CN1138147C - Microacceleration silicon sensor with overload protection and cable of being stuck to curved surface and its manufacture - Google Patents

Abstract

The present invention relates to a silicon micro-acceleration sensor and a fabrication method thereof for curved surface bonding overload protection, which belongs to the technical field of silicon micromechanical sensors. The silicon micro-acceleration sensor has the structural characteristics that two curved surfaces on both sides of a cantilever beam are used for the overload protection of the cantilever beam; the curved surfaces are designed according to a flexing function of the cantilever beam; the whole silicon micro-acceleration sensor is in an integral structure of single chip silicon, and thus, an overload protection cover plate does not need sealing additionally. The fabrication of the silicon micro-acceleration sensor is characterized in that an N doped (100) silicon chip micromechanical processing technology is used; when the transversal cantilever beam is processed by deep reactive ion etching, both sides of the cantilever beam are processed out with overload protection curved surfaces which conform to beam flexure expressed by the flexing function. The present invention has the characteristics of simple structure, artful design, small sensor volume and convenient fabrication, which is suitable for acceleration sensors having high ranges (from 10000 to 100000g), and has wide application prospect.

Description

The silicon micro-acceleration sensor of application of a surface overload protection and manufacture method

Technical field

The present invention relates to a kind of suitable high range (10,000～100,000 g) acceleration transducer and manufacture method, the anti-high impact overload of this class silicon micro-acceleration sensor is to adopt the method for application of a surface formula passive protection and measure to implement more precisely.Belong to the silicon micro mechanical sensor technical field, also belong to the inertia measurement sensor technical field.

Background technology

Increasingly mature along with silicon micro-machining technology, silicon micro mechanical acceleration transducer be because its price is low, precision is high, be suitable for producing in batches, and be widely used in the monitoring of all kinds of motion processes.Wherein measured sensor is all having the typical case and important use aspect the military and civilian two under the high g range carrying out under the HI high impact environment.The detection core component of such sensor is silicon cantilever mechanics sensitive structure and the electric sensor spares such as pressure drag of constructing on it.In the sensor measurement process, the high impact overload situation appears through regular meeting, and therefore need to adopt overload protection method and measure to come protection device to avoid damaging.Existing overcurrent protection structure generally is to adopt to be positioned at semi-girder one side (or both sides) and to add the method that protruding point [seeing Fig. 1 (a)] or each parallel plane [seeing Fig. 1 (b)] of two sides stop the overload motion, the deflection scope of constraint semi-girder under overload situations.When semi-girder under overload situations; its barycenter or top form point with projection or protection plane and contact; cantilever beam structure is a bit supported by original root become 2 supportings; thereby improved semi-girder under the overload situations load-bearing capacity and avoid fractureing, this is the main method of semi-girder overload protection up to the present.For example, [1] H.Chen, S.Shen; M.Bao, Overrange capacity of apiezoresistive microaccelerometer, Sensors and Actuators; A58,1997, pp.197-201.[2] A.Partridge; J.Reynolds; B.Chui, E.Chow, A.Fitagerald; L.Zhang; N.Maluf, T.Kenny, A high performance planar piezoresistive accelerometer; Journal ofMicroelectromechanical Systems; Vol.9, No.1,2000; pp.58-66. in their described micro-acceleration device, all adopt this overload protection method.Yet the method for this overload protection has its certain limitation, particularly bears greater impact when overload when semi-girder, and all the other overhanging portions except that 2 supportings still can move and cause the damage of beam.So the anti-high impact overload protective capability of existing single-point guard method is still not enough, particularly in high measurement scope acceleration transducer, uses and to meet the demands.

Summary of the invention

The purpose of this invention is to provide a kind of more effective overcurrent protection structure and implementation method, to overcome the deficiency that existing semi-girder overcurrent protection structure exists.It is conceived design substantially and makes a kind of novel curved surface overcurrent protection structure, makes micro-machine acceleration transducer when bearing the greater impact overload, still can provide better protect to micro-machine acceleration transducer.

