WO2015163300A1 - Capteur d'accélération - Google Patents

Capteur d'accélération Download PDF

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Publication number
WO2015163300A1
WO2015163300A1 PCT/JP2015/062043 JP2015062043W WO2015163300A1 WO 2015163300 A1 WO2015163300 A1 WO 2015163300A1 JP 2015062043 W JP2015062043 W JP 2015062043W WO 2015163300 A1 WO2015163300 A1 WO 2015163300A1
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WO
WIPO (PCT)
Prior art keywords
cap layer
weight
acceleration sensor
acceleration
electrodes
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PCT/JP2015/062043
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English (en)
Japanese (ja)
Inventor
希元 鄭
雅秀 林
Original Assignee
日立オートモティブシステムズ株式会社
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Publication of WO2015163300A1 publication Critical patent/WO2015163300A1/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
    • G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
    • G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
    • G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
    • G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
    • G01P15/125—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values by capacitive pick-up
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
    • H01L29/84—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by variation of applied mechanical force, e.g. of pressure

Definitions

  • the present invention relates to an acceleration sensor.
  • An electrostatic capacitance detection type acceleration sensor generally includes a weight that is displaced according to an applied acceleration, and a detection electrode that forms a capacitance between the weight. These components can be formed by applying a photolithography technique, an etching technique, and a substrate bonding technique to a silicon substrate having a plurality of layers.
  • a weight is formed on a device layer disposed in a plane formed by a first direction and a second direction perpendicular to the first direction, and a first direction perpendicular to the first direction and the second direction is formed.
  • a support substrate and a cap layer are formed so as to sandwich the weight in three directions (up and down directions).
  • the weight is plate-shaped and is suspended on the support substrate via a torsion beam at a position away from the center of gravity of the weight.
  • the displacement of the weight in the third direction is detected by using two detection electrodes formed on the support substrate side.
  • the detection electrodes are symmetrically arranged at an equal distance when viewed from the rotation center of the weight. Accordingly, the weight rotates in accordance with the acceleration applied in the third direction (z direction) perpendicular to the plane of the support substrate, and the capacitance of the detection electrode arranged at a position where the weight approaches the support substrate side increases. To do.
  • the capacitance of the detection electrodes arranged symmetrically about the rotation axis of the weight, that is, in the opposite direction, that is, at a position where the weight is separated from the support substrate is reduced.
  • the acceleration sensor described in Patent Document 2 below is configured such that the weight rotates around the first direction or the second direction, and the detection electrode is disposed on the cap layer side, as in the acceleration sensor described in Patent Document 1.
  • a weight imbalance is formed by removing a part of the weight, thereby realizing the rotation of the weight and the displacement in the third direction. Therefore, the acceleration sensor described in Patent Document 2 can make the rotation center of the weight coincide with the center of the cavity formed so as to surround the weight by the support substrate and the cap layer. That is, the two detection electrodes are arranged symmetrically with respect to the shape center of the weight and the center of the cavity.
  • the two detection electrodes are uniformly placed on the weight. Displace. Therefore, since the change in the capacitance of the detection electrode due to strain is canceled by the differential detection, it can be separated from the signal due to the application of acceleration. As a result, it is possible to provide an acceleration sensor with little zero point drift due to mounting or environmental temperature change.
  • a cavity is configured by arranging a support substrate and a cap layer so that a weight is sandwiched between upper and lower sides.
  • a plurality of posts connecting the support substrate, the device layer, and the cap layer are provided for the purpose of preventing the cavity from being deformed by an external factor such as a change in environmental temperature.
  • a conductor penetrating the support substrate or the cap layer is formed as means for applying an electric signal to the weight.
  • a typical technique to reduce the cost of an acceleration sensor is to protect the weight from external physical force by forming a cavity so that the weight is surrounded by a support substrate and a cap layer.
  • a conductive electrode material (through electrode) penetrating the support substrate or the cap layer is used as a device. It is necessary to form through until reaching the layer and to connect the weight and the signal processing IC mechanically and electrically.
  • the present invention has been made in view of the problems as described above, and has little initial and temporal zero-point drift even when used in a poor installation environment while keeping the manufacturing cost low.
  • An object is to provide a highly reliable acceleration sensor.
  • the weight that rotates when acceleration is applied in the z direction is disposed in the cavity surrounded by the support substrate and the cap layer.
  • the cap layer is formed so that masses per unit area are different from each other on both sides of the rotation axis of the weight.
  • the acceleration sensor according to the present invention it is possible to suppress the zero point drift caused by environmental changes and changes with time.
