JPH05235264A - Semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the capacity deterioration of the capacitor dielectric film of a semiconductor device which has the capacitor as a constituting element and miniaturizing the device by using an electricity conducting oxide film as the electric material of the capacitor. CONSTITUTION:When the device is applied to a dynamic random access memory device, a source 2, a drain 14, a pit line 3 for impressing a voltage on a transistor, a silicon oxide film 4 for element separation, a gate oxide film 5 which is to be a transfer gate and a word line 6 for applying bias on the film 5 are provided on a silicon substrate 1. A capacitor bottom electrode 7, a metal silicide film 8, an electricity conducting oxide film 9, a capacitor top electrode 11, a capacitor dielectric film 12 and an interlayer insulating film 13 are provided. Thus, the electricity conducting oxide film 9 is provided between the bottom electrode 7 and the dielectric film 12 so as to prevent the generation of low-dielectric constant oxide on the interface between the films 9 and 12 and the capacity deterioration of the capacitor is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device.

[0002]

2. Description of the Related Art FIG. 2 is a sectional view showing a part of a memory cell of a conventional dynamic random access memory device, in which 1 is a silicon substrate, 2 is a source, 14 is a drain, 3 is a bit line, and 4 is a bit line. Is a silicon oxide film for element isolation, 5 is a gate oxide film, 6 is a word line, 7 is a capacitor lower electrode made of polysilicon, 11 is a capacitor upper electrode, 12 is a capacitor dielectric film, and 10 is a capacitor lower electrode. 7 and capacitor upper electrode 11 and capacitor dielectric film 12
Silicon oxide films containing low-dielectric-constant silicon generated at the interfaces with and 13 insulate conductive parts such as the bit line 3, the gate oxide film 5, the capacitor lower electrode 7, and the low-dielectric-constant silicon oxide film 10. Is an interlayer insulating film for.

Next, the operation will be described.

A power supply voltage is applied to the bit line 3, and when a voltage is applied to the gate oxide film 5 which is the transfer gate in this state, the transistor is turned on, and the aluminum wiring which is the bit line is connected to the source. 2. A power supply voltage is applied to the capacitor lower electrode 7 via the drain 14. A capacitor dielectric film composed of a capacitor lower electrode 7 and a capacitor upper electrode 11 in which a potential difference is generated here.
12 is polarized, and charges are accumulated in the capacitor lower electrode 7 and the capacitor upper electrode 11.

[0005]

The conventional dynamic random access memory device is constructed as described above, and when a material having a higher dielectric constant than silicon dioxide is used for the capacitor dielectric film 12, it is made of polysilicon. The low dielectric constant silicon oxide film 10 made of silicon dioxide existing at the interface between the capacitor lower electrode 7 and the capacitor dielectric film 12 lowers the dielectric constant of the entire capacitor and is accumulated in the capacitor lower electrode 7 and the capacitor upper electrode 11. The amount of electric charge generated decreases.

Further, even when a metal material such as tungsten or aluminum or a silicide thereof is used for the lower electrode of the capacitor, the electrode is oxidized in the process of forming the oxide dielectric, and tungsten oxide, aluminum oxide or silicon dioxide is used. Etc. are generated, the charge stored in the capacitor is significantly reduced.

Further, it is difficult to control the film thickness of the very thin interfacial oxide thus produced, and there is a problem that the reproducibility of the process becomes poor.

The present invention has been made to solve the above problems, and an object thereof is to suppress the formation of a low dielectric constant oxide such as silicon oxide at the electrode interface.

[0009]

The present invention relates to a semiconductor device having a capacitor as a constituent element, wherein an electrically conductive oxide film is used as an electrode material of the capacitor.

[0010]

The electrically conductive oxide film, which is the electrode material used in the present invention, is chemically more stable than metal or polysilicon, and has a high dielectric constant directly on the electrically conductive oxide film. By forming the body, a capacitor having a high charge storage capacity can be formed.

[0011]

[Embodiment 1] The present invention will be described below with reference to FIG. 1 showing a dynamic random access memory device using tantalum oxide as a capacitor, which is one embodiment of the semiconductor device of the present invention.

In FIG. 1, 1 is a silicon substrate, 2 is a source, 14 is a drain, 3 is a bit line for applying a voltage to a transistor, 4 is a silicon oxide film for element isolation, and 5 is a transfer gate of the transistor. A gate oxide film 6 which becomes a transfer gate, a word line for applying a bias to the gate oxide film 5 which becomes a transfer gate, 7 a capacitor lower electrode made of polysilicon or the like, 8 a metal silicide film made of titanium silicide or the like, 9 Is La
An electrically conductive oxide film made of TiO ₃ or the like, 11 a capacitor upper electrode, 12 a capacitor dielectric film made of tantalum oxide, 13 a conductive part such as a bit line 3, a gate oxide film 5 and a capacitor lower electrode 7. An interlayer insulating film 13 for insulation.

In the above semiconductor device, the metal silicide film does not necessarily need to be present. Especially when a metal contained in the oxide electrode is used for the lower electrode 7, a material having excellent oxidation resistance such as platinum is used as the lower electrode. When used for the electrode 7, the metal silicide film is unnecessary.

As the semiconductor device of the present invention having a capacitor as a constituent element, in addition to the dynamic random access memory device, an EEPROM, CCD, CPU
Etc.

