JPS60107838A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a film, leakage currents therefrom are little and dielectric strength thereof is high, by laminating and applying first and second insulating films on the surface of a semiconductor substrate, implanting accelerated ions to the second insulating film to bring the second insulating film to an amorphous state and changing the second insulating film to a compact film through heat treatment when a dielectric film having high relative permitivity in Ta2O5, TiO2, etc. is formed on the surface of the substrate. CONSTITUTION:An SiO2 film 2 and a Ta2O5 film 3 are laminated and applied on an Si substrate 1, and ions of Ar, O2, Ta, etc. are implanted to the film 3 to change the film 3 into a Ta2O5 film 31 having amorphous structure. The surface of the substrate 1 is also brought to an amorphous state at that time, but a change into the amorphous state is not at issue practically because the change is recovered in a subsequent heat treatment process. The film 31 is turned into a Ta2O5 film 35 having compact structure through heat treatment at 600-800 deg.C in an inert gas atmosphere or an oxidizing atmosphere. Accordingly, an electrode is formed on the film 35, and MOS capacitance is shaped.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides 'Ta205. The present invention relates to a method of forming a dielectric film with a high relative permittivity such as Tie2, and particularly relates to a method of forming a dielectric film with a low leakage current flowing through the film and a high dielectric strength.

In recent years, MO8 type semiconductor devices have been widely used, and their integration density is increasing year by year. Hitherto, densification has been achieved by making patterns finer. but,
In semiconductor devices such as dynamic and random access memories (DRAMs), miniaturization of patterns leads to a decrease in the amount of accumulated charge corresponding to signals, and memory malfunctions due to radiation such as alpha rays (N7 toe 2-). The problem is that this occurs. Therefore, it is necessary to take measures that do not reduce the amount of accumulated charge even if the pattern is made finer.

Conventionally, this problem has been dealt with by making the insulating film in the BMO8 capacitor part, which stores charge, thinner so that the capacitance value does not decrease. However, as the insulating film becomes thinner, the number of pinholes increases, making it impossible to obtain a sufficient withstand voltage, resulting in a low yield rate of 9, and there are limits to making the film thinner.

Usually, as a dielectric material that constitutes the insulating film of the capacitive part,
8i0. with a dielectric constant of 3.9. However, if a material with a high dielectric constant is used, it is possible to increase the capacitance even with the same electrode area, and therefore, it becomes possible to miniaturize the electrode. For Jin, we already have Ta2O,, Tie,
High dielectric materials such as The means for forming these films is, for example, Ta.

After depositing a metal material such as Ti in a vacuum, it is oxidized by heat treatment in an oxygen atmosphere or by anodic oxidation, or an insulating material such as Ta2O, TiO2 is deposited in a vacuum. It is formed by vapor deposition or deposition using a vapor phase growth method. However, films formed using these methods have not reached the stage where they can be put to practical use because a large amount of leakage current flows when a low voltage is applied.

The reason for this is thought to be that the formed insulating film has a polycrystalline structure, and leakage current flows through the grain boundaries. The inventor thought that leakage current could be reduced.

Based on this consideration, the present invention eliminates the drawbacks of low dielectric strength voltage and large leakage current of high dielectric constant insulating films formed by conventional methods in semiconductor devices, and provides means for realizing high-quality films. There is a particular thing. That is, the present invention provides a second insulating film on the surface of a semiconductor substrate or on the surface of a first insulating film provided on the semiconductor substrate,
Next, the second insulating film is made amorphous by irradiating the surface of the second insulating film with accelerated ions, and then heat treatment is performed to make the second insulating film amorphous. The present invention relates to a method of manufacturing a semiconductor device characterized by including a step of forming a dense film.

Hereinafter, the present invention will be explained in detail using examples.

