EP0970355A1 - Sonde manometrique a semi-conducteur couches minces fabriquee par lots et procede de fabrication correspondant - Google Patents

Sonde manometrique a semi-conducteur couches minces fabriquee par lots et procede de fabrication correspondant

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Publication number
EP0970355A1
EP0970355A1 EP98910183A EP98910183A EP0970355A1 EP 0970355 A1 EP0970355 A1 EP 0970355A1 EP 98910183 A EP98910183 A EP 98910183A EP 98910183 A EP98910183 A EP 98910183A EP 0970355 A1 EP0970355 A1 EP 0970355A1
Authority
EP
European Patent Office
Prior art keywords
membrane
pressure sensor
over
strain gage
pressure
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Withdrawn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
EP98910183A
Other languages
German (de)
English (en)
Inventor
Denny K. Miu
Weilong Tang
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.)
Integrated Micromachines Inc
Original Assignee
Integrated Micromachines Inc
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
Priority claimed from US08/822,839 external-priority patent/US5821596A/en
Priority claimed from US08/937,859 external-priority patent/US6700174B1/en
Application filed by Integrated Micromachines Inc filed Critical Integrated Micromachines Inc
Publication of EP0970355A1 publication Critical patent/EP0970355A1/fr
Withdrawn legal-status Critical Current

Links

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
    • G01L9/0075—Transmitting or indicating the displacement of flexible diaphragms using variations in capacitance using a ceramic diaphragm, e.g. alumina, fused quartz, glass
    • 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
    • G01L9/0051—Transmitting or indicating the displacement of flexible diaphragms using variations in ohmic resistance
    • 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

