JP5777148B2 - Temperature measurement method - Google Patents

Description

  The present invention relates to a temperature measurement method for measuring the temperature of an object surface.

As a conventional temperature measuring method, for example, a planar temperature sensor as described in Patent Document 1 is used. In the surface temperature sensor, measurement cells are arranged in a matrix, and a thin film transistor and a resistor are connected in series in each measurement cell. Since the electrical resistance of the resistor has temperature dependence, the temperature was measured using this. Specifically, at the time of measurement, the thin film transistor is turned on, a current is passed through the resistor, a change in the current value (electric resistance of the resistor) is measured, and the temperature of each measurement cell is determined. I was measuring.

JP 2006-170642 A

However, the conventional temperature measurement method using the planar temperature sensor has a problem that the measurement itself causes a temperature fluctuation and the measurement result cannot be trusted. That is, the resistor for measuring the electrical resistance is directly connected to the thin film transistor, and the thin film transistor self-heating raises the temperature of the resistor so that the thin film transistor is turned on. It was a hindrance. In addition, since the temperature dependence of the electrical resistance is weak, the conventional temperature measurement method using the planar temperature sensor has a problem that it is difficult to measure a slight temperature change. As described above, the conventional temperature measurement method using the planar temperature sensor has a problem that the measurement result cannot be relied upon and the measurement resolution is low. In other words, there is a problem that there is no high-performance and practical temperature measurement method.

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

Application Example 1 A temperature measurement method according to this application example includes a first step in which a thin film transistor is turned on and one end of a capacitor connected to the thin film transistor is charged to an initial potential. A second step of supplying a single potential to turn the thin film transistor into a first off state, and maintaining the first off state; and a third step of detecting a potential at one end,
As a result of executing the first step, the second step, and the third step, when the potential at one end is in the range of 95% to 100% of the initial potential, the second potential is further applied to the first step and the gate electrode. To turn the thin film transistor into a second off state, and perform a fourth step and a third step for maintaining the second off state.
Since the thin film transistor can be formed in units of micrometers, according to this configuration, a temperature sensor having a very high spatial resolution of several micrometers can be realized. Further, according to this configuration, the temperature measurement period and the measurement result output period can be separated, so that accurate temperature measurement is realized without self-heating of the thin film transistor during measurement. In addition, when the measured temperature is outside the measurement range of the first temperature measurement, the next temperature measurement is performed in a different measurement range, and the temperature measurement is made precisely in each measurement range, so a wide temperature range Precise temperature measurement can be performed over a range. In other words, a high-performance and practical temperature measurement method can be provided.

Application Example 2 In the temperature measurement method according to the application example, it is preferable that the second potential is lower than the first potential.
Although it takes time to measure low temperatures, according to this configuration, the second temperature measurement is intended for low temperature measurements, so on average, accurate temperature measurement can be performed over a wide range in a relatively short time. .

Application Example 3 In the temperature measurement method according to the application example, it is preferable that the period of the fourth process is longer than the period of the second process.
According to this configuration, since the first temperature measurement is performed in a short time, on average, accurate temperature measurement can be performed in a relatively short time.

(Application Example 4) In the temperature measurement method according to the application example described above, when the first step, the fourth step, and the third step are executed, the potential at one end is in the range of 95% to 100% of the initial potential. Further, it is preferable to perform the first step, the fifth step of supplying the third potential to the gate electrode to bring the thin film transistor into the third off state, and maintaining the third off state, and the third step. .
According to this configuration, when the measured temperature is outside the measurement range of the first or second temperature measurement, the third temperature measurement is performed in a different measurement range, and the temperature is measured in each measurement range. Since the measurement is made with precision, it is possible to perform precise temperature measurement over a wide temperature range.

Application Example 5 In the temperature measurement method according to the application example described above, it is preferable that the third potential is lower than the second potential.
Although it takes time to measure the low temperature, according to this configuration, as the temperature measurement progresses the first time, the second time, and the third time, the measurement is performed at a lower temperature. Temperature measurement can be performed over a wide range.

Application Example 6 In the temperature measurement method according to the application example described above, it is preferable that the period of the fifth process is longer than the period of the fourth process.
According to this configuration, the measurement time becomes longer as the temperature measurement proceeds from the first time, the second time, and the third time. On average, accurate temperature measurement can be performed over a wide range in a relatively short time.

Application Example 7 In the temperature measurement method according to the application example described above, a temperature sensor including a thin film transistor and a capacitive element in a measurement cell is used, and the temperature sensor is arranged along the first direction and selects the measurement cell. It is preferable that a plurality of measurement cells are arranged along the first direction.
According to this configuration, since a plurality of measurement cells are arranged in the first direction and are individually selected, the spatial distribution of the temperature in the first direction can be measured. Therefore, even if the temperature varies along the first direction, the temperature can be measured quantitatively and accurately as a function of location.

Application Example 8 In the temperature measurement method according to the application example described above, the temperature sensor further includes a second selection circuit that is arranged along a second direction intersecting the first direction and selects a measurement cell. A plurality of measurement cells are preferably arranged along the second direction.
According to this configuration, since a plurality of measurement cells are arranged in the second direction and are individually selected, the spatial distribution of the temperature in the second direction can be measured. Thus, even if the temperature varies along the second direction, the temperature can be measured quantitatively and accurately as a function of location.

Application Example 9 In the temperature measurement method according to the application example, the measurement cell further includes a first thin film transistor and a second thin film transistor, and the first thin film transistor and the second thin film transistor form a differential transistor pair. The gate electrode of the first thin film transistor is preferably connected to one of the source electrode or the drain electrode of the thin film transistor.
According to this configuration, a differential transistor pair is provided in each measurement cell, so that even if the surface temperature sensor has a large area or high definition, the temperature can be measured with high accuracy. Can do.

(Application Example 10) In the temperature measurement method according to the application example, the temperature sensor further includes:
The third thin film transistor includes a fourth thin film transistor, the third thin film transistor is connected to the first thin film transistor, the fourth thin film transistor is connected to the second thin film transistor, and the third thin film transistor and the fourth thin film transistor are The first selection circuit and the second selection circuit are preferably controlled.
According to this configuration, the third thin film transistor and the fourth thin film transistor function as a part of the selection circuit in the first direction and the second direction, and therefore in the first direction and the second direction. Prevents temperature information from interfering.

(Application Example 11) In the temperature measurement method according to the application example, the temperature sensor further includes:
A fifth thin film transistor and a sixth thin film transistor; the fifth thin film transistor and the sixth thin film transistor form a current mirror pair; and a third thin film transistor is disposed between the first thin film transistor and the fifth thin film transistor. The fourth thin film transistor is preferably disposed between the second thin film transistor and the sixth thin film transistor.
According to this configuration, since the thin film transistor group forms a current mirror type differential amplifier circuit, it is possible to amplify after converting the temperature into a voltage. That is, the temperature can be measured accurately.

(Application Example 12) In the temperature measurement method according to the application example, the temperature sensor further includes:
A first power source, a second power source, and a seventh thin film transistor; the first thin film transistor and the second thin film transistor are connected to the first power source; and the fifth thin film transistor and the sixth thin film transistor are connected to the seventh thin film transistor. Preferably, the seventh thin film transistor is connected to the second power source.
According to this configuration, since the seventh thin film transistor can serve as a constant current source, the amplification of the gate potential of the first thin film transistor becomes linear, and the temperature can be accurately measured.

Application Example 13 In the temperature measurement method according to the application example, it is preferable that the fifth thin film transistor, the sixth thin film transistor, and the seventh thin film transistor are N-type, and the second power source is a negative power source.
According to this configuration, a temperature sensor can be realized with an N-type thin film transistor.

Application Example 14 In the temperature measurement method according to the application example, it is preferable that the fifth thin film transistor, the sixth thin film transistor, and the seventh thin film transistor are P-type, and the second power source is a positive power source.
According to this configuration, a temperature sensor can be realized with a P-type thin film transistor.

FIG. 3 is a perspective external view schematically showing the temperature sensor according to the first embodiment. FIG. 3 is a diagram for explaining the measurement principle of the temperature sensor according to the first embodiment. FIG. 3 illustrates a circuit of a temperature sensor according to the first embodiment. FIG. 6 is a diagram for explaining a timing chart when measuring a temperature with the temperature sensor according to the first embodiment. The figure explaining the measurement step at the time of measuring temperature with the temperature sensor concerning Embodiment 1. FIG. The figure explaining the temperature measurement period at the time of measuring temperature with the temperature sensor concerning Embodiment 1. FIG. FIG. 3 is an equivalent circuit diagram when measuring the temperature with the temperature sensor according to the first embodiment. 2A and 2B are diagrams for explaining a planar layout of various circuits used in the temperature sensor according to the first embodiment. FIG. 3A is an output circuit, FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the scales are different for each layer and each member so that each layer and each member can be recognized in the drawing.

