JP4915421B2 - Capacitive humidity detector - Google Patents

Description

  The present invention relates to a capacitive humidity detecting device that detects humidity.

  Conventionally, as disclosed in, for example, Patent Document 1, a sensor unit (humidity sensor) whose capacitance changes in accordance with a change in physical quantity (for example, humidity) and a circuit unit (signal processing unit) including a CMOS transistor or the like are semiconductors. A capacitive physical quantity detection device (capacitive humidity detection device) formed on a substrate has been proposed. As described above, in the capacitive humidity detection device disclosed in Patent Document 1, since the humidity sensor and the signal processing unit are formed on the same semiconductor substrate, the humidity sensor and the signal processing unit are formed on different semiconductor substrates. Compared with the capacity-type humidity detection apparatus made, it is a capacity-type humidity detection apparatus in which the increase in physique is suppressed.

JP 2006-58084 A

  By the way, as described above, in Patent Document 1, the humidity sensor and the signal processing unit are formed on the same semiconductor substrate. Therefore, there is a possibility that heat generated in the signal processing unit by continuous driving is transmitted to the humidity sensor through the semiconductor substrate, and the humidity sensor generates heat. When the humidity sensor generates heat, the moisture in the moisture-sensitive film that absorbs moisture in the humidity sensor evaporates, which may change the dielectric constant of the moisture-sensitive film and reduce the detection accuracy of the humidity sensor.

  In view of the above problems, an object of the present invention is to provide a capacitive humidity detection device in which an increase in physique is suppressed and a decrease in detection accuracy of a humidity sensor is suppressed.

In order to achieve the above-described object, the invention described in claim 1 includes a humidity sensor whose capacity changes in accordance with a change in humidity, a CV conversion unit that converts the capacity change of the humidity sensor into a voltage, A signal processing unit that processes an output signal of the CV conversion unit is a capacitive humidity detection device formed on the same semiconductor substrate, which converts a power supply voltage into a first pulse signal, and the first pulse by inputting the signal to the signal processing unit, it has a intermittent drive unit intermittently drives the signal processing unit, at least one temperature sensor being formed on a semiconductor substrate, the intermittent drive unit, the output signal of the temperature sensor Based on the above, the pulse period of the first pulse signal is adjusted .

As described above, according to the present invention, the humidity sensor and the signal processing unit are formed on the same semiconductor substrate. Therefore, compared to a capacitive humidity detecting device in which the humidity sensor and the signal processing unit are formed on different semiconductor substrates, the capacitive humidity detecting device is suppressed from increasing in size. Moreover, it has the intermittent drive part which intermittently drives the signal processing part. Therefore, heat generation of the signal processing unit due to continuous drive is suppressed, and the capacitive humidity detection device is also suppressed in which a decrease in detection accuracy of the humidity sensor due to this heat generation is suppressed. Further, since the intermittent drive unit adjusts the pulse period of the first pulse signal based on the output signal of the temperature sensor, the drive state of the signal processing unit is adjusted according to the temperature of the semiconductor substrate, and thus the signal processing The temperature of the part (temperature of the humidity sensor) can be adjusted. That is, heat generation of the signal processing unit can be more effectively suppressed, and a decrease in detection accuracy of the humidity sensor can be more effectively suppressed.

According to a second aspect of the present invention, it is preferable that the temperature sensor has a first temperature sensor formed in a formation region of the signal processing unit in the semiconductor substrate. Thereby, the pulse period of the first pulse signal can be adjusted based on the temperature of the signal processing unit that is a heat source.

According to a third aspect of the present invention, it is preferable that the temperature sensor has a second temperature sensor formed in a portion immediately below the formation region of the humidity sensor in the semiconductor substrate. Thereby, the pulse period of the first pulse signal can be adjusted based on the temperature of the humidity sensor affected by the heat of the signal processing unit.

According to a fourth aspect of the present invention, the temperature sensor preferably includes a third temperature sensor formed in a separation region separated from the formation region of the signal processing unit and the formation region of the humidity sensor in the semiconductor substrate.

  According to this, the pulse period of the first pulse signal is adjusted based on the ambient temperature of the semiconductor substrate (hereinafter simply referred to as ambient temperature) and the temperature of the signal processing unit, or the ambient temperature and the temperature of the humidity sensor. be able to. That is, the driving state of the signal processing unit can be adjusted according to the heat generation of the signal processing unit or the humidity sensor.

According to the fifth aspect of the present invention, the signal processing unit, the humidity sensor, and the third temperature sensor are thermally connected between the signal processing unit formation region, the humidity sensor formation region, and the separation region in the semiconductor substrate. A structure in which a trench that separates into two is formed is preferable. Thereby, it can suppress that the heat | fever of the signal processing part which is a heat generating source is transmitted to a 3rd temperature sensor via a semiconductor substrate. Further, it is possible to suppress the heat of the humidity sensor affected by the heat source from being transmitted to the third temperature sensor via the semiconductor substrate. Therefore, the detection accuracy of the ambient temperature in the third temperature sensor can be improved.

