A kind of digital differential relaying type micro-acceleration gauge
Technical field
The invention belongs to the digital accelerometer technical field of micromechanics electronics (mems) is and in particular to a kind of digital difference
Ejector half micro-acceleration gauge.
Background technology
Digital accelerometer does not need digital-to-analogue conversion link, can be directly embedded into digital processing system, have high precision,
Accordingly soon, the advantages of strong antijamming capability.Meanwhile, body is had using the micro- digital accelerometer of micromechanics electronic technology processing
Amass little, low cost and other advantages, just attracting increasing attention power.Digital micro-acceleration gauge has one micro- to shake in sensor
Dynamic element is used for sense accelerations, coordinates corresponding exciting circuit, and vibrating elementss are in resonant condition all the time.The shaking of vibrating elementss
Dynamic frequency is relevant with the axial force that it is subject to.By corresponding quality-spring converting system, acceleration is converted to vibrating elementss
The change of interior axial force, this axial force changes the frequency of vibration of vibrating elementss, then by corresponding circuit, this frequency is changed
Be converted to digital signal output, realize the digitized measurement of acceleration signal.
Two big component parts of digital slight accelerometer are mass-spring system and vibrating elementss.For quality-bullet
Spring system, can effectively reduce the size of sensor using the micro structure substituted metal structure being processed by silicon materials, tool
There are small volume, high precision, low cost and other advantages.In Chinese patent zl201210240759.8, a kind of entitled " silicon substrate four beam knot
In structure quartz resonance acceleration transducer chip ", by quartzy double-ended tuning fork be fixed on using silicon materials processing mass-
On spring system, mass-spring system is made up of the inertial mass that four beams support.Heat due to quartz and silicon bi-material
The coefficient of expansion is different, when the temperature varies, occurs that thermal stress leads to the output of sensor to produce temperature drift in quartz tuning-fork.
In order to solve this problem, in Chinese patent zl201210568654.5, the entitled " silicon substrate quartz with temperature isolation structure
It is proposed that a kind of impact to reduce temperature for temperature isolation structure in acceleration transducer ", but the temperature isolation knot being previously mentioned
Structure also reduces the sensitivity of sensor while effectively reducing temperature impact.
Content of the invention
In order to overcome the shortcoming of above-mentioned prior art, it is an object of the invention to provide a kind of micro- acceleration of digital differential relaying type
Degree meter, can eliminate the impact to sensor for the temperature, improve the nonlinearity of sensor, have fast response time, precision height etc.
Advantage.
To achieve these goals, the technical solution used in the present invention is:
A kind of digital differential relaying type micro-acceleration gauge chip, including the silicon base 1 with mass-spring function and two
Quartzy double-ended tuning fork 2-a, 2-b, silicon base 1 by mass 3 and supports two cantilever beams 4-a, 4-b of mass 3 to form,
Mass 3, the first cantilever beam 4-a and the second cantilever beam 4-b composition mass-spring system refer to along micro-acceleration gauge core
Piece sensitive direction sa, the first cantilever beam 4-a, the second cantilever beam 4-b have elastic characteristic, the first cantilever beam 4-a, the second cantilever beam
4-b is along the diagonal dc2 direction of mass 3;First quartzy double-ended tuning fork 2-a, the second quartzy double-ended tuning fork 2-b
Along other diagonal dc1 of mass 3, the first quartzy double-ended tuning fork 2-a, the second quartzy both-end stationary tone
Fork 2-b structure is identical, and quartzy double-ended tuning fork 2-a, 2-b are in differential fashion arrangement.
Described silicon base 1 adopts bulk silicon process, has positioning first quartz in silicon base 1 diagonal dc1
Double-ended tuning fork 2-a, four locating slots 6-a, 6-b, 6-c, 6-d of the second quartzy double-ended tuning fork 2-b, quartzy both-end is solid
Two fixing ends 7-a, 7-b of accordatura fork 2 are separately fixed in four locating slots 6-a, 6-b, 6-c, 6-d of silicon base 1.
Described quartzy double-ended tuning fork 2 is processed by quartz crystal, is coated with four sides on each prong of tuning fork
Electrode 8, is electrically connected to each other between electrode 8, during normal work, electrode 8 has alternating voltage, due to quartz crystal piezoelectricity and
Inverse piezoelectric effect, quartzy double-ended tuning fork 2 can be in the anti-phase vibration pattern in same plane.
In four described locating slots, the depth of 6-a, 6-b, 6-c, 6-d needs to ensure that quartzy double-ended tuning fork 2 is attached to
After in silicon base 1, it is in the centre position in silicon wafer thickness section 9.
The invention has the benefit that
Manufacture the silicon base of this accelerometer using the micro- technique of silicon, have small volume, high precision, can mass production etc. excellent
Point;Have the advantages that easy excitation, high quality factor, digital signal export using quartzy double-ended tuning fork as vibrating elementss,
Digital processing system can be directly embedded into;Meanwhile, quartzy double-ended tuning fork adopts differential fashion to arrange, can eliminate temperature
Impact;Two quartzy double-ended tuning forks of differential fashion arrangement design the diagonal positions of block of improving quality in silicon substrate, can subtract
The size of little micro-acceleration gauge chip.
Brief description
Fig. 1 is micro-acceleration gauge chip structure schematic diagram of the present invention.
Fig. 2 adopts the silicon substrate bottom structure of micro fabrication manufacture for the present invention.
