GB2034970A - Semiconductor pressure transducer - Google Patents

Semiconductor pressure transducer Download PDF

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Publication number
GB2034970A
GB2034970A GB7934401A GB7934401A GB2034970A GB 2034970 A GB2034970 A GB 2034970A GB 7934401 A GB7934401 A GB 7934401A GB 7934401 A GB7934401 A GB 7934401A GB 2034970 A GB2034970 A GB 2034970A
Authority
GB
United Kingdom
Prior art keywords
pressure transducer
passivation layer
silicon
pressure
layer
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.)
Withdrawn
Application number
GB7934401A
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.)
Hitachi Ltd
Original Assignee
Hitachi Ltd
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 Hitachi Ltd filed Critical Hitachi Ltd
Publication of GB2034970A publication Critical patent/GB2034970A/en
Withdrawn legal-status Critical Current

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Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01LMEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L19/00Details of, or accessories for, apparatus for measuring steady or quasi-steady pressure of a fluent medium insofar as such details or accessories are not special to particular types of pressure gauges
    • G01L19/0061Electrical connection means
    • G01L19/0084Electrical connection means to the outside of the housing
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01LMEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L19/00Details of, or accessories for, apparatus for measuring steady or quasi-steady pressure of a fluent medium insofar as such details or accessories are not special to particular types of pressure gauges
    • G01L19/14Housings
    • G01L19/147Details about the mounting of the sensor to support or covering means
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01LMEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L9/00Measuring 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
    • G01L9/0041Transmitting or indicating the displacement of flexible diaphragms
    • G01L9/0051Transmitting or indicating the displacement of flexible diaphragms using variations in ohmic resistance
    • G01L9/0052Transmitting or indicating the displacement of flexible diaphragms using variations in ohmic resistance of piezoresistive elements
    • G01L9/0054Transmitting or indicating the displacement of flexible diaphragms using variations in ohmic resistance of piezoresistive elements integral with a semiconducting diaphragm
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42Wire connectors; Manufacturing methods related thereto
    • H01L2224/47Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/48Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H01L2224/4805Shape
    • H01L2224/4809Loop shape
    • H01L2224/48091Arched
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/73Means for bonding being of different types provided for in two or more of groups H01L2224/10, H01L2224/18, H01L2224/26, H01L2224/34, H01L2224/42, H01L2224/50, H01L2224/63, H01L2224/71
    • H01L2224/732Location after the connecting process
    • H01L2224/73251Location after the connecting process on different surfaces
    • H01L2224/73265Layer and wire connectors
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/10Details of semiconductor or other solid state devices to be connected
    • H01L2924/1015Shape
    • H01L2924/10155Shape being other than a cuboid
    • H01L2924/10158Shape being other than a cuboid at the passive surface

Landscapes

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

Abstract

In a pressure transducer comprising a silicon substrate 10 having a thin diaphragm portion 10a the upper face of which contains piezoresistive elements 20 and being covered with a passivating layer 40 (eg of silicon dioxide), the lower surface of the diaphragm is provided with a balancing layer 70 (eg also of silicon dioxide) to eliminate thermally induced stresses in the diaphragm which would otherwise be caused by the difference in thermal expansion coefficients of silicon and the material of the passivating layer. <IMAGE>