According to the sixth aspect of the present invention , the external electrode formed on the semiconductor substrate is connected to an ambient temperature sensor that measures the ambient temperature of the semiconductor substrate, and the intermittent drive unit includes the temperature sensor and the ambient temperature sensor. A configuration in which the pulse period of the first pulse signal is adjusted based on the output signal is preferable. According to this, the effect similar to the effect of Claim 5 can be acquired.

As described in claim 7 , a configuration having a sample-and-hold unit that makes the output signal of the signal processing unit constant is preferable. According to this, the synchronization circuit for synchronizing the cycle of the output signal output from the capacitive humidity detection device and the sampling cycle of a circuit (for example, ECU) provided at the subsequent stage of the capacitive humidity detection device, The circuit configuration is not necessarily provided, and the circuit configuration can be simplified.

As a specific configuration of such a sample and hold unit, as described in claim 8 , the sample and hold unit is connected to a voltage follower circuit having an amplification factor of 1, and one end connected to an output terminal of the signal processing unit. The other end is connected to the input terminal of the voltage follower circuit, the other end is connected to the wiring connecting the output terminal of the switch section and the input terminal of the voltage follower circuit, and the other end is connected to the ground. was adopted possess a capacitor for temporarily holding the output signal of the switch unit, and the switch unit, the signal processing unit and the voltage follower earth circuit, and a configuration in which connection between the signal processing unit and the capacitor is controlled can do. According to a ninth aspect of the present invention, the sample-and-hold unit includes an AD conversion unit that converts an output signal of the signal processing unit from an analog signal to a digital signal, one end of which is connected to the output terminal of the signal processing unit. It is also possible to adopt a configuration having a DA conversion unit that converts one output signal of the AD conversion unit from a digital signal to an analog signal, one end of which is connected to the other end of the AD conversion unit.

As described in claim 10, the pulse period is the same as the pulse period of the first pulse signal, the rise timing of the pulse is slower than the rise timing of the first pulse signal, the falling timing of the pulse, the It is preferable that the generator has a generating unit that generates a second pulse signal that is earlier than the falling timing of the one pulse signal, and the switch unit is controlled to be opened and closed by the second pulse signal. According to this, in a state in which the switch unit is closed (a state in which the signal processing unit and the capacitor are connected), an output signal having a voltage level of Low level is input from the signal processing unit to the capacitor and is thereby accumulated in the capacitor. It is possible to suppress fluctuations in the electric charge (detection voltage proportional to the electric capacity detected by the humidity sensor). That is, a decrease in detection accuracy of the humidity sensor can be suppressed.

It is a block diagram showing a schematic structure of a capacity type humidity detecting device concerning a 1st embodiment. It is a top view which shows schematic structure of a semiconductor substrate. It is sectional drawing which follows the III-III line of FIG. It is a timing chart figure of the capacity type humidity detecting device at the time of normal operation. It is a timing chart figure of a capacity type humidity detecting device when a signal processing part is generating heat. It is a wave form diagram for explaining the rise timing and fall timing of the output signal of a generating part. It is sectional drawing which shows the modification of an active element and a temperature sensor. It is sectional drawing which shows the modification of a temperature sensor. It is sectional drawing for demonstrating the connection of an ambient temperature sensor and a semiconductor substrate. It is sectional drawing for demonstrating a trench. It is a block diagram which shows the modification of a sample hold part. It is a block diagram which shows schematic structure of a sample hold part.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a block diagram illustrating a schematic configuration of a capacitive humidity detection apparatus according to the first embodiment. FIG. 2 is a plan view showing a schematic configuration of the semiconductor substrate. 3 is a cross-sectional view taken along line III-III in FIG. FIG. 4 is a timing chart of the capacitive humidity detecting device during normal operation. FIG. 5 is a timing chart of the capacitive humidity detection device when the signal processing unit is generating heat. FIG. 6 is a waveform diagram for explaining the rising timing and falling timing of the output signal of the generation unit. In FIG. 1, the output signal S ₁ of the control unit 32 constituting the intermittent drive unit 30 described later, the output signal S ₂ of the first switch 31, and the output signal S ₃ of the signal processing unit 23 constituting the circuit unit 20. indicates respectively dashed arrows show the output signal S ₄ of the generator 60 by a chain line arrow. Further, in FIGS. 4 and 5, in order to avoid the complication, are omitted output signal S _1.