(Embodiment 1)
"Temperature sensor overview"
FIG. 1 is a perspective external view schematically showing a temperature sensor according to the present embodiment. Hereinafter, the outline of the temperature sensor will be described with reference to FIG.

The temperature sensor 1 according to this embodiment includes an external controller 7, a substrate 2, and a cable 72. The cable 72 electrically connects the external controller 7 and the board 2. The external controller 7 includes a control device 71 that controls temperature measurement, and an interface and a power source with other electronic devices as necessary. The control device 71 is a central processing unit (
CPU), a storage device (memory), and the like, and executes various programs related to temperature measurement.

The temperature sensor 1 uses a flexible substrate 2 such as a soft plastic film. A plurality of measurement cells (i, j) are arranged in a matrix on the substrate 2 to form a measurement circuit 3. Each measurement cell includes a thin film transistor T0 (hereinafter simply referred to as T0) and a capacitive element Cp (see FIG. 3). In the present application, in order to distinguish the thin film transistor T0 from other thin film transistors, this thin film transistor is named a measurement thin film transistor T0. The capacitive element Cp is connected to one of the source electrode and the drain electrode of the measurement thin film transistor T0. Although the source electrode and the drain electrode of the transistor are switched according to the potential, hereinafter, for convenience of explanation, the electrode to which the capacitor element Cp is connected is used as the drain electrode of the measurement thin film transistor T0. The temperature is measured using a charging process and a detection process. The first step is a charging step in which the measurement thin film transistor is turned on, and one end of the capacitive element Cp is charged to an initial potential (here, the first electrode is a positive power supply potential V _dd ). Next, as a second step, the first potential is supplied to the gate electrode of the measurement thin film transistor T0, thereby bringing T0 into the first off state. The period during which T0 is maintained in the OFF state corresponds to the temperature measurement period. During the measurement period, the potential of the capacitive element Cp increases or decreases due to the OFF current of T0. The temperature is measured using this phenomenon. The temperature is mainly measured by using the phenomenon that the charge charged in the capacitor decreases due to the off-current. On the other hand, the temperature is measured by using the phenomenon that the empty capacitor is charged by the off-current. May be. The third step is to detect the potential of one end of the capacitive element Cp after the measurement period ends, and the detection step is a combination of the second step and the third step.
The potential detected in the detection step is called a first high potential. If this first high potential is different from the initial potential (if the first high potential is less than 95% of the initial potential), the temperature corresponding to this first high potential is queried. On the other hand, if the first high potential is substantially equal to the initial potential (when the first high potential is in the range of 95% to 100% of the initial potential), the charging step and the detection step are repeated. At this time, the potential supplied to the gate electrode of T0 during the measurement period is set to a second potential different from the first potential. In this way, the temperature of the part where the measurement thin film transistor T0 is disposed is measured.

Returning to FIG. 1, the description will be continued.
In addition to the measurement circuit 3, the substrate 2 includes an output circuit 4, a first selection circuit 51, and a first processing circuit 5.
2, a second selection circuit 61, and a second processing circuit 62 are provided. The plurality of measurement cells arranged in the measurement circuit 3 are sequentially selected by the first selection circuit 51 and the second selection circuit 61 arranged on the outer periphery of the measurement circuit 3. One side of the substrate 2 in a first direction (in a direction parallel to the x-axis,
Another direction intersecting (substantially orthogonal to) the first direction is the second direction (y)
The first selection circuit 51 and the first processing circuit 52 are formed along the first direction outside the measurement circuit 3, and the second selection circuit 61. And second processing circuit 6
2 is formed along the second direction outside the measurement circuit 3. A plurality of measurement cells are formed along the first direction, and are selected in the first direction by the first selection circuit 51. Similarly, a plurality of measurement cells are formed along the second direction and selected by the second selection circuit 61 in the second direction. The selected measurement cell is connected to the output circuit 4 and temperature measurement is performed. In this way, the temperature is sequentially measured in the measurement cells arranged in a matrix, and a surface distribution related to the temperature is obtained.

"Measurement Principle"
FIG. 2 is a diagram for explaining the measurement principle of the temperature sensor according to this embodiment. Hereinafter, FIG.
The principle of measuring the temperature will be described with reference to FIG.

FIG. 2 shows how the transfer characteristics of an N-type thin film transistor have temperature dependence.
Transistor transfer characteristics are generally classified into an on state, an off state, and a sub-threshold state.
The on state is a state where a channel is formed in at least a part of the channel formation region and the drain conductance is high. That is, the gate voltage is higher than the threshold voltage, and in the case of FIG.
The gate voltage is about 1.5 V or more of the threshold voltage. In a thin film transistor using silicon, the channel has the same conductivity type as the source / drain region. The source-drain current in the on state is called on-current. The off state is a state where the rectifying action is working and the drain conductance is low. In a thin film transistor using silicon, the channel formation region is intrinsic or reversely conductive with the source / drain region, and the PN at the drain end
A reverse bias is applied to the junction. The gate voltage in the off state is lower than the voltage at which the transfer characteristic rises rapidly (in the case of FIG. 2, the gate voltage is about 0V). The source-drain current in the off state is called off-current. The sub-threshold state is a state between the on state and the off state, and in the case of FIG. 2, the gate voltage is between about 0V and about 1.5V. The above is a general definition, but the OFF state of the present application includes a general OFF state and a sub-threshold state, and indicates a state other than a general ON state. That is, the OFF state of the present application refers to a state where the gate voltage is lower than the threshold voltage. The gate voltage lower than the threshold voltage means that the gate voltage is on the negative side of the threshold voltage in the N-type thin film transistor, and the gate voltage is on the positive side of the threshold voltage in the P-type thin film transistor. To do. Note that the gate voltage V _gs is a gate potential with respect to the source potential. Hereinafter, in this specification, a potential that causes an on state of a transistor when applied to a gate electrode is referred to as a high potential, and a gate potential that causes an off state is referred to as a low potential.

Both the on state and the off state have temperature dependence, but the temperature dependence in the off state is strong. This is because the off-current value changes most sensitively to the spread of the Fermi function. The off-current is caused by a mechanism such as heat generation of electron-hole pairs, phonon assisted tunneling accompanied by Pool Frenkel effect, or band-to-band tunneling. The Fermi function changes exponentially even with a slight change in temperature, and strongly influences these mechanisms (particularly, heat generation of electron-hole pairs and phonon assisted tunneling accompanied by the Pool Frenkel effect). Therefore, the temperature dependence of the off-current value becomes extremely strong. Actually, from FIG. 2, the off-current at 200 ° C. is 50
It can be seen that it is about 1000 times the off current of ℃. On the other hand, the on-current increases only several times at the same temperature change. That is, the off-current is nearly 1000 times more sensitive to temperature than the on-current. Roughly speaking, every time the temperature rises by 50 ° C., the off-current increases by a factor of 10, so that if the temperature only rises by 5 ° C., the off-current increases by 26%. In short, even with only a slight temperature change, the off-current value shows a large change that can be measured, so that highly accurate temperature measurement can be realized.

The temperature is measured using a phenomenon in which the charge initially charged in the capacitor increases or decreases due to the off-current. Since the off-state current of the measurement thin film transistor T0 changes drastically according to the temperature, the amount of charge accumulated in the capacitor also changes according to the temperature. The temperature is measured by measuring this change in charge amount (or change in capacitance potential). In this embodiment, the capacitance potential is set to the gate potential of the first thin film transistor T1, and this is compared with the gate potential of the second thin film transistor. That is, the second thin film transistor T2 operates as a reference transistor. The difference between the two gate potentials is differentially amplified, and the temperature in the measurement cell is output as a voltage value or a current value.

"circuit"
FIG. 3 is a diagram for explaining a circuit of the temperature sensor according to the present embodiment. Hereinafter, the circuit of the temperature sensor will be described with reference to FIG. As for the source and drain of the N-type thin film transistor, the higher the potential, the higher the potential becomes the drain, and the lower the potential becomes the source. For reference, FIG. 3 shows the source and drain of each thin film transistor as s and d, respectively.

First, a description will be given with reference to FIG.
The temperature sensor 1 includes a measurement circuit 3, an output circuit 4, a first selection circuit 51, a first processing circuit 52, a second selection circuit 61, and a second processing circuit 62. In the measurement circuit 3, the measurement cell (i, j) has M
They are arranged in a matrix of rows and N columns. M and N are integers of 1 or more (1 ≦ i ≦ M, 1 ≦ j ≦
N). The first selection circuit 51 selects one specific row line from the M row lines R (i) in the first direction. Therefore, the first selection circuit 51 is also a row selection circuit. For the first selection circuit 51, a shift register or a decoder is used. The first processing circuit 52 processes the selection signal from the first selection circuit 51 so as to be suitable for measurement. Specifically, a level shifter for converting the selection potential and a buffer for selecting a row line stably at high speed are provided. The second selection circuit 61 selects one specific column line from the N column lines C (j) in the second direction. Therefore, the second selection circuit 61 is also a column selection circuit. For the second selection circuit 61, a shift register or a decoder is used. The second processing circuit 62 processes the selection signal from the second selection circuit 61 so as to be suitable for measurement. Specifically, a level shifter for converting the selection potential and a buffer for selecting the column line stably at high speed are provided.

