JPS63312664A - Manufacture of capacitor for semiconductor device - Google Patents

Abstract

PURPOSE:To reduce a leakage current by forming an intermediate layer made of metal to become by oxidizing high dielectric or high dielectric, then oxidizing it in an oxidative atmosphere to convert part of a lower electrode into an insulator, and then forming an upper electrode on the intermediate layer. CONSTITUTION:A tantalum nitride film (TaN) is formed as a lower electrode 11 by RF sputtering on an Si substrate 10. Then, a tantalum oxide film (Ta2O5) is deposited as an intermediate layer on the electrode 11. This sample is heat treated at 750 deg.C for 1 hour in an Ar atmosphere, and then oxidized at 750 deg.C for 10min in an oxidative atmosphere. This is further heat treated at 950 deg.C for 30min in a nonoxidative atmosphere. An aluminum film is deposited as an upper electrode 13 on the layer 12. Thus, the layer 12 made of the Ta2O5 film is interposed between electrodes 11 and 13 to complete a capacitor. The capacitor is connected, for example, to the source of a MOS transistor to be used as a memory capacitor.

Description

[Detailed Description of the Invention] [Purpose of the invention] (Field of industrial application) The present invention relates to a method of manufacturing a capacitor for a semiconductor device, and particularly relates to a method of manufacturing a capacitor for a semiconductor device, and in particular, the present invention relates to a method of manufacturing a capacitor for a semiconductor device. The present invention relates to a method of manufacturing a capacitor for a semiconductor device.

(Prior art) In recent years, with the development of semiconductor manufacturing technology, semiconductor devices have become more highly integrated and densely packed. There is a strong demand for downsizing of memory cells. This miniaturization of memory cells leads to a reduction in the area of storage capacitors, which inevitably leads to a decrease in the number of capacitors.

On the other hand, in order to deal with the soft error caused by α playback and to secure the read signal, the appearance of the storage capacitor cannot be reduced to a large extent.

With current technology, the N product charge amount to the capacitor is 150
~200 rc is required. Silicon oxide film (SiO2) is widely used as the dielectric film for this type of capacitor, but as attempts are made to further increase the capacitance to 11M, a problem has arisen in that silicon oxide film lacks the amount of stored charge. .

That is, in order to increase the capacitance, it is necessary to make the dielectric film thinner, but if the dielectric film becomes thinner, reliability problems such as dielectric breakdown cannot be overcome.

Therefore, recently, in order to secure the accumulated charge ω of a capacitor, an effective method of expanding the area by searching for a high dielectric material or forming grooves has been proposed. Insulating films that have a higher permittivity than the currently used silicon oxide film include alumina, titanium oxide, hafnium oxide, l! Zirconium dioxide, silicon nitride, i%! It is listed as a candidate for tantalum. Among them, tank oxidation It! has a proven track record as a high dielectric film. (Ta20S) has high expectations.

The dielectric constant of tantalum oxide film is 20 or more, which is 5 to 6 times that of silicon oxide film, and is expected to be compatible with 4M bit DRAM.

As described above, there are high hopes for tantalum oxide films that have a high dielectric constant, but currently the breakdown voltage is low.

No one has been found that satisfies the leakage current.

That is, even if the film has a high dielectric constant, a decrease in breakdown voltage and leakage current characteristics results in a decrease in the amount of accumulated charge. Therefore, even though the dielectric constant is 5 to 6 times that of a silicon oxide film, the amount of accumulated charge is at most twice that of the silicon oxide film at the current technological level. In this case,
From a long-term perspective, it must be said that there is no place for high dielectric constant films. Note that the tantalum oxide film is obtained by forming a tantalum film by electron beam evaporation, DC sputtering ffi, RF sputtering, or the like, and then performing thermal oxidation, plasma oxidation, anode oxidation, or the like. Furthermore, a tantalum oxide film is also formed directly on a silicon substrate by RF sputtering using an oxide target. Furthermore, CVD methods using organometallic compounds are also known. - However, in either method, heat treatment at 600° C. or higher causes a sudden increase in breakdown voltage and leakage current, which has been a major obstacle to practical application.

Further, in order to improve breakdown voltage and leakage current, it is effective to interpose a silicon oxide film or a silicon nitride film between the tantalum oxide film and the silicon male plate.

