Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2001-08-28
2003-01-21
Pham, Long (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S303000, C257S310000
Reexamination Certificate
active
06509597
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor integrated circuit device and a manufacturing technique therefor. More specifically, the present invention relates to a technique effectively applicable to a FeRAM (Ferroelectric Random Access Memory).
A ferroelectric random access memory (FeRAM) is a nonvolatile memory using a binary characteristic of the polarization state of PZT (Pb(Zr
y
Ti
z
)O
3
) or the like which is a ferroelectric substance. A memory cell of this FeRAM consists of one memory cell selection MISFET and one information capacitor. A PZT film is used as the capacitive insulating film of the capacitor.
Since the ferroelectric substance such as a PZT film contains much oxygen liable to cause reaction, the characteristic of the ferroelectric substance tends to be degraded by various treatments conducted in manufacturing steps.
For example, Japanese Patent Laid-open No. 8-55850 and No. 10-321811 describe a technique for preventing a reaction with oxygen by forming a hydrogen barrier layer.
Japanese Patent Laid-open No. 10-163437 describes a technique for preventing the reaction of oxygen contained in a capacitive insulating film constituting a capacitive element by covering the upper surface of the capacitive element with a sacrificial protection film.
Japanese Patent Laid-open No. 11-135736 describes a technique for preventing the degradation of a ferroelectric substance and a high-dielectric-constant material due to a reduction atmosphere by covering an overall capacitive element with a hydrogen barrier film.
SUMMARY OF THE INVENTION
Inventors of the present invention have developed the capacitive element of an FeRAM. The polarization characteristic of this ferroelectric film is degraded by the presence of either H
2
(hydrogen) or H
2
O (water).
One of the causes of the occurrence of either hydrogen or H
2
O is the presence of an interlayer insulating film. That is, in the formation of a silicon oxide film, a silicon nitride film or the like by a plasma CVD (Chemical Vapor Deposition) method, hydrogen or H
2
O is generated during the reaction of material gas. In addition, the hydrogen or H
2
O is contained in the silicon oxide film. Besides, if a silicon oxide film is formed by performing heat treatment for an SOG film, hydrogen or H
2
O is generated by this heat treatment.
On the other hand, in case of an FeRAM having a peripheral circuit or a logic circuit provided around a memory cell formation region, multilayer wirings are provided if the logic circuit becomes complex.
Since interlayer insulating films are formed between these plural wirings, respectively, it is becoming more important to take measures against hydrogen or H
2
O.
An object of the present invention is to provide a technique for preventing film quality of a ferroelectric film constituting a capacitive element from being degraded.
Another object of the present invention is to provide a technique for improving the film quality of the ferroelectric film and thereby for improving characteristics of a FeRAM memory cell.
The above and other objects and novel features of the present invention will become apparent from description of the present specification and accompanying drawings.
Of inventions disclosed by the present application, the outline of representative ones will be briefly described as follows.
(1) A semiconductor integrated circuit device according to the present invention is a semiconductor integrated circuit device having an information transfer MISFET formed on a main surface of a semiconductor substrate, and a capacitor connected in series to said information transfer MISFET, wherein it has a first shielding film formed under a lower electrode and a second shielding film formed on the upper electrode of said capacitor.
According to means as described above, the first and second shielding films can prevent H
2
or H
2
O from entering an upper or lower portions of the capacitor and prevent the characteristics of a high-dielectric-constant material or ferroelectric material (capacitive insulating film) from being degraded in the capacitor. In addition, the first and second shielding films can reduce diffusion of the components, e.g., lead included in the capacitive insulating film. The first and second shielding films may be made of lead compounds. Also, the capacitive insulating film may be made of a lead compound. If a lead composition ratio of each of the first and second shielding films is set higher than that of the capacitive iinsulating film, then lead diffused from the capacitive insulating film can be compensated by lead included in the first and second shielding films. Thereby, it is possible to prevent the characteristics of the capacitive insulating film from being degraded. The lead compound is exemplified by PZT (Pb
x
(Zr
y
Ti
z
)O
3
) or the like. In addition, if said upper or lower electrode is covered with the first and second shielding films, for example, by forming a side wall film on the side wall of the:upper or lower electrode, or the like, then the present invention becomes more effective.
(2) A semiconductor integrated circuit device according to the present invention is a semiconductor integrated circuit device having an information transfer MISFET formed on a main surface of a semiconductor substrate, and a capacitor connected in series to the information transfer MISFET, wherein it has a shielding film formed under the lower electrode of said capacitor.
According to means as described above, the shielding film can prevent H
2
or H
2
O from entering the lower portion of the capacitor and prevent the characteristics of the high-dielectric-constant material or ferroelectric material (capacitive insulating film) from being degraded in the capacitor. In addition, the shielding film can reduce diffusion of the components, e.g., lead included in the capacitive insulating film. Further, it is possible to improve the crystallinity of the capacitive insulating film on the shielding film. Since the insulating film under a region in which the capacitor is formed contains hydrogen by hydrogen annealing treatment, in particular, it is possible to prevent entry of the hydrogen. This shielding film may be made of a lead compound. Also, the capacitive insulating film may be made of a lead compound. If the lead composition ratio of the shielding film is set higher than that of the capacitive insulating film, lead diffused from the capacitive insulating film can be compensated by lead included in the shielding film. Therefore, it is possible to prevent the characteristics of the capacitive insulating film from being degraded. The lead compound is exemplified by PZT (Pb
x
(Zr
y
Ti
2
)O
3
) or the like.
(3) A semiconductor integrated circuit device according to the present invention is a semiconductor integrated circuit device having an information transfer MISFET formed on a main surface of a semiconductor substrate, and a capacitor connected in series to the information transfer MISFET, wherein is has an interlayer insulating film formed on the information transfer MISFET and the capacitor, the interlayer insulating film which has a barrier layer made of a high-dielectric-constant material or a ferroelectric material.
According to means as described above, the barrier layer can prevent H
2
or H
2
O included in the interlayer insulating film from entering the capacitor and prevent the high-dielectric-constant material or ferroelectric material (capacitive insulating film) from being degraded in the capacitor. This barrier layer may be made of a lead compound. The lead compound is exemplified by PZT (Pb
x
(Zr
y
Ti
2
)O
3
) or the like. This barrier layer may be amorphous. The barrier layer may be formed so as to be put between the first and second insulating films. Also, in the case where a plug is formed in the interlayer insulating film, the bottom and side portions of the plug may be covered with a conductive film having a barrier property such as a TiN film or the like. Further, the barrier layer may be formed in all the interlayer insulating
Mori Mitsuhiro
Waki Hiromichi
Yoshizumi Keiichi
Hitachi , Ltd.
Pham Hoai
Pham Long
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