JPH1050993A - Semiconductor device with current detecting function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a semiconductor device provided with a function for detecting the current flowing through an element itself utilizing the channel resistance in which the current can be detected with high accuracy at all times regardless of the temperature conditions of the element and the periphery thereof. SOLUTION: When an IGBT(insulated gate bipolar transistor) is provided with a probe electrode 9 to be connected electrically with one n-type diffusion layer 4 while being insulated electrically from the source electrode 8 thereof, for example, a voltage γ (rch+ra) is proportional to the source current (is) appears between the probe electrode 9 and the source electrode 8, where γis a constant, rch is a channel resistance and ra is an accumulation resistance. The voltage depends on the temperature because the (rch+ra) has a temperature coefficient but the temperature dependency is eliminated by compensating for the (rch+ra) based on the output from a temperature sensor 10 provided on same substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a current detecting function, and more particularly to a semiconductor device having a current detecting structure suitable for being applied to a semiconductor device such as a vertical MOSFET or a vertical IGBT (insulated gate bipolar transistor). Regarding improvement.

[0002]

2. Description of the Related Art In a semiconductor device such as a power MOSFET or an IGBT, a current detecting function is sometimes provided to protect an element. By providing such a current detection function, it is possible to detect the presence / absence of abnormality in the current flowing through these elements, and to achieve fail-safe such as stopping the drive before the elements are destroyed. Will be able to do it.

Conventionally, such a semiconductor device having a current detecting function is disclosed in, for example, JP-A-63-12175.
A semiconductor device described in Japanese Unexamined Patent Publication (Kokai) No. HEI 9-203 is known. In this semiconductor device, a voltage drop generated when a current flows through the channel portion is detected via a probe electrode provided near the channel portion, and a current flowing through the element is estimated based on the detected voltage drop. I have to.

That is, as described in the same publication, for example, when considering an N-channel MOSFET, if the resistance (channel resistance) of the channel portion is rch and the drain current is id, the above-mentioned probe electrode and source electrode , A voltage drop such as Vps = id × rch (1) occurs. Here, if the channel resistance rch is constant, the voltage drop (the voltage between the probe electrode and the source electrode) Vps is equal to the drain current i.
The drain current id, that is, the current flowing through the MOSFET can be estimated by measuring the voltage drop Vps.

[0005] By employing such a current detection structure, a current flowing in the semiconductor device can be detected without separately providing an external current detection resistor or the like.

[0006]

As described above, the current flowing in the semiconductor device is detected by measuring the voltage drop generated when the current flows through the channel through the probe electrode provided near the channel. Can do it.

As described above, in such a current detection structure, the constant value of the channel resistance rch in the above equation (1) is a critical factor in performing the current detection with high accuracy. It is a premise.

However, as a matter of fact, it is known that the channel resistance rch has a temperature coefficient (TCR), and the resistance value varies with temperature. When the value of the channel resistance rch fluctuates with temperature, the value of the current detected and estimated based on the voltage drop naturally becomes low in reliability.

The present invention has been made in view of such circumstances, and provides a semiconductor device with a current detection function that can always perform highly accurate current detection regardless of the temperature conditions of the element and its surroundings. The purpose is to do.

[0010]

In order to achieve the above object, according to the present invention, (a) a first semiconductor layer electrically connected to a first current-carrying electrode. (B) the first semiconductor layer formed on the main surface side of the first semiconductor layer;
A conductive second semiconductor layer; (C) A second conductivity type diffusion layer formed in a predetermined region on the main surface side in the second semiconductor layer. (D) a second current-carrying electrode formed in the second conductivity type diffusion layer and provided on the main surface side, or a probe electrode electrically separated from the second current-carrying electrode; A plurality of first conductivity type diffusion layers electrically connected; (E) a temperature sensor formed on the main surface of the first semiconductor layer and detecting the temperature of the semiconductor layer; (F) a potential correction circuit for correcting a potential generated at the probe electrode when the element is energized, based on a temperature detection output from the temperature sensor. And the amount of current flowing through the element is estimated based on the corrected probe electrode potential.

According to such a current detection structure as a semiconductor device having a current detection function, at the time of energization, at least the second semiconductor layer is provided between the probe electrode and the second energization electrode. A voltage drop caused by the resistance of the second conductivity type diffusion layer portion between the first conductivity type diffusion layer and the channel, that is, the channel resistance occurs. In addition, the temperature sensor provides temperature information around the channel resistance. Is extracted in a manner proportional to, for example, the absolute temperature.

Therefore, the potential generated at the probe electrode, that is, the voltage between the probe electrode and the second energizing electrode is set so that the aforementioned temperature coefficient (TCR) of the channel resistance is canceled based on the extracted temperature information. If correction is made through the potential correction circuit, current detection with high accuracy is always performed based on this corrected potential (voltage drop) regardless of the temperature conditions including the channel resistance and the surroundings. Will be able to do it.

Such a current detecting structure is also used for the above-mentioned IGBT (insulated gate bipolar transistor) used as a main switching element of, for example, an inverter for an electric vehicle, a general-purpose inverter, an uninterruptible power supply, an AC servo device, and the like. Extremely effective. That is, according to the invention as set forth in claim 2, in the semiconductor device, the first energizing electrode is a drain electrode, the second energizing electrode is a source electrode, and at least the second energizing electrode is a source electrode.
A vertical IGBT including a gate electrode as a control electrode on the second conductivity type diffusion layer between the semiconductor layer and the first conductivity type diffusion layer via an insulating film. According to such a configuration, the current flowing through the IGBT itself can be monitored with high accuracy, and the operation can be performed more accurately even if the aforementioned fail-safe is achieved.

On the other hand, according to the invention of claim 3,
(E1) The temperature sensor is a polycrystalline silicon diode formed on a main surface of the first semiconductor layer via an insulating film. According to such a configuration, the temperature sensor can be formed using the manufacturing process of the semiconductor device as it is, and the semiconductor with the current detection function can be formed as compared with the case where the temperature sensor is formed by other thin film thermistors or thin film resistors. The device can be manufactured efficiently. Further, the temperature sensor made of the polycrystalline silicon diode has good sensitivity (temperature coefficient) and is excellent in isolation from elements constituting the semiconductor device.

On the other hand, according to the invention described in claim 4, (f1) the potential correction circuit is a multiplication circuit for multiplying a potential generated at the probe electrode by a temperature detection output from the temperature sensor. According to this configuration, the above-described temperature coefficient (TCR) cancellation by the same potential correction circuit can be realized extremely efficiently. That is, since the resistance value of the channel resistance generally increases in proportion to the absolute temperature T, the temperature detection output by the temperature sensor is output in a form inversely proportional to the absolute temperature T. Thus, the temperature coefficient is accurately canceled based on the multiplication.

[0016]

FIG. 1 shows an embodiment of a semiconductor device having a current detecting function according to the present invention.

In this embodiment, an IG used as a main switching element of, for example, an inverter for an electric vehicle, a general-purpose inverter, an uninterruptible power supply, an AC servo device, etc.
The present invention is configured as a semiconductor device in which a current detection structure according to the present invention is applied to a BT (insulated gate bipolar transistor).

First, the structure of the IGBT according to the embodiment will be described in detail with reference to FIG. As shown in FIG. 1, the IGBT has a vertical structure, and the back surface of a p-type semiconductor substrate (silicon substrate) 1 is
It is electrically connected to the drain electrode 5 of the BT.

On the main surface side of the semiconductor substrate 1, n
A p-type diffusion layer 3 serving as a channel diffusion layer is formed in a predetermined region on the main surface side of the epitaxial layer 2.

In the p-type diffusion layer 3, an n-type diffusion layer 4 serving as a source layer is also formed in a predetermined region on the main surface side, and is electrically connected to the formed n-type diffusion layer 4. Source electrode 8 is formed.

In the IGBT according to the embodiment, as shown in FIG. 1 as “probe element portion”, only the same portion is exceptionally applied to the source electrode 8 (the source electrode 8 on the right side in FIG. 1). Are formed outside of the n-type diffusion layer 4,
Instead, a probe electrode 9 electrically separated from the source electrode 8 is formed so as to be electrically connected to one of the n-type diffusion layers 4. As will be described later in detail, at the time of energization, the source current of the IGBT is detected via the probe electrode 9.

On the other hand, a gate electrode 7 made of polycrystalline silicon is provided on the p-type diffusion layer 3 between the n-type epitaxial layer 2 and the n-type diffusion layer 4 via an insulating oxide film (silicon oxide film) 6. Are formed, and a vertical IGBT element portion which is added as “IGBT element portion” in FIG. 1 is configured including these gate electrodes 7.

In the IGBT according to the embodiment, a region of the main surface of the semiconductor substrate 1 (more precisely, the main surface of the n-type epitaxial layer 2) which is added as a "temperature sensor portion" in FIG. Further, a temperature sensor 1 made of a polycrystalline silicon diode via an insulating oxide film (silicon oxide film) 6
0 is formed. By adopting this polycrystalline silicon diode as the temperature sensor, the temperature sensor 1 can be manufactured using the manufacturing process of the semiconductor device as it is.
0 can be formed. Temperature sensor 1
0 is the temperature detection output by the electrodes 11, 12 and the terminal T.
1, and taken into the potential correction circuit 20 via T2.