FIGS. 1 to 3 are cross-sectional structural views for explaining the process, taking as an example the case where the present invention is applied to forming an MO8 type capacitor. In the figure, 1 is the semiconductor substrate, 2 is the first
3 indicates the second insulating film, and 4 indicates the ion flying direction. Hereinafter, a silicon substrate will be used as the semiconductor substrate l, a silicon substrate will be used as the first insulating film 2, and a silicon substrate will be used as the second insulating film 3.
As Ta, 0. .

The manufacturing process of an MO8 capacitor using a membrane will be explained step by step.

First, a Sin film 2 is formed on the surface of a silicon substrate 1, and then a 'ra, o film 3 is formed (Fig. 1). Although it is provided to prevent reaction with the substrate 1,
Since the dielectric constant is as small as 3.9, it is desirable that the film be thin in order to form a large MO8 capacitance, and the film thickness is preferably 50 to 100. Also, Ta, 0. The film 3 can be formed by, for example, depositing Ta in a vacuum and then heat-treating it in an oxygen atmosphere or anodizing it, or by depositing Ta in a vacuum.
A2O5 can be formed by vapor deposition in a vacuum or by vapor phase epitaxy, which can be freely selected.Of course, Ta, 0. The membrane 3 is also preferably thinner in order to obtain a large MO8 capacity, and the thickness of the membrane 3 is 200
It is preferable that the film thickness is about ~5008.
.

Film 3 is observed to have an amorphous structure according to X-ray analysis, but it is not completely amorphous from electrical property evaluation. By implanting ions into the Ta*O film 3, Ta, 0. Film 3 has an amorphous structure.
Since the film 3 is a thin film, the ion implantation is performed at an acceleration voltage of 10 to 50K, for example.
If ions are implanted at a dose of 10 to 10 eV under the condition, an amorphous film of sufficient quality will be formed. With the above ion implantation, the entire thickness direction of the Ta, Os film 3 becomes sufficiently amorphous. Ion implantation may be performed by changing the acceleration voltage as shown in FIG. At this time, the surface of the silicon substrate 1 is also made amorphous, but this does not pose a practical problem since the polycrystallinity is restored by heat treatment in a later step.

Also, Ta, 0. Ion implantation may be performed only in a portion of the tank 1 m by providing a mask film notch on the surface of the membrane 3 to serve as a mask for ion implantation. In the ion implantation, the Ta, 0. It is possible to make the film 3 amorphous, but in this case, forming an impurity region on the surface of the silicon substrate 10 is preferable since the present invention can be applied to a wide range of semiconductor devices with other structures. .

After the amorphous Ta, O. film 31 is formed, the amorphous Ta, O. The film 31 is changed to a Ta,05 film 35 with a dense structure (third
figure). Thereafter, an electrode is formed on the surface of the Ta20° film 35 having a dense structure, and an MO8 capacitor is formed.

When the amount of leakage current of the MOB capacitor formed using the present invention was investigated, the leakage current was reduced by about two orders of magnitude compared to the conventional method.
It was found that a sufficiently good film was formed. It is clear that this effect is due to the fact that the 'ra, o, film is once changed to a completely amorphous film. In the above explanation, the dielectric material is Ta, 0. Although it has been described that a film is formed, the present invention is based on Tie.

Dielectric materials such as MgO, Nb, O, or BaTiO
The present invention can be similarly applied to ferroelectric materials such as s.

[Brief explanation of the drawing]

1 to 3 are cross-sectional views of a semiconductor device at various steps for explaining an embodiment of the present invention. 1...
... Semiconductor substrate, 2... First insulating film, 3.
... second insulating film, 4 ... ion flying direction, 31 ... amorphous second insulating film,
35...Second insulating film with a dense structure.

Claims (1)

[Claims] A second insulating film is provided on the surface of the semiconductor substrate or the surface of the first insulating film provided on the semiconductor substrate, and then the second insulating film is
The second insulating film is made amorphous by irradiating the surface of the insulating film with accelerated ions, and then heat treatment is performed to make the second insulating film a dense film. 1. A method for manufacturing a semiconductor device, comprising the steps of: