Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – Insulated gate formation
Reexamination Certificate
2002-04-16
2003-11-04
Kielin, Erik (Department: 2811)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
Insulated gate formation
C438S216000, C438S287000, C438S785000, C257S410000
Reexamination Certificate
active
06642131
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device and a method for producing the same, in particular, a high dielectric constant film used for a gate insulating film.
With recent technological advance with respect to high integration and high speed in semiconductor devices, miniaturization of MOSFETs has been under development. When the thickness of a gate insulating film is being reduced to achieve the miniaturization, problems such as an increase of a gate leak current due to tunneling current are caused. In order to suppress this problem, there has been research on an approach to increase a physical thickness while realizing a small SiO
2
equivalent thickness (hereinafter, referred to as “EOT”) by using gate insulating films made of high dielectric constant material such as hafnium oxide (HfO
2
) and zirconium oxide (ZrO
2
) (hereinafter, referred to as “high-k gate insulating films”).
For example, a method for forming a conventional high-k gate insulating film described in U.S. Pat. No. 6,013,553 is as follows. First, an oxide layer such as a SiO
2
layer is formed on a silicon substrate, and then a metal film made of zirconium or hafnium is deposited on the oxide layer by sputtering or plasma CVD. Thereafter, the metal film is subjected to an oxynitridation treatment with gas such as NO to form a high-k gate insulating film made of zirconium oxynitride (ZrO
x
N
y
) or hafnium oxynitride (HfO
x
N
y
).
However, in the conventional high-k gate insulating film, when heat history is applied by a high temperature treatment during the production process, the high dielectric constant material constituting the gate insulating film is crystallized, so that the electrical conductivity via the resultant crystal grain boundaries or the defect level increases leak current. That is to say, the thermal stability of the conventional high-k gate insulating film is insufficient.
SUMMARY OF THE INVENTION
Therefore, with the foregoing in mind, it is an object of the present invention to provide a semiconductor device employing a thermally stable gate insulating film having a high relative dielectric constant.
In order to achieve the object, a semiconductor device of the present invention includes a gate insulating film formed on a substrate; and a gate electrode formed on the gate insulating film, and the gate insulating film includes a high dielectric constant film containing a metal, oxygen and silicon; and a lower barrier film formed below the high dielectric constant film and containing the metal, oxygen, silicon and nitrogen.
According to the semiconductor of the present invention, the high dielectric constant film constituting the gate insulating film contains silicon, so that the high dielectric constant film is prevented from being crystallized by a high temperature treatment in the production process (e.g., a heat treatment for activating impurities at about 900° C.). Therefore, in a finished semiconductor device, the high dielectric constant film remains mostly amorphous, so that leak current can be suppressed from occurring in the high-k gate insulating film. Consequently, the thermal stability of the high-k gate insulating film can be improved, and therefore a semiconductor device having excellent heat resistance can be realized, and the process margin in the production of a semiconductor device can be increased.
According to the semiconductor of the present invention, the lower barrier film is present below the high dielectric constant film in the gate insulating film, so that the high dielectric constant film can be prevented from reacting with the substrate. Moreover, the lower barrier film contains the same metal as in the high dielectric constant film, so that the relative dielectric constant of the lower barrier film can be increased, and thus the relative dielectric constant of the entire gate insulting film can be increased.
In the semiconductor device of the present invention, it is preferable that the gate insulating film includes an upper barrier film formed above the high dielectric constant film, and the upper barrier film contains the metal, oxygen and nitrogen.
This prevents the gate electrode material and the high dielectric constant film material from being diffused to each other. Moreover, the upper barrier film contains the same metal as in the high dielectric constant film, so that the relative dielectric constant of the upper barrier film can be increased, and thus the relative dielectric constant of the gate insulting film as a whole can be increased.
In the semiconductor device of the present invention, it is preferable to satisfy
0.23
≦y/
(
x+y
)≦0.90
when the composition of the high dielectric constant film is expressed as M
x
Si
y
O, where M, O and Si represent the metal, oxygen and silicon, respectively, and x>0 and y>0.
This ensures the thermal stability of the high-k gate insulating film against a heat treatment at about 900° C. while keeping the relative dielectric constant of the high-k gate insulting film sufficient.
In the semiconductor device of the present invention, it is preferable to satisfy
0.23
≦y/
(
x+y
)≦0.30
when the composition of the high dielectric constant film is expressed as M
x
Si
y
O, where M, O and Si represent the metal, oxygen and silicon, respectively, and x>0 and y>0.
This ensures the thermal stability of the high-k gate insulating film against a heat treatment at about 900° C. while keeping the reliability life of the high-k gate insulting film sufficient.
In the semiconductor device of the present invention, it is preferable to satisfy
x/
(
x+y
)≧0.10
when the metal is hafnium or zirconium, and the composition of the lower barrier film is expressed as M
x
Si
y
ON, where M, O, Si and N represent the metal, oxygen, silicon and nitrogen, respectively, and x>0 and y>0.
This ensures that the relative dielectric constant of the lower barrier film can be increased.
In the semiconductor device of the present invention, the gate electrode may be a metal gate electrode.
A first method for producing a semiconductor device of the present invention includes the steps of forming a high dielectric constant film containing a metal, oxygen and a predetermine substance on a substrate; performing a heat treatment with respect to the high dielectric constant film to diffuse silicon from the side of the substrate into the high dielectric constant film, thereby forming a silicon-containing high dielectric constant film; and forming a conductive film for serving as a gate electrode on the silicon-containing high dielectric constant film.
According to the first method for producing a semiconductor device, a predetermined substance can be desorbed from the high dielectric constant film by performing a heat treatment with respect to the high dielectric constant film containing the predetermined substance, so that silicon is diffused in the high dielectric constant film through the thus formed vacancies and thus a silicon-containing high dielectric constant film can be formed. Therefore, silicon can be contained in the high dielectric constant film efficiently, and the vacancies eventually disappear, so that the silicon-containing high dielectric constant film can become dense. The silicon-containing high dielectric constant film hardly is crystallized by a high temperature treatment in the production process, so that the silicon-containing high dielectric constant film remains mostly amorphous after a device is complete. As a result, leak current can be suppressed from occurring in the gate insulating film including the silicon-containing high dielectric constant film, that is, the high-k gate insulating film. Consequently, the thermal stability of the high-k gate insulating film can be improved, and therefore a semiconductor device having excellent heat resistance can be realized, and the process margin in the production of a semiconductor device can be increased.
In the first semiconductor method of the present invention, it is preferable the predetermined subst
Kielin Erik
Matsushita Electric - Industrial Co., Ltd.
McDermott & Will & Emery
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