JP2002203854A - Forming method of high dielectric oxide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form the high dielectric film of a metal oxide having no oxygen defect and superior in withstanding pressure characteristic. SOLUTION: The forming method of the high dielectric oxide film is provided with a first sputtering process for performing reactive sputtering deposition in the atmosphere of Ar+O2 gas in a first chamber holding an inner peripheral side part surrounding a plasma generation part electric conduction and forming a first metal oxide film (Ta2O5 film) on a substrate, and a second sputtering process for performing reactive sputtering deposition in the atmosphere of Ar+O2 in a second chamber having the inner peripheral side of insulation and forming a second metal oxide film (Ta2O5 film) on the first metal oxide film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a high dielectric oxide film, and more particularly to a method of forming a high dielectric film of a metal oxide suitable as a capacitor insulating film for a logic LSI or the like.
The present invention relates to a method of forming by sputtering (reactive sputter deposition).

[0002]

2. Description of the Related Art In recent years, logic LSIs and DRAMs (Rand
om Access Memory)
High dielectric material with high dielectric constant
It is used. As a material with a high dielectric constant, the crystal structure
Is a single lattice of perovskite structure BST ((Ba
/ Sr) TiO₃) And Ta₂O₅Metal represented by
Oxides are known. In particular, Ta₂O₅Has relative permittivity
25 and nitride film (Si₃N ₄) Has almost 4 times higher value
However, application to LSI has been actively studied. And
Such Ta₂O₅In order to form a film, the same as CVD method
Therefore, an inert gas such as argon (Ar) and oxygen
For reactive sputter deposition in a mixed gas atmosphere
The law has been adopted.

[0003]

However, in the conventional method of forming an oxide film by reactive sputter deposition, oxygen vacancies are found in the formed oxide film, and the breakdown voltage characteristics are reduced. There was a problem. Also,
When the film is formed, the underlying electrode substrate and the like are oxidized. For example, when a Si-based material is used for the lower electrode, an electrode oxide layer such as a SiO ₂ layer is easily generated at the interface. As a result, there is a problem that the capacitance value decreases.

The present invention has been made to solve such a problem, and has as its object to provide a method for forming a metal oxide film having a high dielectric constant and excellent withstand voltage characteristics.

[0005]

According to a first aspect of the present invention, there is provided a method for forming a high dielectric oxide film, comprising forming a metal oxide high dielectric film on a substrate. In the method, reactive sputter deposition is performed in a mixed gas atmosphere of oxygen and an inert gas in a first chamber in which an inner peripheral side surface surrounding a plasma generating portion is kept conductive, and A first sputtering step for forming a first metal oxide film, and a second sputtering step having an insulating inner peripheral side surface.
A second sputtering step of performing reactive sputter deposition in a mixed gas atmosphere of oxygen and an inert gas to form a second metal oxide film on the first metal oxide film. It is characterized by having.

According to a second aspect of the present invention, there is provided a method for forming a high-dielectric oxide film on a substrate, the method comprising forming a high-dielectric film of a metal oxide on a substrate. Forming a first metal oxide film on the substrate by performing reactive sputter deposition in a mixed gas atmosphere of oxygen and an inert gas in a first chamber in which the inner peripheral side surface is kept conductive. A first sputtering step of applying a high-frequency voltage to the substrate in a mixed gas atmosphere of oxygen and an inert gas, and performing reactive sputtering deposition while guiding oxygen plasma species to the substrate surface; A second sputtering step of forming a second metal oxide film on the first metal oxide film.
In the second invention, as described in claim 3, the second sputtering step can be performed in the first chamber.

In the method of forming a high dielectric oxide film according to the present invention, the metal oxide film to be formed may be, for example, BST
(Ta / Ti, Zr, Hf, Pb, Ba, Sr, Al) like a thin film of ((Ba / Sr) TiO ₃ ) or Ta ₂ O _5.
And oxide films of one or more metals selected from the group consisting of: In the formation of such a metal oxide film, Ta, Ti, Zr, Hf, Pb, Ba, S
Reactive sputter deposition can be performed using one or more metals selected from r and Al as targets. Also, as described in claim 6, Ta, Ti, Zr, Hf, P
Reactive sputter deposition can be performed using one or more metals selected from b, Ba, Sr, and Al as targets.

In the present invention, a high dielectric capacitor is formed by forming such a high dielectric oxide film on an electrode substrate (lower electrode) and further forming an upper electrode thereon. Can be. High dielectric capacitors are
It is applied to a capacitor such as a semiconductor memory (DRAM) and a logic LSI. As the lower electrode material, polycrystalline silicon, silicide, or Pt, Au, Al, Ti
Metals such as N, TaN, TiW are used. The same or different material as the lower electrode material is used as the upper electrode material.

In the first invention and the second invention of the present invention, the plasma generating portion between the substrate mounting portion and the target is provided on the inner peripheral surface of the first chamber where the first sputtering process is performed. Since the surrounding side surface is conductive, the oxygen plasma species O ^* (oxygen radical species generated by the plasma) hardly reaches the substrate 2 in the first chamber 1 as shown in FIG. As a result, the oxidation reaction of the substrate 2 hardly occurs, the oxidation of the lower electrode on the substrate 2 is suppressed, and the first metal oxide film is formed directly.

Next, in a second sputtering step, reactive sputter deposition is performed while introducing oxygen plasma species O ^* to the substrate. Here, the oxygen plasma species O
^In order to introduce ^* to the substrate, in the first invention, as shown in FIG. 2, reactive sputter deposition with oxygen is performed in a second chamber 3 having an insulating inner peripheral side surface. Further, in the second invention, as shown in FIG.
Reactive sputter deposition is performed while applying a bias by RF (high frequency) to the substrate 2. FIG. 1 is a view schematically showing a state of generation of oxygen plasma inside the first chamber in the first sputtering step, and FIGS. 2 and 3 are views showing the inside of the chamber in the second sputtering step. It is a figure which shows the generation state of oxygen plasma typically. In these figures, the generation state and the reach of oxygen plasma are indicated by oblique lines. Reference numeral 4 indicates a substrate holder, and reference numeral 5 indicates a target.

Thus, in the second sputtering step,
By forming a metal oxide film by reactive sputter deposition while introducing an oxygen plasma species to the substrate, defects in the film are supplemented with oxygen. The second thus formed
The metal oxide film has good bonding state without oxygen deficiency and high withstand voltage characteristics. In the formation of the second metal oxide film, since the first metal oxide film formed in the first sputtering step is formed between the second metal oxide film and the substrate, an oxidation reaction layer is formed between the second metal oxide film and the substrate. Hard to do.

Therefore, according to the present invention having the first sputtering step and the second sputtering step,
It is possible to form a high-capacity high-dielectric-oxide film having no oxygen deficiency, having excellent withstand voltage characteristics, and having no oxidation reaction layer at the interface with the lower electrode.

[0013]

Embodiments of the present invention will be described below.

Example 1 Reactive sputter deposition using Ta as a target was performed as follows, and a 20 nm thick Ta ₂ film was formed on a silicon substrate on which a lower electrode of polycrystalline silicon was formed.
An O ₅ film was formed in two steps of 10 nm in thickness. The two film formations were performed in different chambers.

That is, first, in the first chamber, the first
Was sputtered to form a Ta ₂ O ₅ film having a thickness of 10 nm. In the first chamber, sputtering (dummy sputtering) was performed with the shutter covering the substrate before the Ta ₂ O ₅ film was formed. In this sputtering, while introducing only Ar gas at a gas flow rate of 30 sccm,
A sputtering power of 4 kW is applied for 100 seconds to form a thin film of metal Ta, which is a constituent material of the target, on the side wall between the substrate mounting portion and the target in the first chamber. And

Subsequently, in the first chamber, Ar + O ₂ gas (mixed gas of argon and oxygen) is supplied into the first chamber.
While introducing r gas at a flow rate of 30 sccm and O ₂ gas at a flow rate of 45 sccm, dummy sputtering was performed at a sputtering power of 4 kW for 30 seconds to oxidize the surface of the Ta target.

After the side surface of the inner periphery of the first chamber was made conductive and the target surface was oxidized, the first sputtering was performed in this chamber. In the first sputtering step, Ar + O ₂ gas is supplied at a flow rate of Ar gas of 30%.
While introducing sccm and O ₂ gas at a flow rate of 45 sccm respectively,
Reactive sputter deposition was performed at a sputtering power of 4 kW for 100 seconds, and a first Ta ₂ O ₅ film was deposited on a silicon substrate for 10 seconds.
Deposited to a thickness of nm.