Returning to FIG. 3, the description will be continued.
The second processing circuit 62 includes column selection transistors T3C and T4C in addition to the circuit described above. Column selection transistors T3C and T4C are provided in pairs for each column. The output circuit 4 becomes a current source for the differential transistor pair, and LDOUT and XLDOUT.
As a result, the measurement result is output. Among these circuits, the measurement circuit 3, the output circuit 4, and the column selection transistors T3C and T4C in the second processing circuit 62 are formed of thin film transistors. In the present embodiment, in addition to these, the first selection circuit 51, the first processing circuit 52, and the second selection circuit 6
1 is also formed of thin film transistors (N-type and P-type) having a CMOS configuration, but column selection among the first selection circuit 51, the first processing circuit 52, the second selection circuit 61, and the second processing circuit 62. Circuits other than the transistors T3C and T4C may be formed by an external silicon IC chip.

In the measurement cell, a measurement thin film transistor T0, a first thin film transistor T1, and a second thin film transistor T2 are arranged. The first thin film transistor T1 and the second thin film transistor T2 form a differential transistor pair and are arranged symmetrically with each other. That is, the drains of both transistors are connected to the first power supply and are arranged in parallel with the power supply.
The first power source is a positive power source _Vdd . The gate of the first thin film transistor T1 is connected to the drain of the measurement thin film transistor T0. A capacitive element Cp is connected to the drain of the measurement thin film transistor T0. The capacitive element Cp sandwiches the dielectric film between the first electrode and the second electrode. In FIG. 3, the first electrode is connected to the drain of the measurement thin film transistor T0 and the gate of the first thin film transistor T1, and the second electrode Is connected to the second power supply. The second power supply is in this case a negative power supply V _ss . The source of the measurement thin film transistor T0 is connected to the charging column line CC, and the gate is connected to the charging row line RC. A reference signal V _ref is supplied to the gate of the second thin film transistor T2.

In the measurement cell (i, j) located in the i row and the j column, there are further row selection transistors T3R and T4.
R is provided. The column selection transistor T3C and the row selection transistor T3R form a third thin film transistor T3. The drain of the row selection transistor T3R is connected to the source of the first thin film transistor T1, and the source is j through the odd column line CO (j) of the jth column.
Connected to the drain of the column selection transistor T3C of the column, the gate is the row line R (i) of the i-th row
Connect to. Similarly, the column selection transistor T4C and the row selection transistor T4R form a fourth thin film transistor T4. The drain of the row selection transistor T4R is connected to the source of the second thin film transistor T2, the source is connected to the drain of the j-th column selection transistor T4C via the even-numbered column line CE (j) of the j-th column, and the gate is Connected to row line R (i) of the i-th row.

The temperature sensor 1 further includes a fifth thin film transistor T5 and a sixth thin film transistor T6 in the output circuit 4, and the fifth thin film transistor T5 and the sixth thin film transistor T6 form a current mirror pair. In the current mirror pair, the sources of both transistors are connected in common, and the same potential is applied to the gate, so that during saturation operation (V _ds > V _gs −V _th > 0),
Even if the drain potentials of both transistors are slightly different, they are transistor pairs that pass the same current. Here, the gates of both thin film transistors are connected to the drain of the fifth thin film transistor. Further, the drain of the fifth thin film transistor T5 is connected to the source of the column selection transistor T3C, and the drain of the sixth thin film transistor T6 is connected to the source of the column selection transistor T4C.

The temperature sensor 1 further includes a seventh thin film transistor T7 in the output circuit 4. The seventh thin film transistor T7 is a current source transistor. A current source transistor is a transistor that performs a saturation operation and always supplies a constant current even if the drain potential slightly varies. The source of the fifth thin film transistor T5 and the source of the sixth thin film transistor T6 are connected to the drain of the seventh thin film transistor T7, and the source of the seventh thin film transistor T7 is connected to the second power source. The second power source is a negative power source V _ss . The first control signal Cnt1 is supplied to the gate of the seventh thin film transistor T7. Since the fifth thin film transistor T5 and the sixth thin film transistor T6 always pass the same current and the seventh thin film transistor T7 supplies a constant current, the fifth thin film transistor T5 and the sixth thin film transistor T6 always have the same current (the seventh Half of the current through the thin film transistor T7).

The third thin film transistor T3 is always disposed between the first thin film transistor T1 and the fifth thin film transistor T5 while changing the column selection transistor and the row selection transistor every time column selection or row selection is performed. The thin film transistor T1 and the fifth thin film transistor T5 can be electrically connected. Similarly, the fourth thin film transistor T4 is always disposed between the second thin film transistor T2 and the sixth thin film transistor T6 while changing the column selection transistor and the row selection transistor every time the column selection or the row selection is performed. ,
The second thin film transistor T2 and the sixth thin film transistor T6 can be electrically connected. That is, when a selection signal (high potential signal) is supplied to the i-th row line R (i), the first thin film transistor T1 arranged in the i-th measurement cell is electrically connected to the odd-numbered column line CO. Connected,
The second thin film transistor T2 is electrically connected to the even column line CE. Conversely, row line R (i)
When a non-selection signal (low potential signal) is input to the first thin film transistor T1, the odd-numbered column line CO is electrically insulated, and the second thin film transistor T2 and the even-numbered column line CE are electrically insulated.

In a state where the selection signal is supplied to the row line R (i), the selection signal (
When the high potential signal) is input, the column selection transistor T3C in the jth column is turned on.
The odd column line CO of the column and the fifth thin film transistor T5 are connected. As a result, the first thin film transistor T1 and the fifth thin film transistor T5 located in the measurement cell (i, j) in i row and j column are electrically connected. Similarly, a selection signal (high potential signal) is applied to the column line C (j) of the j-th column.
Since the column selection transistor T4C in the j-th column is turned on, the even-numbered column line CE in the j-th column and the sixth thin film transistor T6 are connected. As a result, the measurement cell (i row j column) (
The second thin film transistor T2 and the sixth thin film transistor T6 located at i, j) are electrically connected. Conversely, when a non-selection signal (low potential signal) enters the column line C (j) of the jth column,
Since the column selection transistors T3C and T4C in the jth column are turned off, the output circuit 4 and j
The odd-numbered column line CO in the column and the even-numbered column line CE in the j-th column are electrically insulated. As described above, the measurement cell selected by the row line and the column line among the plurality of measurement cells is connected to the output circuit 4. Measurement result from the output circuit 4, the drain potential V ₆ of the sixth thin film transistor T6 is output as LDOUT, drain potential V ₅ of the fifth TFT T5 is output as XLDOUT.

The selection signal or the non-selection signal supplied to the column line C (j) level-shifts the output from the second selection circuit 61 as necessary, and the output from the level shifter is reinforced by a buffer. That is, the column selection transistors T3C and T4C are controlled by the second selection circuit 61.
The selection signal or the non-selection signal supplied to the row line R (i) shifts the output from the first selection circuit 51 as necessary, and the output from the level shifter is reinforced by a buffer. . That is, the row selection transistors T3R and T4R are controlled by the first selection circuit 51. Here, the column selection is performed with the row selected, but the row selection may be performed with the column selected. The odd-numbered column line here is simply a name, which means a column line provided in an odd-numbered transistor row (T1 or T3), and an even-numbered column line is also simply a name and has an even-numbered transistor row ( It means a column line provided at T2 or T4).

"Measurement method"
FIG. 4 is a diagram for explaining a timing chart for driving the circuit when the temperature is measured by the temperature sensor according to the present embodiment. FIG. 5 is a diagram for explaining measurement steps when measuring the temperature with the temperature sensor according to the present embodiment. FIG. 6 is a diagram for explaining a temperature measurement period when the temperature is measured by the temperature sensor according to the present embodiment. Hereinafter, a measurement method using a temperature sensor will be described with reference to FIGS.

The temperature measurement is performed using one to a plurality of temperature measurement periods. As shown in FIG. 4, one temperature measurement period includes a preparation period PP, a measurement period MP, and an output period OP. During the preparation period PP, the measurement thin film transistor T0 is turned on, and the first thin film transistor T1 and the capacitive element Cp
Are charged to a predetermined potential. During the measurement period MP, the measurement thin film transistor T0 is turned off, and the previously charged charge is leaked from the capacitive element Cp. Since the leakage charge amount is temperature-dependent, the gate potential of the first thin film transistor T1 decreases according to the temperature. Output period OP
The output corresponding to the lowered gate potential is taken out from each measurement cell. This is the basic cycle of one temperature measurement period.

