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WO2018050965A1 - Dispositif accéléromètre et procédé de fabrication du dispositif accéléromètre - Google Patents

Dispositif accéléromètre et procédé de fabrication du dispositif accéléromètre Download PDF

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Publication number
WO2018050965A1
WO2018050965A1 PCT/FI2017/050652 FI2017050652W WO2018050965A1 WO 2018050965 A1 WO2018050965 A1 WO 2018050965A1 FI 2017050652 W FI2017050652 W FI 2017050652W WO 2018050965 A1 WO2018050965 A1 WO 2018050965A1
Authority
WO
WIPO (PCT)
Prior art keywords
cantilever
substrate
drain electrode
electrode
previous
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/FI2017/050652
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English (en)
Inventor
Xuefeng Song
Pertti Hakonen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Aalto Korkeakoulusaatio sr
Original Assignee
Aalto Korkeakoulusaatio sr
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Aalto Korkeakoulusaatio sr filed Critical Aalto Korkeakoulusaatio sr
Publication of WO2018050965A1 publication Critical patent/WO2018050965A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • 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
    • G01P15/0894—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 non-contact electron transfer, i.e. electron tunneling
    • 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
    • G01P15/0802—Details
    • 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
    • G01P2015/0805—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 being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration
    • G01P2015/0822—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 being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration for defining out-of-plane movement of the mass
    • G01P2015/0825—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 being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration for defining out-of-plane movement of the mass for one single degree of freedom of movement of the mass
    • G01P2015/0828—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 being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration for defining out-of-plane movement of the mass for one single degree of freedom of movement of the mass the mass being of the paddle type being suspended at one of its longitudinal ends