In a conventional dynamic random access memory device using tantalum oxide, a capacitor dielectric film is formed on a capacitor lower electrode 7 made of polysilicon or the like.
Since 12 was directly formed, oxidation of the capacitor lower electrode 7 was unavoidable, and the capacitance of the capacitor dielectric film 12 was reduced, while the electrically conductive oxide film 9 having conductivity such as LaTiO ₃ was used. In a dynamic random access memory which is an example of the present invention having a capacitor between the capacitor lower electrode 7 and the capacitor dielectric film 12, a low voltage is formed at the interface between the capacitor dielectric film 12 and the electrically conductive oxide film 9 during film formation. It is possible to prevent a decrease in the capacitance of the capacitor because an oxide having a dielectric constant is not generated.

An electrically conductive oxide film (upper electrode) existing between the capacitor dielectric film 12 and the capacitor upper electrode 11.
9 has the same effect.

In the present invention, as the oxide electrode material used as the electrically conductive oxide film, the above-mentioned LaTiO 3 is used.
_In addition to ₃ , perovskite oxides represented by the general formula: ABO ₃ (wherein A represents an alkaline earth metal, a rare earth element, and B represents a transition metal) can be mentioned. Specific examples of the perovskite type oxide include SrCo.
O ₃ , La _1-x Sr _x MnO ₃ , La _1-x Sr _x CoO ₃ , L
Examples thereof include aNiO ₃ , CaRuO ₃ , SrRuO ₃ , and SrIrO ₃ .

The oxide electrode material may be a pyrochlore type oxide represented by the general formula: A ₂ B ₂ O ₇ (wherein A and B are the same as in the case of the general formula ABO ₃ ). As a specific example, for example, Pb ₂ Ru ₂ O
₇ and so on.

Further, as the oxide electrode material, MO _x
A simple oxide of a metal represented by the following is mentioned, and specific examples thereof include MoO ₂ , WO ₂ and TiO ₂ .

In addition to the oxides shown in the above specific examples, the oxide electrode material is not particularly limited as long as it is an oxide having a small electric resistance value near the operating temperature of the semiconductor element. Also,
It is not completely stoichiometric and may have oxygen defects.

The film forming method is not particularly limited, and examples thereof include film forming methods such as sputtering, CVD and vapor deposition.

As a concrete film forming method, for example, a case of forming a film by a sputtering method will be explained. A ceramic target of a capacitor material is prepared, RF power is 1 to 10 kW, power supply voltage is 1 kW, and argon gas is used. Pressure 1
A film can be formed by setting the pressure to about Pa and subjecting the target to high frequency sputtering.

The case of forming a perovskite complex oxide of an alkaline earth metal and a transition metal by the CVD method will be described as an example. The dipivaloylmethanate salt of an alkaline earth metal and the transition metal will be described below. It is possible to form a film by vaporizing the alkoxide salt of 1 as a raw material with a bubbler and introducing it into a heated reaction chamber together with an oxidizing gas such as oxygen.

Also, for example, ITO can be formed by a vapor deposition method.
Taking the case of forming a film of (indium tin oxide) as an example, the film can be formed by reactive vapor deposition of indium metal and tin metal in the presence of oxygen.

In any of the examples, it is necessary to keep the substrate at a temperature suitable for film formation.

Further, in the present invention, the metal contained in the electrically conductive oxide film (lower electrode) 9 is provided between the capacitor lower electrode 7 made of polysilicon or the like and the electrically conductive oxide film (lower electrode) 9. By forming a metal silicide film using, it is possible to avoid generation of a low dielectric constant oxide at the interface between the capacitor lower electrode 7 made of polysilicon or the like and the electrically conductive oxide film (lower electrode) 9. This is because when forming a film, an oxide containing the metal is formed on the metal silicide, so that the composition of the interface oxide continuously changes, and an oxide having a low dielectric constant is not generated. This is because a large capacitor capacity can be secured.

A similar effect can be obtained by forming a metal silicide between the capacitor upper electrode 11 and the electrically conductive oxide film (upper electrode) 9.

Specific examples of the metal silicide film include:
LaTiO ₃ as the electrically conductive oxide film (lower electrode) 8
The titanium silicide film can be given when using.

Examples of the metal silicide film include tungsten silicide and tantalum silicide.

Examples of the method for forming the metal silicide film include sputtering and CVD. The sputtering method can be formed under substantially the same conditions as when forming a dielectric film by the sputtering method except that a metal silicide is used as a target.

Taking the case of forming a film by the CVD method as an example, the film formation is carried out by using a metal halide as a raw material, vaporizing it with a bubbler, and introducing it together with a reducing gas such as silane and hydrogen into a heated reaction chamber. it can.

Examples of the capacitor dielectric film used in the present invention include perovskite type oxides such as lead zirconate titanate, strontium titanate, and tantalum oxide, in addition to the tantalum oxide.

[0033]

As described above, according to the present invention, since the metal oxide, which is the electrically conductive oxide film, is used as the electrode material of the capacitor dielectric film, it is possible to prevent the capacitance of the capacitor dielectric film from lowering, and to reduce the device. Can be made smaller.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a random access memory device which is an embodiment of a semiconductor device of the present invention.

FIG. 2 is a cross-sectional view showing a random access memory device which is an example of a conventional semiconductor device.

[Explanation of symbols]

 1 silicon substrate 2 source 3 bit line 4 silicon oxide film 5 gate oxide film 6 word line 7 capacitor lower electrode 8 metal silicide film 9 electrically conductive oxide film 11 capacitor upper electrode 12 capacitor dielectric film 13 interlayer insulating film 14 drain

Claims (2)

[Claims] 1. A semiconductor device having a capacitor as a constituent element, wherein an electrically conductive oxide film is used as an electrode material of the capacitor. 2. The metal silicide contained in the electrically conductive oxide film is sandwiched between a portion made of silicon such as a substrate and the electrically conductive oxide film.
The semiconductor device described.