JPS6327863B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device, and in particular to a method for manufacturing a semiconductor device that uses a silicon nitride film for surface stabilization, particularly a semiconductor device that has a fine pattern and shallow junctions. be.

Conventionally, when a silicon nitride film is used in a semiconductor device for surface stabilization, each region within the semiconductor substrate is formed, then the silicon nitride film is deposited on the surface of the semiconductor substrate, and then external metal electrodes and A manufacturing method has been used in which openings for connection are selectively provided in the silicon nitride film. however,
This manufacturing method requires alignment work in the photo-etching process for the openings to be made in the silicon nitride film, and in order to provide alignment margin for this, it cannot be used in equipment that uses fine patterns. It was a manufacturing method.
Other methods include conversion of silicon nitride to anodic silicon oxide.
J.Electrochem.Soc.Vol114.No.6 ('67) entitled sillicon Nitride Films to anodic SiO ₂
Published in PP.603. This is bipolar
After forming the base and emitter regions of the transistor, holes are selectively formed in the silicon oxide film on the surface of the semiconductor substrate, and then, after a silicon nitride film is deposited on the substrate surface, the silicon oxide film is used as a mask. When anodic oxidation is performed, the silicon nitride film deposited on the silicon oxide film does not change, but the silicon nitride film deposited on the opening portion is converted into silicon oxide. In this state, it is immersed in a buffered hydrofluoric acid solution for several seconds, and using the difference in etching speed, the silicon oxide converted by anodic oxidation is etched away. As a result, this manufacturing method provides an opening in the silicon nitride film that reaches the semiconductor substrate. This manufacturing method is superior to the above-mentioned manufacturing method in that it provides fine patterned openings, but when the silicon nitride film is anodized, the semiconductor substrate is also anodized to some extent and removed. There is a drawback that it can be done. This is known to be due to the characteristics of semiconductor devices, for example, in the case of shallow junction transistors, a region with high impurity concentration at the contact part of the emitter is removed, resulting in a decrease in the current amplification rate of the transistor. ing. It is also known that the substrate surface is often removed, making ohmic connections with external metal electrodes impossible. Furthermore, it is known that if an electrode is formed of aluminum or the like and heat treated after the opening is formed, alloy spikes will occur particularly in the emitter region, reducing the yield of transistors.

An object of the present invention is to provide a new manufacturing method that eliminates the above-mentioned drawbacks that occur when converting a silicon nitride film into an anodic oxide film and that allows semiconductor devices to be manufactured stably and easily.

A feature of the present invention is that a first opening portion selectively formed in a first silicon oxide film covering one main surface of a semiconductor substrate of one conductivity type on which a base region of an opposite conductivity type is formed is formed to selectively reach the base region. a step of selectively forming a polycrystalline silicon semiconductor film on the first silicon oxide film in and around the first opening; and a step of forming a semiconductor film of polycrystalline silicon and the first opening. forming an emitter region of one conductivity type in the base region by introducing impurities of one conductivity type into the semiconductor substrate through the semiconductor substrate; and covering the semiconductor film with a second silicon oxide film; A second opening is formed in the second silicon oxide film, reaching a part of the upper surface of the semiconductor film, and located above the emitter region and above the first opening. a step of leaving the second silicon oxide film deposited on other parts and side surfaces of the semiconductor film; forming a silicon nitride film to be deposited on the first and second silicon oxide films, and converting the silicon nitride film to be deposited on the upper surface of the semiconductor film within the second opening into an oxide by anodic oxidation; and leaving the silicon nitride film on the entire surface of the first and second silicon oxide films as a silicon nitride film, and selectively only the portion of the silicon nitride film that has been converted into an oxide film. A method for manufacturing a semiconductor device, comprising the steps of: removing and exposing the part of the upper surface of the semiconductor film; and then applying an emitter electrode to the exposed part of the upper surface of the semiconductor film. be.

According to the present invention, when the silicon nitride film is anodized, the underlying polycrystalline silicon film is also converted to oxide to some extent, but there is still a sufficient amount of the highly concentrated polycrystalline silicon film remaining. A highly reliable, high-performance semiconductor device with a fine pattern with shallow junctions can be realized without any significant influence on the characteristics of the conventional semiconductor device.

The polycrystalline silicon semiconductor film of the present invention constitutes a part of the emitter electrode, and has the effect of preventing alloy spikes of aluminum onto the silicon substrate. Furthermore, the present invention has the effect of preventing concentration changes in the emitter region.

Next, the present invention will be explained by examples. Figure 1a
1 to 1k are cross-sectional views showing main manufacturing steps when the present invention is applied to manufacturing a bipolar semiconductor device. First, P is applied to an N-type silicon substrate 11.
A base region 12 of the mold is formed, and a silicon oxide film 13 is deposited on the surface of the substrate. The silicon oxide film 1
3 is suitably made to a thickness of about 2000 Å by thermal oxidation (Fig. 1a).

Next, using the photoresist film 14 as a mask,
The silicon oxide film 13 is selectively removed using a buffered hydrofluoric acid solution to form an opening that reaches the P-type base region 12 (FIG. 1b).

