JPH07263570A - Method for manufacturing dielectric device - Google Patents

Abstract

(57) [Abstract] [Purpose] A method for manufacturing a dielectric device such as a capacitor, which suppresses oxygen defects in an oxide high dielectric material that occurs during electrode formation, reduces carrier concentration, and has a good Schottky barrier. (EN) Provided is a dielectric device which forms an interface between an oxide high dielectric and an electrode and has high insulation and large capacitance density. In the step of forming the upper electrode 3 on the oxide high dielectric film 2 formed on the lower electrode 1, Pt, A
Input power of 3W in an atmosphere containing noble metal such as u in oxygen
Sputtering is limited to not more than / cm ² . Further, this electrode is made of a nitride of a refractory metal such as Ti, oxygen is introduced into the sputtering gas at the initial stage of its growth, and the input power is 2 W / c.
Sputtering is limited to m ² or less. After the surface of the oxide high dielectric is cleaned by oxygen plasma treatment, electrodes are continuously formed by the above method. The electrodes can also be formed by vapor deposition in an oxygen atmosphere.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a dielectric device such as a capacitor using an oxide high dielectric material. Sr
High dielectric oxides such as TiO ₃ , BaTiO ₃ and PZT have a dielectric constant of 50 times or more that of SiO ₂ , and by using this as a dielectric film, the capacitance density of the capacitor can be increased and 256Mbit or later. DRAM
It is an indispensable material for miniaturization in the above, or for realizing a large-capacity capacitor or the like to be incorporated in an IC chip. In these fields of application, high dielectric films are required to have high capacitance density as well as reduced leakage current and improved dielectric breakdown voltage.

[0002]

2. Description of the Related Art Conventionally, when a metal is sputtered on an oxide high dielectric as an electrode, the surface of the dielectric is damaged by the spatter, and oxygen defects are generated, which deteriorates the insulation of the dielectric. There is a problem, and on the other hand, when metal is deposited at low energy by vacuum deposition to avoid damage to the surface of the dielectric, the low dielectric constant layer formed by the reaction with the atmosphere on the surface of the dielectric is removed. Therefore, there is a problem that the dielectric constant of the whole is lowered.

[0003]

Therefore, in the prior art,
It was difficult to solve the problem of insulation and the problem of the low dielectric layer on the surface at the same time.

The present invention suppresses oxygen defects in the oxide high dielectric which occurs during electrode formation to reduce the carrier concentration, and forms an interface between the oxide high dielectric having a good Schottky barrier and the electrode. Then, it is an object of the present invention to provide a method for manufacturing a dielectric device such as a capacitor having a high insulating property and a large capacitance density.

[0005]

In the method of manufacturing a dielectric device according to the present invention, in the step of forming an electrode on an oxide high dielectric, a noble metal is supplied in an oxygen-containing gas atmosphere and an input power is applied. The step of sputtering was adopted while limiting to 3 W / cm ² or less. In this case, the precious metal electrode material is P
It can be t or Au.

In another method of manufacturing a dielectric device according to the present invention, in the step of forming an electrode on an oxide high dielectric, the electrode material is a nitride of a refractory metal such as Ti and the initial growth stage. A process of introducing oxygen into the sputtering gas and limiting the input power to 2 W / cm ² or less for sputtering was adopted.

In these cases, the electrode can be continuously formed after cleaning the surface of the oxide high dielectric material by oxygen plasma treatment. Further, instead of sputtering, the electrodes can be formed by vapor deposition under a low pressure oxygen atmosphere.

[0008]

The bulk material of oxide high dielectric such as SrTiO ₃ and BaTiO ₃ has been conventionally used as a ceramic varistor, and when a voltage (threshold voltage) higher than a certain value is applied, the current suddenly increases. It has the property of starting to flow.

This characteristic is derived from the physical property of the crystal grain boundary of the oxide high dielectric or the interface between the oxide high dielectric and the electrode. Especially in the case of a thin film, the latter Schottky barrier is mainly used. Limits the current.

FIG. 7 is an explanatory diagram of the Schottky barrier at the interface between the oxide high dielectric and the electrode. As shown here, since the Schottky barrier is formed at the interface between the oxide high dielectric and the electrode, the flow of electrons from the electrode to the oxide high dielectric is blocked.

However, when the electrode is formed by sputtering, oxygen atoms near the surface of the oxide high dielectric are knocked out to generate oxygen defects, which serve as donors in the oxide high dielectric and increase the carrier concentration. As a result, the resistivity between the oxide high dielectric and the electrode decreases, and the junction between the oxide high dielectric and the electrode loses the Schottky barrier and becomes ohmic, so the current is not limited and the leak current increases. To do.