First, the outline of the output signals S _{1 to} S ₅ shown in FIG. 1 will be described with reference to FIG. The output signals S _{1 to} S ₃ are pulse signals having a pulse period of T and a pulse width of L ₁ . The output signal S _4, the pulse period is T, the pulse width is narrower L ₂ than L _1, slower than the rise timing of the pulse output signal S _2, S _3, pulse falling timing the output signal of the It is a pulse signal earlier than S ₂ and S ₃ . The output signal S ₅ is a constant amplitude signal. The maximum value of the output signal _{S 2} and the output signal _{S 4} of the respective amplitudes (High-level voltage level of, or the pulse amplitude) is equal to the voltage _{V 0} which power source 80, the output signal _{S 3} and the output signal _{S 5} for each amplitude Is equal to the voltage V ₁ proportional to the electric capacity detected by the humidity sensor 10. The maximum value of the output signals S ₁ amplitude may be any value that can be controlled to open and close the first switch 31 is not particularly limited. Incidentally, the output signal S _2, corresponds to a first pulse signal according to the appended claims, the output signal S ₄ corresponds to a second pulse signal according to the appended claims.

Hereinafter, a schematic configuration of the capacitive humidity detection apparatus 100 will be described with reference to FIG. The capacitive humidity detection apparatus 100 includes, as main parts, a humidity sensor 10 whose capacity changes in accordance with a change in humidity, a circuit unit 20 that processes an output signal of the humidity sensor 10, and a signal that constitutes the circuit unit 20 And an intermittent drive unit 30 that intermittently drives the processing unit 23. Furthermore, in the present embodiment, the temperature sensor 40 (first temperature sensor 41, third temperature sensor 42), the comparison unit 50 that compares the output signals of the temperature sensor 40, and the pulse period are the output signals S ₂ and S ₃ . equally, slower than the rise timing of the pulse output signal _S 2, _{S 3,} a generating unit 60 which fall timing to generate an early output signal _{S 4} output than the output signal _S 2, _{S 3,} the output signal _{S 3} And a sample hold unit 70 that keeps the constant. The humidity sensor 10, the CV conversion unit 22 constituting the circuit unit 20, and the control unit 32 constituting the intermittent drive unit 30 use the voltage V _{0 of the} power supply 80 as the drive voltage, and the signal processing unit 23 serves as the intermittent drive unit. 30 the output signal _{S 2} (first switch 31) has a driving voltage.

  As shown in FIGS. 2 and 3, the humidity sensor 10 and the circuit unit 20 are formed on a semiconductor substrate 90. The semiconductor substrate 90 according to this embodiment is made of single crystal silicon, and a silicon oxide film 91 is formed on the surface.

  The humidity sensor 10 includes a pair of comb-like detection electrodes 11 formed on the surface of the semiconductor substrate 90, and a pair of combs different from the detection electrode 11 in the length of the comb teeth, the number of comb teeth, and the like. A tooth-like reference electrode 12, a protective film 13 that protects these electrodes 11 and 12, and a moisture sensitive film 14 that absorbs and desorbs moisture around the semiconductor substrate 90 are provided. The moisture sensitive film 14 is formed on the detection electrode 11 and the reference electrode 12 in the protective film 13. The capacitance of each capacitor constituted by the detection electrode 11 and the reference electrode 12 is configured to change according to the amount of moisture because the dielectric constant of each capacitor changes according to the amount of moisture absorbed by the moisture sensitive film 14. ing. However, as described above, since the detection electrode 11 and the reference electrode 12 are different in configuration, the change in capacitance with respect to the change in the amount of moisture absorbed in the moisture sensitive film 14 is also different. Therefore, a change in the amount of moisture (humidity) can be detected by comparing the change in the capacitance of the reference electrode 12 with the change in the capacitance of the detection electrode 11. The output signal of the humidity sensor 10 is output from the external electrode 15 to the outside via the circuit unit 20 and the sample hold unit 70. The configuration for detecting humidity is not limited to the above example. For example, the comb-shaped detection electrode 11, the reference electrode 12 having the same configuration as the detection electrode 11, and the electrodes 11 and 12 are protected. A configuration including the protective film 13 and the moisture sensitive film 14 formed on the detection electrode 11 in the protective film 13 can be employed. In this case, the capacity of the reference electrode 12 is not changed according to the amount of water because the moisture sensitive film 14 is not provided. Therefore, a change in the amount of moisture (humidity) can be detected by comparing the reference capacitance with the capacitance of the detection electrode 11 using the capacitance of the reference electrode 12 as a reference capacitance.

