CN1746681A

CN1746681A - Differential anti-high overload micro-tunnel accelerometer and its preparation method

Info

Publication number: CN1746681A
Application number: CN 200410009521
Authority: CN
Inventors: 董海峰; 郝一龙; 贾玉斌; 沈三民; 张文栋
Original assignee: Peking University
Current assignee: Peking University
Priority date: 2004-09-08
Filing date: 2004-09-08
Publication date: 2006-03-15
Anticipated expiration: 2024-09-08
Also published as: CN100383531C

Abstract

An antioverload micro tunnel accelerometer of differential type is prepared as setting electrical signal connection lead on glass substrate, connecting glass substrate with fixed comb electrode and tunnel top through anchor point and support beam, connecting support beam with mass block and movable comb electrode, and applying symmetric structure as sensing structure assisted with differential feedback control circuit. Its preparing method includes positive electrode interlinking technique, conductive coupling plasma etching process and focusing ion beam process.

Description

Miniature tunneling accelerometer of differential type anti high overload and preparation method thereof

Technical field

The invention belongs to the microelectromechanical systems manufacture field, relate in particular to structure of the miniature tunneling accelerometer of a kind of differential type anti high overload and preparation method thereof.

Background technology

Microelectromechanical systems (MEMS) adopts advanced semiconductor process techniques as emerging high-technology field, and whole physical construction is integrated in the chip piece, has obtained using widely in military, biomedical, automobile and other industries.These devices mainly are that various structures are processed on the basis with silicon materials.In recent years, microfabrication means such as dry method deep etching technology, focused ion beam technology ripe gradually is the development high precision, the MEMS device of the new principle tachnical storage that provides the foundation.

Tunneling accelerometer is based on the new device of quantum tunneling effect, people such as U.S. scientist G.Binnig H.Rohrer in 1986 are because of design and developed flying-spot microscope based on quantum tunneling effect and obtain after the Nobel Prize in physics, and many scientists study in the application of other field quantum tunneling effect.Carry out aspect the development of tunnel type accelerometer utilizing the MEMS technology, people (Cheng-Hsien Liu andThomas W.Kenny A high-precision such as the Thoms W.Kenny of Stanford University, wide-bandwith micromachinedtunneling accelerometr, Journal of Microelectromechenical Systems, vol.10, No.3, September 2001 pp425-433) and people (Chingwen Yeh and Khalil Najafi such as the KhalilNajafi of U.S. University of Michigan, A Low-VoltageTunneling-Based Silicon Microaccelerometer IEEE TRANSACTIONSON ELECTRON DEVICES, VOL.44, NO.11, NOVEMBER 1997pp1875-1882) tunneling accelerometer has been done big quantity research, prepared tunneling accelerometer with certain performance.But also find that tunnel type sensor low-frequency noise and drift are bigger simultaneously, this has just limited its range of application, Differential Detection is the method for a kind of good restraining drift and noise, but because tunneling accelerometer needs the distance of feedback circuit control tunnel point and counter electrode, the realization Differential Detection need be processed tunnel point, electrode and lead-in wire at tow sides, adopts present structure and technology to be difficult to realize.

Summary of the invention

The purpose of this invention is to provide a kind of differential type tunneling accelerometer, specifically disclose the structure of this differential type tunneling accelerometer, the characteristics that this accelerometer has microminiaturization, precision height, can produce in batches.

Another object of the present invention provides the preparation method of described differential type tunneling accelerometer.

Technical scheme of the present invention is as follows:

A kind of differential type anti high overload tunneling accelerometer comprises glass substrate, and the glass substrate power on signal connects lead-in wire, and glass substrate is by anchor point (anchor) and brace summer, and the fixed fingers electrode is connected with the tunnel point.Brace summer links to each other with mass, movable comb electrodes.Be characterized in that sensitive structure is a symmetrical structure, be aided with the differential type feedback control circuit, realized the differential type tunneling accelerometer; The elasticity that is connected between tunnel point and the glass substrate is connected rather than is rigidly connected, and this structure has improved the anti high overload ability of device; On the preparation method, designed complete differential type tunneling accelerometer preparation method, wherein mainly comprise anode linkage, inductively coupled plasma etching technology (ICP) and focused ion beam technology technologies such as (FIB).

