WO2016071576A1 - Capteur de pression micromécanique en surface et procédé de fabrication de celui-ci - Google Patents

Capteur de pression micromécanique en surface et procédé de fabrication de celui-ci Download PDF

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Publication number
WO2016071576A1
WO2016071576A1 PCT/FI2015/050775 FI2015050775W WO2016071576A1 WO 2016071576 A1 WO2016071576 A1 WO 2016071576A1 FI 2015050775 W FI2015050775 W FI 2015050775W WO 2016071576 A1 WO2016071576 A1 WO 2016071576A1
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WO
WIPO (PCT)
Prior art keywords
bottom electrode
pressure
cavity
substrate
electrode
Prior art date
Application number
PCT/FI2015/050775
Other languages
English (en)
Inventor
Jaakko Saarilahti
Original Assignee
Teknologian Tutkimuskeskus Vtt Oy
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 Teknologian Tutkimuskeskus Vtt Oy filed Critical Teknologian Tutkimuskeskus Vtt Oy
Publication of WO2016071576A1 publication Critical patent/WO2016071576A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
    • G01L9/0041—Transmitting or indicating the displacement of flexible diaphragms
    • G01L9/0072—Transmitting or indicating the displacement of flexible diaphragms using variations in capacitance
    • G01L9/0073—Transmitting or indicating the displacement of flexible diaphragms using variations in capacitance using a semiconductive diaphragm
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
    • G01L9/0041—Transmitting or indicating the displacement of flexible diaphragms
    • G01L9/0042—Constructional details associated with semiconductive diaphragm sensors, e.g. etching, or constructional details of non-semiconductive diaphragms