  The circuit unit 20 processes the output signal of the humidity sensor 10, and is formed by integrating tens of thousands to hundreds of thousands of active elements such as the MOS transistor 21. The circuit unit 20 includes a CV conversion unit 22 that converts a capacitance into a voltage, and a signal processing unit 23 that processes an output signal of the CV conversion unit 22. The CV conversion unit 22 converts the difference between the charge proportional to the capacitance of the detection electrode 11 and the charge proportional to the capacitance of the reference electrode 12 into a voltage and outputs the voltage. The signal processing unit 23 amplifies the output signal of the CV conversion unit 22 and corrects the temperature of the output signal of the CV conversion unit 22 based on the temperature measured by the temperature sensor 40. In addition, since the specific structure of the CV conversion part 22 is explained in detail in Japanese Patent Application Laid-Open No. 2006-58084, description thereof is omitted in the present embodiment. In FIG. 1, the current path between the temperature sensor 40 and the signal processing unit 23 is omitted in order to avoid complication.

The intermittent drive unit 30 drives the signal processing unit 23 intermittently. The intermittent drive unit 30 according to the present embodiment includes a first switch 31 that controls connection between the power source 80 and the signal processing unit 23, and a control unit 32 that controls the open / closed state of the first switch 31. The first switch 31 is an N-channel MOS transistor, the drain side terminal is connected to the power supply 80, the source side terminal is connected to the signal processing unit 23 and the generation unit 60, and the gate electrode is connected to the control unit 32. Has been. To the gate electrode, the pulse period is T, the output signals S ₁ of the control unit 32 pulse width is L ₁ is input, the source and the drain of the first switch 31, at intervals of pulse period T connected, it is connected between the pulse width L _1. That is, the power supply 80 and the signal processing unit 23, and a power source 80 and the generator 60 are connected at intervals of the pulse period T, is connected between the pulse width L _1. As a result, the first switch 31 outputs the output signal S ₂ whose maximum amplitude is the voltage V ₀ of the power supply 80, the pulse period is T, and the pulse width is L ₁ , and the output signal S ₂ is The signal is input to the signal processing unit 23 and the generation unit 60. As described above, the signal processing unit 23, since the output signal S ₂ is set to the driving voltage, the signal processing unit 23 is driven at intervals of the pulse period T, so that the drive between the pulse width L _1. Thereby, the output signal of the CV conversion unit 22 is amplified from the signal processing unit 23 and the temperature is corrected, and the maximum value of the amplitude is the voltage V ₁ proportional to the electric capacity detected by the humidity sensor 10. , the pulse period is T, the output signal S ₃ the pulse width is L ₁ is outputted.

  The temperature sensor 40 measures the temperature of the semiconductor substrate 90. As shown in FIG. 3, the temperature sensor 40 according to this embodiment includes a first temperature sensor 41 formed in the formation region of the signal processing unit 23 in the semiconductor substrate 90 and the formation of the signal processing unit 23 in the semiconductor substrate 90. And a third temperature sensor 42 formed in the separation region separated from the region and the formation region of the humidity sensor 10. The temperature sensors 41 and 42 according to the present embodiment measure the temperature based on the temperature characteristics of the forward voltage generated when a current flows in the forward direction in the PN junction. As described above, since the semiconductor substrate 90 is made of silicon, the forward voltage of the temperature sensors 41 and 42 has a temperature characteristic that decreases by 2.5 mV each time the temperature increases by 1 ° C. . Since such a temperature sensor 40 can be built in the semiconductor substrate 90 together with the circuit unit 20, the manufacturing process is simplified compared to a configuration in which a temperature sensor is provided in addition to the semiconductor substrate 90. Yes. The temperature sensor 40 is not limited to the one based on the temperature characteristics of the forward voltage of the PN junction described above, and for example, a thermistor can be employed.

The comparison unit 50 compares the output signals of the plurality of temperature sensors 40. The comparison unit 50 according to the present embodiment is formed by a differential amplifier circuit, the output signal U ₁ of the first temperature sensor _41, which is the difference between the output signal U ₃ of the third temperature sensor 42, U ₁ -U An output signal obtained by amplifying ₃ is input to the control unit 32 of the intermittent drive unit 30. Control unit _32, U 1 -U ₃ ≦ 0 by setting the pulse period T to a predetermined value _{T 1} in the case _of, U 1 _-U 3> 0 long _{T 2} than the predetermined value _{T 1} of the pulse period T in the case of It is set to. That is, when the temperature of the signal processing unit 23 is equal to or lower than the ambient temperature, the driving time of the signal processing unit 23 is set to a predetermined time, and the temperature of the signal processing unit 23 is higher than the ambient temperature (the signal processing unit 23 generates heat). In this case, the driving time of the signal processing unit 23 is made shorter than a predetermined time. In Figure 4, shows the output signal S ₂ to S ₄ in case the signal processing section 23 is below ambient temperature, in Figure 5, shows the output signal S ₂ to S ₄ at the time when the signal processing unit 23 generates heat Yes. That is, FIG. 4, a pulse period indicates the output signal _S 2 to S ₄ of the _{T 1,} FIG. 5, the pulse period indicates the output signal _S 2 to S ₄ of _{T 2.} As shown in FIGS. 4 and 5, it can be seen that the pulse period T ₂ is longer than the predetermined value T _1.

