JPH09148263A - Method for manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method capable of introducing impurities to a gate and preventing a diffusion of impurities unrequired for a thin film such as gate insulation film by later heat treatment. SOLUTION: On a thin film 20 on a semiconductor substrate 10, a thin film 200 of a semiconductive amorphous, a thin film 210 of an insulative substance and a thin film 220 of a semiconductive polycrystal are successively stacked and formed, and thereafter impurities are implanted to the thin film 220 of the semiconductive polycrystal. Further, the impurities are diffused to the thin film 200 of the semiconductive amorphous by heat treatment, and then an abnormal diffusion is prevented by the thin film 210 of the insulative substance having a film thickness of 40 angstroms or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the technical field of introducing impurities near the surface of a solid, and more particularly to the introduction of impurities in the field of semiconductor device manufacturing.

[0002]

2. Description of the Related Art In the following, as a conventional technology, for example, MO
A method of introducing impurities into the semiconductor substrate having the S structure will be described with reference to the drawings. FIG. 2 is a sectional process view showing a conventional method of introducing impurities into a semiconductor substrate.

First, as shown in FIG. 2A, a thin film 20 is formed on the plane of the semiconductor substrate 10. Here, in the above description, a semiconductor substrate and a thin film are described.
When applied to the formation of an S-type semiconductor element, the semiconductor substrate 10 is a silicon single crystal and the thin film 20 is a silicon oxide. Then, a semiconductor polycrystal thin film 30 is deposited on the above thin film 20. Then, patterning is performed by etching to form a desired pattern composed of the semiconductor polycrystalline thin film 30 and the thin film 20, as shown in FIG.

Next, the semiconductor substrate 10 having the above structure.
An arbitrary substance such as an impurity is introduced into. When introducing impurities, generally, the semiconductor substrate 10 is irradiated with ions 50 containing a desired substance as shown in FIG. 2C, or
As shown in FIG. 2D, the semiconductor substrate 10 is exposed to the gas 60 or the plasma 70. In addition, in FIG. 2C, the portion surrounded by a circle is a gate electrode in the case of a MOS transistor.

Therefore, hereinafter, in FIG.
Further description will be made with reference to the drawings showing a state in which the portion surrounded by is enlarged. 2E to 2G are enlarged views of FIG. 2C.

As shown in FIG. 2E, the impurity substance introduced in the impurity introducing step is a semiconductor polycrystalline thin film 30.
A high-concentration impurity layer 90 is formed near the upper surface of the. Thereafter, the impurity layer 90 is generally thermally diffused into the semiconductor polycrystalline thin film 30. At that time, as shown in FIGS. Since it diffuses at a high speed along with, it reaches the boundary region, that is, the interface between the semiconductor polycrystalline thin film 30 and the thin film 20 in a time zone of rapid thermal diffusion, and the high concentration layer 110 is formed in this vicinity.

[0007]

First of all, as a result, when the diffusion at grain boundaries becomes dominant, it is basically very difficult to control the diffusion. Further, the high-concentration layer formed near the interface in an early time zone serves as a source of diffusion into the silicon oxide film during the subsequent thermal diffusion step,
A substance that should not be diffused (for example, boron) is taken into the oxide film, which causes a problem of deteriorating the characteristics of the MOS semiconductor device.

The cause of this problem is that the diffusion of the substance in the polycrystal is accelerated by orders of magnitude at the grain boundary. It is difficult to predict the result because it behaves significantly different from diffusion in crystals, which has been widely studied, and largely depends on the polycrystal formation. That is, the substance diffuses through the grain boundary before the substance enters the crystal grain where the substance is originally desired to diffuse. As a result, there arises a problem that the impurities are rapidly diffused downward, and due to another heat treatment performed thereafter, the impurities are diffused into a region where the impurities should not originally be diffused.

In view of the above problems, it is an object of the present invention to provide a method of manufacturing a semiconductor device, which can perform impurity diffusion with good controllability and prevent diffusion of impurities into unnecessary regions. To do.

[0010]

In order to achieve the above object, the present invention is caused by the fact that the impurity layer plays a role as an almost limitless diffusion source of impurities. The thin film functioning as above is provided in the semiconductor polycrystalline thin film.

By using the above-mentioned means, it is possible to control the early diffusion of impurities in the thin film, and as a result, it is possible to uniformly diffuse and reduce the adverse effect on the lower thin film. .

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the step of introducing an impurity into a semiconductor substrate including, for example, a MOS type semiconductor element, and then diffusing the impurity, a structure of a semiconductor device to which impurities are introduced is formed as follows. The impurity introduction method described here is performed by, for example, implanting boron ions at a dose of 5E1 at 2 keV.
Injecting at 5 ions / cm2 is more specific. More specifically, the semiconductor substrate is placed in a vacuum chamber, a gas containing B2H6 is introduced into the vacuum chamber at a vacuum degree of about 5E-4 Torr, and if necessary. Plasma is generated by a technique such as so-called IPC, RF, ECR, helicon, etc.