Description

SPECIFICATION Semiconductor pressure transducer assembly The present invention relates to a semiconductor pressure transducer assembly, more particularly to a semiconductor pressure transducer assembly suitable for use as a pressure sensor in an automobile.
Ordinarily, as an automobile moves, fuel is injected from a fuel injection valve into air which is introduced in an intake manifold, the fuel-air mixture being taken into the inside of the engine and being ignited for combustion thereof. However, if a fixed amount of fuel is always injected irrespective of the pressure of the air which is introduced into the intake manifold, the combustion is imperfect due to a shortage of air, or combustion knock is caused due to an excess of air. In a recent automobile, the quantity of fuel injected from an electronic fuel injection apparatus or the advance angle of an electronic advance device is controlled depending on the intake airpressure which is measured in comparison with atmsopheric pressure or absolute pressure. The combustion in the engine is thereby always kept under the most suitable conditions.To perform this measurement of air pressure in the intake manifold, a semiconductor pressure transducer is widely adopted.
A need exists for pressure transducers having very small physical size and high sensitivity and reliablility, which may be installed in the intake manifold. To achieve this, miniaturized semiconductor pressure transducers have to be fabricated, in which a small-sized silicon diaphragm has a very thin diaphragm portion.
Conventionally, a passivation layer of insulating material, such as silicon dioxide (SiO2), is provided on a surface of the silicon diaphragm for protecting a piezoresistive bridge circuit constructed thereon. However, no passivation layer is provided on the other surface of the thin silicon diaphragm portion which is formed by etching from the bottom surface of the silicon substrate. In the conventional semiconductor pressure transducers having such silicon diaphragm, therefore, the zero-point of output with respect to a standard pressure fluctuates depending on ambient temperature because of strains appearing in the diaphragm portion. This is because, after a bonding process at high temperature, residual stresses are caused owing to the difference in thermal expansion coefficients between the two layers of the thin silicon diaphragm portion and the silicon dioxide passivation layer.For eliminating such residual stresses, the passivation layer should be formed very thinly on the surface of the silicon diaphragm. However, if the thickness of the passivation layer is made very thin, leakage current disadvantageously increases through pin-holes which result from the thinning of the passivation layer.
Details of the prior art can be seen from U.S. Patents 3,918,019 and 4,079,508 "Miniature absolute pressure transducer as sembly and method"; and U.S. Patent 3,397,278 "Anodic bonding".
The present invention provides a semicon ductor pressure transducer assembly for trans ducing pressure to electric signal, comprising: a a silicon diaphragm assembly having a thin pressure sensitive portion; piezoresistive ele ments diffused on one surface of said silicon diaphragm assembly, the resistance value of the piezoresistive elements varying depending on the strains appearing in the thin pressure sensitive portion in response to the pressure applied thereto; and a passivation layer of insulator lying on the surface of the silicon diaphragm assembly on which surface sia piezoresistive elements are diffused, wherein on the other surface of said silicon diaphragm assembly is formed a layer for eliminating stresses caused in the thin pressure sensitive portion due to the thermal expansion differ pence between said silicon diaphragm assem bly and said passivation layer.
An embodiment of the present invention will now be described by way of example, with reference to the accompanying drawings, wherein: Figure 1 is a sectional view of a semicon ductor pressure transducer assembly, and Figure 2 is a sectional view of an entire pressure sensor apparatus including the semi conductor pressure transducer assembly shown in Fig. 1.
Referring now to Fig. 1, on an upper sur face of a silicon diaphragm assembly 10 of single silicon crystal, strain gauge elements 20 of piezoresistor are constructed by diffu sion of impurity such as boron (B). At one end of each strain guage element 20, an incorrup tible electrode 30 such as of aluminium (Al) or of three layers of titanium (Ti), palladium (Pd) and gold (Au), is formed using an appropriate method, for example evaporation or spatter ing. On the upper surface of the processed silicon diaphragm assembly 10 built with the strain gauge elements 20 thereon, is formed a passivation layer 40 such as of silicon dioxide (SiO2). The passivation layer 40 is provided for the purpose of protecting the strain gauge elements 20 and for stability of the surface of the silicon diaphragm assembly 10.
A groove 60 is etched from a bottom sur face of the silicon diaphragm assembly 10, a pressure sensitive thin silicon diaphragm por tion 1 Oa being thereby formed. The silicon diaphragm assembly 10 therefore comprises this thin silicon diaphragm portion 1 0a and a thick silicon supporting portion lOb which surrounds the diaphragm portion 1 Oa. Onto the supporting portion 1 Ob of the silicon diaphragm assembly 10, an insulator sub strate 50 is firmly bonded, for example, using Anodic Bonding or a bonding pad of adhesive.On an inner surface of the groove 60 which is enclosed by the glass substrate 50, a passivation layer 70 of insulator material which has a thermal expansion coefficient equal to that of the silicon dioxide passivation layer 40, is formed using a method such as the C.V.D. method or spattering, preferably to the same thickness as the passivation layer 40. In a chamber defined between the silicon diaphragm assembly 10 and the glass substrate 50, is provided any desired reference pressure, for example a vacuum or a predetermined pressure reference of inactive gas.
The thermal expansion coefficient (3.2 X 10-6/ C) of the single silicon crystal of the diaphragm assembly is greater than the thermal expansion coefficient (0.48 X 10-6/ C) of silicon dioxide of the passivation layer.
Therefore, if the passivation layer of silicon dioxide were prepared only on the upper surface of the silicon diaphragm assembly, initial stresses would appear in the thin diaphragm portion owing to the difference in the thermal expansion coefficients therebetween.
And if such silicon diaphragm assembly was adopted, the zero-point characteristic of the pressure transducer would fluctuate with respect to the predetermined pressure reference, and the thermal dependency would come to 10% over a range of 100"C in ambient temperature. With the embodiment of the present invention shown in Fig. 1, however, since the passivation layers 40 and 70 are formed on both surfaces of the thin diaphragm portion 10a, the dependency upon the ambient temperature comes down to a few percent over the range of 100"C.
A further advantage of this embodiment is that the thickness of the passivation layer 40 formed on the upper surface of the silicon diaphragm assembly 10 can be made sufficient so as to provide adequate protection for the insulation of the piezoresistive elements 20, even if the diaphragm portion 1 Oa is very thin. Because the thin silicon diaphragm portion 1 0a is sandwiched between the two passivation layers 40 and 70 of silicon dioxide, the respective residual stresses are mutually eliminated by each other. A passivation layer 40 without defects such as pin-holes can thus be formed on the silicon diaphragm assembly 10.
Another advantage is that, since the silicon diaphragm assembly 10, in particular the thin diaphragm portion 10a thereof, is covered with the passivation layers 40 and 70, the silicon diaphragm assembly 10 can be protected from corruption if it is used in an active atmosphere of sulfurous acid gas. The silicon diaphragm assembly 10 of such structure, therefore, can be kept and used in a stable condition for long time.
In the embodiment described above, although an absolute pressure transducer is explained, in which a vacuum is provided on one side surface of the thin diaphragm portion 1 Oa of the silicon diaphragm assembly 10, the present invention can be applied to similar effect to a differential pressure transducer which has a pressure reference. Further, it is also obvious that silicon nitride (SiN) can be used as the passivation layers instead of silicon dioxide mentioned above.
Referring to Fig. 2, in a ceramic substrate 111, is formed a groove 11 2 in which the semiconductor pressure transducer assembly 100 is positioned, the bottom of the transducer assembly being connected to the bottom of the groove with resilient adhesive 11 3.
On an upper surface of the ceramic substrate 111, electrodes 114 are prepared at the edges of the groove 11 2, and the electrodes 114 are connected through conductive wires 11 5 such as of gold (Au) to the electrodes of the semiconductor pressure transducer assembly 100. A plastic covering member 11 6 having a pressure inlet is mounted on the upper surface of the ceramic substrate 111, covering the semiconductor pressure transducer assembly 100 and the electrodes 11 4 thereon. On the remaining part of the surface of the ceramic substrate 111, an operational amplifier 11 7 is provided for amplifying an electric signal up to a desired signal level.
Further, the ceramic substrate 111 has plural lead frames 11 8 fixed at the both sides thereof and film electrodes are formed thereon for electrical connections between the semiconductor pressure transducer assembly 100, the operational amplifier 11 7 and the lead frames. The film electrodes are not shown in Fig. 2.
The operation of the apparatus mentioned above will now be described briefly with reference to Figs. 1 and 2. If a pressure to be detected is applied in the direction indicated by an arrow in Fig. 2, the pressure is led onto the thin diaphragm portion 1 Oa of the silicon diaphragm assembly 10, and is transduced into an electric signal by the function of the piezoresistive strain gauge elements 20 thereon. This electric signal is led through the electrodes 30, the conductive wires 11 5 and the electrodes 114 to the amplifier 117, and then the amplified electric signal is led out from the lead frames 11 8.
This apparatus could be used in an autombile as described in the introduction.