Based on the output signal S ₂ , the generation unit 60 has a pulse period of T, a pulse width of L ₂ that is narrower than L ₁ , and a pulse rising timing that is later than that of the output signals S ₂ and S _3. Generates and outputs a pulse signal whose falling timing is earlier than that of the output signals S ₂ and S ₃ . As shown in FIGS. 4 to 6, the output signal _{S 4,} when the voltage level of the output signal _S 2, _{S 3} is High level, the voltage level of the output signal _{S 4} is always a High level. Thus, the second switch 72 constituting the sample-and-hold unit 70 only when (when the voltage level of the output signal S ₄ is High level) in the closed state, the voltage level of the output signal S ₃ is High level The signal V ₁ is input to a voltage follower circuit 71 and a capacitor 73 that constitute the sample hold unit 70.

The sample hold unit 70 makes the output signal of the signal processing unit 23 constant. As shown in FIG. 1, the sample hold unit 70 according to this embodiment includes a voltage follower circuit 71 having an amplification factor of 1, and a second switch 72 that controls connection between the signal processing unit 23 and the voltage follower circuit 71. And a capacitor 73 that temporarily holds the output signal of the second switch 72. The second switch 72 is an N-channel MOS transistor, the drain side terminal is connected to the output terminal of the signal processing unit 23, the source side terminal is the non-inverting input terminal of the voltage follower circuit 71, and the capacitor 73. One end is connected, and the gate electrode is connected to the generation unit 60. To the gate electrode, the output signal S ₄ of the generator 60 is input, the signal processing unit 23 and the voltage follower Ah circuit 71, and a signal processing unit 23 and the capacitor 73 are connected at intervals of the pulse period T, It is connected between the pulse width L _2. As described above, only when the second switch 72 is in the closed state, the signal V ₁ having the high voltage level of the output signal S ₃ is input to the voltage follower circuit 71 and the capacitor 73. The signal V ₁ is always input to the subsequent stage side of the terminal on the source side of the second switch 72 in the hold unit 70. Even when the second switch 72 is in an open state, the signal V ₁ is temporarily held by the capacitor 73, so that the voltage at the subsequent stage of the source side terminal of the second switch 72 is always kept at V ₁ . It has come to droop. As described above, since the amplification degree of the voltage follower circuit 71 is 1, the input voltage and the output voltage of the voltage follower circuit 71 are equal. As a result, an output signal S ₅ having a constant value V ₁ is output from the output terminal of the voltage follower circuit 71.

  Next, the effect of the capacitive humidity detection apparatus 100 according to the present embodiment will be described. As described above, the humidity sensor 10 and the circuit unit 20 formed by the MOS transistor 21 are formed on the same semiconductor substrate 90. Therefore, the capacitive humidity detection device 100 is a capacitive humidity detection device in which the increase in the physique is suppressed as compared with the capacitive humidity detection device in which the humidity sensor and the circuit unit are formed on different semiconductor substrates. . Moreover, it has the intermittent drive part 30 which drives the signal processing part 23 intermittently. Therefore, heat generation of the signal processing unit 23 due to continuous drive is suppressed, and the capacitive humidity detection device is also suppressed in which a decrease in detection accuracy of the humidity sensor 10 due to this heat generation is suppressed.

  The capacitive humidity detection apparatus 100 according to the present embodiment includes a temperature sensor 40 and a comparison unit 50 that compares output signals of the temperature sensor 40, and the control unit 32 outputs an output signal of the comparison unit 50. Based on the above, the pulse period T is set. Accordingly, the driving state of the signal processing unit 23 can be adjusted according to the temperature of the semiconductor substrate 90, and consequently the temperature of the signal processing unit 23 (the temperature of the humidity sensor 10) can be adjusted. That is, heat generation of the signal processing unit 23 can be suppressed, and a decrease in detection accuracy of the humidity sensor 10 can be suppressed.

Further, in the present embodiment, the control unit 32, pulse when the output signal _{U 1} of the first temperature sensor 41, _U 1 -U ₃ is less than or equal to 0 which is the difference between the output signal _{U 3} of the third temperature sensor 42 set period T to a predetermined value _{T 1,} it is set to a long _{T 2} than the predetermined value _{T 1} of the pulse period T if U 1 -U ₃ is greater than 0. That is, when the temperature of the signal processing unit 23 is equal to or lower than the ambient temperature, the driving time of the signal processing unit 23 is set to a predetermined time, and the temperature of the signal processing unit 23 is higher than the ambient temperature (the signal processing unit 23 generates heat). In this case, the driving time of the signal processing unit 23 is made shorter than a predetermined time. Thereby, the heat generation of the signal processing unit 23 is suppressed.

