Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Of specified material other than unalloyed aluminum
Reexamination Certificate
1999-03-26
2003-01-28
Smith, Matthew (Department: 2825)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Of specified material other than unalloyed aluminum
C427S250000, C427S252000, C427S255140, C427S255600, C505S447000
Reexamination Certificate
active
06512297
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a raw material of a chemical vapor deposition (hereinafter referred to as “CVD”) for forming an electrode or a wiring film that is employed in a dielectric memory such as Dynamic Random Access Memory (hereinafter referred to as “DRAM”), or ferroelectric Random Access Memory (hereinafter referred to as “FeRAM”), or as a dielectric filter of an electronic device, and it also relates to an electrode and a wiring film that are formed thereof.
Recently, a high integration of memory device in the semiconductor has been rapidly advancing. Progress in view of the high integration of, for instance, DRAMs resulted in a bit number that was four times larger than three years ago. This progress has been made in order to obtain an device having high speed processing, low consumption of electricity and low cost. However, a capacitor as for a component of a DRAM must have a specific capacitance, in spite of improvement in the integration of the device. Therefore, to secure the required capacitance has been investigated by various methods, for instance, decreasing the film thickness of material for capacitor, improving the permittivity by changing materials, or increasing the effective area by employing a three-dimensional shape, etc.
On the other hand, according to the high-performance of a semiconductor device and the like, it has become necessary to achieve a low resistance of an electrode or a wiring film employed therein and to achieve an affinity with the material of a capacitor or the material of a substrate. Instead of Al that has been generally employed as a material for forming an electrode in the conventional art, there have been employed Cu, Ir, Ru, Pt or, if necessary, an oxide thereof, as a material for forming an electrode and wiring.
Properties required for an electrode material are excellent electric properties of the obtained electrode, namely, small electrical resistance, and it is also important to have a required performance such as a favorable affinity with a dielectric material of a capacitor or with a material of a substrate thereon, and to be formed on a substrate of complicated shape.
For instance, in order to form an electrode as a thin film onto a capacitor of a stepped DRAM, it is necessary to have a favorable coverage of an object of complicated shape. In case of an electrode employed as a capacitor employing an oxide as a dielectric, it is necessary to prevent a decrease in property of the dielectric, and to have the favorable affinity between the dielectric and the electrode. For instance, in a capacitor of (Ba, Sr) TiO
3
or Sr—Bi—Ta—O, a metal of the platinum group such as Pt, Ru or Ir may be employed, and the interface between the dielectric and the electrode is preferably made of a conductive material of the oxide group such as RuO
2
or IrO
2
.
On the other hand, since the wiring material may be required, depending on the application thereof, to have a lower electric resistance than that of a conventional material such as Al, is attractive Cu, and development has been made in the field of Cu wiring technique. Mostly, of the film forming process for the electrode is sputtering, and it has partially been considered to employ a CVD method for Cu and the like.
Under these circumstances, though it is most advantageous to form a film through the CVD method, there is currently a large problem that there are no materials which present stable and favorable evaporating properties as the CVD source material. This is mostly due to the fact that the evaporating properties of dipivaloylmethane (DPM) compounds of the &bgr;-diketone group, mainly employed as the CVD material, are not favorable. This is also mentioned, for instance, in Lecture Number 9a-P- 11 of the Collection of Preparatory Drafts of the 52nd Applied Physics Academy Science Meeting, and is considered to be a problem owing to the essential instability of metallic DPM compounds. Nevertheless, the CVD method has been actively investigated, and there are also reported extreme cases in which the material is wasted after employing it once due to the above described instability of the material. In only case of Cu, materials with a relatively high vapor pressure have been developed, but they present a problem that the material contains fluorine in it or it lacks stability.
Therefore, there are no known techniques for manufacturing a film for an electrode, which has favorable performance and repeatability of manufacturing that overcome these problems owing to the above described material (raw material), and thus these materials need to be developed.
Japanese Unexamined Patent Publication No. Hei.-9-82907 discloses, as an example of the above described conventional art, a problem presented in case that the conventional metal film of Pt or the like was formed as an electrode film, namely, a decrease in permittivity and a generation of leak current according to decreasing the thickness of the capacitor film. As a method for solving this problem, it has been suggested to specify a site of Ba, Sr, Ti, and to form a (Ba, Sr) TiO
3
film with a metal oxide as a main component through a sputtering method, which has a perovskite crystal structure of ABO
3
type. The film contains approximately 1% by weight of Fe and has a thickness of approximately 20 nm.
Japanese Unexamined Patent Publication No. Hei. 8-288242 relates to the formation of Cu film through the CVD method, and it discloses a device in which plural supplying pipes can be sequentially employed as a measure against clogging of pipes that is apt to occur when supplying a Cu raw material. It also discloses a method in which an organic metal is dissolved in a suitable solvent as a Cu source material.
Further, Japanese Unexamined Patent Publication No. Hei. 9-27602 discloses forming of a (Ba
1-X
,Sr
X
)RuO
3
film through the sputtering method as an electrode in case of employing (Ba
1-X
Sr
X
)TiO
3
as a capacitor film, and it also refers to a CVD material containing Ru(C
5
H
5
)
2
that is employed by dissolving in a solvent.
Formation of film for electrode had conventionally been performed in the above manner, and since forming of film disclosed in the Japanese Unexamined Patent Publication No. Hei. 9-82907 had been performed through the sputtering method, there were still presented problems that the film had a poor coverage property, and that forming onto a capacitor of complicated shape was difficult.
In the method disclosed in the Japanese Unexamied Patent Publication No. Hei. 8-288242, Cu was employed as the electrode film, and the stability was not yet sufficient also in the Cu organic metal compound as described herein. And low temperature decomposition is apt to occur even if it has a relatively high vapor pressure, so that the controllability at the film forming is inferior. Thus, the device and the film forming process have been devised to cope with this problem. Further, though it discloses that an organic metal compound is dissolved in a suitable solvent to obtain a Cu material, it does not refer to the effects thereof, that is, the stability or the controllability as a raw material.
Similarly, the Japanese Unexamined Patent Publication No. Hei. 9-27602 does not refer to a stable supply of the organic metal material.
As described so far, it was difficult to supply the CVD material to a CVD reaction portion stably (to perform a stable supply) through heating at a low temperature owing to the stability and the evaporating deficiency of the CVD material for forming an electrode film through the conventional CVD method. Thus, there was a large problem that an electrode film of desired material having favorable properties could not be formed stably. Further, in case of heating at a high temperature in order to improve the evaporating efficiency of the CVD material, the raw material was transported while undergoing pyrolysis, and the deficiency in film shape and the lag of film thickness with the pre-determined value could not be avoided.
Also, a conventional method presented problems that the film
Matsuno Shigeru
Sato Takehiko
Uchikawa Fusaoki
Yamada Akira
Leydig , Voit & Mayer, Ltd.
Malsawma Lex H.
Mitsubishi Denki & Kabushiki Kaisha
Smith Matthew
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