JPS6367333B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a method of forming a dielectric film made of tantalum oxide (Ta ₂ O ₅ ) among methods of manufacturing a semiconductor device.

(b) Prior Art and Problems Semiconductor integrated circuits (ICs) are becoming increasingly dense and highly integrated, and LSIs and VLSIs are being developed and manufactured. Accordingly, the elements constituting the IC have also become extremely miniaturized; for example, one MOS type semiconductor element is housed within an area of about 10 square microns.

In such semiconductor integrated circuits, semiconductor memory devices in particular have become highly integrated, such as 64KRAM and more.
256KRAM was created, and these are composed of memory cells with a simple structure in which one MOS type semiconductor element and one capacitor (capacitive element) are combined.

An example of a cross-sectional view of such a memory cell is shown in FIG. 1. This is called a stacked one-transistor memory, and has a structure in which a capacitor 2 is stacked on a MOS semiconductor element 1, and the capacitor 2 is made of a dielectric material. It has a structure in which a membrane 3 is interposed between electrodes 4 and 5. It goes without saying that one-transistor memory cells of other structures also require such a dielectric film.

By the way, in the past, silicon dioxide (SiO ₂ ) films were generally used as such dielectric films, and sometimes silicon nitride (Si ₃ N ₄ ) was also used, but as mentioned above, the overall size has been miniaturized. In order to maintain the same capacitance (capacitance value), the smaller the area, the thinner the film must be. However, if the film becomes too thin, it becomes difficult to maintain insulation properties, and from this point of view, tantalum oxide films, which have a higher dielectric constant (ε) than silicon dioxide films, are attracting attention. That is, if the dielectric constant becomes large, the capacitance will not change even if the film thickness is increased. It is known that the dielectric constant of the tantalum oxide film is extremely large, at 27, while that of the silicon dioxide film is 3.8 and that of the silicon nitride film is 6.

However, compared to silicon dioxide films, tantalum oxide films have a higher leakage current and poor insulation properties, so they are still not widely used.

(c) Object of the Invention The present invention proposes a method of forming such a tantalum oxide film to improve its insulation properties.

(d) Structure of the invention The object is to be achieved by a manufacturing method that includes a step of implanting oxygen molecular ions or oxygen atomic ions into a tantalum oxide film formed on a substrate to form an amorphous tantalum oxide film. I can do it.

(e) Embodiment of the invention Hereinafter, an embodiment will be described in detail with reference to the drawings. 2 and 3 show cross-sectional views in the order of steps, and FIG. 2 shows a polycrystalline silicon film 12 (one electrode of a capacitor) deposited on a semiconductor substrate 10 with a partial insulating film 11 interposed therebetween. This is a diagram in which a tantalum film 13 having a thickness of 100 to 200 Å is deposited thereon by a sputtering method or a vapor phase growth method.

Next, as shown in FIG. 3, the tantalum film 13 is changed into a tantalum oxide film 14 by processing in an oxidizing gas flow at 500 to 600°C. In addition, the tantalum oxide film 14 with a thickness of 200 to 500 Å can be directly formed without going through the process shown in FIG.
may be coated with This can be formed by reactive sputtering of a tantalum film using oxygen gas.

Next, as shown in FIG. 4, a tantalum oxide film 1 is formed.
Oxygen molecule ions (O ₂ ⁺ ) are injected into 4 at low acceleration energy of 1 to 20 KeV. The injection volume is 10 ¹⁶ ~
10 ¹⁸ /cm ² , and implantation is performed using a low-acceleration, high-current ion implanter. When excessive oxygen is implanted in this manner, even if the tantalum oxide (Ta ₂ O ₅ ) crystal is destroyed, it becomes amorphous, and a dense film quality that is difficult to crystallize even during high-temperature annealing can be obtained.
In addition, the degree of insulation is significantly improved as it approaches that of a silicon dioxide film. This is because in the past, unbonded tantalum existed and crystallized during heat treatment, which caused a decrease in insulation properties, but it is thought that this problem can be eliminated in the present invention.

Next, as shown in FIG. 5, a polycrystalline silicon film 15, which will become the other electrode, is deposited to complete the capacitor. In this way, it is possible to form a capacitor with good insulation using a tantalum oxide film with a good dielectric constant as a dielectric.

Further, the same effect can be achieved even if oxygen atomic ions (O ⁺ ) are implanted instead of implanting oxygen molecular ions (O ₂ ⁺ ). Further, it is necessary to uniformly implant the implant by changing the implant acceleration energy depending on the thickness of the tantalum oxide film.

(f) Effects of the invention As can be seen from the above explanation, according to the present invention, it is possible to use a capacitor using a tantalum oxide film with a good dielectric constant as a dielectric material, and the density can be increased.
This is useful for improving the characteristics and reliability of IC memory.

[Brief explanation of drawings]

FIG. 1 is an example of a cross-sectional view of a one-transistor memory cell, and FIGS. 2 to 5 are cross-sectional views of one embodiment of the present invention in the order of forming steps. In the figure, 1 is a MOS type semiconductor element, 2 is a capacitor, 3 is a dielectric film, 4 and 5 are electrodes, 10 is a semiconductor substrate, 11 is an insulating film, 12 and 15 are polycrystalline silicon films (electrodes), and 13 is a The tantalum film 14 indicates a tantalum oxide film.

Claims (1)

[Claims] 1. A method for manufacturing a semiconductor device, comprising the step of implanting oxygen molecular ions or oxygen atomic ions into a tantalum oxide film formed on a substrate to form an amorphous tantalum oxide film.