WO2009045090A2 - Integrated thermally compensated ph egfet-flow rate sensor - Google Patents

Integrated thermally compensated ph egfet-flow rate sensor Download PDF

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Publication number
WO2009045090A2
WO2009045090A2 PCT/MY2008/000109 MY2008000109W WO2009045090A2 WO 2009045090 A2 WO2009045090 A2 WO 2009045090A2 MY 2008000109 W MY2008000109 W MY 2008000109W WO 2009045090 A2 WO2009045090 A2 WO 2009045090A2
Authority
WO
WIPO (PCT)
Prior art keywords
egfet
flow rate
thermally compensated
sensor
rate sensor
Prior art date
Application number
PCT/MY2008/000109
Other languages
French (fr)
Other versions
WO2009045090A3 (en
Inventor
Ismahadi Bin Syono Mohd
Binti Abdul Rani Rozina
Rofei Mat Hussin Mohd
Original Assignee
Mimos Berhad
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 Mimos Berhad filed Critical Mimos Berhad
Publication of WO2009045090A2 publication Critical patent/WO2009045090A2/en
Publication of WO2009045090A3 publication Critical patent/WO2009045090A3/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/05—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects
    • G01F1/20—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by detection of dynamic effects of the flow

Definitions

  • the present invention relates to an integrated thermally compensated pH EGFET -flow rate sensor.
  • a glass electrode has typically been used as an ion sensing electrode.
  • a glass electrode has the disadvantages of difficulty in measuring miniaturized structures, susceptibility to damage, and low portability.
  • ISFET has the advantages of compatibility with standard CMOS process, high input impedance, and low output impedance, miniaturization capability minute solution measurement, rapid response, and pH measurement capability. Therefore, ISFET has been developed and applied in a variety of fields relating to miniaturized pH sensors and biotechnical sensing devices.
  • EGFET which is an extended ISFET can be combined with a flow rate sensor for integrated measurement of for example water contamination and its flow rate useful for on-line household monitoring (consumption and quality).
  • the temperature fluctuation which causes drift can be compensated without using temperature sensor.
  • the objective of the present invention is to provide a method of designing and fabrication an integrated thermally compensated pH Extended Gate Field Effect Transistor (EGFET) and a flow rate sensor using standard CMOS flow.
  • EGF Extended Gate Field Effect Transistor
  • Another objective of the present invention is to provide an EGFET which is integrated with an actual MEMS device.
  • the present invention relates to an integrated thermally compensated pH EGFET used as a flow rate sensor characterized in that wherein the integrated thermally compensated pH EGFET comprises of at least three EGFETs are combined to create at least two sensors that can detect thermally compensated pH of a solution and its flow rate simultaneously and wherein said sensors are used to form thermally compensated pH sensor by creating a sensing electrode sensitive to H + ions such as nitride and an insensitive one such as oxide and wherein both are exposed to the same solution thereby experiencing the same temperature and pH change.
  • the signal from nitride based electrode therefore contains pH and temperature (Vp+V t ) while the oxide based contains only temperature effect (Vt). Said signals are thereafter fed into a differential amplifier/comparator giving the signal voltage (V p ) at the output due to pH alone The signal V p +V t is also fed into another differential amplifier and wherein the other input of this amplifier comes from an EGFET whose gate is made of similar material as the pH sensor.
  • the sensor functions as a MEMS cantilever wherein the silicon substrate is etched thru for solution to pass thru and wherein when the solution flows the cantilever would bend according to volume flow rate,
  • Figure 1 shows a model of said present invention.
  • Figure 2 shows abasic schematic of sensing circuit of the present invention
  • Figure 3 shows a cross section of EGFETs with and without a cantilever.
  • Figure 4 shows a top view of nitride and oxide coated ISFET with flow rate sensor in the middle and ref electrode on extreme left connected to the sensing circuit DETAILED DESCRIPTION OF THE INVENTION
  • EGFETs are combined to create two sensors that can detect thermally compensated pH of a solution and its flow rate simultaneously.
  • An, EGFET is an advantageous alternative to ISFET as it allows the sensing part to be located away from the transistor area.
  • Two of the EGFETS are used to form thermally compensated pH sensor by creating a sensing electrode sensitive to H + ions such as nitride and an insensitive one such as oxide. Both are exposed to the same solution thereby experiencing the same temperature and pH change.
  • the signal from nitride based electrode therefore contains pH and temperature (V p +V t ) while the oxide based contains only temperature effect (V t ).