In actual temperature measurement, first, prior to temperature measurement, a reference signal V _ref supplied during measurement
Determine the potential value. As described above, the temperature sensor 1 compares the electrical characteristics of the second thin film transistor T2 that is the reference transistor with the electrical characteristics of the first thin film transistor T1 whose gate potential changes according to the temperature. On the other hand, a thin film transistor generally has slightly different electrical characteristics for each transistor. In order to correct this, the value of the reference signal V _ref corresponding to the reference temperature is determined for each measurement cell. A specific method for determining the value of the reference signal V _ref will be described below.

(1) The temperature sensor 1 is installed in a heat reservoir at a reference temperature so that all measurement cells are at the reference temperature. The reference temperature is appropriately set within the measurement target temperature range. It is desirable that the reference temperature is approximately the lower limit of the range. For example, when the temperature range to be measured is a winter temperature in a cold region and is expected to be in the range of −20 ° C. to 30 ° C., the reference temperature is set to about −20 ° C.

(2) The temporary reference high potential H _r expressed by Equation 1 is set as the selection potential of the reference signal V _ref in all measurement cells.

ここでＶ_ddは正電源電位、Ｖ_thは薄膜トランジスターの閾値電圧の平均値、δは０．０
５Ｖから０．３Ｖ程度の小さい電圧値である。仮の基準高電位Ｈ_rは、例えばＨ_r＝４．０
５Ｖである。

Here, V _dd is a positive power supply potential, V _th is an average value of threshold voltages of thin film transistors, and δ is 0.0
It is a small voltage value of about 5V to 0.3V. The temporary reference high potential H _r is, for example, H _r = 4.0.
5V.

(3) The temperature is measured by a method to be described later, and the time of the measurement period MP is determined so that the average value of the output results (V ₅ -V ₆ ) from all the measurement cells becomes almost zero. In other words, the length of the measurement period MP is determined so as to satisfy Formula 2. Almost zero means that the average value of the output result is approximately -0.4V to +0.4
It means entering the range of V.

(4) The temperature of the heat reservoir is again measured using the time of the measurement period MP thus determined. At that time, so that the LDOUT output and the XLDOUT output become equal (V
A reference high potential value of V _ref provided for each measurement cell is determined and stored in a storage device provided in the external controller 7 (so that ₅ = V ₆ ). Thereafter, the temperature sensor 1 is placed on the measurement target, and measurement is started.

Next, the basic cycle of one temperature measurement period will be described. In the temperature measurement, the external controller 7 supplies appropriate signals and power to the first selection circuit 51, the first processing circuit 52, the second selection circuit 61, the second processing circuit 62, and the like. As a result, each row line or column is supplied. The following signals shown in FIG. 4 are supplied to the line, the output circuit 4 and the like.

The first step is performed during the preparation period PP. First, the charging column line CC is set to the positive power supply potential V _dd .
Then the charging row line RC and the second high potential H _2, and turned on the measurement TFT T0. Next, the charging row line RC is returned to the negative power supply potential V _ss . Next, the potential of the charging column line CC is returned to the negative power supply potential V _ss . Through this first step, the first electrodes of the capacitive elements Cp of all measurement cells are charged to the initial positive power supply potential V _dd . The negative power supply potential V _ss is lower than the positive power supply potential V _dd , for example, V _ss = 0V (ground potential). The positive power supply potential is, for example, V _dd = 4.8V
The second high potential is, for example, H ₂ = 7.3V.

In the measurement period MP, the charging column line CC is set to the negative power supply potential V _ss . The charging row line RC is set to a low potential L. As a result, the measurement thin film transistor T0 is turned off and maintained in the off state over the measurement period MP. During the measurement period MP, an off-current corresponding to the temperature leaks from the first electrode to the charging column line CC. Thus, at the end of the measurement period MP, the first thin film transistor T
The gate potential of ₁ becomes the first high potential H ₁ . This is the second step.

After the measurement period MP ends, the process proceeds to the output period OP. As the third step in the output period OP,
The potential of the first electrode is detected. That is, when the output period OP is entered, the third high potential H ₃ is supplied to the first control signal Cnt1. This value is, for example, H ₃ = 1.6V. In the output period OP, first, the row lines R (1) to R (M) are alternately selected one by one. Usually the first row line R (1)
To the M-th row line R (M) of the last row. A selection signal potential (second high potential H ₂ ) is selectively supplied to the row line, and a non-selection signal potential (negative power supply potential V _ss ) when not selected.
Is supplied.

In a period in which one row line is selected, column lines (C (1) to C (N)) are alternately selected one by one. Normally, the selection is made in order from the first column line C (1) to the Nth column line C (N) of the last column. A selection signal potential (second high potential H ₂ ) is selectively supplied to the column line, and a non-selection signal potential (negative power supply potential V _ss ) is supplied when not selected.

In this way, one specific measurement cell is selected from the plurality of measurement cells. The reference high potential corresponding to the selected measurement cell is read from the storage device of the external controller 7, and V _{re
Let f} . Since the reference high potential supplied to the gate of the second thin film transistor T2 is set so that the output voltage is V ₅ = V ₆ if the temperature of the measurement cell is equal to the reference temperature,
When V ₅ to read the value of V _6, seen temperature of the selected measurement cell. For example, if the selected measurement cell is lower than the reference temperature, the leakage current is small, so the first high potential (the gate potential of the first thin film transistor T1) is the reference high potential (the gate potential of the second thin film transistor T2). ). As a result, the potential of LDOUT (V ₆ ) becomes low and XLDOUT (
Since the potential of V ₅₎ increases, the value of V ₅ -V ₆ becomes positive. On the other hand, if the selected measurement cell is higher than the reference temperature, the potential of LDOUT (V ₆ ) becomes high and XLDOUT (V ₅
) Is low, the value of V ₅ -V ₆ becomes negative. In this measurement method, the charge remaining in the capacitive element Cp and the gate capacitance of the first thin film transistor T1 is maintained throughout the output period. In other words, temperature measurement is performed non-destructively (measurement does not affect the object to be measured, in other words, without changing the amount of charge), and therefore, even if the temperature sensor becomes a large area, it becomes high definition. However, accurate measurement will be performed.

The above is the basic cycle of one temperature measurement period, but this may need to be repeated several times. The temperature measurement is performed in the steps shown in FIG. Specifically, the control device 71 executes a program including a setting step S1, an execution step S2, a determination step S3, a reference step S4, a determination step S5, and a resetting step S11.

The setting step S1 sets the temperature measurement condition to the first condition. Measurement condition is measurement period M
A value of a low potential L applied to the charging row line RC and a time length of the measurement period MP. Under the first condition, the low potential L is the first potential, and the time length is determined so that the average value of the output results (V ₅ -V ₆ ) is almost zero (MP = t ₀ ). The first potential is a gate voltage V _{min at} which the transfer characteristic shown in FIG. In this embodiment, V _min = V _ss = 0V.

In the execution step S2, the basic cycle of the first measurement period is executed under the measurement conditions thus set. That is, the first step, the second step, and the third step are performed. In the second step, the first potential is supplied to the gate electrode of the measurement thin film transistor T0, and the measurement thin film transistor T0.
Is maintained in the first off state during the measurement period MP (= t ₀ ).

In the determination step S3, it is determined whether to end the temperature measurement in the basic cycle of the first measurement period or to execute the basic cycle of the measurement period again. That is, the first high potential H ₁ is equal to the initial potential V _in.
If it is less than 95%, it is determined to end the temperature measurement, and if it is 95% or more, it is determined to execute the basic cycle of the measurement period again. This is because the first high potential H ₁ is equal to the initial potential V _i.
If it is less than 95% of _n , the first high potential H ₁ and the temperature can be associated with high accuracy in the next reference step S4, but if it is 95% or more, the error increases. For this reason, if it is 95% or more, the measurement condition is changed and remeasured.

If it is determined in step S3 that the temperature measurement is finished, the process proceeds to reference step S4.
The storage device of the external controller 7 is provided with a look-up table for associating the first high potential H ₁ with the temperature, and referring to this is the reference step S4. In the determination step S5, the temperature thus measured is determined. That is, the measured temperature is output or stored in a storage device.

In the first high potential H ₁ at decision step S3 has not been reduced from an initial potential V _in (if a first high potential H ₁ and the initial potential V _in is substantially equal), the process proceeds to the re-setting step S11. In the resetting step S11, the measurement condition in the next temperature measurement period is changed from the previous measurement condition. That is, when the previous measurement was performed under the first condition, the second condition different from the first condition is reset. The low potential L is lowered by ΔV from the previous time and becomes the second potential. In addition, the measurement period MP may be made longer by Δt than the previous time. These are the second condition. After the resetting step S11, the process proceeds again to the executing step S2. In the second execution step, the basic cycle of the second measurement period is executed. That is, the first step, the fourth step, and the third step are performed. In the fourth step, the second potential is supplied to the gate electrode of the measurement thin film transistor T0, and the measurement thin film transistor T0 is maintained in the second off state during the measurement period MP (= t ₀ + Δt). Next, the process proceeds to decision step S3.