In the present embodiment, the output signal S ₃ of the signal processing unit 23 is made constant, and the sample hold unit 70 that outputs the output signal S ₅ whose signal value is a constant value V ₁ is provided. According to this, the synchronization circuit for synchronizing the cycle of the output signal output from the capacitive humidity detection device 100 and the sampling cycle of a circuit (for example, ECU) provided in the subsequent stage of the capacitive humidity detection device 100 is provided. It is not necessary to provide the circuit described above, and the configuration of the circuit can be simplified.

In the present embodiment, based on the output signal S ₂ , the pulse period is T, the pulse width is L ₂ narrower than L ₁ , the rising timing of the pulse is later than the output signals S ₂ and S ₃ , and the pulse fall timing generates a fast output signal S ₄ than the output signal S _2, S _3, and a generator 60 for outputting a. Thus, the second switch 72 constituting the sample-and-hold unit 70 only when (when the voltage level of the output signal S ₄ is High level) in the closed state, the voltage level of the output signal S ₃ is High level The signal V ₁ is input to a voltage follower circuit 71 and a capacitor 73 that constitute the sample hold unit 70. Thus, in a state where the second switch 72 is closed, the voltage level in the output signal S ₃ from the signal processing section 23 is Low level signal is input to the capacitor 73, thereby the electric charge accumulated in the capacitor 73 (the humidity sensor 10 Fluctuation of the voltage V ₁ ) proportional to the electric capacity detected in step ₁ can be suppressed. That is, a decrease in detection accuracy of the humidity sensor 10 can be suppressed.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  In the present embodiment, an example in which the circuit unit 20 is formed by the MOS transistor 21 is shown. However, the active element forming the circuit unit 20 is not limited to the MOS transistor 21. For example, as shown in FIG. 7, a CMOS transistor 24 may be employed. In addition, for example, a bipolar transistor or IGBT can be employed.

In the present embodiment, the temperature sensor 40 is separated from the first temperature sensor 41 formed in the formation region of the signal processing unit 23 in the semiconductor substrate 90, the formation region of the signal processing unit 23, and the formation region of the humidity sensor 10. The example which has the 3rd temperature sensor 42 formed in the separated area | region which was made was shown. However, as shown in FIG. 7, the temperature sensor 40 includes a second temperature sensor 43 formed in a portion of the semiconductor substrate 90 immediately below a region where the humidity sensor 10 is formed, and the third temperature sensor 42 described above. Can also be adopted. In this case, the comparison unit 50, the output signal _{U 2} of the second temperature sensor 43, which is the difference between the output signal _{U 3} of the third temperature sensor _42, an output signal obtained by amplifying the U 2 -U _3, the intermittent drive unit 30 To the control unit 32. Control unit _32, U 2 -U ₃ ≦ 0 by setting the pulse period T to a predetermined value _{T 1} in the case _of, U 2 _-U 3> 0 long _{T 2} than the predetermined value _{T 1} of the pulse period T in the case of Set to. That is, when the temperature of the humidity sensor 10 is equal to or lower than the ambient temperature, the driving time of the signal processing unit 23 is set to a predetermined time, and the temperature of the humidity sensor 10 is higher than the ambient temperature (the signal processing unit 23 generates heat). ), The driving time of the signal processing unit 23 is made shorter than a predetermined time. FIG. 7 is a cross-sectional view showing a modification of the active element and the temperature sensor.

As shown in FIG. 8, the temperature sensor 40 may include a first temperature sensor 41 and a second temperature sensor 43. In this case, the comparison unit 50 inputs an output signal obtained by amplifying U ₁ −U ₂ , which is a difference between the output signal U ₁ and the output signal U ₂ , to the control unit 32 of the intermittent drive unit 30. Control unit _32, U 1 -U ₂ ≦ 0 by setting the pulse period T to a predetermined value _{T 1} in the case _of, U 1 _-U 2> 0 long _{T 2} than the predetermined value _{T 1} of the pulse period T in the case of Set to. FIG. 8 is a cross-sectional view showing a modification of the temperature sensor.

As shown in FIG. 9, as the configuration for measuring the ambient temperature, a configuration in which the ambient temperature sensor 44 for measuring the ambient temperature is connected to the external electrode 15 can be adopted. Thereby, since the signal processing unit 23 and the ambient temperature sensor 44 that are heat sources are thermally separated, the ambient temperature in which the influence of the heat of the signal processing unit 23 is suppressed can be measured. . In this case, the control unit 32 determines the pulse period T based on the difference between the output signal U ₁ and the output signal U ₄ of the ambient temperature sensor 44. FIG. 9 is a cross-sectional view for explaining the connection between the ambient temperature sensor and the semiconductor substrate 90.

