WO1986003583A1 - Temperature sensor - Google Patents

Temperature sensor Download PDF

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Publication number
WO1986003583A1
WO1986003583A1 PCT/SE1985/000508 SE8500508W WO8603583A1 WO 1986003583 A1 WO1986003583 A1 WO 1986003583A1 SE 8500508 W SE8500508 W SE 8500508W WO 8603583 A1 WO8603583 A1 WO 8603583A1
Authority
WO
WIPO (PCT)
Prior art keywords
temperature
temperature sensor
traps
charge
diode
Prior art date
Application number
PCT/SE1985/000508
Other languages
French (fr)
Inventor
Mats Kleverman
Original Assignee
Deltasense Instruments (Pte) 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 Deltasense Instruments (Pte) Ltd. filed Critical Deltasense Instruments (Pte) Ltd.
Publication of WO1986003583A1 publication Critical patent/WO1986003583A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
    • G01K7/01—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using semiconducting elements having PN junctions
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
    • G01K7/16—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements
    • G01K7/22—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a non-linear resistance, e.g. thermistor
    • G01K7/24—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a non-linear resistance, e.g. thermistor in a specially-adapted circuit, e.g. bridge circuit
    • G01K7/245—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a non-linear resistance, e.g. thermistor in a specially-adapted circuit, e.g. bridge circuit in an oscillator circuit