Next, polycrystalline silicon 15 is grown on the silicon oxide film 13 and the opening (FIG. 1c),
A silicon oxide film 16 is formed on the polycrystalline silicon 15.
(Fig. 1d). The polycrystalline silicon 15 has a thickness of about 4000 Å, and the silicon oxide film 16 is
It is appropriate to make the film thickness about 500 Å by thermal oxidation.

Next, using the photoresist film 17 as a mask,
The silicon oxide film 16 is selectively removed using a buffered hydrofluoric acid solution. Furthermore, a photoresist film 17
Then, using the silicon oxide film 16 as a mask, the polycrystalline silicon 15 is selectively removed.
When removing it, it is appropriate to use a mixed solution of hydrofluoric acid, iodine-containing glacial acetic acid, and nitric acid (Figure 1e).

Next, after removing the silicon oxide film with a buffered hydrofluoric acid solution, phosphorus is diffused from above the polycrystalline silicon 15 to form an emitter region 18 in the base region 12 through the opening. Figure 1 f).

Next, a silicon oxide film 19 is deposited on the polycrystalline silicon 15 (FIG. 1g), and the silicon oxide film 19 is further coated using a buffered hydrofluoric acid solution using the photoresist film 20 as a mask. openings selectively reaching the polycrystalline silicon 15 and the base region 12 (FIG. 1h). Next, the photoresist film 20 is removed. Thereafter, a silicon nitride film 21 is deposited over the entire surface of the substrate. The appropriate thickness of the silicon nitride film is approximately 300 Å (FIG. 1i).

Next, when the substrate is anodized, only the silicon nitride film deposited on the opening is converted into a silicon oxide film. At this time, the silicon nitride film in the portion other than the opening is insulated by the silicon oxide films 13 and 19, and therefore is not converted into a silicon oxide film. The silicon oxide film is removed using a buffered hydrofluoric acid solution to form an opening that reaches the polycrystalline silicon 15 and the base region 12 in the semiconductor substrate (FIG. 1j).

Next, a metal electrode 22 made of aluminum or the like is selectively provided to cover the opening and ohmically connect to the base region 12 and emitter region 18 to complete the formation of the transistor element (FIG. 1k).

As explained in the above embodiment, the present invention forms polycrystalline silicon to cover the openings reaching the emitter region 18 before anodizing the silicon nitride film and converting it into a silicon oxide film. ing. For this reason, when the silicon nitride film is anodized and converted into a silicon oxide film, which was a drawback of the conventional method, a portion of the emitter region 18 that is not covered with the silicon oxide film 13 is also anodized, and the silicon When the silicon oxide film converted into the nitride film is removed using a buffered hydrofluoric acid solution, a portion of the emitter region 18 of the semiconductor substrate is not removed. This makes it possible to manufacture a highly reliable semiconductor device with a shallow junction in which the semiconductor surface is inactivated with a silicon nitride film, without any significant effect on the characteristics of the semiconductor device. Furthermore, according to the present invention, since the polycrystalline silicon semiconductor film constitutes a part of the emitter electrode, there is no possibility that the transistor yield will be reduced due to a reduction in breakdown voltage due to alloy spikes.

In addition, in the example, an NPN transistor was explained, but by changing the conductivity type, a PNP
It can also be applied to transistors. Also, similarly MOS
The present invention can also be applied to elements such as type transistor diodes and resistors, and can also be applied to integrated circuit devices including these elements.

[Brief explanation of the drawing]

FIGS. 1a to 1k are cross-sectional views showing main manufacturing steps in manufacturing a bipolar semiconductor device according to an embodiment of the present invention. In the figure, 11...silicon substrate, 12
... Base region, 13, 16, 19 ... Silicon oxide film, 14, 17, 20 ... Photoresist film, 15 ... Polycrystalline silicon, 18 ... Emitter region, 21 ... Silicon nitride film, 22 ... ...It is a metal electrode.

Claims (1)

[Claims] 1. Forming a first opening selectively reaching the base region in a first silicon oxide film covering one main surface of a semiconductor substrate of one conductivity type on which a base region of an opposite conductivity type is formed; selectively forming a polycrystalline silicon semiconductor film on the first silicon oxide film in and around the first opening; and forming a semiconductor film of one conductivity type through the semiconductor film and the first opening. forming an emitter region of one conductivity type in the base region by introducing impurities into the semiconductor substrate; covering the semiconductor film with a second silicon oxide film; A second hole is formed in the oxide film, reaching a part of the upper surface of the semiconductor film, and being located above the emitter region and above the first opening.
forming an opening, leaving the second silicon oxide film deposited on other parts of the top surface and side surfaces, and exposing the semiconductor film in the second opening. forming a silicon nitride film on a portion of the upper surface and covering the first and second silicon oxide films, and depositing it on the upper surface of the semiconductor film within the second opening by anodic oxidation; converting the silicon nitride film into an oxide, and converting the first and second silicon nitride films into oxides;
A process of leaving the silicon nitride film on the entire surface of the silicon oxide film as a silicon nitride film, and selectively removing only the portion of the silicon nitride film that has been converted to oxide, and removing the silicon nitride film on the entire surface of the semiconductor film. A method for manufacturing a semiconductor device, comprising the steps of: exposing the part; and then depositing an emitter electrode on the exposed part of the upper surface of the semiconductor film.