variable shaped beam acceleration sensor chip structural front view;

Fig. 3 is eight variable shaped beam acceleration sensor chip structure cut-open views;

Fig. 4 is resistance, wire arrangements figure on eight variable shaped beam acceleration sensor chips;

Fig. 5 is that x is to bridge diagram figure;

Fig. 6 is that y is to bridge diagram figure;

Fig. 7 is that z is to bridge diagram figure;

Fig. 8 is the finite element model of acceleration transducer;

Fig. 9 is the deformation pattern of structure under the situation of x unidirectional load;

Figure 10 is the deformation pattern of structure under the situation of y unidirectional load;

Figure 11 is the deformation pattern of structure under the situation of z unidirectional load;

Figure 12 is x, y, the deformation pattern of structure under the situation of z three direction resultant loads;

Figure 13 is displacement curve figure;

Figure 14 is stress curve figure;

Figure 15 is x axle mechanical model figure when stressed;

Figure 16 is y axle mechanical model figure when stressed;

Figure 17 is z axle mechanical model figure when stressed;

Figure 18 is the window synoptic diagram before the EPW system corrosion of silicon;

Figure 19 is the window synoptic diagram behind the EPW system corrosion of silicon;

Figure 20, Figure 21 and Figure 22 are the convex corner compensation synoptic diagram of EPW system corrosion of silicon mask;

Figure 23 is the photo figure in kind of the result after the three dimension acceleration sensor chip manufacture;

Five, embodiment

Say concrete enforcement of the present invention in detail below in conjunction with accompanying drawing.

Fig. 1, the little resistance-type acceleration transducer of a kind of integrated silicon comprises pedestal 801, is contained in the housing 802 that shields on the pedestal, by the stress sensitive part, mass body portion, voltage dependent resistor (VDR) and the detection chip 803 that bridge diagram constituted; Fig. 2 is described detection chip, and the heart is the mass 804 of fine motion therein, the described responsive part that is being symmetrically distributed around mass, eight strain beams 805 that are used for the bearing mass piece.Its mass and strain beam are constituted by the whole piece monocrystalline silicon piece that adopts the micromachined moulding.The voltage dependent resistor (VDR) of detection chip be connected electric bridge low-resistance lead on the SiO2 protective seam is arranged.

Fig. 3, shown in mass in the acceleration sensor chip be a positive water chestnut stage body, its four sides and bottom surface be the angle of promising α all, and the periphery sides of bearing strain beam is trapezoidal, the angle of medial surface and the promising β in bottom surface.The best angle of its α and β is 54.7 °.

Fig. 4, the resistance-type acceleration transducer, described voltage dependent resistor (VDR) is that the employing phosphonium ion is injected into the electric resistance structure on the silicon chip, the maximum stress point place of its position on every beam.Its maximum stress point place concerning eight strain beams that are used for the bearing mass piece, can be determined by following computing method:

The mechanical structure calculation of parameter

The accelerometer mass is obtained by the EPW anisotropic etch.The mass of acceleration transducer is a positive truncated rectangular pyramids, and four sides of truncated rectangular pyramids and the angle of bottom surface are 54.7 °, as shown in Figure 5.Last bottom side length is a1, and the length of side of going to the bottom is b, highly is H, and the volume of mass is V, and the quality of mass is m, and the distance on center and xoy plane is zc.Beam length is l, and width is w, and thickness is h, and the spacing between two beam centers is a2, and barycenter is zC to the distance of upper surface.Get a1=800 μ m, l=750 μ m, H=340 μ m, w=68 μ m, h=40 μ m, a2=400 μ m mass goes to the bottom width b=a1-2 * H/tg54.7 °=800 * 10 ^-6-2 * (300 * 10 ^-6)/tg54.7 °=375 * 10 ^-6M mass volume V=1/3H (a ₁ ²+ b ²+ a ₁B)=1.08 * 10 ^-10m ³Position Zc=1.02 * 10 of mass barycenter ^-4m

The acceleration a of an any direction can be decomposed into ax, ay, three components of acceleration of az in x, y, three directions of z.The speed a that is subjected to adding arbitrarily direction when accelerometer does the time spent, and force analysis is as follows: following various in E--Young's modulus of elasticity＜100〉E=1.3 * 1011pa;