  • FIG. 1 It is a schematic diagram which shows the whole structure of acceleration sensor S1 which concerns on Embodiment 1.
  • FIG. It is a top view which shows the weight 2 with which acceleration detection element S1E is provided, and its periphery structure.
  • FIG. 3 is a sectional view taken along the line A-A ′ of FIG. 2. It is a figure explaining the principle of operation of acceleration sensor S1.
  • FIG. 1 It is a top view which shows the weight 2 with which acceleration detection element S1E is provided, and its periphery structure.
  • FIG. 3 is a sectional view taken along the line A-A ′
  • FIG. 8 is a cross-sectional view taken along line A-A ′ of FIG. 7. It is a figure explaining the structure of the acceleration sensor which concerns on Embodiment 3.
  • FIG. It is a figure which shows the structural example which replaced with the level
  • the constituent elements are not necessarily indispensable unless otherwise specified or apparently indispensable in principle.
  • FIG. 1 is a schematic diagram showing an overall configuration of an acceleration sensor S1 according to Embodiment 1 of the present invention.
  • the acceleration sensor S1 includes an acceleration detection element S1E, a signal processing IC (Integrated Circuit) 50, a lead frame 150, and a conductive wire 152.
  • the conductive wire 152 electrically connects the acceleration detection element S1E, the signal processing IC 50, and the lead frame 150.
  • the signal processing IC 50 and the acceleration detection element S1E are fixed on the lead frame 150 and the signal processing IC 50 through an adhesive 151, respectively.
  • Acceleration sensor S1 is completed by press-molding thermosetting resin 153 and covering each part.
  • the acceleration sensor S1 is incorporated in a higher system, and provides the detected physical quantity information to the higher system.
  • FIG. 2 is a plan view showing the weight 2 provided in the acceleration detecting element S1E and its peripheral configuration.
  • a plan view of the device layer 1c in a state where the cap layer 100 described later with reference to FIG. 3 is peeled off is shown.
  • the acceleration detecting element S1E includes a weight 2 formed by processing by a method described later.
  • the weight 2 is suspended by the fixed part 6 via the torsion beam 5, and is thereby configured to rotate around the y direction (second direction).
  • the fixing portion 6 is fixed to the support substrate 1a via an intermediate insulating layer 1b described later. Accordingly, the weight 2 rotates around the second direction in proportion to the acceleration applied in the third direction (z direction), that is, is displaced in the third direction.
  • the pad E1 will be described later.
  • the acceleration detection element S1E includes, for example, an SOI (Silicon On Insulator) substrate 1 in order to form mechanical components such as the weight 2 and the fixed portion 6.
  • the SOI substrate 1 has a configuration in which an intermediate insulating layer 1b is formed on a support substrate 1a, and a device layer 1c is formed on the intermediate insulating layer 1b.
  • the support substrate 1a is made of, for example, silicon (Si).
  • the intermediate insulating layer 1b is made of, for example, silicon oxide (SiO 2 ).
  • the device layer 1c is made of, for example, conductive silicon.
  • the total thickness of the support substrate 1a and the intermediate insulating layer 1b is, for example, several hundred ⁇ m.
  • the thickness of the device layer 1c is, for example, several to several tens of ⁇ m.
  • a semiconductor substrate other than the SOI substrate can be used.
  • conductive polysilicon using surface MEMS technology or plated metal such as nickel (Ni) may be used as the device layer 1c.
  • the SOI substrate 1 can also be formed by processing the cavity CD on the support substrate 1a and then thermally oxidizing to form the intermediate insulating layer 1b and further bonding the device layer 1c.
  • Each component of the acceleration detection element S1E is formed by processing the device layer 1c and the cap layer 100.
  • a method of processing the device layer 1c and the cap layer 100 there are the following methods. First, a resist that reacts to light, an electron beam, or the like is applied onto the device layer 1c or the cap layer 100, and then the resist on the device layer 1c or the cap layer 100 is applied using photolithography or an electron beam drawing technique. Remove some. Next, the exposed device layer 1c or the cap layer 100 is removed by using dry etching using RIE (Reactive Ion Etching) or wet etching technology using an alkaline chemical such as TMAH or KOH. Thereafter, by removing the remaining resist, each component described later can be formed on the device layer 1c and the cap layer 100.
  • RIE Reactive Ion Etching
  • TMAH TMAH
  • KOH alkaline chemical
  • fixed side electrodes C1B and C2B are formed in order to measure the displacement of the weight 2.
  • the weight 2 plays a role as a drive side electrode.
