JPH04192556A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To reduce a leakage current and to form a capacitor having a dielectric film whose specific permittivity is large by a method wherein a thin metal film is irradiated with a high energy beam in an oxidizing atmosphere, it is charged to a metal oxide film, the dielectric film for a capacitor is produced and a counter electrode for the capacitor is formed on the dielectric film. CONSTITUTION:A thin metal film 5 used to constitute a dielectric film for a capacitor is formed on a barrier film 4; the thin metal film 5 is irradiated with a high energy beam, melted and solidified; the film is charged to a metal oxide film; the dielectric film for the capacitor is produced; a counter electrode 3 for the capacitor is formed on the dielectric film. As a result, a crystal defect and a pinhole hardly exist in the thin metal film 5; the film can be formed as a uniform and good-quality film. The polycrystallization of a metal oxide which is caused when a substance is moved during a reaction process is not caused. Thereby, an electric current which is leaked along a grain boundary is reduced, and the capacitor having the dielectric film whose specific permittivity is large can be obtained.

Description

[Detailed Description of the Invention] [Summary] A method suitable for manufacturing a semiconductor device requiring a capacitor such as a dynamic random access memory, which can prevent a film made of a metal oxide from becoming polycrystalline. With the aim of obtaining a semiconductor device incorporating a capacitor with a dielectric film having a low leakage current and a high dielectric constant, we formed a silicon storage electrode on a substrate to form a capacitor. Next, a barrier film is formed to prevent other substances from entering the silicon storage electrode, and then a metal thin film is formed on the barrier film to form a dielectric film of a capacitor. Alternatively, the metal thin film is irradiated with a high-energy beam such as an electron beam to melt and solidify, and then the densified metal thin film is irradiated with a high-energy beam such as a laser or an electron beam in an oxidizing atmosphere. The method includes the steps of: irradiating the method to convert the metal oxide film into a dielectric film of the capacitor; and then forming a counter electrode of the capacitor on the dielectric film.

[Industrial application field]

The present invention is a dynamic random access memory (dynamic random access memory).
The present invention relates to a method suitable for manufacturing semiconductor devices that require capacitors, such as memory (DRAM).

In recent years, with the miniaturization of semiconductor devices having capacitors such as DRAMs, the planar area occupied by the capacitors has been reduced, making it difficult to ensure sufficient capacitor capacity.

Therefore, research and development on such capacitors to date have focused exclusively on making the dielectric film thinner and making the capacitor three-dimensional in order to increase the capacitance of the capacitor.

Such countermeasures may be effective for the miniaturization required to manufacture 64MDRAM.

However, it is thought that this will reach its limit.

Therefore, new means will be required for subsequent miniaturization.

[Conventional technology]

Currently, in response to miniaturization after 64M DRAM, 5iOz film or SiO□/S i :IN a that has been conventionally used as a dielectric film for capacitors is used.
/ S i O□ three-layer structure film, that is, 0NOl! As an alternative to ma, IVa of the periodic table.

Metal oxides of various groups of Va are attracting attention. These metal oxides are known as high dielectric constant oxides, and their relative permittivity is approximately 25 on average, and S 10 z is 3.
8, it is more than 6 times more than 64MDR.
It is thought that it will be able to fully cope with the miniaturization after AM.

To form this metal oxide film, plasma CVD (p
lasma chemical vapor
A thermal oxidation method, a thermal CVD method, etc. are commonly used.

[Problem to be solved by the invention]

The metal oxide film formed by the plasma CVD method described above has not reached the level of practical use. The reason for this is that it has the disadvantage of a large leakage current.

This leakage current originates from polycrystallization of the metal oxide during the process of forming the metal oxide film. That is, since leakage current is generated through grain boundaries of crystals, it is natural that it increases in the case of polycrystals.

The present invention makes it possible to prevent a film made of a metal oxide from becoming polycrystalline, and to provide a semiconductor device 1 incorporating a capacitor with a dielectric film having a small leakage current (and a high relative dielectric constant). make sure you get it.