Definitions

  • This invention relates to a temperature sensor based on temperature dependence of electric charge emission from charge carrier traps in the energy bandgap of a solid material, which is subjected to the temperature to be measured.
  • thermocouples which use electrical methods, e.g. thermocouples, thermistors, and pn-diodes give signals magnitude of whichis a function of the temperature. Changes in the contact resistance and/or aging phenomena alter the signal level and severe errors may be introduced in the temperature measured.
  • a semiconductor or insulator which has an energy bandgap is preferably used as a sensor element.
  • the sensor elements are made in such a way that impurity centers, acting as charge carrier traps, and at leastd one space charge region are incorporated in the material.
  • the traps are fileld with electrical charges, electrons or holes, by "pumping" the sensor element by applying an electrical pulse e.g. by short circuiting a reversed biased pn-diode before initiating a temperature measurement.
  • the charge emission from the traps is measured after the filling pulse. This can be done in several different ways, depending on the implementation of the sensor element.
  • the charge emission can be measured as a change in the .apitance of the diode.
  • MIS Metal Isolator Semiconductor
  • the time constant of the capacitance change of the diode is a measure of the temperature.
  • Fig. 1 shows an embodiment of the sensor when the change of the capacitance of a pn-diode is detected and the temperature of the surroundings is calculated and displayed.
  • Fig. 2a shows the pumping signal applied to the embodiment of the present invention.
  • the detected capacitance of embodiment of the invention is presented in Fig. 2b.
  • Fig. 2c shows the relation between the time constant of the changes in the signals shown in Fig. 2b and the temperature.
  • a diode is connected in parallel with a pulse generator 2 in series with a controllable current switch S2.
  • a MIS-capacitor, a Schottky diode or any other element with a space charge region e.g. a transistor, can be used instead of the shown pn-diode.
  • a control logic unit 4 is connected to an output of the capacitance meter 3, to an activation input of the capacitance meter 3, to an activation input of the pulse generator 2 and to the activation inputs of the current switches S 1 and S 2 .
  • a measurement is initiated by closing the current switch S 1 by a signal from the control logic unit 4.
  • the pulse generator 2 is activated to give an output signal (shown in Fig. 2a) by an activation signal from the control logic unit 4.
  • This output signal is a pulse sequence consisting of long measurement pulses with short pulses in between (filling pulses). The "pumping" of the diode takes place during the filling pulses.
  • control logic unit 4 It is possible to control one or more of the parameters such as the pulse frequency, the length of the measurement pulse, and the pulse pause from the control logic unit 4.
  • the control logic unit 4 keeps the current switch S 2 opened in order to prevent damage to the capacitance meter 3 during the pumping procedure in the pulse pause when the diode is short circuited. During the measurement pulses the control logic unit keeps the current switch S 2 closed.
  • the control logic unit 4 is implemented preferably by a micro-computer and the output signal from the capacitance meter 3 is sampled with a certain frequency.
  • Fig. 2b shows the capacitance of the diode during several measurement periods.
  • the control logic unit 4 samples the output signal of the capacitance meter 3 at time t 1 , t 2 , t 3 , and t 4 and thus the corresponding capacitance values C 1 , C 2 , C 3 , and C 4 are obtained.
  • the course of events during a measurement is as follows:
  • the impurity centers in the space charge region of the diode are fileld during the pulse pause 2 of the pulse generator 2.
  • the filled impurity traps emit the electrons or holes and the capacitance of the diode changes correspondingly.
  • an output signal is a function of the temperature, as shown in Fig. 2b.
  • the signal is sampled at least twice inside every time window t 2 - t 3 .
  • the time constant is converted into temperature by the control logic unit 4 giving an output signal to a digital or analog display.
  • the control logic unit can automatically control the pulse generator 2 in such a way that the time window, giving the best resolution in the temperature, may be used fo adapt to the temperature range of interest.
  • the innovation is thus based on the principle that after a filling pulse, resulting in a certain occupation of majority or minority traps, a capacitance transient is detected.
  • the decay rate of the transient is directly related to the temperature of the atmosphere. Since several minority and majority traps can exist in the same semiconductor material the same sensor element can be used for temperature measurements in several temperature ranges.
  • semiconductor materials could be: A1P, GaP, GaAs, InP,
  • These materials are doped with impurities or treated in a proper way to produce charge carrier traps. If Si is used it can be doped with S, Se or Te and if GaAs is used it can be doped with Fe.
  • the emission rates of electric charges from the charge carrier traps, after the pumping (filling pulse), are related to the energy difference between the energy position of the trap and the valence band (hole-emission) or the conduction band (electron emission) by an exponential relation.
  • a majority carrier pulse which decreases momentarily the reverse voltage bias of the diode and the traps become occupied by majority carriers which pulse is of the type shown in Fig. 1 and Fig. 2a-2c.
  • the other type of occupational pulse is a minority carrier pulse which momentarily forward bias the diode, and the traps become occupied by minority carriers.
  • the last alternative is not presented in any figure but is, nevertheless, a possibility within this innovation.
  • the circuit in Fig. 1 is interchangable in such a way to provide the possibility, that a pulse from the pulse generator 2 may inject minority charge carriers.
  • This pulse is more or less of the same form as the pulse shown in Fig. 2a but with the difference that the injection pulse is above the abscissa.
  • the capacitance transient in this case is upside down, compared to the one shown in Fig. 2b, in such a way that the peak is located at a high capacitance value and the capacitance signal decreases with the time.
  • t is the time constant of the transient, i.e. the inverted value of the emission rate, and has a well defined relation to the temperature. This is shown in Fig. 2c, where log(1/r) versus 1/T is plotted. T is the temperature in K (Kelvin). Log(1/r) is more or less a linear function of 1/T.
  • the control logic unit 4 in Fig. 1 computes the value of log(1/r) from the sampled values from the capacitance meter 3, and T is then computed from the graph in Fig. 2c.
  • the signal to the indication unit 5 is suitabley computed from the mean value of T obtained from two or more measurements.
  • the length of the filling pulse can be 100ns - 1ms e.g. 5us and the spacing between the pulses may be 5 us - 1s.
  • the circuit shown in Fig. 1 can be made with contemporary techniques as an integrated circuit.
  • the elements 1, 1', 2, 3, S 1 , S 2 can be made as one unit, fabricated as an IC, with a control logic unit being a one-chips microprocessor.
  • the semiconductor component in the example above, is a pn-diode, a MIS capacitor, or a Schottky diode and has been pumped by an electrical pulse.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • Testing Of Individual Semiconductor Devices (AREA)
  • Thermistors And Varistors (AREA)
  • Testing Or Measuring Of Semiconductors Or The Like (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)

Abstract

Temperature sensor based on temperature dependence of electric charge carrier traps in the energy band of a solid material, which is subjected to the temperature to be measured. The charge carrier traps are first filled with electrical charges. Thereafter a quantity having a predetermined relation to the emitted charge or to the rest of the charge is measured. The change in the measured quantity has a time constant corresponding to a given temperature. The time constant is indicated and the temperature is calculated.

Description

TEMPERATURE SENSOR
Background of the invention
This invention relates to a temperature sensor based on temperature dependence of electric charge emission from charge carrier traps in the energy bandgap of a solid material, which is subjected to the temperature to be measured.
For many applications of temperature measurements, it is of great interest to be able to use a method which does not rely on a calibration procedure and combines good reproducibility with long term stability.
Contemporary temperature sensors, which use electrical methods, e.g. thermocouples, thermistors, and pn-diodes give signals magnitude of whichis a function of the temperature. Changes in the contact resistance and/or aging phenomena alter the signal level and severe errors may be introduced in the temperature measured.
The present invention, given by the characteristics stated in patent claim No 1 , is an improvement compared with the sensors dicsussed above. Further improvements are given by the additional patent claims.
Summary of the invention
A semiconductor or insulator which has an energy bandgap is preferably used as a sensor element. The sensor elements are made in such a way that impurity centers, acting as charge carrier traps, and at leastd one space charge region are incorporated in the material. The traps are fileld with electrical charges, electrons or holes, by "pumping" the sensor element by applying an electrical pulse e.g. by short circuiting a reversed biased pn-diode before initiating a temperature measurement.
The charge emission from the traps is measured after the filling pulse. This can be done in several different ways, depending on the implementation of the sensor element.
If the sensor is manufactured as a diode for electrical measurements, the charge emission can be measured as a change in the .apitance of the diode. The diode can be a pn-diode, a MIS-capacitor (MIS = Metal Isolator Semiconductor), or a Schottky diode. The time constant of the capacitance change of the diode is a measure of the temperature.
Brief description of drawings
The innovation is described in more detail below and referring to the enclosed drawings.
Fig. 1, shows an embodiment of the sensor when the change of the capacitance of a pn-diode is detected and the temperature of the surroundings is calculated and displayed.
Fig. 2a shows the pumping signal applied to the embodiment of the present invention. The detected capacitance of embodiment of the invention is presented in Fig. 2b. Fig. 2c shows the relation between the time constant of the changes in the signals shown in Fig. 2b and the temperature.
Description of preferred embodiment In the embodiment, shown in Fig.1, a diode is connected in parallel with a pulse generator 2 in series with a controllable current switch S2. A MIS-capacitor, a Schottky diode or any other element with a space charge region e.g. a transistor, can be used instead of the shown pn-diode. A control logic unit 4 is connected to an output of the capacitance meter 3, to an activation input of the capacitance meter 3, to an activation input of the pulse generator 2 and to the activation inputs of the current switches S1 and S2.
A measurement is initiated by closing the current switch S1 by a signal from the control logic unit 4. The pulse generator 2 is activated to give an output signal (shown in Fig. 2a) by an activation signal from the control logic unit 4. This output signal is a pulse sequence consisting of long measurement pulses with short pulses in between (filling pulses). The "pumping" of the diode takes place during the filling pulses.
It is possible to control one or more of the parameters such as the pulse frequency, the length of the measurement pulse, and the pulse pause from the control logic unit 4.
The control logic unit 4 keeps the current switch S2 opened in order to prevent damage to the capacitance meter 3 during the pumping procedure in the pulse pause when the diode is short circuited. During the measurement pulses the control logic unit keeps the current switch S2 closed. The control logic unit 4 is implemented preferably by a micro-computer and the output signal from the capacitance meter 3 is sampled with a certain frequency.
Fig. 2b shows the capacitance of the diode during several measurement periods. The control logic unit 4 samples the output signal of the capacitance meter 3 at time t1, t2, t3, and t4 and thus the corresponding capacitance values C 1 , C2, C3, and C4 are obtained.
The course of events during a measurement is as follows: The impurity centers in the space charge region of the diode are fileld during the pulse pause 2 of the pulse generator 2. During the measurement pulse the filled impurity traps emit the electrons or holes and the capacitance of the diode changes correspondingly. By measuring the capacitance of the diode, an output signal is a function of the temperature, as shown in Fig. 2b. Alternatively, it is possible to measure the capacitance in the time period between t2 and t3, which must be separated from t1 and t4 defining the pumping pulse. In the last alternative the signal is sampled at least twice inside every time window t2 - t3. The time constant is converted into temperature by the control logic unit 4 giving an output signal to a digital or analog display.
Different materials may be chosen for the diode to obtain different effective temperature ranges, since every material has a specific relation between the time constant of the capacitance transient and the temperature. Several diodes 1, 1' of different types can alternatively be connected in the circuit by the switch S3, as shown in Fig. 1. In order to fully make use of this possibility, the control logic unit can automatically control the pulse generator 2 in such a way that the time window, giving the best resolution in the temperature, may be used fo adapt to the temperature range of interest.
The innovation is thus based on the principle that after a filling pulse, resulting in a certain occupation of majority or minority traps, a capacitance transient is detected. The decay rate of the transient is directly related to the temperature of the atmosphere. Since several minority and majority traps can exist in the same semiconductor material the same sensor element can be used for temperature measurements in several temperature ranges. Such semiconductor materials could be: A1P, GaP, GaAs, InP,
InAs, In1-xA1xP. In1-xGaxP, Ga1-xA1xAs, In1-xGaxAS, Ga1-xA1xAs InAs1-yPy, GaAs1-yPy, where 0≤ x≤1 and 0≤ y ≤1, or Ge, Si, C or ZnTe, ZnSe, CdTe, CdSe or CdS, SiC, GaN. These materials are doped with impurities or treated in a proper way to produce charge carrier traps. If Si is used it can be doped with S, Se or Te and if GaAs is used it can be doped with Fe. The emission rates of electric charges from the charge carrier traps, after the pumping (filling pulse), are related to the energy difference between the energy position of the trap and the valence band (hole-emission) or the conduction band (electron emission) by an exponential relation.
Two major types of filling pulses exist, namely: a majority carrier pulse, which decreases momentarily the reverse voltage bias of the diode and the traps become occupied by majority carriers which pulse is of the type shown in Fig. 1 and Fig. 2a-2c. The other type of occupational pulse is a minority carrier pulse which momentarily forward bias the diode, and the traps become occupied by minority carriers. The last alternative is not presented in any figure but is, nevertheless, a possibility within this innovation.
The circuit in Fig. 1 is interchangable in such a way to provide the possibility, that a pulse from the pulse generator 2 may inject minority charge carriers. This pulse is more or less of the same form as the pulse shown in Fig. 2a but with the difference that the injection pulse is above the abscissa. The capacitance transient in this case is upside down, compared to the one shown in Fig. 2b, in such a way that the peak is located at a high capacitance value and the capacitance signal decreases with the time.
t is the time constant of the transient, i.e. the inverted value of the emission rate, and has a well defined relation to the temperature. This is shown in Fig. 2c, where log(1/r) versus 1/T is plotted. T is the temperature in K (Kelvin). Log(1/r) is more or less a linear function of 1/T.
The control logic unit 4 in Fig. 1 computes the value of log(1/r) from the sampled values from the capacitance meter 3, and T is then computed from the graph in Fig. 2c. The signal to the indication unit 5 is suitabley computed from the mean value of T obtained from two or more measurements. However, it is also possible to have a running indication of the temperature, especially when the indication unit 5 is an anlog display instrument. The length of the filling pulse can be 100ns - 1ms e.g. 5us and the spacing between the pulses may be 5 us - 1s. Thus, it is possiboe to follow a rather fast change in the temperature with the sensor in accordance with the present innovation even if the control logic unit computes a mean value of several measurements of the temperature.
The circuit shown in Fig. 1 can be made with contemporary techniques as an integrated circuit. Alternatively, the elements 1, 1', 2, 3, S1, S2 can be made as one unit, fabricated as an IC, with a control logic unit being a one-chips microprocessor.
The semiconductor component, in the example above, is a pn-diode, a MIS capacitor, or a Schottky diode and has been pumped by an electrical pulse.
The systems described above, with reference to the drawings, may be varied in many ways within the scope of the invention.

