JPH05129598A - Overheat detector for power device - Google Patents

Abstract

PURPOSE:To form a temperature detector in a simple structure by connecting a diode in series with a MOSFET, applying a reverse bias to the diode, and connecting the other end of the diode to the GND. CONSTITUTION:A diode 1 and a depression type MOSFET(MOSFET) 2 having a source, a drain and a gate 22 are connected in series. The diode 1 is connected to a buffer 5 in which an FET is used at a midpoint of the MOSFET 2. The buffer 5 has a predetermined threshold voltage. The reverse leakage current of the diode 1 is varied depending upon the square root of temperature, and increased as the temperature rises. When an intermediate voltage Vc of the MOSFET 2 exceeds the threshold value of the buffer 5, it is set to output a signal. Thus, the detection signal of an abnormal temperature can be output, and damage of a power IC can be prevented by controlling it by using the detection signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power device overheat detection circuit which is formed on a semiconductor substrate such as a control power IC and detects an abnormal temperature of a power device included in the power IC.

[0002]

2. Description of the Related Art In a control power IC, a control section and a power section are formed on one semiconductor chip, and it is necessary to prevent mutual interference between the control IC and the power stage. For that purpose, various methods of dielectric isolation separated by an insulating film, junction separation separated by a PN junction, and self-separation separated by a PN junction of each device controlled by a gate insulated from a substrate are used. is there. The former two are costly, so
It is desirable to be able to adopt the self-separation method.

Since the power device is used for high voltage and large current, when a large current exceeding the rated current flows due to, for example, a sudden increase in load or a short circuit, there is a risk that the power device will be thermally destroyed due to heat generation. Therefore, the temperature of the power device is constantly monitored, and if there is a temperature abnormality that exceeds a predetermined temperature, that is, if there is overheating, a protective operation such as disconnecting the load circuit is performed to prevent a thermal breakdown accident of the power device. Is required.

When the temperature of the power IC is to be monitored, it is necessary to build an overheat detection circuit including a temperature sensor on the same semiconductor substrate as the power IC in order to increase the temperature detection sensitivity and simplify the circuit structure. It goes without saying that it is advantageous. However, in the conventional overheat detection circuit formed in the power IC by the self-separation method, there is only an example in which a power source is connected to the substrate and the potential thereof is set to the maximum potential or the minimum potential, and the substrate serves as an output terminal like a power device. Things have not been announced.

[0005]

Such an overheat detecting circuit can be used for a high side type in which a power device for switching is connected between a load and a high potential power source, but the overheat detecting circuit is not connected to the load and the GND potential. It cannot be used for the low side type in which a power device for switching is connected.

An object of the present invention is that a detection circuit portion for detecting the temperature of a power device using a semiconductor substrate as an output terminal can be formed on the same substrate by a self-separation type with a simple structure, and the temperature dependence is used for detection. An object is to provide an overheat detection circuit for a power device that can extract a large signal in the temperature range.

[0007]

In order to achieve the above-mentioned object, the present invention is a circuit formed on a semiconductor substrate common to a power device to detect overheating of the power device, which uses a depletion type MOSFET. The constant current power source, the reverse biased one side to a low potential, the other side to the PN junction connected to the constant current power source, and the potential at the intermediate point between the constant current power source and the PN junction has reached a predetermined value. And a determination circuit that determines and issues a signal.

Further, the present invention is a circuit for detecting overheating of a power device formed on a common substrate with the power device, each of which is a constant current power source using a depletion type MOSFET, and is reverse biased and one side is connected to a low potential. Then, it is determined that the substrate temperature has reached a predetermined detection temperature because the potential of the PN junction whose other side is connected to the constant current power source and the intermediate point between the constant current power source and the PN junction has reached a predetermined value. A detection circuit with a high detection temperature and a second detection circuit with a low detection temperature, and a signal when the substrate temperature rises and exceeds the detection temperature of the first detection circuit. A hysteresis circuit that outputs the signal and then outputs the signal by connecting the signal until the substrate temperature drops and becomes equal to or lower than the detected temperature of the second detected temperature.

When a constant current power source using a depletion type MOSFET cannot be used, a resistor or enhancement type MOSF connected to a high potential is used instead of the constant current power source using a depletion type MOSFET.
It is also possible to use ET.