[Means to solve the problem]

In the method for manufacturing a semiconductor device according to the present invention, (1)
A silicon storage electrode (for example, storage electrode electrode 3) for forming a capacitor is formed on a substrate (for example, a Si semiconductor substrate 1), and then a barrier film is formed to prevent other substances from entering the silicon storage electrode. A thin metal film (for example, a metal thin film 5) for forming a dielectric film of a capacitor is then formed on the barrier film, and then a high-intensity beam such as a laser or an electron beam is formed. The metal thin film is melted and solidified by irradiation with an energy beam, and then the densified metal thin film is irradiated with a high-energy beam such as a laser or an electron beam in an oxidizing atmosphere to form a metal oxide film. to form a dielectric film (for example, metal oxide thin film 5'') of the capacitor, and then forming a counter electrode of the capacitor (for example, counter electrode (cell plate) 6) on the dielectric film. (2) In (1) above, the barrier film that prevents other substances from entering the silicon storage electrode is made of TiN. (3) In (1) above, the barrier film that prevents other substances from entering the silicon storage electrode is made of TiW, or (4) ) In the above (1) or (2) or (3),
The thin metal film constituting the dielectric film of the capacitor is characterized by being made of a metal of the Ma group, IVa group, or Va group.

[Operation] By adopting the above-mentioned measures, the metal thin film of the MA group, IVa group, or Va group, which is oxidized and becomes the dielectric film of the capacitor, has almost no crystal defects or pinholes, and is made uniform and of good quality. Moreover, since it is instantaneously reacted with atmospheric gas to form a metal oxide film, polycrystallization of the metal oxide due to mass transfer during the reaction process does not occur, and therefore, there is no formation of polycrystallization at grain boundaries. The current leaking along the line is significantly reduced, and the dielectric strength of the metal oxide film is also sufficiently high.

(Embodiment) FIGS. 1 to 5 are cross-sectional side views of essential parts of a semiconductor device at key points in the process for explaining an embodiment of the present invention, and the explanation will be given below with reference to these figures. do.

See FIG. 1. For example, a selective thermal oxidation method using a Si or N4 film as an oxidation-resistant mask, such as LOCO3(l).

cat oxidation of 5ilic
On) method is applied to form a field insulating film 2 having a thickness of, for example, 500 (nm) on the surface of the Si semiconductor substrate 1 for isolation between elements.

The oxidation-resistant mask used during selective thermal oxidation is removed, and S
i After exposing a part of the semiconductor substrate 1, LPCVD (
low pressure chemical va
By applying the Pour deposition method, P-containing polycrystalline S with a thickness of, for example, 200 (nm) is deposited.
Form an i-film.

This P-containing polycrystalline Si film can be formed by adding P during growth as described above, or by ion implantation after growing the polycrystalline Si film. The concentration of P is, for example, 5 in terms of dose.
x 10'' (ell-2).

By applying ordinary photolithography technology, the P-containing polycrystalline Si film is patterned to form the storage electrode 3 of the capacitor.

Refer to Figure 2. For example, by applying a sputtering method, TiN or TiW having a thickness of about 50 (nm) can be formed.
A barrier metal film 4 consisting of, etc. is formed.

As a technique for forming the barrier metal film 4, a thermal CVD method or the like can be applied in addition to the sputtering method.

By applying the sputtering method, it is possible to deposit materials such as the Ma group, IVa group, and Va group of the periodic table with an average thickness of 5 (nm).
A thin film 5 made of a metal selected from the group consisting of:

Note that as a technique for forming the metal thin film 5, an electron beam evaporation method or the like can be applied in addition to the sputtering method. Moreover, regardless of which technique is applied, the obtained metal In! 5 by SEM (scanning el)
When observed with an electron microscope, it can be seen that many irregularities are generated on the surface, and that pinhole-like things are unevenly present.
In addition, TEM (transmission elect
When observed with a tron m1 microscope, it can be seen that many crystal defects are scattered.

Referring to FIG. 3, the metal thin film 5 is melted by irradiation with a high-energy beam such as a laser beam or an electron beam, and then solidified. This laser irradiation or electron beam irradiation will be referred to as pre-laser irradiation or pre-electron beam irradiation to distinguish it from high-energy beam irradiation in an oxygen atmosphere that will be performed in a later process. .

This melting and solidification of the metal thin film 5 may be performed not only once, but multiple times as necessary, so that the metal thin film 5 is flattened and uniform, and pinholes are removed. and crystal defects can be reduced.