G--shear elasticity＜100〉G=7.9 * 107Pa;

μ--Poisson ratio＜100〉μ=0.18; When A. only bearing the acceleration ax of x direction, acceleration is decomposed into two (one) is subjected to inertial force in the y plane-max effect, distortion is symmetrical in the x axle, is illustrated in fig. 15 shown below.Stressing conditions is symmetrical in the x axle, and at the stressed equal and opposite in direction of y axle two curb girders, direction is opposite.So only need 1/4th stressing conditions of analytical structure, beam 1-2,3-4, beam 3-4 stressing conditions: be subjected to axle pressure at Liang3Chu $N_3=\frac{\mathrm{Ewh}}{l}\mathrm{\Δx}$ Be subjected to axle pressure N at Liang4Chu ₄=N ₃3, the 4 compression chord σ of place _3xi=σ _4xi=-N ₃/ wh beam 3-4 is subjected to maximum stress σ _3-4ximax=σ 3 _Xi=σ _4xiThe stressing conditions of beam 1-2: Liang2Chu is subjected to shearing $Q_{2\mathrm{xi}}=\frac{\mathrm{Eh}{w}^3}{l^3}\mathrm{\Δx}$ Liang1Chu is subjected to shearing Q _1xi=Q _2xiThe moment of flexure of Liang2Chu $M_{2\mathrm{xi}}=\frac{{\mathrm{ma}}_{x}l\frac{w^2}{l^2}}{8(1+\frac{w^2}{l^2})}$ The moment M of Liang1Chu _1xi=M _2xiBeam 1,2 place is subjected to maximum stress σ _1xi=M _1i/ hw ²=σ _2xi, occur in lateral beam 1-2 and be subjected to maximum stress σ _1-2ximax=σ _1xi=σ _2xiWherein Δ x is the displacement of mass in the x direction, $\mathrm{\Δx}=\frac{{\mathrm{ma}}_x}{\frac{4\mathrm{Ewh}}{l}(1+\frac{w^2}{l^2})}$