Definitions

  • the present invention relates to a pressure sensor which undergoes physical movement in response to an applied external force.
  • This invention also relates to techniques for fabricating such a pressure sensor.
  • Fig. 1A is a top view of a conventional silicon micromachined piezo-resistive pressure sensor 1.
  • Pressure sensor 1 is fabricated on a silicon substrate 2 having an area of 2 mm by 2 mm and a thickness on the order of 500 ⁇ m.
  • substrate 2 is fabricated to include a frame 2a, an annular diaphragm 2b and a circular platform 2c.
  • Diaphragm 2b is etched to have a thickness on the order of 10 ⁇ m, while frame 2a and platform 2c remain at a thickness of approximately 500 ⁇ m.
  • the deformation of substrate 2 will be concentrated within the annular diaphragm 2b, thereby increasing the sensitivity of pressure sensor 1.
  • Each of these Wheatstone bridge circuits includes a plurality of contact pads 4, a plurality of piezo-resistive elements 5, and conductive traces for connecting the pads 4 and piezo-resistive elements 5.
  • Piezo-resistive elements 5 are formed by ion implanting impurity regions into the annular diaphragm 2b. The resistances of piezo-resistive elements 5 change in response to mechanical stresses applied to the crystalline substrate 2. More specifically, the resistances of piezo-resistive elements 5 change in response to compression and dilation of diaphragm 2b.
  • This annular diaphragm 2b and the position of piezo- resistive elements 5 provides a 25 to 50 times increase in the gauge factor, such that pressure sensor 1 can provide an output voltage on the order or 2 to 3 mV/V when designed for full range of differential pressure on the order of a 4 inch water column (WC) .
  • pressure sensor 1 has typically been used for high pressure range sensing applications in the automobile world.
  • Such applications include, for example, measurements of manifold absolute pressure,
  • the effectiveness of pressure sensor 1 is determined by a combination of two physical effects, which can be explained in terms of a mechanical amplifier cascaded with an electrical amplifier.
  • the mechanical amplifier is diaphragm 2b which converts pressure into displacement.
  • the electrical amplifier is the combination of piezo-resistive elements 5 and Wheatstone bridge circuits 3a-3d, which convert displacement into output voltage.
  • platform 2c acts as a seismic mass which causes an excessive amount of dynamic deflection in response to shock and vibration (i.e., noise) .
  • Platform 2c can further cause an excessive amount of static deflection in response to gravity, thereby making the sensor highly sensitive to mounting positions) .
  • the operation of pressure sensor 1 can be affected by the position and environment in which pressure sensor 1 is mounted.
  • piezo-resistive elements 5 act as pyro- resistors, thereby making pressure sensor 1 extremely sensitive to temperature changes.
  • sophisticated temperature compensation schemes must typically be used with pressure sensor 1. It is typical that even after such temperature compensation is provided, the temperature effects are on the order of 1 to 2 percent of full range.
  • annular diaphragm 2b is typically very fragile, thereby rendering pressure sensor 1 prone to damage during transportation, handling and assembly.
  • the shape of annular diaphragm 2b limits the linear elastic range the diaphragm 2b.
  • the performance of pressure sensor 1 can be nonlinear if the deformation of diaphragm 2b exceeds the linear elastic range of the silicon diaphragm.
  • FIG. IB is a cross sectional view of a conventional capacitive differential pressure sensor 20 which is used to measure pressure.
  • Pressure sensor 20 is formed by sandwiching an etched silicon diaphragm 29 (which is etched from a silicon substrate 28) between an upper glass plate 30 and a lower glass plate 27.
  • Pressure ports 25 and 26 are formed through the upper and lower glass plates 30 and 27, respectively, to vent silicon diaphragm 29.
  • Aluminum is sputtered to the inner surfaces of the upper and lower glass plates to form fixed capacitor plates 23 and 24.
  • Connectors 21 and 22 extend from plates 23 and 24, respectively, along the walls of pressure ports 25 and 26, to the outer surfaces of the upper and lower glass plates 30 and 27.
  • the silicon diaphragm 29 forms a movable center capacitive plate of the sensor 20 in a configuration similar to a capacitive potentiometer.
  • a positive pressure applied to pressure port 25 causes the silicon diaphragm 29 to deflect toward the lower glass plate 27, thereby increasing the capacitance between diaphragm 29 and plate 24, while decreasing the capacitance between diaphragm 29 and plate 23.
  • the imbalance which is directly proportional to pressure, is detected by an electronic circuit .
  • Pressure sensor 20 to exhibits the following disadvantages.
  • silicon diaphragm 29, being relatively thick (i.e., having a thickness of at least about 5 microns) can experience an excessive amount of dynamic deflection in response to shock and vibration.
  • silicon diaphragm 29 is made thinner for low pressure applications (i.e., a thickness of approximately 5 microns) it is difficult to fabricate a substantially planar diaphragm.
  • a non-planar diaphragm can result in erroneous capacitance measurements.