Definitions

  • the invention relates to a capacitive pressure sensor according to the preamble of claim 1 and a method for manufacturing the same.
  • micromechanical pressure sensors are categorized in two classes according to their manufacturing method.
  • a pressure sensor is categorized as a surface micromechanical sensor if it is manufactured using surface micromechanical techniques, while the term bulk micromechanical device is used if the fabrication of the sensor is based on the older bulk micromechanical technique.
  • pressure sensors are also categorized in two classes depending on whether the sensor is responsive to a differential pressure or an absolute pressure.
  • a typical pressure sensor comprises a top electrode, bottom electrode and a cavity between them. The pressure is detected in the change of capacitance between the top and bottom electrodes caused by bending of at least one of the electrodes.
  • inaccuracies and mounting problems with encapsulated surface micromachined sensors are mechanical forces caused by mounting or external temperature changes.
  • the present patent application discloses a novel construction for a surface micromechanical pressure sensor and a method for manufacturing the same.
  • the invention is based on creating a floating bottom electrode for eliminating the mechanical stresses inside the MEMS chip and between the joint of the chip and PCB-board.
  • the back electrode is used as a second sensing electrode.
  • the sensor chip is formed as an elongated structure such that the actual sensing end of this structure is not attached to the frame of the sensor.
  • the pressure sensor according to the invention is characterized by what is stated in the characterizing part of claim 1.
  • the invention offers significant benefits.
  • the invention makes it possible decrease mechanical stresses both inside the sensor structure and between the sensor structure and the frame to which the sensor structure is mounted, e.g. PCB -board.
  • PCB PCB-board
  • Fig. 1 shows a typical design of a conventional surface micromechanical MEMS pressure sensor element as a cross section.
  • Fig. 2 shows a cross section of a conventional surface micromechanical MEMS pressure sensor element.
  • Fig. 3 shows cross section of a pressure sensor element with floating back electrode in accordance with the invention.
  • Fig. 4 shows cross section of the back-opened pressure sensor element with bending back electrode in accordance with the invention.
  • Fig. 6 shows a sensor structure layout for on PCB using stress eliminating acpect ration in accordance with the invention.
  • Bottom insulator e.g. Silicon oxide
  • Bottom electrode e.g. Polysilicon or metal
  • Sacrificial oxide e.g. Silicon oxide
  • Top contact pad (e.g. aluminum)
  • External pressure e.g. air pressure
  • the invention relates to methods for compensating the temperature dependences and enhancing sensitivity and installing of pressure sensors made with MEMS technology.
  • the main sources for inaccuracies and mounting problems with encapsulated surface micromachined sensors are mechanical forces caused by mounting or external temperature changes.
  • the pressure sensor element 33 comprises a top electrode 6, bottom electrode 3 and a cavity 5 between them and the pressure is detected in the change of capacitance between the top 6 and bottom electrodes 3 caused by bending of at least one of the electrodes.
  • the chip size is typically 0.5 mm 2 - 4.0 mm 2
  • the thickness of the sensor chip is defined by the silicon substrate, which could be thinned down to less than 100 ⁇ .
  • the thickness of the active sensor structure is less than 5 ⁇ .
  • the pressure sensor structure 12 is constructed of an array of surface micromechanical, capacitive pressure sensor elements 33
  • each element 33 is about 10 - 500 ⁇ depending on the top membrane material, the mechanical stress of the top membrane, the size of the sensor gap and the measured pressure range.
  • the sensor may include an internal oxide reference capacitor for temperature compensation.
  • One aspect of the invention in accordance with figure 3 relates to releasing the bottom electrode 3 during the etching phase of the sensor cavity 5 e.g. in accordance with the method described in EP01982512.
  • both the top 6 and bottom electrodes 3 will be of a porous polycrystalline silicon layer or functionally equivalent material, whereby a second cavity 11 may be formed between the bottom electrode and the substrate 1, in figure 3 below the bottom electrode 3. Therefore the bottom electrode 3 will be encapsulated within or on the border of the cavity 5 but suspended from its edges to the supporting structure 4. Thereby the bottom electrode 3 will not be affected by the external, measureable pressure, and hence it is being inactive to the pressure measurement.
  • the bottom electrode 3 is enclosed in the same pressure as the first cavity 5 by forming a second cavity 11 between the bottom electrode 3 and the substrate 1.
  • the mechanically released floating bottom electrode 3 is independent from the temperature stresses caused by different temperature coefficients in different layers and stresses caused by mounting, therefore the bottom electrode 3 is also inactive to the pressure to be measured, whereby the pressure measurement is performed by the top electrode 6 only as designed.
  • one additional measure is to open the silicon frame 1 from the backside by deep etching.
  • the bottom electrode 3 of the sensor structure 12 will be released until the bottom electrode 3 in order to form a pressure port 34 for the bottom electrode 3.
  • the bottom electrode 3 will bend under the influence of the external pressure 10, whereby also the bottom electrode 3 acts as a sensing element. So,the bottom electrode 3 is opened to the same pressure as the top electrode 6 by forming a pressure port 34 from the bottom electrode 3 to the ambient space.
  • a fourth embodiment of the invention includes modifying the aspect ratio (length/width) of the silicon sensor in order to compensate for the mounting stresses.
  • the part sensitive of the pressure of the sensor structure 12 is positioned in one end S of the sensor chip 26 and electric contacts 27 to the second end.
  • the passive silicon frame 28 between the first S and second end M is thinned by deep etching as narrow as possible such that the aspect ratio between the width 24 of the passive silicon frame 28 and the width 25 of the sensor S (24/25) is small .
  • the effectiveness of the thinned passive silicon frame depends on the aspect ratio which should generally be smaller than 1 :5.
  • the electric conductors between the sensing element S and contacts 27 are positioned on the surface of this passive silicon part 28.
  • the sensor chip 26 with this layout is attached to a frame from the second end M whereby the part S sensitive the pressure is in the other, first end S.
  • the elongated, thinned part 28 between the ends eliminates the stresses caused by mounting in the sensing part S of the structure 26.
  • top electrode (6) electrically isolated and spaced apart by a first cavity (5) from said bottom electrode (3), the top electrode (6) is deformable under the pressure (10) to be measured
  • Paragraph 2 The sensor structure (12) of Paragraph 1, characterized in that the bottom electrode (3) is concealed in the same pressure as the first cavity (5) by forming a second cavity (11) between the bottom electrode (3) and the substrate (1).
  • Paragraph 3 The sensor structure (12) of Paragraph 1, characterized in that the bottom electrode (3) is opened to the same pressure as the top electrode (6) by forming a pressure port (34) from the bottom electrode (3) to the ambient space.
  • Paragraph 7 A method for forming a capacitive surface micro mechanical pressure sensor structure (12) including at least one sensor element (33), in which method includes the following steps: forming a bottom electrode (3) on a substrate (1) such that it is in a mechanical connection with the substrate (1), and
  • top electrode (3) electrically isolated and spaced apart by a cavity (6) from said bottom electrode (3), which top electrode (6) is deformable under the pressure (10) to be measured, characterized in that releasing the bottom electrode (3) from the substrate (1), advantageously at least essentially in the vicinity of the cavity (5).
  • Paragraph 8 The method of Paragraph 7, characterized by concealing the bottom electrode (3) in the same pressure as the first cavity (5) by forming a second cavity (11) between the bottom electrode (3) and the substrate (1) by forming the bottom electrode (3) of porous polycrystalline silicon and using this porous material (3) for etching the second cavity (11).
  • Paragraph 9 The method of Paragraph 7, characterized by opening that the bottom electrode (3) the same pressure as the top electrode (6) (fig. 4) outside the cavity (5) by forming a pressure port (34) from the bottom electrode (3) to the ambient space.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Measuring Fluid Pressure (AREA)
  • Pressure Sensors (AREA)

