JPH0936356A - Application of bipolar semiconductor element comprising temperature detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect temperature by forming a temperature detecting section consisting of a pn-junction type diode on a semiconductor substrate of a bipolar semiconductor element having a control electrode and measuring a forward voltage of a diode when the control signal is on or off. SOLUTION: Temperature is detected by making use of temperature dependence of the forward voltage VF of a diode when the gate is off. The voltage across the electrode C of collector 9 and electrode E of emitter 8 is set to zero and the voltage of gate electrode 7 is also set to zero. Under this condition, a constatnt current is applied from a current source 18 to measure a voltage across the anode electrode 15 and cathode electrode 16. Or, under the condition that the on signal is applied to the gate electrode 7, a constant current is applied from a low current source 18 to measure the voltage across the anode electrode 15 and cathode electrode 16. The forward voltage of diode obtained is plotted on the vertical axis and temperature on the horizontal axis to draw the temperature dependence curve of the forward voltage. Thereby, accurate temperature may be detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a minority carrier injection type semiconductor device equipped with a temperature detector used in an inverter device or the like.

[0002]

2. Description of the Related Art Minority carrier injection type so-called bipolar semiconductor devices (IGBTs, bipolar transistors, etc.)
Are used for inverters and the like, and recently, IGBTs have been replaced by bipolar transistors and the market has been expanding. The IGBT has been mainly developed with an emphasis on total loss and improvement of characteristics in the safe operation area, but in recent years, demands for higher functionality and easier handling have been increasing. In order to meet these various demands, there is a limit in the IGBT alone, and we are trying to respond by making intelligent power devices such as IGBTs. Intelligentization is to integrate power devices and their peripheral circuits to enhance their functions while compensating for their weaknesses. For example, IPM (Intelligent Power Module) has emerged as one of its first Device.

[0003] With the advent of the IPM, the field of application in which conventional thyristors and bipolar transistors have been used has been increased.
GBT became rapidly penetrating. If an IGBT is used in an inverter, etc.
There is a mode in which an overcurrent is applied, and in addition to protection of these by the power device alone, there is an example in which overheating is detected through an external circuit as IPM technology to enable protection.

FIG. 5 shows a timing chart at the time of overheat operation of the IPM including the IGBT. The horizontal axis is time. For detecting overheating, for example, a thermistor is attached to the lower arm case in the IPM module, and the temperature characteristics of the thermistor are used. From time T1 (1)
When the gate signal of (4) is given, the output current of (4) is output. Then, the temperature rises due to the switching loss and the steady loss of the IGBT, and the case temperature of (3) gradually rises. When the case temperature reaches the set level L1 (time T2), the protection circuit of (2) operates, the gate signal of (1) is stopped, the output current of (4) is stopped, and the protection operation against heating is performed. It will be. When the case temperature of (3) decreases and reaches the set level L2 (time T3), the protection circuit of (2) is released, and the gate signal of (1) is applied again from time T4, and (4) The output current of is output. (5) is an output of, for example, an alarm signal that works in synchronization with the protection circuit of (2).

As a sensor for detecting overheating, a diode can be used in addition to a thermistor. The example of the temperature dependency of the forward voltage at a current with a diode (V _F) shown in FIG. The horizontal axis is temperature, and the vertical axis is forward voltage.
V _F is the higher the temperature, and has a small value. This V _F
The temperature can be detected from the value of. However, temperature detection is usually performed in the vicinity of a power device mounted on a substrate, and is not detecting the temperature of the junction of the semiconductor element, so that the temperature of the semiconductor element may rise rapidly. There is no protection against abnormal modes. This is a major problem for reliability. When temperature detection of a semiconductor element is performed, it is desirable that the temperature detection target semiconductor element and the temperature detection unit are as close as possible. Ideally, the temperature detector is formed on the semiconductor element itself.