  • the fixed electrodes C1B and C2B and the driving electrode form detection electrodes C1 and C2 described later with reference to FIG.
  • the capacitances of the detection electrodes C1 and C2 are arranged so that when one side increases in conjunction with the movement of the weight 2, the other side decreases. Therefore, an output proportional to the applied acceleration can be obtained by using the differential detection method described in FIG. Detailed description of each element constituting the circuit will be described later.
  • the cap layer 100 is provided with a step as shown around the rotation center B of the weight 2. Due to this step, the left side stiffness and the right side stiffness of the rotation center B are different from each other. The reason for this will be described later with reference to FIG.
  • the cap layer 100 is a layer for protecting the weight 2, the torsion beam 5, and the detection electrodes C1 and C2 from external impact, mechanical contact, dust, and the like.
  • the cap layer 100 has a trench formed by a dry etching technique or the like.
  • An insulating film 101 such as a thermal oxide film is buried in the trench, and thereby the airtightness of the cavity CD surrounded by the cap layer 100 and the support substrate 1 is maintained.
  • the through electrodes T3 and T4 shown in FIG. 3 are formed by dividing the cap layer 100 by the trench and the insulating film 101, and function as the fixed-side electrodes C1B and C2B.
  • the insulating film 101 can be formed, for example, by thermal oxidation after forming a trench, or by using CVD (Chemical Vapor Deposition).
  • the cap layer 100 in which the insulating film 101 and the through electrodes T3 and T4 are formed is bonded to the SOI substrate 1 on which the weight 2, the torsion beam 5 and the like are formed, so that the weight 2 is mechanically contacted from the outside. And can be protected from dust.
  • a bonding method (a) an eutectic bonding method in which an alloy such as gold or tin is applied between the cap layer 100 and the device layer 1c and then cured by heat treatment, and (b) the cap layer 100 and the device layer 1c.
  • silicon-silicon or silicon-silicon oxide films are directly bonded to each other by hydrogen bonding at room temperature and heating at a high temperature.
  • Pads E1, E3, E4, and the like are formed in order to electrically connect the weight 2, the fixed side electrodes C1B and C2B, and the signal processing IC 50 described later.
  • the pads E3 and E4 are connected to the through electrodes T3 and T4, respectively.
  • the signal processing IC 50 can input and output electrical signals between the weight 2 and the fixed side electrodes C1B and C2B via the pads E1, E3, and E4.
  • FIG. 4 is a diagram for explaining the operating principle of the acceleration sensor S1.
  • the weight 2 is formed such that the weights on both sides of the central axis in the first direction (x direction) are different from each other with the torsion beam 5 as the central axis. That is, when acceleration is applied in the third direction (z direction), the force (F1) received by the left weight 2 (m1) of the torsion beam 5 and the force (F2) received by the right weight 2 (m2) are: The values are different from each other. Further, the distance (r1) from the center of gravity of the left side portion of the weight 2 to the torsion beam 5 and the distance (r2) from the center of gravity of the right side portion of the weight 2 to the torsion beam 5 are also different.
  • Equation 1 shows the moment M generated in the torsion beam 5 when the acceleration a is applied in the third direction.
  • the generated angle ⁇ (displacement of the weight 2 in the third direction) can be defined as the following formula 2.
  • a CV (Capacitance to Voltage) conversion circuit 52 which will be described later, performs differential detection using two detection electrodes C1 and C2 whose capacitance changes in accordance with displacement generated in the third direction.
  • the displacement in the direction (change in capacitance) is converted into an electric signal (voltage).
  • the through electrodes T3 and T4 formed on a part of the cap layer 100 as the fixed electrodes C1B and C2B of the detection electrodes C1 and C2 form a capacitance with the weight 2, and the CV conversion circuit 52 Detects changes in capacitance.
  • the torsion beam 5 (rotation center) at a position away from the center of gravity of the weight 2.
  • the detection electrodes C ⁇ b> 1 and C ⁇ b> 2 are formed so as to have the same capacitance at the same interval in the first direction when viewed from the torsion beam 5 in order to ensure the linearity of the sensor output with respect to the applied acceleration. Therefore, the detection electrodes C1 and C2 are necessarily arranged at positions away from the center of the cavity CA formed by the support substrate 1a and the cap layer 100.
  • the through electrodes T3 and T4 having the role as the fixed side electrodes C1B and C2B are equal in the first direction (x direction) when viewed from the torsion beam 5 (the rotation center of the weight 2). Arranged at a distance. Further, the capacitance formed by the left side portion of the weight 2 around the torsion beam 5 and the fixed side electrode C1B is the same as the capacitance formed by the right side portion of the weight 2 and the fixed side electrode C2B. Has been placed.