  • silicon diaphragm 29 is made thinner for low pressure applications, the diaphragm becomes very fragile, thereby rendering pressure sensor 20 prone to damage during transportation, handling and assembly.
  • the present invention provides a sensitive pressure sensor which includes a flexible membrane, such as low-stress silicon nitride, which is supported by a semiconductor frame.
  • the flexible membrane extends over the frame, and an inherent tensile stress is present in the membrane.
  • a thin film strain gage material such as nickel-chrome, is deposited over the flexible membrane to form one or more variable resistance resistors over the flexible membrane.
  • an external pressure such as a dynamic pressure drop due to an air flow
  • the membrane is deformed out of plane.
  • the variable resistance resistors increase in length, and thereby increase in resistance.
  • the increase in resistance is monitored by an electronic circuit, such as a Wheatstone bridge circuit.
  • the pressure sensor of the present invention is immune to shock, vibration, and orientation.
  • the resistance of the strain gage material is based purely on geometric effect, such that the pressure sensor of the present invention is very temperature stable.
  • the flexible membrane undergoes a relatively large deformation (in comparison with sensor 1) for a given applied pressure differential This provides a relatively sensitive and stable sensor, suitable for low pressure applications.
  • the flexible membrane is made of a strong material which can withstand a large applied pressure differential. Because the membrane is under tensile stress, the out-of-plane displacement is linearly proportional to the applied pressure.
  • FIG. 1A is a top view of a conventional silicon micromachined piezo-resistive pressure sensor
  • Fig. 4 is a cross sectional view of the pressure sensor of Fig. 2 along section line 4-4 of Fig. 2 ;
  • Figs. 5A-5G are cross sectional views illustrating the pressure sensor of Figs. 2-4 during selected processing steps;
  • Fig. 8 is a bottom view of the upper over-pressure stopper structure of Fig. 7;
  • Fig. 9 is a cross sectional view illustrating a capacitive pressure sensor in accordance with an alternate embodiment of the present invention.
  • Fig. 10B is a top view of the air flow tubes of the pressure sensor assembly of Fig. 10A;
  • Fig. 11 is a cross sectional view of a pressure sensor which is adapted for use as temperature sensor in accordance with one embodiment of the invention.
  • Fig. 12 is schematic diagram of a pressure sensor which is adapted for use as vacuum sensor in accordance with another embodiment of the invention.
  • Figs. 13, 14 and 15 are cross sectional views of pressure sensors which are adapted for uses as pitot tubes in accordance with alternative embodiments of the invention; and Fig. 16 is a cross sectional view of a pressure sensor which is modified to operate as a chemical detector in accordance with another embodiment of the invention.
  • Fig. 2 is a top view of a pressure sensor 200 in accordance with one embodiment of the present invention.
  • Fig. 3 is a bottom view of pressure sensor 200.
  • Fig. 4 is a cross sectional view of pressure sensor 200 along section line 4-4 of Fig. 2.
  • Figs. 2-4 use the illustrated X-Y-Z coordinate system.
  • Pressure sensor 200 includes semiconductor frame 201, flexible membrane 202, electrically conductive traces 211-214, electrically conductive pads 211a-214a, and strain gage resistors 221-224.
  • Semiconductor frame 201 is a monocrystalline semiconductor material. In the described example, frame 201 is monocrystalline silicon having a ⁇ 100> orientation. However, frame 201 can be made of other semiconductor materials in other embodiments. Frame 201 has dimensions of approximately 0.6 cm along the X-axis, 0.6 cm along the Y-axis, and 400 ⁇ m along the Z-axis. A centrally located opening 203 extends completely through frame 201. Frame 201 supports a low- stress, flexible membrane
  • membrane 202 is a silicon rich, silicon nitride membrane which extends over opening 203 at the upper surface of frame 202.
  • the silicon nitride membrane 202 has a thickness of approximately 2,000 Angstroms.
  • membrane 202 can be made of other materials, such as polyimide .
  • the intrinsic tensile stress of membrane 202 tends to hold membrane 202 irA ⁇ "plane which is parallel to the X-Y plane.
  • membrane 202 is compliant along the Z-axis.
  • membrane 202 deforms to move along the Z-axis.
  • the forces required to deform membrane 202 are on the order of 250 ⁇ N.
  • the amount of deformation of membrane 202 along the Z-axis in the presence of these forces is approximately 0.5 ⁇ m.
  • Membrane 202 provides for a greatly improved mechanical amplification factor with respect to the conventional piezo-resistive pressure sensor 1 (Fig. 1A) . Because membrane 202 is pre-stressed, the membrane acts more like a taut cable in a suspension bridge than a cantilever beam.
  • the out-of-plane stiffness of membrane 202 is not a function of Young' s modulus or the cross- sectional inertia of the membrane material, but rather, is a function of the well controlled inherent tensile stress of membrane 202.