Claims (10)

1. A semiconductor pressure transducer assembly for transducing pressure to electric signal, comprising: a silicon diaphragm assembly having a thin pressure sensitive portion; piezoresistive elements diffused on one surface of said silicon diaphragm assembly, the resistance value of the piezoresistive elements varying depending on the strains appearing in the thin pressure sensitive portion in response to the pressure applied thereto; and a passivation layer of insulator lying on the surface of the silicon diaphragm assembly on which surface said piezoresistive elements are diffused, wherein on the other surface of said silicon diaphragm assembly is formed a layer for eliminating stresses caused in the thin pressure sensitive portion due to the thermal expansion difference between said sil icon diaphragm assembly and said passivation layer.
2. A semiconductor pressure transducer assembly according to claim 1, wherein a groove is etched from the bottom of said silicon diaphragm assembly for defining the thin pressure sensitive portion and a thick supporting portion therefor, and said stress eliminating layer is formed on an inner surface of said groove.
3. A semiconductor pressure transducer assembly according to claim 1 or claim 2 wherein the passivation layer and the stress eliminating layer are of the same material.
4. A semiconductor pressure transducer assembly according to claim 3, wherein said passivation layer and said stress eliminating layer are formed of silicon dioxide.
5. A semiconductor pressure transducer assembly according to claim 3, wherein said passivation layer and said stress eliminating layer are formed of silicon nitride.
6. A semiconductor pressure transducer assembly according to any one of the preced ing claims, wherein said passivation layer and said stress eliminating layer are formed in thicknesses equal to each other.
7. A semiconductor pressure transducer assembly for transducing pressure to electric signal, substantially as described herein with preference to Fig. 1 of the accompanying draw ings.
8. Pressure sensor apparatus incorporating a semiconductor transducer element according to any one of the preceding claims.
9. Pressure sensor apparatus substantially as described herein with reference to Fig. 2 of the accompanying drawings.
10. An automobile fitted with pressure sensor apparatus according to claim 8 or claim 9.
GB7934401A 1978-10-06 1979-10-04 Semiconductor pressure transducer Withdrawn GB2034970A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP12254078A JPS5550668A (en) 1978-10-06 1978-10-06 Semiconductor pressure converter

