JPH0722138B2 - Method for manufacturing semiconductor device - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device, and more particularly to improvement of a step of forming a p-type layer on the surface of a silicon layer.

[Technical background of the invention and its problems]

Currently, most of the impurities are introduced into semiconductor devices by the ion implantation method. The ion implantation method is excellent in that the amount of impurities to be introduced can be electrically controlled accurately.

However, there are some problems in forming a diffusion layer by ion implantation in a semiconductor device in which the element is further miniaturized. In FIG. 1, if the acceleration energy is lowered to form an extremely shallow diffusion layer, the so-called channeling effect becomes remarkable. This is because the influence of the channeling effect is not so obvious when ion implantation is performed with a large acceleration energy to form a diffusion layer which is deeper than a certain degree, whereas the influence is largely shown when a shallow diffusion layer is obtained. Second, the ion-implanted impurities need to be activated by heat treatment, but a temperature higher than a certain level is required for sufficient activation, and the impurities are re-diffused by this heat treatment. No shallow diffusion layer can be obtained. Thirdly, it is difficult to ion-implant the inclined surface. For example, in a MOS dynamic RAM or the like, in order to increase the capacity of a memory capacitor, it is proposed to dig a groove in a substrate and use the side wall to form a capacitor. Ion implantation becomes more difficult as the side wall surface becomes closer to vertical.

[Object of the Invention]

The present invention has been made in view of the above points, and an object thereof is to provide a method for manufacturing a semiconductor device including a step of forming a shallow p-type layer in a silicon layer with good controllability.

[Outline of Invention]

According to the present invention, in a method of manufacturing a semiconductor device having a step of forming a p-type layer on a silicon layer of a substrate, the step of forming the p-type layer includes depositing a boron film on the surface of the silicon layer via an oxide film. And a heat treatment to react the boron film and the oxide film with each other.
A first heat treatment step for forming a glass film;
The method further comprises a step of removing the boron film remaining on the silicate glass film, and a second heat treatment step of performing heat treatment to solid-phase diffuse boron from the boron silicate glass film into the silicon layer. To do.

Here, the first heat treatment step is performed in a vacuum or an inert gas atmosphere at 800 to 1100 ° C., and the second heat treatment step is performed in a vacuum or an inert gas atmosphere at 800 to 11 ° C.
It is desirable to be performed at 00 ° C.

〔The invention's effect〕

When the BSG film is formed by the method of the present invention, as will be clarified later by data, when the thickness of the boro-base film formed on the oxide film is more than a certain level, the boron concentration in the BSG film does not depend on the film thickness. Furthermore, since the boron film remaining on the boron-silicate glass film after the first heat treatment is removed constantly, an extremely shallow p-type layer is formed with good controllability by utilizing solid phase diffusion from this BSG film. can do. Further, since the method of the present invention utilizes solid phase diffusion,
With the ion implantation method, a shallow p-type layer can be easily formed even on an inclined surface where it is difficult to introduce impurities. Therefore, the present invention can be applied to various semiconductor devices in which the element is further miniaturized, and a great effect can be obtained.

Example of Invention

 Embodiments of the present invention will be described below with reference to the drawings.

1 (a) to 1 (d) show a manufacturing process of an embodiment in which the present invention is applied to a MOS type semiconductor device. A field insulating film 2 is formed on an n-type silicon substrate 1 by a known process, a thermal oxide film 3 serving as a gate insulating film is formed in an element formation region, and a gate electrode 4 made of a polycrystalline silicon film is formed thereon. ((A)). After that, the gate electrode 4 is covered with an oxide film, an oxide film 5 by CVD is selectively formed on the side wall of the gate electrode to a predetermined thickness, and a boron film 6 of 100 Å or more is deposited on the entire surface by a sputter deposition method ((b)). ). Then, heat treatment is performed at 900 ° C. for 30 minutes in an argon atmosphere (first heat treatment step) to react the boron with the oxide film to form the BSG film 7, and then the boron film remaining on the BSG film 7 is treated with fluorine. Removed by gas phase etching in plasma containing, and again in argon atmosphere
Heat treatment at 900 ℃ for 30 minutes (second heat treatment step), BSG
Boron is diffused from the film 7 into the substrate 1 to form p-type layers 8 and 9 which will be source and drain regions ((c)). Then, after that, the BSG film 7 is removed by etching with a hydrofluoric acid solution, the entire surface is covered with a CVD oxide film 10, a contact hole is formed, and Al is formed.
The source and drain ohmic electrodes 11 and 12 are formed by vapor deposition and patterning of the film ((d)).

According to this embodiment, the p-type layers 8 and 9 to be the source and drain regions can be formed with an extremely shallow diffusion depth with good controllability.

The fact that a shallow p-type layer can be formed with good controllability according to the present invention will be clarified below based on specific experimental data.