For convenience, the metal thin film 5 after such treatment is indicated by the symbol 5'.

Refer to Fig. 4. The metal thin film 5' is irradiated with a high-energy beam such as a laser or an electron beam in an oxygen atmosphere to form a metal oxide thin film 5''.
Convert to

The film quality of the metal oxide thin film 5″ thus obtained was determined by S
Observation with EM shows that the metal thin film 5' that has been subjected to the melting and solidification treatment maintains a good condition, and does not undergo polycrystallization unlike metal oxide thin films produced by conventional techniques. This can be confirmed. The reason why polycrystalization does not progress is that the metal thin film 5' is instantaneously oxidized in a time on the order of 2 to 3 (msec) due to high-energy beam irradiation, so no mass transfer occurs. It is thought that it depends on the

By applying the LPCVD method (see FIG. 5), the metal oxide thin film 5
A P-containing polycrystalline Si film having a thickness of, for example, about 200 nm is formed on #.

This P-containing polycrystalline Si film can be formed by adding P during growth as described above, or by introducing it by ion implantation after growing the polycrystalline Si film.
In addition, the concentration of P is, for example, 5 x 10 in terms of dose.
” (ci-”).

By applying ordinary photolithography technology, the P-containing polycrystalline Si film formed in step 5-(1) is patterned to form the counter electrode (cell plate) of the capacitor.
6, and the capacitor is now completed.

FIG. 6 shows a diagram for explaining the relationship between applied voltage and leakage current density for capacitors made according to the present invention and capacitors made by applying various techniques for comparison. is the applied voltage (V), and the vertical axis is the leakage current density CA/C11'').

The dielectric film of the capacitor when this data was obtained was TazO.
s film, and the steps described in FIGS. 1 and 2,
That is, the steps up to forming the metal thin film 5, here a Ta thin film, are all the same for each sample.

The thickness of the Ta film formed by sputtering method is 5 (nm).
The thickness of the Ta, O, film produced by thermal oxidation in the conventional technique or laser irradiation oxidation in the present invention is about 10 nm. Thickness is 10 (nm)
The performance as a dielectric film obtained with the TazOs film of Si
n, the film thickness is 3 (nm).

As the barrier metal film 4, a TiN film with a thickness of 50'', nm was used.

The laser used for laser irradiation oxidation was an excimer laser.

In Figure 6,
0 portion] and converted to T'a, O, and thin film.

■; Similarly to ■, the Tal film is oxidized by laser irradiation in an oxygen atmosphere without prior laser irradiation, and T a z
This was converted into an Os Fi film.

The conditions for laser irradiation in this case are that the laser intensity density is 1.
5 (J/am"), and the pulse width is 30 [n seconds].

(2): A Ta thin film was pre-irradiated with laser and then thermally oxidized under the same conditions as (2) to convert it into a TazOs thin film.

In this case, the pre-laser irradiation conditions are such that the laser intensity density is 3
．． 5 [J 7cm2], and the pulse width is 30[n
seconds].

(2) This is the second embodiment of the present invention, and Taz
This is a thin film of Os.

As is clear from ■ and ■ in the figure, the leakage current was large without prior laser irradiation, and there was almost no difference between thermal oxidation and laser irradiation oxidation. As shown in ■ in the figure, the leakage current is slightly reduced by pre-laser irradiation + thermal oxidation, but it is insufficient from a practical point of view. As seen in ■ in the figure, the leakage current is sufficiently reduced in the pre-laser irradiation + laser irradiation oxidation.

As described above, a dielectric film with low leakage current can be obtained for the first time by combining pre-laser irradiation and laser irradiation oxidation according to the present invention.

Regarding the capacitor made under the conditions of (■) above, 1O-b
The dielectric strength voltage is 14 (M V /
cva) and TDDB (time de
pendence dielectric bre
As a result of measurement, it was found that the device had a lifespan of 10 years, which was sufficient for practical use, and that the dielectric film was highly reliable.

By the way, as described above, the pre-laser irradiation serves to melt and solidify the formed metal thin film to flatten the surface and to reduce pinholes and crystal defects in the film.

