Metal treatment – Process of modifying or maintaining internal physical... – Carburizing or nitriding using externally supplied carbon or...
Reexamination Certificate
1999-02-11
2001-04-24
Sheehan, John (Department: 1742)
Metal treatment
Process of modifying or maintaining internal physical...
Carburizing or nitriding using externally supplied carbon or...
C148S281000, C148S283000, C427S327000, C427S343000, C427S419700
Reexamination Certificate
active
06221174
ABSTRACT:
BACKGROUND OF THE DISCLOSURE
1. Field of the Invention
The invention relates to a method of thin film processing and, more particularly, it relates to a method of forming an integrated film stack of titanium and titanium nitride with improved reliability.
2. Description of the Background Art
In the manufacture of integrated circuits, a titanium nitride film is often used as a metal barrier layer to inhibit the diffusion of metals into an underlying region beneath the barrier layer. These underlying regions include transistor gates, capacitor dielectric, semiconductor substrates, metal lines, and many other structures that appear in integrated circuits.
For example, when an electrode is being formed for a transistor's gate, a diffusion barrier is often formed between the gate material and a metal that serves as the contact portion of the electrode. The diffusion barrier inhibits the diffusion of the metal into the gate material, which may be composed of polysilicon. Such metal diffusion is undesirable because it would change the characteristics of the transistor, or render it inoperative.
When the underlying region is silicon (Si), it is also desirable to use a titanium/titanium nitride (Ti/TiN) combination as a barrier layer. Since the contact resistivity of Ti to Si is significantly lower than that of TiN to Si, the use of Ti to contact the underlying Si will lead to a lower contact resistance, while the TiN layer will act as an effective barrier against diffusion of metal into the underlying silicon.
Ti and TiN films can be formed by physical or chemical vapor deposition. A Ti/TiN combination barrier layer may be formed in a multiple chamber “cluster tool” by depositing a Ti film in one chamber followed by TiN film deposition in another chamber. When depositing both Ti and TiN using chemical vapor deposition (CVD), titanium tetrachloride (TiCl
4
), for example, may be used to form both Ti and TiN films when allowed to react with different reactant gases.
However, when a TiCl
4
-based chemistry is used in such an integrated Ti/TiN film process, a reliability problem is encountered. In particular, it has been found that if the thickness of the Ti film exceeds about 120 Å, the integrated Ti/TiN stack structure will either peel off or exhibit a haze that is indicative of poor film quality. This problem can be overcome by special treatment of the Ti film after Ti deposition. For example, if the Ti film is first subjected to a rapid thermal nitrogen (RTN) treatment, the subsequently deposited TiN film will not exhibit film failure in the form of peeling or haze. However, the drawback for this approach is that the additional process step of RTN can only be performed in a separate piece of equipment outside of the cluster tool. If the Ti film is formed from a high temperature CVD Ti process, the need for the additional RTN step decreases the process throughput. In general, an extra process step requiring additional wafer handling and transfer among different equipment translates to extra cost and additional risk for wafer contamination or breakage. Since Ti and TiN deposition are usually performed within different chambers in a cluster tool, the need for an additional step such as RTN would defeat the purpose of using a cluster tool for this Ti/TiN application.
Therefore, a need exists in the art for a method of forming a reliable Ti/TiN diffusion barrier in an integrated process.
SUMMARY OF THE INVENTION
The disadvantages associated with the prior art are overcome by the present invention of a method of forming an integrated Ti/TiN film structure by implementing two process steps between the Ti and TiN film deposition. The first step exposes the Ti film to an ammonia (NH
3
) environment under a high temperature condition. The second step deposits a thin seed layer of TiN film using a thermal TiCl
4
/NH
3
reaction under a NH
3
-rich condition. After depositing about 50 Å of the TiN seed layer, the process proceeds with TiN deposition under the normal condition. The combination of the NH
3
treatment and seed layer formation steps allows a successful Ti/TiN film integration for Ti film thickness up to about 300 Å, while the use of either step alone allows successful integration for Ti film thickness up to about 150 Å. Optionally, the seed layer of TiN may also be subjected to an NH
3
treatment step prior to the subsequent TiN deposition to reduce the chlorine content in the TiN film. Using the present invention, a conformal Ti/TiN diffusion barrier can successfully be formed in a contact structure with an aspect ratio up to about 12:1.
REFERENCES:
patent: 4897709 (1990-01-01), Yokoyama et al.
patent: 5175126 (1992-12-01), Ho et al.
patent: 5192589 (1993-03-01), Sandhu
patent: 5279857 (1994-01-01), Eichman et al.
patent: 5308655 (1994-05-01), Eichman et al.
patent: 5312774 (1994-05-01), Nakamura et al.
patent: 5378501 (1995-01-01), Foster et al.
patent: 5378660 (1995-01-01), Ngan et al.
patent: 5416045 (1995-05-01), Kauffman et al.
patent: 5420072 (1995-05-01), Fiordalice et al.
patent: 5567483 (1996-10-01), Foster et al.
patent: 5593511 (1997-01-01), Foster et al.
patent: 5610106 (1997-03-01), Foster et al.
patent: 5624868 (1997-04-01), Iyer
patent: 5789321 (1998-08-01), Ohsita
patent: 5866213 (1999-02-01), Foster et al.
patent: 397 131 A2 (1990-11-01), None
patent: 720 214 A2 (1996-07-01), None
patent: 63-229814 (1988-09-01), None
patent: 10-209077 (1998-08-01), None
patent: WO 95/33865 (1995-12-01), None
M.E. Gross, E. Coleman,K. Ohto, “Effect of NH3Plasma Treatment on Etching of Ti During TiCl4Baed TiN CVC Processes”, Material Res. Soc. Symp. Proc. vol 514, pp. 523-529.
J.T. Hillman, D. W. Studiner “Controlling the Properties of LPCVD Titanium Nitride”, VMIC Conference, Jun. 9-10, 1992.
N. Yokoyama, K. Hinode, Y. Homma, “LPCVDTitanium Nitride for ULSIs”, J. Electrochem. Soc. vol. 138, No. 1, Jan. 1991 pp 190-195.
K. Mori, M. Akazawa,M. Iwasaki, H. Ito, K. Tsukamoto, Y. Akasaka, “Contract Plug Formed with Chemical Vapour Deposited TiN”, 1991 Int'l Conference on Solid State Devices and Materials, Yokohama, 1991, pp. 210-212.
S.R. Kurtz, R.G. Gordon, “Chemical Vapor Deposition of Titanium Nitride at Low Temperatures”, Thin Solid Films, vol. 140, pp 277-290 (1986).
M.J. Buiting, A. F. Otterloo, A. H. Montree, “Kinetical Aspects of the LPCVD of Titanium Nitride from Titanium Tetrachloride and Ammonia”, J. Electrochem Soc., vol. 138, No. 2, Feb. 1991, pp 500-505.
M. Eizenberg, “Chemical Vapor Deposition of TiN for ULSI Applications”, Mat. Res. Soc. Symp. Proc. vol. 427, 1996, pp 325-335.
Bouteville et al. “Low Temperature Rapid Thermal Low Pressure Chemical Vapor Deposition of (111) Oriented TiN Layers from the TiCl4-NH3-H2Gaseous Phase” Microelectronic Engineering 37/38 , pp. 421-425, 1997.
Erkov et al. “Deposition and Properties of Titanium Nitride Films Obtained by TiCl4Ammonolysis in the LPCVD Process” Russian Microelectronics, vol. 27, No. 3, pp. 183-187, 1998.
Chen Fufa
Hu Jianhua
Lin Yin
Wu Frederick
Wu Li
Applied Materials Inc.
Oltmans Andrew L.
Sheehan John
Thomason Moser & Patterson
LandOfFree
Method of performing titanium/titanium nitride integration 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 of performing titanium/titanium nitride integration, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of performing titanium/titanium nitride integration will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2477536