JPH06117942A - Semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a semiconductor device incorporating a temperature detecting element exhibiting such characteristics as reflecting the element temperature accurately by forming the temperature detecting element on the surface of a semiconductor element through a dielectric film. CONSTITUTION:A dielectric film of 0.6-1.0mum thick is deposited on a gate oxide 7 and a poly-Si layer of about 1mum thick is then deposited thereon and subjected to ion implantation to form a p<+> layer 14 and an n<+> layer 15 constituting a temperature detecting diode. An anode electrode 11 to be connected with terminal A and a cathode electrode 12 to be connected with terminal C are provided on the surfaces of the layers 14, 15. A signal dependent on forward or reverse characteristics of diode is obtained from the electrode 11 or 12 and inputted through terminal A or C to a gate voltage control circuit thus protecting a gate isolation bipolar transistor against overheat. Since temperature of semiconductor element can be detected accurately without forming any parasitic element, safety operation region is widened in this semiconductor device.

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 built-in overheat protection function used for power switching.

[0002]

2. Description of the Related Art A semiconductor device used for power switching may be thermally destroyed due to overcurrent.
Therefore, it is desirable to have a built-in overheat protection function. For such an overheat protection function, a change in the forward characteristic or the reverse characteristic of the diode due to temperature is used. FIG. 2 shows a conventional insulated gate bipolar transistor having an overheat protection function (hereinafter referred to as an IGBT). The IGBT is
n stacked on the p ⁺ substrate 3 via the n ⁺ buffer layer
^A p base layer region 4 is selectively formed on the surface layer of the layer 1, and an n ⁺ source region 5 is selectively formed on the surface layer of the p base layer region 4, and the p base region 4 and the n ⁺ source region are formed. The surface of 5 is electrically short-circuited by the source electrode 6 connected to the source terminal S, and the gate is formed on the region sandwiched between the n ⁺ source region 5 of the p base region 4 and the exposed portion of the n ⁻ layer 1. The gate electrode 8 insulated from the source electrode 6 and the insulating film 9 is provided via the oxide film 7, and the drain electrode 10 connected to the drain terminal D is brought into contact with the back surface of the p ⁺ substrate 3 to complete the process. The overheat detection diode is n
^{The +} layer 1 includes a p ⁺ region 21 formed on the surface layer of the p layer 1 with a distance from the p base region 4, and an n ⁺ region 22 selectively formed on the surface layer. The p ⁺ region 21 is connected to the anode terminal A, the anode electrode 11, and the n ⁺ region 23.
The cathode electrode 12 connected to the cathode terminal C is connected to. In normal switching operation, the gate electrode 8
Is applied to the n ⁺ source region 5
Electrons are injected into the n ⁻ layer 1 and the n ⁺ buffer layer 2 from.
A positive voltage is applied to the p ⁺ substrate 10, holes are injected from the p ⁺ region 3, and the built-in p ⁺ substrate 3, n ⁺ buffer layer 2 and n ⁻ layer 1, p base region are formed. Four
The PNP transistor consisting of 1 operates to turn on the IGBT. When a voltage below the threshold value is applied to the gate electrode 8, the IGBT can be turned off because electron injection from the n ⁺ source region 4 is stopped. When the IGBT is operated at a constant frequency, heat is generated due to switching loss and steady loss of the element, and the temperature of the entire n ⁻ layer 1 rises.

FIG. 3 shows the forward IV characteristic of the overheat detecting diode composed of the p ⁺ region 21 and the n ⁺ region 22, where the line 31 is at room temperature and the line 32 is at high temperature. Therefore n ^- layer 1
Since the temperature rise of the electrode can be detected from the decrease of the saturation voltage, the electrode 1
If the operation of limiting the current is performed by reducing the voltage applied to the gate electrode 8 by the electric signals taken out from 1 and 12, the IGBT can be protected from overheating. FIG. 4 shows the reverse leakage current characteristic of the overheat detection diode, where point 41 is the leakage current with respect to a constant voltage at room temperature and at high temperature at point 42. Therefore, it is possible to detect the temperature rise from the increase of the leakage current and perform the operation of limiting the current.

[0004]

However, when the IGBT of the semiconductor device shown in FIG. 2 is turned off, holes which are minority carriers are injected from the n ⁻ layer 1 into the p ⁺ region 21,
The parasitic thyristor including the p ⁺ substrate 3, the n ⁺ buffer layer 2 and the n ⁻ layer 1, the diode p ⁺ region 21, and the n ⁺ region 22 malfunctions, and the control by the gate electrode 8 becomes impossible, leading to latch-up breakdown. In order to avoid the formation of such a parasitic thyristor, if the temperature detecting element is externally attached separately from the protection target element, the temperature of the semiconductor element body of the protection target element cannot be accurately detected.

An object of the present invention is to solve this problem, to form a semiconductor device having a temperature detecting element having a characteristic that accurately reflects the temperature of the semiconductor element body of the element to be protected without forming a parasitic element. To provide.