In any case, it is effective that the layer on the low impurity concentration side of the reverse biased PN junction has an impurity concentration of 5 × 10 ¹³ / cm ² or more.

[0011]

The reverse leakage current of the PN junction formed on the same semiconductor substrate as the power device increases as the substrate temperature rises. This increase in reverse leakage current can be converted into an electric signal with a large change by changing it to a voltage by using the static characteristics of depletion type MOSFETs connected in series, and this voltage signal can be judged by a judgment circuit to determine the overheat temperature range. If the control signal for shutting off the power device or the like is issued when the temperature reaches, it is possible to prevent a thermal destruction accident of the power IC.

Then, since the overheat is detected by using the potential of the intermediate point of the PN junction formed on the same semiconductor substrate as the power device and having one side at the GND potential and the depletion type MOSFET connected in series to the PN junction, the substrate is powered. It becomes possible to make it the output terminal of the device.

Further, if two sets of the overheat detection circuits having the above-mentioned constructions, which have different detection temperatures from each other, and the hysteresis circuit are combined so as to provide a predetermined temperature range between the transmission and the stop of the notification signal, the load can be reduced. Power I due to fluctuations
Since it is possible to prevent the notification signal from being repeatedly output with respect to a short-time temperature change that occurs in C, it is possible to eliminate the inconvenience of erroneously recognizing the temperature change due to the load change as an overheated state and cutting off the load. A reliable overheat detection can be performed.

Further, in order to convert the reverse leakage current into voltage, instead of the depletion type MOSFET, a resistor or enhancement type MOSFE connected to a high potential is used.
You may use T.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an overheat detection circuit according to an embodiment of the present invention.
Fig. 2 shows a semiconductor device to be formed and is a power device.
It is formed on the same semiconductor substrate as the MOSFET shown in
It The semiconductor substrate is n⁺Substrate 11 and formed on it
n^-The epitaxial layer 12^-On layer 12
p⁺Diffusion layer 13, p^-Diffusion layer 14, n^-Diffusion layer 15, n
⁺Diffusion layers 16, 17, 18, 19 are formed, n^-Layer 1
N of 2⁺Insulating film 2 on the surface sandwiched by layers 17 and 18
Through the gate electrode 22, p^-N of layer 14 ⁺Layer 19 and
n^-The insulating film 23 is formed on the surface sandwiched between the exposed portions of the layer 12.
The gate electrode 24 is formed of a polycrystalline silicon layer through
ing.

Insulating films 25, 26, 27, 28, 2 as a protective film for the junction and an interlayer insulating film exposed on the surface of the substrate.
Electrodes 31 and n ⁺ layers 16 and 1 which are formed to contact the p ⁺ layer 13 and the p ⁺ layer 13 and the p ⁻ layer 14 in common through the contact holes and are connected to the GND terminal.
7 and the gate electrode 22, and the electrode 32 connected to the V _C terminal and the electrode 33 connected to the n ⁺ layer 18 and connected to the V _DD terminal are both made of metal. On the back surface side of the substrate, which is also made of metal, the drain electrode 34 connected to the output terminal V _D , which is an output electrode, is in contact with the n ⁺ layer 11.

The MOSFET shown in FIG.
When a positive voltage is applied to the pole 34, the gate electrode 2
When a positive voltage above the threshold is applied to 4, p^-Layer 14
N ⁺Layers 19 and n^-The part sandwiched between the exposed part of layer 12
Is inverted and an n-channel is generated, so that the electrode 31
Source region 19, n channel, n^-Layer 12, n⁺Layer 1
The electrons flow to the drain electrode 34 via 1
Pass through. And it was 100-200V or more when off
Output terminal V_DPotential becomes close to GND.

FIG. 3 is a circuit diagram composed of the elements shown in FIG. 1, and the portions corresponding to the respective portions in FIG. 1 are designated by the same reference numerals. Source p ⁺ layer 13 and n ⁺ more becomes a layer 16 diode 1 and the n ⁺ layer 17 in FIG. 1, n ⁺ layer 18
Is connected in series with the depletion type MOSFET 2 having a gate electrode 22 as a drain. The intermediate point between the diode 1 and the MOSFET 2 is connected to the buffer 5 using an FET or the like.