FIG. 8 is a partial cross-sectional view of an insulated gate bipolar transistor (hereinafter abbreviated as IGBT) as an example of a semiconductor device in which a temperature detecting unit is added to the semiconductor device itself. The left part of the figure is an active region that performs switching operation for conducting and blocking the main current of the IGBT. Shown in the figure is a unit part including one control electrode (hereinafter called cell).
And the active region consists of a large number of such cells. Further, a withstand voltage structure such as a guard ring structure or a field plate structure is provided at a peripheral portion of the IGBT, but is not shown in the drawing.

In the figure, p base region 4 is selectively formed in the surface layer of n base layer 3 laminated on p substrate 1 with n ⁺ buffer layer 2 interposed therebetween. An n emitter region 5 is selectively formed in the p base region 4, and polysilicon is formed on the surface of the p base region 4 sandwiched between the n base layer 3 and the n emitter region 5 via a gate oxide film 6. And a gate electrode 7 connected to the G terminal.
A collector electrode 9 connected to the C terminal is provided on the back surface of the p substrate 1, and an n emitter region 5 is provided on the n emitter region 5.
And an emitter electrode 8 which is in common contact with the p base region 4 and is connected to the E terminal. This IGBT
Is a gate oxide film 6, a gate electrode 7, a p base region 4,
A MOSFET composed of an n emitter region 5, an n base layer 3 and an n ⁺ buffer layer 2 and a pnp transistor composed of a p-type substrate 1, an n ⁺ buffer region 2, an n base layer 3 and ap base region 4. It can also be seen as consisting of.

The n base layer 3 of such an IGBT is formed, for example, of a p substrate 1 and an n ⁺ buffer layer 2 laminated thereon.
Is formed by epitaxial growth on a substrate consisting of Further, p base region 4 is formed by introducing impurities using the gate electrode 7 formed earlier as a mask, and n emitter region 5 is formed by introducing impurities using a photoresist (not shown) as a mask. As shown in the figure, the emitter electrode 8 may be extended on the gate electrode 7 via an insulating film.

The switching operation of this IGBT is performed as follows. By applying a voltage equal to or higher than a threshold value to the gate electrode 7 in a state where a positive voltage is applied to the C terminal with respect to the E terminal, the p base region 4 immediately below the gate electrode 7 is applied.
An inversion layer (channel region 12) is formed on the surface of the MOSFET and the MOSFET becomes conductive. Electrons are injected from the n emitter region 5 into the n base layer 3 and the n ⁺ buffer layer 2 through the inversion layer. Since the junction between p substrate 1 and n ⁺ buffer layer 2 is forward biased, electrons flow into p substrate 1 through this junction. Then, a pnp transistor having the p-substrate 1, the n ⁺ buffer layer 2, the n-base layer 3, and the p-base region 4 as an emitter, a base, and a collector respectively operates, and conductivity modulation occurs to turn on the IGBT. This I
When the GBT is turned off, by removing the voltage of the gate electrode 7, the inversion layer formed on the surface of the p base region 4 immediately below the gate electrode 7 disappears, and the injection of electrons from the n emitter region 5 is stopped. Turn off.

On the right side of FIG. 8, a temperature detecting diode 17 is provided as a temperature detecting section. That is, n
A p anode region 13 is selectively formed on the surface layer of the base layer 3, and an n cathode region 14 is formed on the surface layer. p
An anode electrode 15 and a cathode electrode 16 are provided in the anode region 13 and the n cathode region 14, respectively.
The anode electrode 15 is connected to the current source 18 and the cathode electrode 16 is connected to the emitter electrode 8 of the IGBT section.

[0011]

However, as shown in FIG. 8, due to the forward voltage of the temperature detecting diode, the IGBT is
When I performed the heating protection operation of,
It operated at low temperature and showed extremely unstable operation. In the IGBT shown in FIG. 8, the IGBT shown in FIG. 9 was prototyped in consideration of interference between the IGBT section and the temperature detecting diode 17. That is, in the IGBT of FIG. 9, the IGBT of FIG.
In addition to T, p-type regions 23 and 24 for extracting holes are provided in the central portion of the figure, that is, between the IGBT portion and the temperature detecting diode 17. p-type region 23,
The emitter electrode 8 is in contact with the surface of 24. However, even in the IGBT shown in FIG. 9, the heating protection operation by the diode for temperature detection is still unstable.

The cause was investigated. The forward current-voltage curve of the temperature detecting diode 17 is shown in FIG. 7A and 7B are forward current-voltage curves of the temperature detecting diode 17, where FIG. 7A shows the case where the gate is on when a voltage Vg is applied to the gate, and FIG. 7B shows the case where the gate voltage is zero and the gate is off. In this way, it was found that two curves differ depending on the presence or absence of the gate signal. When the gate is on, the forward voltage is lower than when the gate is off.

In view of the above problems, an object of the present invention is to provide a semiconductor substrate of a bipolar semiconductor device having a control electrode with p
An object of the present invention is to provide a method of use for performing a stable protection operation of a temperature detecting section built-in bipolar semiconductor element in which a temperature detecting section made of an n-junction diode is formed.

[0014]

In order to solve the above-mentioned problems, the present invention forms a temperature detecting portion composed of a pn junction type diode on a semiconductor substrate of a bipolar semiconductor element having a control electrode, and the forward direction of the diode is formed. In the method of using the temperature detection part built-in bipolar semiconductor device that detects temperature from the temperature dependence of voltage, when the control signal is on, or
When the control signal is off, the forward voltage of the diode shall be measured to detect the temperature.

The forward voltage is measured within a range in which the forward voltage when the control signal is on and that when the control signal is off are measured,
It is also possible to detect the temperature. It is also possible to detect the temperature based on the difference in the forward voltage of the diode when the control signal is on and when the control signal is off. By detecting the temperature with pulse generation means and pulse-like voltage measurement means,
It is also possible to detect the temperature when a voltage is applied to the bipolar semiconductor element.

The above means have the following effects. If the forward voltage of the diode is measured separately when the control signal is on or when the control signal is off, there is no confusion between the two states and accurate temperature detection is possible. If the forward voltage of the diode is measured within a range in which the forward voltage when the control signal is on and that when the control signal is off are matched, there is no confusion between the two states and accurate temperature detection is possible.

If the temperature is detected by the difference in the forward voltage of the diode when the control signal is on and when the control signal is off,
Easy to judge. If the temperature is detected when the voltage is applied to the bipolar semiconductor element by detecting the temperature by the pulse generating means and the pulse-like measuring means, no extra time is required for the temperature detection.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION In order to perform a stable protection operation of a bipolar semiconductor device with a built-in temperature detector, the method of the present invention comprises:
The temperature is detected from either the forward voltage of the diode in the ON state of the bipolar semiconductor element or the forward voltage of the diode in the OFF state, or within the range where the two coincide, or from the difference between the two.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. Figure 1 shows the temperature dependence of the forward voltage (V _F) in the forward current with a temperature sensing diode 17 of FIG. 9 (e.g. 200 .mu.A). The horizontal axis represents temperature and the vertical axis represents forward voltage of the diode. As shown in FIG. 7, two temperature dependence curves can be seen depending on the presence / absence of the control signal, that is, the gate-on case and the gate-off case. The mechanism by which the forward current-voltage curve is divided depending on the presence or absence of the control signal will be described below.

Here, a constant current of 200 μA is applied to the current source 18 of the temperature sensing diode 17 to drive it. When the gate is on, 15V is applied to the gate electrode 7 with respect to the emitter electrode 8, and when the gate is off, the voltage of the gate electrode 7 is 0V. When 15 V is applied to the gate electrode 7 of the IGBT portion, a channel region 12 is formed in the surface layer of the p base region 4 directly below the gate electrode 7, and the n emitter region 5 and the n base layer 3 are connected. When a current is supplied from the current source 18 in this state, a hole current flows from the p anode region 13 to the n cathode region 14, and conversely, electrons flow from the n cathode region 14 to the p anode region 13. But,
At this time, since the cathode electrode 15 in contact with the n cathode region 14 is connected to the emitter electrode 8 of the main IGBT portion, the p electrode between the p anode region 13 and the n base layer 3 is p.
Similarly, the n-junction is also in the forward bias state, and the n-base layer 3
Hole current flows in. Further, electrons are supplied from the n emitter region 5 to the n base layer 3. This current is applied to the p anode region 13, the n base layer 3 and the p base region 4, p
The base current of the pnp transistor formed of the extraction regions 23 and 24 becomes the base current of the pnp transistor, and the p base region 4 and the p extraction regions 23 and 24 are turned on.
Flow into. That is, when the gate is turned on, in addition to the temperature sense diode 17 including the p anode region 13 and the n cathode region 14, the lateral IGBT including the n emitter region 5, the p base region 2, the n base layer 3, and the p anode region 13 is turned on. As a result, current also flows through the extraction regions 23 and 24. Furthermore, when the gate is on (V _G = 15 V), a large number of carriers are generated in the n base layer 3, and the Coulomb force of the carriers causes the latter pnp transistor to easily flow a current. Therefore, when the gate is on, the forward voltage V _F of the temperature sense diode 17 becomes small.

On the other hand, when the gate is off (V _G = 0V), since the gate is off, the channel region 12 is not formed in the surface layer of the p base region 4 immediately below the gate electrode 7, so that the n emitter region is formed. 5 and the n base layer 3 are not connected, and no current flows from the p anode region 13 to the n base layer 3. Therefore, the current flowing from the p anode region 13 is
Only the n-cathode region 14 can flow, and the forward voltage V _F becomes higher than when the gate is on. However, even when the gate is off, when it reaches a certain temperature as shown in FIG. 1, the forward voltage V _F when the gate is on matches the forward voltage V _F. This is because as the temperature rises, the junction voltage formed between the p anode region 13 and the n cathode region 14 decreases, and the amount of holes generated in the n base layer 3 increases, so that the n base layer 3 This is because the conductivity modulation at increases as the temperature rises.

Therefore, as a first method for detecting the temperature from the forward voltage of the diode of FIG. 9, temperature sensing is performed by utilizing the temperature dependence of the forward voltage V _F at the time of gate-off shown in FIG. Is good. Specifically, with the voltage between C and E set to zero and the voltage on the gate electrode 7 also set to zero, a constant current is passed from the current source 18 and the voltage between the anode electrode 15 and the cathode electrode 16 is measured, It is assumed that the temperature is determined from the curve (a) in FIG. Precise temperature determination can be performed without being affected by the IGBT section and because of the large forward voltage.

As a second method, temperature sensing can be performed by utilizing the temperature dependence of the forward voltage V _F at the time of gate on shown in FIG. Specifically, with the voltage between C and E set to zero and an ON signal applied to the gate electrode 7,
A constant current is made to flow from the current source 18, the voltage between the anode electrode 15 and the cathode electrode 16 is measured, and the temperature is judged from the curve (b) of FIG. There is no bending point, it is not easily affected by noise, etc., and stable temperature determination can be performed.

FIG. 2 shows a temperature dependence curve of the forward voltage of the temperature sensing diode in another IGBT. The horizontal axis represents temperature and the vertical axis represents forward voltage of the diode. In FIG. 1, two forward current-voltage curves were generated when the gate was on and when the gate was off, and the two curves were seen to coincide with each other at around 130 ° C. FIG.
In the above, the curve when the gate is off and the curve when the gate is on are matched near room temperature. One way to do this is to increase the current flowing from the current source 18 to the temperature sensing diode 17 as much as possible. The other is to get as close to the main IGBT as possible.