(2) be subjected to around y axle moment of inertia-mayzC effect, distortion is symmetrical in the x axle, is illustrated in fig. 16 shown below.So only need 1/4th of analytical structure, beam 1-2,3-4, the stressed feelings stressing conditions of beam 1-2 is symmetrical in the x axle, and at the stressed equal and opposite in direction of y axle two curb girders, the opposite condition of direction: 1,2 place is subjected to shearing $Q_{1\mathrm{xm}}=Q_{2\mathrm{xm}}=\frac{\mathrm{Eh}{w}^3{a}_2}{{2l}^3}{\mathrm{\θ}}_y$ Liang2Chu is subjected to moment of flexure $M_{2\mathrm{ym}}=\frac{\mathrm{Ew}{h}^2{a}_2}{4l^2}{\mathrm{\θ}}_y$ Liang1Chu is subjected to moment M _1xm=M _2xm1 place's maximum stress occurs in back on the beam ${\mathrm{\σ}}_{1\mathrm{xm}}=-\frac{M_{1\mathrm{xm}}}{\frac{w{h}^2}{6}}$ 2 place's maximum stresses occur in back on the beam ${\mathrm{\σ}}_{2\mathrm{xm}}=\frac{M_{2\mathrm{xm}}}{\frac{w{h}^2}{6}}$ Beam 1-2 is subjected to maximum stress σ _1-2xm=σ _1xm=σ _2xmBeam 1-2 is subjected to torsional interaction $M_{\mathrm{Tx}12}=\frac{\mathrm{Gw}{h}^3}{3l}{\mathrm{\θ}}_y$ Shear stress is identical in beam 1-2 cross section ${\mathrm{\τ}}_{x1}={\mathrm{\τ}}_{x2}=\frac{M_{\mathrm{Tx}12}}{\frac{1}{3}w{h}^2}$ Maximum shear occurs in the back mid point ${\mathrm{\τ}}_{\max }=\frac{M_{\mathrm{Tx}12}}{0.25w{h}^2}$ The stressing conditions of beam 3-4: 3,4 places are subjected to shearing $Q_{3\mathrm{xm}}=Q_{4\mathrm{xm}}=\frac{\mathrm{Ew}{h}^3}{2l^2}(a_1+1){\mathrm{\θ}}_y$ Liang3Chu is subjected to moment of flexure $M_{3\mathrm{xm}}=\frac{\mathrm{Ew}{h}^3}{12l^2}({3a}_1+2l){\mathrm{\θ}}_y$ Liang4Chu is subjected to moment of flexure $M_{3\mathrm{xm}}=\frac{\mathrm{Ew}{h}^3}{12l^2}({3a}_1+4l){\mathrm{\θ}}_y$ At beam 3 place's maximum crushing stresses ${\mathrm{\σ}}_{3\mathrm{xm}}=-\frac{\left|M_{2\mathrm{xm}}\right|}{\frac{w{h}^2}{6}}$ At beam 4 place's maximum tension stresses ${\mathrm{\σ}}_{4\mathrm{xm}}=-\frac{\left|M_{2\mathrm{xm}}\right|}{\frac{w{h}^2}{6}}$ Beam 3-4 is subjected to maximum stress σ _3-4xmmax=σ _3xm=σ _4xmWherein θ y is the corner of mass, ${\mathrm{\θ}}_y=\frac{3m{a}_x{z}_c{l}^3}{w{h}^3[E(6a_{1}l+3a_1^2+4l^2)+3a_2^{2}E+4G{l}^2]}$ B. bear y directional acceleration ay () and be subjected to inertial force in the xoy plane-may effect, distortion is symmetrical in the y axle.Stressing conditions is symmetrical in the y axle, and at the stressed equal and opposite in direction of x axle two curb girders, direction is opposite.So only need 1/4th of analytical structure, beam 1-2,3-4, the stressing conditions of beam 1-2: beam 1-2 is subjected to axle pressure $N_1=N_2=\frac{\mathrm{Ewh}}{l}\mathrm{\Δy}$ Beam 1-2 is subjected to axial compression stress σ _1yi=σ _2yi=-N ₁/ wh beam 1-2 is subjected to maximum stress σ _1-2yimax=σ _1yi=σ _2yiThe stressing conditions of beam 3-4: 3,4 places are subjected to shearing $Q_{3\mathrm{yi}}=Q_{4\mathrm{yi}}=\frac{\mathrm{Eh}{w}^3}{l^3}\mathrm{\Δy}$ Beam 3 place's moments of flexure $M_{3\mathrm{Yi}}=\frac{{\mathrm{ma}}_{y}l\frac{w^2}{l^2}}{8(1+\frac{w^2}{l^2})}$ Beam 4 place's moment M _4yi=M _3yiBeam 