Next, referring to FIG. 4, the overheat detecting operation will be described. The line 40 in FIG. 4 is the current value of the MOSFET 2 when the midpoint potential V _C is changed, and this value is the MOS value.
It depends on the shape of the FET 2, the concentration of the n ⁻ layer 15, and the like. Line 4
1, 42, 43, 44, 45 and 46 are reverse leakage currents of the diode 1, which are values when the temperature is increased from T ₁ to T ₆ . As can be seen from the figure, the leakage current changes depending on the square root √T of the temperature T, and increases as the temperature rises. When the temperature is low, for example, at 15 ℃, the reverse leakage current is 50 ×.
Those of 10 ⁻¹⁵ A increase to 200 nA at 175 ° C., for example. This current value also changes depending on the PN junction area. Potential of V _C is determined by the intersection of line 40 and line 41 to 46, but when the temperatures T ₁ is V _1, when the temperature T ₅ is changed to V _5. Therefore, a constant threshold voltage V _th
By using the buffer 5 having the above and outputting a signal when V _C becomes equal to or lower than V _th , an abnormal temperature detection signal can be output. If this signal is changed to a control signal and is input to the gate electrode 24 of the MOSFET of the power device shown in FIG. 2 through a logic circuit that determines the priority order with respect to the drive signal and the current is controlled, the power IC is destroyed. Can be prevented.

As described above, the MOSFET is turned on and off.
Output terminal V_DThe potential of changes, but
An error occurs in the detected temperature. That is, MOSFET
Low detection temperature when output potential is close to GND after turning on
Tend to show. This is n ⁺Layer 16, p⁺Layers 13, n
^-Due to the current amplification of the parasitic transistor formed in layer 12,
It is considered to be one.

FIG. 5 shows the results of measuring the detection temperature error by changing the impurity concentration of the p ⁺ layer 13. It can be seen that the error is suppressed by increasing the concentration of the p ⁺ layer 13 and suppressing the h _FE of the parasitic transistor. Although depending on the design of the control circuit, a practical overheat detection circuit could be formed by setting the concentration of the p ⁺ layer 13 to 5 × 10 ¹³ / cm ² or more.

FIG. 6 is a circuit diagram showing an overheat detecting circuit according to the second embodiment of the present invention. In this case, the first detection circuit 61 in which the diode 1 and the depletion type MOSFET 2 are connected in series, and the diode 3 and the depletion type MOSFET formed on the same semiconductor substrate as the first detection circuit 61.
T2 and the second detection circuit 62 connected in series. Then, it receives the output of the inverter 51 that inverts and outputs the output of the buffer 5 connected to the first detection circuit 61 and the output of the buffer 5 connected to the second detection circuit 62, and outputs the combined output V _X. It is provided with a pair of NAND circuits 52 and 53 that are output and feedback-coupled to each other. For example, by setting the PN junction area of the diode 1 in this overheat detection circuit smaller than the PN junction area of the diode 3, the detection temperature at which V _C of the first and second detection circuits becomes V _th or less can be changed. ..

For example, if the junction area of the diode 1 is
If 1/4 to 1/5 of the joint area of the card 3 is used, the first detection
The detection temperature of the circuit 61 is 180 ° C, the detection temperature of the second detection circuit
The temperature is 155 ° C. As a result, the temperature of the semiconductor substrate
Output V above 180 ° C _XBecomes L → H, and becomes 1 again
Even if the temperature falls below 80 ° C, the substrate temperature remains unchanged from 155 ° C.
Output V from H to L for the first time when the degree decreases_XChanges. This
Even if there is a detection error of 20 ° C, the output V_XOf
Stable control can be performed without any change in return.
It

FIG. 7 shows the case the power device is a insulated gate bipolar transistor (IGBT), but this case is p ⁺ substrate 10 is used instead of the n ⁺ substrate 11 of FIG. 1, the p ⁺ layer 13 It can be seen that the diode formed of the n ⁻ layer 12 and the MOSFET formed of the n ⁻ layer 15, the n ⁺ layers 17 and 18 and the gate electrode 22 can be formed in the same manner as in FIG. Further, it goes without saying that any of the present invention can be applied to a p-channel insulated gate power device in which the conductivity type is reversed. In that case, GND becomes the highest potential.

In any of the above embodiments,
It is possible to replace the depletion type MOSFET with a resistor or an enhancement type MOSFET. In this case, the n ⁻ layer, the n ⁺ layer, and the polycrystalline silicon layer can be used for the resistor. In addition, enhancement type MOSF
The gate of ET is connected to V _DD . However, if a resistance or enhancement type MOSFET is used,
It should be noted that when the potential of the high potential V _DD terminal changes, the detected temperature also changes slightly.

