Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2000-09-05
2002-07-23
Flynn, Nathan (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S296000, C257S297000, C257S298000
Reexamination Certificate
active
06423999
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a semiconductor device and a method of fabricating the same.
2. Description of the Related Art
In these days, a semiconductor memory device has been required to operate at a higher rate, have a greater capacity for storing data therein, and operate in less power consumption. To such requirements, there has been suggested a dynamic random access memory (DRAM), which is much in demand now, having a capacitive or insulating film of a capacity device or a memory node which film is composed of metal oxides having a greater dielectric constant than that of a silicon dioxide film in order to make it possible to form memory cells in a circuit smaller. Some of such metal oxides are ferroelectric. There has been also suggested a non-volatile memory utilizing ferroelectric characteristics of those metal oxides.
Japanese Unexamined Patent Publication No. 7-38068 published on Feb. 7, 1995 has suggested a semiconductor memory device having a capacitive film composed of high-dielectric substance.
FIG. 1
illustrates the suggested semiconductor memory device.
LOCOS oxide films
803
are formed at a surface of a silicon substrate
801
to thereby define a device formation region therein. Below LOCOS films
803
are formed channel stopper regions
804
. Source/drain regions
802
are formed at a surface of the silicon substrate
801
. Gate electrodes
805
acting as word lines are formed on LOCOS oxide films. A signal line
806
acting as a bit line is formed on the silicon substrate
801
between the source/drain regions
802
.
An interlayer insulating film consisting of a silicon dioxide film
807
and a silicon nitride film
808
is formed on the silicon substrate
801
. The interlayer insulating film is formed therethrough with contact holes
809
reaching the source/drain regions
802
. Each of the contact holes
809
is filled with a plug
810
composed of an electrically conductive material such as metal.
A capacity device having a capacitive film composed of high-dielectric substance is formed on the interlayer insulating film. The capacity device is in electrical connection with the source/drain regions
802
through the plug
810
. The silicon nitride film
808
and the plug
810
are both planarized at the same level.
The capacity device is comprised of a plurality of lower or storage electrodes
811
, a capacitive insulating film
812
entirely covering the lower electrodes
811
therewith, and an upper or plate electrode
813
deposited all over the capacitive insulating film
812
.
Over the upper electrode
813
are formed a metal wiring layer (not illustrated), and an interlayer insulating film
814
for electrically insulating the metal wiring layer and the upper electrode
813
with each other, to thereby constitute a semiconductor memory device.
After the metal wiring layer has been formed, the product is thermally annealed in hydrogen atmosphere in order to reduce a dispersion in a threshold voltage of transistors arranged on a surface of the silicon substrate, and a dispersion in a current for driving transistors. This thermal annealing compensates for defects, such as a trap level, formed at an interface between the capacity device and the interlayer insulating film making contact with the capacity device.
However, the above-mentioned semiconductor memory device illustrated in
FIG. 1
has shortcomings as follows.
First, since the thermal annealing in hydrogen atmosphere is carried out after the capacity device has been formed, the capacitive film composed of metal oxide is unpreferably reduced with the result of deterioration of capacitive characteristics of the capacity device.
Secondly, transistors formed on layers located below a layer on which the capacity device is formed may be deteriorated with respect to performance and reliability thereof. Specifically, as illustrated in
FIG. 1
, since the silicon nitride film
808
entirely covers the silicon dioxide film
807
except the plugs
810
, if the product is thermally annealed in hydrogen atmosphere after the capacity device has been formed, the silicon nitride film
808
acts as a barrier for hydrogen to reach layers on which transistors are formed. As a result, performance of transistors and reliability for transistors are deteriorated, and a characteristic of transistors is not uniformized.
SUMMARY OF THE INVENTION
In view of the above-mentioned problems in a conventional semiconductor memory device, it is an object of the present invention to provide a semiconductor device and a method of fabricating the same both of which are capable of avoiding a capacitive film composed of metal oxide from being degraded even if a capacity device is thermally annealed in hydrogen atmosphere.
In one aspect of the present invention, there is provided a semiconductor device including (a) a semiconductor substrate, (b) a capacity device, (c) an interlayer insulating layer formed between the semiconductor substrate and the capacity device for electrically isolating them with each other, the interlayer insulating layer being formed therethrough with a contact hole below the capacity device, (d) a contact plug composed of an electrically conductive material and formed in the contact hole, (e) a film composed of a material through which hydrogen is not allowed to pass, the film entirely covering both the capacity device and the contact plug therewith.
In accordance with the above-mentioned semiconductor device, both the capacity device which may include a capacitive film composed of metal oxide, and the contact plug electrically connecting the capacity device to the semiconductor substrate are entirely covered with a film composed of a material through which hydrogen is not allowed to pass. Hence, it is possible to prohibit hydrogen to reach the capacitive film.
There is further provided a semiconductor device including (a) a semiconductor substrate, (b) a capacity device, (c) an interlayer insulating layer formed between the semiconductor substrate and the capacity device for electrically isolating them with each other, the interlayer insulating layer being formed therethrough with a contact hole below the capacity device, (d) a contact plug composed of an electrically conductive material and formed in the contact hole, (e) a first film composed of a first material through which hydrogen is not allowed to pass, and formed between the interlayer insulating layer and the capacity device, (f) a second film composed of a second material through which hydrogen is not allowed to pass, and formed on an inner wall of the contact hole, (g) a third film composed of a third material through which hydrogen is not allowed to pass, and formed to cover an upper surface of the capacity device therewith, and (h) a fourth film composed of a fourth material through which hydrogen is not allowed to pass, and formed to cover a side surface of the capacity device therewith.
It is preferable that the first, second, third, and fourth materials are the same. The first, second, third, and fourth materials are preferably nitride, and more preferably silicon nitride.
It is preferable that the capacity device includes a capacitive film composed of tantalum oxide. As an alternative, the capacity device may include a capacitive film composed of high-dielectric or ferroelectric substance.
It is preferable that the contact hole electrically connects the capacity device to a source or drain region formed in the semiconductor substrate.
The semiconductor device may further include an upper electrode to be electrically connected to an external wiring, in which case, the upper electrode is located remote from the capacity device.
In another aspect of the present invention, there is provided a method of fabricating a semiconductor device, including the steps of (a) forming a multi-layered interlayer insulating film on a semiconductor substrate, the multi-layered interlayer insulating film including a first film, as an uppermost film, composed of a first material through which hydrogen is not
Flynn Nathan
Hutchins, Wheeler & Dittmar
NEC Corporation
Quinto Kevin
LandOfFree
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