3,4 places are subjected to maximum stress to occur in the side of beam ${\mathrm{\σ}}_{3\mathrm{yi}}={\mathrm{\σ}}_{4\mathrm{yi}}=\frac{M_{3\mathrm{yi}}}{\frac{w^{2}h}{6}}$ Beam 3-4 is subjected to maximum stress σ _3-4yimax=σ _3yi=σ _4yiWherein Δ y is the displacement of mass in the y direction, $\mathrm{\Δy}=\frac{{\mathrm{ma}}_y}{\frac{4\mathrm{Ewh}}{l}(1+\frac{w^2}{l^2})}$ (2) be subjected to around x axle moment of inertia-mayzC effect, distortion is symmetrical in the x axle.Stressing conditions is symmetrical in the y axle, and at the stressed equal and opposite in direction of x axle two curb girders, direction is opposite.So only need 1/4th of analytical structure, beam 1-2,3-4, beam 3-4 is stressed: beam 3,4 place's shearings $Q_{3\mathrm{ym}}=Q_{4\mathrm{ym}}=\frac{\mathrm{Ew}{h}^3{a}_2}{2l^3}{\mathrm{\θ}}_y$ Beam 3 place's moments of flexure $M_{3\mathrm{Ym}}=\frac{M_{3\mathrm{ym}}}{\frac{w{h}^2}{6}}$ Beam 4 place's moments of flexure $M_{3\mathrm{Yi}}=\frac{M_{4\mathrm{ym}}}{\frac{w{h}^2}{6}}$ Beam 3 place's upper surface maximum tension stresses ${\mathrm{\σ}}_{3\mathrm{ym}}=\frac{M_{3\mathrm{ym}}}{\frac{w^{2}h}{6}}$ Beam 4 place's upper surface maximum crushing stresses ${\mathrm{\σ}}_{4\mathrm{ym}}=\frac{M_{4\mathrm{ym}}}{\frac{w^{2}h}{6}}$ Beam 3-4 is subjected to maximum stress σ _3-4yimax=σ _3ym=σ _4ymBeam 3-4 is subjected to torsional interaction $M_{\mathrm{Tx}12}=\frac{\mathrm{Gw}{h}^3}{3l}$ Shear stress caused by torque each cross section on beam 3-4 is identical ${\mathrm{\τ}}_{x3}={\mathrm{\τ}}_{x4}=\frac{M_{\mathrm{Ty}34}}{\frac{1}{3}w{h}^2}$ Maximum shear occurs in the back mid point ${\mathrm{\τ}}_{\max }=\frac{M_{\mathrm{Tx}34}}{0.25w{h}^2}$ Beam 1-2's is stressed: 1,2 place's shearing $Q_{3\mathrm{ym}}=Q_{3\mathrm{ym}}=\frac{\mathrm{Ew}{h}^3}{2l^3}(a_1+l){\mathrm{\θ}}_x$ Beam 1 place's moment of flexure $M_{1\mathrm{ym}}=\frac{\mathrm{Ew}{h}^3}{12l^2}(3a_1+2l){\mathrm{\θ}}_x$ Beam 2 place's moments of flexure $M_{2\mathrm{ym}}=\frac{\mathrm{Ew}{h}^3}{12l^2}(3a_1+4l){\mathrm{\θ}}_x$ Beam 1 place's upper surface maximum tension stress ${\mathrm{\σ}}_{1\mathrm{ym}}=\frac{M_{1\mathrm{ym}}}{\frac{w^{2}h}{6}}$ Beam 2 place's upper surface maximum crushing stresses ${\mathrm{\σ}}_{2\mathrm{ym}}=\frac{M_{2\mathrm{ym}}}{\frac{w^{2}h}{6}}$ Beam 1-2 is subjected to maximum stress σ _1-2ymmax=σ _1ym=σ _2ymWherein θ x is the corner of mass, ${\mathrm{\θ}}_y=\frac{3m{a}_y{z}_c{l}^3}{w{h}^3[E(6a_{1}l+3a_1^2+4l^2)+3a_2^{2}E+4G{l}^2]}$ C. bear z directional acceleration az, structure stress is out of shape as shown in figure 17.Every beam stress situation is identical, only analyzes one of them, and beam 1-2 beam 1,2 is subjected to shearing $Q_{1Z}=Q_{2Z}=\frac{{\mathrm{ma}}_z}{8}$ The moment of flexure of Liang1Chu $M_{1Z}=\frac{{\mathrm{ma}}_z}{16}$ The moment of flexure of Liang2Chu $M_{1Z}=\frac{{\mathrm{ma}}_z}{8}$ The maximum crushing stress of Liang1Chu ${\mathrm{\σ}}_{1Z}=\frac{M_{1Z}}{\frac{{\mathrm{wh}}^2}{6}}$ The tension of Liang2Chu ${\mathrm{\σ}}_{2Z}=\frac{M_{2Z}}{\frac{w{h}^2}{6}}$ Beam 1-2 is subjected to maximum stress σ _1-2zmax=σ _1z=σ _2z

