The background technology obliquity sensor is a kind of sensor that is used for attitude monitoring and control, has very widely at various military affairs such as the land of satellite, guided missile, tank, cannon, aircraft, automobile, naval vessel, geology oil exploration, construction, robot and underwater operation and civil area and uses.Traditional obliquity sensor has bubble formula, liquid pendulum-type, condenser type, inductance type, potentiometer formula, gas pendulum etc., and the angle that mostly can only detect one dimension changes, and size is bigger, is not suitable for the field that volume and weight is had certain limitation.In realizing the obliquity sensor that the detection two dimension angular changes, structures such as gas pendulum, twin axle, magnetic fluid formula have been adopted mostly.Recently by patent office searching's centre retrieves to patent-related document: utility model patent " a kind of optoelectronic angle sensor " Granted publication that Shanghai Xue Shui in 2004 very applies for is CN 2752725Y.This patent is a kind of sensor of photoelectric measurement corner, utilizes the swing of cam-shaped grating wheel, changes the luminous flux of silion cell, is not the relevant patent of utilizing silicon micro mechanical technology for detection inclination angle.
Retrieve U.Mescheder by the retrieval non-patent literature, S.Majer is published in the document " Micromechanical inclinometer " of " Sensors andActuators " A60 (1997) magazine, a kind of silicon micro mechanical twin shaft mass obliquity sensor is proposed in the document, be infused on the silicon beam by ion and make piezo-resistance, form electric bridge, measure the inclination angle of both direction.But its complex manufacturing technology with KOH body lithographic technique, needs convex corner compensation, and practical structures and design size are had than mistake.The KOH corrosion has an inclination angle, and the volume that this has reduced mass greatly reduces sensitivity, and sensor array density is restricted.Need carry out dense boron and dense phosphonium ion respectively and inject, make piezo-resistance be difficult to accurate control, skewness, bridge circuit is unbalance.
Summary of the invention the objective of the invention is to develop a kind of new, volume is little, array density height, energy measurement both direction inclination angle, the simple high sensitivity silicon micro mechanical of manufacture craft bidimensional obliquity sensor chip and preparation method simultaneously.
Technical scheme of the present invention is: a kind of silicon micro mechanical bidimensional obliquity sensor, described sensor comprise Pyrex substrate, electrode, butterfly mass, peripheral frame, silicon strain beam L1, L2, L3, L4; Piezo-resistance R1, R2, R3, R4, R5, R6, R7, R8, particularly: described Sensor core is by a movable butterfly mass, become four silicon strain beam L1 of " ten " font structure, L2, L3, L4 constitutes, described strain beam L1, L2, L3, L4 connects butterfly mass and peripheral frame, described Pyrex substrate is fixedlyed connected by sealing technology with peripheral frame, the degree of depth with Pyrex substrate depression of overload position limitation protection function should be greater than the deflection of silicon strain beam, sensor is when heeling condition, described butterfly mass makes silicon strain beam L1 under the gravity effect, L2, L3, L4 produces stress; The thickness of described butterfly mass is identical with the thickness of peripheral frame, equals the thickness of silicon chip, is 300~600 microns; Described piezo-resistance R1, R2 are arranged in the two ends of silicon strain beam L1, and piezo-resistance R3, R4 are arranged in the two ends of silicon strain beam L2, and piezo-resistance R5, R6 are arranged in the two ends of silicon strain beam L3, and piezo-resistance R7, R8 are arranged in the two ends of silicon strain beam L4; When sensor perturbations, the silicon strain beam produces stress changes piezo-resistance resistance; Piezo-resistance R1, R2, R3, R4 form a full-bridge circuit, detect around the inclination angle of Y direction, and piezo-resistance R5, R6, R7, R8 form another full-bridge circuit, detect the inclination angle around directions X.
The consistent size of described each silicon strain beam, its thickness are 5~20 microns, and length is 500~2000 microns, and width is 50~300 microns; The feature of described Pyrex substrate is that its thermal coefficient of expansion and silicon are approaching; Described electrode is electrically connected with piezo-resistance respectively, and the signal of telecommunication is passed to peripheral circuit, and its number of poles is determined as the case may be.
As a further improvement of existing technologies, it is square that the shape of described butterfly mass is not restricted to each angle, and its shape facility is fully to be full of the peripheral frame volume inside.
A kind of preparation method of silicon micro mechanical bidimensional obliquity sensor comprises thermal oxide, photoetching, the injection of boron ion, inductively coupled plasma dry etching, Pyrex wet etching, electrostatic sealing-in, wire bonds, chip encapsulation, particularly:
Described induction lotus root is closed the plasma dry lithographic technique silicon chip is carried out the thickness that positive etching is determined silicon strain beam L1, L2, L3, L4, and close plasma dry with reverse side induction lotus root and discharge silicon strain beam L1, L2, L3, L4 and make it to separate with peripheral frame with the butterfly mass, the steps include:
1. silicon chip cleans and two-sided thermal oxide;
2. the positive photoetching of silicon chip and erode away eight sensitive resistance district windows on silicon strain beam L1, L2, L3, the L4;
3. positive ion for the first time injects and forms resistance area;
4. positive even glue also makes the resistance head window by lithography;
5. photoresist carries out the ion injection second time to form ohmic contact regions as mask;
6. make mask with oxide layer, positive photoetching also etches the fairlead window and front silicon strain beam L1, L2, L3, L4 window;
7. two-sided evaporation plating;
8. back side photoetching and etch silicon strain beam L1, L2, L3, L4 and peripheral frame window;
9. positive photoetching also etches metal lead wire and electrode;
10. alloying is finished Ohmic contact;
11. positive induction lotus root is closed plasma dry and etches silicon strain beam L1, L2, L3, L4 structure, and control thickness;
12. back side induction lotus root is closed plasma dry and etches the gap, releasing structure;
13. carry out the static encapsulation with glass substrate;
14. the gold ball bonding lead-in wire also carries out outer package.