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  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Volume Flow (AREA)

Abstract

The present invention relates to an integrated thermally compensated pH EGFET used as a flow rate sensor characterized in that wherein the integrated thermally compensated pH EGFET comprises of at least three EGFETs are combined to create at least two sensors that can detect thermally compensated pH of a solution and its flow rate simultaneously and wherein said sensors are used to form thermally compensated pH sensor by creating a sensing electrode sensitive to H+ ions such as nitride and an insensitive one such as oxide and wherein both are exposed to the same solution thereby experiencing the same temperature and pH change.

Description

INTEGRATED THERMALLY COMPENSATED pH EGFET-FLOW RATE
SENSOR
FIELD OF THE INVENTION
The present invention relates to an integrated thermally compensated pH EGFET -flow rate sensor.
BACKGROUND OF THE INVENTION
A glass electrode has typically been used as an ion sensing electrode. A glass electrode has the disadvantages of difficulty in measuring miniaturized structures, susceptibility to damage, and low portability. ISFET has the advantages of compatibility with standard CMOS process, high input impedance, and low output impedance, miniaturization capability minute solution measurement, rapid response, and pH measurement capability. Therefore, ISFET has been developed and applied in a variety of fields relating to miniaturized pH sensors and biotechnical sensing devices.
EGFET which is an extended ISFET can be combined with a flow rate sensor for integrated measurement of for example water contamination and its flow rate useful for on-line household monitoring (consumption and quality). The temperature fluctuation which causes drift can be compensated without using temperature sensor.
The objective of the present invention is to provide a method of designing and fabrication an integrated thermally compensated pH Extended Gate Field Effect Transistor (EGFET) and a flow rate sensor using standard CMOS flow.
Another objective of the present invention is to provide an EGFET which is integrated with an actual MEMS device. SUMMARY OF THE INVENTION
The present invention relates to an integrated thermally compensated pH EGFET used as a flow rate sensor characterized in that wherein the integrated thermally compensated pH EGFET comprises of at least three EGFETs are combined to create at least two sensors that can detect thermally compensated pH of a solution and its flow rate simultaneously and wherein said sensors are used to form thermally compensated pH sensor by creating a sensing electrode sensitive to H+ ions such as nitride and an insensitive one such as oxide and wherein both are exposed to the same solution thereby experiencing the same temperature and pH change.
The signal from nitride based electrode therefore contains pH and temperature (Vp+Vt) while the oxide based contains only temperature effect (Vt). Said signals are thereafter fed into a differential amplifier/comparator giving the signal voltage (Vp) at the output due to pH alone The signal Vp+Vt is also fed into another differential amplifier and wherein the other input of this amplifier comes from an EGFET whose gate is made of similar material as the pH sensor.
The sensor functions as a MEMS cantilever wherein the silicon substrate is etched thru for solution to pass thru and wherein when the solution flows the cantilever would bend according to volume flow rate,
BRIEF DESCRIPTION OF THE FIGURES
Figure 1 shows a model of said present invention.
Figure 2 shows abasic schematic of sensing circuit of the present invention
Figure 3 shows a cross section of EGFETs with and without a cantilever.
Figure 4 shows a top view of nitride and oxide coated ISFET with flow rate sensor in the middle and ref electrode on extreme left connected to the sensing circuit DETAILED DESCRIPTION OF THE INVENTION
The present invention will now be described in detailed with reference made to the accompanied drawings but not limited thereto,
According to the present invention, three EGFETs are combined to create two sensors that can detect thermally compensated pH of a solution and its flow rate simultaneously. An, EGFET is an advantageous alternative to ISFET as it allows the sensing part to be located away from the transistor area.
Two of the EGFETS are used to form thermally compensated pH sensor by creating a sensing electrode sensitive to H+ ions such as nitride and an insensitive one such as oxide. Both are exposed to the same solution thereby experiencing the same temperature and pH change. The signal from nitride based electrode therefore contains pH and temperature (Vp+Vt) while the oxide based contains only temperature effect (Vt).
These signals are thereafter fed into a differential amplifier/comparator giving the signal voltage (Vp) at the output due to pH alone. The signal Vp+Vt is also fed into another differential amplifier. The other input of this amplifier comes from an EGFET whose gate is made of similar material as the pH sensor (nitride).
While this gate looks similar to the other gates of the previous EGFETs, it functions as a MEMS cantilever. Its silicon substrate is etched thru for solution to pass thru, Whenever the solution flows the cantilever would bend according to volume flow rate (g.cm/sec). The more it bends the more resistance will be introduced. This can be modeled as the following with variable membrane and line resistances, Figure 1.
This signal Vp+Vt+Vr. where Vr is contribution from resistance change and the signal Vp+Vt are fed into the second differential amplifier giving output due to flow rate alone, Figure 2.