Abstract

La présente invention concerne une structure formant capteur de pression micromécanique en surface du type capacitif (12) comprenant au moins un élément de capteur (33), chaque élément de capteur (33) comportant un substrat (1), une électrode inférieure (3) en connexion mécanique avec le substrat (1), et au moins une électrode supérieure (6) isolée électriquement et espacée par une première cavité (5) par rapport à ladite électrode inférieure (3), l'électrode supérieure (6) étant déformable sous l'effet de la pression (10) devant être mesurée. Conformément à l'invention, l'électrode inférieure (3) est libérée (11, 34) du substrat (1) au moins essentiellement à proximité de la cavité (5).
PCT/FI2015/050775 2014-11-07 2015-11-09 Capteur de pression micromécanique en surface et procédé de fabrication de celui-ci WO2016071576A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI20145977 2014-11-07
FI20145977 2014-11-07

Publications (1)

Publication Number Publication Date
WO2016071576A1 true WO2016071576A1 (fr) 2016-05-12

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Application Number Title Priority Date Filing Date
PCT/FI2015/050775 WO2016071576A1 (fr) 2014-11-07 2015-11-09 Capteur de pression micromécanique en surface et procédé de fabrication de celui-ci

Country Status (1)

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WO (1) WO2016071576A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106813811A (zh) * 2017-01-20 2017-06-09 南京大学 一种高灵敏度电容型柔性压力传感器
CN113790833A (zh) * 2021-09-16 2021-12-14 武汉敏声新技术有限公司 一种压力传感器

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4111119A1 (de) * 1991-04-03 1992-10-08 Univ Chemnitz Tech Stapelbare mikromechanische kapazitive druckmesszelle
DE4441903C1 (de) * 1994-11-24 1996-03-21 Siemens Ag Drucksensor
WO2004063089A2 (fr) * 2003-01-13 2004-07-29 Indian Institute Of Technology - Delhi (Iit) Composant a microstructure evidee et procede de fabrication de ce composant
EP1982512A1 (fr) 2006-02-10 2008-10-22 Eastman Kodak Company Imprimante a calibrage automatique et procede de calibrage pour imprimante
DE102009000056A1 (de) * 2009-01-07 2010-07-08 Robert Bosch Gmbh Sensorelement zur kapazitiven Differenzdruckerfassung
US20130233086A1 (en) * 2012-03-08 2013-09-12 Nxp B. V. Mems capacitive pressure sensor

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4111119A1 (de) * 1991-04-03 1992-10-08 Univ Chemnitz Tech Stapelbare mikromechanische kapazitive druckmesszelle
DE4441903C1 (de) * 1994-11-24 1996-03-21 Siemens Ag Drucksensor
WO2004063089A2 (fr) * 2003-01-13 2004-07-29 Indian Institute Of Technology - Delhi (Iit) Composant a microstructure evidee et procede de fabrication de ce composant
EP1982512A1 (fr) 2006-02-10 2008-10-22 Eastman Kodak Company Imprimante a calibrage automatique et procede de calibrage pour imprimante
DE102009000056A1 (de) * 2009-01-07 2010-07-08 Robert Bosch Gmbh Sensorelement zur kapazitiven Differenzdruckerfassung
US20130233086A1 (en) * 2012-03-08 2013-09-12 Nxp B. V. Mems capacitive pressure sensor

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106813811A (zh) * 2017-01-20 2017-06-09 南京大学 一种高灵敏度电容型柔性压力传感器
CN106813811B (zh) * 2017-01-20 2019-04-05 南京大学 一种高灵敏度电容型柔性压力传感器
CN113790833A (zh) * 2021-09-16 2021-12-14 武汉敏声新技术有限公司 一种压力传感器

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