However, even if pre-laser irradiation is performed, if thermal oxidation is performed afterwards, mass transfer of, for example, TazOs will occur during the oxidation process and polycrystallization will progress, resulting in an increase in leakage current. Conceivable. In laser irradiation oxidation, Ta is oxidized instantaneously as described above, so it is thought that the mass transfer of TazOs is suppressed.
Polycrystallization does not occur, and the dielectric film is produced while preserving the good film quality immediately after the previous laser irradiation.

FIG. 7 is a diagram for explaining the relationship between applied voltage and leakage current density for a capacitor made according to the present invention and a capacitor made by applying the conventional technology for comparison. is the applied voltage ryE, and the vertical axis is the leakage current density CA/C1+2').

In the figure, ■ is the characteristic line of the capacitor according to one embodiment of the present invention, as in FIG.
conductor W.

rld 1990 5 P, 113J), in which a Tazo s film was formed by the LPCVD method and IJV (u
This is a case where two-step annealing is performed, which is so-called Uv ozone annealing and dry oxidation annealing, in which annealing is performed while irradiating (ltraviolet rays), and
This is the case where a TazOs film was formed by sputtering and dry oxidation annealing was performed. The thickness of the Taz05 film in both (1) and (2) was 10 [nm], which is the same as in the experiment conducted for making the present invention.

As can be seen from the figure, it is clear that according to the characteristic line (2) according to the embodiment of the present invention, the leakage current is extremely small compared to the characteristic lines (2) and (2) of the conventional example.

FIG. 8 is a diagram for explaining the relationship between applied voltage and leakage current density for capacitors made according to the present invention and capacitors made by applying various techniques for comparison. is the applied voltage (yE), and the vertical axis is the leakage current density [A/cTIi2].This data is based on an experiment roughly similar to that in which the data in Figure 6 was obtained. You can think of it as something you got by going there.

The dielectric film of the capacitor when this data was obtained was TiO2
Here, the steps to form the Tifji film are all the same for each sample.

The thickness of the Ti film formed by sputtering method is 5 (nm).
The thickness of the Tie film produced by thermal oxidation in the conventional technique or laser irradiation oxidation in the present invention is about 15 [nm]. The performance as a dielectric film obtained with a TiO2 film with a thickness of 15 (nm) is
The film thickness is 2.5 (nm).

The barrier metal film is made of TiN with a thickness of 50 [nm].
A membrane was used.

Laser irradiation oxidation The laser used is XeCl excimer.
It's a laser.

In Fig. 8, ■: The case where the Ti'l film was thermally oxidized without prior laser irradiation, and the thermal oxidation was carried out for 10 (minutes) in an oxygen atmosphere of 950 ('C3) and converted to a Tie2 thin film. This is what I did.

■: Similar to ■, the Ti thin film is oxidized by laser irradiation in an oxygen atmosphere without prior laser irradiation.
It was converted into an i0zFf film.

The conditions for laser irradiation in this case are that the laser intensity density is 1.
3 (J/cm2), and the pulse width is 30 [n seconds]
It is.

(2): The Til film was pre-irradiated with laser, and then thermally oxidized under the same conditions as (2) to convert it into a Tie2 thin film.

In this case, the pre-laser irradiation conditions are such that the laser intensity density is 2
．． OCl/CWI” E, and pulse width is 30C
n seconds].

[Phase]: This is an example of the present invention, and T
It is made into an iO□ thin film.

As is clear from ■ and ■ in the figure, the leakage current was large without prior laser irradiation, and there was almost no difference between thermal oxidation and laser irradiation oxidation. As shown in ■ in the figure, although the leakage current is slightly reduced by pre-laser irradiation + thermal oxidation, it is still insufficient for practical use. As seen in the [phase] in the figure, δ, pre-laser irradiation + laser irradiation oxidation,
Leakage current is sufficiently reduced.

Also in this case, a dielectric film with low leakage current can be obtained for the first time by combining pre-laser irradiation + laser irradiation oxidation according to the present invention.

Regarding the capacitor created under the above [phase] conditions, 10
The dielectric strength voltage is 13 [MV
/C11) The lifespan of the element was 9 years as a result of Tearly and TDDB measurements, and this example is also a dielectric film that is sufficient for practical use and has high reliability.