On the other hand, in the present invention, in order to prevent oxygen deficiency on the surface of the oxide high dielectric material due to electrode formation,
Sputtering for forming the electrodes is performed in an atmosphere containing oxygen while limiting the input power to 3 W / cm ² or less.

As a result, oxygen defects do not occur near the surface of the oxide high dielectric, the carrier concentration is kept low, the current is limited by the Schottky barrier, and the resistivity of the oxide high dielectric increases. Since the voltage applied to the junction decreases, the Schottky barrier is less likely to be destroyed. Also, the low dielectric constant layer on the surface of the oxide high dielectric is removed by low power sputtering, so that the apparent dielectric constant found in dielectric devices such as conventional capacitors in which electrodes are formed by vapor deposition is used. It also solves the problem of the decrease of.

[0014]

EXAMPLES Examples of the present invention will be described below. (First Embodiment) FIG. 1 is a diagram for explaining the structure of a capacitor according to the first embodiment. In the figure, 1 is a lower electrode, 2 is a high dielectric oxide film, and 3 is an upper electrode.

The capacitor of this embodiment is platinum (Pt).
After depositing an oxide high-dielectric film 2 of SrTiO ₃ having a thickness of 1000 to 2000 Å on the lower electrode 1 made of, for example, 400 in an atmosphere (oxygen) of 1 atm.
Annealing is performed at 30 ° C. for 30 minutes, and platinum (Pt) having a thickness of 1000 Å is formed as an upper electrode 3 on the gas atmosphere containing oxygen (Ar: 4.5 mTorr, O ₂ : 0.5 mTorr).
In r), it is formed by sputtering with an input power of ² W / cm ² .

FIG. 2 is a leakage current characteristic diagram of the capacitor of the first embodiment. In this figure, in addition to the leakage current characteristic a of the capacitor of this example, the input power at the time of sputtering the upper electrode is 2 W / cm ² , but when oxygen gas is not introduced b and oxygen gas However, when the input power for sputtering is as high as 5 W / cm ² , c is shown for comparison.

It has been shown that the leakage current of the capacitor of this embodiment sputtered in Ar + O ₂ and at low power has a particularly small leakage current on the negative bias side. It is considered that this is because oxygen defects near the interface of the upper electrode are reduced to generate a Schottky barrier and limit the reverse current.

FIG. 3 is an explanatory diagram of the oxygen concentration distribution of a conventional oxide high dielectric film. This figure shows the result of SIMS measurement of the oxygen distribution of a sample sputtered in an atmosphere of Ar without introducing oxygen gas when forming the upper electrode.

FIG. 4 is an explanatory view of the oxygen concentration distribution of the oxide high dielectric constant film of the first embodiment. This figure shows the result of SIMS measurement of the oxygen distribution of a sample sputtered in an Ar atmosphere into which oxygen gas was introduced when forming the upper electrode according to the manufacturing method of this example.

As shown in FIG. 4, oxygen is piled up at the interface between the oxide high dielectric film 2 and the upper electrode 3 to increase the oxygen concentration. In this embodiment, the input power was set to 2 W / cm ² , but if it is 3 W / cm ² or less, substantially the same effect as described above is obtained.

(Second Embodiment) In the method of manufacturing an oxide high dielectric material of this embodiment, TiN is used as the upper electrode instead of Pt or Au. Similar to the capacitor of the first embodiment, after the lower electrode and the dielectric film are formed, a Ti target is used for the upper electrode and a gas containing oxygen (Ar: 3.
8 mTorr, N ₂ : 0.8 mTorr, O ₂ : 0.5
² mW / cm ² of TiON film at 1.2 W / cm 2
00Å growth, then stop the supply of oxygen, 5W /
A TiN film is grown to 800 Å in cm ² .

FIG. 5 is a leakage current characteristic diagram of the capacitor of the second embodiment. In this figure, in addition to the leakage current characteristic a of the capacitor of this example, the input power for sputtering the upper electrode is 1.2 W / cm ² , but oxygen gas was not introduced at the initial stage. For comparison, case b and case c in which oxygen gas is introduced but the input power for sputtering is as high as 5 W / cm ² are shown.

The leak current of the capacitor of this example sputtered in an Ar + O ₂ + N ₂ atmosphere and at low power has a smaller leak current on the negative bias side than the capacitors manufactured under the other conditions shown for comparison. It is shown.