Result of executing the second time base cycle, when the first high potential H ₁ is more than 95% of initial potential V _in, the process proceeds from decision step S3 to reconfigure the step S11. In the resetting step S11, the measurement conditions in the third temperature measurement period are changed from the second measurement conditions. That is, the measurement condition is reset to a third condition different from the second condition. The low potential L is lowered by ΔV from the previous time,
Third potential. In addition, the measurement period MP may be made longer by Δt than the previous time. These are the third condition. After the resetting step S11, the process proceeds again to the executing step S2. In the third execution step, the basic cycle of the third measurement period is executed. That is, the first step, the fifth step, and the third step are performed. In the fifth step, the third potential is supplied to the gate electrode of the measurement thin film transistor T0, and the measurement thin film transistor T0 has the measurement period MP (= t ₀ + 2Δ).
The third off state is maintained during t). Next, the process proceeds to decision step S3. Hereinafter, the basic cycle of the same measurement period is rotated as necessary, for the fourth time, the fifth time, and the sixth time.

The result of each measurement, when the first high potential H ₁ and the initial potential V _in is approximately equal, which means the temperature which is a measurement target is lower than the measurement range of the measurement. Therefore, the temperature measurement range for the next measurement needs to be lower than the temperature measurement range for the measurement performed immediately before. Specifically, the temperature measurement range according to the second condition is set to a lower temperature side than the temperature measurement range according to the first condition, and the temperature measurement range according to the third condition is more than the temperature measurement range according to the second condition. Further, it is on the low temperature side.

FIG. 6 corresponds to this. In FIG. 6, the first temperature measurement period to the third temperature measurement period are depicted. The measurement condition of the measurement period MP1 in the first temperature measurement period is determined by the first condition. Similarly, the measurement condition of the measurement period MP2 in the second temperature measurement period is determined by the second condition, and the measurement condition of the measurement period MP3 in the third temperature measurement period is determined by the third condition. Than the low-potential (first potential L ₁₎ the first condition is determined, a low potential second condition is determined (second potential L ₂₎ it is lower, the low potential to the second condition is determined (second potential L ₂ ) Is lower than the low potential (third potential L ₃ ) determined by the third condition. For example, L ₁ = 0V, L ₂ = −2.5V, and L ₃ = −5V. or,
The measurement period MP2 defined by the second condition is longer than the measurement period MP2 defined by the first condition, and the measurement period MP3 defined by the third condition is longer than the measurement period MP2 defined by the second condition. For example, MP1 = 2.5 milliseconds, MP2 = 5 milliseconds, and MP3 = 7.5 milliseconds. As shown in FIG. 2, as the gate voltage decreases, the off-current increases (especially at low temperatures). By doing this, the temperature measurement range under the second condition is the temperature measurement under the first condition. It shifts to the lower temperature side than the range. Similarly, the temperature measurement range of the third condition is shifted to the lower temperature side than the temperature measurement range of the second condition.

"how to use"
When using a temperature sensor, a low frequency measurement mode and a high frequency measurement mode may be provided. The low frequency measurement mode is a period in which measurement is repeated at low frequency in preparation for the high frequency measurement mode. In the high frequency measurement mode, the temperature sensor repeats measurement at high frequency. For example, when a temperature sensor is used in a freezing prevention zone of a water supply, the low frequency measurement mode is set during a warm day, and the high frequency measurement mode is set during a period when the temperature starts to decrease and is likely to freeze. Or
The low frequency measurement mode is selected when the temperature change is slow, and the high frequency measurement mode is set when the temperature change is slow.

In both the low frequency measurement mode and the high frequency measurement mode, the temperature sensor performs the measurement operation by the method described in the “Measurement Method” section above, but the measurement frequency is different. In the low frequency measurement mode, the number of measurements performed within a unit time is small, and in the high frequency measurement mode, this is high. When a period for selecting and measuring all the measurement cells arranged in M rows and N columns is a frame period, and a time from one frame period to the next frame period is a standby period, the measurement frequency is the frame period and the standby period. The reciprocal of the sum of the period (1 / (frame period + standby period)).
That is, the measurement frequency in the high frequency measurement mode is set larger than the measurement frequency in the low frequency measurement mode. As an example, in the high-frequency measurement mode, the standby period is set to zero, and the frame frequency (the reciprocal of the frame period) and the measurement frequency are matched. On the other hand, the standby period in the low frequency measurement mode is set to a relatively long time of several milliseconds or more (for example, 1 second), and the measurement frequency in the low frequency measurement mode is made to substantially coincide with the reciprocal of the standby period.

By providing such a low frequency measurement mode and a high frequency measurement mode, power consumption can be reduced in the low frequency measurement mode, and time resolution can be maximized in the high frequency measurement mode. . Here, the frame period is the same in both the low frequency measurement mode and the high frequency measurement mode, and the standby period is changed. However, the present invention is not limited to this, and the frame period may be changed between the low frequency measurement mode and the high frequency measurement mode. Absent. That is, the clock frequency in the high frequency measurement mode may be set higher than the clock frequency in the low frequency measurement mode to increase the measurement frequency in the high frequency measurement mode.

"Transistor size and driving conditions"
FIG. 7 is an equivalent circuit diagram when the temperature is measured by the temperature sensor according to the present embodiment.
Next, with reference to FIG. 7, conditions for realizing high-sensitivity and high-performance measurement are shown. Hereinafter, the first thin film transistor T1 is abbreviated as T1. Similarly, the second thin film transistor T2 to the seventh thin film transistor T7 are also abbreviated. Note that represents a drain potential of T3 in V _3, represents the drain potential of T4 drain potential of V _4, T7 V ₇ at.

Since T1 and T2 are differential input pairs, nonlinear operation such as saturation operation is desirable. T3 and T4 are selection transistors, and linear operation is desirable from the viewpoint of widening the output potential range.
Thus, for the T3 and T4, the source drain voltage V _ds is as small as possible, V ₃ =
V ₅ and V ₄ = V ₆ become desirably. T5 and T6 must be in saturation with the current mirror pair. Also, since T7 is a current source transistor, it must be in an arrow-saturated operation.

  First, the symbol of Equation 3 is used to express the current equation of the transistor.

ここでＷはトランジスターチャンネル形成領域の幅、Ｌはトランジスターチャンネル形
成領域の長さ、Ｃ_oxは単位面積当たりのゲート絶縁膜容量、μは移動度である。すると、
飽和特性の近似式は数式４で表される。

Here, W is the width of the transistor channel formation region, L is the length of the transistor channel formation region, C _ox is the gate insulating film capacitance per unit area, and μ is the mobility. Then
The approximate expression of the saturation characteristic is expressed by Expression 4.

又、線型特性の近似式は数式５で表される。

Further, the approximate expression of the linear characteristic is expressed by Expression 5.

本実施形態では薄膜トランジスターの閾値電圧をＶ_thで表し、薄膜トランジスター間の
Ｖ_th変動は僅かであると近似する。即ち、Ｔ１からＴ７のＶ_thは総て等しいと近似する。
又、Ｖ_thは正であるとし、全体の電流（Ｔ７の電流）を２Ｉとする。まず、Ｔ１からＴ７
のＺをＺ₁からＺ₇で表し、これらを数式６の関係とする。

In this embodiment, the threshold voltage of the thin film transistor is represented by V _th , and it is approximated that the V _th variation between the thin film transistors is slight. That is, it is approximated that V _{th of} T1 to T7 are all equal.
Further, it is assumed that V _th is positive, and the entire current (current of T7) is 2I. First, from T1 to T7
Z is represented by Z ₁ to Z ₇ , and these are represented by the relationship of Equation 6.

数式６が満たされていると、Ｔ１のゲート電位Ｈ₁とＴ２のゲート電位Ｈ_rとの差は線型
増幅されて出力される。以下、各トランジスターに求められる駆動条件を検討する。

If Equation 6 is satisfied, the difference between the gate potential H _r of the gate potential H ₁ and T2 T1 is output is linearly amplified. Hereinafter, driving conditions required for each transistor will be examined.

(1) The saturation operation of T1 is desirable. Therefore, it is desirable that the saturation conditions represented by Expression 7 and Expression 8 are satisfied.

その結果、Ｔ１のドレイン電流は次式となる。

As a result, the drain current of T1 is as follows.

(2) Saturation operation is desirable for T2. Therefore, it is desirable that the saturation condition represented by Expression 10 and Expression 11 is satisfied.

その結果、Ｔ２のドレイン電流は次式となる。

As a result, the drain current of T2 is as follows.

(3) T3 is preferably linear. Therefore, it is desirable that the linear condition expressed by Equation 13 is satisfied.

その結果、Ｔ３のドレイン電流は次式となる。

As a result, the drain current of T3 is as follows.

(4) T4 is preferably linear. Therefore, it is desirable that the linear condition expressed by Equation 15 is satisfied.

その結果、Ｔ４のドレイン電流は次式となる。

As a result, the drain current of T4 is as follows.