FIG. 2 shows the results of measuring the relationship between the boron film thickness and the surface resistance of the obtained p-type layer. Experiment 50 on a silicon substrate
A Å thermal oxide film was formed, and a boron film having a film thickness selected in the range of 10 to 500 Å was sputter-deposited on the oxide film to prepare a sample. First, a heat treatment at 900 ° C. for 30 minutes was applied to these samples to form a BSG film. Then, the unreacted boron film is removed by etching in plasma containing fluorine, and heat treatment is again performed in an argon atmosphere at 900 ° C for 30 minutes, and then BS is added with a hydrofluoric acid solution.
The surface resistance of the silicon substrate was measured after removing the G film.

As is clear from FIG. 2, the surface resistance value is almost constant regardless of the boron film thickness when the boron film thickness is 50 Å or more, particularly 100 Å or more. This is because the BSG film is formed by the reaction between metallic boron and the thermal oxide film of silicon, but the boron concentration of the obtained BSG film does not depend on the film thickness if the boron film thickness is a certain value or more. It is shown that the excess boron is kept at a constant value and remains on the BSG film as it is, and the residual boron is removed by vapor phase etching. This fact suggests that poor coverage of the boron film causes almost no problem, and for example, the p-type layer can be formed on the inclined surface of the silicon substrate as well as on the flat surface. .

Fig. 3 shows the relationship between the oxide film thickness and the surface resistance of the p-type layer by BSG.
The heat treatment temperature for chemical conversion is shown as a parameter.
The experiment was performed in the same steps as the basic previous experiment. That is, prepare a sample in which a thermal oxide film is formed on a silicon substrate in the range of 50 to 200 Å, deposit a boron film at 200 Å on each sample, and 1000 ℃, 950 ℃, 9 ℃ for each sample in an argon atmosphere.
A heat treatment was performed at 00 ° C. for 30 minutes to form a BSG film. Then, as in the previous experiment, residual boron was removed from each sample, heat treatment was again performed at 900 ° C. for 30 minutes in an argon atmosphere, and then the BSG film was removed to measure the surface resistance.

From this experimental data, the boron concentration in the BSG film changes depending on the heat treatment temperature for BSG formation. However, if the heat treatment temperature is set to a constant value, the sheet resistance of the p-type layer formed is almost the same as the oxide film thickness. I know that it is not affected.

FIG. 4 shows the results of comparing the boron distribution of the p-type layer obtained by the present invention with that by the ion implantation method.
The data of the present invention is for the sample having a boron film thickness of 200 Å shown in FIG. The data obtained by the ion implantation method is the case where ion implantation was performed at an acceleration energy of 200 keV and a dose amount of 5 × 10 ¹⁵ / cm ² , and heat treatment was performed at 900 ° C. for 60 minutes.

From this result, it is clear that the method of the present invention can provide a shallow boron diffusion layer.

As described above, according to the present invention, an extremely shallow p
The type diffusion layer can be formed with good controllability, and miniaturization and high performance of elements such as MOS integrated circuits can be achieved. Further, since it is possible to easily form the p-type diffusion layer on the inclined surface, which is difficult by the ion implantation method, it is expected to be greatly effective when applied to, for example, a trench digging type MOS dynamic RAM.

Although all the heat treatments are performed in an argon atmosphere in the above, the same effect can be obtained by performing the heat treatments in another inert gas atmosphere or in a vacuum.

[Brief description of drawings]

1 (a) to 1 (d) are sectional views showing a manufacturing process of a MOS type semiconductor device according to an embodiment of the present invention, and FIG. 2 is a sheet of a boron film thickness and a p-type layer obtained by the method of the present invention. Data showing the relation of resistance, FIG. 3 is data showing the relation between the oxide film thickness and the sheet resistance of the obtained p-type layer, and FIG. 4 is showing the same boron concentration distribution as that obtained by the ion implantation method. Is. 1 ... n-type silicon substrate, 2 ... field insulating film, 3
... thermal oxide film, 4 ... gate electrode, 5 ... CVD oxide film,
6 ... Boron film, 7 ... BSG film, 8, 9 ... P-type layer, 10 ...
CVD oxide film, 11,12 ... Ohmic electrode.

Claims (2)

[Claims] 1. A method of manufacturing a semiconductor device, comprising a step of forming a p-type layer on a silicon layer of a substrate, wherein the step of forming the p-type layer covers the surface of the silicon layer with a boron film via an oxide film. And a first heat treatment step of reacting the boron film with the oxide film by heat treatment to form a boron-silicate glass film, and boron remaining on the boron-silicate glass film. The step of removing the film and the heat treatment are performed to remove the boron silicate.
A second heat treatment step of solid-phase diffusing boron from a glass film to the silicon layer, the method for manufacturing a semiconductor device. 2. The first heat treatment step is performed at 800 to 1100 ° C. in a vacuum or an inert gas atmosphere, and the second heat treatment step is performed.
The heat treatment process is performed in vacuum or in an inert gas atmosphere at 800
The method for manufacturing a semiconductor device according to claim 1, wherein the method is performed at ˜1100 ° C.