A method of manufacturing a semiconductor device according to an embodiment of the present invention will be described below with reference to FIG.

First, as shown in FIG. 1A, a thin film 20 is formed on the plane of the semiconductor substrate 10. Here, when forming a MOS type semiconductor element, the semiconductor substrate 10 is, for example, a silicon single crystal, and the thin film 20 is a silicon oxide. In this case, a 60 angstrom silicon oxide film can be formed by inserting a silicon single crystal gas into an electric furnace and performing heat treatment at 900 degrees while introducing hydrogen and oxygen.

After that, a semiconductor amorphous thin film 200 is deposited on the thin film 20. This semiconductor amorphous thin film 200 can be formed by the CVD method. Furthermore, a thin film 21 of an insulating material is formed by using the PVD method.
0 is deposited to 30 Å, and then the second semiconductor polycrystalline thin film 220 is deposited to 500 Å by the CVD method.

Next, as shown in FIG. 1B, a desired pattern including the thin film 20, the semiconductor amorphous thin film 20, the insulating thin film 210, and the second semiconductor 200 is formed by etching or the like. Then, an arbitrary substance such as an impurity is introduced into the semiconductor substrate 10 having the above structure.

Therefore, the method of introducing the above impurities will be described in detail below with reference to FIG. When introducing impurities, generally, as shown in FIG. 1C, the semiconductor substrate 10 is irradiated with ions 50 containing a desired substance.
Here, a normal ion implanter is used to implant boron ions at a dose of 5E15 ions / cm 2 at 2 keV. Instead of the method of introducing impurities shown in FIG. 1C, the semiconductor substrate 10 may be exposed to the gas 60 or the plasma 70 as shown in FIG. 1D. Here, the semiconductor substrate 10 is installed in a vacuum chamber, a gas containing B2H6 is introduced in a state of a vacuum degree of about 5E-4 Torr, and so-called IPC, RF, EC are added if necessary.
Plasma is generated by a method such as R or helicon to carry out this step.

At this time, the portion circled in FIG. 1 (c) is a gate electrode in MOS,
An enlarged view of this portion is shown in FIGS.
The substance introduced in the impurity introduction step is formed as a high-concentration impurity layer 90 near the upper portion of the semiconductor polycrystal thin film 30, as shown in FIG. Generally, the impurity layer 90 is thermally diffused into the semiconductor polycrystalline thin film 30. At this time, first, the impurity layer 90 is diffused at high speed in the second semiconductor polycrystalline thin film 220. Further, the material to be further diffused is limited in diffusion and limited by the thin film 210 of the insulating material. During the subsequent heat treatment, it gradually diffuses into the lower thin film, for example, the thin film 210 of the insulating material.

As described above, according to the present invention, since the insulating thin film is formed between the semiconductor amorphous thin film 200 and the second semiconductor thin film, as a result, the second semiconductor polycrystalline thin film 220 is formed. A slightly high concentration impurity layer 230
On the other hand, a slightly low concentration impurity layer 240 is formed in the lower semiconductor amorphous thin film 200.

According to the embodiment of the present invention, by interposing an insulating thin film of 30 angstrom between two semiconductor layers, it is possible to prevent impurities from diffusing to some extent. The diffusion of impurities can be suppressed. Here, in the embodiment of the present invention, the thickness of the insulating thin film is set to 30 angstroms, but the same effect can be obtained if the thickness is 40 angstroms or less.

[0021]

As described above, according to the present invention, when forming a MOS type semiconductor element, for example, low energy impurities are introduced and diffused,
The process can be performed extremely accurately.

[Brief description of the drawings]

FIG. 1 is a process sectional view of a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a process sectional view of a conventional semiconductor device.

[Explanation of symbols]

 10 Semiconductor Substrate 20 Thin Film 30 Semiconductor Polycrystalline Thin Film 40 Impurity 50 Ion 60 Gas 70 Plasma 80 Gate Electrode 90 Impurity Layer 100 Grain Boundary 110 High Concentration Layer 200 Semiconductor Amorphous Thin Film 210 Insulating Material Thin Film 220 Second Semiconductor Polycrystal Thin film 230 High concentration impurity layer 240 Low concentration impurity layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroaki Nakaoka 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] 1. A step of forming a thin film on a semiconductor substrate, a step of forming a first semiconductor layer on the thin film, and a step of forming an insulating thin film having a film thickness of less than 40 angstrom on the semiconductor layer. And a step of forming a second semiconductor layer on the insulating thin film, and using the resist as a mask to form the thin film, the first semiconductor layer, the insulating thin film and the second semiconductor layer on the semiconductor substrate. A step of patterning,
Plasma irradiation or ion irradiation is performed from the patterned second semiconductor layer side to form an impurity layer in the second semiconductor layer, and then heat treatment is performed to form an impurity layer in the second semiconductor layer. And a step of diffusing a part of the impurities into the first semiconductor layer through the insulating thin film.