Shown in Figure 4, described voltage dependent resistor (VDR) is formed the bridge diagram of measured X, Y, three directions of Z, its R1=R2=R3=R4=R5=R6=R7=R8=R12=R13=R respectively, R9=R10=R11=4R and R9, R10, R11, R12, R13 are the fixed resistance on the chip outward flange.Electric bridge encourages with constant voltage source Ui, Ui=5V, and Fig. 5, Fig. 6 and shown in Figure 7, and have measured X, and Y, Z, the acceleration bridge diagram of three directions is as follows respectively:

(1), the bridge diagram of directions X, by R7, R8, R12, R13 forms series loop, wherein, tap E between R7 and R8, tap D between R12 and the R13, and be the feeder ear Ui of excitation power supply in tap between R7 and the R12 and between R8 and the R13; And two terminations of E and D are that X is to the acceleration analysis output terminal.

(2), the bridge diagram of Y direction, by R5, R6, R12, R13 forms series loop, wherein, tap C between R5 and R6, tap D between R12 and the R13, and be the feeder ear Ui of excitation power supply in tap between R5 and the R12 and between R6 and the R13; And two terminations of C and D are that Y is to the acceleration analysis output terminal.

(3), the bridge diagram of Z direction, by R1, R2, after R3, the R4 series connection earlier, again with R11, R10, R9 forms series loop; Wherein, tap A between R4 and R11, tap B between R10 and the R9, and be the feeder ear Ui of excitation power supply in tap between R11 and the R10 and between R9 and the R1; And two terminations of A and B are that Z is to the acceleration analysis output terminal.

The present invention is the manufacturing job operation of the chip of the little resistance-type acceleration transducer of a kind of integrated silicon, for concrete processing technology of the acceleration sensor chip of eight variable shaped beam structures and step is:

(1), be equipped with sheet, select the special-purpose double-polished chip of P type (100) micromechanics for use;

(2), once oxidation, generate the SiO2 protective seam

(3), photoetching, the low-resistance wire pattern;

(4), phosphorous diffusion, the low-resistance lead;

(5), secondary oxidation, generate the SiO2 protective seam;

(6), positive photoetching, form resistance pattern;

(7), phosphonium ion injects formation N type piezoresistance;

(8), annealing, eliminate defective, make crystal obtain electric conductivity;

(9), three oxidations, generate the SiO2 protective seam;

(10), back side photoetching, form back side mass activity surplus figure;

(11), the EPW anisotropic etch, erode away mass;

(12), positive photoetching, form the figure of beam;

(13), positive RIE corrosion, dry etching goes out beam, the reactive ion etching of free radical vertical incidence;

(14), four oxidations, generate the SiO2 protective seam;

(15), positive photoetching, form the window that is connected of low-resistance silicon and metal level;

(16), positive photoetching, form the plain conductor layer pattern;

(17), evaporation TiPtAu, form metal carbonyl conducting layer, can anti-EPW mordant;

(18), back side photoetching, carve the figure of mass, comprise convex corner compensation;

(19), the EPW anisotropic etch, erode away the shape of the piece of quality.Critical process in the concrete processing technology of the acceleration sensor chip of above-described eight variable shaped beam structures is described in detail as follows: (one) EPW anisotropic etch

Monocrystalline silicon is anisotropic material, and is different with key density in atom line density, the surface density of different crystal orientations and crystal face, therefore has different physicochemical characteristicss in different directions.The bulk silicon micro mechanic process technology has two kinds of isotropic etch and anisotropic etchs.The anisotropic etch of silicon is meant that the different crystal faces to silicon have different corrosion rates.Anisotropic etch has the characteristics of less sideetching speed than isotropic etch, thus when the processing microtexture the more frequent anisotropic etch of using.Anisotropic etch speed is relevant with the crystal orientation.Anisotropic etchant commonly used has KOH system and EPW system.But KOH system and microelectronics are incompatible.The accelerometer mass is obtained by the EPW anisotropic etchant.EPW is an ethylenediamine, the mixed liquor of catechol and water.The corrosion rate of EPW corrosive liquid and the proportioning of composition, the factors such as doping content of corrosion temperature and silicon substrate are relevant.Anisotropic etch can the limit corrosion crystal face, and { corrosion rate of 111} crystal face is than { slow many of 100} face in the EPW system.The side in the V-shape hole chamber that the mask window that carves on (100) substrate is eroded away along＜110〉direction the time is { 111} crystal face, { 111} and the { angle theta of 100}=54.7 °.With EPW corrosion＜100〉substrate, to the window of any closed figure,, all can occur at last through corrosion for a long time＜110〉orientation and wall be＜111 vestibule.On mask window edge＜110〉square hole.The side of the vestibule that the mask window that carves on (100) substrate is eroded away along＜110〉direction the time is that { the 111} crystal face, { 111} is with { angle theta of 100}=54.7 ° are as Figure 18 and shown in Figure 19.The reaction equation of EPW system corrosion silicon can be expressed as: Wb is the width at vestibule top, and ws is the width of cavity bottom, and h is the vestibule degree of depth of corrosion.w _s＝w _b-2h

