Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of...
Reexamination Certificate
2001-03-12
2001-10-30
Lebentritt, Michael (Department: 2824)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
C438S784000, C438S789000
Reexamination Certificate
active
06309982
ABSTRACT:
BACKGROUND OF INVENTION
1) Field of the Invention
This invention relates generally to fabrication of a semiconductor device and more particularly to a method for minimizing copper diffusion into a plasma enhance chemical vapor deposition inorganic dielectric layer by doping the inorganic dielectric layer with phosphorous (P), or sulfur (S), or both.
2) Description of the Prior Art
As semiconductor dimensions continue to shrink and performance requirements continue to increase, it has become desirable to use copper for interconnections. However, traditional plasma enhanced chemical vapor deposition (PECVD) oxide (SiO
2
) dielectric layers suffer from copper migration into the oxide from the interconnect. To prevent this copper migration barrier layers (typically tantalum or tantalum nitride) are deposited onto the sidewalls of contact (via) openings in the dielectric layer, prior to depositing the copper.
As the openings continue to shrink, however, a barrier layer can cause performance problems. The barrier layer can adversely affect RC delay degrading device performance. Coverage of trenches and/or vias by a barrier layer is not uniform. THe barrier layer is thinnest along the side and at the bottom corners of trenches and/or vias, thereby offering poor barrier properties. Also, the crystalline nature of barrier metals tend to allow diffusion of copper along the grain boundaries.
The importance of overcoming the various deficiencies noted above is evidenced by the extensive technological development directed to the subject, as documented by the relevant patent and technical literature. The closest and apparently more relevant technical developments in the patent literature can be gleaned by considering the following patents.
U.S. Pat. No. 5,654,232 (Gardner) shows a method for forming a copper interconnect using a silicon nitride or tantalum wetting layer and a copper reflow process to eliminate voids. Gardner does suggest that the dielectric layer can be phosphorous doped silicon glass (PSG), however the dielectric layer is not in contact with the interconnect. Instead a silicon nitride or tantalum wetting layer is used to prevent copper diffusion. Therefore, Gardner does not suggest eliminating the barrier layer.
U.S. Pat. No. 5,739,590 (Sakamoto et al.) teaches a nitrided sulfur glass (NSG) and phosphorous doped silicon glass (PSG) interlayer insulating film (ILD). This invention does not disclose or suggest copper interconnects, nor does it address copper diffusion.
U.S. Pat. No. 5,451,542 (Ashby) teaches a sulfur surface passivation process.
U.S. Pat. No. 6,001,415 (Nogami et al.) and U.S. Pat. No. 5,985,762 (Geffken et al.) show copper interconnect processes with copper diffusion limited by depositing a barrier layer on the sidewall of an insulating layer prior to depositing copper.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for reducing copper diffusion into an inorganic dielectric layer by doping the inorganic dielectric layer with a doping agent.
It is another object of the present invention to provide a method for forming an inorganic dielectric layer, especially silicon oxide, which is doped with phosphorous or sulfur or both, such that it prevents copper diffusion from adjacent copper structures.
It is another object of the present invention to provide a method for reducing fabrication cost and cycle time for copper contacts by eliminating the need for a barrier layer to prevent copper diffusion.
It is yet another object of the present invention to provide a method for reducing RC delay in copper contacts by eliminating the need for a barrier layer for preventing copper diffusion.
To accomplish the above objectives, the present invention provides a method for doping an inorganic dielectric layer with a reducing agent during plasma enhanced chemical vapor deposition to prevent copper diffusion into the inorganic dielectric layer. The resulting doped inorganic dielectric layer can reduce copper diffusion without a barrier layer reducing fabrication cost and cycle time, as well as reducing RC delay.
REFERENCES:
patent: 5451542 (1995-09-01), Ashby
patent: 5654232 (1997-08-01), Gardner
patent: 5739590 (1998-04-01), Sakanoto et al.
patent: 5985762 (1999-11-01), Geffken
patent: 5998303 (1999-12-01), Sato
patent: 6001415 (1999-12-01), Nogami et al.
patent: 6057250 (2000-05-01), Kirchhoff et al.
patent: 1011135-A2 (2000-06-01), None
Aliyu Yakub
Chooi Simon
Gupta Subhash
Ho Paul
Roy Sudipto Ranendra
Chartered Semiconductor Manufacturing Ltd.
Lebentritt Michael
Pike Rosemary L. S.
Saile George O.
Stoffel William J.
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