JPH0236538A - Semiconductor device - Google Patents

Abstract

PURPOSE:To eliminate the problem of 'eye opening' by a method wherein emitters and a damper diode contact part are separated from each other by covering lateral part of the emitter diffused layers of a transistor with a surface oxide film. CONSTITUTION:Emitter n<+> diffused layers 4 are formed in the surface of a base p-type layer 3 using an oxide film 5 as a mask. At this time, the dimension (l1) of the film 5, which is used as a diffusion mask, of a damper diode contact part is wide and peripheral parts 4a of the layers 4 are extended in the lateral direction under the film 5. A contact window is opened on a surface oxide film 13 and the contact window is provided in such a way that the dimension (l2) of a window hole 9 of the damper diode contact part is smaller than the dimension (l1) and the window hole at least is not placed on the lateral layers 4. An Al electrode to come into ohmic contact to the contact window hole is provided to complete a transistor with a build-in damper diode. When an emitter and a collector of the transistor are turned-OFF and a large current flows, a base-collector junction directly under the damper diode contact part works as the damper diode and protects the junction between emitters from being broken.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a technique for improving the breakdown resistance of a transistor with a built-in damper diode.

[Conventional technology]

In a Brainer type transistor, for example, a power transistor for TV water horizontal deviation, the base (
A structure is known in which a resistor (2) is provided between D and emitter (E), and a diode DY is connected between emitter [F] and collector C as a damper. This damper diode has changed from the conventional external type to the built-in type that utilizes a base-collector junction.

FIG. 2g5 is a partial cross-sectional view showing an example of a triple diffusion type npn transistor with a built-in damper diode. A p-type semiconductor layer 3 is formed on the upper surface of the base semiconductor substrate l and the n-type diffusion layer 2 formed on its lower surface as a collector, and several n-type diffusion layers 4 are formed on the surface of the paste p-layer 3. The emitter of this npn transistor is used as an emitter, and a part of the surface of the base surrounded by this emitter is connected to the electrode on the emitter as a contact part of a damper diode, and is used as a base region under the emitter. When the collector is turned off, the base-collector junction directly below the contact portion functions as a damper diode. [Problem to be solved by the invention] In the transistor with a built-in damper diode described above, the contact window of the damper diode is made as large as possible. Although it is desirable that the contact window be small in area, this causes a problem of the "opening" phenomenon in which a part of the contact window covers the emitter diffusion layer. This is because, as shown in FIG. 7, when emitter diffusion is performed using the surface oxide film 5 of the semiconductor layer 3 as a mask, the impurities are also diffused in the lateral direction, so the diffusion layer 6 slightly digs into the area where the contact window is to be formed. It takes shape.

After this, a contact hole is formed using a photoresist process, and a damper diode contact portion Ak is formed as shown in FIG.
An electrode 7 is provided, but in that case, when a part of the electrode 7' is applied to the emitter diffusion layer and a large current flows through the damper diode, the damper diode current i passes through the emitter from the opening part 8, and as a result, The withstand capacity of the discharge ASO test will be weakened.

In the above-mentioned conventional technology, for example, the dimension 1t of the contact window of the diper diode is made almost equal to or slightly smaller than the width β of the mask for emitter diffusion.
Not enough consideration was given to the "opening" of the damper diode contact window, which caused the above-mentioned problem.

An object of the present invention is to provide sufficient consideration to the width of lateral diffusion during emitter diffusion, and to perform isolation using an oxide film so as to eliminate the "opening" problem.

[Failure to solve the problem]

The above purpose is to separate the damper diode contact part from the S-shaped vines by covering the horizontally extending portion of the emitter diffusion layer of the transistor with a surface oxide film in a transistor with a built-in damper diode that utilizes a base-collector junction. This is achieved by

[Effect]

In a transistor with a built-in damper diode configured as described above, the damper diode contact portion is separated from the emitter by covering the portion extending in the lateral direction of the emitter diffusion with a surface oxide film, thereby increasing the opening of the emitter diffusion layer. Therefore, the damper diode current does not pass through the perforated part from the damper diode electrode, and therefore, the withstand capacity of the discharge ASO test is not reduced.