Publications (1)

Publication Number Publication Date
GB2034970A true GB2034970A (en) 1980-06-11

Family

ID=14838386

Family Applications (1)

Application Number Title Priority Date Filing Date
GB7934401A Withdrawn GB2034970A (en) 1978-10-06 1979-10-04 Semiconductor pressure transducer

Country Status (6)

Country Link
JP (1) JPS5550668A (en)
AU (1) AU5117679A (en)
DE (1) DE2940497A1 (en)
FR (1) FR2438264A1 (en)
GB (1) GB2034970A (en)
IT (1) IT7926278A0 (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2229816A (en) * 1989-03-31 1990-10-03 Stc Plc Resonating element differential pressure sensor
GB2265754A (en) * 1992-03-30 1993-10-06 Awa Microelectronics Beam structure in silicon devices
AU660358B2 (en) * 1992-03-30 1995-06-22 Awa Microelectronics Pty Limited Silicon transducer
WO2003095963A2 (en) * 2002-05-06 2003-11-20 Rosemount, Inc. Barometric pressure sensor
US10156489B2 (en) * 2016-02-02 2018-12-18 Asia Pacific Microsystems, Inc. Piezoresistive pressure sensor

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS57142533A (en) * 1981-02-27 1982-09-03 Mitsubishi Electric Corp Pressure sensor
JPS6056244U (en) * 1983-09-26 1985-04-19 住友電気工業株式会社 semiconductor pressure sensor
JPS60149369A (en) * 1984-01-14 1985-08-06 Hitoshi Nagaoka Mycelial extract of ganoderma lucidum and production thereof
JPH0465643A (en) * 1990-07-05 1992-03-02 Mitsubishi Electric Corp Semiconductor pressure sensor and its manufacture

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL162254B (en) * 1968-11-29 1979-11-15 Philips Nv SEMI-CONDUCTOR DEVICE FOR CONVERSION OF MECHANICAL VOLTAGES INTO ELECTRICAL SIGNALS AND METHOD OF MANUFACTURING THIS.
US3819431A (en) * 1971-10-05 1974-06-25 Kulite Semiconductor Products Method of making transducers employing integral protective coatings and supports
JPS5217780A (en) * 1975-07-04 1977-02-09 Hitachi Ltd Pressure convertor with semi-conductor elements
JPS52127257A (en) * 1976-04-19 1977-10-25 Hitachi Ltd Displacement converter

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2229816A (en) * 1989-03-31 1990-10-03 Stc Plc Resonating element differential pressure sensor
GB2229816B (en) * 1989-03-31 1992-11-18 Stc Plc Pressure sensor
GB2265754A (en) * 1992-03-30 1993-10-06 Awa Microelectronics Beam structure in silicon devices
AU660358B2 (en) * 1992-03-30 1995-06-22 Awa Microelectronics Pty Limited Silicon transducer
GB2265754B (en) * 1992-03-30 1995-10-25 Awa Microelectronics Silicon transducer
US5682053A (en) * 1992-03-30 1997-10-28 Awa Microelectronics Pty. Limited Silicon transducer with composite beam
WO2003095963A2 (en) * 2002-05-06 2003-11-20 Rosemount, Inc. Barometric pressure sensor
WO2003095963A3 (en) * 2002-05-06 2004-04-01 Rosemount Inc Barometric pressure sensor
US10156489B2 (en) * 2016-02-02 2018-12-18 Asia Pacific Microsystems, Inc. Piezoresistive pressure sensor

Also Published As

Publication number Publication date
DE2940497A1 (en) 1980-04-10
FR2438264A1 (en) 1980-04-30
AU5117679A (en) 1980-04-17
JPS5550668A (en) 1980-04-12
IT7926278A0 (en) 1979-10-05

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