Differential type anti high overload tunneling accelerometer of the present invention utilizes the feedback control circuit self-adaptation to regulate driving voltage, and the distance of tunnel point and counter electrode is remained about 1nm, reads the size of input acceleration by the variation of feedback voltage.The present invention has not only realized the symmetry of sensitive structure, and in feedback control circuit, adopt single bleeder circuit scheme that differential configuration is driven and setover, adopt the symmetric circuit scheme to carry out filtering and feedback, thereby suppressed noise and drift, improved the precision of tunneling accelerometer.

The preparation method of differential type anti high overload tunneling accelerometer may further comprise the steps successively:

1. parent material is a silicon chip, etching shallow slot on silicon chip so that in last etching releasing structure.Lithographic method can adopt potassium hydroxide (KOH) etching process, also can adopt other catechol ethylene diamines (EDP), tetramethyl ammonium hydroxide (TMAH) to wait other caustic solutions.

2. preparation drive electrode and tunnel point counter electrode on glass substrate at first erodes away latent groove on glass substrate, and depositing metal in the groove of diving then is with bonding quality and the electrical connection that realizes.

3. anode linkage is realized glass substrate and silicon pad alignment and bonding.

4. adopt the inductively coupled plasma etching technology etching silicon chip back side, obtain the differential type sensitive structure, comprise mass, fixed fingers, movable broach, brace summer and elasticity tunnel point are not worn but do not carve, about surplus 9-11 μ m.

5. the employing focused ion beam technology etches the step of deposit tunnel point on silicon structure, and then depositing metal platinum tunnel point.

6. adopt the inductively coupled plasma etching technology etching silicon chip back side once more, carve and wear silicon chip, releasing structure is promptly finished the processing of described tunneling accelerometer.

Advantage of the present invention and good effect:

Differential type anti high overload tunneling accelerometer of the present invention owing to designed the sensitive structure of differential type, is aided with the feedback control circuit of differential type simultaneously, thereby can reduces the noise and the drift of device significantly, improves the performance of device, expands its range of application.The present invention has designed elasticity tunnel point structure, has improved the anti-overloading performance of tunneling accelerometer under the situation that does not influence the device dynamic response characteristic effectively, has further widened the application of tunneling accelerometer.

The preparation method that the present invention adopts adopts conventional MEMS (micro electro mechanical system) (MEMS) process equipment and advanced focused ion beam technology, can realize manufacturing in enormous quantities, has realized the microminiaturization of tunneling accelerometer simultaneously.Among the preparation method, on silicon chip, etch structure earlier, but do not discharge, carry out focused-ion-beam lithography and deposit again, so just avoided because the imaging drift that electric conductivity causes is difficult to carry out pinpoint problem.Adopting another benefit of focused ion beam technology is to have overcome the problem that conventional depositing technics is difficult to realize big isolation resistance.

Description of drawings

Below in conjunction with accompanying drawing the present invention is illustrated in further detail:

Fig. 1 is the structural representation of tunneling accelerometer of the present invention.

Fig. 2 is the elasticity tunnel point structural representation of tunneling accelerometer of the present invention.

Fig. 3 is the feedback control circuit schematic diagram of tunneling accelerometer of the present invention.

Fig. 4 (a)～Fig. 4 (g) shows the main preparation process of tunneling accelerometer of the present invention.

Among the figure:

The 1-glass substrate, 2-fixed fingers electrode, 3-tunnel point, 4,4 ', 4 " the bonding anchor point, 5-detects mass, 6-brace summer, 7-movable comb electrodes, 8-electrical lead, 9-pressure welding electrode, 10-elastic beam, 11-silicon substrate

Most preferred embodiment is described in detail

Below with reference to accompanying drawing of the present invention, more detailed description goes out most preferred embodiment of the present invention.

Embodiment 1: differential type tunneling accelerometer structure

As shown in Figure 1, be the synoptic diagram of differential type tunneling accelerometer.Comprise glass substrate 1, electric connecting wire 8 and pressure welding electrode 9 are arranged on the glass substrate 1, be Ti/Pt/Au three-decker or Cr/Au double-decker etc., glass substrate 1 is fixedlyed connected with brace summer 6 by bonding anchor point 4, detecting mass 5 fixedlys connected with brace summer 6, movable electrode 7 is fixedlyed connected with mass 6, and movable electrode 7 is realized being electrically connected with corresponding corresponding pressure welding electrode 9 by mass 5, brace summer 6, bonding anchor point 4, adjacent electric connecting wire 8.