Next, the substrate on which the first Ta ₂ O ₅ film was formed was taken out of the first chamber and subjected to second sputtering in the second chamber.

First, while the substrate was covered by the shutter when the chamber was started, sufficient dummy sputtering was performed to deposit Ta ₂ O ₅ on the side surface of the inner periphery of the second chamber. Next, in the second chamber whose inner side surface was made insulative in this way, a reaction was performed for 100 seconds at a sputtering power of 4 kW while introducing Ar + O ₂ gas at an Ar gas flow rate of 30 sccm and an O ₂ gas flow rate of 45 sccm, respectively. A second Ta ₂ O ₅ film was deposited to a thickness of 10 nm on the first Ta ₂ O ₅ film formed in the first sputtering step.

FIG. 4 shows a cross-sectional structure of the high dielectric film thus formed. In the drawing, reference numeral 6 denotes a silicon base substrate, reference numeral 7 denotes a lower electrode of polycrystalline silicon formed thereon, and reference numeral 8 denotes a high dielectric film. High dielectric film 8, the second Ta ₂ O of which the first and the Ta ₂ O ₅ film 8a of thickness 10nm is formed in the second sputtering process with a thickness of 10nm formed by first sputtering step composed of the ₅ film 8b.

The high dielectric film 8 (film thickness) formed in Example 1
In the case of (20 nm), since no oxidation reaction layer is generated at the interface with the lower electrode 7, there is no deterioration in capacitance characteristics, and there is no oxygen deficiency in the film, and the bonding state is good, so that the breakdown voltage characteristics are excellent. . That is, in the first sputtering step, reactive sputter deposition is performed in the first chamber in which the inner peripheral side surface is kept conductive, under conditions that oxygen radical species generated by plasma hardly reach the substrate. Since the reaction is performed, the oxidation reaction of the lower electrode 7 is suppressed, and an oxidation reaction layer is hardly generated at the interface with the substrate electrode.

Then, the second sputtering process
In the process, the reactive spa
Since deposition is being performed,
The oxygen deficiency is supplemented with oxygen in the film to be
Good second Ta₂O₅The film 8b is formed. Besides
In the sputtering step of No. 2, the first Ta₂O ₅
Owing to the presence of the film 8a, the oxygen plasma species
The electrode oxidation is suppressed without touching the unit electrode 7.

The first Ta ₂ O ₅ film 8 thus formed
When the capacitance characteristics and the breakdown voltage characteristics of the high dielectric film 8 having a thickness of 20 nm, which is composed of a and the second Ta ₂ O ₅ film 8 b, were measured, oxygen vacancies were found in the second Ta ₂ O ₅ film 8 b. As a result, the bonding state was good and the overall withstand voltage was high, and there was no oxidation reaction layer at the interface with the lower electrode 7, so that the capacitance was high.

On the other hand, in Comparative Example 1, the same gas flow rate (Ar +
O ₂ gas) and subjected to 200 seconds continuously reactive sputtering deposition by sputtering power, the film thickness of 20 nm Ta ₂ O ₅
The film was deposited. Further, as Comparative Example 2, reactive sputtering deposition was continuously performed for 200 seconds in the second chamber at the same gas flow rate and power as in Example 1 to deposit a Ta ₂ O ₅ film having a thickness of 20 nm.

The T thus formed in Comparative Examples 1 and 2
The capacitance and breakdown voltage characteristics of the a ₂ O ₅ film were measured in the same manner as in the example, and the Ta ₂ O ₅ film obtained in Comparative Example 1 was obtained.
_The film No. 5 did not generate an electrode oxide layer (SiO ₂ ) at the interface with the lower electrode and exhibited a high capacitance value similar to that of Example 1, but had oxygen deficiency in the film and had a low withstand voltage Met. In addition, the Ta ₂ O ₅ film obtained in Comparative Example 2 did not have oxygen deficiency in the film and exhibited a high breakdown voltage similar to that of Example 1, but an oxidation reaction layer was formed at the interface with the lower electrode. And
High capacity values could not be obtained.

Embodiment 2 First sputtering is performed in a first chamber in the same manner as in the first embodiment, and a first Ta ₂ O ₅ film is formed on a silicon substrate.
After forming the film to a thickness of 10 nm, a second sputtering was performed in the first chamber.