Ultimate principle of the present invention is as follows: Fig. 2 is acceleration transducer semi-girder overload curved surface protection philosophy schematic top view.According to the semi-girder mechanical analysis, the square equal cross-section semi-girder that is respectively L and w when length and thickness is under the effect of acceleration a during to a side deflection.Its flexural function is: $f\left(x\right)=\frac{\mathrm{\ρ}\stackrel{\→}{a}}{2w^{2}E}{x}^2(x^2-4\mathrm{Lx}+{6L}^2)$ Wherein f (x) the deflection displacement of ordering for coordinate x, density, the E that ρ is silicon are the young modulus of silicon.Illustrate that its deflection displacement of place of different x points is different on the semi-girder, and be complicated funtcional relationship.For improving the ability of overload protection, changing existing single-point contact protection is the protection that curved surface is fitted everywhere.In other words, the overload protection curved surface also makes the curve same with the beam deflection, and after the deflection of beam reaches overload level, will fit with the protection side naturally substantially fully in the whole side of beam.Nearly all part all no longer further increases deflection on whole beam under bigger impact or the overload, thereby the overload protection effect is improved greatly than existing single-point protection.

For further specifying substantive distinguishing features of the present invention and marked improvement, use Fig. 3 sets forth in detail.Fig. 3 has shown the perspective, cut-away view of the high g value acceleration transducer with anti high overload impact that adopts this overload protection invention.The protection curved surface 4 that it is impacted by silicon frame 1, boron diffusion piezoresistance sensitivity resistance area 2, semi-girder 3 and anti high overload etc. is partly formed, and its protection curved surface is positioned at two sides up and down of semi-girder 3.Its principle of work is: when pedestal bears acceleration, and the semi-girder transverse curvature, because piezoresistive effect, the resistivity in boron diffusion district changes, and realizes output after Wheatstone bridge connects.When to the certain voltage of electric bridge input, the variation of output voltage and acceleration be varied to direct ratio, so measure the variation that the Changing Pattern of output voltage just can record acceleration.

Acceleration transducer of the present invention can make the making of responsive semi-girder and overcurrent protection structure utilize DRIE to finish simultaneously jointly, thereby guarantees to finish the precision that body plan is made.That is when utilizing advanced deep reaction ion etching (DRIE) cross machine deflection semi-girder, process the overload protection curved surface identical in its both sides with the beam deflection of front equation expression.The shape of this curved surface is made by photo mask board and the precision of DRIE technology decides.And the precision of the integrated processing of this respect is very high exactly, guarantees like this can be properly fit onto substantially when beam transships on the protection curved surface on opposite, therefore reaches the target that improves device overload capacity.

Entire device utilizes the micromachining technology of N type doping (100) silicon chip to implement.Owing to adopted advanced technologies such as DRIE, be suitable for producing in batches.The processing step of its making is briefly described as follows:

(1) with silicon chip back side anisotropic etch to certain thickness, its one-tenth-value thickness 1/10 equals semi-girder design width.

(2) light boron diffusion forms the sensitive resistance with piezoresistive effect, and its square resistance is in 100-250 ohm scope.

(3) dense boron diffusion makes the two ends in variable resistor district and the metal lead wire of outside form Ohmic contact; The square resistance of contact is in 10-20 ohm scope.

(4) etch fairlead at ohmic contact regions.

(5) silicon chip upper surface deposition film aluminium and be carved into the lead-in wire and pad.

(6) adopt deep reaction ion etching technology to process the thickness and the overload protection curved-surface structure of semi-girder simultaneously, this curved surface carries out Design and Machining by above-mentioned flexural function.Utilize the mask plate that computer graphical generates and laser beam is processed to make DRIE etching pattern by lithography, utilize photoresist, accurately form semi-girder and curved surface protection structure simultaneously as etch mask material.

In sum, advantage of the present invention is:

(1) in Fig. 2, the overload protection of semi-girder adopts two curved surfaces that are positioned at the semi-girder both sides, and the amount of deflection curved surface of beam matched when this toroidal function and semi-girder bore maximum overload.When semi-girder bears bigger overload; semi-girder forms integral body with the protection curved surface and contacts closely; 2 supportings with respect to traditional employing single-point guard method; stress distribution on the semi-girder is more even; further improved the stressing conditions of beam under overload situations, can significantly improve under the high overload situation the protective capability of semi-girder and the reliability of device work.

(2) adopting the acceleration transducer of such overload structure is the monolithic construction of single piece of silicon, need not other sealing-in overload protection cover plate, therefore has simple in structure and the little advantage of volume, has also improved fabrication yield simultaneously and has reduced production cost.

(3) even there is defective in indivedual places when the protection Machining of Curved Surface, because of the face contact can not influence semi-girder yet and protect contacting between the curved surface, so the present invention is skillfully constructed, it is convenient to implement.

Description of drawings

Fig. 1 is existing two kinds of single-points contact overload protection structural representation.

(a) side adds the protection structure of protruding point

(b) each plane-parallel protection structure of two sides

Fig. 2 (a) is an application of a surface formula overload protection top view provided by the invention.

Fig. 2 (b) is the curved surface by the attaching type overload protection of flexural function calculating.

Fig. 3 is an application of a surface formula overload protection perspective, cut-away view provided by the invention.

Among the figure:

1-silicon frame, 2-boron diffusion sensitive resistance district

3-not stand under load front boom beams 3 '-stand under load back boom beam deflection shape

The protruding point of protection curved surface 5-overload protection that 4-anti high overload impacts

6-parallel plane W-semi-girder width

L-semi-girder length

The direction of-signal acceleration

Embodiment

Design example 1

The design range is the jerk acceleration transducer of 100,000 g, anti-overload 300,000 g.Through design, semi-girder length is 515 microns, and thickness is 16 microns, and width is 50 microns.Under 100,000 g acceleration effects, the amount of deflection of each point can be calculated by above-mentioned formula on the beam, and for example the terminal amount of deflection of beam is 5.5 microns etc.Two sensitive resistances are distributed in the beam root and lean on two side positions to experience the variation of stress, output electric signal after Wheatstone bridge connects.Implement on (100) silicon chip that N mixes during whole, sensor is the monolithic construction of single piece of silicon, need not other sealing-in overload protection plate.

Claims (3)

1. the silicon micro-acceleration sensor of an application of a surface overload protection comprises silicon frame (1), boron diffusion piezoresistance sensitivity resistance area (2), semi-girder (3), it is characterized in that:

A. the overload protection of semi-girder adopts two curved surfaces that are positioned at the semi-girder both sides; This curved surface is the flexural function by semi-girder $f\left(x\right)=\frac{\mathrm{\ρ}\stackrel{\→}{a}}{{2w}^{2}E}{x}^2(x^2-4\mathrm{Lx}+{6L}^2)$ Design, in the formula, the deflection displacement that f (x) is ordered for coordinate x, ρ be the density of silicon, young modulus, L that E is silicon be semi-girder length, W be the semi-girder width, Be acceleration;

B. silicon micro-acceleration sensor is the monolithic construction of single piece of silicon.

2. press the manufacture method of the silicon micro-acceleration sensor of the described application of a surface overload protection of claim 1; comprise and utilize N type doping (100) silicon chip micromachining technology; when it is characterized in that, process the identical overload protection curved surface of beam deflection of expressing in its two side with flexural function with deep reaction ion etching cross machine deflection semi-girder.

3. press the manufacture method of the silicon micro-acceleration sensor of the described application of a surface overload protection of claim 2, it is characterized in that concrete processing step is:

(1) with silicon chip back side anisotropic etch to certain thickness, its one-tenth-value thickness 1/10 equals semi-girder design width;

(2) light boron diffusion forms the sensitive resistance with piezoresistive effect, and its square resistance is in 100-250 ohm scope;

(3) dense boron diffusion makes the two ends in variable resistor district and the metal lead wire of outside form Ohmic contact; The square resistance of contact is in 10-20 ohm scope;

(4) etch fairlead at ohmic contact regions;

(5) silicon chip upper surface deposition film aluminium and be carved into the lead-in wire and pad;

(6) utilize the mask plate that computer graphical generates and laser beam is processed to make DRIE etching pattern by lithography, utilize photoresist, accurately form semi-girder and curved surface protection structure simultaneously as etch mask material.