JPS62108570A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve yield by selectively oxidizing first and second poly crystalline semiconductor layers simultaneously and forming an electrode an a leading-out wiring for a transistor. CONSTITUTION:A buried layer 2 and an epitaxial layer 3 are shaped onto a semiconductor substrate 1, a thin oxide film 5 is formed onto the whole surface an an silicon nitride film 6 is shaped selectively, and collector, base and emitter regions are formed through selective oxidation, using the silicon nitride film as a mask. An silicon nitride film 11 and a thin oxide film 10 are removed, the surface of the epitaxial layer 3 is exposed, and a first polycrystalline semiconductor layer is shaped onto the whole surface. A base layer 8 is formed through selective ion implantation, a second polycrystalline semiconductor layer 15 is shaped onto the whole surface of the first polycrystalline semiconductor layer 13, and the first and second polycrystalline semiconductor layers are oxidized selectively at the same time to form an electrode and leading-out wirings 20, 21 for a transistor. Accordingly, the layer resistance of the wirings is lowered, and the yield of a semiconductor device can be improved largely.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method of manufacturing a semiconductor device, and in particular to a method of manufacturing a semiconductor device, in particular a method of manufacturing a semiconductor device, in which one end of an emitter is formed by an oxide film formed by selectively oxidizing a semiconductor substrate, and a transistor including the emitter is formed. The present invention relates to a method of manufacturing a semiconductor device in which electrodes and lead wiring are formed by selectively oxidizing a polycrystalline semiconductor layer.

[Conventional technology]

Conventionally, this type of semiconductor device has been manufactured as follows.

First, as shown in FIG. 2, there are four semiconductor substrates 1 of the first conductivity type.
A layer 2 of a second conductivity type and an epitaxial layer 3 are formed on the epitaxial layer 3, and impurities of a first conductivity type are selectively added onto the epitaxial layer 3 to reach a semiconductor substrate of the first conductivity type. Then, the insulating region 4 is formed.

Next, a thin oxide film 5 and a selective silicon nitride film 6 are formed on the semiconductor substrate, and the semiconductor substrate is selectively oxidized using the silicon nitride film as a mask to form collector, base, and emitter regions.

Next, a base layer is formed, and there are three methods for this.

In the first method, a photoresist is selectively formed from the state shown in FIG. 2, and ions are implanted through the silicon nitride film 6 and thin oxide film 5 using the photoresist as a mask to form a base layer. After removing the photoresist, the silicon nitride film 6 and thin oxide film 5 are removed to expose the surface of the epitaxial layer and form a polycrystalline semiconductor layer on the entire surface.

The second method is to remove the silicon nitride film 6 and the thin oxide film from the state shown in FIG. 2 to expose the surface of the epitaxial layer, then selectively form a photoresist, and use the photoresist as a mask to expose the surface of the epitaxial layer. The base layer is formed by direct ion implantation. After removing the photoresist, a polycrystalline semiconductor layer is formed on the entire surface.

In the third method, the surface of the epitaxial layer is exposed in the same manner as in the middle steps of the second method, a polycrystalline semiconductor layer is formed on the entire surface, and then selectively photocoated.

A resist is formed, and ions are implanted through the polycrystalline semiconductor layer using the photoresist as a mask to form a base layer.

After forming the base layer and the polycrystalline semiconductor layer using one of the first to third methods, as shown in FIG. A silicon nitride film 11 is formed, and the polycrystalline semiconductor layer 9 is selectively oxidized using the silicon nitride film 11 as a mask to form electrodes such as the collector, emitter, and base of the transistor and lead wiring.

Next, as shown in FIG. 4, in order to reduce the contact resistance between the base layer 8 and the electrode lead wiring layer 9 formed by selectively oxidizing the polycrystalline semiconductor layer, a silicon nitride film 11 is formed on the base layer 8. Then, the thin oxide film 10 is selectively removed, and impurities of the first conductivity type are added from above the base lead-out wiring layer to the base layer, and oxidized to form a thick oxide film 14 on the surface.

Next, the silicon nitride film and thin oxide film on the collector and emitter lead-out wiring layers are selectively removed, and a second conductivity type impurity is added from above the wiring layer to form an emitter, and at the same time, the collector lead-out wiring and the collector are Reduce contact resistance.

Thereafter, as shown in FIG. 5, the silicon nitride film and oxide film on the wiring layer are removed, and a noble metal such as platinum is deposited on the entire surface and heat treated to form a low-resistance silicide layer on the wiring layer. Then, platinum on the oxide film is removed. Note that FIG. 6 is a plan view of FIG. 5.

[Problem that the invention seeks to solve]

In the conventional semiconductor device manufacturing method described above, there are three types of methods for forming the base layer.

Here, in order to explain the three types of methods in detail, a cross section in the B-B' force direction of the transistor shown in the plan view of FIG. 6 will be explained.