9 shows an example in which the temperature sensor 40 includes the first temperature sensor 41, but a configuration including the second temperature sensor 43 instead of the first temperature sensor 41 may be employed. In this case, the control unit 32, based on the difference of the output signals U ₂ and the output signal U _4, to determine the pulse period T.

  As a configuration for measuring the ambient temperature in which the influence of heat of the signal processing unit 23 that is a heat source is suppressed, as shown in FIG. 10, the formation region of the signal processing unit 23 and the humidity sensor 10 in the semiconductor substrate 90, A configuration in which a trench 92 is provided between the isolation region and the isolation region may be employed. Accordingly, it is possible to suppress the heat of the signal processing unit 23 that is a heat generation source from being transmitted to the third temperature sensor 42 via the semiconductor substrate 90. Further, the heat of the humidity sensor 10 affected by the heat source can be prevented from being transmitted to the third temperature sensor 42 through the semiconductor substrate 90. Thereby, the ambient temperature in which the influence of the heat of the signal processing unit 23 is suppressed can be measured. FIG. 10 is a cross-sectional view for explaining a trench.

  In the present embodiment, an example in which the first switch 31 and the second switch 72 are N-channel MOS transistors has been described. However, the configuration of the switch that is closed by the input of a signal having a high voltage level is not limited to the above example. For example, a switch having an N-channel MOS transistor, a P-channel MOS transistor, and an inverting circuit that inverts the signal level can be employed. In this switch, a signal is directly input to the gate electrode of the N-channel MOS transistor, a signal is input to the gate electrode of the P-channel MOS transistor via an inverting circuit, the sources are connected to each other, and the drains are connected to each other. They are connected to each other. Thereby, the N-channel MOS transistor and the P-channel MOS transistor are simultaneously closed by the input of a signal having a high voltage level, and the source and the drain are connected.

  When the N-channel MOS transistor is in a closed state, the on-resistance, which is the resistance between the source and drain, increases, whereas the on-resistance of the P-channel MOS transistor decreases. Therefore, when the switch is composed of only an N-channel MOS transistor, the ON resistance corresponding to the resistance of the switch continues to rise in a state where a signal having a high voltage level is input. When the modified example is adopted, the resistance of the switch is determined by the on-resistance of the N-channel MOS transistor and the on-resistance of the P-channel MOS transistor, so that the change of the switch resistance due to the signal input to the gate electrode Can be suppressed.

In the present embodiment, the sample and hold unit 70 includes a voltage follower circuit 71 having an amplification factor of 1, a second switch 72 that controls connection between the signal processing unit 23 and the voltage follower circuit 71, and the second switch 72 An example having a capacitor 73 that temporarily holds an output signal is shown. However, as shown in FIG. 11, the sample-and-hold unit 70 for a constant output signal S ₃ of the signal processing section 23, A-D converting the output signal S ₃ of the signal processing unit 23 into a digital signal from an analog signal A configuration having a conversion unit 74 and a D / A conversion unit 75 that converts the output signal of the A / D conversion unit 74 from a digital signal to an analog signal may be employed. FIG. 11 is a block diagram showing a modification of the sample hold unit.

Hereinafter, the driving of the sample and hold unit 70 will be described with reference to FIG. 12, taking the case where the A-D conversion unit 74 and the D-A conversion unit 75 have 4 bits as an example. The DA converter 75 includes four switches 76a to 76d that control connection between the power supply 80 and the output terminal, four resistors 77a to 77d provided in a power supply wiring 81 that connects the power supply 80 and ground, And four resistors 78a to 78d provided on the wiring connecting the power supply wiring 81 and the source side terminals of the switches 76a to 76d. The switches 76a to 76d are N-channel MOS transistors, the source-side terminal is connected to the power supply wiring 81, the drain-side terminal is connected to the output terminal, and the gate electrode is connected to the AD converter 74. Yes. The resistors 77a to 77d are provided between the intersection of the drain side terminal of the switches 76a to 76d and the power supply wiring 81, and between the intersection of the source side terminal of the switch 76d and the power supply wiring 81 and the ground. It has been. The gate electrode of each switch 76a-76d, is determined based on the signal of the output signal _{S 3,} the output signal of the A-D conversion unit 74, for example, [0010] is inputted, the four switches 76a-76d Among them, only the switch 76c is closed, and the power source 80 and the output terminal are connected via the resistors 77a, 77b, and 78c. Then, the voltage level of the signal output from the switch 76c is uniquely determined, and a signal having the determined voltage level is output from the AD conversion unit 74. As a result, an output signal having a constant signal value is output from the output terminal of the sample hold unit 70. Incidentally, as the amplitude of the outputted signal becomes equal to the voltages _{V 1} proportional to the capacitance detected by the humidity sensor 10, the output signal of the A-D converter unit 74, resistors 77a to 77d, and the resistor 78a~78d The resistance value is adjusted. FIG. 12 is a block diagram showing a schematic configuration of the sample hold unit.