In the second sputtering step, a high
Frequency voltage to guide oxygen plasma species to the substrate surface.
The first Ta₂O₅The second Ta on the film₂O
₅The film was deposited to a thickness of 10 nm. The sputtering conditions were as follows:
Ar gas flow rate 30 sccm, O ₂Gas flow rate 45 sccm,
4 kW of putter power, reactive sputter deposition for 100 seconds
Session.

The high-dielectric film having a thickness of 20 nm thus formed is formed of the first Ta film formed in the first sputtering step.
₂ O ₅ film is composed from the (thickness 10 nm) and a second Ta ₂ O ₅ film is formed by a second sputtering process (thickness 10 nm), product of the oxidation reaction layer at the interface between the lower electrode Therefore, there was little deterioration in capacitance characteristics and the capacitance value was high. Further, there is no oxygen vacancy in the second Ta ₂ O ₅ film,
Since the bonding state was good, a high withstand voltage value was exhibited.

[0029]

As is apparent from the above description, according to the present invention, there is no oxygen deficiency in the film, excellent pressure resistance characteristics, and no formation of an oxidation reaction layer at the interface with the lower substrate. A high-capacity high-dielectric oxide film can be formed. Therefore, the high dielectric film obtained according to the present invention has a DRA
It can be suitably applied as an insulating film for a capacitor used in a semiconductor memory such as M and a logic LSI.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a state of generation of oxygen plasma inside a first chamber in a first sputtering step in the present invention.

FIG. 2 is a diagram schematically showing a state of generation of oxygen plasma inside a chamber in a second sputtering step in the first invention of the present invention.

FIG. 3 is a diagram schematically showing a state of generation of oxygen plasma inside a chamber in a second sputtering step in the second invention of the present invention.

FIG. 4 is a sectional view showing a structure of a high dielectric film formed in Example 1 of the present invention.

[Explanation of symbols]

1... First chamber, 2... Substrate 3... Second chamber 4... Substrate holder 5... Target 6... Silicon base substrate 7. Electrode, 8 High dielectric film, 8a First Ta ₂ O ₅
Film, 8b... Second Ta ₂ O ₅ film

Claims (6)

[Claims] 1. A method for forming a metal oxide high dielectric film on a substrate, wherein oxygen and an inert gas are provided in a first chamber in which an inner peripheral side surface surrounding a plasma generating portion is kept conductive. A first sputtering step of performing a reactive sputter deposition in a mixed gas atmosphere of forming a first metal oxide film on the substrate, and a second chamber having an insulating inner peripheral side surface, A second sputtering step of performing a reactive sputter deposition in a mixed gas atmosphere of oxygen and an inert gas to form a second metal oxide film on the first metal oxide film. A method for forming a high-dielectric-constant oxide film. 2. A method for forming a metal oxide high dielectric film on a substrate, wherein oxygen and an inert gas are contained in a first chamber in which an inner peripheral side surface surrounding a plasma generating portion is kept conductive. A first sputtering step of forming a first metal oxide film on the substrate by performing reactive sputter deposition in a mixed gas atmosphere of Applying a high-frequency voltage to the substrate and performing reactive sputter deposition while guiding oxygen plasma species to the substrate surface to form a second metal oxide film on the first metal oxide film. And a method of forming a high dielectric oxide film. 3. The method for forming a high dielectric oxide film according to claim 2, wherein said second sputtering step is performed in said first chamber after said first sputtering step. 4. The method according to claim 1, wherein the metal oxide is Ta, Ti, Zr,
The high dielectric oxide film according to claim 1, wherein the high dielectric oxide film is an oxide of one or more metals selected from Hf, Pb, Ba, Sr, and Al. Formation method. 5. In the first sputtering step, Ta, Ti, Zr, Hf, Pb, Ba, Sr, Al
5. The method for forming a high dielectric oxide film according to claim 4, wherein the reactive sputter deposition is performed using one or more metals selected from the group consisting of: 6. In the second sputtering step, Ta, Ti, Zr, Hf, Pb, Ba, Sr, Al
5. The method for forming a high dielectric oxide film according to claim 4, wherein the reactive sputter deposition is performed using one or more metals selected from the group consisting of: