JP2000323678A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a capacitor device whole insulating film of a metal oxide film is covered with an upper electrode formed of a metal nitride film by simplifying the manufacturing process, improving the accuracy of working and preventing degradation of device characteristics. SOLUTION: An insulating film 2 in which a hole as upper electrode forming region of a capacitor device is formed on a semiconductor substrate 1, and the upper electrode 3 of the capacitor device is formed in the opening of the insulating film 2. A material gas of organic metal base is intermittently supplied to the surface of the semiconductor substrate 1 for selectively depositing a insulating film 4 of metal oxide film only on the surface of the lower electrode 3. At the time of deposition, the insulating film 4 is heat treated in an oxide atmosphere. By heat treatment, the insulating film 4 changes is conductive property to its original insulating property. A capacitor device is obtained by forming an upper electrode 5 of metal nitride film. Since the insulating film 4 is selectively deposited only on the surface of the lower electrode 3, manufacturing process can be simplified and the accuracy of working can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a capacitive element of a dynamic random access memory (hereinafter referred to as DRAM). The present invention relates to a method for manufacturing a DRAM using a high dielectric constant film.

[0002]

2. Description of the Related Art In the field of DRAM, there is a demand for a reduction in chip area and an increase in recording density due to miniaturization.
In recent years, as the miniaturization progresses, the area occupied by the charge storage portion of the DRAM has been reduced, and it has become extremely difficult to secure the amount of charge storage required for the operation of the DRAM. As a countermeasure against such a shortage of the capacitance of the capacitor, a metal oxide having a higher relative dielectric constant than a silicon oxide film or a silicon nitride film conventionally used as a material for a capacitor insulating film, for example, tantalum oxide, barium oxide / strontium / titanium compound Attempts have been made to replace them. This makes it possible to store a larger amount of electric charge in the same area,
The AM capacitor can be further miniaturized.

[0003]

However, when the metal oxide film is exposed to a reducing gas such as hydrogen or silane (silicon hydride), the metal oxide film is easily reduced and becomes a metal excess composition. It shows electrical conductivity, and a problem arises in that charge cannot be stored in a capacitor due to current leakage. The reducing gas after the formation of the capacitive element is supplied from, for example, a hydrogen-containing source gas used for depositing an interlayer insulating film, or hydrogen used for a heat treatment for reducing the resistance of an aluminum wiring.

FIG. 2 is a process sectional view showing a conventional method for manufacturing a semiconductor device. First, as shown in FIG. 2A, on a semiconductor substrate 1 using a silicon substrate, an insulating film 2 having an opening in a region where a lower electrode of a capacitor is formed is formed.
A conductive lower electrode 3 is formed in the opening of the insulating film 2. Next, as shown in FIG. 2B, a capacitor insulating film 4 made of a metal oxide film and an upper electrode 5 are stacked and deposited on the entire surface, and the resist 6 is patterned. Subsequently, as shown in FIG. 2C, the capacitive insulating film 4 and the upper electrode 5 are collectively etched using the resist 6 as a mask to obtain a capacitive element. However, in the capacitor having the conventional structure shown in FIG. 2C (for example, the same as that described in Japanese Patent Application Laid-Open No. 7-235639), the end side wall of the capacitor insulating film 4 made of a metal oxide film is exposed. And the ingress of reducing gas is easy.

In order to prevent the end side wall of the capacitive insulating film 4 from being exposed, FIG. 3D and FIG.
As shown in the publication, it is necessary to completely cover the capacitance insulating film 4 made of a metal oxide film with the upper electrode 5 made of a metal nitride film. FIG. 3 is a process sectional view showing another conventional method for manufacturing a semiconductor device. In this method, FIG.
As shown in FIG. 7, after the capacitive insulating film 4 is deposited, a resist 7 is formed.
The capacitor 7 is once etched using the resist 7 as a mask (FIG. 3B), and as shown in FIG. 3C, after the upper electrode 5 is deposited, the resist 8 is patterned. Since a capacitor is obtained by etching, a complicated process is required as compared with the manufacturing method shown in FIG. The increase in the number of times of mask alignment increases the cost, and technically, it is difficult to manufacture a fine pattern with high accuracy. Further, a resist 7 is deposited on the capacitance insulating film 4 and the capacitance insulating film 4
There is also a problem of deterioration of device characteristics due to contamination of the interface between the electrode and the upper electrode 5.

Therefore, an object of the present invention is to prevent the capacitance insulating film made of a metal oxide film from becoming conductive by exposure to a reducing gas, so that the capacitance insulating film is covered with an upper electrode made of a metal nitride film. An object of the present invention is to provide a method for manufacturing a semiconductor device capable of manufacturing a capacitor by simplifying a process, improving processing accuracy, and preventing deterioration of element characteristics.

[0007]

According to a method of manufacturing a semiconductor device of the present invention, a first step of forming a conductive film serving as a lower electrode of a capacitor in an opening of an insulating film having an opening formed on a semiconductor substrate is provided. And a second step of selectively depositing a conductive metal oxide film only on the surface of the conductive film by intermittently supplying an organometallic source gas in a vacuum on the semiconductor substrate; A third step of reforming the metal oxide film into an insulating metal oxide film by heat-treating the metal oxide film in an oxidizing atmosphere; and forming a metal nitride film serving as an upper electrode of the capacitor element so as to cover the insulating metal oxide film. And forming a fourth step.

According to this manufacturing method, in the production of a capacitive element, a metal oxide film serving as a capacitive insulating film is intermittently supplied on a semiconductor substrate in a vacuum to form a metal oxide film serving as a capacitive insulating film. Since it can be selectively deposited only on the surface of the conductive film) and can be formed in a self-aligned manner without etching a fine pattern, processing accuracy can be improved. Further, since the capacitor insulating film is formed without using lithography and etching, the process can be simplified. Further, since the deposition of the capacitor insulating film and the deposition of the upper electrode are performed successively, the interface between the capacitor insulating film and the upper electrode is not contaminated, and deterioration of the capacitor can be prevented.

It is preferable to use a metal oxide containing any one of tantalum, bismuth, strontium, titanium and barium for the metal oxide film.

It is preferable to use a metal nitride containing any one of titanium, vanadium, chromium, zirconium, niobium, molybdenum, hafnium, tantalum, and tungsten for the metal nitride film.

[0011]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a process sectional view of a method of manufacturing a capacitive element according to an embodiment of the present invention.

First, using a well-known method, as shown in FIG. 1A, an insulating film 2 (thickness) of silicon oxide is formed on a semiconductor substrate 1 made of a silicon substrate. Is formed, for example, 20 nm).
A lower electrode 3 of a capacitive element made of a conductive film in an opening of the insulating film 2
To form As this conductive film, for example, a doped silicon film (thickness: for example, 100 nm) is formed. The insulating film 2 is for element isolation.

Next, as shown in FIG. 1B, an organometallic source gas (for example, pentaethoxy tantalum) is intermittently supplied onto the semiconductor substrate 1 in a vacuum of 30 Pa or less.
A capacitance insulating film 4 made of a metal oxide film (for example, tantalum oxide) is selectively deposited only on the surface of the lower electrode 3. The ratio between the supply time of the organometallic source gas and the interruption time is 1: 2. The supply time is 20 seconds to 1 minute, and the interruption time is 40 seconds to 2 minutes corresponding to the supply time. The temperature range in which the deposition is performed is 500 ° C. or less.

The surface of the lower electrode 3 made of a doped silicon film has many electrons (hereinafter referred to as dangling bonds) that do not contribute to the bonding of atoms, and these dangling bonds act as catalysts for the decomposition of pentaethoxy tantalum. effective. Therefore, pentaethoxy tantalum is easily decomposed, and tantalum oxide is deposited at a high deposition rate. On the other hand, dangling bonds are small on the silicon oxide insulating film 2, pentaethoxy tantalum is hardly decomposed, and tantalum oxide is not deposited. Even if it is deposited, the attached atoms are re-evaporated due to the intermittent interruption of the supply of pentaethoxy tantalum, so that selective deposition of tantalum oxide is possible. In addition, since tantalum oxide is mixed with impurities such as carbon and hydrogen because of the use of organometallic raw material gas, the original characteristics of tantalum oxide are insulators, but it becomes a conductor immediately after deposition. I have. Therefore, dangling bonds also exist on the tantalum oxide capacitance insulating film 4, and even if the film thickness increases, the selective deposition is maintained. Then, tantalum oxide having a desired film thickness (thickness: for example, 10 n
m). The thickness of tantalum oxide is 5 nm or more and 20
nm or less.

Next, the deposited capacitive insulating film 4 is subjected to a heat treatment in an oxidizing atmosphere such as oxygen, oxygen mononitride, or oxygen dinitride. The conditions of the heat treatment are 700 ° C. or more and 30 seconds or more. By this heat treatment, carbon and hydrogen mixed in the capacitive insulating film 4 during the deposition are removed, and oxygen is inserted into lattice positions of the removed atoms. As a result, the capacitance insulating film 4 is modified from conductivity to insulation, which is the original characteristic.

Next, as shown in FIG. 1C, an upper electrode 5 made of a metal nitride film (for example, titanium nitride) is deposited,
A resist 6 is patterned thereon, and the upper electrode 5 is etched using the resist 6 as a mask.
Is removed, a capacitive element is obtained (FIG. 1D).

As described above, according to the present embodiment, the capacitance insulating film 4 is selectively self-aligned only to the surface of the lower electrode 3.
Therefore, the number of steps is smaller than the case where the capacitive insulating film 4 is deposited over the entire surface and etched as shown in FIG.
In addition, it can be formed with high accuracy. In addition, since the deposition of the capacitor insulating film 4 and the deposition of the upper electrode 5 are performed continuously, the capacitor insulating film 4 can be formed without contaminating the interface between the capacitor insulating film 4 and the upper electrode 5. Degradation can be prevented. Further, since the capacitor insulating film 4 is completely covered with the upper electrode 5 of the metal nitride film and the side wall end of the capacitor insulating film 4 is not exposed, it can be protected from exposure to the reducing gas. For example, even if an interlayer insulating film is deposited with a source gas containing a reducing gas after forming a capacitive element, or a hydrogen heat treatment is performed after forming an aluminum wiring, the capacitive insulating film 4 made of a metal oxide film is reduced. In addition, it is possible to prevent deterioration of electrical characteristics.

In the present embodiment, the capacitance insulating film 4 has been described using tantalum oxide as an example. However, barium strontium titanate (BST) or the like may be used, and tantalum, bismuth,
Needless to say, a similar effect can be obtained if a metal oxide film contains any one of strontium, titanium, and barium. Capacitive insulating film 4 of any metal oxide film
Is formed, an organic metal-based source gas, that is, an organic metal gas containing a metal constituting the capacitive insulating film 4 and an oxidizing gas are intermittently supplied onto the semiconductor substrate 1 in a vacuum, so that self-alignment is achieved. Can be formed. As a raw material gas of organic metal-based, other pentaethoxytantalum, such as tetra-isopropoxy titanium _{{Ti (i-OC 3 H} 7)
₄ ｝, bisdipivaloyl methanate barium ｛Ba (D
PM) ₂ ; Ba (O ₂ C ₁₁ H ₁₉ ) ₂ }, bis dipivaloyl methanato strontium {Sr (DPM) ₂ ; Sr
(O ₂ C ₁₁ H ₁₉ ) ₂ }.

Although titanium nitride has been described as an example of the upper electrode 5, tantalum nitride, tungsten nitride or the like may be used. It goes without saying that a similar effect can be obtained if the metal nitride film contains the same.

[0020]

As is apparent from the above description, according to the method of manufacturing a semiconductor device of the present invention, in manufacturing a capacitor, an organometallic source gas is intermittently supplied to a semiconductor substrate in a vacuum. Thus, a metal oxide film serving as a capacitor insulating film can be selectively deposited only on the surface of the lower electrode (conductive film), and a fine pattern can be formed in a self-aligned manner without etching. Processing accuracy can be improved. Further, since the capacitor insulating film is formed without using lithography and etching, the steps can be simplified. Further, since the deposition of the capacitive insulating film and the deposition of the upper electrode are performed successively, the interface between the capacitive insulating film and the upper electrode is not contaminated, and deterioration of the capacitive element can be prevented.
In the capacitive element formed according to the present invention, the capacitive insulating film made of the metal oxide film is covered with the upper electrode of the metal nitride film, and the side wall end of the capacitive insulating film is not exposed, so that it is protected from exposure to the reducing gas. For example, even if an interlayer insulating film is deposited with a source gas containing a reducing gas after forming a capacitive element, or a hydrogen heat treatment is performed after forming an aluminum wiring, a capacitive insulating film made of a metal oxide film can be reduced. And the deterioration of the electrical characteristics can be prevented.

[Brief description of the drawings]

FIG. 1 is a process sectional view illustrating a method for manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a process cross-sectional view illustrating a conventional method for manufacturing a semiconductor device.

FIG. 3 is a process sectional view illustrating another conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

 Reference Signs List 1 semiconductor substrate 2 insulating film 3 lower electrode (conductive film) 4 capacitance insulating film (metal oxide film) 5 upper electrode (metal nitride film)

Claims (3)

[Claims] A first step of forming a conductive film serving as a lower electrode of a capacitor in the opening of an insulating film having an opening formed on a semiconductor substrate; A second step of selectively depositing a conductive metal oxide film only on the surface of the conductive film by intermittently supplying the material gas of the above, and heat treating the conductive metal oxide film in an oxidizing atmosphere. And a fourth step of forming a metal nitride film serving as an upper electrode of the capacitive element so as to cover the insulating metal oxide film. And a method for manufacturing a semiconductor device. 2. The method according to claim 1, wherein the metal oxide film is made of a metal oxide containing any one of tantalum, bismuth, strontium, titanium, and barium. 3. The semiconductor according to claim 1, wherein the metal nitride film is made of a metal nitride containing any one of titanium, vanadium, chromium, zirconium, niobium, molybdenum, hafnium, tantalum, and tungsten. Device manufacturing method.