The former is to increase the current value to increase the current flowing from the p anode region 13 to the n base layer 3 to accelerate the operation of the pnp transistor.
The latter may be a method of promoting the operation of the pnp transistor by bringing them closer to each other. If the temperature at the cross point where both curves coincide is lowered, the curve of the forward voltage becomes one in a wide range above the temperature. A third method of the present invention is to detect in the range where the curve of the forward voltage becomes one. This allows
Suppressing complication, stable detection can be performed in a wide range.

FIG. 3 shows a temperature dependence curve of the forward voltage of the temperature detecting diode in another IGBT. The horizontal axis represents temperature and the vertical axis represents forward voltage of the diode. In FIG. 3, contrary to FIG. 2, the temperature at the cross point where the two curves coincide is shifted to a high temperature side to some extent. As a method therefor, the method is the opposite of that shown in FIG. 2, and the driving of the pnp transistor may be suppressed. Either reduce the current flowing through the temperature sense diode or separate the temperature sense diode from the IGBT section. The temperature at the cross point should be close to the overheat detection temperature.

As a fourth method of the present invention, if the difference between the forward voltage when the gate is off and that when the gate is on is taken with such a diode, it is possible to easily determine whether the cross point temperature is above or below. Next, consider the case where a voltage is applied between the collector and the emitter of the IGBT. in this case,
When the gate is off, from the p anode region 13 to the n base layer 3
No current flows to the temperature sensing diode, and the forward voltage of the temperature sensing diode is no different from that when no voltage is applied between the collector and the emitter. However, when the gate is turned on, the IGBT is turned on, and a current flows in a wide range. Therefore, a large amount of excess carriers exist in the n base layer 3, and a current easily flows from the p anode region 13 to the n base layer 3. , The forward voltage of the diode becomes low. Moreover, since the density of excess carriers changes, depending on the magnitude of the current flowing in the IGBT,
The forward voltage of the diode also fluctuates slightly.

FIG. 4 is a diagram showing timings of signals and the like for explaining the fifth and sixth methods of the present invention. The horizontal axis is time. That is, as a fifth method, a pulse (4a) is generated from the pulse generator in synchronization with the gate signal (1) and the forward voltage of the diode is measured in a pulsed manner, and the off period of the gate signal, that is, The temperature is detected only during the period when V _CE (2) is applied to both ends of the IGBT. This is a method that enables stable temperature detection.

On the contrary, as the sixth method, the gate signal is turned on.
I period, that is, the current I _C(3) is flowing
Gate signal to detect temperature only during
Pulse (4b) from the pulse generator synchronized with (1)
That measures the forward voltage of the diode in a pulsed manner
It is. In this case, the current of the IGBT as described above
Causes the temperature dependence curve of the forward voltage to fluctuate slightly.
So, for precise temperature setting, make a calibration curve with current
It is desirable to put it.

By adopting the fifth and sixth methods, the temperature can be detected during the operation of the IGBT, so that extra time such as stopping the voltage application is not required for the temperature detection. Although the n-channel region type IGBT has been described in the above embodiments, the same applies to the p-channel IGBT in which the conductivity types are exchanged. In addition, MCT (moss control thyristor) other than IGBT, EST (emitter separation thyristor), BSI
It is also applicable to devices such as T and SITh (static induction thyristor), and is effective as long as it is a bipolar semiconductor device having a control electrode and injecting minority carriers.

[0031]

As described above, according to the temperature detecting method of the present invention, in the bipolar semiconductor device having the temperature detecting diode built therein, the forward voltage depends on the temperature with or without the control signal. Precise temperature detection is possible by utilizing the characteristics. By using a range in which both the forward voltage with the control signal and that with the control signal do not match, more stable temperature detection is possible. It is also possible to detect the temperature from the difference between the two. It is also possible to detect the temperature during the operation of the bipolar semiconductor device by the pulse-like measurement.