First, in the first method, as shown in FIG. 7(a), after selective oxidation of the semiconductor substrate, ions are implanted through the silicon nitride film 6 and the thin oxide film 5 using the photoresists 1 to 22 as masks. A layer 8 is formed (the buried layer, epitaxial layer, etc. are omitted in the figure). Next, after removing the photoresist 22, the silicon nitride film 6 is removed, and the thin oxide film 5 is treated with hydrofluoric acid or the like. It is removed by immersing it in Socinda solution, but at this time, because the etching speed of the oxide film at the end of the emitter is fast, the oxide film at the end of the emitter becomes large and etched and soothed, as shown at 23 in Figure 7(b). This shortens the distance between the oxide film at the emitter end and the collector junction.

Next, as shown in FIG. 7(c), a polycrystalline semiconductor layer is formed on the entire surface, and an emitter is formed as described above. As shown in the figure, since the distance between the collector and emitter at the emitter end 23 is short, the withstand voltage between the collector and emitter decreases, and short circuit between the collector and emitter may occur, which causes a deterioration in the yield of semiconductor devices. It had become.

In the second method, as shown in FIG. 8(a), a semiconductor substrate is selectively oxidized to form collector, base, and emitter regions. Next, the silicon nitride film and the thin oxide film are removed, and ions are implanted using a photoresist as a mask to form a base layer.

Since the surface of the epitaxial layer is already exposed, there is no need to immerse it in an etching solution such as hydrofluoric acid, and the oxide film at the end of the emitter will not be etched, so it is possible to maintain a certain distance between the collector emitter and the ivy. can.

However, in this second method, since ions are directly implanted into the surface of the epitaxial layer, a crystal defect generating layer 25 is generated on the surface of the base layer as shown in FIG. 8(b), which causes a decrease in the yield of transistors.

In addition, the third method is to carry out a second process after selective oxidation of the semiconductor substrate.
After exposing the surface of the epitaxial layer in the same manner as in the middle steps of the method described above, a polycrystalline semiconductor layer is formed on the entire surface, and ions are implanted through the polycrystalline semiconductor layer using a photoresist as a mask to form a base layer. The cross-sectional view at this time is shown in Figure 9 (
Shown in a>.

Next, after removing the photoresist 22, the polycrystalline semiconductor layer 26 is selectively oxidized to form an electrode lead wiring layer. A cross-sectional view at this time is shown in FIG. 9(b). According to the third method, since the oxide film constituting the emitter end is not etched after the base layer is formed, the distance between the collector emitter and the ivy can be kept constant. , problems such as the occurrence of crystal defects can be solved.

However, in the third method, ions are implanted through the polycrystalline semiconductor layer to form the base layer, so if the polycrystalline semiconductor layer is formed thickly, it becomes difficult to control the base layer resistance and the junction depth. Semiconductor layers can only be formed thinly.

Therefore, even if a silicide film made of a noble metal is formed on a wiring layer formed by selectively oxidizing a polycrystalline semiconductor layer, the silicide film can only be formed thinly, increasing the layer resistance of the wiring, which poses a major constraint on circuit design. On the other hand, when forming a silicide film, noble metals diffuse through the polycrystalline semiconductor layer and easily reach the emitter-base junction, causing emitter-base short circuits and adversely affecting the yield of semiconductor devices.

The purpose of the present invention is to eliminate the above-mentioned conventional drawbacks, to be able to maintain a constant distance between emitter and collector, to prevent crystal defects from occurring on the surface of a single crystal, and to form a thick silicide film to prevent wiring. To provide a method for manufacturing a semiconductor device in which layer resistance can be lowered, precious metals are not diffused and reach an emitter-to-base junction, and as a result, restrictions on circuit design are removed and yield can be improved. There is a particular thing.

[Means for solving problems]

In the method for manufacturing a semiconductor device of the present invention, an oxide film formed by selectively oxidizing a semiconductor substrate constitutes one end of an emitter, and a polycrystalline semiconductor layer is selectively oxidized to form an electrode and lead wiring of a transistor including the emitter. In a method for manufacturing a semiconductor device, a buried layer and an epitaxial layer are formed on a semiconductor substrate, a thin oxide film and a selective silicon nitride film are formed on the entire surface, and selective oxidation is performed using the silicon nitride film as a mask. a step of forming a collector, a base and an emitter region; a step of removing the silicon nitride film and the thin oxide film to expose the surface of the epitaxial layer and forming a first polycrystalline semiconductor layer on the entire surface; a step of forming a base layer by ion implantation into the base layer, a step of forming a second polycrystalline semiconductor layer on the entire surface of the first polycrystalline semiconductor layer, and simultaneously selecting the first and second polycrystalline semiconductor layers. The method includes a step of oxidizing to form transistor electrodes and lead wiring.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings. FIGS. 1(a) to 1(C) are cross-sectional views of main steps shown in the order of steps for explaining an embodiment of the present invention. Note that the manufacturing process using the same method as the conventional method will be explained using the above-mentioned conventional explanatory drawings.

