JPH0260157A - Semiconductor device - Google Patents

Abstract

PURPOSE:To prevent reduction in capacity attributable to such a transition layer as an SiOx layer by a method wherein a conductive nitrogen compound film is formed on the top surface of a silicon substrate and then an insulating metal oxide film is formed thereon. CONSTITUTION:An insulating film 2 is selectively formed on a silicon substrate 1, and then a high concentration impurity region 3 is formed. Next, a conductive nitrogen compound film 4 is formed by sputtering, to be subjected to selective etching for the retention of some of the film 4 in a specified region. An insulating metal oxide film 5 is formed by sputtering on the film 4, on which oxide film 5 an electrode 6 is formed in a specified region. The result is a structure wherein a capacitor is constituted of the film 4 serving as the lower electrode, the film 5 serving as a dielectric film, and the electrode 6 as the upper electrode. With an insulating metal oxide film being formed after the formation of a conductive nitrogen compound film, such a transition layer as an SiOx film is not to be formed, which prevents capacity from reduction.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a semiconductor device, and in particular, the present invention relates to a semiconductor device, and in particular, the structure of a capacitor part uses a silicon substrate, a polysilicon electrode, or a silicide electrode as a base electrode, and a metal oxide film as a dielectric material. The present invention relates to a semiconductor device configured using.

[Conventional technology]

In a semiconductor device such as a DRAM (dynamic random access memory) that has a capacitor as a component, it is important to reduce the area of the capacitor part as much as possible in order to increase the density of the semiconductor device. be.

In order to reduce the area occupied by the capacitor, the conventional 5i
It is advantageous to use a dielectric material with a larger permittivity than f2 or Si3N4, and for this reason Ta oxide, Ti
Attempts have been made to use metal oxide films made of oxides, Zr oxides, Hf oxides, etc., and films made of ferroelectric materials such as BaTi0°. Methods for forming these dielectric films include: (1) forming a metal film on the substrate surface by sputter deposition using a metal material such as Ta, Ti, Zr, or Hf as a target, and then oxidizing it; (2) using sputter deposition with oxygen; A method of depositing a metal oxide film on a substrate in an atmosphere, or a method of depositing a metal oxide film on a substrate by CVD method, etc. are used.

[Problem to be solved by the invention]

When a film made of an insulating metal oxide such as Ta oxide or Ti oxide is formed on single crystal silicon or polycrystalline silicon (polysilicon) electrodes, the high capacitance value that should originally be obtained decreases. There is a drawback. This phenomenon becomes particularly noticeable as the metal oxide film becomes thinner.

This is caused by the formation of a low dielectric constant transition layer (relative dielectric constant about 4) such as SiOx between the gold FiJ film and the silicon or polysilicon electrode. In other words, the observed capacitance value is the value that is the series connection of the capacitance of the metal oxide film and the capacitance of the transition layer.If the thickness of the metal oxide film is thin and the capacitance of the film is large, the observed capacitance value This is because the value is largely dominated by the capacitance of the transition layer, which has a small capacitance.

The reason why a transition layer is formed at the interface between silicon and metal oxide film is that metal oxide film easily releases oxygen (easily reduced).
When it comes into contact with an active substance that is easily oxidized, such as silicon, it releases oxygen, and as a result, a SiOx layer is formed at the interface.

According to high-resolution cross-sectional observation using a transmission electron microscope, the thickness of this transition layer is extremely thin by 20 to 35 people. However, for example, the dielectric constant is 25. If a metal oxide film with a thickness of 100% is formed, the observed capacitance value will be 45% or less compared to the case without a transition layer. Therefore, when a metal oxide film is formed on silicon, the property of the metal oxide film as a film with a high dielectric constant cannot be utilized.

As one means for improving the above-mentioned problem of the transition layer, a metal oxide film having insulating properties is provided on an electrode thinning film having a lower activity instead of silicon, which is easily oxidized. That is, once WSi2 is placed on the silicon substrate,
．． MoSi2. After a metal silicide film such as TiSi2 is provided, an insulating metal oxide film is formed. However, since metal silicide contains silicon as a composition, it is necessary to keep the temperature of the process after film formation below 350° C. in order to prevent reaction with the metal oxide film. Such limited conditions have the drawback of severely restricting the fabrication of semiconductor devices and limiting their applications.

[Means to solve the problem]

In the semiconductor device of the present invention, a film made of a conductive nitrogen compound or a metal compound is provided on a silicon substrate or a polysilicon electrode or a metal silicide electrode, and then a film made of an electrically conductive nitrogen compound or a metal compound is formed as a dielectric. Provide an oxide film,
Next, it has a capacitor configured by providing an electrode.

Since the insulating metal oxide film is in contact with a conductive film made of a nitrogen compound or a metal compound and has no contact with silicon, a transition layer such as SiOx is not formed. Therefore, it is possible to realize a large nitrogen capacitance that is originally provided by an insulating metal oxide film.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a diagram illustrating a cross-sectional structure of a capacitor according to a first embodiment of the present invention. In the figure, 1 is a silicon substrate, 2 is an insulating film, 3 is a high concentration impurity region provided on the surface of the silicon substrate 1 and is of the opposite type to the substrate, 4 is a film of a nitrogen compound or metal compound having conductivity, and 5 6 indicates an insulating metal oxide film, and 6 indicates an electrode. The capacitor is constructed using a conductive nitrogen compound or metal compound film 4 as a base electrode, an insulating metal oxide film 5 as a dielectric, and an electrode 6 as an upper electrode.

In this embodiment, the conductive nitrogen compound or metal compound film 4 is connected to the high concentration impurity region 3 provided on the surface of the silicon substrate 1.
The capacitor functions by applying a voltage between the electrode 6 and the electrode 6.

