Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – Having insulated gate
Reexamination Certificate
1999-06-30
2001-07-24
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
Having insulated gate
C438S238000, C438S243000, C438S398000, C438S396000, C438S253000, C438S386000, C257S310000
Reexamination Certificate
active
06265260
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of semiconductors, and, more particularly, to a method for making a capacitor in an integrated circuit.
BACKGROUND OF THE INVENTION
An integrated circuit typically includes transistors and other devices formed on a semiconductor substrate. A capacitor may be provided as part of an integrated circuit by forming a first conductive electrode, a dielectric layer on the first electrode, and a second conductive electrode on the dielectric layer. Such capacitors are commonly used in memory cells for DRAM devices, for example, as well as in analog-to-digital converters and other circuits.
As disclosed in U.S. Pat. No. 5,910,880 to DeBoer et al., for example, tantalum pentoxide (Ta
2
O
5
) is a desired material for a capacitor dielectric because of its relatively high dielectric constant of about 25. In comparison, silicon nitride has a dielectric constant of about 8, and silicon dioxide has a dielectric constant of about 4. The high dielectric constant of tantalum pentoxide allows a thinner layer of the material to be used between the electrodes to achieve the same capacitance as using other lower dielectric constant materials.
A typical construction of such a capacitor includes a first or lower electrode of polycrystalline silicon. A first barrier layer of silicon nitride is typically provided to protect the polycrystalline silicon from forming into silicon dioxide and to prevent diffusion as the tantalum pentoxide is deposited thereon. A second barrier layer of titanium nitride or tungsten nitride may be deposited over the tantalum pentoxide prior to forming the polycrystalline silicon or metal layer of the upper electrode.
U.S. Pat. No. 5,622,888 to Sekine et al. discloses making a DRAM capacitor also using tantalum pentoxide. A layer of tungsten is sputter deposited on a polysilicon lower electrode. The tantalum pentoxide is deposited by chemical vapor deposition (CVD) at a temperature in a range of 300 to 600° C. Unfortunately, the higher temperatures may have a tendency to oxidize the tungsten. Thereafter, the tantalum pentoxide is densified by a plasma using an oxygen gas at a temperature ranging from 200 to 600° C. An upper tungsten electrode is formed on the tantalum pentoxide.
Despite continuing development in the field of integrated circuit capacitors using tantalum pentoxide as the dielectric, there still exists a need to further develop the manufacturing process to produce such capacitors having relatively high capacitance values and other desirable properties.
SUMMARY OF THE INVENTION
In view of the foregoing background, it is therefore an object of the invention to provide a method for making an integrated circuit capacitor having a relatively high capacitance.
This and other objects, features and advantages in accordance with the present invention are provided by a method for making an integrated circuit capacitor which in one embodiment preferably comprises the steps of: forming a first metal electrode adjacent a semiconductor substrate; forming a tantalum pentoxide layer on the first metal electrode while maintaining a temperature below an oxidizing temperature thereof; performing at least one remote plasma anneal of the tantalum pentoxide layer while also maintaining a temperature below the oxidizing temperature of the first metal electrode; and forming a second electrode adjacent the tantalum pentoxide layer while also maintaining a temperature below the oxidizing temperature of the first metal electrode. The step of forming the tantalum pentoxide layer preferably comprises chemical vapor deposition of the tantalum pentoxide at a temperature below about 500° C., and, more preferably, below about 400° C. The CVD forming of the tantalum pentoxide may preferably be performed in less than about 10 minutes. In addition, the pressure during CVD is typically greater than about 3 Torr, such as in a range of 3 to 15 Torr.
To reduce damage to the tantalum pentoxide layer, the step of annealing preferably comprises exposing the tantalum pentoxide layer to a first remote plasma of pure nitrogen and to a second remote plasma including nitrogen and oxygen. Accordingly, oxidation of the metal of the first electrode is avoided and a high quality tantalum pentoxide is produced by the method of the invention.
The metal of the first metal electrode may comprise at least one of titanium, tungsten, tantalum, platinum, iridium, ruthenium, and alloys thereof. More preferably, the first metal electrode comprises at least one of titanium, tungsten, tantalum, and alloys thereof. Most preferably the metal comprises titanium nitride.