First, an epitaxial layer is formed on a semiconductor substrate and selectively oxidized to form a collector, a base, and an emitter/vine region according to the conventional manufacturing method described in FIG.

Next, as shown in FIG. 1(a), the thin oxide film and silicon nitride film are removed to expose the surface of the epitaxial layer as in the conventional third method, and a first polycrystalline semiconductor layer 26 is formed on the entire surface.
form. Thereafter, a photoresist 22 is selectively formed, and ions are implanted using the photoresist as a mask to form a base layer 8.
form.

Note that 7 is a selective oxide film.

Next, as shown in FIG. 1(b), the photoresist is removed and a second polycrystalline semiconductor layer 28 is formed on the first polycrystalline semiconductor layer 26.

Next, as shown in FIG. 1(c), a first polycrystalline semiconductor layer 26 is formed according to the conventional manufacturing method shown in FIGS. 3 to 5.
At the same time, the second polycrystalline semiconductor layer 28 is selectively oxidized to form a selective oxide film 32, and electrode lead wirings for collector, base, emitter, etc. are formed. Next, impurities of the first conductivity type are added to reduce the contact resistance between the electrode lead wiring layer and the base layer by the method shown in FIG. 4, and then a silicon nitride film and a thin oxide film are added on the collector and emitter lead wirings. is selectively removed and impurities of the second conductivity type are added from above the wiring layer to form the emitter layer 29 and at the same time reduce the contact resistance between the collector lead-out wiring and the collector.

After that, the silicon nitride film and oxide film on the wiring layer are removed,
A noble metal such as platinum is deposited on the entire surface and heat treated to form a low resistance silicide film 16 on the wiring layer. Next, this example is completed by removing the platinum on the oxide film.

〔Effect of the invention〕

As explained above, according to the present invention, since the oxide film constituting one end of the emitter is not etched after the base layer is formed, the distance between the collector emitters can be kept constant, and the distance between the collector emitters can be kept constant. Since the base layer is formed by implanting ions through the layer, crystal defects can also be prevented from occurring.

Furthermore, by forming the second polycrystalline semiconductor layer, the wiring layer can be made thicker, so the silicide film can also be made thicker, and the layer resistance of the wiring can be lowered.

Furthermore, even if the noble metal diffuses into the polycrystalline semiconductor layer during the formation of the silicide film, it will not reach the emitter base junction because the film is thick. Therefore, restrictions on circuit design can be removed, and the yield of semiconductor devices can be greatly improved.

[Brief explanation of drawings]

Figures 1 (a) to (C) are cross-sectional views of the main steps shown in order to explain one embodiment of the present invention, and Figures 2 to 5 illustrate a conventional method of manufacturing a semiconductor device. 6 is a plan view of the semiconductor device shown in FIG. 5,
FIGS. 7(a) to 9(c) to FIGS. 9(a) to 9(b) are sectional views of the main steps for explaining three methods of forming a base layer using conventional manufacturing methods. 1... Semiconductor substrate of first conductivity type, 2... Buried layer of second conductivity type, 3... Epitaxial layer of second conductivity type,
4... Insulating region of first conductivity type, 5... Thin oxide film,
6... Silicon nitride film, 7... Selective oxide film, 8...
・Base layer, 9... Polycrystalline semiconductor layer, 10... Thin □
11... silicon nitride film, 12... selective oxide film, 13... polycrystalline semiconductor layer of first conductivity type, 14
... Thick oxide film, 15... Second conductivity type polycrystalline semiconductor layer, 16... Silicide film, 17... End of base layer, 18... Base layer, one... Base electrode lead wiring, 20... Emitter electrode lead wiring, 21
. . . Collector electrode lead wiring, 22 . . . Photoresist, 23 . Semiconductor layer, 27... selective oxide film, 28... second
polycrystalline semiconductor layer, 29...emitter layer, 30...
First polycrystalline semiconductor layer, 31... Second polycrystalline semiconductor layer, 32... Selective oxide film 6 2 Bacterial recruitment S Figure Kaya/WJ Yakyo, 5' Concave diagram

Claims (1)

[Claims] In a method of manufacturing a semiconductor device, one end of an emitter is formed by an oxide film formed by selectively oxidizing a semiconductor substrate, and an electrode and lead wiring of a transistor including the emitter are formed by selectively oxidizing a polycrystalline semiconductor layer. After forming a buried layer and an epitaxial layer on the substrate, forming a thin oxide film and selectively a silicon nitride film on the entire surface, and selectively oxidizing the silicon nitride film using the silicon nitride film as a mask to form a collector, base, and emitter region. , a step of removing the silicon nitride film and the thin oxide film to expose the surface of the epitaxial layer and forming a first polycrystalline semiconductor layer on the entire surface; a step of selectively implanting ions to form a base layer; a second polycrystalline semiconductor layer; and a step of simultaneously selectively oxidizing the first and second polycrystalline semiconductor layers to form transistor electrodes and lead wiring. Method of manufacturing the device.