  • FIG. 5 is a circuit diagram of the signal processing IC 50.
  • the signal processing IC 50 applies the carrier wave 51 to the fixed side electrodes C1B and C2B via the pads E3 and E4.
  • the weight 2 is connected to the input terminal of the CV conversion circuit 52 via the torsion beam 5, the fixing portion 6, and the pad E1. Thereby, a change in electrostatic capacitance between the weight 2 and the fixed side electrodes C1B and C2B can be detected.
  • the synchronous detection circuit 53 restores the amplitude and frequency following the movement of the weight 2 by processing the output signal from the CV conversion circuit 52 using the frequency of the carrier wave 51.
  • the AD converter 54 converts the result into a digital signal. Thereby, a signal Vo proportional to the acceleration applied to the weight 2 is output.
  • the acceleration sensor S1 employs a package in which a thermosetting resin 153 is pressure-molded for cost reduction. Therefore, the acceleration detection element S1E receives a pressure generated when the thermosetting resin 153 is pressure-molded. Therefore, zero point drift may occur when the acceleration sensor S1 is shipped. Furthermore, the internal stress generated in the thermosetting resin 153 during the formation of the package fluctuates due to relaxation over time due to changes in environmental temperature and humidity. Therefore, even after the acceleration sensor S1 is shipped, zero point drift can occur.
  • a step is provided in the cap layer 100 so that the rigidity of the portion corresponding to the fixed side electrode C1B and the rigidity of the portion corresponding to the fixed side electrode C2B are different from each other. Yes.
  • the specific configuration will be described below.
  • FIG. 6 is a diagram showing a result of analyzing the deformation state of the cap layer 100 and the fixed side electrodes C1B and C2B by the finite element method when a pressure of several Mpa is applied to the cap layer 100.
  • FIG. FIG. 6A shows an analysis result when the cap layer 100 has no step t.
  • FIG. 6B shows an analysis result when a step t is provided in the cap layer 100.
  • the inflection point of deformation of the cap layer 100 is located at the center of the cavity CA.
  • the displacement amounts of the fixed side electrodes C1B and C2B arranged symmetrically about the rotation center B in the third direction (z direction) are different from each other.
  • the capacitance changes ⁇ C1 and ⁇ C2 of the detection electrodes C1 and C2 are also different from each other, and a non-zero value that is originally expected as the sensor output (initial zero point) is output.
  • the inflection point of the deformation of the cap layer 100 is located immediately above the rotation center B of the weight 2.
  • the displacement amounts of the fixed-side electrodes C1B and C2B in the third direction (z direction) have the same value.
  • the capacitance changes ⁇ C1 and ⁇ C2 of the detection electrodes C1 and C2 also have the same value, and these fluctuations are offset by the differential detection, so that the sensor output becomes a value as originally expected.
  • thermosetting resin 153 When the internal stress is relaxed with time and the capacitance changes ⁇ C1 and ⁇ C2 change, (b) the capacitance changes ⁇ C1 and ⁇ C2 change as the curable resin 153 expands by absorbing moisture from the environment. (C) When the capacitance changes ⁇ C1 and ⁇ C2 fluctuate due to mounting stress and strain generated when the lead frame 150 is constrained on a specific substrate by soldering, etc. In this case, the output drift (variation) of the acceleration sensor S1 can be suppressed.
  • the portion corresponding to the fixed side electrode C1B and the portion corresponding to the fixed side electrode C2B of the cap layer 100 have different thicknesses. Specifically, the portion corresponding to the fixed side electrode C1B arranged on the light side with the rotation center B of the weight 2 as the center is formed thinner than the portion corresponding to the fixed side electrode C2B arranged on the heavy side. Has been. Thereby, the displacement amount of each detection electrode C1 and C2 which generate
  • thermosetting resin 153 In the first embodiment, an example in which packaging is performed by press-molding the thermosetting resin 153 is shown.
  • the present invention is not limited to the packaging method in which the thermosetting resin 153 is pressure-molded, and even in a package in which the acceleration detection element S1E is put in a container that is shaped in advance, such as a ceramic package, and the lid is covered. Needless to say, similar effects can be obtained.
  • the acceleration detection element S1E is a composite of thin layers made of different materials such as the support substrate 1a, the intermediate insulating layer 1b, the device layer 1c, the cap layer 100, the lead frame 150, the signal processing IC 50, and the adhesive 151.
  • the material is configured as a body and the linear expansion coefficients of the respective constituent materials are different, so that distortion occurs due to a change in environmental temperature.