〔Effect of the invention〕

In the method for manufacturing a semiconductor device according to the present invention, a silicon storage electrode for forming a capacitor is formed, a barrier film is formed to prevent other substances from entering the silicon storage electrode, and a barrier film is formed to prevent other substances from entering the silicon storage electrode. A thin metal film to constitute the dielectric film of the capacitor is formed on the barrier film, the metal thin film is melted and solidified by irradiation with a high-energy beam, and the metal thin film is irradiated with a high-energy beam in an oxidizing atmosphere. is irradiated and converted into a metal oxide film to generate a dielectric film of a capacitor, and a counter electrode of the capacitor is formed on the dielectric film.

By adopting the above structure, the metal thin film of the Ma group, TVa group, or ~°a group, which is oxidized to become the dielectric film of the capacitor, has almost no crystal defects or pinholes, and is uniform and of good quality. Moreover, since it is instantaneously reacted with atmospheric gas to form a metal oxide film, polycrystallization of the metal oxide due to mass transfer during the reaction process does not occur, and therefore, polycrystallization of the metal oxide does not occur along grain boundaries. The leakage current is significantly reduced, and the dielectric strength of the metal oxide film is also sufficiently high.

[Brief explanation of the drawing]

1 to 5 are cross-sectional side views of essential parts of a semiconductor device at key points in the process for explaining one embodiment of the present invention, and FIG. 6 is a side view of a capacitor manufactured according to the present invention and for comparison. Diagrams for explaining the relationship between applied voltage and leakage current density of capacitors created by applying various techniques, FIG. 7 shows capacitors created according to the present invention and conventional technology applied for comparison. Fig. 8 is a diagram for explaining the relationship between applied voltage and leakage current density of a capacitor made according to the present invention and capacitors made by applying various techniques for comparison. Each of the diagrams shows a diagram for explaining the relationship between the applied voltage and the leakage current density. In the figure, 1 is a Si semiconductor substrate, 2 is a field insulating film, 3 is a storage electrode of a capacitor, 4 is a barrier metal film, 5 is a metal thin film, 5' is a melted and solidified metal thin film, 5''
6 is the metal oxide thin film, and 6 is the counter electrode of the key vanta (cell).
plate) are shown respectively. Patent Applicant: Fujitsu Ltd. Representative Patent Attorney: Akira Aitani Representative Patent Attorney: Hiroshi Watanabe - 1 (Si semiconductor substrate) Cutaway side view of essential parts of a semiconductor device at important process points to explain embodiments Figure 1: Process for explaining the embodiment @ cut-away eI side view of essential parts of the semiconductor device at important points Figure 2: 5 (melted and solidified metal thin film) Process outline for explaining the high-energy beam embodiment Figure 3: Cutaway side view of essential parts of a semiconductor device at a location (metal W arsenal thin film)
Adding a cutaway side view of the main part of a semiconductor device at a key point in the process to explain the beam example 6 (Counter electrode) Voltage () Diagram for explaining the relationship between the applied voltage of the capacitor and leakage current density Figure 6 Applied voltage (V) Diagram for explaining the relationship between the applied voltage of the capacitor and the leakage current density Figure 7

Claims (4)

[Claims] (1) Form a silicon storage electrode to form a capacitor on a substrate, then form a barrier film to prevent other substances from entering the silicon storage electrode, and then form a capacitor on the barrier film. A thin metal film is formed to constitute a dielectric film, and then a high-energy beam such as a laser or an electron beam is irradiated to melt and solidify the metal thin film, and then the densified metal The thin film is irradiated with a high-energy beam such as a laser or an electron beam in an oxidizing atmosphere to convert it into a metal oxide film to form a dielectric film of the capacitor, and then a counter electrode of the capacitor is placed on the dielectric film. 1. A method of manufacturing a semiconductor device, comprising a step of forming a semiconductor device. (2) The method of manufacturing a semiconductor device according to claim 1, wherein the barrier film that prevents other substances from entering the silicon storage electrode is made of TiN. (3) The method of manufacturing a semiconductor device according to claim 1, wherein the barrier film that prevents other substances from entering the silicon storage electrode is made of TiW. (4) Metal thin film to constitute the dielectric film of the capacitor
4. The method of manufacturing a semiconductor device according to claim 1, wherein the semiconductor device is made of a metal of group IIIa, group IVa, or group Va.