The method may further include the steps of: forming at least one dielectric layer adjacent the semiconductor substrate, and forming an opening in the at least one dielectric layer. Accordingly, the step of forming the first metal electrode layer may comprise forming the first metal electrode layer to line the opening in the at least one dielectric layer.
The step of forming the first metal electrode may comprise the steps of forming a first metal layer and nitridizing an upper surface portion thereof according to one embodiment. The step of nitridizing may preferably include exposing the first metal layer to a nitrogen containing ambient while maintaining a temperature below the oxidizing temperature of the metal. Alternately, the step of forming the first metal electrode may comprise depositing a first metal layer and depositing a metal nitride layer thereon while preferably maintaining a temperature below the oxidizing temperature of the metal. The nitridized surface portion may further enhance resistance to oxidization of the underlying metal, especially for tungsten, for example.
REFERENCES:
patent: 5576240 (1996-11-01), Radosevich et al.
patent: 5622888 (1997-04-01), Sekine et al.
patent: 5780115 (1998-07-01), Park et al.
patent: 5825073 (1998-10-01), Radosevich et al.
patent: 5851870 (1998-12-01), Alugbin et al.
patent: 5903493 (1999-05-01), Lee
patent: 5910218 (1999-06-01), Park et al.
patent: 5910880 (1999-06-01), DeBoer et al.
patent: 5912797 (1999-06-01), Schneemeyer et al.
patent: 5913118 (1999-06-01), Wu
Hiroshi Shianrki et al., UV-O3 and Dry-O2: Two-Step Annealed Chemical Vapor-Deposited Ta2O5 Flims fro Storage Dielectrics of 64-Mb DRAM's IEEE Trans. Electron Devices vol. 38 No. 3, Mar. 1991.*
Alers et al.,Nitrogen Plasma Annealing for Low Temperature TA205 Films, Applied Physics Letters, US, American Institute of Physics. New York, vol. 72, No. 11, Mar. 16, 1998, pp. 1308-1310 XP000742858, ISSN: 0003-6951.
Yamagishi et al.,Stacked Capacitor Dram Process Using Photo-CVD TA205 Film, IEEE Transactions on Electron Devices, US, IEEE Inc., New York, vol. 35, No. 12, Dec. 1, 1998, p. 2439, XP0000496986, ISSN: 0018-9383.
Tanimoto et al.,Investigation on Leakage Current Reduction of Photo-CVD Tantalum Oxide Films Accomplished by Active Oxygen Annealing, Journal of the Electrochemical Society, US, Electrochemical Society, Manchester, New Hampshire, vol. 139, No. 1, 1992, pp. 320-328, XP000261719, ISSN: 0013-4651.
Chaneliere et al.,Tantalum pentoxide (Ta205) thin films for advanced dielectric applications, Materials Science and Engineering R: Reports, CH, Elsevier Sequoia S.A., Lausanne, vol. 22, No. 6, May 25, 1998, pp. 269-322, XP004130212, ISSN:0927-796X.
Devine et al.,Electrical Properties of TA205 Films Obtained by Plasma Enhanced Chemical Vapor Deposition Using a TAF5 Source, Applied Physics Letters, US, American Institute of Physics. New York, vol. 68, No. 13, Mar. 25, 1996, pp. 1775-1777, XP000582376, ISSN: 0003-6951.
Matusi et al.,Reduction of Current Leakage in Chemical-Vapor Deposited TA205 Thin-Films by Oxygen-Radical Annealing, IEEE Electron Device Letters, US, IEEE Inc., New York, vol. 17, no. 9., Sep. 1, 1996, pp. 431-433, XP000625748, ISSN: 0741-3106.
Zhang et al., Characteristics of High Quality Tantalum Oxide Films Deposited by Photoinduced Chemical Vapor Deposition, Applied Physics Letters, US, American Institute of Physics, New York, vol. 73, No. 16, Oct. 19, 1998, p
Alers Glenn B.
Roy Pradip Kumar
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Keshavan Belur
Lucent Technologies - Inc.
Smith Matthew
LandOfFree
Method for making an integrated circuit capacitor including... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for making an integrated circuit capacitor including..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for making an integrated circuit capacitor including... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2566942