FIG. 8 shows a circuit of an embodiment in which a resistor 120 is used instead of the depletion type MOSFET, and FIG.
Shows the circuit of the embodiment when the enhancement type MOSFET 220 is used. Enhancement type MOSFE
When T220 is used, the gate electrode 22 is preferably connected to V _DD by the wiring 33.

10 and 11 are sectional views of a main portion corresponding to the embodiment using the resistor 120 of FIG. 8. FIG. 10 shows a case where a diffused resistance layer 121 is used for the resistor 120, and FIG. In this case, the polycrystalline silicon resistance layer 122 using the same polycrystalline silicon layer as that used for the gate electrode 22 of the depletion type MOSFET 2 is used. In any case, the manufacturing process can be carried out by the same process as that of the embodiment shown in FIG.

FIG. 12 shows a depletion type MOSFET.
FIG. 10 is a cross-sectional view of a main portion corresponding to the example of the circuit in FIG. 9 when an enhancement type MOSFET 220 is used instead of 2. The difference from FIG. 1 is that the n ⁻ diffusion layer 15 is unnecessary and the gate electrode 22 is connected to V _DD by the wiring 33. In the example of using the resistance or enhancement type MOSFET described in the above embodiment, as compared with the example of using the depletion type MOSFET described above, for example, in FIG. 10, a large number of layers for forming the gate electrode 22 in FIG. 1 is formed. Since the process of depositing the crystalline silicon layer is unnecessary and the process of forming the n ⁻ diffusion layer in FIG. 1 is not necessary in FIGS. 11 and 12, there is an advantage in cost reduction, but the voltage of V _DD is If it fluctuates, there is a demerit that the heating detection temperature slightly changes, so it is necessary to use it properly depending on the application.

[0029]

According to the present invention, a diode formed on the same semiconductor substrate as a power device and a depletion type MOSFET as a constant current power source are connected in series, a reverse bias is applied to the diode, and the P side of the PN junction of the diode or By connecting the N side to the minimum or maximum potential of GND, the diode and MO
An abnormality in the substrate temperature can be detected by utilizing the potential change at the intermediate point of the SFET, and an overheat detection circuit for a power device in a self-isolated power IC applicable to the low side type can be obtained. Further, by connecting the outputs of the pair of detection circuits to the flip-flop, it was possible to obtain a stable overheat detection circuit that performs a hysteresis operation between two detection temperatures.

By setting the impurity concentration of the layer on the low impurity concentration side of the diode to 5 × 10 ¹³ / cm ² or more, the error in the detected temperature when the power device is turned on can be suppressed.

Also, when a resistor or an enhancement type MOSFET is used instead of the depletion type MOSFET, almost the same result as the above is obtained, but there is a demerit that the detection temperature slightly changes due to the change of the power supply potential. ..

[Brief description of drawings]

FIG. 1 is a sectional view of an element constituting an overheat detection circuit according to an embodiment of the present invention.

2 is a cross-sectional view of a MOSFET protected by the circuit of FIG.

FIG. 3 is a circuit diagram of an overheat detection circuit according to an embodiment of the present invention.

FIG. 4 is a potential and MOSFET showing the operation of the embodiment of FIG.
Diagram of the current of the diode and the reverse leakage current of the diode

FIG. 5 is a diagram showing the relationship between the concentration of the p ⁺ layer forming the diode and the detected temperature error.

FIG. 6 is a circuit diagram of another embodiment of the present invention.

FIG. 7 is a cross-sectional view of an element that constitutes an overheat detection circuit that protects an IGBT according to another embodiment of the present invention.

FIG. 8 is a circuit diagram of an overheat detection circuit according to another embodiment of the present invention.

FIG. 9 is a circuit diagram of an overheat detection circuit according to still another embodiment of the present invention.

FIG. 10 is a sectional view of elements constituting an overheat detection circuit according to another embodiment of the present invention.

FIG. 11 is a cross-sectional view of elements constituting an overheat detection circuit according to another embodiment of the present invention.