The method for forming the capacitor is to selectively provide the film 2 on the surface of the silicon substrate 1 using a well-known technique, and then form the high concentration impurity region 3 using a thermal diffusion or ion implantation technique. Next, a nitrogen compound film having conductivity such as TiNx, WNx or TiW, AuSn, A
A metal compound film 4 such as u5nAj7 is formed using a method such as sputter deposition or chemical vapor deposition.

The preferred thickness of the conductive metal oxide film is 200 mm.
~1000 people. Next, the film 4 is selectively etched using well-known techniques to leave the film in desired areas. Next, an insulating metal oxide film 5 such as T a gos, Z r 02 #Hf 02 or B a T i O3 is formed using a method such as sputter deposition or chemical vapor deposition. Next, the electrode 6 is formed in a desired region, and the capacitor of this embodiment is formed. In the capacitance of the above-described structure, the conductivity type of the high concentration impurity region 3 may be the opposite type to the silicon substrate 1 or the same type, and the selection thereof is free. Furthermore, the high concentration impurity region 3 may not be provided and may be brought into direct contact with the silicon substrate 1.

In the structure of the container shown in FIG. 1, the conductive nitrogen compound or metal compound film 4 is provided on the surface of the high concentration impurity region 30 and a part of the surface of the insulating film 2. In order to avoid forming a transition layer between the target silicon substrate and the silicon substrate, a conductive nitrogen compound or metal compound film 4 may be provided only on the surface of the high concentration impurity region 30, as shown in FIG. Needless to say.

FIG. 3 is a diagram illustrating a cross-sectional structure of a capacitor according to a second embodiment of the present invention. In the figure, the same symbols as in FIG. 1 indicate the same materials or substances having the same function, and 7 indicates a polysilicon electrode.

The capacitance of this structure is composed of a conductive nitrogen compound or metal compound film 4 provided on the surface of the polysilicon electrode 7, an insulating metal oxide film 5, and an electrode 6. Since the conductive metal oxide film 4 is in contact with the polysilicon electrode 7, the voltage applied to the polysilicon electrode is directly applied to the conductive metal oxide film 4.

FIG. 4 is a cross-sectional view for explaining the third embodiment of the present invention, and shows a cross-sectional structure when the capacitor is applied to a DRAM (dynamic random access memory). In the figure, the same symbols as in FIG. 1 are the same substances or substances having the same function, 21 and 22 are insulating films,
31 and 32 are high concentration impurity regions, 61 is an electrode, 62
72 represents a bit electrode, and 72 represents a word electrode.

The capacitor of this structure is composed of a conductive nitrogen compound or metal compound film 4, an insulating metal oxide film 5, and an electrode 61. The conductive nitrogen compound or metal compound film 4 is in contact with the high concentration impurity region 32, and the voltage applied to the high concentration impurity region 32 is applied to the conductive metal oxide film 4.

FIG. 5 is a cross-sectional view showing a fourth embodiment of the present invention, and shows a cross-sectional structure when the capacitor is applied to a DRAM of another structure. In the figures, the same symbols as in FIGS. 3 and 4 indicate the same substances or substances having the same functions.

In this structural capacitance, the conductive nitrogen compound or metal compound film 4 is in contact with the polysilicon electrode 7, and the polysilicon electrode 7 is in contact with the high concentration impurity region 32, so that it is not added to the high concentration impurity region 32. The voltage is directly applied to the polysilicon electrode 7 and the conductive nitrogen compound or metal compound film 4.

FIG. 6 is a cross-sectional view showing a fifth embodiment of the present invention, and shows a cross-sectional structure when applied to a DRAM of another structure. In the figure, the same symbols as in FIGS. 1 and 4 are the same substances or substances having the same function, 33 is a high concentration impurity region of the same type as the silicon substrate 1, and 75 is a buried electrode.

The structural capacitance forms a groove on the surface of the silicon substrate l,
A capacitance is formed on the side and bottom walls of the groove. The structure of the inner wall of the groove is such that a conductive nitrogen compound or metal compound film 4 is provided on the surface of a silicon substrate on which a high concentration impurity region 33 is formed, and then an insulating metal oxide film 5 is provided. Next, a buried electrode 75 is provided to fill the inside of the groove, forming a capacitor.

〔Effect of the invention〕

As explained above, in the present invention, a film of a nitrogen compound or a metal compound having conductivity is once provided on the surface of a silicon substrate, a polysilicon electrode, or a silicide electrode that is active against oxygen, and then a metal oxide film having an insulating property is formed. This has the effect of preventing a decrease in capacity due to the formation of a transition layer such as SiOx. Further, the capacitor of the present invention has excellent heat resistance with both a metal oxide film as a dielectric and a conductive nitrogen compound or metal compound.

No change in electrical properties was observed even at 600°C.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views for explaining the first embodiment of the present invention, FIG. 3 is a cross-sectional view for explaining the second embodiment of the present invention, and FIG. 4 is a cross-sectional view for explaining the second embodiment of the present invention. FIG. 5 is a cross-sectional view of the shaft for explaining the fourth embodiment of the present invention, and FIG. 6 is a cross-sectional view for explaining the fifth embodiment of the present invention. FIG. 1... Silicon substrate, 2... Insulating film,
3...High concentration impurity region, 4...Nitrogen compound or metal compound film having conductivity, 5...
...Insulating metal oxide film, 6...Electrode, 7...Polysilicon electrode, 75...
Implanted electrode. Agent Patent Attorney Uchihara Onsei Zu Tezu

Claims (1)

[Claims] A semiconductor device comprising a capacitor formed by sequentially stacking a conductive film made of a nitrogen compound or a metal compound, an insulating metal oxide film, and an electrode on a silicon or metal silicide layer. .