Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1998-10-29
2001-05-22
Everhart, Caridad (Department: 2825)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S675000, C438S680000, C438S681000
Reexamination Certificate
active
06235631
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to forming metal layers in semiconductor integrated circuit manufacturing, and more specifically to the chemical vapor deposition of titanium aluminum nitride.
BACKGROUND OF THE INVENTION
Increasing demand for semiconductor memory and competitive pressures require higher density integrated circuit dynamic random access memories (DRAMs) based on one-transistor, one capacitor memory cells. But scaling down capacitors with the standard silicon oxide and nitride dielectric presents problems including decreasing the quantity of charge that may be stored in a cell. Consequently, alternative dielectrics with dielectric constants greater than those of silicon oxide and nitride are being investigated. Various dielectric materials are available, such as tantalum pentoxide, lead zirconate titanate, strontium bismuth tantalate, and barium strontium titanate (BST).
These alternative dielectrics are typically deposited at elevated temperatures and in an oxidizing ambient. As a result, an oxygen-stable bottom electrode material such as platinum or ruthenium oxide is used. Platinum, however, readily forms a silicide when in direct contact with silicon, and further is not a good barrier to oxygen due to fast diffusion down the platinum grain boundaries. A typical approach to solve this problem is to deposit the platinum on a thin oxidation barrier material. One such oxidation barrier material is titanium aluminum nitride. See co-pending, co-assigned application Texas Instruments Ser. No. 09/105,830, pending. See also Texas Instrument Ser. No. 09/105,738 now U.S. Pat. No. 6,153,490 and Ser. No. 09/05,411 now U.S. Pat. No. 6,090, for the hardmask and etch stop features of titanium aluminum nitride, or Ti-Al-N. Note that as used herein the notation “A-B-C” indicates that the material may exist in varying compositions of the elements A, B, and C, an example being “Si-O-N”. An alternative notation is “Ti
1-x
Al
x
N,” which is used herein in some instances.
Common deposition techniques for thin films include: physical vapor deposition (PVD), sputtering for example; thermal chemical vapor deposition (CVD); and plasma-enhance chemical vapor deposition (PECVD). PVD has been used for depositing Ti-Al-N, but lacks the film thickness control and step coverage available in CVD and PECVD systems. PECVD has been investigated for Ti-Al-N deposition. See for example S.-H. Lee, et al., “(Ti
1-x
Al
x
)N coatings by plasma-enhanced chemical vapor deposition,” J. Vac. Sci. Technol. A 12(4), Jul/Aug 1994, p. 1602, and S.-H. Lee, et al., “Compositionally gradient (Ti
1
-xAlx)N coatings made by plasma enhanced chemical vapor deposition,” J. Vac. Sci. Technol. A 13(4), Jul/Aug 1995, p. 2030. PECVD, however, also suffers from relatively poor step coverage, owing in large part to the directionality inherent in the electric field set up by the plasma.
Even though Ti-Al-N films produced by PVD and PECVD suffer from poor film quality and step coverage, no successful deposition of thermal CVD films has thus far been reported. The lack of a suitable precursor has been one obstacle to the implementation of CVD. The Lee papers cited above use inorganic precursors such as TiCl
4
, AlCl
3
, NH
3
, H
2
, and Ar in conjunction with PECVD for the deposition of Ti-Al-N. These precursors, however, typically require high temperatures to achieve deposition. In the Lee papers, for example, the reported substrate temperature is 450° C. Thus, a need exists in the industry for a method of forming Ti-Al-N thin films with a thermal CVD process.
SUMMARY OF THE INVENTION
In accordance with an embodiment of the invention, there is disclosed a method for the chemical vapor deposition of titanium aluminum nitride layers. The method includes the steps of placing a substrate in a deposition reactor; introducing tetrakis-dimethyl-amido-titanium (TDMAT) into the reactor; and introducing dimethyl-aluminum-hydride (DMAH) into the reactor in the presence of the TDMAT. In one embodiment the TDMAT is introduced at a rate of between 10 and 1000 times the rate at which the DMAH is introduced. In another embodiment the substrate temperature is between about 200° C. and 500° C.
An advantage of the inventive concepts is that titanium aluminum nitride films may be deposited with chemical vapor deposition. The films show good step coverage and uniform thickness.
REFERENCES:
patent: 6066358 (2000-05-01), Guo et al.
patent: 4222021 (1994-01-01), None
patent: 448223 (1991-09-01), None
Sun, Y-M et al. “Low Pressure CVD Growth of AlxTil-xN” Symp Chem Aspects of Electronic Ceramics Processing p. 165-70 (Abstract Only), Dec. 1997.*
Eiichi Kondoh and Tomohiro Ohta, “Chemical Vapor Deposition of Aluminum From Dimethylaluminumhydride (DMAH): Characteristics of DMAH Vaporization and A1 growth Kinetics”J. Vac. Sci. Technol. A,vol. 13, No. 6, pp. 2863-2871, Nov./Dec. 1995.
Ajit Paranjpe and Mazhar IslamRaja, “Chemical Vapor Deposition TiN Process for Contact/Via Barrier Applications”J. Vac. Sci. Technol. B13(5), pp. 2105-2113, Sep./Oct. 1995.
Sang-Hyeob Lee, Ho-Joon Ryoo and Jung-Joong Lee, “(Ti1-xAlx) N Coatings by Plasma-Enhanced Chemical Vapor Deposition”J. Vac. Sci. Technol. A12(4), pp. 1602-1607,. Jul./Aug. 1994.
Sang-Hyeob Lee and Jung-Joong Lee, “Compositionaly Gradient (Ti1-xAlx) N Coatings Made by Plasma Enhanced Chemical Vapor Deposition”J. Vac. Sci. Technol.,pp. 2030-2034.
D. McIntyre et al., “Oxidation of Metastable Single-Phase Polycrystalline Ti0.5Al0.5N Films: Kinetics and Mechanisms”J. Appl. Phys.67(3), pp. 1542-1553, Feb. 1, 1990.
L. Hultman et al., “Interfacial Reactions in Single-Crystal-TiN (100)/Al/Polycrystalline-TiN Multilayer Thin Films”Thin Solid Films,215, pp. 152-161, 1992.
I. Petrov et al., “Interfacial Reactions in Epitaxial Al/Ti1-xAlxN(<x<0.2) Model Diffusion-Barrier Structures”J. Vac. Sci. Technol. A11(1), pp. 11-17, Jan./Feb. 1993.
Brady III W. James
Everhart Caridad
Garner Jacqueline J.
Telecky Jr Frederick J.
Texas Instruments Incorporated
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