Claims

1. An integrated thermally compensated pH EGFET used as a flow rate sensor characterized in that wherein the integrated thermally compensated pH EGFET comprises of at least three EGFETs are combined to create at least two sensors that can detect thermally compensated pH of a solution and its flow rate simultaneously and wherein said sensors are used to form thermally compensated pH sensor by creating a sensing electrode sensitive to H+ ions such as nitride and an insensitive one such as oxide and wherein both are exposed to the same solution thereby experiencing the same temperature and pH change.
2. An integrated thermally compensated pH EGFET used as a flow rate sensor as claimed in Claim 1 wherein the signal from nitride based electrode therefore contains pH and temperature (Vp+Vt) while the oxide based contains only temperature effect (Vt).
3. An integrated thermally compensated pH EGFET used as a flow rate sensor as claimed in Claim 1 wherein said signals are thereafter fed into a differential amplifier/comparator giving the signal voltage (Vp) at the output due to pH alone
4. An integrated thermally compensated pH EGFET used as a flow rate sensor as claimed in Claim 1 wherein the signal Vp+Vt is also fed into another differential amplifier and wherein the other input of this amplifier comes from an EGFET whose gate is made of similar material as the pH sensor.
5. An integrated thermally compensated pH EGFET used as a flow rate sensor as claimed in Claim 1 wherein the sensor functions as a MEMS cantilever wherein the silicon substrate is etched thru for solution to pass thru and wherein when the solution flows the cantilever would bend according to volume flow rate.
PCT/MY2008/000109 2007-10-05 2008-09-29 Integrated thermally compensated ph egfet-flow rate sensor WO2009045090A2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
MYPI20071720 2007-10-05
MYPI20071720 2007-10-05

Publications (2)

Publication Number Publication Date
WO2009045090A2 true WO2009045090A2 (en) 2009-04-09
WO2009045090A3 WO2009045090A3 (en) 2009-06-04

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Application Number Title Priority Date Filing Date
PCT/MY2008/000109 WO2009045090A2 (en) 2007-10-05 2008-09-29 Integrated thermally compensated ph egfet-flow rate sensor

Country Status (1)

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WO (1) WO2009045090A2 (en)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6294133B1 (en) * 1998-01-14 2001-09-25 Horiba, Ltd. Multiple detecting apparatus for physical phenomenon and/or chemical phenomenon
US6653842B2 (en) * 2001-07-10 2003-11-25 Digital Concepts Of Missouri Galvanic probes as pH and oxidation reduction potential sensors, control devices employing such probes, and related methods
US6974716B2 (en) * 2003-03-19 2005-12-13 Chung Yuan Christian University Method for fabricating a titanium nitride sensing membrane on an EGFET

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5614148A (en) * 1979-07-16 1981-02-10 Shimadzu Corp Semiconductor ion selective electrode

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6294133B1 (en) * 1998-01-14 2001-09-25 Horiba, Ltd. Multiple detecting apparatus for physical phenomenon and/or chemical phenomenon
US6653842B2 (en) * 2001-07-10 2003-11-25 Digital Concepts Of Missouri Galvanic probes as pH and oxidation reduction potential sensors, control devices employing such probes, and related methods
US6974716B2 (en) * 2003-03-19 2005-12-13 Chung Yuan Christian University Method for fabricating a titanium nitride sensing membrane on an EGFET

Also Published As

Publication number Publication date
WO2009045090A3 (en) 2009-06-04

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