  • the inflection point is adjusted to be located at the rotation center B by reducing the thickness of the cap layer 100 on the left side of the rotation center B, that is, in the direction in which the cavity CA is small. Similarly, the same effect can be expected even if the cap layer 100 on the right side of the rotation center B is thickened. Further, although not shown, it is needless to say that the same effect can be obtained even if the step t is arranged not only in one but also in a slit shape. Further, the step can be configured in a multi-step manner.
  • the cavity CA is formed so as to surround the simplest plate-shaped weight 2 and the gaps at equal intervals (minimum), processing and manufacturing processes are simple, and the area is used. It can be said that the efficiency is high. That is, it can be said that it is advantageous for miniaturization.
  • FIG. 7 is a plan view showing main components of the acceleration sensor S2 according to the second embodiment of the present invention.
  • FIG. 7 shows a state in which the cap layer 100 is peeled off as in FIG. Below, the part which overlaps with the content demonstrated about acceleration sensor S1 of Embodiment 1 is omitted, and the changed and added part is demonstrated intensively.
  • the manufacturing method of the acceleration sensor S2 is the same as that of the acceleration sensor S1 in the first embodiment.
  • the difference from the first embodiment is that the weight 2 is arranged so as to surround the fixed portion 6, that is, the fixed portion 6 is formed inside the weight 2, and the fixed portion 6 and the signal are connected via the through electrodes T 1 and T 2. That is, the processing IC 50 is electrically connected.
  • the through electrodes T1 and T2 are configured to mechanically connect the device layer 1c and the cap layer 100, they serve as posts that suppress deformation of the cap layer 100 due to external pressure application. Also have.
  • a fixed portion 6 is formed inside the weight 2
  • a torsion beam 5 is formed so as to extend from the fixed portion 6 in the second direction
  • a weight is formed at the tip of the torsion beam 5. 2 are connected.
  • the fixing portion 6 is fixed to the supporting substrate 1a via the intermediate insulating layer 1b in the vicinity of the center portion of the cavity CA formed by the supporting substrate 1a and the cap layer 100 so as to surround the weight 2.
  • FIG. 8 is a cross-sectional view taken along the line A-A ′ of FIG.
  • the acceleration sensor S2 detects the displacement of the weight 2 so that the through electrodes T3 and T4 functioning as the fixed-side electrodes C1B and C2B are formed in the cap layer 100. It has a capacitance. Pads E3 and E4 are formed on the through electrodes T3 and T4, and are electrically connected to the signal processing IC 50.
  • the through electrodes T1 and T2 penetrate the cap layer 100 from above the fixed portion 6 and reach the fixed portion 6.
  • the through electrodes T1 and T2 are disposed along the rotation axis B.
  • a pad E1 is connected to the through electrodes T1 and T2.
  • the signal processing IC 50 inputs and outputs electrical signals through the pad E1 and the through electrodes T1 and T2. As a result, the electric signal propagates to the weight 2 through the fixed portion 6.
  • only one through electrode is sufficient, but by providing a plurality of through electrodes, the connection between the cap layer 100 and the device layer 1c can be determined.
  • a closed loop can be formed for inspection.
  • the through electrodes T1 and T2 serve as electrodes that electrically connect the weight 2 and the signal processing IC 50 and also serve as posts that prevent the cap layer 100 from collapsing.
  • the cap layer 100 In order to measure the displacement of the weight 2 in the third direction (z direction), a part of the cap layer 100 is formed as the through electrodes T3 and T4, which are used as the fixed electrodes C1B and C2B. Therefore, when the thermosetting resin 153 is pressure-molded, the capacitances of the detection electrodes C1 and C2 also change according to the deformation of the cap layer 100.
  • the acceleration detecting element S2E uses a laminated structure of a plurality of different materials such as silicon as the support substrate 1a, silicon oxide as the intermediate insulating layer 1b, and metal materials such as aluminum as the pads E1, E3, and E4. It is made as. Therefore, it is easily conceivable that the capacitance of the detection electrodes C1 and C2 changes due to the deformation of the acceleration detection element S2E or the cap layer 100 due to a change in environmental temperature.
  • Capacitance changes of the detection electrodes C1 and C2 are caused by equal capacitances in the first direction (x direction) with the detection electrodes C1 and C2 having the torsion beam 5 (rotation center: B line) as an axis of symmetry.
  • a step t is formed in the cap layer 100, the inflection point of deformation of the cap layer 100 is aligned with the rotation center, and a positive carrier wave is applied to the detection electrode C1.