The potential correction circuit 20 cancels a temperature-dependent component of the potential generated at the probe electrode 9 in proportion to the source current based on the temperature detection output from the temperature sensor 10 when the IGBT is energized. It is. In addition,
The potential correction circuit 20 may be integrated with the semiconductor device forming the IGBT, or may be provided separately from the semiconductor device forming the IGBT as an external processing circuit. Good.

Next, the operation of the IGBT according to the embodiment will be described in detail, including the principle of current detection. In the IGBT of the embodiment illustrated in FIG. 1, when a voltage exceeding a threshold is applied between the gate electrode 7 (terminal G) and the source electrode 8 (terminal S), the source current flowing through the IGBT unit cell is , Where is is expressed as is = is (e) + is (h) (2). In the equation (2), is (e) is an electron current, and is (h) is a hole current.

On the other hand, assuming that the channel resistance of the IGBT unit cell is rch and the accumulation resistance is ra, the potential at point A in FIG. 1 is VA, and VA = is (e)) (rch + ra). (3)

Here, the potential correction circuit 20 receives the voltage (the voltage of the terminal P) Vp of the probe electrode 9 at a high impedance with respect to the combined resistance (rch + ra), and the source current is (electron current is (e)). The same potential correction circuit 2)
Assuming that there is no outflow to the 0 side, the potential VA at the above point A is obtained.
And the voltage Vp at the terminal P are equal, and Vp = VA = is (e). (Rch + ra) (3) '. That is, although the potential VA at the point A is originally proportional to the source current is, by applying such conditions, the voltage Vp at the terminal P is also substantially proportional to the source current is.

Then, if a condition such as is (e) / is≡γ (constant) (4) is introduced, the above equation (3) ′ becomes Vp = VA = γ · (rch + ra) · is (5) The source current is obtained from the voltage Vp of the terminal P (hereinafter referred to as a probe voltage).

However, the channel resistance rch is equal to the temperature coefficient (T
CR) is as described above. In particular, the proportional coefficient (rch + ra) is 5000 ppm
It has been confirmed by the inventors that they have a temperature coefficient of about / K.

Therefore, in the IGBT of the embodiment, as described above, the temperature is detected through the temperature sensor 10 formed in the same semiconductor device, and based on the detected temperature, the potential correction circuit 20 is used. To cancel the temperature-dependent component included in the probe voltage Vp.

FIG. 2 shows a specific configuration example of such a potential correction circuit 20. Next, the temperature compensation structure of the IGBT of the embodiment will be described in further detail with reference to FIG.

As shown in FIG. 2, the potential correction circuit 20 is mainly composed of two circuits, a temperature detector 21 and a temperature compensator 22. Among them, the temperature detecting section 21 is composed of an operational amplifier A1 and resistors R1 to R3, and supplies a constant current to the polycrystalline silicon diode array constituting the temperature sensor 10;
An operational amplifier A2 constituting a buffer amplifier is provided.

From the temperature detecting section 21, a temperature signal Vt having a temperature coefficient inversely proportional to the absolute temperature T, ie, having a temperature coefficient of (1 / T) is sent to the temperature compensating section 22 via the buffer amplifier (operational amplifier) A 2. Output.

On the other hand, the temperature compensator 22
r1 and a differential amplification stage composed of Tr2 and a transistor Tr
3 is configured as a multiplication circuit. In such a multiplying circuit, as shown in FIG. 2, when the probe voltage Vp is input to the base electrode of the transistor Tr1 and the temperature signal Vt is input to the base electrode of the transistor Tr3, "current output" It is known that the multiplication calculation force represented by the following equation is expressed as Vout = {R5 / (Vh · R6)} × Vp × Vt (6) when this is set as Vout (for example, Alan
"Analog Integrated Circuits" by B. Grebene, Modern Science Company, 1
975). Here, R5 is the collector resistance of the transistors Tr1 and Tr2, R6 is the emitter resistance of the transistor Tr3, and Vh is the thermal voltage.

By performing such a multiplication through the temperature compensator 22, the fluctuation (temperature-dependent component) generated in the probe voltage Vp due to the temperature coefficient of the resistor (rch + ra) is (1 / T). The temperature signal Vt having the following temperature coefficient is suitably canceled.

That is, since the channel resistance rch and the accumulation resistance ra have a positive temperature coefficient, the probe voltage Vp increases in proportion to the absolute temperature T. By multiplying the temperature signal Vt having a temperature coefficient of 1 / T) in the form of the above equation (6), the temperature-dependent component is accurately canceled out, and the “current output” has higher accuracy. Thus, a signal corresponding to the flow rate of the source current is obtained.

As described above, according to the semiconductor device with a current detection function according to the embodiment, (a) the current flowing through the element is always detected with high accuracy regardless of the temperature condition of the semiconductor device. can do. (B) For this reason, even if the above-described fail-safe is achieved, the operation can be performed more accurately. (C) By using a polycrystalline silicon diode as the temperature sensor, the temperature sensor can be formed using the manufacturing process of the semiconductor device as it is, and the temperature sensor can be formed by using another thin film thermistor or thin film resistor. The semiconductor device with the current detection function can be manufactured more efficiently than in the case of forming. Also,
A temperature sensor made of a polycrystalline silicon diode has good sensitivity (temperature coefficient) and is excellent in isolation from elements constituting the semiconductor device. (D) Since the potential correction circuit (more precisely, the temperature compensator) is constituted by a multiplication circuit, cancellation of the temperature-dependent component can be realized extremely efficiently. Many excellent effects can be achieved.

In this embodiment, the effects (c) and (d) can also be obtained by employing a polycrystalline silicon diode as the temperature sensor or by configuring the potential correction circuit by a multiplication circuit. However, the semiconductor device with a current detection function according to the present invention is not limited to these adoptions or configurations.

That is, whatever the type of temperature sensor, or the configuration of the potential correction circuit,
Any device that can accurately detect the temperature of the semiconductor device and can cancel (correct) the temperature-dependent component of the probe voltage Vp based on the detected temperature information may be used.

In the embodiment, the semiconductor device with a current detection function according to the present invention is an n-channel IGB
Although the case where it applied to T was shown, p channel IGB
It goes without saying that the same applies to T.

The semiconductor device with a current detection function according to the present invention can be applied not only to these IGBTs but also to general power MOSFETs and the like that require current detection.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment of a semiconductor device with a current detection function according to the present invention.

FIG. 2 is a circuit diagram showing a specific configuration example of a potential correction circuit of the embodiment.

[Explanation of symbols]

1 ... p-type semiconductor substrate, 2 ... n-type epitaxial layer, 3 ...
p-type diffusion layer (channel diffusion layer), 4 ... n-type diffusion layer (source layer), 5 ... drain electrode, 6 ... insulating oxide film, 7 ... gate electrode, 8 ... source electrode, 9 ... probe electrode, 10 ... temperature Sensors (polycrystalline silicon diodes), 11, 12 ...
Temperature sensor output electrode, 20: potential correction circuit, 21: temperature detection unit, 22: temperature compensation unit, A1, A2: operational amplifier,
Tr1 to Tr3: transistors, R1 to R6: resistors, r
ch: channel resistance, ra: accumulation resistance.

Claims (4)

[Claims] A first semiconductor layer electrically connected to a first current-carrying electrode; a first conductivity-type second semiconductor layer formed on a main surface side of the first semiconductor layer; A second conductivity type diffusion layer formed in a predetermined region on the main surface side in the second semiconductor layer; and a second current-carrying electrode formed in the second conductivity type diffusion layer and provided on the main surface side or A plurality of first-conductivity-type diffusion layers electrically connected to one of the second current-carrying electrode and a probe electrode electrically separated from the second conduction electrode; and a plurality of first-conductivity-type diffusion layers formed on a main surface of the first semiconductor layer. A temperature sensor for detecting the temperature of the semiconductor layer; and a potential correction circuit for correcting a potential generated at the probe electrode when the element is energized based on a temperature detection output from the temperature sensor. Is used to estimate the amount of current flowing through the element. Current detection function wherein a. 2. The semiconductor device according to claim 1, wherein the first current-carrying electrode is a drain electrode, the second current-carrying electrode is a source electrode, and at least the second semiconductor layer and the first conductivity type diffusion layer are provided. 2. The semiconductor device with a current detecting function according to claim 1, wherein the semiconductor device has a vertical insulated gate bipolar transistor including a gate electrode as a control electrode on the second conductive type diffusion layer via an insulating film. 3. The semiconductor device with a current detection function according to claim 1, wherein said temperature sensor is a polycrystalline silicon diode formed on a main surface of said first semiconductor layer via an insulating film. 4. The semiconductor device with a current detection function according to claim 1, wherein said potential correction circuit is a multiplication circuit for multiplying a potential generated at said probe electrode by a temperature detection output from said temperature sensor.