JPH03240240A - Semiconductor device - Google Patents

Abstract

PURPOSE:To include a protective diode in a transistor element by using a comparatively small area, by a method wherein the anode diffusion layer of a diode is formed in the emitter diffusion layer of a transistor, and a protective diode is constituted. CONSTITUTION:When a backward bias is applied across the base-emitter of a transistor, a current flows firstly to the earth potential through a resistor formed by an N-type emitter diffusion layer 7 of a transistor just under a P-type anode diffusion layer 8 of a protective diode. When the voltage drop becomes higher than the forward voltage of the diode, the PN junction of the diode turns to the forward bias, and the current is absorved through the diode, so that the transistor is protected. In this manner, by forming the layer 8 of a protective diode in the layer 7 of a transistor, connecting them by using a wiring metal layer 10, forming a contact window as the cathode of the diode on the surface of the layer 7 across the layer 8 from a contact window of the layer 7, and forming a wiring metal layer 11, a protective diode can be included in a transistor element, by using a comparatively small area.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a semiconductor device used for power regulators, motor controls, and the like.

BACKGROUND OF THE INVENTION Conventionally, when a power transistor is used in a bipolar semiconductor device as a power supply regulator, motor control, etc., a power transistor Q! is used as shown in FIG. A diode D is connected to the emitter of the diode D. When used in power supply regulators, motor control, etc., if the signal from the previous stage suddenly stops or if there is a very strong noise signal, the base and emitter of the power transistor Q+ may become reverse biased, causing the transistor Q! may be damaged.

To prevent this, a protection diode D is connected to the emitter to absorb the reverse bias current.

FIG. 3 shows the circuit shown in FIG. 4 constructed using a bipolar semiconductor. 1 is a P-type semiconductor substrate, 2 is an N-type buried collector layer, 3 is an N-type epitaxial layer, 4 is a P-type buried isolation layer, 5 is a P-type isolation layer, 6 is a P-type base diffusion layer, 7 is an N-type semiconductor substrate
8 is an anode diffusion layer of a protection diode, 9 is a silicon dioxide film, and 10 is a wiring metal layer.

Problems to be Solved by the Invention In such a conventional structure, the N-type epitaxial layer 3 serving as the cathode region of the diode has a high resistance and is usually several tens of μm thick. Therefore, when a reverse bias is applied to the emitter, the voltage drop of the diode is large when the diode receives a large current, and the reverse bias current cannot be sufficiently absorbed. In addition, it is possible to absorb a large reverse bias current by increasing the area of the anode region of the diode, but this has the problem of increasing the area of the element and increasing the chip area of the product. .

The present invention solves these problems by installing a protective diode inside the transistor element that absorbs the current and prevents the transistor from being destroyed even when a reverse bias is applied between the base and emitter of the transistor and a large current flows. Another object of the present invention is to provide a semiconductor device that can be built in a relatively small area.

Means for Solving the Problem In order to solve this problem, the present invention forms an anode diffusion layer of a protection diode in the emitter diffusion layer of the transistor, forms a diode with this and the emitter diffusion layer, and also forms a diode with the emitter diffusion layer. The layer and the anode diffusion layer are connected by a wiring metal layer. Then, a contact window is provided as a cathode of the diode on the surface of the emitter diffusion layer that separates the anode diffusion layer from the contact window of the emitter diffusion layer.
By forming a wiring metal layer, a protection diode is built into the transistor.

Effect: With this configuration, even if a positive charge is applied to the emitter of the transistor, the current can be absorbed by the forward biased protection diode.

EXAMPLE An example of the present invention will be described in detail below with reference to FIGS. 1(a) and 1(b).

As shown in FIG. 1, an N-type epitaxial layer 3 having an N-type buried layer 2 is formed on a P-type semiconductor substrate 1, and element isolation is performed by a P-type buried isolation layer 4 and a P-type isolation layer 5. Next, a P-type base diffusion layer 6 of the transistor is formed, and an N-type emitter diffusion layer 7 is formed therein. Then, a diode anode diffusion layer 8 is formed in the emitter diffusion layer. And the emitter and base of the transistor are made of silicon dioxide @9.

Open contact windows for the collector and the anode and cathode of the diode. At this time, the distance a between the anode and cathode contact windows is set to be sufficiently shorter than the distance between the anode contact window of the diode and the transistor emitter contact window. FIG. 2 shows an equivalent circuit of FIG. 1. Protection diode D in the circuit
The resistor R connected in parallel to + is a squeeze resistor formed in the emitter diffusion layer directly below the anode diffusion layer of the diode. When a reverse bias is applied between the base and emitter, current initially flows through the resistor R to ground potential. Then, the voltage drop due to the resistance R is caused by the protection diode D
When the forward voltage of D1 becomes higher than that of D1, the protection diode D1
The PN junction of becomes forward biased, and through the diode,
The current is absorbed and transistor Q1 is protected. By setting the value of the squeeze resistor R so that the voltage drop caused by this is larger than the forward voltage of the diode, the current flowing through the squeeze resistor R can be adjusted. It is possible to set it so that

As explained in detail, according to the present invention, even if a reverse bias is suddenly applied between the base and emitter of a transistor, the current is absorbed by the squeeze resistor and protection diode connected to the emitter without destroying the transistor. I can do that. Since the amount of impurities at the anode and cathode of the protection diode is relatively high, the voltage drop is small, and the junction of the transistor can be sufficiently protected even at the time of large current. As described above, the semiconductor device of the present invention can be formed relatively easily by a normal bipolar process, and a protection diode with excellent forward characteristics can be incorporated in a transistor element in a relatively small area.

[Brief explanation of drawings]

FIG. 1 is a plan view of a semiconductor device according to an embodiment of the present invention;
2 is an equivalent circuit diagram of the semiconductor device of FIG. 1, FIG. 3 is a sectional view of a conventional semiconductor device, and FIG. 4 is an equivalent circuit diagram of the semiconductor device of FIG. 3. DESCRIPTION OF SYMBOLS 1... P-type semiconductor substrate, 2... N-type buried diffusion layer, 3... N-type epitaxial layer, 4...
...P type push separation layer, 5...P type separation layer, 6...P type base diffusion layer, 7...N
type emitter diffusion layer, 8...P type anode diffusion layer, 9... silicon dioxide film, 10°11...
...Wiring metal layer.

Claims (1)

[Claims] a first diffusion layer of a second conductivity type formed on a semiconductor substrate of a first conductivity type; a second diffusion layer of a first conductivity type formed within the first diffusion layer; and a second diffusion layer of the first conductivity type formed within the second diffusion layer. the second formed in
A third diffusion layer of a conductivity type, a first wiring layer connecting the second diffusion layer and the third diffusion layer, and a second diffusion layer on the opposite side of the third diffusion layer from the second diffusion layer. An electrode take-out window is provided adjacent to the electrode take-out window of the third diffusion layer based on the distance between the electrode take-out windows provided on the semiconductor substrate surface of the second diffusion layer and the third diffusion layer connected by the first wiring layer. a connected second wiring layer, a transistor is configured by the first and second diffusion layers and the semiconductor substrate;
A semiconductor device characterized in that a protection diode is formed by a second and third diffusion layer.