(5) It is desirable that T5 operates in saturation. Therefore, it is desirable that the saturation condition expressed by Equation 17 is satisfied.

その結果、Ｔ５のドレイン電流は次式となる。

As a result, the drain current of T5 is as follows.

(6) It is desirable that T6 operates in saturation. Therefore, it is desirable that the saturation condition expressed by Equation 19 and Equation 20 is satisfied.

その結果、Ｔ６のドレイン電流は次式となる。

As a result, the drain current of T6 is as follows.

(7) It is desirable for T7 to perform a saturation operation. Therefore, it is desirable that the saturation condition expressed by Equation 22 is satisfied.

その結果、Ｔ７のドレイン電流は次式となる。

As a result, the drain current of T7 is as follows.

ここで、数式２２を満たす為に、数式２４とする。

Here, in order to satisfy Expression 22, Expression 24 is used.

δは例えば０．１Ｖ程度で、容易に飽和条件を満たすには０．３Ｖ程度未満の正の値が
理想である。

For example, δ is about 0.1V, and a positive value less than about 0.3V is ideal for easily satisfying the saturation condition.

  Next, in order to satisfy Expressions 13 and 15, Expression 25 is used.

これにより、少なくとも数式２６と数式２７とが満たされる様になる。

As a result, at least Expressions 26 and 27 are satisfied.

  From Equation 23 regarding T7 and Equation 16 regarding T4, the following equation is obtained.

この数式２８に数式２４と数式２５とを適応すると、次の様になる。

Applying Equation 24 and Equation 25 to Equation 28 yields the following.

数式２９の右辺に関しては、数式３０を考慮する。

For the right side of Equation 29, Equation 30 is considered.

ここで数式３１とする。

Here, Equation 31 is used.

こうすれば、数式３２が得られる。

In this way, Expression 32 is obtained.

即ち、Ｔ４はゲート電圧がＶ_th＋１Ｖ以上ならば、線型動作する。更に、Ｔ４での電位
降下を確実に０．１Ｖ未満と小さくし、Ｔ４を線型動作させる為には、概ね次式が満たさ
れれば良い。

That is, T4 operates linearly when the gate voltage is V _th + 1V or more. Furthermore, in order to reliably reduce the potential drop at T4 to less than 0.1 V and to make T4 perform a linear operation, the following equation should generally be satisfied.

数式３３は数式３４と変形される。

Equation 33 is transformed to Equation 34.

この場合、数式３５の関係が得られる。

In this case, the relationship of Formula 35 is obtained.

即ち、明らかに線型条件（数式１５）は満たされる。

That is, the linear condition (Formula 15) is clearly satisfied.

Next, the configuration is determined to satisfy all desirable conditions. Formula 36 is given for Formula 23 related to T7 and Formula 21 related to T6.

こうすると、数式２１と数式２３とから数式３７が得られる。

In this way, Expression 37 is obtained from Expression 21 and Expression 23.

  Next, Equation 38 is given for Equation 9 relating to T1 and Equation 18 relating to T5.

こうすると、数式３９が得られる。

In this way, Equation 39 is obtained.

Ｔ７とＴ４の議論（数式２８から数式３５までの議論）により、数式４０と数式４１で
表される関係になっている。

Based on the discussion of T7 and T4 (discussion from Equation 28 to Equation 35), the relationship is expressed by Equation 40 and Equation 41.

数式３９に数式４１を代入し、数式３７と連立させると、数式４２と数式４３の解が得
られる。

By substituting Equation 41 into Equation 39 and simultaneously with Equation 37, the solutions of Equation 42 and Equation 43 are obtained.

  From Expression 12 regarding T2 and Expression 21 regarding T6, Expression 44 is obtained.

数式４４に数式３７と数式４０とを代入すると、数式４５が得られる。

Substituting Equation 37 and Equation 40 into Equation 44 yields Equation 45.

The following shows how to satisfy each of the conditions that should be satisfied in order to realize high-sensitivity and high-performance measurement.

  Formula 7 as a preferred condition: Formula 7 is expressed by Formula 46 from Formula 41 and Formula 42.

  Formula 10 as a suitable condition: Formula 10 is expressed by Formula 46 from Formula 40 and Formula 44.

Formula 8 as a preferred condition: Formula V is positively satisfied if Formula 47 holds because V _th is positive.

Formula 11 as a preferred condition: Since Formula 11 is positive in V _th , if Formula 48 holds,
Surely satisfied.

Formula 13 and Formula 15 as preferred conditions: Formula 13 and Formula 15 are Formula 24 and Formula 3
Filled with 4.

Formula 17 as a preferred condition: Formula 17 is expressed by Formula 46 from Formula 42 and Formula 43.

Formula 19 as a preferred condition: Formula 19 is expressed by Formula 49 from Formula 42 and Formula 45.

従って、計測温度が基準温度よりも高温の時の方が低温の時よりも高精度に温度計測が
なされる。その意味では、基準温度は測定対象温度範囲の下限値に設定するのが好ましい
。

Therefore, temperature measurement is performed with higher accuracy when the measured temperature is higher than the reference temperature than when the measured temperature is lower. In that sense, the reference temperature is preferably set to the lower limit value of the measurement target temperature range.

  Formula 22 as a preferred condition: Formula 24 to Formula 22 become Formula 50.

これに数式４３を適応すると、数式２２は、数式５１となる。

Applying equation 43 to this, equation 22 becomes equation 51.

数式２４により、これは、数式５２を意味する。

According to Equation 24, this means Equation 52.

From Equation 47 and Equation 52, the preferred condition for H ₁ is Equation 53.

In order to satisfy the right side of Formula 53, the gate potential of T1 is charged to V _dd during the preparation period PP,
Discharge during the measurement period MP. When the first high potential H ₁ is equal to the reference high potential H _r , the output (V ₅
Since −V ₆ ) becomes zero, in order to make it easy to satisfy the left side of the first high potential H ₁ , the provisional reference high potential is set in the middle of the right side and the left side of Formula 53 and set as Formula 1. .

The positive power supply voltage V _dd can be set to three times or more of the third high potential H ₃ as shown in the equation 54. Note that Formula 54 takes into account Formula 24.

Since the first high potential H ₁ is in the vicinity of the positive power supply voltage, Formula 55 is obtained from Formula 43 and Formula 42 even when V _dd is three times the smallest H ₃ .

即ち、Ｔ１とＴ５、Ｔ７にはほぼ均等なドレイン電圧が印加され、これらのトランジス
ターは飽和動作する。同様にＴ２、Ｔ６、Ｔ７にもほぼ均等なドレイン電圧が掛かり、飽
和動作する。Ｖ_ddが３倍よりも大きくなると、Ｔ１やＴ５、Ｔ７に掛かるソースドレイン
電圧は更に高くなるので、差動増幅範囲は更に広がる。

That is, substantially equal drain voltages are applied to T1, T5, and T7, and these transistors operate in saturation. Similarly, almost equal drain voltages are applied to T2, T6, and T7, and a saturation operation is performed. When V _dd is larger than three times, the source / drain voltages applied to T1, T5, and T7 are further increased, so that the differential amplification range is further expanded.

In summary, the potential relationship is such that the formula 54 related to V _dd , the formula 24 related to H ₃ , the formula 25 related to H ₂ , and the formula 1 related to H _r are satisfied. As an example, V _th = 1.5
As V, δ = 0.1V, γ = 1V, positive power supply potential V _dd = 4.8 V, third high potential H ₃ =
1.6 V, second high potential H ₂ = 7.3 V, and provisional reference high potential H _r = 4.05 V.

Regarding the transistor size, Formula 6 and Formula 34, Formula 36, Formula 38 to Formula 5 are used.
6.

この様な電気関係とトランジスターサイズとを採用する事で、高感度で正確な計測が実
現する。但し、Ｔ３とＴ４とは、実際には列選択トランジスターと行選択トランジスター
との直列接続なので、列選択トランジスターや行選択トランジスターのＺはＺ₃やＺ₄の二
倍とする。即ち、Ｔ３ＣやＴ３Ｒ、Ｔ４Ｃ、Ｔ４ＲのＺをそれぞれＺ_3C、Ｚ_3R、Ｚ_4C、Ｚ
_4Rにて表現した時に数式５７とする。

By adopting such electrical relationship and transistor size, highly sensitive and accurate measurement is realized. However, the T3 and T4, in fact because the series connection of the column selection transistor and a row select transistor, Z of the column selection transistor and row select transistors is twice the Z ₃ and Z _4. That is, Z of T3C, T3R, T4C, and T4R is changed to Z _3C , Z _3R , Z _4C , Z, respectively.
_When expressed in _4R , Formula 57 is obtained.

"Planar layout"
FIG. 8 is a diagram for explaining a planar layout of various circuits used in the temperature sensor according to the present embodiment, where (a) is an output circuit, (b) is a column selection transistor, and (c) is a measurement cell (i).
, J). Hereinafter, the planar layout of these circuits will be described with reference to FIG.