Definitions

  • the invention relates to an accelerometer device for determining acceleration introduced to the accelerometer device and manufacturing method for manufacturing the accelerometer device.
  • the invention relates to tunneling accelerometers.
  • Accelerometers are widely used in various scenarios in modern world, e. g., seismology, transportation, aerospace, navigation, automation, industry, security, and consumer electronics. Wide bandwidth, high sensitivity, small footprint MEMS (Micro Electro-Mechanical System) accelerometers are favored in many applications, but such high-end accelerometers are far from mature for large scale industrial deployment. Quantum tunneling effect of electrons between adjacent electrodes has been known to be extremely sensitive to the tunneling gap, which makes it a plausible candidate for miniaturized sensors of displacement and acceleration. Unlike the capacitive accelerometers where the minimum size is limited by stray capacitance, or the piezoelectric ones where high voltage is required, tunneling based accelerometers are superior on miniaturization and integration with semiconductor circuits.
  • MEMS Micro Electro-Mechanical System
  • tunneling current based accelerometers do suffer from difficult fabrication and long-term instability in their commercialization. There is thus a need for a tunneling accelerometer which is small, sensitive, easy to fabricate, and reliable.
  • An object of the invention is to alleviate and eliminate the problems relating to the known prior art. Especially the object of the invention is to provide an accelerometer which is small, sensitive, easy to fabricate, and reliable. The object of the invention can be achieved by the features of independent claims.
  • the invention relates to an accelerometer device according to claim 1.
  • the invention relates to a manufacturing method for manufacturing the accelerometer device according to claim 16.
  • an accelerometer device for determining acceleration introduced to the accelerometer device comprises a substrate having first and second surfaces.
  • a cantilever having first and second ends, wherein the cantilever is anchored to the substrate via the first end and wherein the second end is a free end. The free end is moved towards and away from the first surface of the substrate when acceleration is introduced.
  • the device also comprises a source electrode, drain electrode and a gate electrode arranged on the substrate, advantageously on the first surface of the substrate being faced against the cantilever.
  • the source electrode and the first end of the cantilever are arranged in a galvanic contact with each other.
  • the source electrode is preferably made of Pd, Pt, or Au in order to provide good galvanic or Ohmic contact with the cantilever.
  • the drain electrode and the cantilever are arranged so that a tunneling gap is formed between the drain electrode and the cantilever in order to allow tunneling current from the drain electrode to the cantilever over the tunneling gap.
  • bias voltage typically from 0.01 V to 10 V
  • bias voltage is also provided from the drain electrode to the source electrode and again to the cantilever so that the tunneling current from the drain electrode (16) to the source electrode via the cantilever has a net flow.
  • the tunneling current is advantageously maintained over the tunneling gap in a chosen constant value, typically in the range of 0.1 nA to 10 nA through a feedback circuit by controlling the gate voltage on the gate electrode.
  • a chosen constant value typically in the range of 0.1 nA to 10 nA
  • electrostatic force between the gate electrode and the cantilever is applied to maintain the gap constant, so to force, advantageously to pull, the second end of the cantilever in relation to the substrate in a position so that the tunneling current (electron flow) due to tunneling effect between the drain electrode and the cantilever is maintained constant and thus maintaining the tunneling gap between the cantilever and the drain electrode.
  • the equilibrium position is balanced between the electrostatic pulling force and the spring-restoring force of the cantilever.
  • the tunneling gap should be small enough, typically from 0.1 nm to 10 nm, so that the electrons tunnel through the gap.
  • the gate voltage applied on the gate electrode is thus proportional to the acceleration introduced, and the acceleration can be determined by determining the gate voltage applied on the gate electrode needed to maintain the tunneling gap and thus the tunneling current constant.
  • the cantilever is either a mono- or multilayer cantilever.
  • the cantilever advantageously comprises carbon material, such as graphene or diamond like carbon (DLC), which offers high reliability due to the crystalline nature of graphene or DLC.
  • carbon material such as graphene or diamond like carbon (DLC)
  • the substrate may also comprise a stamp, advantageously a polymer stamp, for anchoring the cantilever to the substrate.
  • the cantilever is advantageously anchored to the substrate via the first end of the cantilever, and it can be anchored either directly by the stamp or the first end of the cantilever can be arranged between the stamp and the source electrode thereby providing the galvanic contact between the source electrode (and the cantilever via the first end of the cantilever.
  • the cantilever may also comprise a proof mass, but it is to be noted that this is an optional feature.
  • the proof mass may comprise e.g. Pt, Pd, or Au, the weight of which can be varied to achieve different bandwidth-sensitivity specifications.
  • the source electrode may comprise Pd, Pt, or Au in order to provide good galvanic contact.
  • the drain electrode may have a shape a portion, such as an edge portion, which can be arranged to form an actual contact with the cantilever and may comprise W or Pt-lr or conductive carbon material.
  • a suspended graphene cantilever is stamp-transferred onto a set of electrodes (source, drain, and gate), and a tunneling current from drain to source via the graphene cantilever is maintained by a feedback voltage on the gate electrode.
  • the polymer assisted stamp-transfer process is simple and substrate-insensitive.
  • the cantilever made of crystalline graphene (mono- or multi- layer) is mechanically, electrically and chemically robust, which guarantees long- term stability and reliability of the sensor.
  • the device can be composed of a mono- or multi- layer graphene cantilever with an optional extra proof mass deposit on it, a polymer stamp used to transfer and hold the graphene cantilever, a set of electrodes (source, drain, and gate) on a substrate, and a necessary feedback circuit to maintain a constant tunneling current with a controlled electrostatic attractive force between the gate electrode and the cantilever.
  • the acceleration causes an inertial force on the cantilever due to the mass of the cantilever and the optional extra proof mass.
  • the inertial force is balanced by the electrostatic force caused by the controlled voltage on the gate electrode, so that the tunneling gap between the cantilever and the drain electrode is remained constant, which results in a constant tunneling current under a given bias voltage between the drain and the source.
  • the acceleration is transduced to the feedback gate voltage.
  • the present invention offers advantages over the known prior art.
  • the accelerometer device according to the embodiments of the invention has e.g. wider bandwidth, smaller size, high sensitivity, and it is easy to integrate with semiconductor circuit when compared e.g. to a capacitive accelerometers or the piezoelectric ones, which are bulky and in addition there an expensive crystal is required.