(2) convex corner compensation

Anisotropic etch does not corrode re-entrant angle, so the vestibule border in good order.And anisotropic etch often corrodes salient angle, and the corrosion rate of salient angle is relevant with the type of mordant and exposed area.Wish to obtain neat mesa structure when making acceleration transducer, when using EPW corrosive liquid corrosion (100) substrate in the reality, when mask was rectangle, corrosion presented dodecagon through the short period, and long-time corrosion is octagon.Table top salient angle sideetching is relevant with factors such as corrosion depth, mordant proportioning types.Corrosion experiment and measurement show, to EPW " B " mordant dip plane be the 212} face, and the 212} face with the intersection of 100} face is＜121 〉.Therefore when making such device, must adopt the method for convex corner compensation.Compensation has two kinds of methods: 1. the drift angle at mask adds compensation; 2. make mask with respect to＜110〉angle of deviation in driction.In design, adopt first method.The method of interpolation compensation bar has several, adopts in the design and adds foursquare scheme, as Figure 20, Figure 21 and shown in Figure 22.EPW " B " mordant (ethylenediamine is used in corrosion, the mol ratio of catechol and water is 43.8%: 4.2%: 52%), under 115 ℃, corrosion depth is H, two dip plane, salient angle place are dc at the intersection point of (100) face to the vertical range of mask drift angle, and the mask edge is d to the distance on constriction point top.D, the physical dimension of dc and w meets following formula:

dc＝dsinα+dcosα (d≤0.5w)

Dc=0.5wcos α+dsin α (dc of d 〉=0.5w), w and corrosion depth H meet following relational expression:

H＝(0.5wsinα+dcosα)/UC (d≤0.5w)

H＝(0.5cosα+dsinα)/Uc (d≥0.5w)

Uc is the normalized value in the experiment in the formula, Uc=dc/H=0.42, and the type of it and mordant, composition proportion and temperature are relevant.α be the 212} face with the intersection of 100} face and＜110〉angle of direction, α=18.50.Work as d=0.5w, during H=340 μ m, can obtain w=225.6 μ m, d=112.8 μ m, Figure 20 of mask, Figure 21 and shown in Figure 22.

(3) RIE dry etching

Though wet etching is widely used in the micromachined, also there are many shortcomings in it, for example uses a large amount of poisonous medicines, and efficient is low; The sideetching effect is arranged, be difficult to obtain high-precision size; Some material (as Si3N4, SiO2, etc.) and insoluble metal are difficult to corrosion etc.So developed some dry etching technology recently.RIE is exactly wherein a kind of.RIE (Reactive Ion Etching) full name is that the reactive ion etching of free radical vertical incidence is also referred to as reactive sputtering corrosion (RSE), and it belongs to a kind of plasma etching.Plasma etching technology has three outstanding advantages: the surface configuration of an etching is controlled easily, does not have remaining etching surface; The back side of two etchings need not protection; Three etching processes are compatible mutually with CMOS technology; Four can obtain bigger depth-to-width ratio.During RIE method dry etching, on anode, add bias voltage, the ion of carrying active particle is accelerated and vertical incidence in the sheet sub-surface, active particle forms etching with etching material chemically reactive.Because directed incident, etching has isotropy, and high-resolution figure is highly beneficial for making.

(4) annealing

Follow ion implantation process, incident ion will have a series of defective around its process, even form damage zone, and the foreign atom that injects often is in interstitial site, and electric conductivity generally is not provided.The semiconductor annealing technology is a thermal effect of utilizing various form of energy to produce, eliminates the semiconductor slice, thin piece and is playing various defectives and the internal stress that the ion injection waits some processes to produce, or make effectively electricity activation of dopant atom.Method for annealing commonly used is the thermal annealing technology.

