Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
1999-10-12
2003-04-15
Fahmy, Wael (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S378000, C257S640000, C257S641000, C257S649000, C257S650000
Reexamination Certificate
active
06548873
ABSTRACT:
RELATED APPLICATION DATA
The present application claims priority to Japanese Application No. P10-288984 filed Oct. 12, 1998 which application is incorporated herein by reference to the extent permitted by law.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device and a manufacturing method thereof and more specifically to a semiconductor device and a manufacturing method thereof which causes less characteristic fluctuation of elements and hardly causes a parasitic action even when the semiconductor device comprises a barrier metal made of a titanium material on an inter-layer insulating film.
2. Description of Related Art
FIG. 1
is a section view showing one structural example of a semiconductor device.
The semiconductor device shown in the figure is a so-called BiCMOS comprising a bipolar transistor
101
, an N-channel type MOS (Metal Oxide Semiconductor) transistor
102
, a P-channel type MOS transistor (not shown) and a MIS (Metal Insulator Semiconductor) type capacitor element
103
formed on the surface side of one and same semiconductor substrate
104
. The bipolar transistor
101
is an NPN type bipolar transistor having a double poly-silicon structure suited for high speed and the MOS transistor
102
has a single drain structure. The capacitor element
103
is formed by using a silicon nitride film as a dielectric film
105
.
An inter-layer insulating film
107
covering a gate electrode
106
of the MOS transistor
102
is composed of a first silicon oxide film
107
a
and a second silicon oxide film
107
b.
The first silicon oxide film
107
a
is a film for use as an opening of an active region of the bipolar transistor
101
and the second silicon oxide film
107
b
is a film formed on the first silicon oxide film
107
a
while covering a base electrode
109
of the bipolar transistor
101
and an upper electrode
110
of the capacitor element
103
. Wires
108
are provided on the inter-layer insulating film
107
constructed as described above. Its electro-migration resistance and heat resistance are assured by constructing it by laminating, in order from the bottom, a titanium film, titanium nitride oxide film, a titanium film and silicon aluminum film.
However, the semiconductor device constructed as described above has had the following problems.
In the semiconductor device constructed as explained by using
FIG. 1
, the wire
108
is provided on the gate electrode
106
via the inter-layer insulating film
107
composed of the first silicon oxide film
107
a
and the second silicon oxide film
107
b.
Therefore, hydrogen which has been captured by dangling bonds at the interface between the silicon/silicon oxide film (i.e., the interface between the semiconductor substrate
104
and the gate oxide film
111
) under the gate electrode
106
diffuse within the inter-layer insulating film
108
and are absorbed by the titanium film composing the wire
108
when a heating process such as a sintering process or an alloy processing for forming a titanium-gold alloy film on the back of the semiconductor substrate
104
is implemented after forming the wire
108
. As a result, the dangling bonds increase at the above-mentioned interface, thus fluctuating the threshold voltage of the MOS transistor
102
. Further, moisture within the thick silicon oxide film composing the inter-layer insulating film
107
diffuses under the gate electrode
106
, thus deteriorating the hot-carrier resistance of the MOS transistor
102
.
Meanwhile, as the BiCMOS type semiconductor device, there is also one using an inter-layer insulating film formed by laminating a silicon oxide film on a silicon nitride film as disclosed in Japanese Patent Laid-Open No. 2-32561.
In the semiconductor device disclosed in Japanese Patent Laid-Open No. 2-32561, the upper part of a MOS transistor is covered by a silicon nitride film for preventing the diffusion of hydrogen. Therefore, it is possible to prevent the hydrogen at the above-mentioned interface between the silicon/silicon oxide film under the gate electrode
106
from diffusing by the silicon nitride film even when the above-mentioned heating process is carried out after forming the wires above the silicon nitride film. Accordingly, it enables the prevention of the dangling bonds from increasing at the abovementioned interface. Still more, because the silicon nitride film also shuts down the diffusion of moisture, it is possible to prevent the moisture within the silicon oxide film composing the inter-layer insulating film from diffusing under the gate electrode. Accordingly, it allows the hot-carrier resistance of the MOS transistor to be assured.
However, because the upper part of the bipolar transistor is also covered by the silicon nitride film in this semiconductor device, a number of dangling bonds is kept small at the interface between the silicon and the silicon oxide film in the bipolar transistor (e.g., at the interface between the semiconductor substrate and the field oxide film in the above-mentioned publication). Accordingly, the current amplification factor (hFE) of a parasitic PNP bipolar transistor composed of a base/collector/substrate in the NPN type bipolar transistor becomes high.
Further, because an element isolating region for isolating the MOS transistors is also covered by the silicon nitride film in the semiconductor device described in the above-mentioned publication, hydrogen at the interface between the field oxide film and the semiconductor substrate composing the element isolating region are assured, thus preventing the dangling bonds from increasing. Therefore, threshold voltage (Para-Vth) of the parasitic MOS transistor formed between the adjoining MOS transistors becomes small. As a result, it has had a problem that a parasitic action is liable to occur.
Accordingly, it is an object of the present invention to provide a semiconductor device, and a manufacturing method thereof, which causes less characteristic fluctuation of elements and hardly causes parasitic action even if it comprises a barrier metal composed of a titanium material on an inter-layer insulating film.
SUMMARY OF THE INVENTION
In order to achieve the above-mentioned object, an inventive semiconductor device comprises a MOS transistor provided on the surface side of a semiconductor substrate; a silicon oxide insulating film and a silicon nitride insulating film provided on the semiconductor substrate while covering the MOS transistor; and wires having a barrier metal made of a titanium material and provided above these insulating films and is characterized in that the silicon nitride insulating film covers the MOS transistor and has an opening on an element isolating region for isolating the MOS transistors.
Because the silicon nitride insulating film covering the MOS transistor becomes a barrier in the semiconductor device constructed as described above, hydrogen which has been captured by dangling bonds at the interface between the semiconductor substrate and a gate oxide film will not reach to the wires provided above the silicon nitride insulating film. Therefore, it is possible to prevent the hydrogen from being absorbed by the barrier metal made of the titanium material constituting the wire and to suppress a number of dangling bonds from increasing at the above-mentioned interface. Accordingly, the threshold voltage of the MOS transistor is stabilized.
Further, because the silicon nitride insulating film becomes the barrier, it prevents moisture above the silicon nitride insulating film from diffusing down to a gate electrode of the MOS transistor. Therefore, the hot-carrier resistance of the MOS transistor may be assured.
Still more, because the opening of the silicon nitride insulating film is provided on the element isolating region for isolating the MOS transistors, hydrogen at the interface between the silicon oxide film and the semiconductor substrate diffuses upward via the silicon oxide film when the silicon oxide film is provided in the element isolating region, thus increas
Ammo Hiroaki
Kanematsu Shigeru
Miwa Hiroyuki
Fahmy Wael
Louie Wai-Sing
Sonnenschein Nath & Rosenthal
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