The quartzy double-ended tuning fork schematic diagram that Fig. 3 adopts for the present invention, wherein Fig. 3-1 shows for quartz tuning-fork overall structure
It is intended to;Fig. 3-2 is distribution and the electrical connection diagram of quartz tuning-fork Top electrode.
Fig. 4 is the a-a schematic cross-section of Fig. 1.
Fig. 5 is connection diagram during micro-acceleration gauge chip operation with quartz resonance circuit.
Specific embodiment
Below in conjunction with accompanying drawing, the structure & working mechanism of the present invention is described in detail.
With reference to Fig. 1, a kind of digital differential relaying type micro-acceleration gauge chip, including the silicon substrate with mass-spring function
Bottom 1 and two quartzy double-ended tuning fork 2-a, 2-b, silicon base 1 is by two cantilever beam 4- of mass 3 and support mass 3
A, 4-b form, and mass 3, the first cantilever beam 4-a and the second cantilever beam 4-b composition mass-spring system refer to along micro-
Accelerometer chip sensitive direction sa, the first cantilever beam 4-a, the second cantilever beam 4-b have elastic characteristic, the first cantilever beam 4-a,
Second cantilever beam 4-b is along the diagonal dc2 direction of mass 3;First quartzy double-ended tuning fork 2-a, the second quartzy both-end
Fixing tuning fork 2-b is along other diagonal dc1 of mass 3, the first quartz double-ended tuning fork 2-a, the second stone
English double-ended tuning fork 2-b structure is identical, and quartzy double-ended tuning fork 2-a, 2-b are in differential fashion arrangement, this diagonal
Arrangement can reduce the size of micro-acceleration gauge microarray biochip.
With reference to Fig. 2, described silicon base 1 adopts bulk silicon process, solid in order to position the first quartzy both-end when mounted
Accordatura fork 2-a, the second quartzy double-ended tuning fork 2-b, have four locating slots 6-a, 6- in silicon base 1 diagonal dc1
b、6-c、6-d.
Reference picture 3-1, two fixing ends 7-a, 7-b of described quartzy double-ended tuning fork 2 are separately fixed at silicon base 1
Four locating slots 6-a, 6-b, 6-c, 6-d in;Reference picture 3-2, described quartzy double-ended tuning fork 2 is processed by quartz crystal
, electrode 8 is coated with four sides on each prong of tuning fork, is electrically connected to each other between electrode 8, during normal work, meeting on electrode 8
There is alternating voltage, due to piezoelectricity and the inverse piezoelectric effect of quartz crystal, quartzy double-ended tuning fork 2 can be in same plane
Anti-phase vibration pattern.
With reference to Fig. 4, in four described locating slots, the depth of 6-a, 6-b, 6-c, 6-d needs to ensure quartzy both-end stationary tone
After fork 2 pastes on a silicon substrate 1, it is in the centre position in silicon wafer thickness section 9, the purpose of so design is to improve micro- acceleration
The linearity of degree meter chip.
The operation principle of the present invention is:
With reference to Fig. 5, described two quartzy double-ended tuning fork 2-a, 2-b are connected to the stone being made up of double phase inverters
In English resonance circuit 10-a, 10-b, quartz resonance circuit provides alternating voltage, and quartz resonance circuit 10-a, 10-b are in itself
DC level is powered, and the resistance r1~r4 in quartz resonance circuit 10-a, 10-b and electric capacity c1 needs solid according to quartzy both-end
The equivalent circuit parameter that 2-a, 2-b are pitched in accordatura specifically sets, to guarantee to encourage quartzy double-ended tuning fork 2-a, 2-b can
It is in conplane anti-phase vibration pattern, quartz resonance circuit 10-a, 10-b output frequency digital signal, through difference frequency
The difference on the frequency of both circuit counting is as the output of sensor.
Cantilever beam 4-a, 4-b in silicon base 1 and mass 3 composition mass-spring system, when having acceleration along quick
When sense direction sa acts on micro-acceleration gauge chip, according to Newton's second law, mass 3 can be acted on by inertia force, matter
Inertia force is delivered in quartzy double-ended tuning fork 2-a, 2-b gauge block 3, causes inside quartzy double-ended tuning fork 2-a, 2-b
Axial stress changes, and this axial stress changes the frequency of vibration of tuning fork, by detection quartzy double-ended tuning fork 2-a, 2-b
The measurement of acceleration signal is realized in the change of frequency of vibration.
Because quartzy double-ended tuning fork 2-a, 2-b are in differential fashion arrangement, that is, when having acceleration effect in biography
During sensor, one therein quartzy double-ended tuning fork tension, its frequency of vibration becomes big;Other one quartzy double-ended tuning fork
Pressurized, its frequency of vibration diminishes.The difference of two quartzy double-ended tuning fork frequency changes is as the output of sensor.
The present invention can eliminate the impact to sensor for the temperature.Bi-material silicon and the heat of quartz that sensor chip adopts
The coefficient of expansion is different.When temperature changes, thermal stress can be produced in two quartzy double-ended tuning fork 2-a, 2-b and cause it to shake
Dynamic frequency changes.Both frequency changes are consistent, that is, big or diminish and absolute value is identical with time-varying, and pass
The output signal of sensor is the difference of both frequency of vibration changes, and the frequency change therefore being caused by thermal stress is cancelled out each other, thus
Eliminate the impact to sensor for the temperature.