(5) layout design

Adopt P type wafer to do substrate, inject phosphorus as N type piezoresistance.

Resistive layer adopts ion implantation to obtain, and square resistance is about 400 Ω/.Be connected with low-resistance silicon between piezoresistance and the metal level, low-resistance silicon obtains with diffusion method.The square resistance of low-resistance silicon is about 2 Ω/, and the resistance on every beam is about 30 Ω.Low-resistance silicon is connected with metal wants windowing.The bulk silicon etching of mass will carry out convex corner compensation.

Accelerometer needs 7 lithography mask versions altogether.Resistive layer version wherein, the diffusion layer version, the metal level version, the beam version, reverse side makes the version that activity space is arranged between mass and the base, each one of mass and convex corner compensation version.Positive five, two of reverse side.

Shown in Figure 23 is the photo in kind of the result after the three dimension acceleration sensor chip manufacture.

The little resistance-type acceleration transducer of the integrated silicon of miniature three-dimensional acceleration provided by the present invention has been used for the collision experiment of automobile reliably.

Claims (3)

1, the little resistance-type acceleration transducer of a kind of integrated silicon, comprise pedestal (801), be contained in the housing (802) that shields on the pedestal, by the stress sensitive part, the mass body portion, voltage dependent resistor (VDR) and the detection chip (803) that bridge diagram constituted, the detection chip heart therein are the masses (804) of fine motion, are being symmetrically distributed to be used for bearing mass piece and responsive eight beams of beam (805) partly of conduct around mass; It is characterized in that: described voltage dependent resistor (VDR) is infused on the maximum stress point position and detection chip outward flange on every beam of detection chip for adopting phosphonium ion; Described voltage dependent resistor (VDR) is formed the bridge diagram of measured X, Y, three directional accelerations of Z respectively, wherein:

R1=R2=R3=R4=R5=R6=R7=R8=R12=R13=R, R9=R10=R11=4R and R9, R10, R11, R12, R13 are the fixed resistance on the detection chip outward flange;

The voltage dependent resistor (VDR) of detection chip be connected electric bridge low-resistance lead on the SiO2 protective seam is arranged.

2, the little piezoresistance type acceleration sensor of a kind of integrated silicon according to claim 1, it is characterized in that described mass is a positive water chestnut stage body, its four sides and bottom surface be the angle of promising α all, and the periphery sides of bearing strain beam is trapezoidal, the angle of medial surface and the promising β in bottom surface.

3, the manufacturing job operation of the little resistance-type acceleration transducer of a kind of integrated silicon according to claim 2 is characterized in that described detection chip process for making is:

(1), be equipped with sheet, select the special-purpose double-polished chip of P type (100) micromechanics for use;

(2), once oxidation, generate the SiO2 protective seam

(3), photoetching, the low-resistance wire pattern;

(4), phosphorous diffusion, the low-resistance lead;

(5), secondary oxidation, generate the SiO2 protective seam;

(6), positive photoetching, form resistance pattern;

(7), phosphonium ion injects formation N type voltage dependent resistor (VDR);

(8), annealing, eliminate defective, make crystal obtain electric conductivity;

(9), three oxidations, generate the SiO2 protective seam;

(10), back side photoetching, form back side mass activity surplus figure;

(11), the EPW anisotropic etch, erode away mass;

(12), positive photoetching, form the figure of beam;

(13), positive RIE corrosion, dry etching goes out beam, the reactive ion etching of free radical vertical incidence;

(14), four oxidations, generate the SiO2 protective seam;

(15), positive photoetching, form the window that is connected of low-resistance silicon and metal level;

(16), positive photoetching, form the plain conductor layer pattern;

(17), evaporation TiPtAu, form metal carbonyl conducting layer, can anti-EPW mordant;

(18), back side photoetching, carve the figure of mass, comprise convex corner compensation;

(19), the EPW anisotropic etch, erode away the shape of mass.

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