Fixed electorde 2 is by bonding anchor point 4 " fixedlys connected with glass substrate; realize being electrically connected with corresponding pressure welding electrode 9 by adjacent electric connecting wire 8 simultaneously; fixed electorde 2 is two counter electrodes that realization drives with movable electrode 7, can be plate electrode, also can be comb electrodes.

Tunnel point 3 is positioned at the structure centre, and tunnel point 3 comprises symmetrical two tunnel points.Tunnel point is by bonding anchor point 4 ' fixedly connected with glass substrate, simultaneously by adjacent electric connecting wire 8 and corresponding pressure welding electrode 9 realization electrical connections.

The total left-right symmetric.

Figure 2 shows that the elasticity tunnel point structural representation of tunneling accelerometer of the present invention, the tunnel point can be elasticity tunnel point.

Embodiment 2: differential type tunneling accelerometer testing circuit

As shown in Figure 3, be differential type tunneling accelerometer testing circuit schematic diagram, the current potential of two tunnel points is identical among the figure, an and shared cover biasing and a benchmark bleeder circuit, by resistance R 1, R2, R3, Vcc, provide, the voltage that wherein connects the tunnel point is bias voltage, adjust R1, R2, R3 makes it equal 100mV, electric current under the assurance duty between tunnel point and the counter electrode is a tunnel current, adjust R1, R2, R3 makes reference voltage equal 10mV, be used for follow-up comparator circuit, the effect of R8 is that tunnel current is converted to tunnel voltage, also can adopt the current-voltage conversion chip to realize, tunnel voltage and reference voltage pass through A1, after the A1 ' comparison, by R4, C2, A2, R4 ', C2 ', the symmetric circuit of A2 ' composition carries out filtering and follows processing, enter the FEEDBACK CONTROL link afterwards, by resistance R 5, R6, R7, R5 ', R6 ', R7 ', Vcc, ground is formed, also adopt the circuit of symmetry fully, corresponding with symmetrical sensitive structure, the feedback control circuit of this differential type has suppressed the noise and the drift that produce in the circuit, because the symmetry of structure, thereby also suppressed the noise and the drift that produce on the structure simultaneously.Be output as the difference of two symmetrical sensing units, the remolding sensitivity individual unit is doubled.

The preparation method of differential type tunneling accelerometer

Figure 4 shows that the preparation technology of differential type tunneling accelerometer.

1. parent material is two N type (100) silicon chips 9 of throwing, and thickness is 400 ± 10 microns, resistivity 2～4 Ω cm;

The groove 2.KOH corrosion is dived, concentration 30%, 80 ℃ of temperature, the activity space of preparation structure, thickness is 3～4 μ m, shown in Fig. 4 (a);

3. prepare electrical lead and pressure welding electrode, at first at the latent groove with dark 1000 of HF solution corrosion on glass, deposit photoresist then, after adopting same mask to carry out photoetching, development, adopt sputtering technology deposit Ti/Pt/Au (thickness is 400 /300 /900 ), adopt the ultrasonic technology of acetone to peel off at last, on glass substrate 1, prepare electrical lead and pressure welding electrode, comprise tunnel point electrode, mass 1 connection electrode, mass 2 connection electrode, fixed electorde 1, fixed electorde 2, shown in Fig. 4 (b);

4. anode linkage, at first in double-sided alignment litho machine (model: last aligning KarlSuss MA6/BA6) with glass substrate substrate 1 and silicon chip 9, then in bonding machine (model: carry out anode linkage KSSB6), 380 ℃ of bonding temperatures, bonding voltage 1500V, the normal pressure bonding is shown in Fig. 4 (c);

5. inductively coupled plasma etching technology for the first time, control etching time and passivation time were respectively 7 seconds/9 seconds, and air pressure is less than 150 milli torrs, generate the basic structure of mass, brace summer and tunnel point, it is vertical that its sidewall keeps, and do not carve and wear, stay surplus thick 9-11 μ m, shown in Fig. 4 (d);

6. focused particle beam technology etches the step of deposit tunnel point, shown in Fig. 4 (e);

7. focused particle beam technology generates Pt tunnel point, shown in Fig. 4 (f);

8. inductively coupled plasma etching technology for the second time, control etching time and passivation time were respectively 8 seconds/9 seconds, and air pressure is less than 150 milli torrs, and releasing structure is shown in Fig. 4 (g);

9. sliver is finished the processing of tunneling accelerometer.

The differential type anti high overload tunneling accelerometer that preceding method makes, its middle and lower part is a glass substrate 1, and top is silicon structure, is positioned at mass 5 brace summer 6 all around by eight and supports, and tunnel point 3 is positioned at the centre of total, is symmetrical two tunnel points.Tunnel point 3 is round, adopts the deposit of focused particle beam technology to form.The initial distance of tunnel point 3 between the corresponding mass piece by the first time inductively coupled plasma etching and focused ion beam depositing technics control; Brace summer 6 and mass 5 all obtain by the deep erosion of dry method, adopt inductively coupled plasma etching technology and focused particle beam technology, obtain differential type tunneling accelerometer structure, the feedback control circuit that is aided with differential type, reduce the noise and the drift of tunneling accelerometer significantly, improved the precision of device.

Although disclose most preferred embodiment of the present invention and accompanying drawing for the purpose of illustration, it will be appreciated by those skilled in the art that: without departing from the spirit and scope of the invention and the appended claims, various replacements, variation and modification all are possible.Therefore, the present invention should not be limited to most preferred embodiment and the disclosed content of accompanying drawing.

Claims

1. A differential anti-high overload micro-tunnel accelerometer, comprising a glass substrate, and an electric signal connection lead on the glass substrate, is characterized in that:

Adopt anti-high overload differential sensitive structure and differential feedback control circuit;

The differential sensitive structure includes mass blocks, fixed combs, movable combs, support beams and elastic tunnel tips, electrical connection leads and welding electrodes;

The glass substrate is connected to the support beam, the fixed comb electrode and the tunnel tip through the anchor point, and the support beam is connected to the proof mass and the movable comb electrode;

The tunnel tip is located in the center of the structure, and the tunnel tip includes two symmetrical tunnel tips;

The connection between the tunnel tip and the glass substrate is an elastic connection rather than a rigid connection;

The differential feedback control circuit includes a common bias and reference circuit, a symmetrical filter and feedback circuit.

2. The differential anti-high overload micro-tunnel accelerometer according to claim 1, characterized in that: the tunnel tip can be an elastic tunnel tip.

3. The differential anti-high overload micro-tunnel accelerometer according to claim 1, characterized in that: the potentials of the two tunnel tips are identical, and share a set of bias and reference voltage divider circuits, while comparison, filtering and feedback The circuit is realized with a completely symmetrical circuit.

4. The differential anti-high overload micro-tunnel accelerometer according to claim 1, characterized in that: the output is the difference of two symmetrical sensitive units.

5. A preparation method of a differential anti-high overload micro-tunnel accelerometer, specifically comprising the following steps:

(1) The starting material is a silicon wafer, and shallow grooves are etched on the silicon wafer to release the structure in the final etching;

(2) Prepare the driving electrode and the corresponding electrode of the tunnel tip on the glass substrate;

(3) Anode bonding to achieve alignment and bonding of glass substrates and silicon wafers;

(4) Use inductively coupled plasma etching technology to etch the back of the silicon wafer to obtain a differential sensitive structure, including mass blocks, fixed comb teeth, movable comb teeth, support beams and elastic tunnel tips, but not through;

(5) Using focused ion beam technology to generate a metal platinum tip on the top of the tunnel tip;

(6) Etching the back side of the silicon wafer by inductively coupled plasma etching technology again, carving through the silicon wafer, and releasing the structure.

6. The preparation method of the differential anti-high overload micro-tunnel accelerometer according to claim 5, characterized in that: when using inductively coupled plasma etching technology to etch the back of the silicon wafer, it does not cut through, and the remaining 9-11um, Then the tunnel tip is prepared by the focused particle beam process, and then the structure is released by the inductively coupled plasma etching process to obtain the differential tunnel accelerometer structure.