Coating apparatus – Gas or vapor deposition – With treating means
Reexamination Certificate
2002-04-17
2002-10-29
Ghyka, Alexander (Department: 2812)
Coating apparatus
Gas or vapor deposition
With treating means
C118S719000, C118S7230AN, C118S7230MW
Reexamination Certificate
active
06470824
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a manufacturing method of semiconductors, in particular detail, to a method for forming gate insulators in MIS (MOS) semiconductor devices, and to a manufacturing method of semiconductor devices provided with insulator films such as gate insulators on a surface of a silicon substrate.
2. Description of the Related Art
Recently, as MIS (MOS) semiconductors have been patterned finer, extremely thin gate insulators such as approximately 4 nm or less are in demand. So far, for gate insulator material, silicon oxide films (SiO
2
film) have been industrially used that can be obtained by directly oxidizing a silicon substrate by use of a high temperature furnace of approximately 850° C. to 1000° C.
However, when the SiO
2
layer is 4 &mgr;m or less, a leakage current (gate leakage current) flowing the gate insulator increases to cause problems such as an increase of consumption power or an acceleration of deterioration of device property.
In addition, there is such a problem that during formation of a gate electrode, boron contained therein causes alloy spikes in the SiO
2
film to reach the silicon substrate to result in deterioration of semiconductor device property. As one method for solving such a problem, nitride film (SiN film) is under consideration as the gate insulator material.
When the SiN films are deposited by use of CVD method, there occur many incomplete bonds (dangling bond) at the interface with the silicon substrate to result in deterioration of device property. Accordingly, in forming the SiN films, it is considered very promising to directly nitride a silicon substrate by use of plasma. The reason why to nitride directly is to obtain gate insulators of high quality that are less in interface states.
In addition, one reason for using the plasma is to form SiN films at low temperatures. In obtaining SiN films by heating to nitride, high temperatures of 1000° C. or more are necessary. In the process of the heating, dopant is injected into the silicon substrate. The dopant diffuses differentially to cause deterioration of device property. Such methods are disclosed in Japanese Patent Laid-open Application (KOKAI) Nos. SHO 55-134937 and SHO 59-4059.
However, in the case of depositing SiN layers with the plasma, the following problems have been pointed out. That is, ions in the plasma are accelerated by a plasma sheath voltage to bombard the silicon substrate with high energy, thereby so-called plasma damage occurs at interfaces of the silicon substrate or on the silicon substrate to deteriorate the device property.
To this end, a microwave plasma device is disclosed that is provided with a planar-array antenna that is low in electron temperature and has a lot of slits causing less plasma damage.
(Ultra Clean Technology Vol.10 Supplement 1, p.32, 1998, published by Ultra Clean Society).
In this plasma device, the electron temperature is approximately 1 eV or less and the plasma sheath voltage also is several volts or less. Thus, compared with existing plasma. of which plasma sheath voltage is approximately 50 V, the plasma damage can be largely reduced.
However, even when silicon nitride is formed with this plasma device, in the case of forming SiN films by use of direct nitriding method, there is the following problem. That is, in order to obtain interfaces of. good quality of less dangling bond defects by dominantly distributing oxygen only at the interfaces of the silicon substrate, there is a difficulty in regulating film quality at the interfaces with the silicon substrate.
In addition, in employing this plasma device to nitride, nitrogen atoms must diffuse into the silicon substrate to proceed nitriding. That is a slow process to require a long time to give prescribed processing to an object being processed. Accordingly, the objects can not be processed much per unit period to cause difficulties in industrial application. In forming SiN films of a thickness of for instance 4 nm, even under the best adjusted plasma conditions of such as pressure and microwave power, it takes approximately 5 min or more to process. Accordingly, throughput is much lower than that required from a viewpoint of mass-production, for instance 1 min per one piece of the object.
SUMMARY OF THE INVENTION
The present invention is made to solve the aforementioned problems. That is, an object of the present invention is to provide a method and an apparatus for manufacturing semiconductors that can successfully regulate film quality at the interfaces between silicon substrates and SiN films.
The other object of the present invention is to provide a method and an apparatus for manufacturing semiconductors that can form a SiN film of high quality in a short time.
To the above ends, a manufacturing method of semiconductors of the present invention is characterized in implementing the invention in the following manner. That is, in an atmosphere of processing gas, microwaves are irradiated through a planar-array antenna having a plurality of slits on an object to be processed comprising silicon to generate plasma containing oxygen, or nitrogen, or oxygen and nitrogen. With the plasma, direct oxidation, nitriding, or oxy-nitriding is implemented on a surface of the object to form an insulator film of a thickness of 1 nm or less (in terms of silicon oxide film).
In the present manufacturing method, a thickness of insulator film is 1 nm or less. Accordingly, the nitriding of the silicon substrate is not due to diffusion but due mainly to a reaction process between nitrogen atoms or oxygen atoms or nitrogen and oxygen atoms generated by the plasma and the surface of silicon substrate. As a result of this, a nitriding rate of such short as approximately 30 sec can be obtained. on the thin insulator film that is obtained by implementing the direct nitriding or oxidizing or oxy-nitriding, the rest of the insulator film is deposited by use of CVD method. In this case, since a deposition rate of 3 nm/min or more can be attained relatively easily, even an insulator film of a total film thickness of 4 nm can be formed in less than two min.
In addition, in the present manufacturing method, a process for forming, due to direct nitriding or oxidizing or oxy-nitriding, an insulator film of good quality at an interface with the silicon substrate and a process for forming thereon, due to CVD method, the rest of the insulator film can be independently implemented. Accordingly, compared with the case where all process is implemented by direct nitriding only or CVD method only to form an insulator film, the film quality at the interface with the silicon substrate can be improved in regulation to result in an insulator film of better quality.
In the present manufacturing method, for the processing gases, a gas containing for instance N
2
or N
2
O or NO or NH
3
can be cited. The processing gas can contain rare gas such as argon or the like.
Another manufacturing method of semiconductors of the present invention comprises a step of forming a first insulator film and a step of forming thereon a second insulator film. Here, the step of forming the first insulator is carried out in the following manner. That is, in an atmosphere of a processing gas, on an object to be processed comprising silicon, through a planar-array antenna having a plurality of slits, microwaves are irradiated to generate plasma containing oxygen, or nitrogen, or oxygen and nitrogen. With the plasma, direct oxidizing, nitriding, or oxy-nitriding is implemented to. form the first insulator film.
In the aforementioned manufacturing method, the second insulator film can be an insulator film comprising for a instance silicon nitride.
The process of forming the second insulator film may be implemented by use of CVD method, or by use of plasma irradiation.
Plasma containing for instance N
2
or NH
3
and monosilane or dichlorosilane or trichlorosilane is supplied to form the second insulator film.
According to the present method, in an atmosphere of a processing gas, on
Hongoh Toshiaki
Kawakami Satoru
Murakawa Shigemi
Yuasa Mitsuhiro
Ghyka Alexander
Pillsbury & Winthrop LLP
Tokyo Electron Limited
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