JPS58134464A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a capacitor having large capacity density and small leakage current by superposing Ta2O5, Ta on an Si and oxidizing it to form a Ta2O5 film. CONSTITUTION:An N type polysilicon film 8 to becomes the electrode of the capacity of a memory cell by connecting to the N<+> type drain 6 of an FET is formed, a Ta2O5 9 is sputtered in approx. 10nm, and Ta film 10 is then sputtered in more than 50nm. It is then treated at approx. 800 deg.C in vacuum to improve the crystallinity of the film 10, oxidized to form a Ta2O5 film 11 together with the film 9, a polysilicon electrode 12 is attached, memory cells are individually isolated, and a capacitor is formed. The film 10 is oxidized in dry O2, but the Ta is not silicided to the polysilicon 8 due to the intermediary of the film 9, and the temperature and the time can be widely selected. When N2 is flowed to the trichloroethylene surface at 0 deg.C, introduced together with the O2 to a treating chamber and oxidized in an atmosphere including Cl2, it is effective to reduce the leakage current of the Ta2O5 formed of the Ta.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical field of the invention The present invention relates to semiconductor devices, 4! The present invention relates to a method for manufacturing a tantalum oxide film used as a dielectric of a capacitor such as a KMOS Guinaoch random access memory.

Background of the Technology A typical example of providing a capacitor element in a semiconductor integrated circuit is the MO8 Dyna Z Tsukundam Access Memory (hereinafter referred to as M08 RAM).

MOS RA
It is necessary that the capacitor M has as large a capacitance as possible.

1MO8RA to increase the capacitance of the capacitor
A method has been proposed to maximize the capacitor area by modifying the planar arrangement of M and further by adding multiple layers.Another method is to use silicon dioxide (810 , ) has a relative dielectric constant of 3
．． Although it is small at about 8, silicon nitride (8ゑ-N-) (as density 5~7), which has a larger dielectric constant than this, and an oxidation tank k (Tm, 0.) (L=20~ 2
It has been proposed to increase the capacitance density by using B) etc. as a dielectric. (C) Conventional technology and problems Silicon (St) such as a silicon substrate or a polycrystalline silicon layer provided on a substrate On the layer, tank # (TI)
When forming @ by sputtering method, electron beam method, etc., the temperature is much lower than the normal Ta silicidation reaction temperature, 50°C extreme or at most 1
Although the temperature does not rise to 00°C, a chemical reaction occurs between Ta and 81.

Furthermore, even when the Tdll formed on the S1 layer is heated to a temperature higher than the KTi film formation temperature for heat treatment or thermal oxidation, the silicidation reaction of Ti proceeds.

In this way, when a Ta film containing 8if is oxidized to a 10g Ta film by thermal oxidation or anodic oxidation, and this is used as a dielectric to form a capacitor, yc Tm, O, The leakage current is large compared to the case where a film is formed, and this becomes a particularly serious problem in applications where the purpose is to accumulate charge, such as in MOS RAM.

There is also a method of directly forming a KTag O@ film on the S& layer by sputtering or the like, but the Ta10B film formed by this method tends to have defects in its structure and is difficult to use as a dielectric for a capacitor.

(dl Purpose of the Invention The present invention provides a tantalum oxide material, which has low leakage current and is suitable for industrial production of semiconductor devices, as a dielectric material of a capacitor, on a silicon substrate or a silicon layer of a polycrystalline silicon layer provided on a substrate. The purpose is to provide a manufacturing method for forming.

(e) Structure of the Invention The object of the present invention is to provide a tantalum oxide film on a silicon layer, to form a mental film on the tantalum oxide film, and then to oxidize the tantalum film. The tantalum film may be subjected to heat treatment in advance to remove defects in its structure (f) Embodiments of the Invention The present invention will be described below in detail with reference to the drawings. Explain.

1 to 3 are cross-sectional views illustrating an embodiment of the present invention for forming a dielectric of a capacitor of a memory cell of a MOS RAM.

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FIG. 1 shows the back and front states of the present invention, in which 840. A field insulating film 2 and a gate insulating film 3 are provided, and a gate electrode 141 made of polycrystalline silicon is formed through the gate insulating film 3. After forming n++ regions 5 and 6 that will become sources or drains, 8i
0. A polycrystalline silicon film 8 is formed by selectively removing the insulation film 7 on the n+ region surface.

This polycrystalline silicon film 8 becomes one electrode of the capacitor of the intended memory cell, and is doped with the same (njJK) doping as the source and drain.

Figure 2 shows T-town 01 membrane 9 and T1 membrane 1 obtained by the method of this invention.
0 is formed to indicate a large state. That is, the Kt, Ta, C% film 9 is formed on the polycrystalline silicon film 8 to a thickness of, for example, 10#1.
Form to a certain degree. The Tm, O, film 9 can be formed by an electron beam method, but even better results can be obtained by a sputtering method. Next, this Tag O6g 9 upper fc
A Ta film 10 is formed to a thickness of, for example, about 50 mm. This thickness can be arbitrarily selected to be about 10- or more. The T1 film 10 can also be formed by electron beam vacuum evaporation, but sputtering is preferred.

If heat treatment is performed at a temperature of about 800° C. in a vacuum after Ta1IO is formed, it is expected that a film of higher quality will be obtained due to improvement of the crystallinity of the Ta film 10 or increase in crystal grains. This greatly affects the quality of the Ta1O1 film.

After forming the T1 film 10 or after the heat treatment, KTajl11
By oxidizing 0, Ta, 0-film 1 and K Tag 0
One film lit is formed. FIG. 3 shows this Ta,O,- film 11.
A polycrystalline silicon film 12 serving as an electrode is provided thereon and divided into memory cells to form a conductor +1 to show a large state.

Oxidation of Ta Jig 10 is carried out, for example, by heating at a temperature of 500"CIIItK in a dry oxygen tS atmosphere.
) Atsushi 3! Unlike the case of the prior art described above, since the Tal0@ film 9 is interposed between the polycrystalline silicon film 8, silicidation of %T does not occur, and the temperature and time can be selected over a wide range. I can do it.

As an oxidation method for reducing the leakage current of 9 Tl*0*ml formed from the -★ Tm film 10, there is an oxidation method in an atmosphere containing chlorine, which is proposed separately by the present inventor. For example, the oxidation method at 0°C is shown in Figure 1. 3Il! l

Claims (1)

[Claims] Manufacture of a semiconductor device comprising a step of providing a tantalum oxide film on a silicon layer, and after forming a tantalum film on the tantalum oxide film, oxidizing the skeleton tantalum film to form a tantalum oxide film. Method.