In this figure, after TiON or TiN is formed by sputtering a, b, and c, a gas containing oxygen (Ar: 3.8 mTorr, N ₂ : 0.8 mTo is used.
rr, O ₂ : 0.5 mTorr), input power 5 W
The reason why the TiON is formed by increasing it to / cm ^{2 is} to increase the input power to obtain the thickness as an electrode in a short time because the growth rate when forming the TiON by applying low power is small. .

In this example, when Ti nitride was formed on the oxide high dielectric by sputtering, oxygen was introduced at the initial stage of growth to make the input power 1.2 W / cm ^2. When the electric power is limited to ² W / cm ² or less, almost the same effect as described above is obtained.

(Third Embodiment) In the method of manufacturing an oxide high dielectric material of this embodiment, the upper electrode is formed by vapor deposition in low-pressure oxygen instead of sputtering.

FIG. 6 is a leakage current characteristic diagram of the capacitor of the third embodiment. This figure shows the leakage current characteristics of a capacitor having an upper electrode formed by depositing gold under a high vacuum of about 1 × 10 ⁻⁷ Torr and a low vacuum of about 1 × 10 ⁻² Torr.

When the upper electrode is formed by the vapor deposition method, the leakage current on the negative bias side is small because the surface of the oxide high dielectric material is less damaged as in the case where the upper electrode is formed by sputtering. The apparent relative permittivity of the oxide high-dielectric substance vacuum-deposited in (1) is as low as ε = 104.

It is considered that this is because the low dielectric constant layer is formed on the oxide high dielectric material and the low dielectric constant layer is not removed. On the other hand, 0.01 (1 × 10 ^-2 )
When vapor deposition is carried out in an oxygen atmosphere of Torr, there is no change in the leak current and the dielectric constant is ε = 187, indicating that this vapor deposition process under low vacuum has the effect of removing the surface layer. In this case, 1 × 10 ⁻³ to 1 × 10
Even when vapor deposition was performed in an oxygen atmosphere in the range of ^-1 Torr, almost the same effect as described above was produced.

Similarly, when the above-mentioned upper electrode is formed by sputtering, it is considered that the effect of removing the low dielectric constant layer is obtained within the range where the surface of the oxide high dielectric material is not damaged. Furthermore, the surface of the oxide high dielectric is treated with oxygen plasma (room temperature, O ₂ : 0.2 Torr, 3 to
This effect can be enhanced by forming an upper electrode after 4 W / cm ² , 5 minutes).

[0031]

As described above, according to the present invention,
By taking measures to suppress oxygen defects that occur in the oxide high dielectric when forming electrodes, the leakage current can be kept low in the practical voltage range, which contributes to the application of the oxide high dielectric to DRAM. There is a lot to do.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a configuration of a capacitor according to a first embodiment.

FIG. 2 is a leakage current characteristic diagram of the capacitor of the first embodiment.

FIG. 3 is an explanatory diagram of an oxygen concentration distribution of a conventional oxide high dielectric film.

FIG. 4 is an explanatory diagram of oxygen concentration distribution in the oxide high dielectric constant film of the first example.

FIG. 5 is a leakage current characteristic diagram of the capacitor of the second embodiment.

FIG. 6 is a leakage current characteristic diagram of the capacitor of the third embodiment.

FIG. 7 is an explanatory diagram of a Schottky barrier at an interface between an oxide high dielectric and an electrode.

[Explanation of symbols]

 1 Lower electrode 2 Oxide high dielectric film 3 Upper electrode

Continuation of the front page (51) Int.Cl. ⁶ Identification code Reference number within the agency FI Technical display location C23C 14/34 N 8414-4K H01G 4/33 H01L 21/31 27/04 21/822 H01L 21/31 D 27 / 04 C

Claims (5)

[Claims] 1. A dielectric film characterized in that, in the step of forming an electrode on an oxide high dielectric material, sputtering is carried out by limiting the input power to 3 W / cm ² or less in a gas atmosphere containing oxygen with a noble metal. Body device manufacturing method. 2. The method for manufacturing a dielectric device according to claim 1, wherein the noble metal electrode material is Pt or Au. 3. In the step of forming an electrode on an oxide high dielectric, the electrode material is a nitride of a refractory metal such as Ti, oxygen is introduced into the sputtering gas at the initial stage of growth, and
A method for manufacturing a dielectric device, characterized in that sputtering is performed while limiting an input power to 2 W / cm ² or less. 4. An electrode is formed by the method according to any one of claims 1 to 3 after cleaning the surface of the oxide high dielectric material by oxygen plasma treatment. A method for manufacturing a dielectric device, comprising: 5. The dielectric device according to claim 1, wherein the electrode is formed by vapor deposition in a low-pressure oxygen atmosphere instead of sputtering. Manufacturing method.