Semiconductor device manufacturing: process – Making passive device – Stacked capacitor
Reexamination Certificate
1999-06-25
2001-06-19
Chaudhari, Chandra (Department: 2813)
Semiconductor device manufacturing: process
Making passive device
Stacked capacitor
C438S399000, C438S253000, C438S682000
Reexamination Certificate
active
06248640
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for fabricating a semiconductor device, and more particularly, to a method for forming a capacitor of a semiconductor device.
2. Description of the Related Art
With the development of technology for manufacturing semiconductor integrated circuits (IC) and extension of their application fields, development of large capacity memory devices is in progress. Large capacity memory devices are highly integrated, thus reducing the area of a memory cell unit and cell capacitance.
Particularly, in a dynamic random access memory (DRAM) device comprised of a capacitor for use as an information storage unit and a switching transistor connected to the capacitor, a reduction in cell capacitance due to a decrease in the area of the memory cell unit lowers the read-out capability of the memory cell and increases soft error. Therefore, the reduction in cell capacitance must be prevented, to achieve high integration of the memory devices.
A capacitor for a semiconductor memory device is comprised of a storage node being a lower electrode, a dielectric film, and a plate node being an upper electrode. In order to obtain a higher capacitance in a restricted area of the capacitor of the semiconductor memory device, research has been conducted in the following three areas: (1) a reduction in thickness of the dielectric film; (2) an increase in effective area of the capacitor; and (3) use of a dielectric film material having a high dielectric constant.
In a method for fabricating a capacitor using a material having a high dielectric constant, an oxide film and a nitride film or a composite film of oxide and nitride films was initially used as the dielectric film, but ongoing efforts have been made to use ditantalum pentoxide (Ta
2
O
5
), tita strontium trioxide (SrTiO
3
), or tita strontium barium trioxide ((BaSr)TiO
3
), each having a high dielectric constant, instead of the above films. Ditantalum pentoxide (Ta
2
O
5
) has a dielectric constant of approximately 24, which is six times that of the oxide dielectric film. Thus, ditantalum pentoxide (Ta
2
O
5
) has been predicted as the most practical high dielectric film material up to now, even though leakage current has been high due to a deficiency of oxygen within the dielectric film.
The above-described technology has been disclosed in U.S. Pat. No. 5,079,191, “Process for Producing a Semiconductor Device”, Jan. 7, 1992.
In the prior art, in order to reduce leakage current in a ditantalum pentoxide (Ta
2
O
5
) thin film resulting from a deficiency of oxygen, a dielectric film of ditantalum pentoxide is deposited and then oxidized at a temperature of 600 to 1000 degree C., thus supplying necessary oxygen to the dielectric film and simultaneously increasing the density of the dielectric film.
However, in this method, an oxide film having a low dielectric constant grows below the dielectric film, causing a reduction of the overall capacitance. Also, the high temperature for oxidation causes a decrease in the concentration of impurities on the surface of a lower electrode formed of polysilicon doped with impurities, thus greatly changing Cmin/Cmax.
SUMMARY OF THE INVENTION
To solve the above problems, it is an objective of the present invention to provide a method of forming a capacitor of a semiconductor device using high temperature oxidation, which can prevent disconnection between lower electrodes by forming an oxide of a second conductive film on an interlayer dielectric by depositing the metallic second conductive film on a semiconductor substrate on which the lower electrode is formed and oxidizing the deposited film, and which can obtain a high capacitance by forming both a silicide layer including the second conductive film, and an oxide of the second conductive film having a high dielectric constant, on the lower electrode, and using the silicide layer and the oxide as a dielectric film, on the basis of the characteristics that a conductive film of a silicide origin is oxidized by oxidation.
Accordingly, to achieve the above objective, in a method of forming a capacitor of a semiconductor device using high-temperature oxidation, first, a capacitor lower electrode pattern of a first polysilicon film is formed on a semiconductor substrate on which an interlayer dielectric is formed. A second conductive film is formed on the entire surface of the semiconductor substrate on which the capacitor lower electrode is formed. Silicide mixed with the second conductive film and an oxide of the second conductive film are formed on the capacitor lower electrode pattern by oxidizing the semiconductor substrate on which the second conductive film is formed, at a high temperature. Only the oxide of the second conductive film is formed on the interlayer dielectric. A dielectric film is formed on the semiconductor substrate on which the high temperature oxidation was performed. An upper electrode of a third conductive film is formed on the semiconductor substrate on which the dielectric film has been deposited.
According to a preferred embodiment of the present invention, the first polysilicon film is formed of polysilicon doped with impurities, and the second conductive film is formed of one material selected from the group consisting of titanium (Ti), tungsten (W), tantalum (Ta), molybdenum (Mo), platinum (Pt), cobalt (Co), palladium (Pd), nickel (Ni) and hafnium (Hf). Also, it is suitable that the dielectric film is a single film or a composite film including at least one film selected from the group consisting of an oxide film, a nitride film, and ditantalum pentoxide (Ta
2
O
5
), and that the third conductive film is formed of polysilicon doped with impurities, or a metal.
Preferably, in the high temperature oxidation, the semiconductor substrate is introduced into a chamber of a rapid thermal processing (RTP) apparatus, and rapid thermal oxidation (RTO) is performed on the semiconductor substrate for between 30 seconds and 5 minutes, under an oxygen atmosphere, at a temperature of 650 to 850 degree C. Alternatively, the semiconductor substrate is introduced into a furnace and dry-oxidized for between 5 minutes and one hour, under an oxygen atmosphere, at a temperature of 650 to 850 degree C. Or, the semiconductor substrate is introduced into a furnace and wet-oxidized for between 5 minutes and one hour, at a temperature of 600 to 800 degree C.
Also, it is preferable that post-processing on the dielectric film, such as ultraviolet ozone (UV-O
3
) processing or oxidation, is further performed after the step of depositing the dielectric film.
According to the present invention, the oxide film of the second conductive film such as titanium dioxide (TiO
2
) is formed on the interlayer dielectric using high temperature oxidation, so that disconnection between lower electrodes is prevented. Also, the silicide layer including the second conductive film, and the oxide of the second conductive film having a high dielectric constant, arc simultaneously formed on the lower electrode, and the result is used as the dielectric film, thereby obtaining a high capacitance in a process for forming a capacitor of a semiconductor device.
REFERENCES:
patent: 5316982 (1994-05-01), Taniguchi
patent: 5985731 (1999-11-01), Weng et al.
Chaudhari Chandra
Huynh Yennhu B.
Marger & Johnson & McCollom, P.C.
Samsung Electronics Co,. Ltd.
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