As a result, it is possible to take a prompt and appropriate response to the detected temperature, such as reducing the current to prevent thermal runaway. In addition, it is possible to reduce the risk rate that was largely seen in preparation for inaccurate temperature, or the design margin.
The semiconductor device performance can be fully utilized.

[Brief description of drawings]

FIG. 1 is a temperature dependence curve of a forward voltage of a diode formed in an IGBT.

FIG. 2 is a temperature dependence curve of a forward voltage of a diode formed in another IGBT.

FIG. 3 is a temperature dependence curve of a forward voltage of a diode formed in another IGBT.

FIG. 4 is a diagram showing timings of signals and the like for explaining the fifth and sixth methods of the present invention.

FIG. 5 is a diagram showing timings of signals and the like in a semiconductor having a conventional heating prevention circuit.

FIG. 6 is a temperature dependence curve of the forward voltage of the diode.

FIG. 7: Forward current-voltage curve of diode formed in IGBT

FIG. 8 is a partial cross-sectional view of an IGBT with a built-in diode.

FIG. 9 is a partial sectional view of an IGBT in which another diode is built.

[Explanation of symbols]

1 p substrate 2 n ⁺ buffer layer 3 n base layer 4 p base region 5 n emitter region 6 gate oxide film 7 gate electrode 8 emitter electrode 9 collector electrode 10 oxide film 11 insulating film 12 channel region 13 anode region 14 cathode region 15 anode Electrode 16 Cathode electrode 17 Temperature detection diode 18 Current source 20 IGBT part 21 Hole extraction region 23 p-type region 24 p-type region

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seiji Momota 1-1, Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Fuji Electric Co., Ltd.

Claims (6)

[Claims] 1. A method for forming a temperature detecting section composed of a pn junction type diode on a semiconductor substrate of a bipolar semiconductor element having a control electrode and detecting the temperature from the temperature dependence of the forward voltage of the diode, wherein a control signal is turned on. A method for using a bipolar semiconductor device with a built-in temperature detector, characterized in that the forward voltage of the diode is measured to detect the temperature. 2. A method of forming a temperature detecting section composed of a pn junction type diode on a semiconductor substrate of a bipolar semiconductor element having a control electrode, and detecting the temperature from the temperature dependence of the forward voltage of the diode, wherein the control signal is turned off. A method for using a bipolar semiconductor device with a built-in temperature detector, characterized in that the forward voltage of the diode is measured to detect the temperature. 3. A method of forming a temperature detecting section composed of a pn junction type diode on a semiconductor substrate of a bipolar semiconductor element having a control electrode, and detecting the temperature from the temperature dependence of the forward voltage of the diode, wherein a control signal is turned on. A method for using a bipolar semiconductor device with a built-in temperature detector, comprising measuring the forward voltage of a diode within a range where the forward voltage at the time of and the control voltage at the time of turning off the control signal are matched to detect the temperature. 4. A method of forming a temperature detecting section composed of a pn junction type diode on a semiconductor substrate of a bipolar semiconductor element having a control electrode, and detecting the temperature from the temperature dependence of the forward voltage of the diode, wherein a control signal is turned on. A method of using a bipolar semiconductor device with a built-in temperature detector, wherein the temperature is detected by the difference in the forward voltage of the diode between when the control signal is off and when the control signal is off. 5. A method for forming a temperature detecting section composed of a pn junction type diode on a semiconductor substrate of a bipolar semiconductor element having a control electrode, and detecting the temperature from the temperature dependency of the forward voltage of the diode. 5. The method for using the bipolar semiconductor device with a built-in temperature detecting section according to claim 1, wherein the forward voltage of the diode is measured when the voltage is applied to detect the temperature. 6. The method of using a bipolar semiconductor device with a built-in temperature detecting part according to claim 5, wherein the temperature is detected by a pulse generating means and a pulse-like voltage measuring means.