JPS627703B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a semiconductor device.

Conventionally, the electrode wiring structure of semiconductor devices is a structure in which metal is deposited directly on the semiconductor substrate, with relatively deep PN
It was effective for joining. In recent years, advances in semiconductor technology have made it possible to fabricate very shallow PN junctions (shallow junction type).
When forming electrodes on a semiconductor element having a junction,
When electrode metal is directly vapor-deposited and heat treated, accidents often occur in which the electrode metal diffuses into the semiconductor or penetrates through the joint. For this reason, the impurity diffusion layer changes, resulting in a change in layer resistance and short-circuiting of the junction.

In order to compensate for these drawbacks, an electrode wiring structure as shown in FIG. 1 has recently been proposed. That is, the impurity diffusion layer 3 is formed using the oxide film 2 selectively formed on one surface of the silicon substrate 1 as a mask. Furthermore, an oxide film 4 is formed leaving a part of the impurity diffusion layer 3, a polycrystalline silicon layer is grown on the entire surface, and after diffusing an impurity having the same conductivity type as the impurity diffusion layer 3, thermal oxidation is performed to form a polycrystalline silicon layer. silicon layer 5
Then, electrical continuity between the impurity diffusion layer 3 and the oxide film 6 is formed. After that, the oxide film 6 is opened,
A metal electrode 7 is formed by vapor deposition. That is, by sandwiching the above-mentioned polycrystalline silicon 5 between the silicon substrate and the metal electrode, it is intended to prevent the diffusion of metal into silicon, but even if it can be prevented to some extent, it is not perfect. Electrical instability such as breakdown voltage and leakage often occurred in the equipment.

In view of the above-mentioned drawbacks, the present invention provides an electrode wiring structure that can substantially prevent the diffusion of electrode metal into the semiconductor, has high reliability, is free from disconnection of the wiring, and has a predetermined insulation structure in the field area. An object of the present invention is to provide a semiconductor device suitable for an integrated circuit that can be separated.

The present invention is characterized by a first insulating film provided on one main surface of a semiconductor substrate, a first opening provided in the first insulating film, and a first insulating film provided in the semiconductor substrate within the first opening. a second insulating film extending from within the first opening onto the first insulating film; and a second insulating film provided in a portion of the second insulating film within the first opening. a second opening; a semiconductor layer having the same conductivity type as the impurity region and connected to the impurity region through the second opening and extending over the second insulating film; and a metal layer connected to the separated portions of the semiconductor layer. Preferably, substantially the entire surface of this semiconductor layer is covered with an insulating film, particularly a thermal oxide film.

Hereinafter, the present invention will be explained with reference to the drawings.

FIG. 2 is a sectional view showing an embodiment of the present invention. Impurity layer 3 is formed using oxide film 2 selectively formed on one surface of silicon substrate 1 as a mask. Further, an oxide film 4 is formed leaving a part of the impurity layer 3, and a semiconductor layer, such as a polycrystalline silicon layer, is grown over the entire surface and connected to the impurity region 3 at an intermediate portion thereof. For this polycrystalline silicon layer,
After diffusing an impurity of the same conductivity type as impurity layer 3, thermal oxidation is performed to obtain electrical continuity between polycrystalline silicon layer 5 and impurity layer 3 as a low resistance layer, and to form oxide film 6. Thereafter, the oxide film and the polycrystalline silicon layer are selectively etched away using a photo-etching technique, leaving the polycrystalline silicon layer 5 in a predetermined shape and the thermal oxide film 6 thereon. A thermal oxide film is also formed on the side surface of this polycrystalline silicon layer 5 by the subsequent high-temperature thermal oxidation. Thereafter, a hole is formed in the oxide film 6 at a distance of several microns or more in the lateral direction from the connection between the polycrystalline silicon layer 5 and the impurity layer 3 using a photo-etching technique, and a metal electrode 7 is formed by vapor deposition, and a predetermined shape is formed. get. By alloying the metal 7, the contact with the polycrystalline silicon 5 is strengthened.

As for the position of the metal electrode 7 mentioned above, the connection between the polycrystalline silicon 5 and the impurity layer 3 and the connection between the polycrystalline silicon 5 and the metal electrode 7 should be separated by at least several microns so that they do not overlap during heat treatment. It is based on the principle that metal diffusion can be prevented.

The first effect of the present invention is that the connection between the metal electrode and polycrystalline silicon is separated from the connection between the impurity layer and the metal electrode and the semiconductor substrate have a structure in which an oxide film is sandwiched between them. In some cases, it is possible to completely prevent metal from diffusing into the silicon substrate.

In addition, the second effect of the present invention is that since polycrystalline silicon is formed on the oxide film, the contact area between the polycrystalline silicon and the electrode metal can be large, and there are fewer breaks in the electrode metal, making it more electrically reliable. An electrode wiring structure with excellent contact properties and stability can be obtained. When this semiconductor layer is covered with a thermal oxide film, reliability is further improved. That is, the thermal oxide film has better film quality and adhesion to the semiconductor layer than an oxide film grown in a vapor phase, and is also easier to form.

Further, a third effect of the present invention is that the first insulating film and the second insulating film are used together. Thereby, the first insulating film can be used, for example, as a mask for forming an impurity region, and its film thickness can be determined so as to obtain a predetermined high threshold voltage in the field region. On the other hand, by using the second insulating film, it is possible to determine the connection position with the semiconductor layer at a predetermined location in the impurity region, and by considering the material of the second insulating film, the corner of the stepped part of the insulating film can be made smooth. This makes it possible to eliminate disconnections in the semiconductor layer.

Although the embodiments have been described using a silicon substrate, similar effects can be obtained even if other semiconductors are used.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the electrode wiring structure of a conventional semiconductor element, and FIG. 2 is a sectional view showing the electrode wiring structure of a semiconductor element according to the present invention. In the figure, 1 is a silicon substrate, 2 is an oxide film, 3 is an impurity layer (region), 4 is an oxide film, 5 is a polycrystalline silicon layer containing an impurity of the same conductivity type as the impurity diffusion layer 3, and 6 is an oxide film. The film 7 is a metal for electrodes.

Claims (1)

[Claims] 1. A first insulating film provided on one main surface of a semiconductor substrate, a first opening provided in the first insulating film, and an impurity region provided in the semiconductor substrate within the first opening. , a second insulating film deposited on the semiconductor substrate in the first opening and extending over the first insulating film, and provided at a location of the second insulating film in the first opening. a second opening made of the second insulating film and located within the first opening; forming an insulating layer having a second portion located outside the first opening; The second step is formed by a first portion and a second portion of the insulating layer, and has the same conductivity type as the impurity region, and enters the impurity region through the second opening. A connected semiconductor layer is deposited from the first step onto the top surface of the first portion of the insulating layer and from the second step onto the top surface of the second portion of the insulating layer. the semiconductor layer extends from the first
1. A semiconductor device, wherein the semiconductor device is connected to a metal layer at a second portion of the insulating layer formed of the first and second insulating films outside the opening of the insulating layer.