However, both silicon oxide films and nitride films have dielectric constants of 1/6 to 1/1 compared to tantalum oxide films.
3, and the presence of these films with low dielectric constants in series causes a very large decrease in the lff1 factor as a whole. Furthermore, since the film thickness of the low dielectric constant material has a large influence on the composite dielectric constant, it is necessary to strictly control the film thickness in order to obtain a capacitor having a constant volume @ chain.

For this reason, practical field values could hardly be expected.

(Problems to be Solved by the Invention) Conventionally, high dielectric constant films such as tantalum fused films have the drawback that their leakage current increases when subjected to high-temperature heat treatment. For this reason, the height of tantalum oxide film etc. is 1?
! ? Even if a capacitor is formed using a body film, it is difficult to obtain a sufficiently large amount of accumulated charge due to the deterioration of leakage current characteristics of a high dielectric film.

The present invention has been made in consideration of the above circumstances, and its purpose is to provide a reliable capacitor for semiconductor devices that can reduce leakage current in a high dielectric film and has a large amount of accumulated charge. The purpose is to provide a manufacturing method.

[Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is to repair defective parts that cause leakage current in a high dielectric film by oxidizing a part of the lower electrode. be. Leakage current in high R1 systems is due to defects in the film, and it is known that defects in particular increase significantly during high-temperature heat treatment (including thermal oxidation). It is substantially difficult to form a dielectric film with no defects; rather, leakage current should be reduced by introducing a process that reduces defective locations to [1]. Based on this idea, the inventors investigated the process of forming an oxide film and found that a method of converting a portion of the lower electrode into an insulator through the defect location is extremely effective in reducing leakage current.

The present invention has been made with attention to such points, and in a method for manufacturing a capacitor for a semiconductor device using a high dielectric constant film, a method for manufacturing a capacitor for a semiconductor device using a high dielectric constant film is provided. After forming an intermediate layer made of a metal or a high dielectric material that is oxidized to become a high dielectric material on the lower electrode, a part of the lower electrode is converted into an insulator by performing oxidation treatment in an oxidizing atmosphere, In this method, an upper electrode is then formed on the intermediate layer.

(Function) According to the present invention, leakage current in a high dielectric film is reduced in the following manner. That is, tantalum, niobium, titanium, hefnium, zirconium, aluminum, rare earth elements, or their nitrides or silicides are used for the lower electrode, and on top of this, a high dielectric material made of an oxide film of tantalum, titanium, etc. is used as an intermediate layer. Deposit the film. In this state, it is effective to further generate defects in the high dielectric constant film by high temperature heat treatment or the like. This does not apply when the high dielectric constant film already contains enough defects. Here, defects that cause leakage current include impurity elements present in the film,
There are grain boundaries, irregularities on the surface of Fi9, stress, etc. In any case, it is based on the non-uniformity of the film.

Next, a portion of the lower i-electrode is oxidized through the defects in the intermediate layer in an oxidizing atmosphere. Although there is not always a perfect one-to-one correspondence between defects that cause leakage current and metal ion species in the oxidizing material or lower electrode, these ion species are mainly diffused and diffused through the defect location. Moving. As a result, the lower electrode near the defective location is oxidized and becomes an insulator. As a result, the defective portion is repaired and leakage current can be reduced.

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

- FIG. 1 is a process sectional view for explaining the first embodiment method of the present invention. First, as shown in FIG. 1 (a), an RF
Tantalum II nitride (TaN) was formed as the lower electrode 11 to a thickness of 1000 nm by sputtering. Subsequently, a tantalum oxide film (T820s) as an intermediate layer 12 was deposited on the lower electrode 11 to a thickness of 200 mm.

This sample was heat-treated at 750° C. for 1 hour in an Ar gas atmosphere to generate defects in the Ta205 film. Next, this Ta205! In order to repair the defects in i, oxidation treatment was performed at 750° C. for 10 minutes in an oxidizing atmosphere. This was further heat-treated at 950° C. for 30 minutes in a non-oxidizing atmosphere, and the leakage current characteristics were examined as described below.

Next, as shown in FIG. 1(b), an Aff film as an upper electrode 13 was formed on the intermediate layer 12 by kiln deposition. As a result, the intermediate layer 12 made of the Ta205 film is connected to the electrodes 11.13.
The capacitor sandwiched between the two is now completed. Further, this capacitor is used as a memory capacitor by being connected to the source of a MoS transistor, for example, as shown in FIG.