The invention has the beneficial effects as follows: with respect to proposing a kind of silicon micro mechanical twin shaft mass obliquity sensor in the prior art, be infused on the silicon beam by ion and make piezo-resistance, form electric bridge, measure the inclination angle of both direction.Its weak point is its complex manufacturing technology, with KOH body lithographic technique one inclination angle is arranged, reduced the volume of mass, sensitivity is reduced, sensor array density is restricted, and need carry out dense boron and dense phosphonium ion respectively and inject, and makes piezo-resistance be difficult to accurate control, cause the residual stress of silicon beam big, increase non-linear.
Sensor of the present invention is by four silicon strain beams of a movable butterfly mass, one-tenth " ten " font structure and the Pyrex substrate formation with overload position limitation protection function.This sensor chip can detect simultaneously around the inclination angle of X and Y both direction and change.Each monocrystalline silicon strain beam is arranged two piezoresistance sensitivity resistance at sensitive position, and four sensitive resistances on corresponding two beams constitute full-bridge output, detects the inclination angle and changes.This shows silicon micro mechanical bidimensional obliquity sensor of the present invention, simple in structure, volume is little, array density is high, energy measurement both direction inclination angle, the simple high sensitivity silicon micro mechanical of manufacture craft bidimensional obliquity sensor chip simultaneously.Its preparation method adopts induction lotus root to close the plasma dry etching, can increase the mass volume effectively and improve sensitivity and accurate control strain beam thickness, improves the array density of sensor chip, is beneficial to improve yield rate and reduce cost.Adopt the even doping of ion implantation technology simultaneously to the piezo-resistance district, implantation dosage is accurately controlled, the high conformity of piezo-resistance, and it is more shallow that ion injects the resistance area junction depth that forms, piezo-resistance just can make full use of the maximum strain top layer like this, therefore has higher sensitivity.
The specific embodiment
Below in conjunction with accompanying drawing embodiments of the invention are further explained:
Fig. 1 is a silicon micro mechanical bidimensional obliquity sensor chip structure schematic diagram; Among Fig. 1,1 is the Pyrex substrate, and 2 is electrode, and 3 is the butterfly mass, and 4 is peripheral frame.
Silicon micro mechanical bidimensional obliquity sensor core is made of a movable butterfly mass 3, four silicon strain beam L1 that become " ten " font structure, L2, L3, L4; the silicon strain beam connects butterfly mass 3 and peripheral frame 4; Pyrex substrate 1 and peripheral frame 4 are fixed by sealing technology, and the degree of depth with Pyrex substrate 1 depression of overload position limitation protection function should be greater than the maximum deformation quantity of strain beam.
The thickness of butterfly mass 3 is identical with the thickness of peripheral frame 4, equals the thickness of silicon chip, is 300~600 microns.Butterfly mass 3 to be shaped as four angles be square, with 50~100 microns of peripheral frame 4 distances.
Piezo-resistance R1, R2 are arranged in the two ends of silicon strain beam L1, and piezo-resistance R3, R4 are arranged in the two ends of silicon strain beam L2, and piezo-resistance R5, R6 are arranged in the two ends of silicon strain beam L3, and piezo-resistance R7, R8 are arranged in the two ends of silicon strain beam L4.Piezo-resistance R1, R2, R3, R4 form a full-bridge circuit, and piezo-resistance R5, R6, R7, R8 form another full-bridge circuit, and each resistance size is the same, is 1~10 kilohm.
The size of each silicon strain beam is in full accord, and its thickness is 5~20 microns, and length is 500~2000 microns, and width is 50~300 microns.
Pyrex substrate 1 thermal coefficient of expansion is 2.2~2.5 * 10
-6/ K.
Fig. 2 is a silicon micro mechanical bidimensional obliquity sensor chip manufacture method flow chart.In Fig. 2, silicon micro mechanical bidimensional obliquity sensor is made flow process and is:
At first the silicon chip at butterfly mass 3 and peripheral frame 4 places cleans and two-sided thermal oxide (step 100); Positive then photoetching also erodes away eight sensitive resistance district windows on silicon strain beam L1, L2, L3, the L4, and ion injects the formation resistance area for the first time, positive even glue and be that mask lithography goes out the resistance head window with the photoresist carries out second time ion and injects with formation ohmic contact regions (step 110); Follow two-sided thermal oxide and make mask with oxide layer, positive photoetching also etches the fairlead window and front silicon strain beam L1, L2, L3, L4 window, two-sided evaporation plating aluminium (step 120); Back side photoetching then also etches silicon strain beam L1, L2, L3, L4 and peripheral frame 4 windows, and positive photoetching also etches aluminum lead and electrode 2, and alloying is finished Ohmic contact (step 130); Positive induction lotus root is closed plasma dry and etches silicon strain beam L1, L2, L3, L4 structure, and control thickness (step 140); Back side induction lotus root is closed plasma dry and etches the gap, releasing structure (step 150); Last sensitive structure and glass substrate are carried out static encapsulation (step 160); The gold ball bonding lead-in wire also carries out outer package (step 170).
Obviously, those skilled in the art can carry out various changes and modification to silicon micro mechanical bidimensional obliquity sensor chip of the present invention and preparation method and not break away from the spirit and scope of the present invention.Like this, if of the present invention these are revised and modification belongs within the scope of claim of the present invention and equivalent technologies thereof, then the present invention also is intended to comprise these changes and modification interior.