  • a negative carrier wave is applied to the detection electrode C2, and the sum is input to the CV conversion circuit 52 to perform differential detection, so that it can be canceled theoretically.
  • 0-point output of the sensor at the initial stage (0-point output that does not change at the product shipment stage: 0-point output is the sensor output when no acceleration is applied to the sensor and is expected to be 0)
  • thermosetting resin 153 In the case of a package employing the thermosetting resin 153, an internal stress is generated inside the resin during pressure molding, and this internal stress is relieved with time. The amount of deformation of 100 also changes over time. Furthermore, the volume of the thermosetting resin 153 increases or decreases according to the environmental humidity. That is, the deformation amount of the cap layer 100 changes depending on the environmental humidity. The zero point drift depending on these environmental and temporal factors cannot be electrically corrected.
  • the initial and temporal fluctuations of the detection electrodes C1 and C2 are suppressed, and even when there is a fluctuation, the fluctuation amount is made the same between C1 and C2, so that It needs to be able to offset.
  • a plurality of through electrodes T1 and T2 are provided along the rotation axis (twisted beam 5) to serve as posts, thereby minimizing the deformation of the cap layer 100 and reducing the cap layer.
  • a step t it is useful that the capacitance variations of the detection electrodes C1 and C2 are made the same and can be canceled by differential detection even if deformation occurs.
  • the fixed portion 6 is arranged near the center of the cavity CA, and (configuration b) a plurality of posts (through electrodes T1, T2) are arranged on the fixed portion 6 along the rotation axis.
  • the detection electrodes C1 and C2 are arranged at equal intervals and the same capacity in the first direction (x direction) with the torsion beam 5 (rotation axis: B line) as the axis of symmetry.
  • the cap layer 100 has a step t and is configured such that the capacitance changes of the detection electrodes C1 and C2 are the same even when the cap layer 100 is deformed.
  • the fixed portion 6 and the torsion beam 5 are arranged near the center of the cavity CA (the B line in FIG. 7), and the through electrodes T1 and T2 are arranged on the fixed portion 6 along the rotation axis (the B line). Even when a pressure is applied to the layer 100 from the outside, the amount of deformation is made as small as possible. Further, since the cap layer 100 has the step t, even if the cap layer 100 is deformed, the capacitance changes of the detection electrodes C1 and C2 are the same, so the influence of the deformation is offset by differential detection. can do.
  • the cap layer 100 It can easily be considered to reduce the deformation amount of the cap layer 100 by increasing the thickness of the cap layer 100.
  • a narrow trench is processed in the cap layer 100, and the insulating film 101 (the through electrodes T1, T2 in FIGS. , T3 and T4).
  • the ratio of the width of the trench to the thickness of the cap layer 100 is 20 or less, so that mass production is possible. Therefore, increasing the thickness of the cap layer 100 has a limit from the viewpoint of mass productivity.
  • the width of the trench is several ⁇ m, and the thickness of the cap layer 100 is 100 to 400 ⁇ m.
  • Detecting electrodes C1 and C2 are arranged at equal intervals and the same capacity in the first direction (x direction) with the torsion beam 5 (B line) as the axis of symmetry. Further, the thickness of the cap layer 100 on the cavity CA2 side, which is short in the first direction from the rotation center (B line), is formed thinner than the thickness of the cap layer 100 on the opposite side of the cavity CA1. That is, adjustment is made so that the rigidity in the third direction of the fixed side electrodes C1B and C2B of the detection electrodes C1 and C2 is approximately the same. Therefore, even when the cap layer 100 is deformed by the application of pressure from the outside or a change in the surrounding environment, the capacitance fluctuations of the detection electrodes C1 and C2 are the same, and the influence can be offset by differential detection.
  • the acceleration sensor S ⁇ b> 2 uses the through electrodes T ⁇ b> 1 and T ⁇ b> 2 installed to apply an electric signal to the weight 2 as a post supporting the cap layer 100, thereby 100 deformations can be reduced. Furthermore, by providing the step t in the cap layer 100, it is possible to cancel the fluctuations in the capacitance of the detection electrodes C1 and C2 due to external pressure and environmental fluctuations, and to improve the stability of the zero point output of the sensor.
  • Embodiments 1 and 2 it has been described that the capacitance fluctuation amount of the detection electrodes C1 and C2 is made the same by providing the step t in the cap layer 100.
  • the essence of Embodiment 1 is that the inflection point of the cap layer 100 coincides with the rotation center (B line).