In FIG. 2, 21 is a gate insulating film, 22 is a gate N pole, and 23a and 23b are '/- soustrain regions.

Now, when the leakage current characteristics of the above sample were investigated, the results shown in FIG. 3 were obtained. That is, the sample that was only heat-treated in the Ar gas atmosphere had a very large leakage current as shown in a in the figure. Further, the sample oxidized in an oxidizing atmosphere is labeled b in the figure, and the sample further heat-treated in a non-oxidizing atmosphere is labeled C in the figure, and the leakage current was significantly reduced compared to sample a. For comparison, a sample a' which was not heat-treated in the Ar gas atmosphere and a sample C' which was further heat-treated at 950° C. for 30 minutes are shown. From these results, it can be seen that the dielectric film subjected to the repair treatment maintains a low leakage current even after high-temperature heat treatment at 950°C.

Thus, according to one embodiment method, Ta20sl! A capacitor can be formed using a high dielectric material of 1st class,
In addition, leakage current of the high dielectric film can be significantly reduced. For this reason, the amount of accumulated charge per medium area is increased to about 2 to 8 times that of the conventional high dielectric film. Therefore, when the method of this embodiment is applied to a memory capacitor or the like, it is possible to realize a capacitor having a large storage current ω in a small area, which is extremely effective in manufacturing a DRAM.

In addition, by performing heat treatment in an Ar gas atmosphere, defects are generated in a cumulative manner before oxidation, so defects can be repaired more effectively in the subsequent oxidation treatment. Since TaNi1, which forms an oxide with a high dielectric constant, is used as the lower electrode 11, the decrease in capacitance due to the formation of this oxide is extremely small. Since it has a barrier property that prevents high-temperature reactions with the dielectric film that is the layer 13, it is also effective from the viewpoint of protecting the substrate.

Next, a second embodiment method of the present invention will be described. In this example, Ta nitride was used as the lower electrode 11, and titanium oxide l1l (TiO2) was deposited on the lower electrode 11 to a thickness of 300 nm as the intermediate layer 12. Next, heat treatment was performed at 800°C for 30 minutes to remove TlO2.
This caused defects in the film.

Thereafter, a portion of the lower electrode 11 was oxidized through the defects in Ti0zl19 in an oxygen atmosphere, thereby repairing the defects in the TiO2 film.

As a result, the leakage current of the dielectric film was reduced, and even after high-temperature treatment, the increase in leakage current was extremely small.

Thus, according to the method of this embodiment, TiO2, which conventionally had a significantly large leakage current because it was easily crystallized at low temperatures,
The effect of significantly reducing leakage current can also be obtained. In addition, as the lower mold 1 coffin 11, Nb, Ti is used instead of Ta.
Similar effects were obtained using nitrides such as , Hf, Zr, and Affi. Furthermore, similar effects were obtained even when a silicide film was used as the lower electrode 11.

Next, a third embodiment method of the present invention will be described. This practical example aims to further reduce -H in leakage current by forming a composite dielectric film.

First, as shown in FIG. 1, titanium nitride flu (TiN) was formed to a thickness of 2000 nm as a lower electrode 11 on a 3i substrate 10 on which a storage capacitor was to be formed.

Subsequently, tantalum oxide II! is deposited on the lower electrode 11 as the intermediate layer 12! (Ta20s) was deposited to a thickness of 0 to 200 nm. This was heated to 700°C in an oxidizing atmosphere. 30
Oxidation treatment was performed for 1 minute. Through this oxidation treatment, a part of the lower electrode 11 is oxidized, and this oxide film and Ta20
sNQ becomes Φ, and a decomposed dielectric film is formed.

Next, as shown in FIG. 1(b), an A2 layer was deposited on the intermediate layer 12 as an upper electrode 13 to complete a capacitor. When the leakage current characteristics and the dependence of the dielectric constant on the film thickness of the Ta205 film of this sample were investigated, the results shown in FIGS. 4 and 5 were obtained. From the results in Figure 4, T
It can be seen that the thicker the a205 film is, the smaller the leakage current is. Furthermore, it can be seen that when the film thickness is 100 to 200, the leakage current characteristics are close to those shown in FIG. 3 in the first practical example. Also, from the binding in Figure 5, Ta205
II! It can be seen that the thinner the film thickness, the higher the dielectric constant of the composite dielectric film. This shows that the 17ff rate, which is higher than that of the Ta205 film, can be increased by 1q due to the formation of the composite oxide film.

