Coating processes – Coating by vapor – gas – or smoke – Metal coating
Reexamination Certificate
2001-08-13
2003-06-10
Chen, Bret (Department: 1762)
Coating processes
Coating by vapor, gas, or smoke
Metal coating
C427S252000
Reexamination Certificate
active
06576292
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method of forming high adhesion copper thin films on metal nitride substrates.
BACKGROUND OF THE INVENTION
There has been a great interest in chemical vapor deposition (CVD) of copper metal thin films, because of copper's low resistivity (1.7 &mgr;&OHgr;-cm) and high electromigration resistance, the copper metal thin film is considered the ideal material for use as the metal interconnections in integrated circuit devices.
However, the adhesion of a copper thin film on a metal nitride substrate is difficult to achieve, and generally results in a film exhibiting poor adhesive qualities and conductivity less than that of pure copper. A copper interconnect line is formed by depositing copper onto either of a dual damascene or single damascene trench, wherein the trench is lines with a barrier metal, such as a metal nitride, i.e., titanium nitride or tantalum nitride. The layer is smoothed, typically by chemical mechanical polishing (CMP). Deposition methods may include physical vapor deposition (PVD), metal organic chemical vapor deposition (MOCVD) and electrochemical deposition (ECD), however, PVD has poor step coverage, and ECD requires the initial deposition of a copper seed layer, which, of course, must be deposited by PVD or MOCVD. Because of the poor step coverage of the PVD technique, PVD is not suitable for applications where very narrow, i.e., less than 100 nm, trenches are used to form the interconnects. MOCVD is more suited to deposition of copper in sub-micron trench/via copper fillings, and for providing the seed layer for ECD, however, the known MOCVD processes do not produce copper layers which have adequate adhesion between the copper layer and a metal barrier layer, such as a nitride layer. One solution is to use flash PVD to form a very thin seed layer prior to CVD or MOCVD, or to add a small amount of silicon to the barrier metal nitride compounds. While such processes provide adequate adhesion and conductivity characteristics for the copper layer, the process complexity is greatly increased, resulting in higher production costs and less throughput and may increase the barrier metal-to-copper contact resistance.
The copper precursor composition may be modified in an attempt to improve the copper thin film adhesion. CupraSelect Blend has been used to replace the pure CupraSelect (Cu(hfac)(tmvs)) by the addition of a very small amount of H(hfac).2H
2
O, about 0.4%. By using CupraSelect Blend (Cu(hfac)(tmvs)+H(hfac).2H
2
O), the adhesion of copper thin films on a TiN substrate have been improved, but have not improved adhesion on a TaN substrate. The abbreviation ‘hfac’ stands for hexafluoroacetylacetonate, while ‘tmvs’ stands for trimethylvinylsilane.
U.S. Pat. No. 5,322,712, to Norman et al., granted Jun. 21, 1994, for Process for Improved Quality of CVD Copper Films, describes introduction of an organometallic copper precursor and a complex copper vapor, or hydrate, of a volatile ligand.
U.S. Pat. No. 5,744,192, to Nguyen et al., granted Apr. 28, 1998, for Method of Using Water Vapor to Increase the Conductivity of Copper Deposited with Cu(hfac)(tmvs), describes use of 0.3% to 3% H
2
O
(g)
to increase conductivity of a copper layer.
SUMMARY OF THE INVENTION
A method of forming a highly adhesive copper thin film on a metal nitride substrate includes preparing a substrate having a metal nitride barrier layer formed on a portion thereof; heating the substrate in a chemical vapor deposition chamber to a temperature of between 160° C. to 250° C. for about one minute and simultaneously introducing a copper precursor into the reaction chamber at a very slow initial flow rate of between less than 0.1 ml/min, and simultaneously providing an initial high wet helium gas flow in the reaction chamber of greater than 5 sccm; reducing the wet helium gas flow in the reaction chamber to 5 sccm or less; and increasing the flow of copper precursor to between about 0.1 ml/min and 0.6 ml/min.
It is an object of the invention to provide a method of forming high adhesion copper thin films on metal nitride substrates.
This summary and objectives of the invention are provided to enable quick comprehension of the nature of the invention. A more thorough understanding of the invention may be obtained by reference to the following detailed description of the preferred embodiment of the invention in connection with the drawings.
REFERENCES:
patent: 5322712 (1994-06-01), Norman et al.
patent: RE35614 (1997-09-01), Norman et al.
patent: 5744192 (1998-04-01), Nguyen et al.
patent: 5891513 (1999-04-01), Dubin et al.
patent: 6090705 (2000-07-01), Arena et al.
patent: 6245261 (2001-06-01), Zhuang et al.
patent: 6281377 (2001-08-01), Zhuang et al.
patent: 6423201 (2002-07-01), Mandrekar
Evans David Russell
Hsu Sheng Teng
Zhuang Wei-Wei
Chen Bret
Krieger Scott C.
Rabdau Matthew D.
Ripma David C.
Sharp Laboratories of America Inc.
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