  • the essence of the second embodiment is to make the through electrodes T3 and T4 have the same rigidity. That is, by adjusting the rigidity of the through-electrodes T3 and T4 according to the sizes of the cavities CA1 and CA2, the amount of deformation caused by external pressure application or environmental fluctuation can be made the same.
  • FIG. 9 is a diagram illustrating the configuration of the acceleration sensor according to the third embodiment.
  • FIG. 9C is a plan view of the acceleration sensor according to the third embodiment, and shows a state where the cap layer 100 is peeled off as in FIG.
  • FIG. 9D is a cross-sectional view taken along the line D-D ′ of FIG.
  • FIG. 9A is a plan view of the acceleration sensor S1 according to the first embodiment, and is shown together with FIG. 9C for comparison.
  • FIG. 9B is a cross-sectional view taken along the line C-C ′ of FIG.
  • a hole 10 is used instead of the step t.
  • the hole 10 is formed so as not to penetrate the cap layer 100 along the third direction (z direction) from the insulating film 101 side toward the weight 2.
  • Other configurations are the same as those in the first and second embodiments.
  • the inflection point of the cap layer 100 can be variously adjusted by adjusting the arrangement, size, pitch, and depth of the holes 10. Specifically, by forming more holes 10 on the left side of the rotation axis B than on the right side, the rigidity of the cap layer 100 on the left side of the rotation axis B can be made weaker than that on the right side. Further, by using the hole 10, unlike the case where the step t is provided, the thickness of the cap layer 100 can be kept constant. Therefore, the insulating film 101 and the pads E3 and E4 arranged on the cap layer 100 can be formed by a simpler manufacturing method.
  • a cylindrical hole 10 that does not penetrate the cap layer 100 is provided in the cap layer 100.
  • a hole having a shape such as a square or a band (groove) is provided in the cap layer 100.
  • the hole is not limited to a circular hole.
  • FIG. 10 is a diagram illustrating a configuration example in which the groove 11 is provided in the cap layer 100 in place of the step t in order to adjust the inflection point of the cap layer 100.
  • FIG. 10A is a plan view of the cap layer 100
  • FIG. 10B is a cross-sectional view taken along the line E-E 'of FIG.
  • the groove 11 is formed on the bottom surface of the cap layer 100, that is, on the cavity CA side.
  • the arrangement of the fixing portion 6 described in the second embodiment is assumed, but the groove 11 can be provided in the configuration described in the first embodiment.
  • FIG. 11 is a diagram showing a result of analyzing the deformation state of the cap layer 100 by a finite element method.
  • FIG. 11A shows an analysis result when there is no groove 11
  • FIG. 11B shows an analysis result when the groove 11 is present.
  • the displacement amounts of the through electrodes T3 and T4 in the third direction can be made substantially the same. Accordingly, since the capacitance changes ⁇ C1 and ⁇ C2 have the same value, the influence of deformation of the cap layer 100 can be offset by using differential detection.
  • ⁇ Embodiment 3 Supplement about hole 10 and groove 11> All the depressions such as the hole 10 and the groove 11 for adjusting the inflection point and rigidity of the cap layer 100 are arranged so as not to straddle the insulating film 101 and the trench that separates the fixed-side electrodes C1B and C2B from the surrounding silicon. Has been.
  • the first embodiment is performed in order to remove silicon of the cap layer 100 and silicon oxide constituting the insulating film 101.
  • a manufacturing step different from ⁇ 2 is required.
  • SF6 is used as a reactive gas in order to remove silicon
  • CHF3 is used as a reactive gas in order to remove a silicon oxide film, so that the manufacturing process becomes somewhat complicated.
  • the depressions such as the holes 10 and the grooves 11 are formed so as not to cross the trench, only the silicon needs to be processed, so that the manufacturing process can be simplified.
  • the depressions such as the holes 10 and the grooves 11 are formed in the cap layer 100 along the third direction from the outer side of the cap layer 100 (that is, the surface not facing the weight 2) toward the weight 2.
  • the distance between the fixed side electrode C1B or C2B and the weight 2 is not affected by the presence of the depression. Therefore, in this case, as shown by the hole 10 in FIG. 9C, the position overlapping the fixed side electrode C1B or C2B in the third direction (z direction) (inner portion surrounded by the dotted line in FIG. 9C) You may arrange
  • the cap layer 100 is formed along the third direction with the depressions such as the holes 10 and the grooves 11 from the inner side of the cap layer 100 (ie, the surface facing the weight 2) toward the opposite surface.
  • the hole 10 or the groove 11 is located between the fixed side electrode C1B or C2B and the weight 2, so that the detection electrodes C1 and C2 and the weight depend on the positions of these depressions.