  • Strain gage resistors 221-224 are formed over the exposed surface of membrane 202. Strain gage resistors are defined as resistors formed from a strain gage material. Strain gage material is defined to mean electrically conductive material which has a resistance which is proportional to the length of the material and inversely proportional to the cross sectional area of the material. In the described example, strain gage resistors are made of nickel-chrome (which is approximately 80 percent nickel and 20 percent chrome) . Other strain gage materials include chrome or titanium.
  • resistors 223 and 224 could be fabricated using a different material (including a non strain gage material) than the strain gage material used to fabricate strain gage resistors 221-222.
  • resistors 223 and 224 are designed to have the same resistance as strain gage resistors 221 and 222 when membrane 202 is not deformed along the Z-axis.
  • Strain gage resistors 221 and 222 are formed in a semi-circular, serpentine pattern as illustrated in Fig. 2. Strain gage resistors 221 and 222 are formed entirely over the portion of membrane 202 which is not directly connected to frame 201.
  • strain gage resistors 221 and 222 are formed over the portion of membrane 202 which is located over the opening 203 of frame 201. (Opening 203 is shown by the dashed line in Fig. 2.) As a result, strain gage resistors 221 and 222 increase in length and decrease in cross sectional area as membrane 202 moves out of the X-Y plane. As described in more detail below, the resistances of these strain gage resistors 221 and 222 increase under these conditions. Strain gage resistors 223 and 224 are formed in a linear serpentine pattern as illustrated in Fig. 2. Strain gage resistors 223 and 224 are formed entirely over the portion of membrane 202 which is directly connected to frame 202.
  • strain gage resistors 223 and 224 are formed directly over frame 203. As a result, strain gage resistors 223 and 224 do not expand in any significant manner as membrane 202 moves out of the X-Y plane.
  • Electrically conductive traces 211-214 are formed from a low-resistance material, such as a metal or metal alloy. In the described example, traces 211-214 are formed from gold or a gold alloy having a thickness of approximately 2000 Angstroms and a width of approximately 100 ⁇ m. As a result, the resistances of traces 211-214 are much less than the resistances of strain gage resistors 221-224. Traces 211-214 couple strain gage resistors 221-224 to form a Wheatstone bridge circuit.
  • trace 211 couples a first terminal of resistor 223 to a first terminal of resistor 221.
  • Trace 212 couples a second terminal of resistor 223 to a first terminal of resistor 222.
  • Trace 213 couples a second terminal of resistor 222 to a first terminal of resistor 224.
  • Trace 214 couples a second terminal of resistor 221 to a second terminal of transistor 224.
  • Pads 211a-214a are formed at the ends of traces 211-214, respectively, thereby providing connection points for the Wheatstone bridge circuit.
  • Pressure sensor 200 is fabricated as follows in accordance with one embodiment of the present invention.
  • Figs. 5A-5G illustrate pressure sensor 200 during particular processing steps.
  • monocrystalline silicon substrate 201 is cleaned.
  • a layer of silicon nitride 202 is deposited over the outer surfaces of substrate 201.
  • the silicon nitride layer 202 has a thickness of approximately 2000 A, although other thicknesses are possible.
  • a photoresist layer 501 is then deposited over the silicon nitride layer 202.
  • the photoresist layer 501 is patterned to define an opening 502. In the described method, this opening 502 has a square shape.
  • a plasma etch is performed to remove the portion of the silicon nitride layer 202 which is exposed by the opening 502.
  • a KOH etch is then performed on the resulting structure. As shown in Fig. 5C, the KOH etch forms opening 203, which extends through substrate 201, thereby causing the substrate to form frame 201. Because the KOH etch does not attack the silicon nitride layer 202, the silicon nitride layer 202 remains as a membrane across opening 203. This membrane 202 has an inherent tensile stress due to the method of fabrication.
  • a layer of gold 215 having a thickness of approximately 2000 A is evaporated (or sputtered) over the entire lower surface of the silicon nitride layer 202.
  • This gold layer 215 is then patterned and etched in accordance with conventional processing techniques to form traces 211-214 as illustrated in Fig. 5E.
  • a layer of strain gage material 216 e.g., nickel- chrome
  • This layer of strain gage material 216 is then patterned and etched in accordance with conventional processing techniques, thereby forming strain gage resistors 221-224 and completing the fabrication of pressure sensor 200 (Fig. 5G) .
  • Etchants other than KOH can be used in other embodiments of the invention.
  • Figs. 5A-5G illustrate the fabrication of a single pressure sensor 200
  • many pressure sensors similar to pressure sensor 200 can be simultaneously (i.e., batch) fabricated on a silicon wafer.
  • These batch- fabricated pressure sensors can be cut into individual pressure sensors in accordance with well known semiconductor processing techniques.
  • these batch-fabricated pressure sensors can be used as an integrated array of pressure sensors.
  • the operation of pressure sensor 200 will now be described.
  • membrane 202 is substantially parallel to the X-Y plane, and there is no deflection of membrane 202 along the Z-axis.
  • strain gage resistors 221-224 have equal resistances .