Note that the A-D conversion unit 74 and the D-A conversion unit 75 described above are preferably formed without using capacitors. When the capacitor is included, the charge accumulated in the capacitor (voltage V ₁ proportional to the electric capacity detected by the humidity sensor 10) may fluctuate due to charge leakage of the capacitor. Therefore, by forming the A / D conversion unit 74 and the D / A conversion unit 75 without using a capacitor, it is possible to suppress the occurrence of the above-described problems.

DESCRIPTION OF SYMBOLS 10 ... Humidity sensor 20 ... Circuit part 22 ... CV conversion part 23 ... Signal processing part 30 ... Intermittent drive part 40 ... Temperature sensor 50 ... Comparison part 60 ... Generation unit 70 Sample hold unit 80 Power source 90 Semiconductor substrate 100 Capacitance humidity detector

Claims (10)

A humidity sensor whose capacity changes in response to changes in humidity;
A CV conversion unit that converts a capacitance change of the humidity sensor into a voltage;
A signal processing unit that processes the output signal of the CV conversion unit, and a capacitive humidity detection device formed on the same semiconductor substrate,
The power supply voltage into a first pulse signal and inputting the first pulse signal to the signal processing unit, have a intermittent drive unit intermittently drives the signal processing unit,
At least one temperature sensor is formed on the semiconductor substrate;
The said intermittent drive part adjusts the pulse period of a said 1st pulse signal based on the output signal of the said temperature sensor, The capacitive humidity detection apparatus characterized by the above-mentioned . Before SL temperature sensors, capacitive humidity detector according to claim 1, characterized in that to have a first temperature sensor which is formed on said signal processing unit forming region where definitive in the semiconductor substrate. 3. The capacitive humidity detecting device according to claim 1, wherein the temperature sensor includes a second temperature sensor formed in a portion of the semiconductor substrate immediately below the formation region of the humidity sensor . 4. The said temperature sensor has the 3rd temperature sensor formed in the separation area separated from the formation area of the signal processing part and the formation area of the humidity sensor in the said semiconductor substrate, The Claim 2 or Claim 3 characterized by the above-mentioned. Capacitance type humidity detection device as described. Before Symbol semiconductor substrate, wherein a formation region of the formation region of the signal processing unit and the humidity sensor, wherein between the separating region, the signal processing unit and said humidity sensor and said third temperature sensor thermally capacitive humidity detector according to claim 4, characterized in Rukoto trench isolation is formed. An ambient temperature sensor for measuring the ambient temperature of the semiconductor substrate is connected to the external electrode formed on the semiconductor substrate,
The intermittent drive unit, wherein the temperature sensor based on the output signal of the ambient temperature sensor, capacitance type according to claim 2 or claim 3, characterized that you adjust the pulse period of the first pulse signal Humidity detection device. Capacitive humidity detector according to any one of claims 1 to 6, wherein Rukoto that have a sample-and-hold unit for a constant output signal of the signal processing unit. The sample hold unit
A voltage follower circuit with an amplification factor of 1,
One end is connected to the output terminal of the signal processing unit, the other end is connected to the non-inverting input terminal of the voltage follower circuit,
One end is connected to the wiring connecting the output terminal of the switch unit and the input terminal of the voltage follower circuit, the other end is connected to the ground, a capacitor for temporarily holding the output signal of the switch unit, I have a,
8. The capacitive humidity detection device according to claim 7 , wherein the switch unit controls connection between the signal processing unit and the voltage follower circuit, and between the signal processing unit and the capacitor . The sample hold unit
An AD converter that converts an output signal of the signal processor from an analog signal to a digital signal, one end of which is connected to an output terminal of the signal processor;
One end is connected to the other end of the A-D converter unit, according to claim 8, further comprising, a D-A converter for converting the analog signal from the digital signal an output signal of the A-D converter unit Capacitive humidity detector. The pulse period is the same as the pulse period of the first pulse signal, the pulse rising timing is later than the rising timing of the first pulse signal, and the pulse falling timing is the falling edge of the first pulse signal. A generator that generates a second pulse signal that is earlier than the timing;
The switch unit, capacitive humidity detector according to claim 8, characterized in Rukoto controlled to open and close by the second pulse signal.

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