Thus, according to the method of this embodiment, it is possible to form a high dielectric constant film having a larger dielectric constant than the Ta205 film. For this reason, the V4 charge capacity per unit area is about 4 to 8 times that of the conventional high dielectric film. Therefore,
The same effects as in the first embodiment can be obtained.

Next, a fourth embodiment method of the present invention will be described. In this example, Ta nitride is used as the lower electrode 11, and titanium oxide flu (TiO2) as the intermediate layer 12 is deposited on the lower electrode 11 to a thickness of 0 to 300 nm.

Next, heat treatment was performed at 700° C. for 30 minutes in an oxidizing atmosphere to form a composite dielectric film.

As a result, the leakage 'Wi current of the dielectric film decreased, and even in the case of high wetting treatment (1), the leakage current increased only at the extreme parts.

Further, as the lower electrode 11, Nb is used instead of Ta.

Similar effects were obtained using nitrides such as Ti, Hf, Zr, and Aλ. Furthermore, similar effects were obtained even when a silicide film was used as the lower electrode 11.

Note that the present invention is not limited to the methods of each of the embodiments described above. For example, in addition to the electrode shown in the embodiment, the lower electrode may be a conductor 71 that is liquefied in an oxidizing atmosphere to form an insulator. Further, the intermediate layer is not limited to an oxide film such as Ta or Ti, but it is also possible to use a metal that becomes a high dielectric constant film through subsequent oxidation treatment.

In general, the oxidation treatment is not limited to thermal oxidation, but it is also possible to use plasma oxidation, anodic oxidation, and the like. In addition, conditions such as heating temperature for 1 hour in oxidation treatment are as follows:
It can be changed as appropriate depending on the specifications. In addition, various modifications can be made without departing from the gist of the present invention.

[Effect of Fl Light] As described in detail above, according to the present invention, defective parts that cause leakage current in the high dielectric material 9 are fixed by oxidizing a part of the lower electrical connection. It is possible to significantly reduce leakage current in body membranes during high stepping. Therefore, a highly reliable capacitor for a semiconductor device with a sufficiently large amount of stored charge can be manufactured, and its usefulness is extremely high.

[Brief explanation of drawings]

1 to 3 are for explaining the method of the first embodiment of the present invention, and FIG. 1 is a process sectional view, and FIG. 2 is a DRAM.
A cross-sectional view showing an example applied to a cell, Fig. 3 is a characteristic diagram showing leakage current characteristics, Figs. 4 and 5 are for explaining the method of the third embodiment, and Fig. 4 is a tantalum oxidation method. FIG. 5 is a characteristic diagram showing leakage current characteristics when the film is used as a parameter, and FIG. 5 is a characteristic diagram showing changes in dielectric constant with respect to film thickness of a tantalum oxide film. 10...3i substrate, 11...lower electrode, 12...
Intermediate layer, 13... Upper electrode, 21... Gate insulating film, 22... Gate electrode, 23a, 23b... Source/drain region. (a) (b) Figure 1 Figure 2 Figure 3

Claims (4)

[Claims] (1) Forming an intermediate layer made of a metal or a high dielectric material that becomes a high dielectric material when oxidized on a lower electrode made of a metal, a metal nitride, or a metal silicide that is oxidized in an oxidizing atmosphere; A capacitor for a semiconductor device, comprising the steps of: converting a part of the lower electrode into an insulator by performing oxidation treatment in an oxidizing atmosphere; and forming an upper electrode on the intermediate layer. Production method. (2) The semiconductor device according to claim 1, wherein one type of nitride selected from tantalum, niobium, titanium, hafnium, zirconium, and aluminum is used as the lower electrode. Method of manufacturing capacitors. (3) The method for manufacturing a capacitor for a semiconductor device according to claim 1, wherein a tantalum or titanium oxide film is used as the intermediate layer. (4) The method for manufacturing a capacitor for a semiconductor device according to claim 1, wherein heat treatment is performed in a non-oxidizing atmosphere before the oxidation treatment step.