  • a constant external voltage is applied across pads 211a and 213a (or alternatively, across pads 212a and 214a) . Because the strain gage resistors 221-224 all have the same resistance at this time, there is no voltage differential across pads 212a and 214a.
  • Fig. 6A illustrates deformation of membrane 202 in the positive Z direction.
  • Fig. 6B illustrates deformation of membrane 202 in the negative Z direction.
  • strain gage resistors 221 and 222 are symmetrical with respect to the deformation of membrane 202, strain gage resistors 221 and 222 deform (i.e., elongate) by approximately the same amount, the resistances of strain gage resistors 221 and 222 increase by approximately the same amount.
  • a voltage differential is developed across pads 212a and 214a (if a constant input voltage is applied across pads 211a and 213a) .
  • the voltage differential across pads 212a and 214a is proportional to the deflection of membrane 202. Because the deflection of membrane is proportional to the pressure, the voltage differential across pads 212a and 214a is proportional to the pressure.
  • Pressure sensor 200 exhibits the following advantages with respect to conventional piezo-resistive pressure sensors.
  • pressure sensor 200 is extremely sensitive and is capable of measuring pressures much less than 1 psi.
  • pressure sensor 200 has a sensitivity range of 5 inch water column (0.02 psi) full range to 0.005 inch water column full range.
  • pressure sensor 200 has an improved mechanical amplification factor based on the use of a pre-stressed membrane.
  • membrane 202 is pre- stressed, membrane 202 has a tremendous linear range and over-pressure protection. Because membrane 202 has a relatively low mass, the so-called G-force is almost negligible, thereby rendering pressure sensor 200 immune to static errors due to gravity (i.e., sensor position offset) or dynamic errors due to noise and vibration.
  • pressure sensor 200 can be used in the following extremely low pressure range air- flow sensing applications: HVAC damper control, duct air flow and filter pressure drop measurement, chemical flow hoods, hospital room and clean room pressurization, medical instrumentation, industrial control/monitoring and electronics convective cooling integrity detection.
  • Pressure sensor 200 can be operated by itself as previously described, or connected to other structural members which act to limit the range of motion of membrane 202 in the event of exposure to an excessive pressure (i.e., an over-pressure condition) .
  • Fig. 7 is a cross sectional view of a first over-pressure stopper structure 300 and a second over-pressure stopper structure 400 connected to pressure sensor 200.
  • First over-pressure stopper 300 is connected to pressure sensor 200 at the surface which supports membrane 202.
  • First over-pressure stopper 300 includes a substrate 301 having a plurality of support pads 303 formed around the perimeter of the substrate 301.
  • substrate 301 is monocrystalline silicon.
  • An electrically insulating layer 302 is formed over the support pads 303 as illustrated.
  • insulating layer 302 is silicon oxide. Insulating layer 302 prevents the shorting of traces 211- 214 and strain gage resistors 221-224 when the first over-pressure stopper 300 is coupled to pressure sensor 200.
  • the combined height of support pads 303 and insulating layer 302 is selected to correspond with the desired maximum distance of travel of membrane 202 along the positive Z direction. Fig.
  • Second over-pressure stopper 400 is connected to pressure sensor 200 at the surface opposite the surface which supports membrane 202.
  • Second over-pressure stopper 400 includes a substrate 401 having a plurality of holes 402 formed therethrough. In the described example, substrate 401 is monocrystalline silicon.
  • the first over-pressure stopper 300 can include holes (similar to through holes 402) through substrate 301 to vent the upper surface of membrane 202.
  • the second over-pressure stopper 400 can include a channel (similar to channel 304) in substrate
  • first over-pressure stopper 300 can be used without second over-pressure stopper 400.
  • second over-pressure stopper 400 can be used without first over-pressure stopper 300.
  • FIG. 9 is a cross sectional view of a capacitive pressure sensor 500 in accordance with such an alternate embodiment of the present invention.
  • Capacitive pressure sensor 500 includes pressure sensor 200A and first overpressure stopper 300A.
  • Pressure sensor 200A and first over-pressure stopper 300A are similar to previously described pressure sensor 200 and first over-pressure stopper 300.
  • similar elements in Figs. 7 and 9 are labeled with similar reference numbers.
  • pressure sensor 200A includes frame 201, membrane 202 and gold layer 215. Note that gold layer 215 is not patterned, and strain gage layer 216 is not formed in this embodiment.
  • Over-pressure stopper 300A is formed by depositing a conductive layer 305 (e.g., gold) in the channel region 304 of over-pressure stopper 300 (Fig. 8) . Electrical connections are made to conductive layers 215 and 305 and the capacitance between these two layers is measured by a conventional capacitance measuring circuit. As membrane 202 deflects toward over-pressure stopper 300A, the measured capacitance will increase. Conversely, as membrane 202 deflects away from over-pressure stopper 300A, the measured capacitance will decrease. The magnitude of the applied pressure can be derived from the measured capacitance using conventional techniques.
  • Air flow detector Pressure sensor 200 can be used in a variety of applications. As illustrated in Fig. 10A, the pressure sensor 200 is packaged to form a pressure sensor assembly 900. Pressure sensor assembly 900 includes an upper molding 901 and a lower molding 902, each of which can be made of plastic. The upper molding 901 is fixed on the lower molding 902 such that an air-tight seal is formed between these two moldings. Pressure sensor 200 is affixed to the lower molding 902, such that an air-tight seal is formed. Two cavities 903 and 904 extend through the lower molding 902. Pressure sensor 200 is positioned over cavity 904, such that the lower surface of membrane 202 exposed within cavity 904. Cavity 903 extends through lower molding 902 at a location outside of the perimeter of the pressure sensor 200.
  • Air flow tubes 910 and 911 are fitted into cavities 903 and 904 respectively.
  • Air flow tubes 910 and 911 are hollow tubes which are open at their uppermost ends, and closed at their lowermost ends. Openings 930 and 931 are located on the face surfaces of tubes 910 and 911, respectively.
  • Filters 920 and 921 are located over the uppermost ends of air flow tubes 910 and 911, respectively. Filters 920 and 921 prevent particles from entering housing 900 and changing the operating characteristics of membrane 202.
  • the various bond pads 211A-214A of pressure sensor 200 can be connected to connector pins (such as connector pin 905) by bonding wires (such as bonding wire 950) .
  • the resulting structure operates as follows.
  • the pressure sensor assembly 900 is mounted in a location where there is an expected air flow.
  • the pressure sensor assembly 900 is aligned such that opening 930 is facing into the direction of expected air flow, and opening 931 is facing away from the direction of the expected air flow.
  • Fig. 10B is a top view of air flow tubes 910 and 911. Arrows 1010 indicate the direction of expected air flow. When such an air flow exists, a positive pressure PI results through opening 930, and a negative pressure P2 results through opening 931. Opening 931 must be located at least 90 degrees out of phase with the expected direction of the air flow in order for a negative pressure (vacuum) P2 to be developed.
  • air flow tubes 910 and 911 can be replaced with a single air flow tube having two inner channels, with one hole connecting to each of the inner channels.
  • each of air flow tubes 910 and 911 can include two or more holes, with each hole being located at a slightly different angle relative to the air flow, but all joining to the same cavity (e.g., 903 or 904) .
  • two holes are provided with an angle of approximately five degrees between the two holes. Providing two holes enables air flow tubes 910 and 911 to be positioned with a lower degree of accuracy relative to the direction of air flow. However, with each additional hole added per air flow tube, the detected pressure decreases, giving a slight reduction in sensitivity.
  • holes 930 and 931 can be replaced with horizontal slit openings.
  • the pressure sensor assembly 900 can be mounted near a fan in a computer system, or near an electronic component to be protected. Pressure sensor 200 thereby receives the air flow created by the fan. When the air flow is greater than a predetermined threshold, membrane 202 will deform, thereby causing a differential voltage to be developed across pads 212a and 214a. The presence of this differential voltage is then interpreted to indicate the presence of an adequate air flow in the system.
  • the threshold of the pressure sensor 200 can be determined by adjusting the location of pressure sensor 200 both radially or axially with respect to the fan, or by changing the sensitivity of membrane 202. Because pressure sensor 200 immediately detects failure or the sub-optimal operation of the fan, overheating of the electronic components in the system can be prevented at an earlier stage than when using conventional temperature sensing devices.
  • a plurality of pressure sensor assemblies can be located throughout the system to be protected. Such an arrangement can detect localized areas of sub-optimal fan performance.
  • such a device can be used as a feedback sensor to control the rotational speed of a fan such that for a given system or ambient temperature, the fan can be controlled to rotate at whatever speed necessary to achieve the desired air flow.
  • the number of operational fans can be controlled to achieve the desired air flow.
  • Such an adaptive (or 'smart') fan can be used in applications where fan noise is a problem or where system reliability is a major concern.
  • Temperature sensor 200 can be used to form a temperature sensor 1100.
  • Temperature sensor 1100 includes pressure sensor 200, lower housing member 1101, upper housing member 1102 and plug 1103.
  • a cavity 1104 extends through lower housing member 1101.
  • Pressure sensor 200 is affixed to housing member 1101 with an air-tight seal, such that the lower surface (or upper surface) of membrane 202 is exposed by cavity 1104.
  • Upper housing member 1102 is affixed to lower housing member 1101 as illustrated.
  • Upper housing member 1102 includes a filter 1105 which vents the upper surface (or lower surface) of membrane 202. While controlling the ambient temperature, the cavity 1104 is sealed (air tight) with plug 1103.
  • cavity 1104 becomes a closed cavity which contains a fixed amount of air.
  • this air is heated (or cooled) , it expands (or contracts) , thereby causing the conductive membrane to deform.
  • the pressure sensor 200 can be used to detect vacuum (or pressure) in a chamber or air flow by detecting a vacuum in a channel, such as in an air conditioning system, a furnace or in semiconductor processing equipment.
  • Fig. 12 is a schematic diagram of a vacuum pressure sensor 1200 in accordance with another embodiment of the invention.
  • the vacuum pressure sensor 1200 includes pressure sensor 200, which is affixed to a lower housing element 1202.
  • An opening 1203 extends through housing element 1202, thereby exposing the lower surface (or upper surface) of membrane 202.
  • An upper housing element 1204 having a filter 1205 is attached to the lower housing element 1202.
  • the lower housing element 1202 and upper housing 1204 are fitted into a larger housing 1210 which is tapped off of an air flow tube 1211 (e.g., a venturi) .
  • an air flow tube 1211 e.g., a venturi
  • membrane 202 In the absence of air flow through tube 1211, membrane 202 is in a non-deflected state. However, when an air flow F is introduced in tube 1211, membrane 202 is deflected by the negative pressure P induced in the housing 1210.
  • Fig. 13 is a cross sectional diagram of a pitot tube 1300 in accordance with one embodiment of the invention.
  • substrate 201 of pressure sensor 200 is extended, and a trough 1301 is formed in the upper surface of the extended portion of the substrate 201.
  • An upper layer 1311 of structural material, such as monocrystalline silicon, is affixed over the upper surface of substrate 201.
  • An opening 1312 extends through upper layer 1311. The opening 1312 and trough 1301 vent the upper surface of membrane 202 to the outer atmosphere.
  • a lower structural layer 1320 is attached to the lower surface of pressure sensor 200 as illustrated.
  • Lower structural layer 1320 includes support pads 1321, which result in a cavity 1322, a trough 1323 at the lower surface of layer 1320, and an opening 1324 which extends between cavity 1322 and trough 1323.
  • Trough 1323 extends to the outer perimeter of the lower structural layer 1320 at point 1325.
  • a lower cover layer 1330 is affixed to the lower surface of lower structural layer 1320. As a result, the lower surface of membrane 202 is vented to the outer atmosphere through cavity 1321, trough 1323 and opening 1324.
  • the resulting structure can be used to measure air velocity as in a conventional pitot tube. Assuming that the incoming air flow, F, has a velocity V]_ and a pressure P ⁇ _, then at any other point in the flow we have
  • the opening 1312 is pointing a direction perpendicular to the flow, so through the trough 1301, the pressure at the top surface of the membrane 202 is simply Pi, then the differential pressure on membrane 202 is
  • Fig. 14 illustrates a three layer pitot tube structure 1400 which includes three structural members 1401, 1411 and 1421 coupled to pressure sensor 200.
  • Structural member 1401 includes support pads 1402, opening 1403, channel 1404 and opening 1405.
  • the upper surface of structural member 1401 i.e., the surface which includes support pads 1402 is attached to pressure sensor 200 as illustrated.
  • Structural member 1411 is affixed to the lower surface of structural member 1401.
  • Structural member 1421 which is affixed to pressure sensor 200 as illustrated, includes two openings 1422 and 1423. Opening 1422, which has a 90 degree bend, vents the upper surface of membrane 202. Opening 1422, which is a straight opening, is continuous with an opening 1406 formed in pressure sensor 200. Opening 1406 extends between openings 1423 and 1405, thereby venting the lower surface of membrane 202.
  • Pitot tube structure 1400 operates in the same manner previously described for pitot tube structure 1400.
  • Fig. 15 illustrates a two layer pitot tube structure 1500. Similar elements in pitot tube structures 1400 and 1500 are labeled with similar reference numbers.
  • Pitot tube structure 1500 replaces structural members 1401 and 1411 of pitot tube structure 1400 with a single structural member 1501.
  • Structural member 1501 includes support pads 1502, as well as a channel 1503 which vents the underside of membrane 202 to openings 1423 and 1406.
  • Channel 1503 is formed in the same manner previously described for channel 304 (Fig. 8) .
  • Pitot tube structure 1500 operates in the same manner as pitot tube structures 1300 and 1400.
  • a pitot tube structure can be made of another material (such as plastic) and bonded to the switch (which is made from silicon) .
  • Fig. 16 illustrates a pressure sensor which is adapted for use as a gas or chemical detector 1600 (for example, carbon monoxide) .
  • a chemical absorbent material 1601 is deposited over the membrane 202 within opening 203. Material 1601 absorbs chemical present in the ambient atmosphere. Upon absorption, the material 1601 expands, thereby forcing membrane 202 to deform. The resulting voltage differential can be used to identify the presence of an excessive amount of a toxic chemical in the ambient atmosphere .