Claims

CLAI MS
1. A temperature sensor comprising:
- a body (1) of a solid material with an energy bandgap with electric charge carrier traps and incorporating at least one space charge region as a detection element, - an activation apparatus (2) connected to said body, which apparatus during the first time period supplies electric charges to charge carrier traps in said body so as to completely or almost completely fill traps in said space region with charges, - a detection apparatus (3) which during the second time period after said first time period detects a quantity which is unambiguously related to the magnitude of the thermally emitted charge from traps or to remaining charge in traps, said quantity having a time constant dependent on temperature during the period said activation is not active,
- an apparatus (4) which converts said detected quantity into a signal giving information about the temperature.
2. Temperature sensor as claimed in claim 1, in which the said body (1) of solid material is a pn-diode.
3. Temperature sensor as claimed in claim 1, in which the said body (1) of solid material is a MIS-capacitor.
4. Temperature sensor as claimed in claim 1, in which the said body (1) of solid material is a Schottky diode.
5. Temperature sensor according to any of the previous claims, in which said activation apparatus (2) is a pulse generator and the detector apparatus (3) is a capacitance meter.
6. Temperature sensor according to any of the previous claims, in which said sensor is a part of an integrated circuit.
PCT/SE1985/000508 1984-12-06 1985-12-06 Temperature sensor WO1986003583A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE8406199A SE445781B (en) 1984-12-06 1984-12-06 TEMPERATURE SENSOR
SE8406199-3 1984-12-06

Publications (1)

Publication Number Publication Date
WO1986003583A1 true WO1986003583A1 (en) 1986-06-19

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ID=20358068

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1985/000508 WO1986003583A1 (en) 1984-12-06 1985-12-06 Temperature sensor

Country Status (3)

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EP (1) EP0204808A1 (en)
SE (1) SE445781B (en)
WO (1) WO1986003583A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003016846A1 (en) * 2001-08-14 2003-02-27 Schneider Automation Inc. Solid state temperature measuring device and method

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3344671A (en) * 1964-12-03 1967-10-03 Gordy Irving Time measurement as indication of temperature
EP0029653A1 (en) * 1979-11-21 1981-06-03 THE GENERAL ELECTRIC COMPANY, p.l.c. Optical systems for sensing and measuring physical quantities
SE426262B (en) * 1981-05-08 1982-12-20 Asea Ab FIBEROPTICAL METDON
GB2109938A (en) * 1981-11-24 1983-06-08 Ferranti Ltd Temperature measuring circuit using semi-conductor diode
EP0095673A1 (en) * 1982-05-27 1983-12-07 Asea Ab Optical-fibre sensor for measuring physical quantities

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3344671A (en) * 1964-12-03 1967-10-03 Gordy Irving Time measurement as indication of temperature
EP0029653A1 (en) * 1979-11-21 1981-06-03 THE GENERAL ELECTRIC COMPANY, p.l.c. Optical systems for sensing and measuring physical quantities
SE426262B (en) * 1981-05-08 1982-12-20 Asea Ab FIBEROPTICAL METDON
GB2109938A (en) * 1981-11-24 1983-06-08 Ferranti Ltd Temperature measuring circuit using semi-conductor diode
EP0095673A1 (en) * 1982-05-27 1983-12-07 Asea Ab Optical-fibre sensor for measuring physical quantities

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003016846A1 (en) * 2001-08-14 2003-02-27 Schneider Automation Inc. Solid state temperature measuring device and method

Also Published As

Publication number Publication date
SE445781B (en) 1986-07-14
SE8406199D0 (en) 1984-12-06
EP0204808A1 (en) 1986-12-17

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