  • the integration of the capacitive accelerometers or the piezoelectric ones with a semiconductor circuit is not easy.
  • Figure 1 illustrates an exemplary accelerometer device design for determining acceleration according to an advantageous embodiment of the invention
  • Figure 2 illustrates an exemplary accelerometer device design for determining acceleration according to another advantageous embodiment of the invention
  • Figure 3 illustrates an exemplary manufacturing method for manufacturing the accelerometer device according to an advantageous embodiment of the invention
  • Figure 4 illustrates an exemplary cantilever of the accelerometer device according to an advantageous embodiment of the invention
  • Figure 1 illustrates an exemplary accelerometer device design 100 for determining acceleration according to an advantageous embodiment of the invention, where the device 100 is an assembly of two main parts that can be made separately.
  • One part is composed of a solid substrate 1 1 having first and second surfaces 1 1A, 1 1 B, and a set of electrodes, i.e., the source electrode 15, the drain electrode 16, and the gate electrode 17 advantageously arranged on the first surface 1 1 A.
  • the width of the electrodes 15-17 is typically from 0.1 ⁇ to 50 ⁇
  • the height of the source electrode 15 is preferably lower than that of drain electrode 16 and gate electrode 17, but all typically in the range from 10 nm to 500 nm.
  • the distance between the electrodes may vary in different designs, but typically all are in the range from 0.1 ⁇ to 50 ⁇ .
  • the other part is composed of a polymer stamp 14, a mono- or multilayer graphene cantilever 12, and an optional extra proof mass 13.
  • the accelerometer is assembled by placing the polymer stamp 14 onto the substrate 1 1 in such a way that the root of the cantilever 12 is anchored on the substrate 1 1 under the polymer stamp 14, while the arm of the cantilever 12 is bent away from the substrate surface 1 1A due to the contact with the source electrode 15.
  • a gate voltage is applied on the gate electrode 17, so that the electrostatic force between the electrode 17 and the cantilever 12 is attractive force and will force (pull) the cantilever towards the substrate until a tunneling gap 20 between the cantilever 12 and the edge of the drain electrode 16 is small enough (typically from 0.1 nm to 10 nm) for the electrons to tunnel through the tunneling gap 20.
  • a small bias voltage (typically from 0.01 V to 10 V) is applied from the drain electrode 16 to the source electrode 15, so that the tunneling current has a net flow from the drain electrode 16 to the source electrode 15. This tunneling current is maintained to a chosen constant value (typically from 0.1 nA to 10 nA) through a feedback circuit (not shown) by controlling the gate voltage on the gate electrode 17.
  • the feedback circuit can be a simple PID controller or a circuit with more comprehensive features such as temperature compensation. Depending on the target application, such a feedback circuit can be built in the form of a PCB module, an ASIC chip, or even integrated on the same substrate 1 1.
  • the materials used for the electrodes 15-17 can be different metals.
  • the source electrode 15 is preferably made of Pd, Pt, or Au.
  • Hard metals (preferably W or Pt-lr) or conductive carbon materials are preferred for the edge or other contact portion of the drain electrode 16 for better long-term stability.
  • the edge of the drain electrode 16 can be designed to be a straight line or various curves.
  • the optional proof mass 13 can be any inert materials (preferably Pt, Pd, or Au) that stick well on the cantilever 12, and the weight can be designed easily to achieve different bandwidth-sensitivity specifications. In general, lower proof mass weight means higher bandwidth and less sensitivity; higher proof mass weight means lower bandwidth and more sensitivity.
  • the polymer stamp 14 is made of photosensitive polymers (preferably commercial photoresists from AZ series or SU-8 series) or e- beam sensitive polymers (preferably commercial PMMA or MMA-MAA copolymer), so that it can be patterned with photolithography or e-beam lithography.
  • the graphene cantilever 12 can be either monolayer or multilayer, from any graphene sources (e.g., exfoliated flakes, CVD wafers). The profile of the cantilever 12 can be patterned into any desired shapes by oxygen plasma etching, as explained below in Figure 3.
  • Figure 2 illustrates an exemplary accelerometer device design 100 for determining acceleration according to another advantageous embodiment of the invention, which is a variant version of the first embodiment shown in Figure 1.
  • the substrate is marked as 21 having first and second surfaces 21 A, 21 B.
  • the mono- or multilayer graphene cantilever is marked as 22.
  • the optional proof mass is marked as 23.
  • the polymer stamp is marked as 24.
  • the source, drain, gate electrodes are marked as 25, 26, 27, respectively. Most of the above description, numbers and features for the first embodiment are still valid. The differences in relation to the device illustrated in Figure 1 are as follow.
  • the height of the source electrode 25 is higher than the drain electrode 26 and the gate electrode 27.
  • the root or the first end 22A of the cantilever 22 is anchored not on the substrate, but on the source electrode 25.
  • FIG. 3 illustrates an exemplary manufacturing method for manufacturing the accelerometer device 100 of the polymer stamp with graphene cantilever and proof mass according to an advantageous embodiment of the invention.
  • the accelerometer 100 in the embodiment is an assembly of two main parts that are made separately. The fabrication of the substrate with electrodes on it can be done with normal photolithography and lift-off.
  • a mono- or multi-layer graphene flake 37 is located on a substrate 31 with a sacrificial layer 32.
  • the graphene flake 37 may come from exfoliated natural graphite, transferred CVD graphene, or original CVD graphene grown on Ni coated Si.
  • the graphene flake 37 is then cut to a designed cantilever shape (not necessarily rectangular but also other shapes can also be utilized) via photolithography or e-beam lithography followed by oxygen plasma etching.
  • the Au proof mass 38 is deposit on the cantilever 37 via another photolithography or e-beam lithography followed by standard lift-off.
  • the photo resist or e-beam resist 33 is spun coat and then patterned into the designed shape shown in Fig 3.
  • the stamp 36 has a pick-up hole 34 in it, and a few weak links 35 around it.
  • the width and length of the stamp 36 is typically in the range from 5 ⁇ to 500 ⁇ , with a thickness typically in the range from 0.1 m to 10 ⁇ .
  • the diameter of the hole 34 is typically in the range from 1 ⁇ to 50 ⁇ .
  • the shape of the graphene cantilever is designable and can vary.
  • Two more advantageous and exemplary embodiments on the cantilever design are shown in Figure 4.
  • the cantilever 471 is perforated with an array of holes 491 , so that the spring constant and mass of the cantilever 471 can be reduced.
  • the cantilever 472 is in addition round- edged to reduce the risk of electron emission or corona discharge on sharp corners.
  • the extra proof mass 481 and 482 are optional, and the polymer 461 and 462 are parts of the stamps in connection with the cantilevers 471 and 472, respectively.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Pressure Sensors (AREA)