[0006]

[Means for Solving the Problems]
In addition to the main semiconductor device, the present invention
In a semiconductor device equipped with a temperature detection element for protection.
The temperature detection element is the main semiconductor element
The base is a semiconductor layer formed on the surface through an insulating film
I shall. The temperature detection element is the main semiconductor element.
First conductivity of the semiconductor layer formed on the surface through an insulating film
Region of the second conductivity type adjacent to the region of
Is a diode that has a semiconductor layer of
Being a polycrystalline silicon layer,
At least one of the areas is 5 × 10 ¹⁴Cm^-2Dose below
It is effective that it is formed by introducing impurities.

[0007]

Since the temperature detecting element is formed in contact with the semiconductor element body of the main element, which is protection symmetrical, the temperature of the semiconductor element body can be accurately detected, but it is electrically insulated from the semiconductor element body. In addition, the destruction due to the parasitic effect of other elements does not occur.

[0008]

1 shows a semiconductor device according to an embodiment of the present invention having the same function as that of the semiconductor device of FIG. 2, and the same parts as those of FIG. 2 are designated by the same reference numerals. 2 is different from FIG. 2 in that the overheat detecting diode is not formed on the surface layer of the n ⁻ layer 1 and the gate oxide film 7 on the surface has a thickness of 0.6-
About 1 μm deposited on the insulating film 13 having a thickness of 1.0 μm
P formed by ion implantation into a polycrystalline silicon layer having a thickness of
It is composed of the ⁺ layer 14 and the n ⁺ layer 15. And
The anode electrode 1 connected to the terminal A is formed on the surfaces of the p ⁺ polycrystalline silicon layer 14 and the n ⁺ polycrystalline silicon layer 15.
1, cathode electrodes 12 connected to the terminal C are provided respectively.

A signal depending on the forward characteristic or the reverse characteristic of the diode obtained from the anode electrode 11 and the cathode electrode 12 is input from the terminals A and C to the gate voltage control circuit to protect the IGBT from overheating.
In this semiconductor device, since the temperature detecting diode is formed via the n ⁻ layer and the insulating film 13, it is possible to prevent the parasitic thyristor from operating due to the carrier due to dv / dt at the time of turn-off. When the reverse breakdown voltage is used to detect the temperature rise, the reverse IV characteristic 43 at room temperature and the reverse I at high temperature I as shown in FIG.
If the −V characteristic 44 is soft, the resolution of voltage detection is lowered, which leads to an error in temperature detection. But p
^{When one of the +} polycrystalline silicon layer 14 and the n ⁺ polycrystalline silicon layer 15 is formed by ion implantation with a dose amount of 5 × 10 ¹⁴ Cm ⁻² or less, the reverse IV characteristic is shown in FIG. As shown in, the avalanche characteristics are obtained, and the avalanche voltage rises as the temperature rises, improving the resolution of temperature detection.

[0010]

According to the present invention, since the temperature detecting element is provided on the semiconductor element body of the main element via the insulating film, the parasitic element is not formed and the temperature of the semiconductor element body is accurately measured. Therefore, a semiconductor device with a built-in overheat protection function with an expanded safe operation area was obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a semiconductor device having an IGBT as a main element and a built-in overheat protection function according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a conventional semiconductor device having an IGBT as a main element and a built-in overheat protection function.

FIG. 3 is a forward current-voltage temperature characteristic diagram of a temperature detection diode.

FIG. 4 is a reverse leakage current temperature characteristic diagram of the temperature detecting diode.

FIG. 5 is a reverse current voltage temperature characteristic diagram of a temperature detecting diode.

FIG. 6 is a reverse current-voltage temperature characteristic diagram of a temperature detecting die auto of a semiconductor device according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 n ^- layer 2 n ⁺ buffer layer 3 p ⁺ substrate 4 p base region 5 n ⁺ source region 6 source electrode 7 gate oxide film 8 gate electrode 10 drain electrode 11 anode electrode 12 cathode electrode 13 insulating film 14 p ⁺ polycrystalline silicon Layer 15 n ⁺ polycrystalline silicon layer

Claims (4)

[Claims] 1. A main semiconductor device further comprising a temperature detecting device for overheat protection of the device, wherein the temperature detecting device is provided on the surface of the semiconductor body of the main semiconductor device via an insulating film. A semiconductor device comprising the formed semiconductor layer as a base. 2. A diode in which a temperature detecting element is composed of a region of a first conductivity type of a semiconductor layer formed on the surface of a main semiconductor device with an insulating film interposed therebetween and a region of a second conductivity type adjacent to the region. The semiconductor device according to claim 1, wherein 3. The semiconductor device according to claim 2, wherein the semiconductor layer is a polycrystalline silicon layer. 4. At least one of the diode regions is 5 ×
4. The semiconductor device according to claim 3, which is formed by introducing impurities in a dose amount of 10 ¹⁴ Cm ⁻² or less.