  • the capacitance formed by 2 is affected. Therefore, in this case, it is desirable to arrange the depression at a position that does not overlap with the fixed side electrode C1B or C2B in the third direction (z direction).
  • the degree of freedom for adjusting the inflection point and the rigidity of the cap layer 100 is reduced as compared with the case where the depression is formed from the outside to the inside of the cap layer 100.
  • the pads E1, E3, E4, etc. on the depressions since it is not necessary to form the pads E1, E3, E4, etc. on the depressions, the formation and arrangement of the pads E1, E3, E4 and the routing of the wiring are facilitated.
  • the present invention is not limited to the embodiments described above, and includes various modifications.
  • the above embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to the one having all the configurations described.
  • the step t, the hole 10 and the groove 11 are exemplified as means for adjusting the rigidity of the cap layer 100.
  • the cap is formed on both sides of the rotation axis B. If the mass per unit area in the XY plane of the layer 100 can be configured to be different from each other, it is considered that the same effect can be exhibited.
  • the step t, the hole 10, and the groove 11 are used to change the inflection point and rigidity of the cap layer 100, and the third direction of the fixed side electrodes T3 (C1B) and T4 (C2B). It was shown that the amount of displacement in can be adjusted. However, it is needless to say that these methods are not limited to those independent from each other, and can be variously modified without departing from the gist thereof.
  • the recesses can be formed on the front or back of the cap layer 100 by combining the holes 10 and the grooves 11.
  • the step t may be combined as necessary.
  • the packaging technology using the thermosetting resin 153 has been described for convenience of explanation.
  • the acceleration detecting element is composed of a plurality of materials, the linear expansion coefficient is Deformation of the acceleration detection element due to the difference is easily assumed. Therefore, the concept of the present invention is also useful in various packaging technologies that involve deformation of the acceleration detecting element itself or distortion due to mounting, such as a ceramic package or a pre-molded package in which plastic is molded in advance and components are mounted therein. is there.
  • the present invention can be widely used in the fields of attitude detection of automobiles, robots, etc., camera shake correction, navigation attitude / direction detection, game machine attitude detection sensors, and the like. In particular, it can be expected to exert its effect when used in a moving body or when there are heat sources such as engines, motors, electromagnets, and microcomputers in the vicinity.
  • S1 to S2 Acceleration sensor 1a: Support substrate 1b: Intermediate insulating layer 1c: Device layer 2: Weight 5: Torsion beam 6: Fixing part C1 to C2: Detection electrode C1B: Detection electrode fixed side electrode C2B: Detection electrode fixing Side electrode CA: Cavity CA1: Cavity CA2: Cavity T1-T2: Through electrode (post) T3 to T4: Through electrode (detection electrode fixed side electrode) E1 to E4: Pad 101: Insulating film 50: Signal processing IC 51: Carrier 52: CV conversion circuit 53: Synchronous detection circuit 54: AD conversion unit 100: Cap layer 150: Lead frame 151: Adhesive 152: Wire 153: Thermosetting resin

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Ceramic Engineering (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Computer Hardware Design (AREA)
  • Pressure Sensors (AREA)

Abstract

　La présente invention vise à fournir un capteur d'accélération hautement fiable ayant une dérive du zéro minimale à la fois au départ et au cours du temps, même lorsqu'il est utilisé dans de mauvaises conditions d'installation, tout en maintenant les coûts de production bas. Dans ce capteur d'accélération, un poids qui tourne lorsqu'une accélération est appliquée dans la direction z est positionné à l'intérieur d'une cavité qui est entourée par un substrat de support et une couche d'encapsulation. La couche d'encapsulation est formée de telle sorte qu'il existe une différence dans la surface par unité de masse entre les deux côtés de cette dernière situés de chaque côté de l'arbre rotatif du poids (voir fig. 1).
PCT/JP2015/062043 2014-04-24 2015-04-21 Capteur d'accélération WO2015163300A1 (fr)

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JP2014-089742 2014-04-24
JP2014089742A JP2015210095A (ja) 2014-04-24 2014-04-24 加速度センサ

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WO2015163300A1 true WO2015163300A1 (fr) 2015-10-29

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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005052602A1 (fr) * 2003-11-20 2005-06-09 Honeywell International Inc. Accelerometre a detection capacitive et reequilibrage electrostatique presentant un amortissement gazeux egalise

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005052602A1 (fr) * 2003-11-20 2005-06-09 Honeywell International Inc. Accelerometre a detection capacitive et reequilibrage electrostatique presentant un amortissement gazeux egalise

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