The method of manufacturing the thin film transistor will be described in detail later.
In addition, it has a gate wiring metal layer GM constituting the gate electrode and a source wiring metal layer SM mainly connected to the source / drain electrodes. An insulating film is provided between these three layers and is electrically separated unless connected by a contact hole. As shown in FIG. 8A, the current mirror pair T5 and T6 are formed adjacent to each other in plan view. That is, the semiconductor layer SL of T5
And the semiconductor layer SL of T6 are arranged next to each other. The two semiconductor layers are arranged as close as possible to each other as long as the design rule permits, without another semiconductor layer being located between them. Of course, the gate electrodes are common and are arranged at the shortest distance so that the gate electrode of T5 and the gate electrode of T6 are straight. The sources of both transistors are connected by a gate wiring metal layer GM and are connected to the drain of T7. Since the arrangement of T5 and T6 is close, the gate electrode is formed at the shortest distance, and the source contact is connected by the gate wiring metal layer GM, the temperatures of both transistors are substantially equal, and the current mirror pair operates accurately. It will be a thing.

Similarly, as shown in FIG. 8B, the column selection transistor pairs T3C and T4C are also arranged so that the semiconductor layers SL of both transistors are adjacent to each other and the gate electrodes are straight. As a result, the temperatures of the two transistors become substantially equal, and the amplification error caused by the column selection transistor pair can be minimized.

In the measurement cell, as shown in FIG. 8C, the differential transistor pair T1 and T2 are arranged adjacent to each other, and the drains of both transistors are connected to _Vdd by the gate wiring metal layer GM.
Thereby, the temperature of both transistors becomes substantially equal, and accurate differential amplification is performed. The row selection transistor pairs T3R and T4R are also arranged so that the semiconductor layers SL of both transistors are adjacent to each other and the gate electrodes are straight. As a result, the temperatures of both transistors are substantially equal, and the amplification error caused by the row selection transistor pair can be minimized.

"Manufacturing method of temperature sensor"
In the temperature sensor 1, a thin film circuit is formed on a flexible plastic film substrate 2. Here, a method for manufacturing the temperature sensor 1 will be described. Specifically, the temperature sensor 1 is manufactured by peeling the thin film circuit first formed on the glass substrate and transferring it to a plastic film.

As a 1st manufacturing process, a peeling layer is provided on the glass substrate used as a manufacturer board | substrate. The release layer is a hydrogenated amorphous silicon film having a thickness of about 50 nm. After forming a silicon oxide film serving as a base insulating film on the release layer, a thin film circuit including a thin film transistor is manufactured. For the thin film circuit, a known low temperature process polycrystalline silicon thin film transistor manufacturing method is applied. Specifically, a laser-crystallized polycrystalline silicon semiconductor layer is provided on the base insulating film, and then a gate insulating layer using a silicon oxide film and a metal obtained by adding an additive to aluminum or aluminum are used. A gate electrode (referred to as a gate wiring metal layer) is formed. Further, a first interlayer insulating layer using a silicon oxide film, a source contact and a drain contact (referred to as a source wiring metal layer) using aluminum or a metal obtained by adding an additive to aluminum, and a first resin using a polyimide resin. Two-layer insulating layer (protective film), indium tin oxide (ITO: Indium Tin
An electrode terminal (mounting terminal) using Oxide) is created.

Next, as a second manufacturing step, a temporary adhesive is applied to the surface of the thin film circuit, and the manufacturer substrate is attached to the temporary transfer substrate. As a temporary adhesive, what mixed polyvinyl pyrrolidone resin in order to give water solubility to acrylic resin is used. The temporary transfer substrate is a smooth glass substrate.

Next, as a third manufacturing process, the manufacturer substrate is removed, and the thin film circuit is transferred to the temporary transfer substrate. As a method of removing the manufacturer's substrate, laser light is irradiated from the back of the manufacturer's substrate to weaken the adhesive force inside or at the interface of the release layer, and then the manufacturer's substrate and the temporary transfer substrate are peeled off. By doing so, the thin film circuit is transferred to the temporary transfer substrate.

Next, as a fourth manufacturing process, the peeling layer remaining on the back surface of the thin film circuit is removed, and charges existing on the back surface of the thin film circuit are removed using, for example, an ionizer. In this way, it is possible to remove a certain amount of peeling electrification and frictional electrification with air during drying.

Next, as a fifth manufacturing process, for example, the back surface of the thin film circuit is attached to the first surface side of the plastic film using a permanent adhesive made of an acrylic resin. As the plastic film, a film having high heat resistance such as polyimide can be used.

After affixing the plastic film, as a sixth manufacturing process, the support substrate is bonded to the second side of the plastic film (the side opposite to the first side) using a temporary adhesive. This temporary adhesive is a material that easily loses its adhesiveness upon stimulation with heat, ultraviolet light, or the like, and is insoluble in a solvent that dissolves the temporary adhesive.

Next, as a seventh manufacturing process, the temporary transfer substrate is removed using a solvent (in this case, water) that dissolves the temporary adhesive. Thereafter, the temporary adhesive is washed away.

Next, as an eighth manufacturing process, a mounting operation is performed. First, tape wiring is mounted on the mounting terminals.
In this case, an anisotropic conductive paste or anisotropic conductive film is disposed between the mounting terminal and the tape wiring, and both are adhered. Thereafter, a stimulus such as heat or ultraviolet light is applied to the temporary adhesive to remove the support substrate. Finally, the tape wiring is an external controller 7 provided outside the temperature sensor 1
Connected to. Thus, the temperature sensor 1 is completed.

In addition to the plastic film described above, the substrate 2 has a thickness of 50 micrometers to 5 micrometers.
It may be a thin metal foil of about 00 micrometers or a thin glass of about 10 to 200 micrometers in thickness. Since these substrates have flexibility, they can be applied to any shape such as the skin of a robot. However, when the temperature sensor 1 is used for planar applications, the thickness is about 0.4 mm to 2 mm. Glass may be used as the substrate. Also, the manufacturing method is a method of thinly cutting the glass after forming a thin film circuit on the thick glass,
A method of directly forming a thin film circuit on a plastic film or metal foil may be used. In the case of direct formation, an amorphous silicon thin film transistor, an oxide thin film transistor using an oxide containing zinc or tin as a semiconductor layer, or the like can be used.

As described above, according to the temperature sensor 1 according to the present embodiment, the following effects can be obtained.
Since the control device 71 executes the setting step, the execution step, the determination step, and the resetting step, the second temperature measurement is different when the measured temperature is outside the measurement range of the first temperature measurement. It is possible to perform precise temperature measurement over a wide temperature range.
In other words, a high-performance and practical temperature measurement method can be provided.

In addition, since the second temperature measurement is intended to be performed at a temperature lower than that of the first temperature measurement, on average, accurate temperature measurement can be performed in a relatively short time.

In addition, the measurement cell includes a measurement thin film transistor and a capacitive element connected thereto, and a temperature measurement period in which temperature measurement is performed has a preparation period, a measurement period, and an output period. Can provide a simple temperature measurement method.

In addition, since the low potential based on the second condition is lower than the low potential based on the first condition, on average, accurate temperature measurement can be performed in a relatively short time.

In addition, since the determination step determines execution of the second temperature measurement when the initial potential and the first high potential are the same, high-precision temperature measurement can be performed in a short time if averaged. .

Further, since a plurality of measurement cells are arranged in the first direction and are individually selected, the temperature spatial distribution in the first direction can be measured. Therefore, even if the temperature differs along the first direction, the temperature can be accurately measured.

In addition, since a plurality of measurement cells are arranged in the second direction and are individually selected, the spatial distribution of the temperature in the second direction can be measured. Therefore, even if the temperature varies along the second direction, the temperature can be accurately measured.

Furthermore, since the measurement cell includes a differential transistor pair, the temperature can be measured with high accuracy even if the planar temperature sensor has a large area or high definition.

Further, since the third thin film transistor and the fourth thin film transistor function as a part of the selection circuit, it is possible to prevent the temperature information in the first direction and the second direction from interfering with each other.

Further, since the fifth thin film transistor and the sixth thin film transistor are provided and these form a current mirror pair and can be connected to the first thin film transistor and the second thin film transistor, the temperature can be accurately measured.

In addition, it has a first power supply, a second power supply, and a seventh thin film transistor, and since the seventh thin film transistor can be a constant current source, the temperature-related signal amplification is linear, and the gate potential of the first thin film transistor is accurately measured. it can.

In addition, since the fifth thin film transistor, the sixth thin film transistor, and the seventh thin film transistor are N-type and the second power source is a negative power source, a temperature sensor is used with an N-type thin film transistor without using a P-type thin film transistor. 1 can be realized.

The present invention is not limited to the above-described embodiment, and various changes and improvements can be added to the above-described embodiment. A modification will be described below.

(Modification 1)
"The circuit is formed by PMOS"
A temperature sensor according to the first modification will be described with reference to FIG. In addition, about the component same as Embodiment 1, the same number is attached | subjected and the overlapping description is abbreviate | omitted.
Compared with the first embodiment, this modification is different in the conductivity type of the thin film transistor that constitutes the circuit of the temperature sensor 1. Other configurations are almost the same as those of the first embodiment.

In the first embodiment, a circuit of the temperature sensor 1 (measurement circuit 3) using an N-type thin film transistor.
And the output circuit 4 and the column selection transistor of the second processing circuit 62). In this modification, these circuits are configured using P-type thin film transistors T1 to T7. In this case, the first power source is the negative power source V _ss and the second power source is the positive power source V _dd . The source and drain of the P-type thin film transistor is the source having the higher potential and the drain having the lower potential. As the P-type thin film transistor, poly (9,9-dioctylfluorene-cordithiophene) (F8T2), poly (3-hexylthiophene) (P3HT),
Poly [5,5′-bis (3-dodecyl-2tinyl) -2,2′-bithiophene] (PQT
-12) Organic thin film transistors using organic substances such as PBTTT and pentacene can be used.

The transistor size is the same as in the first embodiment. Although the driving method is the same as that in FIG. 4 of the first embodiment, the potential in the non-selection period is set to V _dd, and various high potentials H ₂ , H ₃ , and H _r in the selection period have negative absolute values larger than V _dd Change the way. Also, the low potential L becomes a value near V _dd ,
As L ₁ <L ₂ <L ₃ <L ₄ is repeated, the value of the low potential increases as the temperature measurement period is repeated. P
The threshold voltage V _thP of the thin film transistor is negative. Specifically, Formula 54 relating to V _dd
Is changed to Equation 58.

又、Ｈ₃に関する数式２４は数式５９へと変えられる。

Also, the equation 24 related to H ₃ is changed to the equation 59.

又、Ｈ₂に関する数式２５は数式６０へと変えられる。

In addition, Formula 25 relating to H ₂ is changed to Formula 60.

又、Ｈ_rに関する数式１は数式６１へと変えられる。

Also, Equation 1 relating to H _r is changed to Equation 61.

Therefore, for example, assuming that V _thP = −1.5 V, δ _P = −0.1 V, γ _P = −1 V, V _ss =
0 V, V _dd = 4.8 V, H ₃ = 3.2 V, H ₂ = −2.5 V, H _r = 0.75 V, L ₁ =
It is assumed that 4.8V, L ₂ = 7.3V, and L ₃ = 9.8V. If it is difficult to prepare a negative voltage like H ₂ here, V _dd and V _ss may be shifted by a certain amount so that all potentials become positive. For example, Formula 58 relating to V _dd is changed to Formula 62.

これに応じて、Ｖ_ssを数式６３へと変える。

In response to this, V _ss is changed to Equation 63.

上記例では全体が２．５Ｖずれて、Ｖ_dd＝７．３Ｖ、Ｖ_ss＝２．５Ｖ、Ｈ₃＝５．７Ｖ
、Ｈ₂＝０Ｖ、Ｈ_r＝３．２５Ｖ、Ｌ₁＝７．３Ｖ、Ｌ₂＝９．８Ｖ、Ｌ₃＝１２．３Ｖとな
る。

In the above example, the whole is shifted by 2.5 V, V _dd = 7.3 V, V _ss = 2.5 V, H ₃ = 5.7 V
H ₂ = 0V, H _r = 3.25V, L ₁ = 7.3V, L ₂ = 9.8V, and L ₃ = 12.3V.

As described above, according to the temperature sensor 1 according to this modification, the temperature sensor 1 can be realized with a P-type thin film transistor without using an N-type thin film transistor.

In the above example, the column selection transistors of the measurement circuit 3, the output circuit 4, and the second processing circuit 62 are all formed of P-type thin film transistors. However, in addition to this, some of these circuits are P-type. Other parts may be N-type. For example, the output circuit 4 may be formed of a P-type thin film transistor, and the measurement circuit 3 may be formed of an N-type thin film transistor. Further, a differential transistor pair (T1 and T2 pair), a row selection transistor pair (T3R and T4R pair),
If the thin film transistors paired inside each pair such as a column selection transistor pair (T3C and T4C pair) and a current mirror pair (T5 and T6 pair) are of the same conductivity type, a thin film is not formed between the pair. The conductivity type of the transistor may be different.

DESCRIPTION OF SYMBOLS 1 ... Temperature sensor, 2 ... Board | substrate, 3 ... Measuring circuit, 4 ... Output circuit, 7 ... External controller, 51 ... First selection circuit, 52 ... First processing circuit, 61 ... Second selection circuit, 62 ... Second processing Circuit, 71 ... control device, 72 ... cable.

Claims (14)

A temperature measurement method using a temperature sensor comprising a measurement thin film transistor and a capacitive element having one end connected to one of a source or a drain of the measurement thin film transistor,
A first step of charging the initial potential of the one end of the capacitive element to the measurement for TFT is turned on to,
A second step of changing the potential of the one end at the first off-current, with the first off-current flowing through the measurement thin film transistor ;
Performing a third step of detecting the potential of the one end as a first high potential ;
As a result of executing the first step, the second step, and the third step, if the first high potential is an appropriate potential within a range of less than 95% of the initial potential, the appropriate potential is set to Use to determine the temperature
When the first high potential is in the range of 95% or more and 100% or less of the initial potential as a result of executing the first step, the second step, and the third step,
The first step;
A fourth step of changing the potential of the one end with the second off-current, with the measurement thin film transistor in a state in which a second off-current greater than the first off-current flows .
A temperature measurement method comprising performing the third step. The state in which the first off current flows is obtained by supplying a first potential to the gate electrode of the measurement thin film transistor, and the state in which the second off current flows is a second potential in the gate electrode of the measurement thin film transistor. obtained by supplying, the temperature measuring method according to claim 1, characterized in that the lower of the second electric potential than the first potential.   The temperature measurement method according to claim 1, wherein the period of the fourth step is longer than the period of the second step. As a result of performing the first step, the fourth step, and the third step, the first high potential is a second appropriate potential that is in a range of less than 95% of the initial potential, Set the temperature using the second appropriate potential,
The first step, the fourth step, and the results of executing the third step, when the first high potential is 100% or less than 95% of the initial potential is further
The first step;
A fifth step of changing the potential of the one end with the third off-current, with the measurement thin film transistor in a state in which a third off-current larger than the second off-current flows .
The temperature measurement method according to any one of claims 1 to 3, wherein the third step is performed. 5. The state in which the third off-current flows is obtained by supplying a third potential to the gate electrode of the measurement thin film transistor, and the third potential is lower than the second potential. The temperature measurement method described in 1.   The temperature measurement method according to claim 4 or 5, wherein the period of the fifth step is longer than the period of the fourth step. The temperature sensor is disposed along a first direction, and includes a first selection circuit that selects the measurement cell,
The temperature measurement method according to claim 1, wherein a plurality of the measurement cells are arranged along the first direction. Furthermore, the temperature sensor includes a second selection circuit that is arranged along a second direction that intersects the first direction and that selects the measurement cell.
The temperature measurement method according to claim 7, wherein a plurality of the measurement cells are arranged along the second direction. The measurement cell further includes a first thin film transistor and a second thin film transistor,
The first thin film transistor and the second thin film transistor form a differential transistor pair,
The temperature measuring method according to claim 8 , wherein the gate electrode of the first thin film transistor is connected to one of a source electrode and a drain electrode of the thin film transistor. Further, the temperature sensor includes a third thin film transistor and a fourth thin film transistor,
The third thin film transistor is connected to the first thin film transistor;
The fourth thin film transistor is connected to the second thin film transistor;
The temperature measuring method according to claim 9, wherein the third thin film transistor and the fourth thin film transistor are controlled by the first selection circuit and the second selection circuit. Further, the temperature sensor includes a fifth thin film transistor and a sixth thin film transistor,
The fifth thin film transistor and the sixth thin film transistor form a current mirror pair,
The third thin film transistor is disposed between the first thin film transistor and the fifth thin film transistor;
The temperature measurement method according to claim 10, wherein the fourth thin film transistor is disposed between the second thin film transistor and the sixth thin film transistor. The temperature sensor further includes a first power source, a second power source, and a seventh thin film transistor,
The first thin film transistor and the second thin film transistor are connected to the first power source,
The fifth thin film transistor and the sixth thin film transistor are connected to the seventh thin film transistor;
The temperature measuring method according to claim 11, wherein the seventh thin film transistor is connected to the second power source. The fifth thin film transistor, the sixth thin film transistor, and the seventh thin film transistor are N-type,
The temperature measuring method according to claim 12, wherein the second power source is a negative power source. The fifth thin film transistor, the sixth thin film transistor, and the seventh thin film transistor are P-type,
The temperature measurement method according to claim 12, wherein the second power source is a positive power source.

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