Active solid-state devices (e.g. – transistors – solid-state diode – With means to control surface effects – Insulating coating
Reexamination Certificate
1999-03-16
2001-06-26
Crane, Sara (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
With means to control surface effects
Insulating coating
C257S649000
Reexamination Certificate
active
06252296
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a method of manufacturing a semiconductor device including the step of forming a silicon oxynitride film on a silicon substrate, and more particularly to a method of localizing nitrogen at an interface between the silicon substrate and the silicon oxynitride film. The present invention also relates to a semiconductor device obtained by such methods.
2. Description of the Background Art
The method of forming a silicon oxynitride film as a gate insulating film on a silicon substrate is conventionally known. The silicon oxynitride film as a gate insulating film is used because the reliability of an insulating film and therefore a device increases compared with a silicon oxide film.
The method of forming a silicon oxynitride film is described in Appl. Phys. Lett. 63 (1993), p. 54, for example. Here, a silicon oxynitride film is formed by using N
2
O gas and an RTA device (Rapid Thermal Anneal device). Meanwhile, it is known that an oxynitride film formed by an older prior art diffusion furnace has nitrogen diffused to the entire film.
However, any of the conventional methods was not designed for intentionally controlling the depth direction profile of nitrogen in an oxynitride film. Therefore, a method in which TDDB (Time Dependent Directric Breakdown) characteristics are sufficiently satisfied has not been obtained. That is, when a silicon oxynitride film obtained by a conventional method is used as a gate insulating film, the silicon substrate and the gate electrode are electrically connected.
SUMMARY OF THE INVENTION
The present invention is intended to solve the above mentioned problems and its object is to provide a method of manufacturing a semiconductor device which has a silicon oxynitride film having superior TDDB characteristics.
Another object of the present invention is to provide a method of forming a silicon oxynitride film having TDDB characteristics superior than a silicon oxynitride film having nitrogen distributed to the entire film.
Still another object of the present invention is to provide a semiconductor device obtained by such methods.
The invention according to claim
1
relates to a method of manufacturing a semiconductor device having a silicon oxynitride film. First, a silicon substrate is prepared. Gas including non-pyrolized N
2
O is brought into contact with a surface of the silicon substrate while the silicon substrate is heated, and thereby a silicon oxynitride film is formed on the surface of the silicon substrate.
According to the invention, the gas including non-pyrolized N
2
O is brought into contact with the surface of the heated silicon substrate. It was found out that nitrogen in the silicon oxynitride film formed by this method localizes at an interface between the silicon substrate and the silicon oxynitride film. It was also found out that an Si—NO
2
chemical bond unit does not exist at the interface and a portion other than the interface (hereinafter, referred to as a bulk portion). It was also made clear that the silicon oxynitride film having nitrogen localized at the interface has TDDB characteristics improved compared with a silicon oxynitride film having nitrogen uniformly distributed in the film.
In a method of manufacturing a semiconductor device according to claim
2
, the above described gas including N
2
O is introduced from the side of the silicon substrate to the surface of the silicon substrate at a flow speed of 0.5 m/sec or more.
Since the flow speed of N
2
O gas is made higher than 0.5 m/sec according to the method, pyrolisis of N
2
O is not caused. As a result, a silicon oxynitride film having nitrogen localized only at an SiO
2
/Si interface can be formed.
In a method of manufacturing a semiconductor device according to claim
3
, the above described N
2
O gas is brought into contact with the surface of the silicon substrate while the silicon substrate is rotated.
Since it is performed while the silicon substrate is rotated, the gas flow is disturbed. Thus, N
2
O gas that is not heated, that is, not pyrolyzed always reacts with the silicon substrate. As a result, a silicon oxynitride film having nitrogen localized only at an SiO
2
/Si interface can be formed.
The invention according to claim
4
relates to a method of manufacturing a semiconductor device having a silicon oxynitride film. First, a silicon substrate is prepared. Gas including non-pyrolyzed N
2
O is blown like a shower to a surface of the silicon substrate from above while the silicon substrate is heated, and thereby a silicon oxynitride film is formed on the surface of the silicon substrate.
Since the gas including non-pyrolyzed N
2
O is blown like a shower to the surface of the silicon substrate according to the invention, N
2
O can react with the silicon substrate without pyrolyzing N
2
O. As a result, an oxynitride film having nitrogen localized only at an SiO
2
/Si interface can be formed.
The invention according to claim
5
relates to a method of manufacturing a semiconductor device having a silicon oxynitride film. An oxide is formed on a silicon substrate. A compound of nitrogen and oxygen is ion-implanted to an interface between the silicon substrate surface and the oxide film.
According to the present invention, a silicon oxynitride film having nitrogen localized only at an SiO
2
/Si interface can also be formed. Accordingly, a silicon oxynitride film having superior TDDB characteristics can be obtained.
A semiconductor device according to claim
6
includes a silicon substrate. On the silicon substrate, a silicon oxynitride film is provided that does not include the chemical bond unit shown by the structural formula below at any portion in the film thickness direction.
Since the silicon oxynitride film as a gate insulating film does not include an Si—NO
2
chemical bond unit at any portion in the film thickness direction according to the present invention, a silicon oxynitride film having superior TDDB characteristics can be obtained.
In a semiconductor device according to claim
7
, the silicon oxynitride film is formed by bringing gas including non-pyrolyzed N
2
O into contact with a surface of the silicon substrate while the silicon substrate is heated.
When a silicon oxynitride film is formed by this method, a silicon oxynitride film that does not include an Si—NO
2
chemical bond unit at any portion in the film thickness direction can be obtained.
REFERENCES:
patent: 5726087 (1998-03-01), Tseng et al.
patent: 6-151829 (1994-05-01), None
patent: 9-306907 (1997-11-01), None
“Controlled Nitridation of SiO2 for the Formation of Gate Insulators in FET Devices”, IBM Technicla Disclosure Bulletin, vol. 28, Issue No. 6, pp. 2665-2666, Nov. 1985.*
“Role of Interfacial Nitrogen in Improving Thin Silicon Oxides Grown in N2O”, E.C. Carr et al., Applied Physics Letter 63(1), Jul. 5, 1993, pp. 54-56.
Tamura Hiroaki
Umeda Hiroshi
Crane Sara
McDermott & Will & Emery
Mitsubishi Denki & Kabushiki Kaisha
Tran Thien F.
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