〔Example〕

FIGS. 1 to 3 show an embodiment of the present invention, and are cross-sectional views of some steps in the transistor manufacturing process when a damper diode is incorporated in a triple diffusion type NPN transistor.

Figure 1 is a cross-sectional view during emitter diffusion, showing a form in which an emitter n+ diffusion layer 4 is formed on the surface of a base p-type layer 3 using an oxide film 5 as a mask. The dimension C3 of the oxide film 5 is set wide, and the peripheral part 4a of the n-diffusion layer 4 extends laterally below the oxide film 5.

FIG. 2 shows a form in which a contact window is formed in the surface oxide film 13, and the dimension of the window hole 9 of the contact part of the damper diode is smaller than L, so that it does not cover at least the emitter diffusion layer K extending in the lateral direction. do. 10 is a window hole for base contact.

In FIG. 3, ohmic contact is made to the contact window hole. FIG. 3 is a cross-sectional view of a main part showing a completed transistor with a built-in damper diode provided with an electrode.

7 was provided at the damper diode contact section. 1 electrode, 11 is a base electrode provided on the base contact 10,
Reference numeral 12 denotes an emitter electrode that contacts an emitter diffusion layer located at a remote location. The contact portion electrode 7 of the damper diode 9 and the emitter electrode 12 are connected to each other by an AA wiring (not shown). When the emitter and collector of the transistor are turned off and a large current flows, the base Φ collector junction directly under the damper diode contact portion acts as a damper diode, protecting the emitter junction from destruction.

FIG. 4 is a plan view corresponding to FIG. 3, and shows contact window holes 9, 10. The diffusion mask (dimensions are indicated by 81) and the butter/of the diffusion layer peripheral portion 4a are shown.

The figure shows a state in which the surface oxide film 13 on the emitter diffusion layer 4 covers the peripheral portion 4a of the diffusion layer and extends to the contact hole.

〔Effect of the invention〕

According to this embodiment, since the oxide film 13 completely covers the surface of the emitter junction, the diode current flows without passing through the emitter, resulting in the effect of improving the breakdown resistance of the discharge ASO.

According to this embodiment, the effect of improving the reliability of the power transistor can therefore be obtained.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the present invention, and are cross-sectional views of main parts showing the manufacturing process of a transistor with a built-in damper diode. FIG. 4 is a plan view showing the pattern of the peripheral portion of the diffusion layer and the pattern of the contact window hole corresponding to FIG. 3. FIG. 5 is a sectional view showing an example of a transistor with a built-in damper diode. FIG. 6 is an equivalent circuit diagram of the transistor shown in FIG. 5. 7 and 8 are cross-sectional views showing some steps in the manufacturing process of a transistor with a built-in damper diode. I...n-type semiconductor substrate (collector), 2...n-type diffusion layer (collector/contact formation part), 3...p-type diffusion layer (base), 4...n+-type scattering layer emitter)
, 5... Oxide film, 7... Damper diode contact part electrode, 8... Emitter diffusion layer periphery, 9...
・Damper diode contact part, 10... Base contact part, 11... Base electrode, 12... Emitter electrode. Figure 1

Claims (1)

[Claims] 1. A semiconductor substrate of a first conductivity type is formed as a collector on the surface of the substrate, and a semiconductor layer of a second conductivity type is formed as a base, and a diffusion layer of a first conductivity type that becomes an emitter is formed on a part of the base surface. A transistor is formed in which a part of the surface of the base is connected to the emitter as a wide-area contact part, and the base-collector junction directly under the base-collector junction is built in as a damper diode, and the contact part of the damper diode and its A semiconductor device characterized in that a peripheral emitter contact portion is electrically isolated by a surface oxide film of a diffusion layer that serves as an emitter. 2. The semiconductor device according to claim 1, wherein the emitter and damper diode contact portion are separated by covering a laterally extending portion of the emitter diffusion layer of the transistor with a surface oxide film.