FIG. 12 is a cross-sectional view of elements constituting an overheat detection circuit according to still another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 diode 2 depletion type MOSFET 3 diode 5 buffer 61 first detection circuit 62 second detection circuit 63 hysteresis circuit V _C midpoint potential 120 resistance 220 enhancement type MOSFET

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location // H01L 23/58 7220-4M H01L 23/56 D

Claims (9)

[Claims] 1. A circuit formed on a semiconductor substrate common to a power device to detect overheating of the power device, the circuit comprising:
Constant current power supply using depletion type MOSFET,
A signal is issued by determining that the potential of the reverse biased one side has a low potential, the other side has been connected to the constant current power source, and the potential at the intermediate point between the constant current power source and the PN junction has reached a predetermined value. An overheat detection circuit for a power device, comprising: a determination circuit. 2. A circuit which is formed on a semiconductor substrate common to a power device and detects overheating of the power device,
A constant current power source using depletion type MOSFETs, a reverse biased one side is connected to a low potential, and the other side is connected to the constant current power source and a PN junction and a potential at an intermediate point between the constant current power source and the PN junction is predetermined. The first detection circuit having a high detection temperature and the second detection circuit having a low detection temperature, which has a determination circuit that determines that the substrate temperature has reached a predetermined temperature when the temperature reaches a predetermined value and issues a signal, and the substrate temperature. A signal is output when the temperature rises and exceeds the detection temperature of the first detection circuit, and then the signal is connected and output until the substrate temperature decreases and becomes equal to or lower than the detection temperature of the second detection temperature. An overheat detection circuit for a power device, comprising: a circuit. 3. The circuit according to claim 1 or 2,
The layer on the low impurity concentration side of the reverse biased PN junction is 5 ×
An overheat detecting circuit for a power device having an impurity concentration of 10 ¹³ / cm ² or more. 4. A circuit which is formed on a semiconductor substrate common to a power device and detects overheating of the power device,
Judge that the resistance connected to a high potential, the reverse biased one side to a low potential, the other side connected to the resistance, and the potential at the midpoint between the resistance and the PN junction have reached a predetermined value. And a decision circuit for issuing a signal, and an overheat detection circuit for a power device. 5. A circuit which is formed on a semiconductor substrate common to a power device and detects overheating of the power device,
A resistor connected to a high potential, respectively, and a reverse biased PN with one side connected to a low potential and the other side connected to the resistor
The first detection with a high detection temperature, which has a determination circuit that issues a signal by determining that the substrate temperature has reached a predetermined temperature when the potential of the junction and the intermediate point between its resistance and the PN junction has reached a predetermined value. Circuit and a second detection circuit with a low detection temperature, outputs a signal when the substrate temperature rises and exceeds the detection temperature of the first detection circuit, and then the substrate temperature falls and the second detection temperature An overheat detection circuit for a power device, comprising: a hysteresis circuit that connects and outputs the signal until the temperature becomes equal to or lower than a detection temperature. 6. The circuit according to claim 4 or 5,
The layer on the low impurity concentration side of the reverse biased PN junction is 5 ×
An overheat detecting circuit for a power device having an impurity concentration of 10 ¹³ / cm ² or more. 7. A circuit which is formed on a semiconductor substrate common to a power device and detects overheating of the power device,
Enhancement type MOSFET connected to high potential
Then, it is judged that the reverse biased one side has a low potential, the other side has the PN junction connected to the enhancement type MOS, and the potential at the intermediate point between the enhancement type MOS and the PN junction has reached a predetermined value. And an overheat detection circuit for a power device, comprising: 8. A circuit formed on a semiconductor substrate common to a power device to detect overheating of the power device, the circuit comprising:
Enhancement type MOS connected to high potential
FET, reverse biased P connected to one side at low potential and the other side connected to the enhancement MOSFET
A first detection circuit having a high detection temperature, which has a judgment circuit for judging that the substrate temperature has reached a predetermined temperature when the potential at the intermediate point between the N junction and its resistance and the PN junction has reached a predetermined value A detection circuit and a second detection circuit with a low detection temperature, and outputs a signal when the substrate temperature rises and exceeds the detection temperature of the first detection circuit, and then the substrate temperature falls and the second detection temperature And a hysteresis circuit for connecting and outputting the signal until the detected temperature becomes equal to or lower than the detection temperature. 9. The circuit according to claim 7 or 8,
The layer on the low impurity concentration side of the reverse biased PN junction is 5 ×
An overheat detecting circuit for a power device having an impurity concentration of 10 ¹³ / cm ² or more.