Abstract

Un accéléromètre (100) comprend un cantilever ancré à un substrat (11) et une électrode de source (15), une électrode de drain (16) et une électrode de grille (17) disposées sur le substrat (11). L'électrode de drain (16) et le cantilever (12) sont agencés de sorte qu'un espace de tunnellisation (20) est formé entre l'électrode de drain (16) et le cantilever (12) afin de permettre un courant de tunnellisation sur l'espace de tunnellisation (20). Le courant de tunnellisation est maintenu sur la constante d'espace de tunnellisation par commande de la tension de grille appliquée sur l'électrode de grille (17) de sorte qu'une force électrostatique entre l'électrode de grille (17) et le cantilever (12) force le cantilever par rapport au substrat dans une position telle que le courant de tunnellisation est maintenu constant. La tension de grille appliquée sur l'électrode de grille (17) est proportionnelle à l'accélération, après quoi l'accélération est déterminée en fonction de la tension de grille appliquée.
PCT/FI2017/050652 2016-09-14 2017-09-13 Dispositif accéléromètre et procédé de fabrication du dispositif accéléromètre Ceased WO2018050965A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US201662394256P 2016-09-14 2016-09-14
US62/394,256 2016-09-14

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WO2018050965A1 true WO2018050965A1 (fr) 2018-03-22

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111693734A (zh) * 2020-06-11 2020-09-22 南方科技大学 一种隧穿型加速度传感器及包含其的加速度计和用途
US20240120389A1 (en) * 2017-10-13 2024-04-11 Wayne State University Method for fabricating wafer scale/nano submicron gap electrodes and arrays via photolithography

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5293781A (en) * 1987-11-09 1994-03-15 California Institute Of Technology Tunnel effect measuring systems and particle detectors
US5563344A (en) * 1992-10-28 1996-10-08 California Institute Of Technology Dual element electron tunneling accelerometer
US6580138B1 (en) * 2000-08-01 2003-06-17 Hrl Laboratories, Llc Single crystal, dual wafer, tunneling sensor or switch with silicon on insulator substrate and a method of making same
EP1564183A2 (fr) * 2004-02-13 2005-08-17 Zyvex Corporation Microconnecteurs et microassemblage non motorisé les utilisant
WO2005112126A1 (fr) * 2004-05-14 2005-11-24 Chalmers Intellectual Property Rights Ab Dispositif nanotube électromécanique à effet tunnel comprenant une source, un drain et une porte

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5293781A (en) * 1987-11-09 1994-03-15 California Institute Of Technology Tunnel effect measuring systems and particle detectors
US5563344A (en) * 1992-10-28 1996-10-08 California Institute Of Technology Dual element electron tunneling accelerometer
US6580138B1 (en) * 2000-08-01 2003-06-17 Hrl Laboratories, Llc Single crystal, dual wafer, tunneling sensor or switch with silicon on insulator substrate and a method of making same
EP1564183A2 (fr) * 2004-02-13 2005-08-17 Zyvex Corporation Microconnecteurs et microassemblage non motorisé les utilisant
WO2005112126A1 (fr) * 2004-05-14 2005-11-24 Chalmers Intellectual Property Rights Ab Dispositif nanotube électromécanique à effet tunnel comprenant une source, un drain et une porte

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20240120389A1 (en) * 2017-10-13 2024-04-11 Wayne State University Method for fabricating wafer scale/nano submicron gap electrodes and arrays via photolithography
CN111693734A (zh) * 2020-06-11 2020-09-22 南方科技大学 一种隧穿型加速度传感器及包含其的加速度计和用途

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