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Measuring Fluid Pressure (AREA)
  • Pressure Sensors (AREA)

Abstract

L'invention concerne une sonde manométrique comportant une membrane flexible soumise à une force externe, telle qu'une pression issue d'un flux d'air. La membrane flexible recouvre la structure à semi-conducteurs présentant un orifice, de façon qu'une partie de la membrane flexible recouvre la structure à semi-conducteurs et qu'une partie de la membrane flexible recouvre l'orifice. Une contrainte de traction inhérente existe au niveau de la membrane. Une ou plusieurs jauges de contrainte à résistance sont réalisées sur la partie de la membrane recouvrant l'orifice de la structure à semi-conducteurs. La membrane se déforme sous l'action d'une pression s'exerçant extérieurement. Lorsque la membrane se déforme, les jauges de contrainte à résistance s'allongent, ce qui a pour effet d'augmenter la résistivité de ces résistances. Ce changement de puissance mesuré permet de déterminer l'ampleur de la pression externe. Selon un mode de réalisation, un pont de Wheatstone permet de convertir le changement de résistivité des jauges de contrainte à résistance en une différence de potentiel.
EP98910183A 1997-03-24 1998-03-24 Sonde manometrique a semi-conducteur couches minces fabriquee par lots et procede de fabrication correspondant Withdrawn EP0970355A1 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
US08/822,839 US5821596A (en) 1997-03-24 1997-03-24 Batch fabricated semiconductor micro-switch
US822839 1997-03-24
US937859 1997-09-25
US08/937,859 US6700174B1 (en) 1997-09-25 1997-09-25 Batch fabricated semiconductor thin-film pressure sensor and method of making same
PCT/US1998/004331 WO1998043057A1 (fr) 1997-03-24 1998-03-24 Sonde manometrique a semi-conducteur couches minces fabriquee par lots et procede de fabrication correspondant

Publications (1)

Publication Number Publication Date
EP0970355A1 true EP0970355A1 (fr) 2000-01-12

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EP98910183A Withdrawn EP0970355A1 (fr) 1997-03-24 1998-03-24 Sonde manometrique a semi-conducteur couches minces fabriquee par lots et procede de fabrication correspondant

Country Status (5)

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EP (1) EP0970355A1 (fr)
JP (1) JP2001524212A (fr)
CN (1) CN1257578A (fr)
AU (1) AU6448398A (fr)
WO (1) WO1998043057A1 (fr)

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2853057B1 (fr) * 2003-03-26 2005-09-23 Cera Dispositif de detection d'enfoncement a amplificateur de detection
JP5092167B2 (ja) * 2009-03-24 2012-12-05 三菱電機株式会社 半導体圧力センサおよびその製造方法
US9968254B2 (en) * 2010-01-05 2018-05-15 Sensimed Sa Intraocular pressure monitoring device
US8461655B2 (en) * 2011-03-31 2013-06-11 Infineon Technologies Ag Micromechanical sound transducer having a membrane support with tapered surface
CN102692294B (zh) * 2012-05-29 2014-04-16 上海丽恒光微电子科技有限公司 复合式压力传感器及其形成方法
MY184622A (en) * 2013-11-26 2021-04-09 Mimos Berhad A pressure sensor with magnetic nanoparticles
CN107430039A (zh) * 2015-03-17 2017-12-01 安普泰科电子韩国有限公司 压力传感器
CN107068959A (zh) * 2017-02-17 2017-08-18 厦门金龙旅行车有限公司 一种用于动力客车动力电池的热失控早期探测系统及其控制方法
US11137308B2 (en) * 2019-01-02 2021-10-05 Baker Hughes, A Ge Company, Llc High sensitivity pressure sensor package
CN112484631B (zh) * 2020-12-09 2022-01-11 湖南启泰传感科技有限公司 一种薄膜压力传感器及其布局方法

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4462018A (en) * 1982-11-05 1984-07-24 Gulton Industries, Inc. Semiconductor strain gauge with integral compensation resistors
JPS63165725A (ja) * 1986-12-26 1988-07-09 Aisin Seiki Co Ltd 圧力センサ−用歪ゲ−ジ
JPH02177567A (ja) * 1988-12-28 1990-07-10 Toyota Central Res & Dev Lab Inc 半導体容量型圧力センサ
US5295395A (en) * 1991-02-07 1994-03-22 Hocker G Benjamin Diaphragm-based-sensors
JPH05296864A (ja) * 1992-04-16 1993-11-12 Nec Corp 圧力センサおよびその製造方法

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9843057A1 *

Also Published As

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CN1257578A (zh) 2000-06-21
WO1998043057A1 (fr) 1998-10-01
JP2001524212A (ja) 2001-11-27
AU6448398A (en) 1998-10-20

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